KR101321523B1

KR101321523B1 - Manufacturing of active carbon for capacitor electrode using NaOH chemical activation and a capacitor made thereof

Info

Publication number: KR101321523B1
Application number: KR1020110080766A
Authority: KR
Inventors: 이종대
Original assignee: 충북대학교 산학협력단
Priority date: 2011-08-12
Filing date: 2011-08-12
Publication date: 2013-11-21
Also published as: KR20130017989A

Abstract

The present invention relates to the production of activated carbon as a capacitor electrode material by activating a low-cost palm charcoal using NaOH. The specific surface area and pore size can be freely adjusted according to the activation conditions to achieve a high specific surface area (1500㎡ / g). And a method for producing activated carbon having a pore size (1.5 to 5 nm). The present invention can provide a variety of specific surface area and pore structure of the activated carbon prepared by adjusting the type and composition of the activated chemical, the active gas, the activation temperature, the temperature raising method and the like by using the coconut shell charcoal. The activated carbon may be used as an anode and cathode electrode material of an electric double layer capacitor and as an anode electrode of a high capacity, high output hybrid capacitor, and is highly developed in the case of a hybrid capacitor using a Li salt-based cathode electrode and an activated carbon anode electrode. Charge and discharge characteristics can be given.

Description

Manufacture of active carbon for capacitor electrode using NaOH chemical activation and a capacitor made thereof

The present invention relates to a method for producing activated carbon with mesopores using coconut shell charcoal as a raw material, and utilizing it as a capacitor electrode material. More specifically, the activated carbon thus prepared is used as an anode electrode and a Li salt metal. A method of manufacturing a hybrid capacitor using an oxide (cobalt, manganese) as a cathode electrode, or a method of manufacturing an electric double layer capacitor using the activated carbon as an anode and a cathode. That is, in the present invention, various high specific surface areas (1500 to 3000 m 2 / g) and mesopores (1.5) are used while changing the activation temperature, the temperature increase rate, the type and flow rate of the activation gas, the weight of the raw material, etc. using a chemical activation method with NaOH. It relates to a method of manufacturing activated carbon that can be utilized as a high capacity capacitor electrode material and a capacitor using the same.

Recently, hybrid capacitors have been of interest for securing stable electrical energy and excellent energy storage devices. Hybrid capacitors have been developed in order to improve energy density, which is a disadvantage of high charge / discharge efficiency, output density, and semi-permanent cycle characteristics, which are advantages of the conventional electric double layer capacitor (EDLC). The development of hybrid capacitor technology to take advantage of energy density and the high power density of EDLC is also drawing attention. As a result, the development of next generation hybrid capacitors with high reliability and safety with high energy density and power density characteristics is in progress, and an energy storage system that can satisfy both aspects of energy density and power density in energy sustainability and efficiency is required. ought. Recently, a case of using a metal oxide containing lithium salt as an electrode material has been reported in the process of manufacturing a hybrid capacitor, and they have been reported to have a higher energy density than a conventional capacitor. Hybrid capacitors are expected as a technology that can create new markets in the field of environmental energy for the purpose of saving energy and effectively utilizing natural energy such as electric vehicles, railway vehicles, solar and wind power generation facilities.

The hybrid capacitor is composed of a separator and an electrolyte that carries current collectors and ions, which are flow paths of positive and negative electrodes and electrons separated by the separator. Such hybrid capacitors have fields such as separation membrane, electrolyte, and electrode manufacturing technology, and researches on electrodes mainly use activated carbon as anode electrode, and technology development on specific surface area, pore size, electrical conductivity and surface chemical characteristics This is mainly going on. In addition, the hybrid capacitor uses a single-component, two-component, and ternary system including Li salt-based cobalt, manganese, iron, and nickel as cathode electrodes to increase energy density. In the field of electrolytes, technology development for investigating the effects of charge mobility and electrical conductivity on electrochemical properties is in progress, and various organic electrolytes are used. The anode electrode active material of the hybrid capacitor requires a large specific surface area, moderate pore distribution, high electrical conductivity, and chemical stability, and activated carbon is the most used to date.

