A method for finely controlling and preparing capacitor materials using micro-oxidized carbon materials

Abstract

The present invention discloses a method for preparing capacitor materials by finely controlling and micro-oxidizing carbon materials, comprising the following steps: (1) using coal powder as an activation raw material, and activating it at high temperature by an alkali activation method to obtain coal-based activated carbon; (2) subjecting the coal-based activated carbon obtained in step (1) to acid washing, water washing, deashing, and drying to obtain purified coal-based activated carbon; (3) finely controlling the purified coal-based activated carbon in step (2), mixing the purified activated carbon with a certain amount of sedimentation liquid for a period of time, performing liquid phase impregnation, filtering, drying, and carbonization deposition to obtain coal-based porous carbon; (4) uniformly mixing the coal-based porous carbon in step (3) with an oxidant solution, placing it in a water bath at a certain temperature, fully stirring for a period of time, performing surface oxidation treatment, and washing with water to obtain the final product, an ultra-microporous carbon electrode material. The present invention provides a high-value utilization method for coal, has low preparation cost, and produces a product with good electrical properties.

Description

Technical Field

[0001] The present invention relates to supercapacitor electrode materials, and specifically to a method for preparing capacitor materials by finely regulating and micro-oxidizing carbon materials. Coal-based carbon obtained by coal activation is used as a precursor, and liquid phase deposition + surface micro-oxidation modification is performed to finally prepare an ultra-microporous carbon electrode material suitable for different ion water-based supercapacitors (KOH, NaOH, LiOH). This material is rich in ultra-micropores below 1 nm and is mainly used as an electrode material for supercapacitors. Background Art

[0002] Capacitors have the advantages of high energy storage and high power density, and are widely used. Carbon materials are traditionally used as capacitor electrode materials. Currently, high-power electric vehicles and large mobile electric vehicles are becoming increasingly popular. Capacitors, with their "fast charge and discharge" characteristics, are beneficial for suppressing the high current generated during motor startup, preventing overload damage to the motor and circuits during startup. To meet energy storage needs, supercapacitors, which use traditional capacitor electrodes as the positive electrode and ion battery cathodes as the positive electrode, are rapidly developing. These require higher energy and power density of the electrode materials, and the development of low-cost supercapacitor electrode materials is urgently needed.

[0003] Traditional capacitor carbon materials utilize the double-layer structure formed on their surface in the electrolyte to achieve charge storage. However, the specific surface area that can be achieved by carbon materials prepared through processes such as activation, deposition, and template methods has an upper limit. At the same time, the equipment required for preparing ultra-high specific surface area carbon materials using vapor deposition and template methods is complex, and the raw material cost is too high, which is not conducive to the large-scale mass production of carbon materials. Currently, there are two difficulties in the preparation of microporous carbon materials. Although a high specific surface area can be achieved using a simple activation method, the activated carbon nanostructure obtained is uneven, and the pore size of the material cannot be precisely controlled, resulting in the actual capacity being far lower than expected; or the microscopic pore structure of the carbon material can be precisely controlled using methods such as vapor deposition, but this method requires complex equipment and a high level of technology, resulting in high costs and unsuitable for industrial production.

[0004] After Gogotsi first proposed in Science in 2006 that microporous desolvation can significantly improve the specific capacitance of porous carbon, a large number of studies have also found that carbon materials rich in ultramicropores <1nm can achieve desolvation of metal ions. Compared with carbon materials rich in mesopores, microporous carbon materials can obtain several times higher specific capacitance when the specific surface area is the same, but at the same time, too small pores are not conducive to the diffusion of ions in the electrode material.

