1.What are aluminum electrolytic capacitors?

Aluminum electrolytic capacitors are capacitors that use aluminum foil as electrodes and aluminum oxide film as the dielectric. Due to the high insulation strength of the oxide film on the aluminum foil surface, aluminum electrolytic capacitors can achieve a combination of high capacitance and high voltage. In electronic circuits, aluminum electrolytic capacitors are usually used in DC circuits for filtering and decoupling, as well as in high-frequency circuits such as computer motherboards.

2.The structure of aluminum electrolytic capacitors

The basic structure of an aluminum electrolytic capacitor consists of two electrodes, an electrolyte, and an insulator. One electrode is made of aluminum foil, and the other is a metal foil with a conductive coating. There is an electrolyte between these two electrodes, usually aluminum sulfate. The insulator is a special material used to prevent direct contact between the electrodes.

3.The general production process of aluminum electrolytic capacitors

Step 1: Etching
To enhance the contact area between the aluminum foil and the electrolyte, the aluminum foil is electrochemically etched to form a rough and porous surface, thereby increasing its surface area.

Step 2: Anodizing
Following the galvanic etching, a chemical process is employed to convert the aluminum foil’s surface into aluminum oxide, which acts as the dielectric of aluminum electrolytic capacitors.

Step 3: Cutting
Before manufacturing a specific type of electrolytic capacitor, the aluminum foil is cut into varying widths based on its size.

Step 4: Riveting and Winding
The aluminum foil is nailed with guide pins, followed by winding positive foil, electrolytic paper, negative foil, and so on.

Step 5: Dipping
Once the electrolytic paper is wound, the electrolyte is poured in, allowing it to be impregnated onto the electrolytic paper.

Step 6: Sealing
The core package of the electrolytic capacitor is enclosed within an aluminum container, and the container’s opening is sealed using a rubber plug or a resin plate to prevent the electrolyte from evaporating.

Step 7: Aging
This process involves subjecting the capacitor to a DC voltage greater than the rated voltage but less than the original anodizing voltage of the aluminum foil, which repairs and screens any faulty products.

4.Characteristics 

• High capacitance: Aluminum electrolytic capacitors have a large capacitance value, typically ranging from several microfarads to several hundred millifarads, to meet the requirements of different circuits.
• High voltage: Aluminum electrolytic capacitors can achieve high operating voltages, typically ranging from several hundred volts to several hundred volts, making them suitable for high-voltage DC circuits.
• Small size: Aluminum electrolytic capacitors have a small volume and weight, making them suitable for use in integrated circuits and microelectronic devices.
• Affordable price: Aluminum electrolytic capacitors are relatively inexpensive and easy to obtain, which is one of the reasons why they are widely used.

5.Applications 

Aluminum electrolytic capacitors have a wide range of applications in electronic circuits, such as filtering circuits, decoupling circuits, oscillation circuits, voltage regulation circuits, and amplification circuits. Here are a few examples of their applications:

1. Power supply filtering circuit: Aluminum electrolytic capacitors can be used as the filtering capacitor in power supply filtering circuits, filtering out ripple signals in the power supply to make the output smoother, reduce output fluctuations, and improve power supply stability.
2. Circuit decoupling: Aluminum electrolytic capacitors can be used as the coupling capacitor in circuit decoupling to separate DC components from AC components, isolate DC and AC circuits, and improve circuit stability and reliability.
3. Audio amplifier circuit: Aluminum electrolytic capacitors can be used as coupling capacitors and limiting capacitors in audio amplifier circuits to amplify and limit sound signals.

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🌞Safety capacitors refer to safety capacitors that will not cause electric shock and will not endanger personal safety after the capacitor fails. Safety capacitors are usually only used for filtering in anti-jamming circuits. They are used in the power supply filter to play the role of power supply filtering, and filter the common mode and differential mode interference respectively. For safety and EMC considerations, it is generally recommended to add a safety capacitor at the power inlet.

2.The difference

🌹The discharge of safety capacitors is different from that of ordinary capacitors. Ordinary capacitors will retain their charge for a long time after the external power supply is disconnected. If you touch them with your hands, they will be charged, but safety capacitors do not have this problem. At the input end of the AC power supply, it is generally necessary to add 3 safety capacitors to suppress EMI conduction interference.

3.Classification

🌸Safety capacitors are divided into x-type and y-type. AC power input is divided into 3 terminals: live wire L/neutral wire N/ground wire G, (L=Line, N=Neutral, G=Ground). Between “L-N”, that is, between “fire wire-neutral wire” is the X capacitor; between “L-G/N-G”, that is, between “fire wire-ground wire or neutral wire-ground wire” is Y capacitance. A capacitor connected between the live wire and the neutral wire is like an “X”, and a capacitor connected between the live wire and the ground wire is like a “Y”. These are not classified according to the material.

X capacitor: Since the location of this capacitor connection is also critical, it also needs to meet relevant safety standards. The X capacitor is also one of the safety capacitors. According to actual needs, the capacitance of the X capacitor is allowed to be larger than that of the Y capacitor, but at this time a safety resistor must be connected in parallel at both ends of the X capacitor to prevent the power cord from being damaged due to the charging and discharging process of the capacitor. Cause the power cord plug to be charged for a long time. The safety standard stipulates that when the power cord of the machine at work is unplugged, within two seconds, the charged voltage (or ground potential) at both ends of the power cord plug must be less than 30% of the original rated working voltage.

🌼As one of the safety capacitors, X capacitors are also required to obtain certification from safety testing agencies. X capacitors are generally marked with safety certification marks and withstand voltage AC250V or AC275V, but their real DC withstand voltage is as high as 2000V or more. When using them, do not use ordinary capacitors with a nominal withstand voltage of AC250V or DC400V as substitutes.

Usually, X capacitors mostly use polyester film capacitors with relatively large ripple currents. This type of capacitor has a large volume, but it allows a large current for instantaneous charge and discharge, and its internal resistance is correspondingly small.

🌻Y capacitor: The connection position of these two Y capacitors is more critical, and must comply with relevant safety standards to prevent leakage of electronic equipment or electrification of the casing, which may endanger personal safety and life. They are all safety capacitors, which require that the capacitance value cannot be too large, and the withstand voltage must be high. In general, for machines working in subtropical regions, the earth leakage current should not exceed 0.7mA; for machines operating in temperate regions, the earth leakage current should not exceed 0.35mA. Therefore, the total capacity of Y capacitors generally cannot exceed 4700PF (472).

The capacitance of the Y capacitor must be limited, so as to achieve the purpose of controlling the magnitude of the leakage current flowing through it and the influence on the EMC performance of the system under the rated frequency and rated voltage. GJB151 stipulates that the capacity of the Y capacitor should not be greater than 0.1uF. In addition to complying with the corresponding grid voltage withstand voltage, the Y capacitor also requires that the capacitor has sufficient safety margin in terms of electrical and mechanical properties to avoid breakdown and short circuit phenomena under extremely harsh environmental conditions. Protecting personal safety is of great significance. In particular: as a safety capacitor, the Y capacitor must be certified by a safety testing agency. Y capacitors are mostly orange or blue in appearance, and are generally marked with safety certification marks (such as UL, CSA, etc.) and withstand voltage AC250V or AC275V. However, its true DC withstand voltage is as high as 5000V or more. It must be emphasized that the Y capacitor should not be replaced by ordinary capacitors with a nominal withstand voltage of AC250V or DC400V.

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When looking at the circuit board of an electronic device, you will find a capacitor electronic component. The main function of the capacitor is to store electricity and release it to the circuits on the circuit board when needed.

In the application of capacitors, two metal plates need to be used to store charges. These metal plates are called electrodes, and an electric field can be maintained between them. They exist as electronic devices for storing power. When the components need to be charged, the capacitor will provide charges as needed.

Capacitors differ from ordinary batteries in terms of energy density, and they also have higher electrical energy storage capabilities compared to standard capacitors. A supercapacitor cannot store as much power as a battery, but it can store more power than a capacitor.

Supercapacitors vs Capacitors

Following are the main differences between supercapacitors and standard capacitors.

1) Material
Standard capacitors are made of a dielectric material, such as polymer film, aluminum oxide, or ceramic, that separates each metal plate (or electrode) from the other. A capacitor does not use all three dielectric materials at the same time, but only one of them.
Supercapacitors use different dielectric materials. Activated carbon is what forms the barrier between the two electrodes of the supercapacitor.

2) Charging time
The best thing about supercapacitors is that they can provide the fastest energy charge and discharge times. Standard capacitors take about 10 seconds to charge and discharge, but supercapacitors can often perform these operations much faster without the risk of damaging circuit components.

3) Energy storage
Supercapacitors store more energy than capacitors and have higher energy density. Typical supercapacitors can store 10 to 100 times more power per unit volume than ordinary capacitors.
This is why supercapacitors are used in so many mobile electronic and mechanical devices, including cars, cell phones, buses, printers, and more.
The use of supercapacitors saves a lot of time spent charging electronic devices, so they rely on supercapacitors to release energy over a longer period of time. In this way, the charging time can be reduced.

4) Cost
Supercapacitors are more expensive than ordinary batteries. The reason can be seen from the above three points, which can be understood as paying for better results. Supercapacitors can store more energy and last longer. There is no need to replace supercapacitors frequently.

5) Power consumption
One advantage of capacitors compared to supercapacitors is that they don’t dissipate as much power, and supercapacitors handle more power, which means you need to provide more energy to the electronics and appliances that use them.

Of course, if you care more about energy saving and saving electricity bills when you use it, then you can choose a device with a capacitor, which is more ideal.
The storage products carried by electronic devices may be capacitors, supercapacitors and batteries, all of which can work together. Supercapacitors offer high energy density and fast charge and discharge times. However, capacitors are necessary to regulate charging and stabilize voltage, especially in batteries and electronics in cars.

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Wonderful Share

🍓The story the teacher told the children in this lesson was “Rainbow Colored Flowers”. When they saw the title, the children were deeply attracted. Through lively language and exaggerated forms of expression, the library teacher vividly presents the cleverly conceived plot and unexpected ending of the story in front of the children. From the story, the children are like rainbow-colored flowers, giving selflessly, sacrificing themselves for others, and not asking for anything in return. Let the child’s mood change from happiness-sadness-surprise with the development of the storyline. Children can experience the joy of helping others, the sadness when the iridescent flower withers, and the surprise when the iridescent flower comes back to life.

The value and charm of the picture book “Rainbow Colored Flowers” lies in that it does not have a single dogma, but it can meet the growth needs of children. There is no reasoning, but it can inspire children to think deeply. There is no noise at all, but it can arouse children’s knowing laughter. We must constantly explore the value of picture books, and show children the splendor of picture books in various forms, so that children can understand in games, grow in understanding, and be happy in growing up.

Curriculum Interaction

🍑During the course, the children listened carefully, thought hard, raised their hands enthusiastically, and actively participated in the classroom interaction. They not only gained gifts, but also gained knowledge.

After the story in the picture book, the teacher took the children to make a handmade —color windmill. When the children make it carefully, the colorful windmills are as gorgeous and warm as the rainbow flowers in today’s story.