As an electrode material, many studies have been conducted to investigate the effect of the physical properties of activated carbon on the electrochemical properties. According to recent research results, the increase of specific surface area generally increases the filling capacity. However, if the specific surface area is above a certain surface area, there is a research result that the development of mesopores greatly affects the filling capacity in the case of organic electrolyte rather than micropores. In the case of an organic electrolyte having a larger ion size than an aqueous electrolyte, it is affected by the diffusion resistance due to the pore size. Many research results for controlling the specific surface area and porosity of the activated carbon electrode by various activation methods have been reported, and the development of technology to increase the electrochemical characteristics by chemical modification of the surface of activated carbon is actively progressing.

In general, a method of controlling the specific surface area of activated carbon and the size or fraction of micropores or mesopores is used as a catalyst for polymer blend carbonization, transition metals and rare earth metals, which carbonize polymers by physically or chemically mixing different types of polymers. This can be categorized into a catalyst activation method for activating at high temperature, a sol-gel activation method for controlling pore and specific surface area of activated carbon by adjusting pH when mixing Resorcinol and Formaldehyde, and template carbonization method using silica matrix. Recently, as the synthesis of high-capacity materials through chemical activation treatment has been newly introduced, the technology of manufacturing activated carbon having high specific surface area and mesopores has become a focus of attention. Therefore, the present invention controls the specific surface area and the mesopores by using NaOH chemical activation method, which is known to develop mesopores relative to KOH as a raw material of coconut shell charcoal, and has a high specific surface area that can be utilized as a high capacity supercapacitor electrode material. Activated carbon and mesopores are to include the contents of the manufacturing process.

The present invention is a technology for manufacturing the activated anode electrode active carbon used in the hybrid capacitor which is an electric energy storage device using the charcoal of charcoal and NaOH as a high specific surface area activated carbon and mesopores using various active conditions. The present invention also provides a method for producing activated carbon for electrode materials for reducing the diffusion resistance of electric charges and producing a high capacity capacitor by manufacturing advanced activated carbon. The present invention also provides an activated carbon anode electrode and Li salt prepared as described above. Provided is a hybrid capacitor that uses an included metal oxide cathode electrode to improve the energy density, which is a disadvantage of the capacitor. Therefore, the object of the present invention is to replace the expensive activated carbon by establishing activated carbon manufacturing technology according to changes in the type and composition of activated chemicals, active gas, activation temperature, temperature raising method, etc. The present invention provides a method of manufacturing activated carbon for a capacitor to realize a capacitor. Activated carbon prepared according to the present invention has a high specific surface area having a very large specific surface area while the mesopores are developed more than the conventional activated carbon by activating with NaOH when the activated carbon has a high specific surface area. ㎡ / g) and at the same time relatively high charge-added high performance capacitors by manufacturing electrode materials with average mesopores of 1.5 to 5 nm and using various conductive agents and binder electrolytes, which are known to reduce the charge transfer resistance to the electrode surface. It can be used to secure price competitiveness of products and global technological competitiveness.

The present invention to solve the problems as described above;

As a method for producing activated carbon for capacitors having a specific surface area of 1500 to 3000 m 2 / g and mesopores of 1.5 to 5 nm, for use of a capacitor electrode material having a charging capacity of 0.3 to 1.0 F / cm 2,

Grinding and mixing sodium hydroxide (NaOH) and coconut shell charcoal in a weight ratio of 0.2 to 10: 1 (S1);

Activating the mixture at a temperature of 700 to 900 ° C. in a tube furnace to prepare activated carbon (S2);

Removing impurities of the activated carbon prepared in step S2 (S3); And,

It provides a method for producing activated carbon for a capacitor comprising the step (S4) of washing and drying after the step (S3).

Since the weight ratio in the step (S1) is very influenced by the specific surface area and the pore size of the activated carbon produced according to the weight ratio of NaOH / coconut shell charcoal, the effect of the case where the weight ratio is small from 1 to large, If the weight ratio is too large, the density is small and the yield is low, so that it cannot be used, so it is within the above range.

NaOH in the above can also use a liquid phase.

In addition, the coconut shell charcoal in the step (S1) is preferably used having a size of 0.6 ~ 5mm, 0.6mm or less in the case of powder, 1 ~ 5mm in the case of granule, but there is no big difference by the particle size .

In addition, the activation in the step (S2) is preferably carried out while controlling the reaction atmosphere by injecting argon and / or nitrogen gas at a flow rate of 100 ~ 1000㏄ / min, in order to prevent oxidation under a reducing atmosphere, The range of the flow rate was determined to be the optimum range of activation.

