JPH048897B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a zinc electrode that can be applied to alkaline storage batteries that use silver oxide, nickel oxide, etc. as a positive electrode active material and an alkaline solution as an electrolyte. In addition to regulating the particle size of the substances metal zinc and zinc oxide, metal zinc, mercury,
By alloying with at least one of indium, lead, and tin, it prevents the crystal diameter of the negative electrode active material from becoming coarser due to charging and discharging cycles, suppresses deformation of the zinc electrode plate, and minimizes the decrease in battery capacity. , aiming to improve battery cycle life.

[Background technology]

Conventionally, zinc storage batteries that use metal zinc as an active material in the negative electrode have a high energy density and are free from pollution because zinc is cheap and has a lower potential in alkaline electrolyte than a cadmium electrode. Because of its small size, many studies have been made to put it into practical use.

However, drawbacks include a lack of reliability due to a short circuit phenomenon between the positive and negative electrodes due to zinc dendrites during the charge/discharge cycle, and difficulty in obtaining a long cycle life due to significant deformation of the zinc electrode during the charge/discharge cycle. There is. This is due to the fact that zinc is an electrode that is soluble in an alkaline electrolyte.

Thus, it is known to use a mixture of metallic zinc and zinc oxide as a zinc active material. However, conventionally used metallic zinc has a particle size of several tens of microns to several hundred microns, while zinc oxide has a particle diameter of several tenths of a micron, which is two to three orders of magnitude smaller than that of metallic zinc. be. As described above, the particle size of conventional metal zinc is particularly large compared to the particle size of zinc oxide, resulting in the following drawbacks. First, since the difference in particle size is as large as two to three orders of magnitude, metallic zinc and zinc oxide are not mixed uniformly. Second, because the particle size is large, even if the same amount of metallic zinc is mixed, the number of particles is small and the number that becomes the nucleus for electrodeposition is small, so the zincate ions that are discharge products are returned to their original state during the next charge. It becomes difficult to electrodeposit on the position. Thirdly, since the particle size of the original metal zinc is large, it quickly grows into coarse zinc particles that become the core of dendrite generation.

In order to deal with this problem, we proposed in Japanese Patent Application No. 41843/1983 that the particle diameters of the active materials, metal zinc powder and zinc oxide powder, should be regulated. That is, the particle size of the metal zinc powder is 1 to 6μ, and the particle size of the zinc oxide powder is 0.1 to 0.5μ. By regulating the particle size in this way, it is possible to prevent the crystal size of the active material from becoming coarser due to charging and discharging cycles, suppress deformation of the electrode plate, minimize capacity loss, and improve the cycle life of the battery. can.

However, as charge-discharge cycles are repeated over a longer period of time, the regulated zinc particles gradually become coarser and denser, reducing the number of zinc particles that should form the nucleus of zinc electrodeposition. . As a result, non-uniform electrodeposition occurs, causing an internal short circuit between the zinc electrode and its counter electrode, and there is a limit to the improvement in the cycle life of the battery.

[Disclosure of the invention]

The present invention has been devised in view of these points, and is intended to alleviate the above-mentioned problems and further improve the cycle life of a storage battery when applied to a storage battery. That is, the present invention provides particle diameters of 1 to 1 containing at least one of mercury, indium, lead, and tin.
It is characterized in that the zinc active material is a zinc alloy powder of 6μ and a zinc oxide powder having a particle size of 0.1 to 0.5μ. By alloying metallic zinc powder with a controlled particle size in this way, the alloyed metal that adheres to the metallic zinc fine particles effectively prevents the coarsening of the zinc fine particles, suppresses dendrites, and further improves cycle life. This is what I am trying to do.

〔Example〕

Examples of the present invention will be described below, as well as comparative examples.

Example 1 First, metal zinc powder having a particle size of 1 to 6 μm is added to a mercury chloride solution having a concentration of 3 to 5%, stirred with a stirrer for 10 minutes, and then washed with water 5 to 8 times. Next, after adding acetone, drying was performed with acetone removed to produce a mercury-zinc alloy powder, which was a fine particle containing about 3% by weight of mercury.

Next, 100% by weight of zinc oxide powder with a particle size of 0.1 to 0.5μ, 10% by weight of the above zinc alloy powder, and 2% by weight of mercury oxide were added to a mixed powder with 5% by weight of polytetrafluoroethylene dispersion (concentration 60%). and water 50
% by weight is added and kneaded while applying shear force. The paste sheet obtained by rolling the obtained kneaded product to a thickness of 1.0 mm with a rolling roller is brought into contact with both sides of the cathode current collector, and is rolled and crimped to obtain a zinc electrode with a thickness of 1.5 mm.

These 5 zinc negative electrodes and 4 well-known sintered nickel electrodes
Nickel-zinc storage battery A with a capacity of 2AH using
It was created.