[0005] Carbon sources such as bio-pyrolysis carbon and coal are mostly directly burned or used as adsorbents, which has low resource utilization efficiency and also causes pollution to the environment. The processed carbon materials are suitable for the preparation of cheap capacitor electrode materials, while also obtaining higher added value and helping the traditional mining industry to upgrade and transform. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing capacitor materials by finely controlling and micro-oxidizing carbon materials, to find a simple and high value-added processing and utilization method for coal, and to provide a new type of carbon-based electrode material for supercapacitors.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: a method for finely regulating and preparing capacitor materials using micro-oxidized carbon materials, comprising the following steps:

[0008] (1) Using coal powder as the activation raw material (but not limited to pyrolytic carbon and), the coal-based activated carbon is obtained by high-temperature activation using an alkali activation method;

[0009] (2) washing the coal-based activated carbon obtained in step (1) with acid and water to remove ash, and drying to obtain purified coal-based activated carbon;

[0010] (3) finely controlling the purified coal-based activated carbon in step (2), mixing the purified activated carbon with a certain amount of sedimentation liquid for a period of time, performing liquid phase impregnation, filtration, drying, and carbonization deposition to obtain coal-based porous carbon;

[0011] (4) The coal-based porous carbon in step (3) is evenly mixed with the oxidant solution, placed in a water bath at a certain temperature, stirred for a period of time, and subjected to surface oxidation treatment. After washing with water, the final product, the ultra-microporous carbon electrode material, is obtained.

[0012] Optionally, the raw material of the coal-based activated carbon powder described in step (1), the carbon source includes but is not limited to coal, including lignite, coking coal, 1 / 3 coking coal, etc., and the remaining carbon sources are also suitable for bio-pyrolysis carbon, including: coconut shell charcoal, peanut shell charcoal, bamboo charcoal, etc. Lignite is preferred, which is cheap, has moderate ash content, and is easy to activate. Alkali activators include potassium hydroxide, sodium hydroxide and mixtures thereof, and the mass ratio of coal to alkali is 1:2-1:6. The activation temperature is 700-1100°C. Preferably, lignite is used as the carbon source, potassium hydroxide is used as the alkaline activator, the mass ratio of coal to alkali is 1:3, and the activation temperature is 800°C.

[0013] Optionally, the coal-based activated carbon powder described in step (2) is purified by acid washing and water washing to a purity of 95% or more and a particle size D50 of 15-25 μm. This is the only way to prepare purified coal-based activated carbon. Preferably, the powder is acid washed with dilute hydrochloric acid, washed with water, and dried to obtain a purified coal-based activated carbon with a purity of 97% or more.

[0014] Optionally, the deposition liquid in step (3) is prepared by mixing a deposition precursor and a solvent in a certain mass ratio, wherein the deposition precursor comprises asphalt, phenolic resin, furfural resin, sucrose, and polyacrylonitrile, and the solvent comprises water, ethanol, acetone, etc. Preferably, phenolic resin is used as the precursor and alcohol is used as the solvent, and the mixture is immersed at 60°C for 24 hours. The alcohol solution facilitates the dissolution of the precursor and is also easy to mix with the purified coal-based activated carbon.

[0015] Optionally, the ratio of the purified coal-based activated carbon and the sedimentation liquid in step (3) is 1 g mixed with 20-50 ml of solution, the specific volume of the sedimentation liquid depends on the bulk density of the purified coal-based activated carbon, and the concentration of the sedimentation liquid depends on the precise control of the carbon microporous material size to be achieved.

[0016] Optionally, the carbonization deposition temperature in step (3) is 700-900° C., and the carbonization time is 1-4 hours, preferably 800° C. for 2 hours.

[0017] Optionally, the oxidant in step (4) is a dilute oxidant solution such as a dilute hypochlorous acid solution or a dilute hydrogen peroxide solution. The oxidant solution is uniformly mixed with the coal-based porous carbon, stirred in a water bath at a certain temperature for a period of time, and washed with water to obtain a microporous carbon electrode material. Preferably, the oxidant is a hydrogen peroxide solution, and the reaction temperature is 40-60°C.

[0018] Finally, the obtained oxidatively modified microporous carbon electrode material was tested and its specific surface area was greater than 1500m 2 / g. It can achieve high specific capacitance while also having good rate performance under large current.

[0019] The technology of the present invention is used to find a high-value utilization method for coal. The preparation cost of the present invention is low and the product has good electrical properties.