🍒The love care class was launched in June 2022. It is mainly to solve the problem that the children of employees are left unattended after school and when their parents are not off work. At present, more than 20 children of employees have participated. The care class is mainly based on basic nursing services. Air conditioners and TVs are installed in the care room, and special caregivers are set up for management. In the nursery class, children can engage in rich activities such as extracurricular reading, painting and graffiti, creative handicrafts, nursery rhyme learning, and popular science videos, which not only cultivate hobbies, develop potential, but also exercise thinking and cultivate sentiment. Waiting for mom and dad to get off work in a safe, fulfilling and meaningful course.

Work hard and continue the love. Thanks to the library for sending children’s books and wonderful courses to the love care class, and thanks to the company for providing care services for the children of all employees, caring and warming everyone. In future activities, the company’s love care class will explore and make progress together with the children, so that more employees’ children can grow up happily in a relaxed and happy atmosphere through both “care” and “teaching”.

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🌱As one of the most abundant elements on earth, carbon plays a vital role in human life and social development. Located in group ⅣA in the second period of the periodic table, the outermost four valence electrons can form single bonds by sp3 hybridization, double bonds by sp2 hybridization and triple bonds by sp hybridization. Various bonding properties give carbon diverse existence forms. 

In terms of simple matter, carbon allotropes include three-dimensional diamond, two-dimensional graphite lamellae and graphene, one-dimensional carbine and carbon nanotubes, zero-dimensional fullerenes and quantum dots, and other forms with completely different structures and properties. 

🌿Carbon materials have various structures and different properties. It can be said that carbon materials almost include the characteristics of all substances on the earth, which makes carbon materials widely used. Among the electrode materials for supercapacitors, the earliest and most mature research technology is carbon materials.

Its research started from the relevant patent published by Beck in 1957, and its development has been more than 60 years. The reason why carbon materials become the first choice for the preparation of supercapacitor electrodes is that they usually have the following characteristics: (1) chemically inert, stable in various acid and alkali solutions, and do not react with electrodes; (2) Large specific surface area, well-developed pore structure and high porosity, which can adsorb a large amount of electrolyte solution;（3）High purity, good conductivity, small leakage current; (4) High thermal stability, stable performance in a wide temperature range; (5)Еasy to process into various shapes of electrodes; (6)The price is low and the source is abundant. 

☘️At present, the most studied electrode materials for supercapacitors mainly include activated carbon, active carbon fiber, carbon aerogel, carbon nanotube and graphene. 

Activated charcoal 

Activated carbon The industrial production and application of activated carbon has a long historyDue to its rich pore structure and huge specific surface area, it has strong adsorption and catalytic properties, and is widely used in environmental protection, chemical industry, energy, medicine and other fields. Activated carbon is the earliest carbon electrode material used in supercapacitors. 

1 The structure of activated carbon-Graphene supercapacitors

🍀Structure of activated carbon Activated carbon is a kind of amorphous carbon, which is composed of graphitized activated carbon microcrystal and non-graphitized amorphous carbon. The graphite microcrystal, which is similar to the two-dimensional structure of graphite, is a planar network structure formed by the hexagonal ring formed by sp2 mixed with hybrid carbon. These graphite microcrystals have a small particle size (about 1 ~ 3nm) and are arranged in an irregular and loose arrangement, which is referred to as “spiral layer structure” or “chaotic layer structure”, as shown in Figure 2-1.

Because the arrangement of graphite microcrystals is irregular and disordered, the pores of different sizes and shapes are formed between microcrystals and amorphous carbonites and between microcrystals, including open pore shape, semi-obturator pore shape and mesenchymal cage shape. According to the size of pores, it can be divided into: large pores (pore diameter greater than 50nm) are called supply or transport pores, accounting for a small proportion, weak adsorption performance, mainly play a role in providing channels for the entry of adsorbent molecules, which plays an important role in the adsorption speed; Mesopore (pore diameter between 2 and 50nm) is also called mesopore. 

🎍On the one hand, mesopore has the same function as macropore, which can act as a channel for adsorbent molecules to enter the micropore. On the other hand, mesopore can adsorb macromolecular substances that cannot enter the micropore. Micropores (pore diameter is less than 2nm), also known as adsorption pores, activated carbon more than 90% of the specific surface area and pore capacity are from the contribution of micropores, micropores for gas and liquid small molecules have a strong adsorption effect, to a large extent determines the adsorption performance of the entire activated carbon. The three kinds of pores are staggered and crossed to form a tree structure, as shown in Figure 2-2.

In addition, the pore size structure of activated carbon has different relationship with the molecular scale of adsorbent, and the adsorption state is also different. When the pore size of activated carbon is much smaller than the molecular diameter of adsorbent,Molecules can not enter the pore, activated carbon does not adsorption; When the pore size of activated carbon and adsorbent molecular diameter is similar, activated carbon on the molecular adsorption capture ability is the strongest, even if the concentration of low molecules can also be adsorbed; When the pore size of activated carbon is larger than the molecular diameter of adsorbent, the molecular capillary condensation occurs in the pore, which can increase the adsorption capacity. When the pore size of activated carbon is much larger than the adsorbent diameter, the molecules are easy to be absorbed, but also easy to occur desorption, so that the final adsorption amount is small. Therefore, only when the pore size of activated carbon and adsorbent molecules match each other can the adsorption process be carried out effectively.

2 Performance characteristics of activated carbon

🎋Activated carbon, as the earliest and most widely used electrode material for supercapacitors, has the following performance advantages. （1）Large specific surface area, the theoretical specific surface area of activated carbon is 500 ~ 3000m2·g-1, which is made into a supercapacitor electrode. The theoretical specific capacitance of a single electrode can be as high as 500F·g-1, but the actual specific capacitance is far less than this A value. （2）The pore structure is developed, and the number of pores is about 1020 ·g-1, which can absorb a large number of electrolyte solution molecules. (3) High chemical stability, no chemical reactions, not easy to be acid, alkali and other solutions corrosion. (4) High purity, good electrical conductivity, good thermal stability. （5）Easy to process, good compatibility with other materials. （6）The price is low and the source is abundant.

3 Preparation of activated carbon

3.1 Prepare raw materials

🍃Raw materials for the preparation of activated carbon There are abundant sources of raw materials for the preparation of activated carbon. Generally, as long as the materials rich in carbon can be used as raw materials for the preparation of activated carbon. According to the source of raw materials can be divided into plant raw materials and mineral raw materials two categories. Among them, plants have a wide range of raw materials, in addition to traditional wood,Coconut shell, walnut shell, apricot kernel, olive kernel, rice husk, etc., as well as agricultural and forestry by-products and waste living carbon, such as wood chips, bark, bamboo, cotton stalk, peanut shell, waste plastic, urban garbage, etc. At present, it is generally believed that the fruit shell is the best raw material for the preparation of activated carbon, which has high strength and very fine micropores, but the fruit shell resources are limited and not easy to concentrate storage. Mineral raw materials include coal measures raw materials and petroleum raw materials. Due to the rich, cheap and easy availability of coal resources, the coal measures raw material is the main raw material for preparing activated carbon in a long period of time. Petroleum raw materials mainly refer to carbon-containing products and wastes in the process of petroleum refining, such as asphalt, oil residue, petroleum coke, etc. Petroleum coke has the advantages of high carbon content, low ash content and good electrical conductivity, which is suitable for the preparation of activated carbon raw materials.

3.2 Preparation Methods

The preparation of activated carbon is generally divided into two steps: carbonization and activation. Carbonization refers to the heating of raw materials to a certain extent under conditions of air isolation or protection from inert gasesTemperature, so that the volatile non-carbon components in the raw material decomposition discharge. The whole process can be divided into four stages according to the temperature change: 

🍂The first stage is the drying process, the temperature is 120 ~ 150℃, mainly to remove the water evaporation in the raw material, the temperature is not high, the chemical composition of the raw material does not change; The second stage is the pre-carbonization process, when the temperature rises to 150 ~ 275℃, the thermal decomposition of raw materials is obvious, the chemical composition of materials begins to change, the internal structure recombines, and some unstable components begin to decompose. The third stage is the carbonization process, which is the key link of the carbonization of activated carbon. The reaction temperature reaches about 400℃, and the rapid decomposition of raw materials produces a large number of gases and liquids. The fourth stage is calcination process, the system temperature reaches 500℃, the raw material is further calcined, a small amount of residual volatile substances are discharged, and the carbon material with increased fixed carbon content is obtained. The essence of carbonization is the process of thermal decomposition and thermal condensation of organic matter in raw materials, among which the carbonization temperature, carbonization time, heating rate and other parameters are important factors affecting the quality of carbonization products, and will also have a certain impact on the subsequent activation process.

Activation process is the most critical step in the preparation of activated carbon, which can effectively regulate the specific surface area and pore structure of activated carbon. The activation process is a complex chemical reaction between activator and carbon material. This process can be divided into three main stages: the first stage is at high temperature, the initial pores blocked by disordered carbon atoms and heteroatoms under the action of activator are opened and further expanded, which is called transverse pore expansion; In the second stage, the unsaturated carbon atoms at the edge of the newly opened pores further react with the activator, making the pores develop continuously to the depth, and achieve the merger or connection between pores. In the third stage, new unsaturated carbon atoms or active spots are exposed to the microcrystalline surface, and the uneven combustion of the microcrystalline surface leads to the formation of a large number of new pores. Changing the temperature, time, gaseous environment and other conditions of activation reaction can regulate the porosity, pore size distribution and inner surface properties of activated carbon to a certain extent. 

🍁At present, the commonly used activation methods include physical activation method, chemical activation method, physical-chemical combined activation method and other activation methods.

(1) Physical activation method physical activation, also known asFor gas activation or thermal activation, carbon materials and water vapor, carbon dioxide, oxygen, air and other gases with oxidation characteristics are heated at a high temperature of 600 ~ 1200℃ for activation. Its essence is the oxidation reaction between the unsaturated carbon atoms in the raw material located at the corner of the microcrystal or the defect of the base surface and the oxidizing gas, which eliminates the residual volatile pyrolysis products in the carbon material and greatly increases the pore volume and the specific surface area of the obtained activated carbon material. 

🍄The main advantages of the physical activation method are simple production process, less pollution, and the product can be directly used without cleaning. However, the activation temperature of the method is higher, the activation time is longer, the energy consumption is high, and the activated carbon pore is not developed enough, and the specific surface area is low. 

(2) Chemical activation method Chemical activation method is a method of mixing thick solutions containing carbon raw materials and chemical reagents, stirring them evenly, heating up, pyrolysis, cooling, and continuous washing with detergent to remove activators. FIG. 2-3 shows its technological process. Its essence is through the dehydration, expansion and skeleton of chemical reagents on raw materials, so that the two are gas activation or thermal activation. It is the method of heating carbon materials and water vapor, carbon dioxide, oxygen, air and other gases with oxidation characteristics at the high temperature of 600 ~ 1200℃ for activation. Its essence is the oxidation reaction between the unsaturated carbon atoms in the raw material located at the corner of the microcrystal or the defect of the base surface and the oxidizing gas, which eliminates the residual volatile pyrolysis products in the carbon material and greatly increases the pore volume and the specific surface area of the obtained activated carbon material. The main advantages of the physical activation method are simple production process, less pollution, and the product can be directly used without cleaning. However, the activation temperature of the method is higher, the activation time is longer, the energy consumption is high, and the activated carbon pore is not developed enough, and the specific surface area is low. 

