JPS59134563A - Production process of collector for electrode - Google Patents

Abstract

PURPOSE:To obtain the captioned collector which is excellent in ruggedness, for adhering to active material by thermal-spraying metal, alloy, or compound thereof upon a sheet-like substrate. CONSTITUTION:A polypropylene sheet is used as a sheet-like substrate 1. With regard to the quality, the material for use herein may be the other one such as polyvinyl chloride, polyester or the like, and also paper (pulp) may be used. Next, a plasma spraying process is used as thermal spraying. Powder made of 0.05wt% of calcium, 0.5wt% of tin, and the rest of lead alloy powder ranging 1-10mum in size whose almost principal ingredient is lead is used as said spraying particles. Resin sheet 1 provided with the obtained sprayed layer 2 is processed into a collector shape 3 for electrode. Heating is not always necessary for punch processing, but it is desired for expand processing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to improvements in current collectors for electrodes that can be widely used in electrochemical devices such as secondary batteries, secondary batteries, fuel cells, electrolytic electrodes, and sensors. It is.

Conventional configurations and their problems In electrochemical devices such as batteries, metal or alloy nets, perforated plates, expanded metal, cast grids, etc. are used for electrodes to collect current and maintain the porous shape. It's normal. Particularly recently, there has been a trend for all devices to be lighter, and the division of roles between current collection and reinforcement has been reconsidered.
A composite current collector was devised in which parts with excess or surplus current collecting capacity were replaced with plastic. However, when we actually manufacture a current collector made of a composite of resin and metal, we find that there are limits to the bonding of the metal and resin, and even with insert molding, for example, they will separate after long-term use, and the metal will separate from the resin. It was recognized that the wires could become loose and cause problems such as wire breakage.

OBJECTS OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and obtain a lightweight current collector in which the metal and resin portions are kept in close contact with each other for a long period of time, thereby making the best use of each other's strengths. The present invention also includes: By making the metal part responsible for the current collection part porous, it is possible to create a structure with excellent unevenness suitable for bonding with the active material, and in the end, this metal also has the ability to maintain the structure without using a resin part. The purpose of the present invention is to obtain a current collector that is effective even when the current collector is distributed to different departments.

Structure of the Invention The method of the present invention to achieve the above-mentioned object comprises the steps of thermally spraying a β group, an alloy, or a compound thereof on one or both sides of a sheet-like substrate, and machining the substrate on which the above-mentioned sprayed layer is formed into a porous shape. It is characterized by having a step of.

The advantage of using this thermal spraying method is that the metal layer is first impinged onto the original sheet in a molten state at high speed, so that it is sufficiently embedded in the resin or fiber sheet, and then the metal parts to be deposited by thermal spraying are firmly attached to the base. It is possible to combine with Therefore, there is little risk of peeling off no matter what processing is applied afterwards.

For thermal spraying, a thermospray method that sprays molten metal with flame can also be applied, but plasma spraying
Advantages include the ability to obtain high temperatures reaching up to 'C, the versatility of materials, the ability to adjust the velocity of particles regardless of the flame in the range of approximately several hundred m/sec4, and the ability to use a reducing atmosphere. There is.

When the sheet-like substrate is to be removed in the final processing, a material that is easy to remove may be used. However, in order to use it as a structural material for reinforcement as mentioned above, it is necessary to use electrolyte-resistant fibers and cloth.
Plastics (synthetic resins) can be used. In particular, when thermoplastic materials such as polypropylene, polyethylene, polyester, polyacrylonitrile, and their derivatives are used, the flexibility of processing can be greatly increased by selecting an appropriate temperature (above the softening point of the resin used) at the time of processing. can be improved. Furthermore, if the desired shape is prepared at high temperature and then cooled, any shape can be easily obtained. For further weight reduction, it is recommended to use woven fabric or low-foam resin.

When machining is then performed, the effect of the present invention can be most widely utilized by forming a reticulate shape by punching.

In this case, it can be applied even if the merged portion with the sheet is somewhat weak like a thermospray.

On the other hand, if you wish to perform extended band processing, it is better to choose a method with a high thermal spraying temperature, such as plasma spraying.

The sprayed area thus obtained is highly uneven, and depending on the adjustment, an unlimited number of layers can be built up.

On the other hand, if the sprayed material is in the form of an oxide, a halide, or a salt such as nitrate, and the spraying atmosphere is air, the sprayed layer may remain in the form of an oxide. In that case, it may be done either before or after processing, but it is better to partially reduce it so that it is electrically conductive to the terminal portion of the electrode plate. Although chemical reduction may be used as the reduction method, the simplest method at room temperature is to press a conductor against a part of the sprayed layer and perform electrolytic reduction.

DESCRIPTION OF EMBODIMENTS The present invention will now be described in detail. Note that the material to be used must of course be selected depending on the liquid properties of the system used, but since the characteristics of the present invention can be explained using an example, a current collector for an electrode for a lead-acid battery will be shown here.

