JPH04284362A - Alkaline battery - Google Patents

Abstract

PURPOSE:To provide an alkaline battery able to obtain high current and to make efficient discharge while attempting mercury-freeing. CONSTITUTION:A granular state gelling agent, having three-dimensional structure and a grain diameter of 50mum or larger, is contained in a gelling agent mentioned later in a zinc alkaline battery having a gel-like cathode 7 in which a cathode active material, having a main body of zinc alloy powder, is dispersed in a gel-like electrolyte composed of an alkaline electrolyte and the gelling agent.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an alkaline battery having a gel cathode in which a cathode active material mainly composed of zinc powder is dispersed in a gel electrolyte consisting of an alkaline electrolyte and a gelling agent, and in particular to a gel cathode. This invention relates to improvements in gelling agents used in shaped cathodes.

0002

2. Description of the Related Art A so-called gel cathode is generally used as the cathode of a zinc-alkaline dry battery. The specific structure of this gel-like cathode is, for example, a gel-like cathode that is made highly viscous with a gelling agent such as cross-linked polyacrylic acid (Junron PW150, manufactured by Nippon Pure Chemical Industries, Ltd.), which is made of fine powder with a particle size of about 20 to 50 μm. It has a structure in which aqueous zinc powder is dispersed in an alkaline electrolyte. With such a structure, ions in the electrolytic solution can easily diffuse and the surface area of the cathode can be expanded, so that polarization can be reduced even under strong discharge. Furthermore, since the cathode can be handled in the same way as a liquid, handling efficiency during production is improved.

0003

Nowadays, with the problem of environmental pollution being brought into sharp focus, there are strong expectations for batteries that do not contain any mercury. However, when non-viscous zinc powder is used in place of the viscous zinc powder mentioned above, the internal resistance of the battery increases significantly because the contact between the zinc particles or between the zinc particles and the current collector becomes weak. , short circuit current and circuit voltage drop significantly. As a result, there was a problem in that the characteristics of alkaline batteries, such as being able to draw a large current and perform efficient discharge, were impaired.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide an alkaline battery that can achieve zero battery life without impairing the characteristics of alkaline batteries, such as being able to draw a large current and efficiently discharging. With the goal.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a gel in which a cathode active material mainly composed of zinc powder is dispersed in a gel electrolyte consisting of an alkaline electrolyte and a gelling agent. In the alkaline battery having a shaped cathode, the gelling agent contains a granular gelling agent having a three-dimensional structure and a particle size of 50 μm or more.

[0006]

[Action] Although the action of the gelling agent used in the present invention is not clear, it is presumed as follows. The granular gelling agent absorbs the alkaline electrolyte in the gelled cathode, swells to some extent, and no longer swells. That is, the granular gelling agent takes on a state similar to that of a fishing net, and maintains this state for a long time. The swollen gelling agent keeps the zinc particles under constant pressure, so that good contact between the zinc particles or between the zinc particles and the current collector is maintained. In other words, the granular gelling agent has a role similar to that of mercury, so even when non-reactive zinc powder is used as the cathode active material, a large current can be extracted and efficient discharge is possible. .

[0007]

[Example] (First Example) The first example of the present invention is shown in FIG.
The following is an explanation based on the following. [Embodiment 1] FIG. 1 is a sectional view of an LR6 type battery, which is an example of the alkaline battery of the present invention. In FIG. 1, reference numeral 1 denotes an anode can, and in this anode can 1, an anode 5 mainly made of manganese dioxide, a separator 6, and a cathode 7 containing zinc particles are arranged. Further, a cathode terminal plate 2 is attached to the opening of the anode can 1 via a sealing gasket 3, and this cathode terminal plate 2 is electrically connected to the cathode 7 via a current collector rod 4. .

[0008] Here, the cathode 7 was manufactured as follows. First, an electrolytic solution containing 40% KOH aqueous solution saturated with zinc oxide was mixed with known finely powdered polyacrylic acid and cross-linked sodium polyacrylate (adjusted using a Tyler standard sieve, the particle size of which was 50 to 100 μm). It was produced by gelatinizing with a gelling agent mixed in a weight ratio of 1:1 and dispersing ineffective zinc powder in this gel.

On the other hand, the anode 5 was prepared by mixing graphite with manganese dioxide and press-molding the mixture. The battery thus produced is hereinafter referred to as the (A1) battery. [Examples 2 to 5] As a crosslinked polyacrylic acid soda,
Particle size is 100-250μm, 250-500μm, 50
Batteries were produced in the same manner as in Example 1, except that 0 to 850 μm and 850 to 1000 μm were used, respectively.

The batteries thus produced are hereinafter referred to as (A2) battery to (A5) battery, respectively. [Comparative Example 1] A battery was produced in the same manner as in Example 1, except that a crosslinked sodium polyacrylate having a particle size of 32 to 50 μm was used.