💐(3) Chemical activation method Chemical activation method is a method of mixing thick solutions containing carbon raw materials and chemical reagents, stirring them evenly, heating up, pyrolysis, cooling, and continuous washing with detergent to remove activators. FIG. 2-3 shows its technological process. Its essence is through the chemical reagents to the raw material dehydration, moistening swelling and skeleton action, so that bothA series of polycondensation and cross-linking reactions take place, thereby releasing part of the carbon atoms in the raw material, and at the same time releasing hydrogen and oxygen in the form of water vapor, forming a large number of pores.

In the chemical activation method, common activators are zinc chloride (ZnCl2), phosphoric acid (H3PO4), potassium hydroxide (KOH), sodium hydroxide (NaOH), calcium chloride (CaCl2) and so on. The action process of these activators on carbon raw materials is different, but the action mechanism is similar. Through the addition of activators, part of carbon, hydrogen and oxygen contained in the raw materials are decomposed and separated in the form of carbon dioxide, carbon monoxide and water vapor, and the carbonization temperature is significantly reduced at the same time.

🌷（1）ZnCl2 activation method ZnCl2 activation method is one of the earliest chemical activation methods for the preparation of activated carbon, its strong dehydration effect makes the activation temperature significantly reduced, generally in 500 ~ 700℃. The activation mechanism is that ZnCl2, as a Lewis acid, interacts with oxygen-containing functional groups, releasing hydrogen and oxygen in the carbon raw material in the form of water vapor, leading to the aromatization of carbon chains to form pore structures, and changing the thermal decomposition process of raw materials to inhibit the generation of tar. Due to the reaction temperature lower than 700℃, ZnCl2 in the form of liquid evenly distributed in the activated carbon, when the water to remove ZnCl2 washing, the formation of developed micro pores, but also caused the removal of ZnCl2 consumption, high activation cost, and pollution to the environment. 

(2) KOH activation method KOH is one of the most representative alkali activators, AMOCO research found that adding KOH to coal or petroleum coke, activation can be obtained after the high specific surface area of 2500m2·g-1 activated carbon. The activated carbon product obtained by this methodThe distribution of micropores is concentrated, the pore structure is uniform and developed, and the specific surface area is large, which has attracted a lot of attention from scholars at home and abroad in recent years. The specific process is to add alkali to the raw material in accordance with a certain proportion of mixing, after grinding and mixing evenly, in inert gas or closed system heating to 700 ~ 800℃ carbonization, activation, that is, to get a large number of cage-like microporous structure of activated carbon. According to the temperature of the system, the whole activation process is divided into four stages [1] : in the first stage, low temperature dehydration (<300℃), the attached water on the surface of the raw material and the combined water generated by the reaction overflow in the form of steam; The second stage, pre-activation (300 ~ 500℃), the production of water vapor and carbon dioxide, carbon monoxide and other gases and volatilization; In the third stage, the molecules are activated at moderate temperature (500 ~ 600℃), crosslinking or polycondensation reaction occurs, and some non-carbon elements are volatilized. In the fourth stage, KOH is almost completely transformed into K2CO3 and K2O by high temperature activation (>600℃). These two compounds are further reacted with carbon materials to generate highly active potassium. When the temperature is higher than 762℃, potassium diffuses in gas state to form vertical The final activated carbon product has a large number of micropores and high specific surface area. The main chemical reactions that occur during the whole process are as follows:

🌹In the process of KOH activation, there are many factors that affect the performance of products, and the main factors are as follows. 

a. Agent to material ratio: that is, the selection of activator KOH and carbon containing raw material between the mass ratio, it on activated carbon products Performance has a significant impact. When the ratio of KOH to carbon material is low, the activation reaction is not sufficient, and the products formed have fewer pores and lower specific surface area.When the alkali-carbon ratio is too large, the excess KOH will cause the excessive reaction of activated carbon, so that some of the formed better pores collapse into series of large pores, so that the product’s specific surface area and pore volume are reduced. Therefore, according to the material and particle size of carbon raw materials and specific process to choose the appropriate ratio of agent to material.

🥀b. Particle size of raw material: particle size of raw material directly affects the full degree of contact between raw material and activator. Under the same conditions, the smaller the particle size of the raw material, the more developed the pore structure of the product, but too small the particle size will bring difficulties to sample preparation and filtration, and affect the yield. 

c. Addition method of KOH: The addition method of KOH mainly includes simple incorporation method and impregnation method. The simple mixing method is to mix KOH powder and carbon raw material, which is simple to operate but has low yield, small product specific surface area and pore capacity. The impregnation method starts with KOH After a certain concentration of solution is prepared, the carbon raw material is added to the solution, and KOH is adsorbed to the surface and internal pores of the raw material through impregnation. This addition method can make the activator contact with the carbon material more fully, with a low loss rate and a larger specific surface area of the product. 

🌺d. Activation temperature: Theoretically, the higher the temperature, the higher the molecular activation energy and the higher the reaction degree, the larger the specific surface area of the product, and the phenomenon of pore expansion will also occur, but the yield will also be reduced.

e. activation time: some conditions, as the activation time of rights, product yield decreased, and the specific surface area, pore volume increased, but when the activation time after reaching a certain value, due to the reaction of generated microporous was further collapse into the holes or big hole, no longer increases the specific surface area and pore volume, it has reduced. In addition, the operation of KOH active agent washing and product drying at the end of the process also has a great influence on the performance of activated carbon. The specific surface area of activated carbon prepared by alkaline activation method is relatively high Large, short activation time, more mature process; However, alkali itself is corrosive to equipment, difficult to recover, in addition to the high activation temperature, energy consumption and other shortcomings, so there are still many problems in large-scale industrial production. 

🌸(3) H3PO4 activation method H3PO4 activation method is one of the most commonly used methods for the preparation of activated carbon because of its light pollution to the environment and low production cost. Its activation mechanism is similar to that of ZnCl2. H3PO4 plays the following roles in the activation process.

a. Dehydration: in the absence of H3PO4, most of the hydrogen and oxygen volatilized by organic matter, while in the form of water vapor removal under the action of H3PO4, more carbon can be retained and the yield increased.

🌼b. Swelling effect: at low temperature, H3PO4 penetrates into the raw material, accelerates the swelling and dissolution of cellulose and lignin in the raw material through ionization, and promotes subsequent hydrolysis and oxidation reactions.

🌻c. Oxidation: H3PO4 has certain oxidation ability. Above 200℃, H3PO4 forms pyrophosphate network structure through cross-linking polycondensation reaction. Pyrophosphate has strong corrosion and oxidation properties, and further oxidizes carbon materials to form more micropores and mesoporous materials.

🌞d. Aromatic condensation: When the temperature continues to rise, polycondensation carbon structure is formed by polycondensation, cyclization and cross-linking of phospholipid bond with organic matter or other polymers, which can be activated and transformed into random layer microcrystalline structure of carbon at appropriate temperature. 

In short, in the whole activation process, H3PO4 can promote the pyrolysis reaction process, reduce the activation temperature, prevent the particle shrinkage under high temperature conditions, reduce the formation of tar. After washing and removing phosphate, activated carbon products with developed pore structure can be obtained. The products prepared by phosphoric acid activation method have wide pore size distribution and well-developed mesoporous pores. Phosphoric acid itself has low corrosion and less environmental pollution. The activated carbon produced is uniform and stable.Good settling performance, wide application areas. 

🌝(3) physical-chemical combined activation method Physical-chemical combined activation method is to combine the advantages of physical activation and chemical activation, the first use of simple physical activation and chemical activation of the secondary activation method. However, this method still cannot overcome some adverse factors, and additional steps are added. At present, the composite activation technology of chemical impregnation and physical activation is mostly adopted. The activated carbon materials with excellent adsorption performance and reasonable pore size distribution can be prepared by controlling factors such as the quality ratio of the activator raw material, impregnation time, activation temperature and activation time. Hu et al. impregnated with ZnCl2 and activated coconut husk with CO2 at high temperature to prepare a series of mesoporous activated carbon with controllable pore structure. Zhang Wenhui et al. took coal-based carbon source as raw material, impregnated the sample with KOH and activated it with water vapor, and obtained the product with a specific surface area greater than 1500m2·g-1 and good adsorption performance in a relatively short time.

4 Activated carbon modification

🌛With the increasingly high performance requirements for carbon-based materials, simple carbonization, activation process has been difficult to meet, therefore, the late regulation and modification of activated carbon technology has been paid more and more attention. The modification of activated carbon includes two aspects: the first is the surface structure modification, which refers to the physical or chemical method to increase the specific surface area of activated carbon material and adjust the pore structure and distribution of activated carbon in the preparation process, so that the pore structure of activated carbon is changed, so as to change its adsorption and energy storage performance. Second, the surface chemical properties of activated carbon modification, is through a certain method to change the type and number of functional groups on the surface, the surface of the heteroatom and its surrounding atmosphere structure, so that the active site increase, so as to control its binding ability with the adsorbed. At present, the research on the late preparation technology of activated carbon modification and modification has attracted much attention. According to the different principles and characteristics of the technical treatment basis, the modification technology can be divided into the following types.

4.1 Heat treatment method

🌟Heat treatment refers to the process of heating activated carbon at high temperature under certain conditions. Through heat treatment, the initial pore size, pore volume and functional groups on the surface of the original carbon material can be changed, so as to obtain the activated carbon material with developed pores, low oxygen and oxidation resistance. Kim heat-treated activated carbon in high temperature and nitrogen environment to obtain activated carbon containing pyrrole nitrogen on the surface, which greatly improved the hydrophilicity and wettability of activated carbon. In addition to the ordinary heating method, the method of microwave heating modified activated carbon has many advantages, and has been paid more and more attention by researchers. Microwave heating mainly causes the shrinkage of carbon skeleton through rapid and efficient thermal action, which leads to the change of pore size and pore volume. In addition, the use of microwave heat treatment of activated carbon under different atmospheres will affect the properties of its surface groups, such as oxidizing atmosphere is conducive to the formation of acidic groups, reducing atmosphere is conducive to the formation of basic groups.