In addition, the activation in the step (S2) is preferably heated to 0.1 ~ 10 ℃ / min and maintained for 30 to 180 minutes at the activation temperature, and then slowly cooled, the most preferred activation is 5 ℃ / min.

If the activation treatment time is 30 minutes or less in the above, a sufficient reaction does not occur, and the activation reaction proceeds at 3 hours or more, and thus is activated at this time.

In addition, the neutralization and impurity removal in the step (S3) is preferably treated for 20 to 60 minutes at 70 ~ 100 ℃ with 3 ~ 5M hydrochloric acid, which is an impurity while neutralizing because it uses an alkaline component such as NaOH This is to remove ash and is most effective at the concentration, temperature and time. Here, if the concentration of hydrochloric acid is high, hydrochloric acid concentration and treatment time can be adjusted in the above range by shortening the treatment time.

In addition, the water washing in the step (S4) is to be carried out to pH 7, the drying is preferably carried out for 10 to 15 hours at a temperature of 80 ~ 110 ℃ in the dryer, pH7 in the above temperature and time range is well as described above Do it. If the temperature is low, drying is not sufficient, and if the temperature is high, there is a risk of burning.

The present invention also provides activated carbon for a capacitor produced by the above method.

The present invention also provides an electric double layer capacitor using the above-mentioned activated carbon for the capacitor as the anode electrode and the cathode electrode, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFePO ₄ , which is a component based on the activated carbon as the anode electrode. _, Using at least one selected from Li ₂ Mn ₃ NiO ₈ _{, which is a} binary system, and LiNi _0.5 Mn _0.2 Co _0.3 O ₂ , which is a ternary system, and using solute TEABF ₄ (Tetraethyl ammonium tetrafluoroborate) as an electrolyte in 1M Concentration dissolved and mixed solution of at least one selected from ethylene carbonate (EC), ethyl-methyl carbonate (EMC), dimethyl carbonate (DMC) in which LiPF ₆ salt is dissolved, and the binder is PTFE (Polytetrafluoroethylene), It provides hybrid capacitors using at least one selected from BS (Butadien styrene) and PVDF (Poly vinylidene fluoride), and at least one of Super-P and Acetylene Black as the conductive material for the electrode.

Activated carbon produced by the method of chemically activated using NaOH of the present invention has a high specific surface area (1500 ~ 3000 ㎡ / g) and 1.5 ~ 5nm size mesopores using activated carbon using low-cost coconut shell charcoal It has the effect of manufacturing. In the present invention, the activated carbon prepared as mesopores, which can reduce the diffusion resistance of the charge, is used as the anode electrode, and the metal oxide electrode containing Li salt is used as the cathode electrode, and the conductive agent, the binder and the electrolyte are changed while changing the hybrid. By manufacturing a capacitor, it is possible to realize high power and high capacity of an energy storage device.

1 is a NaOH chemical process chart of the present invention.
2 is a process chart for manufacturing a hybrid capacitor of the present invention.
3 is a conceptual diagram of a hybrid capacitor of the present invention.
Figure 4 is a graph showing the size of activated carbon mesopores according to the weight ratio and Ar flow rate of NaOH / coconut shell charcoal of the present invention.
5 is a graph showing the size of the activated carbon specific surface area according to the weight ratio and Ar flow rate of NaOH / coconut shell charcoal of the present invention.
Figure 6 is a graph showing an SEM photograph of the activated carbon electrode and metal oxide electrode prepared by the present invention.

The present invention is characterized in that the activated carbon having a high specific surface area and mesopores using a chemical activation method of NaOH with coconut shell charcoal as described above is used as a high capacity hybrid capacitor electrode by producing an anode electrode. Hereinafter, the present invention will be described in more detail with reference to the following examples. These examples are only for illustrating the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples in accordance with the gist of the present invention. .

Example 1 Preparation of Activated Carbon from Activated Chemical NaOH from Coconut Charcoal

In this embodiment, two low-cost palm charcoal having different sizes and ash compositions were used. Each ash contained was 2-4%, and when applying the chemical activation method, the particle size analysis result of the used charcoal was composed. There was no significant difference in the structure of activated carbon pores produced when the particles had a particle size of 1 mm or less and a particle size distribution of 1-5 mm. NaOH was used to prepare activated carbon having a large specific surface area and advanced mesopores as chemically activated chemicals. In addition, activated carbon was prepared by the method of mixing the activated chemical with the palm charcoal in a water-soluble state by a method of mixing the activated chemical with the palm charcoal, and then adhering the activated chemical with the palm charcoal.

