JPH03230480A - Alkali-zinc storage battery - Google Patents

Abstract

PURPOSE:To suppress a dendrite short circuit and a shape change and obtain the long-life cycle characteristic by filling carboxymethyl-cellulose in residual spaces of a liquid holding layer. CONSTITUTION:An electrode group constituted of a zinc electrode 2 mainly made of zinc oxide or metal zinc, a nickel electrode 1, a separator 4 inserted between both electrodes 1, 2, and a liquid holding layer 3 and an electrolyte absorbed and held by the electrode group and limited to the degree that no free liquid exists are provided. Carboxymethyl-cellulose is filled in the residual spaces of the liquid holding layer 3 at the ratio 15-70%. The electrolyte is uniformly held for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application The present invention relates to a sealed alkaline zinc storage battery used as a power source for boats, equipment, portable, stationary, and electric vehicles.

Prior art and its problems Alkaline zinc storage batteries have advantages such as high energy density, high output characteristics, and excellent economy and safety. However, due to the high solubility of zinc, zincate ions present in the electrolyte may precipitate on the negative electrode in a dendritic or sea-like form during charging, causing sheeting through the separator or causing shape changes. The cycle life was reduced due to factors such as a decrease in utilization rate due to chain gear.

In order to improve this drawback, an alkaline zinc storage battery has been proposed in which a multilayer separator having a limited amount of electrolyte is disposed between the zinc electrode and the positive electrode. In conventional alkaline zinc storage batteries, a polyamide-based, polyolefin-based, or hepta-rose nonwoven fabric is used as a liquid retaining layer in contact with the positive and negative electrodes. Furthermore, by disposing cellophane, porous P, P, membrane, etc. between the nonwoven fabrics, Vw-t due to puntophyte growth was significantly improved. However, because the electrolyte holding power of the nonwoven fabric in contact with the zinc electrode is insufficient, the electrolyte drips and the electrolyte distribution becomes uneven, resulting in uneven liquid resistance and charge/discharge cycle problems.
As the process continues, the shape of the zinc electrode changes, resulting in a disadvantage that a long cycle life cannot be achieved.

Therefore, proposals have been made to apply surfactants to improve the liquid retention ability. However, batteries using nonwoven fabrics containing surfactants show good characteristics at the beginning of the cycle, but as the cycle continues for a long time, the surfactant dissolves into the electrolyte or decomposes, causing the liquid retention to deteriorate. The force decreased, and as a result, it was not possible to maintain the electrolyte uniformly.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems.
The object of the present invention is to provide an alkaline zinc storage battery that maintains an electrolytic solution uniformly for a long period of time, suppresses dendophytosis and shade change, and has long-life cycle characteristics.

Structure of the Invention In order to achieve the above object, the present invention comprises an electrode group consisting of a zinc electrode whose main component is zinc oxide or metallic zinc, a nickel IV electrode, a separator and a liquid retaining layer interposed between these two electrodes, and In an alkaline zinc storage battery having an alkaline electrolyte that is absorbed and retained in the electrode group and is limited to such an extent that no free liquid exists, carboxymethy-cellulose has a content of 15 to 70% relative to the remaining space of the liquid retaining layer. It is an alkaline zinc storage battery characterized by being filled at a rate of %.

Example Hereinafter, the details of the present invention will be explained using one example.

Fig. 1 is a partially cutaway perspective view of an alkaline zinc storage battery showing an embodiment of the present invention, Fig. 2 is a diagram showing the relationship between force and swelling degree of bokin methyl cellulose and electrolyte concentration, Fig. 3 Figure 4 shows the relationship between the force of the liquid retaining layer μ poxime f ~ the filling rate of cellulose and the liquid retaining rate, and Figure 4 shows the force μ poxime f of the liquid retaining layer
A diagram showing the relationship between the filling rate of Ceyrose and the dripping index. Figure 5 is a plan view showing the positional relationship in which the electrode plates and separators face each other. Figure 6 shows the current distribution in the zinc electrode plate. 7 are diagrams showing the charge/discharge cycle characteristics of the battery of the present invention and a conventional battery.

Here, 1 is a nickel electrode, 2 is a zinc electrode, 3 is a liquid retaining layer, 4 is a separator, and 5 is a battery case.

The zinc electrode uses a copper punched current collector with many holes as a core metal, and zinc active material sheets are attached to both sides of the metal core. All zinc poles are connected by terminals. The nickel electrode is a known positive electrode plate in which a sintered nickel porous body is filled with an active material whose main component is hydroxide dandruff μ by a chemical impregnation method. Connected to the positive pole by a terminal. Furthermore, each electrode plate has a separator and a molecular weight of 10.000 to 15.00.
0 power Boki V mechi H*1va-y, (hereinafter 0.M, O
, is written. ) A nickel-zinc storage battery with a nominal capacity of 30 mh was prepared by injecting a KOH aqueous solution of &0jllOII#, which was surrounded by a liquid-retaining layer filled with 60 ml.

The degree of swelling of C, M, and a changes depending on the concentration of the electrolytic solution.