4.2 Surface oxidation method

✨Under appropriate conditions, the surface of activated carbon is oxidized by using oxidants to remove some impurities on the surface and improve the content of oxygen-containing functional groups (such as carboxyl group, phenolic hydroxyl group, ester group, etc.) on the surface, which can improve the infiltration of carbon surface and also play a certain role in pore reaming. Oxidizing modification of the commonly used oxidants are nitric acid, hydrogen peroxide, sulfuric acid, ozone, ammonium persulfate, etc., the use of oxidants are different, the number and type of oxygen-containing functional groups of the products are different. In addition, the pore structure, specific surface area, volume and pore size of the modified activated carbon will also change. Nitric acid is the most commonly used strong oxidizing agent, and related studies have been widely reported. Dubi et al. used coconut shell activated carbon and apricot shell activated carbon as raw materials and used concentrated nitric acid surface modification to make electrodes for supercapacitors, and the discharge specific capacitance increased significantly. Ran Longguo et al. treated the activated carbon with nitric acid at different concentrations, and the specific surface area of the activated carbon after 10% nitric acid treatment was as high as that of the activated carbon

4.3 Surface reduction method

⚡️Surface reduction modification refers to the reduction of functional groups on the surface of activated carbon with appropriate reducing agent at appropriate temperature, so as to increase the content of basic functional groups on the surface of activated carbon and enhance its non-polar surface, so as to improve its adsorption capacity for non-polar substances. The commonly used reducing agents are hydrogen, nitrogen, sodium hydroxide, potassium hydroxide and ammonia. Hydrogen or ammonia is the most commonly used method to prepare alkaline activated carbon. At 400-900 ℃, amides and aromatic amines can be generated on the surface of activated carbon after ammonia is added, and pyridine substances can be generated at higher temperatures. These nitrogenous functional groups will enhance the alkalinity of activated carbon surface. In addition, higher content of nitrogenous functional groups can be obtained by impregnating activated carbon in ammonia. Huang et al. found that the nitrogen content in the samples increased significantly after the modification of activated carbon by ammonia infiltration.

4.4 Load atom method

☄️The supported atom modification method is to impregnate the activated carbon in a certain solution, make use of the huge specific surface area and pore volume of activated carbon, and introduce metal ions or other heteroatoms into the activated carbon pore by liquid deposition method, so as to increase the adsorption effect of activated carbon on the adsorbent. The metal ions commonly used for loading are copper ions, iron ions, aluminum ions and silver ions, etc. The activated carbon after loading shows good potential in adsorption of fluoride ions, cyanide and heavy metals and other pollutants

4.5 Low-temperature plasma method

🌈Plasma modification is a process of using non-cohesive plasma gas to modify the material surface. A plasma is an aggregate state of matter with a sufficient number of positive and negative charged particles of approximately equal charge. The low temperature plasma used for activated carbon modification is mainly produced by corona discharge, glow discharge and microwave discharge. The most commonly used is oxygen plasma, which has strong oxidation, when the plasma hits the surface of carbon materials, it can oxidize the crystal Angle, crystal edge and other defects or double bond structure into oxygen-containing functional groups. Modified by low-pressure oxygen and nitrogen plasma, activated carbon with a surface rich in nitro, amino and acyl amino groups can be obtained. Low temperature plasma modification technology is easy to operate, mild reaction conditions, low price, good environmental safety, and the treatment effect is only limited to the surface without affecting the properties of the material. In addition to the above modification methods, activated carbon modification methods also include surface acid-base modification method, ozone oxidation method, microwave radiation method, organic matter grafting method and so on. These methods have their own characteristics, and can be used alone or combined to modify activated carbon, so as to achieve better modification effect. In the process of use, suitable modification methods should be purposefully selected according to the properties of adsorbent.

5 Application of activated carbon in supercapacitors-Graphene supercapacitor

☀️Activated carbon is the earliest carbon electrode material used in supercapacitors. Due to its abundant raw materials, low price and high specific surface area, it is still the first choice for commercial supercapacitors. Since Beck proposed to use activated carbon as electrode of double-layer capacitor in 1954, the application of activated carbon in supercapacitor has attracted much attention. According to the different source of raw carbon, the application of activated carbon in supercapacitors is briefly introduced.

5.1 Fruit shell-based activated carbon

🍏Hou min, etc by the coconut shell charcoal material as raw material, KOH as activator, discussed the basic carbon ratio, activation temperature and activation time on the structure and properties of the activated carbon (table 2- 1), in carbon ratio, alkali activation temperature of 800 ℃, activation time, can prepare the specific surface area, total pore volume and pore diameter are mainly distributed in, porosity, average pore diameter of high quality activated carbon materials. The activated carbon is used as electrode material, the specific capacitance in the electrolyte can be reached, has excellent electrochemical performance; Yang Jing et al. with walnut shell as raw material, using the secondary activation method to prepare activated carbon, charge/discharge, mass ratio capacitance as high as, capacitor energy density as high. Chen Xiaomei et al. prepared activated carbon electrode material by chemical activation method with walnut shell as precursor and KOH as electrolyte The test results show that the prepared activated carbon electrode material has ideal electrochemical capacitance behavior, the specific capacitance is as high as 0.25mA, the leakage current and the equivalent series resistance are only 0.39Ω, respectively. After 5000 cycles of charging/discharging, the capacitance still remains above 88%.

5.2 Rice husk-based activated carbon

🍎Song Xiaolan et al. used rice husk as raw material and NaOH as activator to obtain activated carbon with specific surface area at 800℃. In KOH electrolyte, the specific capacitance of capacitor was up to, and after 5000 cycles, the capacitance retention rate was still there. Using rice husk as raw material and NaOH as activator, He et al. obtained activated carbon with specific surface area as microwave heating, and its specific capacitance was still up to after the second cycle. After carbonizing rice husk under nitrogen atmosphere, impregnating with HF and activating with KOH, the activated carbon with graded pore structure containing large mesopore and rich micropore was finally obtained, with a high specific surface area and energy density

5.3 Bamboo charcoal based activated carbon

🍐Bamboo as a kind of renewable biomass raw material has the characteristics of fast growth, rapid renewal and strong regeneration ability, and bamboo resources are rich and widely distributed in our country, which provide convenience for us on raw materials. Bamboo charcoal is a solid product obtained by carbonization of bamboo at high temperature and without oxygen. It has the characteristics of high mechanical strength, developed pore structure, large specific surface area and good electrical conductivity. Lee et al. found that bamboo activated carbon has good micropore structure and high mesoporous rate, and can significantly improve the permeability of electrolyte when used as a fast ion channel in the electrode of supercapacitor. Bai Xiang et al. with bamboo as raw material, the carbonization of bamboo charcoal first physical activation, and then in the activation, the specific surface area of bamboo charcoal based activated carbon, pore size distribution between, specific capacity up to, and showed a good high current charge/discharge performance. Yang Shengjie et al. prepared activated carbon at high temperature under the protection of inert atmosphere with Moso bamboo as raw material, sodium hydroxide as activator, and obtained the optimal process conditions: activation time 2h, activation temperature, alkalo-carbon ratio (mass ratio), the first discharge ratio capacitance of the prepared material, the second cycle ratio capacitance retention rate, and the leakage current of the prepared material

5.4 Coal-based activated carbon

🍊Coal based activated carbon yield accounts for more than 70% of total activated carbon production in China, is the main variety of activated carbon production in China. Coal-based activated carbon has the characteristics of low production cost, wide source, simple preparation method, good electrical conductivity, high specific surface area, strong corrosion resistance, controllable pore structure and stable electrochemical performance. Therefore, coal-based activated carbon as electrode material has broad application prospects. Zhang Chuanxiang et al. Taixi anthracite as raw material, as activator, under the condition of carboniferous ratio, activation of activated carbon for specific surface area, mesoporous rate is, in the electrolyte capacitance is as high as, and under the high current density charge/discharge ratio capacitance retention rate is high, leakage current is only. Xing Baolin et al Henan Yongcheng anthracite as raw material, coal based activated carbon with high specific surface area, the capacitance is as high as, after the cycle, the ratio of capacitance to maintain the rate. Using bituminous coal as raw material, Zhang et al. prepared a kind of oxygen-rich activated carbon with medium specific surface area by rapid activation method. The oxygen-rich activated carbon as electrode material has higher energy density and power density, and its specific capacitance is as high as and at and current densities, respectively.

5.5 Petroleum-based activated carbon

🍋Petroleum coke is a by-product of petrochemical refining industry, which has abundant resources, wide distribution, low price, high carbon content, high yield of activated carbon and large specific surface area. In addition, the ash and volatile matter of petroleum coke are low, and the activated carbon produced has low impurity content and excellent performance. Song Yan et al. investigated the effects of different influencing factors on the properties of activated carbon products through orthogonal experiments, and the order of the effects was as follows: microstructure of raw coke > activation temperature > alkali-carbon ratio > particle size of raw material > activation time (” > “means” better “). Under the optimal combination conditions, Panjin petroleum coke was used as raw material and activated by KOH to prepare activated carbon with specific surface area. At the same time, it was found that the coke with small grain and fine Mosaic optical structure in the raw material had the highest reactivity with the activator, and the prepared activated carbon had the largest specific surface area. Tan Minghui et al. obtained porous carbon with petroleum coke as raw material and KOH activation, impregnated it in ferric nitrate solution after carbonization and high temperature activation of carbon dioxide, and prepared activated carbon with specific surface area and total pore volume. After the second activation by metal salt impregnation, the mesoporous ratio of the porous carbon increases from to, which significantly increases the charging/discharging rate of the electrode. By introducing the active gas hydrogen, Xiao Ronglin et al. obtained activated carbon with high specific surface area under the condition of reducing the amount of alkali, and showed better performance than the activated carbon prepared without introducing hydrogen. The added hydrogen can react with the functional groups on the surface of activated carbon, provide more active points, promote the development of the pore structure of activated carbon, and adjust the distribution of pore structure.

5.6 Bitum-based activated carbon

🍌Asphalt is a complex mixture of dark brown and high viscosity composed of different molecular weight hydrocarbon compounds and their nonmetallic derivatives, which can be mainly divided into coal tar asphalt, petroleum asphalt and natural asphalt. Among them, coal tar pitch is a by-product of coking, which has the advantages of not being disturbed by season, low price and high carbonization yield, and has been used by a large number of researchers as electrode materials for supercapacitors. Using magnesium oxide as template and coal tar pitch as carbon source, the mesoporous activated carbon material was prepared by one-step heating. The material has high specific capacitance, and the specific capacitance under and current density is and respectively. Using carbonized meso-phase asphalt as precursor and activator, Jing Ulrich prepared activated carbon electrode materials for supercapacitors. The effects of activation temperature, alkali-carbon ratio and process conditions on the pore structure and electrochemical behavior of activated carbon were investigated. The results show that the maximum specific capacitance of the activated carbon electrode prepared under the conditions of activation temperature and alkali-carbon ratio can be reached at time, the changes of the pore structure and specific capacitance of the activated carbon depend on the specific treatment process, and the mesoporous content has an important influence on the specific capacitance of the activated carbon electrode. He et al.] took coal tar pitch as raw material, only a small amount of KOH activator was used, and heated under the assistance of microwave to obtain activated carbon with a specific surface area. The performance of supercapacitor electrode material in different electrolytes is studied. It is found that the ratio of capacitor in the electrolyte is higher than that in the capacitor, and the energy density in the solution is higher.