2-8g of coconut shell charcoal was prepared and the ratio of NaOH was determined based on this. Coconut charcoal was changed into 0.2-10 by weight with NaOH, an active chemical, respectively. Ar gas, which is an inert gas, was used for heat treatment of the coconut shell charcoal, and the reaction atmosphere was controlled by injecting the Ar flow rate while changing the Ar flow rate to 100 to 600 Pa / min. The activation temperature was set at 750 ° C., and the heat treatment condition was raised to 5 ° C./min, reached for about 100 minutes, and then slowly cooled.

After the heat treatment, the prepared activated carbon was treated with 3 ~ 5M HCl for 50 minutes at 80 ° C. to remove impurities, washed sufficiently until pH 7, and dried in an oven set at 80 ° C. to 110 ° C. for about 12 hours. At this time, impurities were removed while appropriately adjusting the hydrochloric acid concentration and treatment time. According to the present invention as described above, the activated carbon prepared by using the activated chemical NaOH, remove impurities with hydrochloric acid, and then the activated carbon prepared using BET, SEM and EDS surface characteristics, specific surface area of the activated carbon, pore volume The mean pore size, mesopore fraction, and surface composition were investigated. Figure 1 shows a process chart produced by the chemical activation method using such NaOH.

2 and 3 show the physical properties of the activated carbon produced by the method of producing activated carbon of the present invention, and shows the specific surface area and average pore size according to the activated chemical NaOH weight ratio and the flow rate of Ar gas to palm charcoal.

In another embodiment according to the impregnation method, determine the number of moles, and then add the amount of activated NaOH chemical per 10 ml of water, put the coconut shell charcoal in a weight ratio, and sufficiently stirred for 1 to 2 hours, and then at 100 ℃ In an inert gas atmosphere or air atmosphere, a sufficient drying time for 10 to 30 hours to produce a coconut shell impregnated with a chemical. Activated charcoal is prepared by putting the prepared coconut shell into a tube furnace and activating it. The physical properties of activated carbon produced by each method were NaOH / palm charcoal = 4/1, and the specific surface area of the impregnated activated carbon prepared in the liquid state was 1537 g / m 2 when the inert gas Ar flow rate was 200 mW / min. As a result, as shown in FIG. 2 prepared by mixing the activated carbon and NaOH physically in the solid state, it was found that the activation was reduced. It is shown that activated carbon produced by the physical method has a larger specific surface area and well developed pores than activated carbon produced by the impregnation method in the aqueous state.

Example 2 Hybrid Capacitor Preparation Using Activated Carbon

4 and 5 is a conceptual diagram showing the electrochemical difference between the electric double layer capacitor and the hybrid capacitor and the manufacturing process of the hybrid capacitor electrode using the activated carbon produced by the present invention. In an embodiment, an electric double layer capacitor having an activated carbon prepared using an anode and a cathode electrode, and in another embodiment, an anode prepared an asymmetric hybrid capacitor using an activated carbon electrode prepared by chemical activation and a Li salt metal oxide electrode as a cathode. High capacity, high power energy storage device was manufactured.

The anode electrode material was mixed in the ratio of activated carbon: conductive material: binder = X: Y: Z to make a slurry. X = 70-80 weight%, Y = 15-20 weight%, Z = 5-10 weight%, X + Y + Z = 100 weight% here. In addition, the cathode electrode material was mixed in the ratio of Li salt metal oxide: conductive material: binder = X: Y: Z to form a slurry, where X = 80 to 90% by weight, Y = 5 to 15% by weight, and Z = 3- 7 weight% and X + Y + Z = 100 weight%. The slurry thus prepared was uniformly mixed at a speed of 300 rpm and then coated on the aluminum foil used as the current collector. The coated electrode is dried at 100 ° C. in an oven, and then pressed to have a constant thickness (100 μm) using a 150 ° C. and 200 kgf / cm 2 hot press. After cutting the crimped electrode to a size of 2 ㅧ 2㎠ and dried for 24 hours in a vacuum dryer at 130 ℃ with a separator prepared in the size of 3㎠3㎠, a unit cell was prepared. All the processes of unit cell preparation were carried out in a glove box under argon atmosphere to prevent the organic electrolyte from contacting with moisture in the air.