Therefore, when considering the filling rate of C, M, and C into the liquid retaining layer, it is necessary to change the appropriate filling value depending on the concentration. The electrolyte concentration to be investigated is 5w5ol/l (d-1,20) to 10.4111, which does not have much influence on the battery active material utilization rate.
01/l (d-1,41)@The results are shown in FIG. Next, C, M, 0. is the most expanding KO
For a H concentration of 6 mol/l and a KOH concentration of 9 mol/l, which has the smallest expansion degree, 13. The range in which M, C, and C can be filled was measured. After a sufficient amount of electrolyte was injected into the battery, the relationship between C, M, O, filling rate, and liquid retention rate of the liquid retention layer was investigated.

The results are shown in Figure 3. From the results in Figure 5, O, M,
It can be seen that the higher the filling rate of O, the higher the liquid retention rate・a
, W, a, the higher the filling rate, the better.
In OR/1, when the filling rate exceeds 40%, % qwsol
/ll, when the filling rate exceeds 70, the liquid retention rate is 100.
- exceeds. This is because O, M, and O absorb more electrolyte than the remaining space in the liquid retaining layer and swell. This results in the battery case expanding, which adversely affects battery performance. Therefore, it is appropriate to set the values below 40% and 70%, respectively, so that the battery case does not swell.

However, if the filling rate of c, m, and c is too small, a drop will occur, resulting in uneven internal resistance and failure to maintain battery performance.

C1M, C, of the liquid retaining layer when enough electrolyte is injected into the battery
The relationship between the filling rate and the drip index was investigated.

Note that the drip index referred to here refers to a and 8 shown in Figure 5.
This is the value obtained by calculating the liquid volume of the nonwoven fabric at a position corresponding to 1C by using the following formula, 1 part of the liquid 1. From the results shown in Figure 4, the lower limit values that do not affect battery performance are 6mo (
1/l KOH, 9mol/(j KOH]'flL C, M, C, filling rate is 1 so that the dripping index is 1 for the solution
5% and 50% are appropriate.

From this, the filling rate of C,

Among these, the one with the highest liquid retention amount is the KOH concentration of 8.
(This was when l+ol#, c, m, c, filling rate was 6C1%.

The electrode plate size of the liquid retaining layer is 140 x 140 m and the above capacity is 3
Using a battery of 0 μh, the depth of discharge is 60% of the nominal capacity with a current of 6 μm, and the amount of charge is 10% of the discharge capacity with a current of 3 A.
The relationship between the number of charge/discharge cycles and the discharge capacity when the ratio is 5% was investigated. Here, battery A is the battery of the present invention, and battery B is a conventional product that is not filled with the retaining liquid 111CO, M, G. It's a battery. The structure of battery B is the same as that of battery A except that the liquid retaining layer of battery B is not filled with C, M, and O.

Regarding this result, the discharge capacity of the conventional battery shown in FIG. 7 decreases as the charge/discharge cycle μ continues.

The battery of the present invention maintains 70% of its initial capacity even after 400 cycles.

In order to eliminate the second cause, the current distribution of the zinc electrode was measured for batteries A and B, and is shown in FIG.

The measurement method was performed at five parts a, b, c, a, and e in FIG. Battery B has a peak of d, e at part C.
In contrast to the large current (!F degree) in battery A, the current density was almost uniform in battery B.
Since a nonwoven fabric is used that is not filled with , the electrolyte moves downward or to the center, causing non-uniformity of the electrolyte. As a result, the current distribution also became non-uniform, which is thought to have lowered the utilization rate. In addition, in areas where a large amount of current flows, there is also a large amount of electrolyte, making it easy for dendritic seats to occur, which is thought to have shortened the cycle life.

On the other hand, battery A uses a non-woven fabric filled with C, M, and G, so the electrolyte does not become uneven, and problems like those in battery B are suppressed, resulting in a good cycle life. It seems to be.

Effects of the Invention As described above, the present invention can provide an alkaline zinc storage battery that maintains the electrolyte uniformly for a long period of time, suppresses Gundheit shift and change, and has a long-life cider μ characteristic. Therefore, its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of an alkaline zinc storage battery showing an embodiment of the present invention, and FIG. 2 is an O, M diagram. Figure 6 shows the relationship between C0 swelling degree and electrolyte concentration. Figure 6 shows the relationship between C, M, C, filling rate and liquid retention rate of the liquid retaining layer. Figure 4 shows the relationship between the swelling degree of C0 and the electrolyte concentration. A diagram showing the relationship between the filling rate of C, M, and O and the drip index, Figure 5 is a diagram showing the positional relationship between the electrode plate and the separator, and Figure 6 is a diagram showing the current distribution in the electrode plate. FIG. 7 is a diagram showing charge/discharge cycle characteristics. 1... Nickel FM 2... Zinc electrode 6... Holder i11 4... Separator 5... Battery case

Claims (1)

[Claims] An electrode group consisting of a zinc electrode whose main component is zinc oxide or metallic zinc, a nickel electrode, a separator and a liquid retaining layer interposed between these two electrodes, and an extent to which there is no free liquid absorbed and retained in the electrode group. What is claimed is: 1. An alkaline zinc storage battery having an alkaline electrolyte limited to 10%, wherein the remaining space of the liquid retaining layer is filled with carboxymethyl cellulose at a ratio of 15 to 70%.