5.7 Phenolic resin-based activated carbon

🍉Phenolic resin is obtained by polycondensation of phenolic compounds and aldehydes, among which the resin obtained by polycondensation of phenol and formaldehyde is the most important. As the earliest synthetic polymer, phenolic resin has attracted more and more attention because of its mature production process, low price, high carbonization yield, easy activation of pores and large specific surface area. Teng et al. used phenolic resin as raw material and as activator to prepare activated carbon with specific surface area and medium specific capacity. Geng Xin et al. prepared activated carbon with high specific surface area for supercapacitors by activation method using water-soluble phenolic resin as raw material. The results show that the activated carbon prepared at 650℃ has the largest specific surface area and the smallest micropore ratio. However, the micropores of activated carbon prepared at 700℃ and 750℃ are interconnected, and the conductivity and ion migration resistance are better than those of the former. Using silica sol as template and phenolic resin as carbon source, Wang Renqing et al. prepared activated carbon with specific surface area by template method. Under the current density, the specific capacitance could be reached. In addition, the pore size and pore size distribution of the product carbon can be controlled by adding materials such as polyvinyl alcohol or polyvinyl butyral, which are easy to crack and have low carbon residue, into the phenolic resin.

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Catch the first little happiness in early winter

At the beginning of the activity, the flower arrangement teacher taught the daily maintenance knowledge of various flowers on the spot, which greatly benefited the employees who love flowers present. Secondly, she demonstrates the basic skills of making flower arrangements, modeling and aesthetic appreciation of flower arrangement art and other basic knowledge.

Early winter is the dusk bitten by the universe

The scene has already been arranged, exquisite and elegant, warm and romantic, with all the production tools and delicate flower materials ready, put aside the tedious life and troubles of work, and enjoy the joy of life brought by flowers.

You have a date with autumn and winter afternoon

Autumn and winter are not necessarily desolate and lonely, but they can also be bright and warm, colorful and full-bodied. Select special flowers for autumn and winter, so that everyone can feel the colorful colors in the flowers.

Hi! Here is a beautiful autumn and winter, please sign for it

Enjoy flower art, create a better life

The ladies and sisters are really super beautiful in arranging flowers carefully. After the steps of selection-trimming-insertion-embellishment, bunches of flowers are in their hands, completing the process from conception to presentation, integrating exclusive mind and fragrance In one flower and one leaf, making a beautiful flower basket with your own hands is the most unique gift and reward for yourself.

This event enriched the employees’ spiritual and amateur cultural life, allowing employees to relax and release work pressure after busy work, and enjoy the fun brought by flower arrangement. In the next step, Dongguan Xuansn Electronics will continue to organize various types of learning and exchange activities, continuously enhance the cohesion of employees, and continue to stimulate employees’ passion and enthusiasm for work.

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Teacher Liu Kaiping：

🌷This event invited Liu Kaiping, Director of Dongguan Hopu Psychological Counseling Service Center, National Secondary Psychological Counselor, Specially Appointed Psychological Counselor and Psychological Lecturer of Dongguan Federation of Trade Unions, to give mental health lectures to employees. Explained and analyzed, and explained to the staff present how to deal with stress and how to relieve it, and how to correctly understand the stress in life. During the course, Mr. Liu interacted with the employees. The whole lecture process was very relaxed and interesting. Through the interaction, the state of the employees at home and at work was presented, and the employees were guided on how to actively resolve conflicts and pressures, which subtly improved the mental health knowledge of the emp.

Mental Health Lectures

🌹Teacher Liu took “Dancing with Stress” as the topic, from understanding stress, understanding the relationship between stress and physical health, analyzing the emotions caused by stress, how to use the way of thinking to optimize hair to deal with stress, and learning how to use external resources to dance with stress, etc. Five aspects are explained. The examples explained by the teacher are vivid and vivid, which play a great positive role in helping employees correctly understand their own psychological problems and relieve their psychological pressure.

🌺Thanks to the Dongguan Xiegang Federation of Trade Unions for delivering lessons to our company. This training has benefited the employees a lot. They are fully aware that when dealing with psychological problems, they must pay full attention and provide timely counseling, without paying too much attention and treating them like a scourge. Many employees have said that in their future life and work, when they encounter confusion and pressure that they cannot solve, they will actively decompress themselves, and if necessary, they will seek guidance and consultation from the outside world or even professional teachers in a timely manner to help them better face the problems. Life. In the next step, Xuansn Electronics will continue to provide employees with training lectures on safety, health, and psychological counseling, so as to effectively protect the physical and mental health of employees and help the high-quality development of the company. In particular, let more people understand the importance of psychological counseling-assisted mediation in advance, so that employees can undergo a complete psychological transformation, and create a positive and healthy working environment in an all-round way.

🌸Mental health refers to all aspects of the mind and the process of activities in a good or normal state. The ideal state of mental health is to maintain a state of intact character, normal intelligence, correct cognition, appropriate emotion, reasonable will, positive attitude, appropriate behavior, and good adaptation.

🌼Mental health is influenced by both heredity and environment, especially the parenting style of the original family in childhood, which has a great impact on the development of mental health. Mental health highlights the ability to maintain good communication or cooperation with other people in social, production, and life, and to be able to handle various situations that occur in life well.

🌻The individual can adapt to the developing environment, has perfect personality characteristics; and its cognition, emotional response, will and behavior are in a positive state, and can maintain normal regulation ability. In the practice of life, being able to correctly understand oneself, consciously control oneself, and correctly treat external influences, so as to keep the mind balanced and coordinated, already possesses the basic characteristics of mental health.

🌞The basic meaning of mental health is that all aspects and activities of the mind are in a good or normal state. The ideal state of mental health is to maintain a state of perfect character, normal intelligence, correct cognition, appropriate emotion, reasonable will, positive attitude, appropriate behavior, and good adaptation. Corresponding to mental health are mental sub-health and mental illness. Mental health has different meanings from different perspectives, and the measurement standards are also different.

🌛Mental health is an inseparable and important aspect of modern people’s health, so what is human mental health? There are standards for people’s physical health, and there are standards for people’s mental health. However, the standard of human mental health is not as specific and objective as the standard of human physical health. Understanding and mastering the definition of mental health is of great significance for enhancing and maintaining people’s health. When people have mastered the standard for measuring people’s mental health, they can use this as a basis to compare themselves and carry out self-diagnosis of mental health. If you find that one or several aspects of your mental state have a certain distance from the mental health standard, you can strengthen mental exercise in a targeted manner in order to achieve the level of mental health. If you find that your mental state seriously deviates from the mental health standard, you should seek medical advice in time for early diagnosis and early treatment.

✨Mental health refers to a sustained and positively developing state of mind in which subjects are able to make good adjustments and develop their full physical and mental potential. Mental health education is an important part of “new health education”. It is aimed at cultivating social citizens with physical and mental health. Through the use of health management methods, the improvement of the campus environment and functional environment is the main focus, and the improvement of the human environment is matched. , with teachers and students as the two main bodies, to provide scientific, healthy and professional guidance. “New Health Education” has built a special health guidance room (psychological counseling room) in the school, equipped with professional psychological counselors stationed in the school for a long time, and guides students’ healthy psychological development by offering psychological courses and carrying out extracurricular activities. At the same time, a “family chat room” is set up to open a channel for the connection of family and pave a smooth way for the healthy growth of students.

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🌟The supercapacitor with metal oxide as electrode material belongs to Faraday pseudocapacitor, also known as Faraday quasi capacitor. The electrode materials mainly include precious metal oxides and transition metal oxides. As the energy storage process of pseudo capacitor is realized through redox reaction, the surface and interior of electrode materials can participate in Faraday reaction, while the electric double-layer capacitor is connected to energy storage is realized by electrostatic adsorption on the surface of electrode material, so the specific capacitance of pseudo capacitor is much higher than that of double layer capacitor, reaching 10~100 times, which makes it possible to realize the miniaturization of supercapacitor. 

⚡️The results show that the metal oxides suitable for supercapacitor electrodes generally need to have: ① conductive oxides; ② In a continuous range without phase change, there should be two or more coexisting oxidation states of the metal; ③ Its lattice should allow protons to be inserted freely (or removed by oxidation) through reduction to exchange O2 and OH -. So far, more and more metal oxides have been applied to pseudocapacitor supercapacitor, mainly including RuO2, MnO2, Co3O4, NiO, V2O5, Fe3O4, SnO2, Bi2O3, IrO2, etc.

1 Precious metal oxides

💥In the 1990s, when Conway was researching ruthenium oxide (RuO2) electrode materials, he found that it had the advantages of good conductivity, high stability, large specific capacitance, and fast charging and discharging. It was the first supercapacitor electrode to be researched. Material. After research, excellent electrochemical performance can be obtained, and its specific capacity is much higher than that of electric double layer capacitors. Among various oxides, RuO2 is considered to be the faraday pseudocapacitor electrode material with the best performance among the currently researched electrode materials for supercapacitor, and is considered to be the most promising material.

🌼As a supercapacitor electrode material, ruthenium oxide has many states, which can be generally divided into pure ruthenium oxide electrode material and composite ruthenium oxide electrode material. Pure ruthenium oxide electrode materials can be divided into crystalline materials and amorphous materials according to the form of ruthenium oxide. Since ruthenium oxide is expensive, it is a good choice to combine it with other materials with similar functions and cheap prices. Composite ruthenium oxide electrode materials can be divided into: composite materials with carbon, composite materials with other oxides, and composite materials with conductive polymers.

1.1 Crystalline ruthenium oxide electrode material and amorphous hydrated ruthenium oxide electrode material

☀️The U.S. Army Laboratory reported that the specific capacitance of its amorphous hydrate RuO2 can reach 768F per gram. Fang used thermal decomposition and oxidation method to make RuO2 thin film electrodes, and the specific capacitance of single electrode reached 380F; Hu prepared hydrated RuO2 by electrochemical deposition, the specific capacitance could reach 552F per gram, and the power density could reach 147kW per kilogram; Makino used liquid crystal material as template Electrodeposition of ordered mesoporous RuO2 materials, the specific capacitance can reach 12.6mF per square centimeter; Hu et al. successfully synthesized aqueous RuO2 (RuO2 xH2O) nanotube array electrodes using template synthesis and anode deposition techniques, with a maximum power density of 4320kW .J.P. Zheng Preparation of amorphous RuO2 xH2O electrode material by low-temperature annealing by sol-gel method.

🌈In its bulk phase, H+ is easily transported, so redox reactions can be carried out not only on its surface but also in its bulk phase. The electrode material has a high utilization rate, a specific capacitance of 768F, and an energy density of 96J; B. O. Park et al. obtained a thin-film RuO2 electrode by cathodic electrodeposition. Studies have shown that the specific capacity and charge-discharge interval are determined by the thickness of the electrodeposited RuO2 film.

When its mass density is 0.0014g, the specific capacitance of the electrode reaches 788F. But when the thickness of RuO2 film continues to increase, its surface morphology changes, the porosity of the outer layer decreases, and a dense inner layer is formed. On the contrary, its specific capacity decreases. Xia et al. RuO2 was prepared by hydrothermal reaction using RuCl3 as precursor. The results show that the material has high energy density and specific capacity, and good cycle stability. After 2000 cycles, its capacity value remained at 97% of the original value.

💐Highly dispersed nanoscale RuO2 particles have high specific capacitance, high energy density, high power density and good stability. Figure 3-1 shows the different morphologies of RuO2 in supercapacitor. Sho Makino et al. Japan studied the capacitive properties of low crystal water RuO2 nanoparticles and high crystal water RuO2 nanosheet electrode materials in the bioelectrolyte Acetobacter buffer. The experimental results show that the specific capacitance of RuO2 nanosheets in 5mol Acetobacter buffer reaches 1038F. The research results provide a new idea for the development of environmentally friendly materials.

