JPS5935359A - Zinc electrode - Google Patents

Abstract

PURPOSE:To increase cycle life by forming a zinc electrode of an alkaline storage battery with an active material prepared by adding a wetting material, an additive, and a binder to zinc oxide powder and metal zinc powder both having a specified particle size. CONSTITUTION:Zinc oxide powder having a particle size of 0.1-0.5mu, metal zinc powder having a particle size of 1-6mu, mercuric oxide, polyvinyl alcohol are mixed. Polytetrafluoroethylene dispersion and water are added to above mixture and they are kneaded. A paste sheet made of the kneaded material is kept in contact with an anode current collector to form a zinc electrode 1. The zinc electrode 1 is combined with a sintered nickel electrode 2 with an electrolyte absorbing layer 4 and a separator 3 interposed, and they are accommodated in a container 5 to form a nickel-zinc alkaline storage battery. Crystal growth of an active material and deformation of an electrode plate are prevented. Diffusion of an electrolyte is supplemented and cycle life is increased.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a zinc electrode that can be applied to an alkaline storage battery that uses silver oxide, di/Kel oxide, etc. as a positive electrode active material and uses an alkaline solution as an electrolyte. By controlling the particle size of metallic zinc and zinc oxide, which are the active materials of the negative electrode, and adding a wetting agent, we prevent the crystal size of the negative electrode active material from becoming coarser due to charge/discharge cycles, and suppress the deformation of the zinc electrode plate. At the same time, the purpose is to compensate for insufficient diffusion of the electrolyte within the zinc electrode, minimize the decrease in battery capacity, and improve the cycle life of the battery.

[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, it lacks reliability due to a short circuit between the positive and negative electrodes due to zinc tendrite during the charge/discharge cycle.
There are disadvantages such as difficulty in obtaining a long cycle life due to the large deformation of the zinc electrode due to the charging and discharging cycles. 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 2 to 3 orders of magnitude larger than that of metallic zinc. It is the particle size. As described above, since the particle size of conventional metal zinc is particularly large compared to that of zinc oxide, there are the following drawbacks. First, because the difference in particle size is two to three orders of magnitude large, 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 of electrodeposition is small. 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, a patent application was filed in 1973 to regulate the particle size of the active materials, metal zinc powder and zinc oxide powder.
It was proposed in No. 7-41843. That is, the particle size of metal zinc powder is 1 to 6μ, and the particle size of zinc oxide powder is 0.1 to 0.5μ.
p. 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, and the number of cleaved zinc particles, which form the core of zinc electrodeposition, decreases. . As a result, non-uniform electrodeposition occurs, the effective area of the zinc electrode increases, and the porosity decreases, which impedes internal diffusion of the electrolyte and reduces conductivity. . That is, a passivation phenomenon occurs, leading to an accelerated deterioration in the utilization rate of the active material as charging and discharging are repeated.

[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 improve the cycle life of a storage battery when applied to a storage battery. That is, the present invention uses zinc oxide powder having a particle size of 0.1 to 05μ and a particle size of 1 to 6μ.
A zinc electrode is constituted by a zinc active material of metallic zinc powder having a particle size of , an organic or inorganic wetting agent, an additive, and a binder. As is clear from this configuration, the present invention suppresses the deformation of the zinc electrode and improves the cycle life of the battery by regulating the particle frame of the active materials, metal zinc powder and zinc oxide powder. Its presence compensates for insufficient diffusion of the electrolyte within the zinc electrode and further improves the cycle life.

〔Example〕

A comparative example will be explained below along with a detailed explanation of the present invention.

Example 1 A mixture of 100% by weight of zinc oxide powder with a particle size of 01 to 0.5μ, 10% by weight of metal zinc powder with a particle size of 1 to 6.11%, 2% by weight of mercury oxide, and 2% by weight of polyvinyl alcohol. Add 5% by weight of polytetrafluoroethylene dispersion (concentration 60%) and 50% by weight of water to the powder,
Crosstalk while applying shearing force. The obtained mixed wire was rolled with a rolling roller to a thickness of 1, Q mm, and the base sheet was brought into contact with both sides of the cathode current collector, and the mixture was rolled and crimped to a thickness of 1.5 m.
obtain a zinc electrode.

A nickel-zinc storage battery (A>) with a capacity of 2 AH was created using five of these zinc negative electrodes and four known sintered nickel electrodes.

In addition, conventional metallic zinc powder of tens to hundreds of microns is produced by melting metallic zinc once in a reducing atmosphere and blowing it into a spray form, whereas the powder used in the present invention The metal zinc powder having a size of 1 to 6 microns is obtained by melting metal zinc in a reducing atmosphere, evaporating it, and condensing it.

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

Example 2 A storage battery (B) was produced which was the same as the storage battery (A) in Example 1 except that titanium oxide powder was used instead of polyvinyl alcohol in Example 1.

Comparative Example For comparison, the storage battery of Example 1 (A
) was created.

FIG. 2 is a diagram showing charge/discharge cycle characteristics of storage batteries (A) and (B) using zinc electrodes according to the present invention and a comparative battery (C). The charging and discharging conditions are: After charging at 400mA for 5 hours,
Electricity/1I2N pressure at 500mA or 1. The discharge continues until it reaches OV. FIG. 2 shows the initial capacity as 100 as the discharge capacity.

It can be seen from FIG. 2 that the cycle characteristics of the storage batteries (A) and (B) using the zinc electrode according to the present invention are improved compared to the cycle characteristics of the comparative battery (C).

The reason for this improvement is thought to be that polyvinyl alcohol and titanium oxide are wetting agents and therefore effectively compensate for the lack of electrolyte diffusion caused by the reduced porosity of the zinc electrode. Examples of polyvinyl alcohol and titanium oxide are shown in the examples, but other wetting materials such as carphoki/methylcellulose, methylcellulose, hydroquinpropylcellulose, and alkynoic acid may be used as long as they have wettability and do not adversely affect battery performance. Organic substances such as soda and gluconic acid, and inorganic substances such as ruconium magnenium and calcium aluminate (eg, sodium silica) can be used. The content ratio of the wetting agent is 0.

Less than 1% by weight has almost no effect, and 25% by weight
In the above, the amount of zinc active material has recently been reduced and the internal resistance of the zinc electrode has increased, so the amount may be about 0.1 to 25% by weight, preferably 0.3 to 10% by weight.

〔effect〕

As described above: The present invention is capable of controlling the particle size of metal zinc powder and zinc oxide powder, which are the active materials of the zinc electrode, and adding a wetting agent to increase the coarseness of the crystal size of the negative electrode active material during charge/discharge cycles. It has industrial value, such as being able to prevent deformation of the zinc electrode and suppress deformation of the zinc electrode, and compensate for insufficient diffusion of the electrolyte in the zinc electrode, increasing the cycle life of storage batteries using this zinc electrode. It is a big thing.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an alkaline zinc storage battery using the zinc electrode according to the present invention, and FIG. 2 is a cycle characteristic diagram of an alkaline zinc storage battery using the zinc electrode according to the invention and a comparative battery.

Claims (1)

[Claims] (1) Zinc oxide powder with a particle size of 0.1~05μ and 1
A zinc electrode comprising a zinc active material of metallic zinc powder having a particle size of ~6〃, an organic or inorganic wetting agent, an additive and a binder.