JPH0642375B2 - Metal-hydrogen alkaline battery - Google Patents

Description

The present invention relates to a metal-hydrogen alkaline storage battery including a positive electrode made of a metal oxide and a negative electrode made of a hydrogen storage alloy.

(B) Conventional technology Lead-acid batteries and nickel-cadmium batteries have been used as conventional storage batteries, but metal-hydrogen batteries have been attracting attention in recent years because they may be lighter and have higher capacity than these batteries. It started like this. Some metal-hydrogen batteries include a positive electrode made of a metal oxide such as nickel hydroxide and a negative electrode made of a hydrogen storage alloy capable of reversibly storing and releasing hydrogen. A hydrogen storage electrode composed of a certain metal hydride,
Generally, as proposed in Japanese Examined Patent Publication No. 58-46827, a method of forming a porous body by sintering a hydrogen storage alloy powder together with a conductive material powder, and using this as a hydrogen storage electrode, or JP As disclosed in Japanese Patent Laid-Open No. 53-103541, the hydrogen storage alloy powder and the conductive material powder are bonded by a binder to form a hydrogen storage electrode.

However, when the hydrogen storage alloy used for these electrodes is repeatedly charged and discharged in an alkaline electrolyte, it repeatedly expands and contracts by absorbing and releasing hydrogen,
Since the alloy lattice is deformed and pulverization progresses, the alloy powder is removed due to pulverization and the capacity is reduced, and
There is a problem that the mechanical strength and conductivity of the electrode are significantly deteriorated and it is difficult to maintain the battery performance for a long period of time.

(C) Problems to be Solved by the Invention The present invention suppresses the drop due to pulverization of the hydrogen storage alloy that occurs due to repeated charging and discharging, thereby deteriorating the battery capacity and the mechanical strength and conductivity of the electrode. It is intended to provide a metal-hydrogen alkaline storage battery that suppresses the deterioration of the property and maintains a high capacity over a long-term charge / discharge cycle.

(D) Means for Solving the Problems In order to solve the problems, the present invention forms a spiral electrode body with a separator interposed between a negative electrode and a positive electrode made of a hydrogen storage alloy, and the electrode body The mutual pressing force between the positive electrode and the negative electrode (hereinafter, referred to as “winding constituent pressure”) constituting the above is set to 1.0 to 5.0 kg / cm ² . Incidentally, the winding constituent pressure in the present invention represents the force of the action / reaction acting on both the positive electrode and the negative electrode constituting the electrode body by pressure, and for example, the pressure between the positive electrode or the negative electrode and the separator. It can be easily measured by winding with a pressure paper or a pressure sensor attached.

(E) Action The spirally wound electrode body with a winding composition pressure of 1.0 to 5.0 Kg / cm ² can be wound appropriately even when the hydrogen storage alloy of the negative electrode is pulverized by repeated charging and discharging. Since the hydrogen storage alloy is held by the constituent pressure to prevent the hydrogen storage alloy from falling off, and a sufficient amount of the electrolytic solution held in the electrode body can be secured, deterioration of the negative electrode capacity and deterioration of the mechanical strength and conductivity of the electrode can be suppressed.

(F) Example A nickel-hydrogen battery is a typical battery that uses a hydrogen storage alloy for the negative electrode and a metal oxide for the positive electrode. The present invention will be described below using such a battery.

LaNi ₅ , which has hydrogen storage capacity, is mechanically pulverized and
Polytetrafluoroethylene (PTFE) powder, in which the particles easily fiberize and plastically deform into aNi ₅ powder with a small shearing force, is added at 5% to the weight of LaNi ₅ powder, and water is added to uniformly knead the polytetrafluoroethylene (PTFE) powder. Fluoroethylene is made into fiber. This mixture of polytetrafluoroethylene made into fibers is rolled and then placed on both sides of a current collector to carry out pressure bonding to produce a hydrogen storage electrode.

Then, the hydrogen storage electrode thus produced was charged with a discharge capacity of 1.
A spiral electrode body was prepared by combining a known sintered nickel positive electrode of 5AH with a separator made of nylon, winding it at a winding pressure shown in the table below, and fixing the outermost periphery with tape to form a spiral electrode body. The body was inserted into a battery outer case, and then an alkaline electrolyte was injected and sealed to obtain nickel-hydrogen alkaline storage batteries A to G having a nominal capacity of 1.5 AH.