1.2 Ruthenium dioxide/carbon composite electrode material

🌷In recent years, various RuO2/carbon composite electrode materials have also attracted attention. Carbon materials used as electrodes for electrochemical supercapacitor mainly include activated carbon powder, carbon black, carbon fiber, glassy carbon, carbon aerosol, carbon nanotubes, etc. Depositing RuO on high-surface-area carbon materials by various methods can increase the specific surface area of RuO, thereby increasing the specific capacitance of the material; adding ruthenium oxide to the carbon material can increase the specific capacity of the carbon material.

For example, the specific capacitance of RuO2/multi-walled carbon nanotube electrodes in sulfuric acid aqueous solution is as high as 1652F. The conductive carbon matrix greatly enhances the conductivity of the material, facilitates the penetration of ions, and significantly shortens the ion transmission distance. Wu used the sol-gel method and low-temperature heat treatment techniques to load RuO2 onto the graphene surface. Due to the high specific surface area and high conductivity of graphene, the utilization of RuO2 active material is greatly improved. It was found that when the loading amount of RuO2 reached 38.2%, the specific capacitance of the composite material was about 570F, which was similar to that of pure RuO2, and the composite material could significantly reduce the preparation cost of the electrode.

1.3 RuO2/conductive polymer composite electrode material

🌹With the broadening of research scope, RuO2/polymer composites have also received more and more attention, including RuO2/polyaniline, RuO2/polypyrrole and RuO2/polyethylene (3,4-ethylenedioxythiophene). Lin Zhidong et al. prepared the nanocomposite of RuO2 and polyaniline (PANi) by in-situ polymerization. When the RuO2 content is 3%, the specific capacity of the composite electrode reaches 373.27F. S. Cosnier et al compounded polypyrrole with RuO2 in different proportions to obtain higher specific capacity, but the power density needs to be improved

1.4 RuO2/other oxide composite electrode materials

🌺It is reported that ruthenium oxide and manganese oxide, nickel oxide, lead oxide, tungsten oxide, indium oxide, tin oxide, strontium oxide, cobalt oxide, tantalum oxide and other oxide materials with pseudo capacitance effect can be obtained by coprecipitation, colloid method, sol-gel method and other methods. The specific surface area of these binary metal oxide composite electrodes increases with the introduction of mixed metal oxides. At the same time, the use of these cheap materials can reduce the preparation cost of the electrodes, and of course, the functions will also decrease.

However, the overall performance of the materials (such as strontium oxide and indium oxide) will also be improved due to the synergistic effect of electrochemical performance. In addition, oxides without pseudocapacitance effect, such as silicon oxide and titanium oxide, are also made into various carriers with high specific surface area (such as film, mesh, nanotube and aerogel), and then ruthenium oxide is deposited on the carriers to increase their specific surface area and specific capacity. Yokoshima et al. successively prepared RuO2 and MoOx, VOx, TiO2, SnO2 and other composite electrode materials by the sol gel method, which played an excellent electrochemical performance of the composite electrode materials while reducing the amount of RuO2. Pani et al. coated Ru (OH) 4 and Ti (OH) 4 sol formed by hydrolysis of RuCl3 and TiCl3 in hydrochloric acid solution on Ti substrate to prepare Ti/TiO2+RuO2 composite electrode materials.

🌸At present, RuO2 materials are mainly used in aerospace, military science and other fields. Due to limited ruthenium resources and high prices, large-scale application is difficult. In addition, among the noble metal oxide electrode materials, IrO2 or RhOx materials are used as electrodes, which have Faraday pseudocapacitance characteristics similar to RuO2 electrodes. They all have good conductivity and can obtain high specific capacity and specific energy, but they are expensive. Therefore, it is necessary to find alternative materials or add other materials to reduce their consumption.

2 Transition metal oxides/hydroxides

🌼Although precious metal oxides and their composites can provide very high specific capacitance in supercapacitor, their high cost greatly limits their application in commercial production. Therefore, researchers are trying to explore using other transition metal oxides/hydroxides to replace noble metal oxides as electrode materials. Some cheap metal oxides, such as NiO, MnO2, Co3O4, SnO2, V2O5, have similar properties with RuO2, and are rich in resources and cheap in price, which has attracted extensive attention from researchers at home and abroad. Therefore, it has super capacitance characteristics.

2.1 Nickel oxide

🌻Nickel electrode materials have high specific capacitance, good magnification performance and stability, and are rich in reserves, low in price, green and non-toxic. It is a class of electrode materials with great development potential. Nickel oxide is mainly used in supercapacitor in the form of thin films. Its preparation methods include chemical precipitation, sol gel method, electrochemical method and template method. In addition, various nano nickel oxides with different morphologies, such as nanowires, nanoribbons, porous membranes, nanocones, nanorods, nano layers and nanospheres, have also been tried to be used as electrode materials for supercapacitor.

🌞Wang et al.obtained nickel oxide nanoribbons by simple hydrothermal method. Under 5A current density, its specific capacitance can be as high as 600F，The specific capacitance retention rate is 95% after 2000 cycles. Deng Meigen et al. prepared Ni (OH) 2 ultrafine powder by precipitation conversion method, and obtained NiO with an average diameter of about 10nm by heat treatment at 300 ℃. This method has simple experimental equipment and easy control of process conditions.

🌝The obtained nano NiO supercapacitor has typical Faraday pseudocapacitance characteristics. Under the charge/discharge current density of 2mA · cm-2, the specific capacity of electrode material reaches 243F.In spite of this, the reported specific capacitance of nickel oxide is still lower than its theoretical value, which can be attributed to its poor cycling performance and low conductivity.

🌛In order to solve these problems, it is an effective method to combine nickel oxide with cobalt oxide or conductive carbon materials to form composite materials. Because of the highly active nickel oxide surface layer, this composite material shows very high specific capacitance (900F), energy density (60W) and power density (10W); Symmetrical supercapacitor assembled from graphene/nickel oxide composites can also produce high specific capacitance (220F); In another work, nickel oxide repairThe specific capacitance of the composite was 816F · g-1 and its magnification property was good after three-dimensional graphene was decorated; The composite of nickel oxide and carbon nanotubes can improve the utilization of active substances in the materials and the specific capacitance can reach 384F · g-1.

🌕Liang Kun et al.constructed high-performance supercapacitor electrode materials such as nano porous NiO film and LaNiO3 doped mesoporous NiO film based on nano porous Ni film. These materials have large specific surface area, reasonable pore size distribution, and good conductivity. They can be directly used as electrode materials without using organic binders, showing good electrochemical performance. Although nickel oxide and nickel hydroxide have high theoretical specific capacitance and low cost, their potential windows are relatively low. How to increase the potential windows to meet the needs of practical commercial applications is still a problem to be solved.

2.2 Cobalt oxide and cobalt hydroxide

🌖Among various metal oxides, Co3O4 has been regarded as an advanced material with potential to replace RuO2 due to its low cost, high redox activity, theoretical specific capacitance up to 3560F, good reversibility and environmental friendliness.

🌱Lin prepared ultrafine Co2O3 electrode active material by alkoxide hydrolysis, and the specific capacity of single electrode reached 246F. However, CoOx dry gel synthesized by alkoxide sol gel method can obtain the maximum specific capacity of 291F at 150 ℃, which is very close to the theoretical value of 335F, and the cycle performance is stable.

🌿In recent years, scientists have also been working on the synthesis of Co3O4 nanostructures with different morphologies, such as nano layers, nanowires, nanotubes, nanorods, gel and microspheres . The specific capacitance of Co3O4 nano layer array can reach 2735F. Due to its unique three-dimensional layered structure, it has fast ion and electron transport characteristics. Mesoporous Co3O4 nanowire array can achieve a specific capacitance of 1160F, coated on foam nickelThereafter, the retention rate was 90.4% . Cobalt oxide nanotubes also exhibit good capacitive properties due to their unique structure and large specific surface area 

☘️In order to improve the conductivity of Co3O4 electrode, it was compounded with various carbon materials and applied in supercapacitor . For example, compared with pure Co3O4, the specific capacitance of cobalt oxide/carbon nanotube composite synthesized by coprecipitation method is significantly increased to 418F, which is due to the synergistic effect between Co3O4 and carbon nanotube. The maximum specific capacitance of the aqueous solution of graphene/Co3O4 composites is 243.2F. Three dimensional graphene foam based Co3O4 nanowires have a specific capacitance of 1100F and excellent cycle stability. The flexible Co3O4/graphene/carbon nanotube paper composite electrode shows a specific capacitance of 378F.

🍀The specific capacitance produced by potential deposition of stainless steel on cobalt hydroxide nano layer is 890F. Porous cobalt hydroxide/nickelThe conductivity of the composite was improved due to the introduction of nickel, and the specific capacitance was 1310F. The sea urchin like mesoporous cobalt hydroxide nanowires show a specific capacitance of 421F. The higher specific capacitance of the material is attributed to its ordered structure, layered porosity and good electrical conductivity. In order to further improve its electrochemical performance, conductive carbon materials (such as carbon nanotubes and graphene) have been used to construct cobalt hydroxide composite nanostructures .

The cohesionless cobalt hydroxide/carbon nanotube array electrode produces high capacitance (12.74F) and has excellent high magnification performance . Compared with pure cobalt hydroxide (726.1F), graphene/cobalt hydroxide composite exhibits high specific capacitance (972.5F). Although cobalt hydroxide and its derived composites show high specific capacitance, their practical application in supercapacitor will be greatly limited due to the low content of active substances and narrow potential range.

2.3 Manganese oxide

🍄Manganese based metal oxides have become the research focus of electrode materials for supercapacitor due to their low price, extensive resources, environmental protection and excellent electrochemical performance. At present, various MnO2 with different crystal structure, morphology and particle size have been studied, synthesized and applied to supercapacitor, and its theoretical specific capacitance can be as high as 1370F. There are many synthesis methods of MnO2 as electrode material of supercapacitor, such as low-temperature reduction method, chemical coprecipitation method, hydrothermal solvothermal synthesis, chemical microemulsion method, sol gel method, solution combustion method, solid phase reaction method, microwave assisted synthesis and deposition method.、

🌴Dangerous earthquake Kun prepared α、β、δ、γ The results show that they all have good capacitive characteristics, α- MnO2 has the highest specific surface area and porosity, its specific capacitance is up to 136F · g-1, but its high current discharge performance is poor, and the other three kinds of MnO2 have the same specific surface area. β- Although the specific capacitance of MnO2 is low (117.1F), its reasonable pore structure makes it have the best magnification characteristics and cycle stability.

