JPH06103979A - Manufacture of conductive binding agent and application top various kinds of batteries - Google Patents

Abstract

PURPOSE:To provide an electrode for a cell and a battery, which is excellent in charge/discharge performance by uniformly dispersing fluorine resin and carbon material in solution, removing the solution so as to allow composite material to be produced thereafter, and thereby binding electrode active material using the aforesaid composite material as binding agent. CONSTITUTION:Fluorine resin powder and carbon material such as Ketien black whose grain size is less than 0.1mum are dispersed in the class of alcohol such as methanol and the like and the class of halide alkyl such as acetonitrile and the like, are mechanically stirred and dispersed uniformly so as to be formed into composite material, so that the solution is removed thereafter. The composite material thus produced has two properties of binding performance and conductivity, so that electrode active material can be bound without lowering conductivity. The carbon material is high in oxygen over potential, a battery with nickel oxide electrodes can sufficiently be charged with less self-discharge and with performance scarcely deteriorated. The carbon material is therefore effective in particular as the binding material for the positive electrode when aqueous solution is used as electrolytic solution.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive binder used for producing a positive electrode and negative electrode mixture for batteries. 2. Description of the Prior Art Alkaline storage batteries having nickel oxide as a positive electrode and a hydrogen storage alloy as a negative electrode and lithium storage batteries having a metal oxide or a chalcogen compound as a positive electrode active material and metal lithium as a negative electrode store hydrogen. It is well known to separately mix a binder such as a fluororesin and a conductive agent such as a carbon material when manufacturing a negative electrode mixture containing an alloy or a positive electrode mixture containing a metal oxide or a chalcogen compound. In alkaline dry batteries and zinc chloride type dry batteries, it is well known that a conductive material such as a carbon material is added to the manganese dioxide positive electrode mixture. Japanese Patent Publication No. 58-163157 proposes a method of fixing the hydrogen storage alloy powder with a binder such as a fluorine resin. However, since the fluorine resin is an insulator, the conductivity of the hydrogen storage electrode is impaired, and the current in this electrode becomes non-uniform, so that the charge and discharge characteristics of the battery deteriorate. . This problem is also common to battery active materials that are semiconductors. In order to solve this problem, it is possible to add a large amount of metal powder such as nickel, but this method not only lowers the discharge capacity per weight, but also the electrode active material, metal powder and polytetrafluorocarbon. Since the ethylene resins have different densities, it is difficult to uniformly disperse the three materials, the binding property of the electrode active material is deteriorated, and the problem that the electrode active material falls off from the electrode with the increase of charge / discharge cycles occurs. Not only that, but the number of materials increases, which leads to an increase in work cost. In order to solve the above problems, the present invention intends to impart conductivity to the binder in advance. That is, in the composite material composed of the fluorocarbon resin and the carbon material, the fluorocarbon resin is uniformly dispersed in the carbon material and has two properties, that is, binding property and conductivity. Without any damage, there is no problem that the discharge characteristics or charge / discharge characteristics of the battery deteriorate. The above-mentioned binder is a composite material in which a fluorocarbon resin such as polyfluoroethylene is uniformly dispersed in a carbon material such as acetylene black, graphite, and Ketchin black, and the specific gravity of the carbon material is low. It is a material that solves both the problem and the problem that fluorine resin is an insulator. The composite material of the present invention can bind an electrode active material without lowering conductivity. The acetylene black used for producing this conductive binder has a surface area of 20-300 m.
² / g, a structure in which carbon particles having a particle size of 0.1 μm or less are connected like a grape, and an active material having a wide range of particle sizes (0.1-
50 μm) to give conductivity. Also,
Carbon materials such as acetylene black used here have a high oxygen overvoltage and can sufficiently charge nickel oxide electrodes, and have little self-discharge, and as a binder for the positive electrode when an aqueous solution is used as the electrolyte with almost no deterioration in its performance. Especially effective. Embodiments of the present invention will be described below. Example 1 1 g of polyfluoroethylene was added to 50-400
Disperse well in ml of methanol using a homogenizer. 0.5-4 g of Ketchin black in this dispersion
Is added and the mixed dispersion is stirred using a homogenizer. The dispersion is filtered and dried at a temperature below the melting point to obtain a composite material composed of a fluorine resin and a carbon material. Example 2 An aqueous dispersion containing 1 g of polyfluoroethylene and 100-300 ml of distilled water were placed in a beaker and mixed using a homogenizer. Acetylene black 20
0-1000 mg is added, and 5-30 ml of methanol is added to the acetylene black floating on the surface of the aqueous solution to disperse the acetylene black in the aqueous solution. The operation of adding acetylene black is repeated 3 times. Finally, 10-50 ml of methanol is added to make sufficient dispersion in the mixed solution of acetylene black. The mixture is filtered after methanol:
Wash with a mixed solution of water = 2: 1 to 1: 4 to remove impurities initially contained in the polyfluoroethylene aqueous dispersion. A composite material composed of a fluorine resin and a carbon material is obtained by drying below the melting point. Example 3 An organic solvent dispersion containing 1 g of polyfluoroethylene was sufficiently dispersed in 50-400 ml of methanol using a homogenizer. 0.5-2 g of Ketchin black was added to this dispersion, and the mixed dispersion was stirred using a homogenizer. The dispersion is filtered and washed with methanol. A composite material composed of a fluorine resin and a carbon material is obtained by drying below the melting point. [Application Example 1] 20 m per 100 mg of Ni (OH) ₂
g of composite material are mixed. 0.1-4 ton / cm of the mixture on a metal screen such as stainless steel or nickel.
² is pressure bonded to produce a nickel positive electrode. The hydrogen storage negative electrode was produced by mixing 180 mg and 30 mg of a hydrogen alloy composite material. The battery performance test was performed by the device shown in FIG. The apparatus in FIG. 1 has a nickel oxide electrode 1 in the center, a hydrogen storage negative electrode 2 on both sides thereof, and Hg / HgO / 8M-KOH.
The structure is such that the conducting wire 3 to the reference electrode is provided in the cell. The electrolytic solution is 8M-KOH containing 0.1M-LiOH. Charging current 2mA for 17 hours, discharging current 4
FIG. 2 shows the result when charging and discharging were repeated up to a positive electrode potential of 0.2 V at mA. APPLICATION EXAMPLE 2 20 mg of composite material is mixed with 100 mg of hydrogen alloy. The mixture is pressed onto a metal screen such as stainless steel or nickel at 0.1-4 ton / cm ² . The same electrolytic solution and electrolytic cell as in Example 1 are used. However, nickel oxide electrodes are arranged on both sides with the hydrogen storage negative electrode as the center. As the nickel oxide electrode, a positive electrode of a commercially available NiCd battery is used. Charging current is 1mA (10mA / g) 24
Charge for hours. The discharge was performed at 1, 6, 15 and 30 mA. The result is shown in FIG. As described above, by using the binder of the present invention, it is possible to provide a battery and a storage battery electrode having excellent discharge or charge / discharge characteristics. [0012]