In addition, conventional metallic zinc powder with a size of several tens of microns to several hundred microns is
Metallic zinc powder is manufactured by melting metallic zinc once in a reducing atmosphere and blowing it out in a spray form from a nozzle, whereas the metallic zinc powder used in the present invention is produced by melting metallic zinc in a reducing atmosphere. It is then evaporated and condensed.

FIG. 1 is a sectional view of this storage battery A. In this drawing, 1 is a zinc electrode, 2 is a nickel electrode, 3 is a separator, 4 is a liquid retaining layer, 5 is a battery case, 6 is a battery cover, and 7 and 8 are positive and negative terminals.

Example 2 Metallic zinc powder having a particle size of 1 to 6 μm was added to a solution of indium nitrate with a concentration of 3 to 5%, and in the same manner as in Example 1, the indium content was approximately 3% by weight.
Indium-zinc alloy powder, which is added fine particles, was prepared.

A zinc electrode was prepared in the same manner as in Example 1, except that this indium-zinc alloy powder was used in place of the mercury-zinc alloy powder of Example 1, and a nickel-zinc storage battery B was prepared.

Example 3 In a solution of lead acetate with a concentration of 3 to 5%, particles with a diameter of 1 to
A lead-zinc alloy powder to which approximately 3% by weight of lead was added was prepared in the same manner as in Example 1 by adding metallic zinc powder having a particle diameter of 6μ.

A zinc electrode was produced in the same manner as in Example 1, except that this lead-zinc alloy powder was used in place of the mercury-zinc alloy powder in Example 1, and a nickel-zinc storage battery C was produced.

Example 4 In a solution of tin chloride with a concentration of 3 to 5%, a particle size of 1
Example 1 with metal zinc powder having ~6μ
In the same manner as above, a tin-zinc alloy powder to which approximately 3% by weight of tin was added was prepared.

This tin-zinc alloy powder was mixed with the mercury-zinc alloy powder of Example 1.
A zinc electrode was prepared in the same manner as in Example 1, except that zinc alloy powder was used instead, and a nickel-zinc storage battery D was prepared.

Comparative Example For comparison, a zinc electrode was prepared in the same manner as in Example 1, except that unalloyed metallic zinc powder was used in place of the mercury-zinc alloy powder, and a nickel-zinc storage battery was prepared. I created E.

Figure 2 shows a storage battery A using zinc electrodes according to the present invention.
FIG. 3 is a charge/discharge cycle characteristic diagram of comparative battery E. The charging/discharging conditions are: After charging at 400mA for 5 hours,
It discharges at 500mA until the battery voltage reaches 1.0V. Figure 2 shows the initial capacity as the discharge capacity.
Shown as 100.

It can be seen from FIG. 2 that the cycle characteristics of storage battery A using the zinc electrode according to the present invention are improved compared to the cycle characteristics of comparative battery E. The cycle characteristics of storage batteries B to D were approximately the same as those of storage battery A.

The reason why the cycle characteristics of the storage battery using the zinc electrode according to the present invention are improved compared to the cycle characteristics of the comparative battery is that each metal attached to and alloyed with fine particles of metal zinc is It is thought that this effectively prevents the coarsening of the powder and suppresses the formation of dendrites. In addition, the metals that alloy zinc powder, such as mercury, indium, lead, and tin, form a strong alloy with zinc, so they do not desorb or peel off even over a longer cycle life, and they remain fine particles. It has effects such as effectively preventing coarsening of zinc alloy powder and suppressing self-discharge due to high hydrogen overvoltage. In the examples, an example of one type of each metal was shown, but even when alloying two or more types of metals,
It is clear that it has the same effect as the case of one type.

〔effect〕

As described above, the present invention regulates the particle size of the zinc alloy powder and zinc oxide powder that are the active materials of the zinc electrode, and also uses metal zinc alloyed with at least one of mercury, indium, lead, and tin. By using the above-mentioned zinc alloy powder, it is possible to prevent the crystal size of the negative electrode active material from becoming coarse due to charge/discharge cycles, and to suppress deformation of the zinc electrode, thereby increasing the cycle life of a storage battery using this zinc electrode. It has great industrial value as it can be further improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an alkaline zinc storage battery A using a zinc electrode according to the present invention, and FIG. 2 is a cross-sectional view of an alkaline zinc storage battery A using a zinc electrode according to the present invention and a comparative battery E.
FIG.

Claims (1)

[Claims] 1 At least 1 of mercury, indium, lead, and tin
A zinc electrode characterized in that zinc alloy powder containing seeds and having a particle size of 1 to 6 μm and zinc oxide powder having a particle size of 0.1 to 0.5 μm are used as zinc active materials.