CN1402273A - Process for preparing high specific capacitance electrode material - Google Patents

Abstract

The invention provides a method for preparing high specific capacitance electrode material. The method uses petroleum coke or pitch coke as raw material and KOH as activator to prepare powdered activated carbon with high specific surface area, and uses phenolic resin and furfural to prepare acrylic acid with a concentration of 7 to 15g/100ml in a weight ratio of 1:1.2 to 1.8. Alcohol solution, the amount of catalyst is 7-15mmol/ml, react at 60-100°C for 4-7 days to form alcohol gel, dry in 250-300°C, 6-8MPa supercritical petroleum ether for 1-3 hours to form phenolic gas Gel, the aerogel is carbonized at 600-1000°C for 1-3 hours to produce carbon aerogel; the two are mixed in a ratio of 1:0.05-1 (weight ratio), and 2-10% binder is added, Mix evenly to prepare high specific capacitance electrode material. The specific capacitance of the electrode material (AC:A=1:0.2) prepared by the method is as high as 330F/g at normal temperature. The electrode material has the advantages of simple preparation method, high specific capacitance, good conductivity, etc., and provides good prospects for large-scale application of electric double layer capacitor technology.

Description

A kind of preparation method of high specific capacitance electrode material

Field:

The invention belongs to a preparation method of a high specific capacitance electrode material for an electric double layer capacitor. In particular, it relates to a method for preparing electrode materials of electric double layer capacitors by using activated carbon with high specific surface area and carbon aerogel as raw materials.

Background technique:

The electric double layer capacitor is a new type of energy storage device, which is made of the electric double layer formed on the interface between the electrode and the electrolyte. It has the characteristics of farad level capacitance and voltage memory function, and its power density is much higher than that of ordinary batteries. , the energy density is much higher than traditional capacitors, thus filling the gap between these two traditional technologies. Electric double layer capacitors have broad application prospects in both military and civilian applications. Electric double-layer capacitors with small current discharge can be used as backup power for microcomputers or primary power for small devices such as toys, alarms, signal lights, etc.; ampere-level high-current discharge electric double-layer capacitors can be used alone or together with batteries to form a power system. It can be used as starting power supply and driving power supply for small loads, such as starting power supply for tanks, airplanes, rockets, missiles, etc. Electric double layer capacitors have higher specific power and longer cycle life than traditional rechargeable batteries (including nickel-metal hydride batteries and lithium-ion batteries). service life of more than 5 years). High-power electric double-layer capacitors are of special significance for the starting, acceleration and uphill driving of electric vehicles; for the management of battery energy systems of electric vehicles, prolonging the cycle life and optimal use of batteries, and the starting of fuel cell electric vehicles It is even more essential. In view of the importance of electric double layer capacitors, all industrialized countries have attached great importance to them, and made them a national key strategic research and development project.

The core of an electric double layer capacitor is the manufacturing technology of the electrode material, and its performance depends critically on the performance of the electrode material. Materials with large specific surface area such as activated carbon, activated carbon fiber, carbon aerogel, etc. have been studied as active electrode materials and some materials (such as activated carbon) have been industrialized. At present, activated carbon and activated carbon fiber cloth are widely used electrode materials. The specific capacitance of ordinary activated carbon is generally below 150F/g, and the energy density is less than 3Wh/Kg. Due to the poor conductivity of activated carbon materials, it is necessary to add some high-conductivity substances such as graphite, carbon fiber, metal fiber, etc. to improve the conductivity and reduce the internal impedance of the electrode. The only function of these conductive materials in the electrode is to increase the conductivity between the activated carbon particles, which does not contribute to the energy storage of carbon electrodes due to their small specific surface area. The amount of conductive material added is generally 10-20% of the mass of the carbon electrode. Therefore, the addition of conductive material reduces the energy density and power density of the capacitor to a large extent. For example, to manufacture an electric double layer capacitor with the same capacity, due to the addition of conductive materials, the quality and manufacturing cost of the capacitor will be greatly increased, causing inconvenience in the actual application process. Therefore, the development of electrode materials with good conductivity is a hot issue that people are currently interested in, and these materials generally include carbon aerogels, carbon nanotubes, etc. Due to the high price, specific surface area and small specific capacitance of carbon nanotubes, the manufacturing cost of capacitors is doubled, which limits its application. Carbon aerogel is a kind of nanoporous material, which has the characteristics of large specific surface area and good electrical conductivity. The electrical performance test results of carbon aerogel show that the electrical conductivity of carbon aerogel is very high (about 25Scm ^-1 ) , and remain basically unchanged in a wide temperature range (-30 ~ 100 ° C), so the electric double layer capacitor made of carbon aerogel as electrode material can be used in a wide temperature range. However, due to the small specific surface area, generally below 1000m ² /g, carbon aerogels store less energy, which affects the energy density and power density of electric double layer capacitors in large-scale applications.