BRIEF DESCRIPTION OF THE DRAWINGS [FIG. 1] Configuration of battery used for test [Explanation of reference numerals] 1 is nickel oxide electrode 2 is hydrogen storage electrode 3 is lead wire to reference electrode 4 is glass container 5 is rubber stopper [ Fig. 2 Charge / discharge behavior of nickel oxide electrode. Fig. 3 Relationship between discharge speed and discharge capacity of hydrogen storage electrode.

Claims (1)

[Claims] 1. Fluorine resin powder and Ketjin black or acetylene black having a particle size of 0.1 μm or less are dispersed in alcohols such as methanol and ethanol, or alkyl halides such as acetonitrile and dichloromethane, and mechanically stirred into a carbon material. After the fluorine resin is uniformly dispersed and complexed, the solvent is removed. Alternatively, a method of heating at a temperature below the melting point of the fluororesin to obtain a composite material composed of the fluororesin and the carbon material Water-methanol mixed solvent (volume ratio 4: 1 to 1: 1)
Kickback black having a particle size of the powder and the following 0.1 [mu] m 2 range) fluorine resin in or after dispersed uniformly compounding the fluororesin to a carbon material by mechanical agitation acetylene black is dispersed, and the solvent To remove. Alternatively, a method of obtaining a composite material composed of a fluorocarbon resin and a carbon material by heating below the melting point of the fluorocarbon resin 3. At this time, the hydrophilicity and water repellency of the composite material can be improved by adding a polyoxyethylene-based neutral surfactant such as Triton 100, an anionic surfactant such as dodecylbenzenesulfonic acid, and a cationic surfactant such as Zephyramine. Method of controlling