🌳M.Kundu et al. Li Wenyao prepared single crystals by hydrothermal synthesis α- MnO2 ultra long nanowires, synthesized with surfactant α- MnO2 nanowires and nanorods. Through comparison, it was found that the electrochemical performance of the super long nanowire MnO2 electrode was the best, and its specific capacitance could reach 345F · g-1 when the current density was 1A · g-1. Wang et al. used one-step hydrothermal method to synthesize foam nickel loaded mesoporous MnO2/Ni (OH) 2 nanosheets. With the help of foam nickel high conductive framework, its specific capacitance reached 843F · g-1 when the current density was 2A · g-1. These indicate that the electrochemical performance of the electrode can be effectively improved by synthesizing nano materials with special morphology and structure.

🌲Yang et al. The charge/discharge test results show that the specific capacitance of the electrode material reaches 204F, and its capacity retention rate is close to 100% after 1000 cycles. Dong et al. obtained MnO2 nanoparticles through in-situ redox reaction between permanganate ions and carbon and embedded them in the mesoporous wall of carbon materials. This new structure of MnO2/mesoporous carbon composite has a specific capacitance of more than 2000F, and has high electrochemical stability and high reversibility.

🎄MnO2 has poor conductivity, so other metal elements (Co, Ni, Al, Mo, V, Fe, etc.) are mixed with MnO2 to form mixed oxides, and the conductivity of MnO2 is increased by introducing more carriers . 

🌵Proper doping can also effectively prevent MnO2 from dissolving, thus improving the electrochemical reversibility and cycle stability. Vanadium doping can effectively inhibit the growth of MnO2 crystal, while iron doping can improve the crystallinity and structural stability and reduce the concentration of unstable Mn3+[37]. The incorporation of metal oxides such as SnO2 and Co3O4 can provide a fast path for electron transport and increase the electrochemical applications of amorphous MnO2.

2.4 Iron oxide

🐲Iron oxides FexOy, such as Fe3O4 and Fe2O3, have low cost, relatively high theoretical Faraday capacitance and high conductivity (Fe3O4 is about 2 × 104S · m) and environmental friendly, but its electrochemical performance needs to be improved due to poor conductivity. It has been reported that the specific capacitance of hydrothermally synthesized iron oxide is 340.5F, and its electrochemical performance strongly depends on the grain size.

🐉In order to improve the electrochemical performance of iron oxide, many researchers have constructed nanostructures or carbon materials or conductive polymers with conductive phases. For example, the specific capacitance of graphene/iron oxide composite nanotubes is 215F, which is 7 times that of pure Fe2O3 [38]. Jin Yuhong et al. [39] prepared Fe2O3 hollow shuttle nanoparticles by template free hydrothermal method. The hollow pore structure can limit the electrolyte. While increasing the reaction site of the active substance, it shortens the transmission distance between the active substance and the electrolyte, ensuring the rapid transmission of ions. When the current density is 0.5A · g, the specific capacitance of the electrode material is 249F. Highly ordered α- Due to its unique nanostructure, iron oxide nanotube arrays can provide a fast transportation route and a solid structure, with a specific capacitance of up to 138F · g-1.

The maximum specific capacitance of graphene/ferric oxide/polyaniline ternary composite is 638F · g-1. In potassium hydroxide solution, its power density is 351W, energy density is 107W, and the specific capacitance attenuation is only 8% after 5000 cycles. The specific capacitance of carbon nanotube/nano-Fe3O4 composite is 165F, and after 1000 cycles, the specific capacitance is still about 85%.

🦄Recently, some researchers found that the external magnetic field has a great influence on the properties of graphene/iron oxide composites, and has obvious capacitance enhancement ability. At present, the electrochemical properties of iron oxides have not fully met expectations. Low conductivity and poor cycle stability are still the problems in the application of iron oxides in supercapacitor electrode materials.

3 Metal oxide composite-Supercapacitor

🦉As a new electrode material for supercapacitor, composite materials have become a research hotspot in recent years. Although metal oxide supercapacitor have developed rapidly and made some progress in theory and practice, the electrochemical properties of metal oxide supercapacitor still need to be further improved. The performance of supercapacitor can be effectively improved by compounding metal oxides with other materials with excellent capacitive properties and utilizing the synergistic effect between components.

3.1 Composite materials of different metal oxides

🐭Tao Jiayou et al. used MnO2 and molybdenum trioxide with the largest work function difference in transition metal oxides as the positive and negative electrode materials of asymmetric supercapacitor. MnO2 nanowires and molybdenum trioxide nanoribbons were synthesized by hydrothermal method, and carbon nanotubes were doped in a certain proportion to improve the conductivity of the electrodes. The results show that the operating voltage window of the asymmetric supercapacitor composed of these two electrodes is 0 ～ 2.0V, and its volume specific capacitance is 50.2F at the scanning speed of 2mV · s-1.

After further inserting an intermediate layer with an inline structure between the positive and negative electrodes, the operating voltage window of the device can reach 0-4.0V. When the power density is 261.4mW, the energy density of the capacitor can reach 28.6mW. After 10000 cycles of testing, the device can retain 99.6% of the initial capacitance. Xu et al. prepared flower like NiO/Co3O4 metal oxide composites by hydrothermal method, andThe Ni/Co ratio in the reaction solution regulates the morphology and electrochemical properties of the metal oxide composites.

🍏In 2017, Zheng Xin designed an energy band structure conducive to interface electronic transmission through the composite of different metal materials. TiO2 embedded layer was introduced at the interface of ZnO/Ni (OH) 2, and ZnO/TiO2/Ni (OH) 2 core-shell structure nanowire arrays were prepared as cathode materials, which effectively reduced the electronic interface transport barrier during charging, reduced the activation energy in reduction reaction, and increased the capacitance. He further prepared ZnO/Fe2O3 composite nano materials by hydrothermal method as the cathode of the supercapacitor, assembled an asymmetric supercapacitor, and expanded the voltage window of the device to 1.6V.

When the current density is 1A, the specific capacitance is l46.8F · g-1, and when the power density is 1350W, the energy density is 52.22W. Later, he further optimized the interface electron transport performance of cathode materials, and used hydrothermal method to grow ZnO/NiO core-shell structure nanowire arrays on three-dimensional carbon cloth substrate as flexible self-supporting electrodesGold nanoparticles are embedded at the interface of ZnO/NiO by ultraviolet reduction. When the current density is 5A, the capacitance of ZnO/Au/NiO electrode material is 4.1F, which is 720% higher than that of ZnO/NiO electrode material (0.5F). The embedding of Au can form a potential well between ZnO and NiO. During the charging process, a small amount of electrons can be captured, further improving the charge storage capacity of electrode material.

3.2 Carbon/metal oxide composite

🍎Carbon/metal oxide composites are widely used as electrode materials in supercapacitor, including carbon nanotubes (CNT)/metal oxide composites and graphene/metal oxide composites.

🍐Chen et al. prepared CNT/Ni (OH) 2 composite by direct hydrothermal method. This preparation method makes CNT uniformly dispersed in Ni (OH) 2 particles. Using 6mol solution as electrolyte, when the charging current is 5A, the specific capacitance of the composite is 1244.2F; When the current density is 20A · g-1, the specific capacitance remains at 771.3F · g-1, which is significantly higher than Ni (OH) 2 particles (372.1F) and CNT (101.4F). Based on the high specific surface area and high chemical stability of carbon nanotubes, the preparation of carbon nanotubes/metal oxide composites as support materials has been rapidly developed. However, due to different types and composite methods of oxides, the specific capacities of carbon nanotubes/metal oxide composite electrode materials vary greatly, as shown in Table 3-1.

🍊Graphene/metal oxide (hydroxide) composite materials use graphene oxide as the carrier, and use the oxygen containing groups on its surface as the anchor points of nanoparticles to deposit metal oxide particles on its surface. The synergistic effect of the two materials not only maintains the specific power of the supercapacitor, but also increases the specific energy and cycle stability of the system, and obtains electrode materials with excellent comprehensive performance. Chen et al. used the electrochemical deposition method to in-situ grow flower like MnO2 nanoparticles on the graphene surface, and the MnO2 nanoflowers uniformly grew on the graphene sheet to form a uniform electrode structure.

🍌The existence of MnO2 nanoparticles can increase the distance between graphene sheets, thereby promoting ion diffusion. Asymmetric supercapacitor is assembled with graphene as anode and MnO2 coated graphene as cathode. The specific capacitance and specific power of the capacitor are 328F · g-1 and 25.8kW · kg-1 respectively. Lee et al. used hydrothermal synthesis method to load Mn3O4 nanoneedles on graphene. In 1mol · L-1 Na2SO4 electrolyte, when the charge/discharge current density is 0.5A · g-1, 1A · g-1, 2A · g-1, 5A · g-1, 10A·At g-1, 15A · g-1 and 20A · g-1, the specific mass capacitances of the composites were 121F · g-1, 115F · g-1, 107F · g-1, 97F · g-1, 88F · g-1, 85F · g-1 and 83F · g-1 respectively (potential window was – 0.1~0.7V). After 10000 charge/discharge cycles (5A · g-1), the capacity retention rate was close to 100%.

🍉Compared with nano Mn3O4 electrode, it is found that the specific capacitance of graphene/Mn3O4 composite material is significantly increased, indicating that with the conductivity of graphene, the internal resistance of electrode material can be reduced and the effect of electrochemical polarization can be reduced; And the high specific surface area of graphene also improves the utilization rate of Mn3O4, thus increasing the specific capacitance of the composite. Similarly, the specific capacity of different graphene/metal oxide composite electrode materials varies greatly, as shown in Table 3-2.

🍋Although the composite of metal oxide particles and graphene can effectively improve the capacitance, and the composite is simple and easy, and the material structure and performance are diverse, there are also shortcomings such as high metal oxide price and heavy metal pollution.

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Highlights of the course-Xuansn  Capacitor

The host introduces the book and teachers, learning methods, classroom rules and conventions

Learning to share

Student group review

Certificate of Completion

💐For this training study, I would like to thank the company for its advance planning and careful preparation, which provides a platform for all managers to learn and grow. Thanks to the wonderful explanations and sharing of “dry goods” by the training teachers of Renben Education, the training scene was interspersed with on-site game interaction, questioning and other links, which enhanced the training scene atmosphere and training effect, and effectively improved the sense of ownership and management methods of grass-roots managers. Help Xuansn Electronics develop with high quality and high efficiency!

🌷In the theoretical system of the four functions, enterprise management is abstracted by process, and the purpose and basic objects of enterprise management cannot be seen, nor can people recognize the specific form of management work. No matter how far a social science develops with the times, it is difficult to deviate from its purpose, the basic object of research, and will not completely deviate from its original state in form. These three aspects can be summarized as its essence. For those who are engaged in business management, clarifying or re-examining the essence of business management can make management work more effective, and it can also make management research work more solid foundation and possible for long-term development.

🌹Generally speaking, the essence of enterprise management includes three aspects: (1) the basic object of enterprise management; (2) the purpose of enterprise management; (3) the basic characteristics of enterprise management. The following is a detailed sharing of the essence of enterprise management.

The basic objects of enterprise management

🌼In a market economy, the resources of an enterprise can be summed up in terms of people, money, and things. Wealth and things are interchangeable and are essentially different manifestations of value. In an enterprise, there is no property or property that does not belong to a person. The property and property belonging to a person are manifested as ownership, and the relationship between property, property and person is the attribution of ownership. According to this logic, business management only faces all kinds of people who have ownership of money and things.