Invention content:

The purpose of the present invention is to develop a high specific capacitance and simple method for preparing an electric double layer capacitor electrode material.

The specific surface area of activated carbon with high specific surface area is more than 3000m ² /g, which can provide the largest active surface to form an electric double layer to store charges; carbon airgel has good conductivity, and it has a large specific surface area and mesopores The structure can store a considerable amount of energy. Therefore, the high specific surface area activated carbon and carbon aerogel mixed to make electrodes can give full play to the advantages of both. Specific capacitance and energy density of electrode materials.

The preparation method of the electrode material in the present invention is prepared by using activated carbon with high specific surface area and carbon aerogel as raw materials, adding binder and mixing according to a certain ratio.

The preparation method of the present invention comprises the steps:

(1) Preparation of aldehyde resin-based carbon airgel

The phenolic resin and furfural are formulated into a propanol solution with a concentration of 7-15g/100ml in a ratio of 1:1.2-1.8 by weight, and the catalyst dosage is 7-15mmol/ml, and react at 60-100°C for 4-7 days to form alcohol Gel, dry in supercritical petroleum ether at 250-300°C and 6-8MPa for 1-3 hours to form phenolic airgel, and carbonize the airgel at 600-1000°C for 1-3 hours to produce carbon aerogel;

(2) Preparation of specific capacitance electrode material

Mix activated carbon and carbon airgel with a particle size of less than 50m and a specific surface area of more than 3000m ² /g at a weight ratio of 1:0.05~1, ball mill for 1-3 hours to make the particle size of the mixture <50m, and then add 2-5 % polytetrafluoroethylene emulsion, stirred evenly, and molded under the pressure of 5-10MPa after drying.

The above-mentioned high specific surface area activated carbon is prepared by using petroleum coke or pitch coke as raw material, KOH as activator, and activating at 700-1000°C for 0.5-2.0 hr.

The catalyst described above is 5% methanolic hydrochloric acid.

The present invention adopts the method of adding carbon aerogel to the activated carbon with high specific surface area, and can use the micropores of the activated carbon and the mesopores of the carbon aerogel to store charges during the charging and discharging process of the electrode, thereby greatly improving the specific capacitance of the material. In addition, the high conductivity of carbon airgel can replace graphite to increase the conductivity between activated carbon particles, avoiding the decline in energy and power density caused by the use of graphite. The electrode material prepared by the method has a specific capacitance of 230-330 F/g at a charging and discharging current density of 1 mA/cm ² .

Detailed ways:

comparative example

Take 40 grams of petroleum coke, mix it with 200 grams of KOH, and activate it at 810°C for 1 hour to prepare powdery activated carbon with high specific surface area. The BET specific surface area reaches 3200m ² /g, and the specific capacitance is 280F/g.

The phenolic resin and furfural were formulated into 10g/100ml propanol solution with a weight ratio of 1:1.6, the catalyst dosage was 10mmol/100ml, reacted at 80°C for 6 days to form alcohol gel, and dried in supercritical petroleum ether for 1 The phenolic aerogel was formed within hours, and the aerogel was carbonized at 800°C for 3 hours to produce carbon aerogel. The carbon airgel has a specific surface area of 597m ² /g and a specific capacitance of 153.6F/g.

Example 1

Take activated carbon with a BET specific surface area of 3200m ² /g. The phenolic resin and furfural are formulated into 12g/100ml propanol solution with a weight ratio of 1:1.6, the catalyst dosage is 8mmol/100ml, react at 80°C for 6 days to form alcohol gel, and dry in supercritical petroleum ether for 2 The phenolic aerogel was formed within hours, and the aerogel was carbonized at 800°C for 2 hours to produce carbon aerogel. The specific surface area of carbon airgel is 632m ² /g. Mix activated carbon and carbon airgel at a weight ratio of 1:0.05, ball mill for 3 hours to make the particle size of the mixture <50m, then add 2% polytetrafluoroethylene emulsion to the mixture, stir evenly, dry and shape under 10MPa pressure . The specific capacitance of the electrode material is 302F/g.

