JPS60136182A - Air cell - Google Patents

Abstract

PURPOSE:To prevent any decrease in the discharge capacity and any liquid leakage of an air cell so as to improve its characteristics by specifying the concentration and the proportion of a caustic alkali in a gel-like zinc negative electrode and by selecting a proper gelling agent. CONSTITUTION:In an air cell constituted using a gel-like zinc negative electrode, an aqueous solution of caustic soda or caustic potash having a concentration of 4-12mol/l is used as alkali electrolyte. The proportion of the alkali electrolyte in the gel-like zinc negative electrode is adjusted to be within the range of 15- 30wt%. A carboxyvinyl polymer having a molecular weight of 100,000-5,000,000 is used as a gelling agent and the proportion of the gelling agent is adjusted to within the range of 0.3-3%. The gel-like zinc negative electrode is made by completely dissolving a carboxyvinyl polymer in an alkali solution to produce a gel before the remaining amount of an amalgamated zinc powder is kneaded into the gel to homogeneously disperse the powder in the gel. Since the gelling agent used in this invention has a superior liquid-holding property, it is possible to constitute an air cell in which no decrease in the discharge capacity is caused and no liquid leakage occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an air battery using a gelled metal cathode formed by kneading metal powder, an alkaline electrolyte, and a gelling agent.

[Technical background of the invention and its problems] Conventionally, in this type of battery, carboxymethyl cellulose, polyvinyl alcohol, sodium polyacrylate, sodium alginate, etc. have been used as cathode gelling agents, but these have been used for battery storage. The electrolyte that has been separated is not the one that has been oxidized or hydrolyzed by the alkaline electrolyte, or that has been altered and its viscosity has decreased, causing the zinc particles and the electrolyte to separate, resulting in a decrease in discharge capacity. It was not a satisfactory gelling agent as it had drawbacks such as the liquid leaking through the air electrode.

Furthermore, when the air battery is opened, that is, when it is in use, the water vapor pressure inside the battery system is different from that outside the system, so water vapor enters and exits as it tries to reach equilibrium. For example, if the water vapor pressure outside the battery system is higher than inside the battery system, water vapor will enter the battery, causing a decrease in the alkaline electrolyte concentration, a drop in the operating voltage, and even leakage. When the outside water vapor pressure is low, it induces evaporation of water in the electrolyte and an increase in internal resistance, and in either case, battery performance is significantly degraded.

[Object of the Invention] In view of the above-mentioned drawbacks, the present invention provides a gelling agent that has excellent liquid retention properties without being oxidized, hydrolyzed, or altered by alkaline electrolyte during storage of batteries, thereby improving discharge capacity. The purpose of the present invention is to provide an air battery that can prevent liquid leakage.

[Summary of the invention] The gel-like zinc cathode used in the present invention has a capacity of 4 to 12 tnol/.

Preferably, 0.3 to 3 wt% of a carboxyvinyl polymer having a molecular weight of 100,000 to 5 p.o.o.o. Add and stir. After the carboxyvinyl polymer is completely dissolved in the alkaline solution and gelled, the remaining amount of zinc hydride powder is added and kneaded to uniformly disperse it in the gel.

The reason why the concentration of the caustic potash aqueous solution is set to 4 to +2 rrrall/l is that outside this range, the specific conductivity becomes small, and if it is less than 6711, the amount of zinc dissolved in the caustic potash solution decreases significantly. , and 1orrlol/l
The main reason for this is that when the temperature exceeds 1, the difference between the water vapor pressure outside the battery system and the water vapor pressure outside the battery system is markedly different. Also, the blending ratio is 15 to 30
The wt% is the value obtained from the dissolved amount of zinc, the discharge capacity, the viscosity of the gel, etc.

= The molecular weight of the polymer is i o o, o
o o~゛ 5ρoo, ooo, blending ratio 0.3~3
It depends on the molecular weight, but if it is less than 0.3 wt%, it will be difficult to gel.If it is less than 0.3 wt%, the zinc particles and electrolyte will be separated, and if it exceeds awt, the viscosity of the gel will be very high and the internal resistance will decrease. In addition, it is difficult to disperse zinc particles uniformly in the gel, making it difficult to manufacture.

[Embodiments of the Invention] The present invention will now be described in detail according to embodiments with reference to FIG.

<Example 1. 〉 □ The composition of gelled zinc cathode 5 is gelling agent 1 wt%, 1
0m01/l caustic potash electrolyte 20wt%, remaining amount 10
% amalgamated zinc powder was collected, and further an air electrode 7 was provided through a separator 6, and a positive electrode can 1,
Insert the cathode sealing lid 2 into the button type air battery (R-44
type) was obtained. In the figure, 3 indicates a gasket, 4 indicates an air hole, 8 indicates a water-repellent membrane, and 9 indicates an air chamber. Table 1 shows a comparison of the discharge efficiency when this battery was discharged at a constant resistance of 2500 until the terminal voltage reached 0.9V and the discharge efficiency after being stored at room temperature for 6 months.

As is clear from the above Table 1, the water-based gelling agent provides a cathode with excellent storage stability.

<Example 2. > A hole of φ8 size was made in the bottom of the positive electrode can of a button-type air battery assembled under the same conditions as in Example 1, and the battery was stored in an atmosphere of 45° C. and 90 fiRH, and leakage from the air electrode was observed. The results are shown in Table 2. The number of orange batteries was 10 each, and leakage was confirmed using a microscope with a high cutting magnification. .

Table 2 (Number of leakage particles) □ As is clear from the above table, the gelling agent of the present invention exhibits an excellent effect on liquid retention.

Next, the thickening effect and dispersion ability of carboxyvinyl polymer will be investigated.

Carboxyvinyl polymer as a gelling agent (trade name:
Carbobol) 4 carboxymethylcellulose (CMC
) and sodium alginate, the thickening effect in water (Figure 2) and the effect of temperature on the viscosity of aqueous solution (Figure 3) were investigated, and curves q and b were obtained, respectively.

Shown as C. In addition, the concentrations of the gelling agents in FIG. 2 are 1 g of case ball, 2% of CMC, and 2.0 g of sodium alginate.
5% was used.

Next, the sedimentation time when silica sand (average diameter Q, 5 m) was dispersed in the gelling agent was investigated, and the results are shown in Table 3.

As is clear from the above results, it is clear that carboxyvinyl polymer (Carbopol) exhibits characteristics that are superior to other gelling agents in terms of thickening effect and dispersion ability.

[Effects of the Invention] As is clear from the above results, the air battery according to the present invention can be said to have excellent specificity without a decrease in discharge capacity or leakage. −

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the configuration of an air battery according to the present invention;
FIGS. 2 and 3 are cross-sectional views showing examples of the characteristics of the gelling agent used in the present invention. 1... Positive electrode can, 2... Cathode sealing lid, 3... Gasket, 4. ... air hole, 5 ... gelled zinc cathode,
6...Separator, 7...Air electrode, 8...Water repellent membrane, 9...Air chamber. Agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Yuka Zuno) Figure 8 On and CC')

Claims (1)

[Scope of Claims] An air battery using a gelled expanded lead cathode prepared by kneading zinc hydrate powder, an alkaline electrolyte, and a gelling agent, wherein the alkaline electrolyte consists of caustic soda or an aqueous solution of caustic potash, and The solution concentration is 4 to 12 mol/,
The blending ratio is in the range of 15 to 30 wt%, the gelling agent is made of carboxyvinyl polymer with a molecular weight of 100,000 to 5,000,000, and the blending ratio is in the range of 0.3 to 3w.
1. An air battery characterized in that the air cell is in the range of t%.