In the embodiment, in the case of the electric double layer capacitor in which both the anode and the cathode electrode are made of the prepared activated carbon, the charging capacity according to the activation chemical NaOH weight ratio and the flow rate of Ar gas is shown in Table 1. The synthesized activated carbon yielded a sharp decrease in the yield of activated carbon below 50% when the NaOH / palm charcoal weight ratio was 6/1 or more.

As shown in Table 1 above, the activated carbon electrode showed a charging capacity of 0.3 to 0.5F / cm 2 when the aluminum electrode was 20 μm according to the Ar flow rate, which has a specific surface area of 2200 m ² / g. When commercially available activated carbon fiber product, MSP-20 (Kansai Coke & Chem) of Japan, was used as the electric double layer electrode, it showed similar or superior characteristics to the charging capacity of 0.37F / cm 2. Therefore, in the present invention, it is possible to produce activated carbon having a specific surface area larger than that of the product, and the technology is very low in price and competitive in price. In addition, when measured based on the weight of the activated carbon electrode, considering that the world's highest charge capacity in the electric double layer and hybrid capacitor is about 100 ~ 200F / g, the capacitor using activated carbon manufactured by activating NaOH from coconut charcoal It can be seen that the electrode has a very good charging capacity.

In another embodiment, to produce a high capacity and high power energy storage device, as shown in Table 2, the activated carbon and cathode electrode prepared in the present invention as an anode electrode, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO based on a salt component _2, LiFePO _4, the binary system of Li ₂ Mn ₃ NiO ₈ and Ternary of LiNi _0.5 Mn _0.2 Co _0.3 O ₂ by using the metal oxide electrode materials, conductive material, electrochemical properties of the hybrid capacitor, while a composition change and the electrolyte and the binder type Was investigated. The FE-SEM image measured to determine the crystal shape of the activated carbon fiber and the metal oxide material is shown in FIG. 6. The crystal shape of the active material is closely related to the capacitor performance. LiMn ₂ O ₄ has an average particle size of 20 μm and a LiCoO ₂ particle size of 50 μm with a relatively uniform particle size. LiFePO ₄ has a particle size of 10-50 μm and a particle size of LiNi _0.5 Mn _0.2 Co _0.3 O _{2 has} a particle size of 20 μm. The particle size was uniform at about 100 μm. Looking at the particle size of activated carbon fiber, the larger the particle size was, the larger the particle distribution was. Table 3 shows examples and results of metal oxides, electrolytes, and binders of the cathodes with respect to the charges of the hybrid capacitors manufactured as described above.

Claims

A method for producing activated carbon for capacitors, which is intended for use as a capacitor electrode material having a charging capacity of 0.3 to 1.0 F / cm 2, and has a high specific surface area of 1500 to 3000 m 2 / g and mesopores of 1.5 to 5 mm.
Grinding and mixing sodium hydroxide (NaOH) and coconut shell charcoal in a weight ratio of 0.2 to 10: 1 (S1);
Activating the mixture at a temperature of 700 to 900 ° C. in a tube furnace to prepare activated carbon (S2);
Removing impurities of the activated carbon prepared in step S2 (S3); And,
A method of manufacturing activated carbon for a capacitor comprising a step (S4) of washing and drying after the step (S3), wherein the coconut shell charcoal in the step (S1) is a powder having a size of 0.6 mm or less or granularity of 1 to 5 mm. , The activation in the step (S2) is carried out while adjusting the reaction atmosphere by injecting argon and / or nitrogen gas at a flow rate of 100 ~ 1000㏄ / min, the activation is heated to 0.1 ~ 10 ℃ / min activation temperature After cooling for 30 to 180 minutes in a slow cooling, the neutralization and impurity removal in the step (S3) is to process 20 to 60 minutes at 70 ~ 100 ℃ with 3 ~ 5M hydrochloric acid, washing with water in the step (S4) Is performed up to pH 7, wherein the drying is performed for 10 to 15 hours at a temperature of 80 ~ 110 ℃ in a dryer.

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