Example 2

Take activated carbon with a BET specific surface area of 3200m ² /g. Phenolic resin and furfural were formulated into 14g/100ml propanol solution with a weight ratio of 1:1.8, the catalyst dosage was 10mmol/100ml, reacted at 80°C for 6 days to form alcohol gel, and dried in supercritical petroleum ether for 1 The phenolic aerogel was formed within 1 hour, and the aerogel was carbonized at 900° C. for 2 hours to produce carbon aerogel. The specific surface area of carbon airgel is 640m ² /g. Mix activated carbon and carbon aerogel at a weight ratio of 1:0.15, ball mill for 2 hours to make the particle size of the mixture <50m, then add 5% polytetrafluoroethylene emulsion to the mixture, stir evenly, dry and shape under 10MPa pressure . The specific capacitance of the electrode material is 312F/g.

Example 3

Take activated carbon with a BET specific surface area of 3600m ² /g. Phenolic resin and furfural were formulated into 15g/100ml propanol solution with a weight ratio of 1:1.4, the catalyst dosage was 15mmol/100ml, reacted at 90°C for 5 days to form alcohol gel, dried in supercritical petroleum ether for 1 The phenolic aerogel was formed within hours, and the aerogel was carbonized at 700°C for 3 hours to produce carbon aerogel. The specific surface area of carbon airgel is 578m ² /g. Mix activated carbon and carbon aerogel in a weight ratio of 1:0.15, ball mill for 3 hours to make the particle size of the mixture <50m, then add 2% polytetrafluoroethylene emulsion to the mixture, stir evenly, dry and shape under 5MPa pressure . The specific capacitance of the electrode material is 320F/g.

Example 4

Take activated carbon with a BET specific surface area of 3600m ² /g. Phenolic resin and furfural were formulated into 10g/100ml propanol solution in a ratio of 1:1.2 by weight, and the amount of catalyst used was 12mmol/100ml, reacted at 70°C for 7 days to form alcohol gel, dried in supercritical petroleum ether for 2 The phenolic aerogel was formed within hours, and the aerogel was carbonized at 850° C. for 2 hours to produce carbon aerogel. The specific surface area of carbon airgel is 682m ² /g. Mix activated carbon and carbon aerogel at a weight ratio of 1:0.2, ball mill for 3 hours to make the particle size of the mixture <50m, then add 3% polytetrafluoroethylene emulsion to the mixture, stir evenly, dry and shape under 7MPa pressure . The specific capacitance of the electrode material is 330F/g.

Example 5

Take activated carbon with a BET specific surface area of 3600m ² /g. The phenolic resin and furfural are formulated into 10g/100ml propanol solution with a weight ratio of 1:1.6, the catalyst dosage is 7mmol/100ml, react at 90°C for 7 days to form alcohol gel, and dry in supercritical petroleum ether for 2 The phenolic aerogel was formed within hours, and the aerogel was carbonized at 850° C. for 2 hours to produce carbon aerogel. The specific surface area of carbon airgel is 582m ² /g. Mix activated carbon and carbon airgel at a weight ratio of 1:0.4, ball mill for 3 hours to make the particle size of the mixture <50m, then add 2% polytetrafluoroethylene emulsion to the mixture, stir evenly, dry and shape under 10MPa pressure . The specific capacitance of the electrode material is 284F/g.

Example 6

Take activated carbon with a BET specific surface area of 3600m ² /g. Phenolic resin and furfural were formulated into a 7g/100ml propanol solution with a weight ratio of 1:1.5, and the catalyst dosage was 12mmol/100ml, reacted at 90°C for 7 days to form an alcohol gel, and dried in supercritical petroleum ether for 2 The phenolic aerogel was formed within hours, and the aerogel was carbonized at 850° C. for 2 hours to produce carbon aerogel. The specific surface area of carbon airgel is 652m ² /g. Mix activated carbon and carbon aerogel at a weight ratio of 1:1, ball mill for 3 hours to make the particle size of the mixture <50m, then add 2% polytetrafluoroethylene emulsion to the mixture, stir evenly, dry and shape under 10MPa pressure . The specific capacitance of the electrode material is 238F/g.

Claims (3)

1. the preparation method of a high specific capacitance electrode material, it is to be that raw material, KOH are that activator prepares the high-specific surface area powdered activated carbon with petroleum coke or pitch coke, and after being the feedstock production charcoal-aero gel with phenolic resins, furfural, with the two mixed with 1: 0.05～1 (weight ratio), add the 2-10% binding agent, mix and make high specific capacitance electrode material.

2. the method for claim 1 is characterized in that with high-specific surface area and charcoal-aero gel with 1: 0.05～1 mixed, normal temperature adds the 2-10% binding agent down and makes electrode material.

3. method as claimed in claim 2 is characterized in that used binding agent is a ptfe emulsion.