JPS5851669B2 - Manufacturing method of battery electrode substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Generally, the electrodes of batteries used for various portable devices, mobile devices, stationary devices, etc. can be roughly divided into paste type, powder press type, clad type, pocket type, and sintered type.

Among these, the paste type is best known for lead batteries, in which active material powder, mainly lead powder, is kneaded with water and sulfuric acid to form a paste, and this is placed on a lattice mainly made of lead. Obtained by painting.

Recently, alkaline batteries have also been coated with a paste made from nickel hydroxide or cadmium oxide, using a binder, on screens, perforated plates, expanded metal, etc., which are called non-sintered batteries. It is used as an electrode.

However, with current technology, this type of electrode has a problem with the lifespan of batteries that use a sufficient amount of electrolyte, so it is mainly used in sealed batteries where the amount of electrolyte is regulated.

The pressurized type is particularly used for manganese dioxide electrodes, mercury oxide electrodes, silver oxide electrodes, etc. of primary batteries, and is made by press-molding electrode materials mainly using active material powder.

These paste type and pressurized type are both easy to manufacture and low cost, and have relatively excellent battery characteristics, so they are the mainstream methods for manufacturing electrodes.

However, if used as a secondary battery (aside from a primary battery) and repeatedly charged and discharged, there is a problem in durability, and the active material is likely to fall off and the electrodes may swell.

In addition, clad lead-acid batteries and pocket alkaline batteries solve the problems of paste-type batteries and have a longer lifespan, but on the other hand, the voltage drop at high discharge is relatively large. , is mainly used for low discharge applications.

Since the sintered type uses a sintered base, significant improvements have been observed in both battery characteristics and lifespan.

However, since the manufacturing method of the sintered body and the process of filling the active material are complicated, it is quite disadvantageous in terms of cost.

Therefore, in recent years, many attempts have been made to bring the performance closer to that of the sintered type and to reduce the cost.

The present invention provides one of the effective methods for manufacturing an electrode substrate.

That is, electrolyte-resistant conductive powder is contained in a porous body made of fibers such as woven fabrics, non-woven fabrics, or felt made of natural or synthetic resin, and then the entire body is plated with metal to obtain a fibrous porous metal body. , this is used as an electrode base.

Generally, woven fabrics, non-woven fabrics, felts, etc. have sufficient strength by themselves, so the porous bodies obtained by applying metal plating to them can be made to any desired thickness, have high porosity, and have high strength. It is superior to conventional sintered substrates, porous materials obtained by gathering and sintering metal fibers, and foamed metals.

For example, even when wound into a spiral shape for use in cylindrical batteries, which are currently widely used, cracks and breakage are extremely rare compared to other electrodes.

In addition, since the fibers are plated with metal, even if the amount of metal is small, the fibers are entangled with each other, so they have advantages such as excellent conductivity.

However, since it is a metal porous body obtained by using woven fabric, non-woven fabric, felt, etc. as the core of the metal layer, the pores are square or rectangular rather than spherical as in sintered or foamed metal. .

Since the active material powder is generally spherical, there is a slight problem with the holding power of the filled active material.

In addition, since the surface of fibers is generally smooth, those plated with it are also smooth and have almost no irregularities compared to sintered bodies obtained from powder, and from this point of view, the adhesion with active materials is also improved. Points and improvements are desired.

That is, these are related to uniform filling and lifetime of the active material.

Therefore, the present invention provides an effective means for solving the above-mentioned problems of an electrode base obtained by metal plating a porous body made of fibers.

In other words, a porous body made of fibers contains conductive powder that is resistant to electrolyte, and the entire body is plated with metal, and the conductive powder is interposed before the metal plating. The fibrous metal porous material obtained after metal plating and the conductive powder are completely integrated, and due to the presence of the conductive powder, the pores formed by the fibers change from square or rectangular to spherical, and the surface condition is complex. In order to
The ability to retain active materials is improved.

Therefore, the uniform filling property of the active material is improved and the life span is also improved.

In addition, as a method for interposing a conductive powder having electrolyte resistance into a porous body, this powder is preferably dispersed in a solvent containing a binder, and the porous body is impregnated with this, followed by drying. is the most effective.

In addition, integrating powder only into the surface layer of the porous material is effective in improving the retention of the active material, so in this case, a dispersion of the powder and binder may be sprayed onto the surface of the porous material. A method of adhering the material to a surface and then drying it is also effective.

Alternatively, the conductive powder may be dispersed in a dispersion medium such as water or alcohol, impregnated into a porous body, and then dried.

When performing metal plating after integrating the conductive powder and the porous body, since the conductive powder is interposed, it is possible to plate the entire body even if electrolytic plating is performed immediately. Considering the efficiency of initial plating, it is preferable to first perform electroless plating and then perform electrolytic plating.