[0020] Compared with the prior art, the characteristics and beneficial effects of the present invention are:

[0021] (1) Wide range of raw materials and low cost

[0022] The raw coal used as raw material, primarily lignite with a low degree of metamorphism, is abundant. Simply by crushing the raw coal and subjecting it to traditional alkaline activation, a coal-based activated carbon precursor with a rich hierarchical pore structure, including micropores and mesopores, can be quickly obtained. Furthermore, after acid and water washing, the ash content of the resulting carbon material is below 5%. The raw coal used in this technology is relatively inexpensive, and the activation and deashing processes are simple and easy to perform, effectively reducing raw material costs.

[0023] (2) Precise hole adjustment method is simple and controllable

[0024] Using coal-based activated carbon as a carbon precursor and synthetic resin as a carbon source, the liquid phase impregnation carbon deposition method is used to control the carbon microporous pore structure. The deposition agent used in this technology is widely available, non-toxic and pollution-free. The process equipment only requires a deposition kettle and a carbonization furnace to prepare carbon materials with different ultra-micropores. According to the actual needs of the user, only the concentration, time, temperature and other process parameters need to be adjusted to prepare ultra-microporous carbon materials that can meet the different actual needs of different users.

[0025] (3) Surface micro-oxidation modification to improve electrical properties

[0026] The excessively small ultramicropores in microporous carbon materials will hinder the rapid entry and exit of ions and will also produce a large internal resistance. The use of surface micro-oxidation modification technology can effectively reduce the ion diffusion rate in the microporous electrode material and reduce the internal resistance of the electrode. This solves the shortcomings of traditional microporous materials, such as low Coulomb efficiency and poor rate performance under high current, and prepares an ultramicroporous carbon electrode material (Example 1). At a current density of 1A / g in KOH electrolyte, the specific capacitance is 273F / g, and at a current density of 20A / g, the specific capacitance retention rate reaches 67%.

[0027] (4) Wide range of uses and easy to expand

[0028] According to different uses and matching different calculation models, we can customize process solutions for ultra-microporous carbon materials for various purposes, and produce capacitor carbon materials suitable for different systems. At the same time, the uses can also be expanded to various aspects such as organic adsorption, gas separation, and catalyst carriers.

[0029] (5) The present invention uses natural coal as raw material, grinds and screens it, activates and carbonizes it, and uses coal-based activated carbon as the carbon source. Through a series of processes such as liquid phase deposition and surface micro-oxidation modification, the resulting carbon material is rich in fissure-like microporous structures, with a high content of ultra-micropores <1 nm. Simultaneously, the obtained electrode material also has the characteristics of rich surface functional groups, which can promote the diffusion of metal ions in it while ensuring that the electrode material obtains high specific capacitance. After the carbon material electrode is formed, the electrode internal resistance is small and the diffusion rate is fast, making it suitable for use as a supercapacitor electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the pore size distribution diagram of the ultra-microporous carbon electrode material prepared in Example 1;

[0031] Figure 2 The microporous structure of the ultra-microporous carbon electrode material prepared in Example 1;

[0032] Figure 3 This is the pore size distribution diagram of the ultra-microporous carbon electrode material prepared in Example 2;

[0033] Figure 4This is a diagram of the microporous structure of the ultra-microporous carbon electrode material prepared in Example 2;

[0034] Figure 5 This is the pore size distribution diagram of the ultra-microporous carbon electrode material prepared in Example 3;

[0035] Figure 6 This is a diagram of the microporous structure of the ultra-microporous carbon electrode material prepared in Example 3. DETAILED DESCRIPTION

[0036] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description in conjunction with the preferred embodiments.

[0037] Example 1:

[0038] A method for finely regulating and preparing capacitor materials using micro-oxidized carbon materials comprises the following steps:

[0039] (1) Preparation of coal-based activated carbon: Lean coal powder with a particle size of <125 μm and KOH were uniformly mixed in a mass ratio of 1:3, heated to 800 °C in a nitrogen atmosphere for 2 h, cooled, washed with distilled water, 7.5% dilute hydrochloric acid, and distilled water in sequence until neutral, dried, and sieved through a 300-mesh sieve to obtain a coal-based activated carbon sample.