As shown in FIG. 3, the winding composition pressure of each battery shown in the table below is determined by connecting the positive electrode 1, the negative electrode 2 and the separator 3 to the pin 5 with the pressure sensitive paper 4 arranged between the negative electrode and the separator. It is a value separately obtained from the color change of the pressure-sensitive paper in the central part of the spiral cross section at that time while winding the electrode body around the pin 5 while pinching the electrode body with the roll 6. When the material and physical properties (thickness, hardness, elastic force) of the members forming the electrode body and the force for pinching the electrode body by the pin 5 and the roll 6 at the time of winding are the same, the values are almost the same. Each winding constituent pressure of the batteries A to G is obtained by variously changing the clamping pressure at the time of winding.

FIG. 1 is a cycle characteristic diagram of the above batteries A to G.
After charging 150% of the nominal capacity at 0 hour rate current, charging / discharging was performed under the cycle condition that the final voltage was 1.0 V and discharging at 5 hour rate current, and the initial capacity of batteries B to F is represented as 100. Further, FIG. 2 is a drawing showing the relationship between the cycle until the discharge capacity reaches 60% of the initial capacity of the batteries B to F and the winding constituent pressure of the electrode body. As is apparent from the drawing, the battery A with the smallest winding configuration pressure of the electrode body has a high initial capacity but the cycle deterioration is remarkable, and the battery G with the largest winding configuration pressure of the electrode body has a low initial capacity. I understand. On the other hand, the batteries B to F have high initial capacity and little cycle deterioration. To guess the reason for this,
When the battery was disassembled after the end of the cycle, the deformation of the negative electrode of battery A was most noticeable.
The initial capacity is high because the amount of retained electrolyte in the electrode body is large and the battery reaction proceeds smoothly because it is as low as g / cm ² , but as the charge-discharge cycle progresses, the hydrogen storage alloy in the negative electrode becomes finely pulverized and the electrode body It is considered that since the winding composition pressure of was low, the finely pulverized hydrogen storage alloy was falling off and the capacity was reduced rapidly. On the other hand, in Battery G, which has the highest winding pressure of the electrode body of 6 kg / cm ² , since the winding pressure is high, permeation of the electrolyte solution into the electrode body is poor and the amount of the electrolyte solution retained in the electrode body is small. The reaction surface area is limited, and the smooth battery reaction is significantly hindered due to a decrease in charging efficiency due to hydrogen gas generation and an increase in internal resistance due to gas accumulation.
Further, it is considered that as the charge / discharge cycle progresses, the charge shortage further progresses and the cycle life becomes shorter. Also,
The batteries B to F in which the winding composition pressure of the electrode body is in the range of 1.0 to 5.0 kg / cm ² are pulverized by the winding composition pressure of the electrode body even if the hydrogen storage alloy of the negative electrode is pulverized. The hydrogen storage alloy is retained by the electrode body and is prevented from falling off, so that deterioration of the negative electrode capacity and deterioration of the mechanical strength and electrical conductivity of the electrode are suppressed, and the winding composition pressure holds the electrolyte solution of the electrode body. Since the amount can be sufficiently secured, a smooth battery reaction is performed, and a high capacity can be maintained for a longer period.

(G) Effect of the Invention The metal-hydrogen alkaline storage battery of the present invention has a winding configuration pressure of 1.
Since it is equipped with a spiral electrode body of 0 to 5.0 Kg / cm ² , even if the hydrogen storage alloy of the negative electrode is pulverized by repeating charging and discharging, the hydrogen storage alloy pulverized by the winding pressure is applied to the electrode body. Since the electrode body is prevented from being retained and dropped, and the electrode body can retain a sufficient amount of electrolytic solution for the battery reaction, the battery performance can be maintained for a longer period of time.

[Brief description of drawings]

FIG. 1 is a cycle characteristic diagram, FIG. 2 is a graph showing the relationship between the winding constituent pressure of the electrode body and the cycle life of the battery, and FIG. 3 is the state of winding when measuring the winding constituent pressure with pressure-sensitive paper. It is a schematic perspective view showing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuzo Murakami 2-18 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Takanao Matsumoto 2-18, Keihan Hondori, Moriguchi City, Osaka Sanyo Denki Within the corporation

Claims (1)

[Claims] 1. A battery comprising an electrode body formed by winding a positive electrode made of a metal oxide and a negative electrode made of a hydrogen storage alloy with a separator interposed between the positive electrode and the positive electrode. The mutual pressing force with the negative electrode is 1.0 to 5.0 kg.
A metal-hydrogen-alkaline storage battery characterized by being / cm ² .