A long polypropylene sheet with a thickness of 1 mm and a width of 120 mm was used as a sheet-like base material without being twisted. Other materials such as polyvinyl chloride and polyester may be used as the material, and paper (pulp) may also be used.

Next, for the thermal spraying, plasma spraying was used for the reasons mentioned above. The sprayed grains contain 0.055% calcium by weight, 0.5% tin by weight, and 1 of a lead alloy in which the remainder is mostly lead.
A powder with a particle size distribution of ~10 μm was used.

An advantage of using the plasma spray method is that any material or composition can be selected for the sprayed particles, and the broken sprayed layer can be layered with different types of alloys. Of course, pure metal such as pure lead can be selected as the sprayed particles, but if small metal compounds such as lead oxide or lead halide are used, in an oxidizing atmosphere, the sprayed layer will form metal particles with a large amount of oxide on the surface. form.

Here, the plasma layer is 100 to 200 m/sec
Thermal spraying was carried out at a speed of about 0.5 mm to obtain a sprayed layer with a thickness of about 0.5 mm.

The sprayed layer here showed considerable electrical conductivity, but if it is not electrically conductive under conditions where there are many oxides, it can be made conductive by pressure-welding a lead plate or the like and cathodically polarizing it in dilute sulfuric acid.

The resin sheet provided with the obtained thermal sprayed layer is shown in FIG. 1
2 is a sheet-like base material, and 2 is a thermally sprayed layer having a rough surface on which fine particles are piled up.

This entire sheet is then processed into the shape of a current collector for an electrode. FIG. 2 shows the grid 3 punched out with a die. Here, the sheet was kept at 130 to 150°C, which is the softening range of polypropylene, and the punching operation was performed. Heating is not necessarily necessary in punching, but heating is desirable in expanding. This is because peeling may occur between the sheet material and the sprayed layer during processing. After processing, hold it in the specified mold and heat it for 130~1ts.
If the temperature is raised to 0''C and then cooled, a current collector that does not lose its shape can be obtained.

Finally, using the current collector obtained above, apply a paste mainly composed of lead powder and dilute sulfuric acid to it, dry it, and
Electrodes with an area of 15 mm were made. A battery in which this was used for the positive and negative electrodes was designated as A1, a battery in which only the positive electrode was used, B1 was a battery in which a conventional cast grid was used for the other electrodes, and C was the reverse case.Batteries each having a nominal capacity of 30 Ah were constructed. As a comparative example, a battery using conventional cast grids for both electrodes is designated as D.

Here, the weight of the lattice alloy for the positive electrode of the present invention is reduced by % of the conventional method, and for the negative electrode, it is reduced to about % of the conventional method.

FIG. 3 shows examples of discharge capacity when the battery having the above configuration is discharged at various discharge rates. As shown here, in the region of low rate discharge, even Battery A, which has a reduced amount of lead in both the positive and negative electrodes, is comparable to the comparative example. When the ratio is further increased, the capacity decreases slightly, but this is not much different between Battery C, in which the present invention is applied only to the negative electrode, and Battery B, in which the present invention is applied only to the positive electrode. This shows that the amount of lead in the positive electrode mainly contributes to the conductivity of the grid, and from a different perspective, it also shows that there is still room for reduction on the negative electrode side. There is.

In actual manufacturing, it is industrially disadvantageous to obtain a grid with a thickness of 0.5 points by casting, but according to the present invention, the weight can be easily reduced as described above.

In addition, the current collector having a structure with a highly uneven surface obtained by the present invention has excellent binding strength with the active material porous body, and even in a drop test after applying and drying the paste, many deposits were observed on the grid. It was found that it is good for lifespan.

Effects of the Invention As described above, according to the present invention, it is possible to obtain a current collector that is lightweight and provides an electrode with excellent characteristics.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a partial cross section of a sheet-like base material provided with a sprayed layer in an example of the present invention, and FIG. 2 is a lattice-like current collector obtained by punching the above-mentioned base material. The perspective view and FIG. 3 show a comparison of discharge capacities at various discharge rates of lead batteries using various current collectors. 1...Sheet-like base material, 2...Thermal spray layer,
3...Punched grid current collector.

Claims (1)

[Claims] (1) Manufacture of a current collector for an electrode, which is characterized by thermally spraying a metal, alloy, or a compound thereof on one or both sides of a chemically stable and lightweight substrate, and then machining the substrate to make it p-porous. Law. (Kon) A method for manufacturing an electrode current collector according to claim 1, wherein the thermal spraying method is a plasma spraying method. A method for producing a current collector for an electrode according to claim 1 or 2. (→Claim 1, wherein the substrate is an electrolyte-resistant and oxidation-resistant nonwoven fabric or a low-foam resin sheet. A method for producing a current collector for an electrode according to claim 2. (4. The current collector for an electrode according to claim 1, wherein the substrate is thermoplastic and the machining is performed at a temperature equal to or higher than the softening temperature of the substrate. (@ The method for producing a current collector M for an electrode according to claim 1, which includes a step of reducing a part of the sprayed layer at an arbitrary stage after the spraying step.