🌻People are constantly allocating and trading ownership, and these activities are also all the contents of internal and external activities of enterprises. The continuous distribution and exchange of ownership between people can be summarized as the continuous occurrence of various interest relationships between people. The management of people in enterprise management is nothing more than the management of various interest relations in their work, whether it is governance or daily operation, it is the management of interest relations. The people in the enterprise are all based on the existence of the interest relationship as the basis for the relationship in the work. The basic relationship between superiors and subordinates is interest distribution and interest collection, and other working relationships occur on this basis. Other working relationships occur between colleagues based on the distribution of interests and cooperation of interests.

🍓Other working relationships occur between shareholders and managers based on the basic relationship of benefit agency and benefit distribution. Other working relationships occur between bosses and employees based on the distribution and transfer of benefits. The relationship between the enterprise and the outside is also based on the basic relationship between interests and all other relationships. Interest relationship is the basic relationship between people in an enterprise. If there is no interest, there is no relationship, no other relationship can occur, and there is no possibility of management.

The goals and objectives of business management

🍒The ultimate goal of business management is to maximize profits, but business management cannot directly achieve this goal. Neither corporate governance nor daily business activities can directly accomplish the realization of profits, they are all a part of realizing profit maximization. What these links need to do is to use their direct goals as a means to achieve the ultimate goal of profit maximization. Only when each link completes its direct goal under the guidance of the ultimate goal can the realization of the ultimate goal be guaranteed.

🍑The direct goal of enterprise management is to improve efficiency and achieve maximum output at the lowest cost in each link. Enterprises can maximize profits only when they maximize efficiency. Efficiency is not the same as speed, it is cost versus output, which includes the speed factor because time is also cost. This efficiency is the efficiency of all aspects of enterprise management, including innovation, development and design, capital operation, production, sales, procurement, transportation, warehousing, logistics, etc. Each link contains various functions, and the efficiency here also includes the efficiency of various functions.

🌈Before a general goal, only by refining the problem and decomposing the goal, and directing each specific action with the direct goal, it is possible to maximize the efficiency. It is possible to maximize profits only when all links have achieved the maximization of efficiency.

The basic characteristics of enterprise management

☀️Management is not only done by managers, all personnel of the enterprise are involved in management. Management is not as abstract as most people imagine, nor as clear and easy as the four functions in the theory describe. Managers are not as high-level, perfect, and high-quality as many people imagine “leaders”.

1. Management is the work of all employees

✨Enterprise managers need to manage subordinates, report to superiors and other management work involving others, and at the same time manage themselves. In terms of self-management, managers need to manage their own time, behavior, attitudes, equipment, tools, ideas, thoughts, etc. Managers need to coordinate relationship management and self-management in order to manage well. For example, in the construction of corporate culture, the leaders of the enterprise should not only let the whole enterprise recognize, absorb and implement the proposed values and concepts, but more importantly, they must have firm beliefs and core values, and guide their own behaviors to lead the way. The entire enterprise develops and influences all members of the enterprise to recognize and implement the concept and values.

2. Personnel in non-management positions also participate in management work

🌞In addition to cooperating with the management of managers, people in non-management positions are more self-management. They have to manage their time, tasks, behaviors, attitudes, relationships, equipment, tools, ideas, etc. These are management jobs. For non-managers, most of their work is done by their own management, and it is impossible for managers to guide or direct non-managers to complete their work in every detail.

3. Management is a very specific and complex job

🌝The management work of managers at all levels and non-managers is very specific and complex work, not as abstract and simple, clear and organized as many people imagine based on functional theory. Many times the management work is not clear and lacks the so-called order.

🍀①Senior managers, whose work mainly includes decision-making and diplomacy. Decision-making is something that some people imagine in the form of meetings, signatures, and decisions. Behind these forms are managers’ collection and processing of a large amount of information, long-term accumulated experience of failure and success, long-term thinking and keeping pace with the times. System thinking and core values formed in long-term management practice. In terms of diplomacy, it is by no means the forms of eating, drinking, meeting, and discussion that some people imagine. Behind these forms are the support of the strength of the enterprise, the adequate preparation of managers, the price of physical fitness, and even the entire enterprise staff. The result of a long struggle for it.

☘️②The main contents of the work of middle-level and grass-roots managers include decision-making transmission, decomposition of decision-making, coordination and arrangement of work, and even direct participation in the work of non-managers. Their work is not only in the form of uploading, participating in meetings, giving instructions, and arranging tasks, but also behind the collection and processing of information, the acquisition and accumulation of experience and lessons, the systematization of thinking, and the formation of values. , human coordination and a series of factors support.

🌿③ For non-managers, the work is more specific and detailed, including the management of equipment, tools, self, work tasks, etc. The objects and contents are very specific and most of them can be seen and touched. In addition, the work of everyone in the company is broken down into every minute and every detail.

🎄In a word, the essence of enterprise management includes three aspects: the most basic object of management is the interest relationship between people; the ultimate purpose of management is to maximize profits, but the direct purpose is to improve the efficiency of each link; Very specific and complex work involved.

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1.1 Monitoring of capacitor unbalanced current operation

🌟One of the most important functions of the AC filter and the shunt capacitor is to provide reactive power for the DC system. When the reactive power does not meet the absolute minimum filter (the absolute minimum filter capacity limit, the absolute minimum filter required to prevent the overload of the filter equipment) In any case, when this condition must be satisfied, it can lead to the occurrence of power reduction accidents in the DC system. During the operation of the DC system, operators should pay attention to the control mode of reactive power, the AC filter and the shunt capacitor input into the group When the power of the DC system changes, the switching of the filter, the backup of the filter and the parallel capacitor, etc. The above are the matters needing attention from the perspective of the AC filter and the parallel capacitor device for the safe and stable operation of the entire DC system.

✨As far as the AC and DC filter and shunt capacitor equipment itself is concerned, the operator should strengthen the monitoring of the unbalanced current of the bridge arm during the operation of the equipment. When the set value is reached, a corresponding alarm will appear in the background, but regularly pay attention to the unbalanced current situation and conduct trend analysis, which can indirectly grasp the operation of the capacitor in advance, and focus on the abnormal unbalanced current in the daily operation and maintenance. filter bank.

☀️The following takes a certain group of filters in the Yinchuan East converter station in the Ningdong-Shandong DC project as an example to illustrate how the operation and maintenance personnel can analyze the trend of unbalanced current: regularly copy the unbalanced current of the three phases of the capacitor (Note: Generally, regular refers to the time interval Certainly, but the analysis here mainly refers to the horizontal data comparison between the three phases. It is not particularly emphasized that the period of data copying must be constant, but the three-phase copying time should be consistent to ensure that the three phases are under the same operating conditions and environmental conditions. Comparability, because for the capacitor towers that have been precisely trimmed before being put into operation, the influence of the outside world and the system on the unbalanced current may be the main factor). As shown in Figure 2-14, the unbalanced current of the 3624 HP11/13 filter copied over a period of time is drawn with the Excel table function to draw the following trend analysis diagram. From the trend analysis chart, it can be seen that before February 28, 2012, the change trend of the unbalanced current between the three phases of the filter group was basically the same (data copied under the same operating conditions and environment). The change trends of the unbalanced currents of phases B and C are still the same, while the unbalanced current trend graph of phase A has left the “rank”, and the unbalanced current of phase A suddenly decreases greatly, indicating that the capacitance value of the capacitor bridge arm of phase A is relatively high. A large change will make the bridge arm more balanced. Conversely, the change in the capacitance value may also make the bridge hip more unbalanced. In both cases, operation and maintenance personnel should focus on strengthening monitoring.

🍎When the filter and shunt capacitor are newly put into operation or manually switched operation, attention should be paid to:

(1) When the new equipment is put into operation for the first time, it should be closed for 3 times at the rated voltage, and then open again after each closing. At least 10 minutes should be guaranteed until the next closing to ensure that the residual voltage of the capacitor discharges to within the required range.

(2) After the newly put into operation (including live debugging) about 2 hours, infrared temperature measurement should be carried out on the equipment.

(3) When the capacitor is newly put into operation for the first time (or put into operation after replacing the faulty capacitor), the unbalanced current needs to be initialized and calibrated on the protection device.

(4) The newly put into operation of the filter and shunt capacitor equipment should go to the wave recording device to print the recorded wave data when the equipment is put into operation, especially the filter and shunt capacitor with the phase selection closing device, so as to analyze whether the recorded wave data is normal or not. , and then it can be checked whether the debugged phase selection closing device is operating normally

1.2 Monitoring of the leakage current and operation of the arrester in the filter field

🍓The main purpose of monitoring the leakage current and operation of the arrester is to check whether the configuration and parameter settings of the arrester of the overvoltage protection device in the filter meet the design requirements and whether it can meet the purpose of protecting the operating equipment. Usually, the operation times and leakage current of the arrester in the filter fence are regularly recorded, and the operation of the arrester is analyzed in combination with the switching times of the filter, and the operation of the arrester can be understood from the side.

1.3 Monitoring the operation of capacitors in the filter

🍑Operation monitoring mainly refers to whether the capacitor joints are hot during operation, whether a single capacitor has bulging, oil seepage, whether there is foreign matter in the capacitor tower, etc. These are the main reasons that may cause capacitor failures.

🌼The above three items are what the operation and maintenance personnel need to pay attention to during the operation and maintenance of the equipment. The essence is the content of the daily operation and maintenance of the converter station filter equipment. The specific and detailed operation and maintenance items will be in the third section of this book. Detailed instructions in tabular form.

2 Basic requirements for the operation and maintenance of filter and shunt capacitor equipment

For the role of filters and parallel capacitors in the DC system, the following operating regulations should generally be noted:

(1) Under the normal operation of the DC system, the reactive power control mode (control of filter and parallel capacitor) is selected automatically.

(2) Under the normal operation of the DC system, the filter bank should be replaced, and the reactive power control should be switched to manual mode.

(3) Manual replacement of filters and parallel capacitors should follow the option of switching first and then cutting.

(4) When the filter and shunt capacitor are disabled, first open the circuit breaker, then open the load-side isolating switch, and then open the bus-side isolating switch. When throwing people, the sequence of operations is reversed.

(5) In the process of operation, it is found that a small amount of oil seeps through the capacitor. If it is determined by infrared temperature measurement that the capacitor has no abnormal heat, it is allowed to continue to operate. The monitoring of various state quantities of the capacitor should be strengthened (unbalanced current, infrared temperature measurement, appearance, etc.). ).

(6) Under normal circumstances, the infrared temperature measurement of the equipment should be carried out once a month, and the infrared temperature measurement should be carried out every week during the peak summer season.

(7) If abnormal discharge sound is found in the equipment during the inspection, the ultraviolet discharge test of the equipment should be carried out as soon as possible.

(8) Regularly record the operation times and leakage current of the arrester in the filter field.

(9) Regularly record and analyze the unbalanced current of the filter and parallel capacitor equipment.

(10) Carry out a nightly inspection of the equipment and equipment once a week to check whether there is any visible abnormal discharge in various equipment of the filter.

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