[0040] (2) Carbon deposition and pore adjustment: Add 20 ml of a 0.05% phenolic resin aqueous solution to a beaker, then add 1 g of coal-based activated carbon. Immerse the mixture at 60°C for 24 h, filter, and dry. Heat the dried product to 800°C under a nitrogen atmosphere for carbonization and deposition, then maintain the temperature for 2 h. Cool the mixture to room temperature in the furnace, and grind and sieve to obtain a coal-based porous carbon sample with a particle size of <40 μm.

[0041] (3) Micro-oxidation modification: Add 1 g of coal-based porous carbon sample to a beaker, then add 25 ml of 40% H202, and add deionized water to make the total volume reach 100 ml. Place it in a water bath at 50°C for 1.5 hours, take it out and let it stand at room temperature for 12 hours. After standing, wash it with pure water and dry it at 60°C for 12 hours to obtain an ultra-microporous carbon electrode material.

[0042] Figure 1 This is the pore size distribution diagram of the ultra-microporous carbon electrode material prepared in Example 1; Figure 2 The microporous structure of the ultra-microporous carbon electrode material prepared in Example 1. The ultra-microporous carbon electrode material obtained in Example 1 has a specific surface area of ​​1632 m 2 In 1 mol / L KOH electrolyte, the discharge specific capacitance is 273 F / g at 1 A / g, and the specific capacitance retention rate is 67% at 20 A / g.

[0043] Example 2:

[0044] A method for finely regulating and preparing capacitor materials using micro-oxidized carbon materials comprises the following steps:

[0045] (1) Preparation of coal-based activated carbon: Lean coal powder with a particle size of <125 μm and an activator (KOH and NaOH mixed in a mass ratio of 1:1) were uniformly mixed in a mass ratio of 1:3, heated to 800 °C under a nitrogen atmosphere for 2 h, and washed with distilled water, 7.5% dilute hydrochloric acid, and distilled water in sequence after cooling until neutral. After drying, the mixture was passed through a 300-mesh sieve to obtain a coal-based activated carbon sample.

[0046] (2) Carbon deposition and pore adjustment: Add 30 ml of 0.01% phenolic resin ethanol solution to a beaker, then add 1 g of coal-based activated carbon, and soak at 60°C for 24 h. Filter and dry. Under a nitrogen atmosphere, heat the dried product to 800°C for carbonization and deposition, and keep it at this temperature for 2 h. Cool it to room temperature in the furnace, and grind and sieve to obtain a coal-based porous carbon sample with a particle size of <40 μm.

[0047] (3) Micro-oxidation modification: 1 g of porous carbon sample was added to a beaker, followed by 20 ml of 5% hypochlorous acid solution, and deionized water was added to make the total volume reach 100 ml. The sample was placed in a water bath at 50 °C for 1.5 h, and then taken out and allowed to stand at room temperature for 12 h. After standing, the sample was washed with pure water and dried at 60 °C for 12 h to obtain an ultra-microporous carbon electrode material.

[0048] Figure 3 This is the pore size distribution diagram of the ultra-microporous carbon electrode material prepared in Example 2; Figure 4 The microporous structure of the ultra-microporous carbon electrode material prepared in Example 2. The ultra-microporous carbon electrode material obtained in Example 2 has a specific surface area of ​​1502 m 2 In 1 mol / L NaOH electrolyte, the discharge specific capacitance is 163 F / g at 1 A / g, and the specific capacitance retention rate is 55% at 20 A / g.

[0049] Example 3:

[0050] A method for finely regulating and preparing capacitor materials using micro-oxidized carbon materials comprises the following steps:

[0051] (1) Preparation of coal-based activated carbon: 1 / 3 coking coal powder with a particle size of <125 μm and KOH were uniformly mixed in a mass ratio of 1:4, heated to 800 °C under a nitrogen atmosphere for 2 h, and washed with distilled water, 7.5% dilute hydrochloric acid, and distilled water in sequence after cooling until neutral. After drying, the mixture was passed through a 300-mesh sieve to obtain a coal-based activated carbon sample.