Next, examples of the present invention will be described.

First, the thickness is about 0.8mm, the average pore diameter is 150μ, and the porosity is about 9.
A felt made of 0% polypropylene is prepared.

10 parts by weight of carbonyl nickel powder was added to 50 parts by weight of a 1% by weight aqueous solution of carboxymethylcellulose, and the felt was immersed in this solution with sufficient stirring.

Thereafter, the felt was taken out of the liquid and dried at 80° C. for 1 hour.

Next, electroless plating and electrolytic plating of nickel are performed to form a nickel plating layer of about 20 μm, thereby obtaining a fibrous nickel porous body having a polypropylene fiber as a core material.

The porosity in this case was about 86%.

After spot welding a lead plate to this electrode base,
The active material was filled by impregnating with a nickel nitrate solution and electrolyzing in a caustic potassium aqueous solution, so-called impregnation-electrolysis five times.

A AA-type sealed battery was manufactured using the electrode obtained in this way and a known cadmium electrode, and this battery was designated as A.For comparison, this battery differs from A in that it does not contain carbonyl nickel powder. Otherwise, the battery was obtained using the same manufacturing method, and a known sintered substrate with a porosity of 82% was used.
A battery using a nickel electrode obtained by repeating filling 8 times using the impregnation-electrolysis method was designated as C, and the performance of each battery was compared.

In Figure 1, 20 batteries of A to C are prepared and heated at 25°C.
The figure shows an average discharge curve when the batteries were discharged at 300 mA in an atmosphere of 100 mA, and the capacity was almost the same for all voltages A=B>C1.

Figure 2 shows the average discharge characteristics when discharging at 3.5A in an atmosphere at 45°C.The trend in capacity is almost the same as in Figure 1, and the voltage changes to A and C. In comparison, B is only slightly lower.

Finally, we conducted a life test under the conditions of 5 hour rate charging and 1 hour rate discharging, and found that A maintained 77% capacity, B 69% capacity, and C 78% capacity after 1000 cycles. It was observed that the decrease in capacity was considerably smaller.

From the above results, the electrode substrate obtained by the manufacturing method of the present invention has a larger porosity than a sintered body, which generally has a porosity of about 78 to 83%, so the number of times the active material is filled can be reduced. Moreover, it has the advantage that it is easy to increase the amount of filling, and it has become clear that it is almost as good as the sintering type in terms of voltage and life.

In addition, the high porosity means that the content of metal as an active material holder may be small, and it is also advantageous in terms of cost since it does not require a core material such as a screen unlike sintered bodies. be.

Furthermore, in the above embodiments, felt was used as the porous body made of fibers, but woven or non-woven fabrics may also be used.

In addition to the polypropylene shown in the examples, as the material, ordinary synthetic resins such as polyethylene, polyvinyl chloride, vinyl chloride-acrylonitrile copolymer, etc., and natural fibers such as cellulose acetalized products can be used.

Further, as the conductive powder, nickel powder was used in the above embodiments, but iron, stainless steel powder, carbon, graphite powder, etc. may also be used.

As the binder, in addition to hydrophilic substances such as carboxymethyl cellulose and polyvinyl alcohol, common binders such as fluorocarbon resin, polystyrene, and polyvinyl chloride can be used.

Although a nickel electrode was described in detail in the above embodiment, a cadmium electrode can be manufactured in the same manner by filling with cadmium oxide, cadmium hydroxide, etc., and the same effect can be obtained.

As for the filling method, in addition to the filling method involving conversion into an active material as shown in the examples for both the nickel electrode and the cadmium electrode, a paste method for directly filling the active material can also be adopted.

As described above, according to the present invention, a porous body composed of fibers contains electroconductive powder having resistance to electrolyte, and is then coated with metal, which is a simple process that achieves excellent quality and cost. A battery electrode substrate can be obtained.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing a comparison of discharge characteristics of various batteries.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an electrode substrate for a battery, which comprises incorporating a conductive powder having electrolyte resistance into a porous body made of fibers, and then applying metal plating to the porous body. 2. The method for producing a battery electrode substrate according to claim 1, wherein the step of incorporating the conductive powder into the porous body comprises impregnating the porous body with a dispersion medium in which the conductive powder is dispersed. 3. The method for producing a battery electrode substrate according to claim 1, wherein the step of incorporating the conductive powder into the porous body comprises impregnating the porous body with a binder solution in which the conductive powder is dispersed. . 4. The battery electrode according to claim 1, wherein the step of incorporating the conductive powder into the porous body comprises applying a binder solution in which the conductive powder is dispersed to the surface of the porous body by spraying. Substrate manufacturing method. 5. The method of manufacturing a battery electrode substrate according to claim 1, wherein the metal plating step comprises first performing electroless plating and then performing electrolytic plating.