[0011] The battery produced in this manner is shown below (X
1) It is called a battery. [Comparative Example 2] A battery was produced in the same manner as in Example 1 above, except that only finely powdered polyacrylic acid was used as the gelling agent. The battery produced in this way is shown below (X2)
It is called a battery. [Experiment] The discharge characteristics of the batteries (A1) to (A5) of the present invention and the batteries (X1) and (X2) of the comparative examples were investigated, and the results are shown in Table 1 below. The experimental conditions were constant resistance (3.9Ω) and battery voltage of 0.9V.
The condition is to discharge up to

0012

[Table 1]

As is clear from Table 1, (A1
) Batteries ~ (A5) It is observed that the discharge duration of the batteries (A5) is longer than that of the comparative examples (X1) and (X2) batteries. This is because in a (X2) battery that does not contain crosslinked sodium polyacrylate, the pressure exerted by the gelling agent is weak, so the contact between the zinc particles or between the zinc particles and the current collector decreases. In addition, in (X1) batteries in which the particle size of the cross-linked sodium polyacrylate is less than 50 μm, the particle size of the cross-linked sodium polyacrylate and the fine powder cross-linked polyacrylic acid is not much different, so the gelling agent It is not possible to improve the pressure. On the other hand, (A1
) Battery - (A5) In the battery, the crosslinked sodium polyacrylate absorbs the alkaline electrolyte and swells to some extent, and its particle size is large, so the zinc particles are constantly subjected to pressure by the swollen gelling agent. Therefore, this is thought to be due to the fact that good contact between the zinc particles or between the zinc particles and the current collector is maintained.

In particular, it is recognized that the discharge duration of the (A2) to (A4) batteries is dramatically longer. This is because if the particle size of the cross-linked sodium polyacrylate is 100 μm or more, the above-mentioned effect of addition is more exhibited, but if the particle size of the cross-linked sodium polyacrylate is 850 μm or more,
It is thought that this is because if it exceeds 100%, the particle size becomes too large due to swelling after forming into a gel cathode, and the amount of zinc powder packed decreases.

[0015] Therefore, the particle size of the crosslinked sodium polyacrylate is desirably 100 μm or more and 850 μm or less. Although not shown in this example, (A
2) Battery - (A4) It has been confirmed through experiments that the battery has approximately the same discharge characteristics as a battery in which mercury is added to the negative electrode.

(Second Example) [Example 1 to Example 3] As the granular gelling agent, cross-linked polyacrylic acid, grafted starch, and carboxymethyl cellulose were used instead of cross-linked sodium polyacrylate, respectively. Otherwise, a battery was produced in the same manner as in Example 1 of the first example.

The batteries thus produced are hereinafter referred to as (B1) battery to (B3) battery, respectively. [Comparative example] Example of the first example, except that only finely powdered polyacrylic acid was used as the gelling agent, and zinc alloy powder to which about 0.6 wt% of mercury was added was used instead of zinc powder. A battery similar to 1 was created.

[0018] The battery produced in this manner is shown below (Y
) is called a battery. [Experiment 1] Battery (A1) of the present invention, batteries (B1) to (B3) of the present invention, and (Y
) After storing the batteries at 60° C. for 30 days, the discharge characteristics of each battery were examined, and the results are shown in Table 2. The experimental conditions for the discharge characteristics were the same as those for the first embodiment.

[0019]

[Table 2]

As is clear from Table 2, (A1
) battery, (B1) battery, and (B2) battery are found to have the same discharge duration as the (Y) battery containing mercury. On the other hand, in the (B3) battery of the present invention,
It is observed that the discharge duration is significantly shortened. Therefore, when storing batteries at high temperatures for long periods of time,
As the granular gelling agent, crosslinked polyacrylic acid, crosslinked sodium polyacrylate, and grafted starch are preferably used.

As mentioned above, the characteristics of the (B3) battery are inferior due to the presence of the alkaline electrolyte and the 60%
Carboxymethylcellulose decomposes due to being stored for a long period of time at high temperatures of °C. This is thought to be due to the fact that the cathode cannot maintain its gel state and the zinc powder settles. [Experiment 2] In this experiment, the optimum concentration of the granular gelling agent was investigated.

Specifically, batteries were prepared in the same manner as in Example 1 above, except that the content ratios of cross-linked polyacrylic acid, cross-linked sodium polyacrylate, and grafted starch were varied. The discharge characteristics were investigated and the results are shown in FIG. The experimental conditions were the same as those of the first embodiment. As is clear from FIG. 2, no matter which granular gelling agent is used, the total concentration of gelling agent is 40 to 6
It is recognized that the discharge duration becomes longer in the range of 0 wt%.

[0023]

As explained above, according to the present invention, good contact between zinc particles or between zinc particles and a current collector can be maintained without using mercury. As a result,
It has the excellent effect of being able to extract a large current while achieving zero discharge, and enabling efficient discharge.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an LR6 type battery, which is an example of the alkaline battery of the present invention.

FIG. 2 is a graph showing the relationship between granular gelling agent concentration and discharge duration.

[Explanation of symbols]

5 Anode 6 Separator 7 Cathode

Claims (1)

[Claims] [Claim 1] A cathode active material mainly composed of zinc powder,
In an alkaline battery having a gelled cathode dispersed in a gelled electrolyte consisting of an alkaline electrolyte and a gelling agent, the gelling agent includes a gelled granule having a three-dimensional structure and a particle size of 50 μm or more. An alkaline battery characterized by containing an agent.