[0052] (2) Carbon deposition and pore adjustment: Add 20 ml of 0.05% phenolic resin ethanol solution to a beaker, then add 1 g of coal-based activated carbon, and soak at 60°C for 24 h. Filter and dry. Under a nitrogen atmosphere, heat the dried product to 800°C for carbonization and deposition and keep it at this temperature for 2 h. Cool it to room temperature in the furnace, and grind and sieve to obtain a coal-based porous carbon sample with a particle size of <40 μm.

[0053] (3) Micro-oxidation modification: Add 1 g of porous carbon sample to a beaker, then add 20 ml of 10% hydrogen peroxide solution, add deionized water to make the total volume reach 100 ml, and place in a water bath at 50°C for 1.5 hours. After taking out, let it stand at room temperature for 12 hours. After standing, wash with pure water and dry at 60°C for 12 hours to obtain an ultra-microporous carbon electrode material.

[0054] Figure 5 This is the pore size distribution diagram of the ultra-microporous carbon electrode material prepared in Example 3; Figure 6 The microporous structure of the ultra-microporous carbon electrode material prepared in Example 3. The ultra-microporous carbon electrode material obtained in Example 3 has a specific surface area of ​​1526 m 2 In 1 mol / L LiOH electrolyte, the discharge specific capacitance is 160 F / g at 1 A / g, and the specific capacitance retention rate is 35% at 20 A / g.

[0055] The above description is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principles of the present invention. These improvements and changes are also considered to be within the scope of protection of the present invention.

Claims

1. A method for finely controlling and preparing capacitor materials using micro-oxidized carbon materials, characterized in that: The following steps are involved: (1) Using coal powder as the activation raw material, the coal-based activated carbon is obtained by high-temperature activation using an alkali activation method; (2) washing the coal-based activated carbon obtained in step (1) with acid and water to remove ash, and drying to obtain purified coal-based activated carbon; (3) finely controlling the purified coal-based activated carbon in step (2), mixing the purified activated carbon with a certain amount of sedimentation liquid for a period of time, performing liquid phase impregnation, filtration, drying, and carbonization deposition to obtain coal-based porous carbon; (4) The coal-based porous carbon in step (3) is evenly mixed with the oxidant solution, placed in a water bath at a certain temperature, stirred for a period of time, subjected to surface oxidation treatment, and washed with water to obtain the final product, an ultra-microporous carbon electrode material; The raw materials of the coal-based activated carbon powder in step (1) include coal as the carbon source, including lignite, coking coal, and 1 / 3 coking coal; the alkali activator includes potassium hydroxide, sodium hydroxide, and a mixture thereof; the mass ratio of coal to alkali is 1:2-1:6; and the activation temperature is 700-1100°C; The coal-based activated carbon powder described in step (2) is purified by acid washing and water washing to achieve a purity of more than 95% and a particle size D50 of 15-25 μm; The pickling is carried out using dilute hydrochloric acid; The deposition liquid in step (3) is prepared by mixing a deposition precursor with a solvent and immersing the mixture at 60° C. for 24 hours, wherein the deposition precursor comprises asphalt, phenolic resin, furfural resin, sucrose and polyacrylonitrile, and the solvent comprises water, ethanol and acetone; The ratio of the purified coal-based activated carbon and the sedimentation liquid in step (3) is 1 g mixed with 20-50 ml of the solution; The temperature of the carbonization deposition in step (3) is 700-900° C., and the carbonization time is 1-4 hours; The oxidant in step (4) is a dilute hypochlorous acid solution or a dilute hydrogen peroxide solution, and the reaction temperature is 40-60°C.

2. The method for preparing capacitor materials by fine-tuning and micro-oxidized carbon materials according to claim 1, characterized in that: The raw materials of the coal-based activated carbon powder described in step (1) are lignite as the carbon source, potassium hydroxide as the alkali activator, the coal to alkali mass ratio is 1:3, and the activation temperature is 800°C.

3. The method for preparing capacitor materials by fine-tuning and micro-oxidized carbon materials according to claim 1, characterized in that: The temperature of the carbonization deposition in step (3) is 800° C., and the carbonization time is 2 hours.

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