JP2931316B2 - Manufacturing method of alkaline zinc storage battery - Google Patents

Description

The present invention relates to an alkaline zinc storage battery using an alkaline electrolyte and using zinc as a negative electrode active material, such as a nickel-zinc storage battery and a silver-zinc storage battery.

2. Description of the Related ArtAlkaline zinc storage batteries using zinc as the negative electrode active material have been subjected to numerous research and development because zinc is inexpensive, pollution-free, and has a high energy density when used as a negative electrode active material. Nothing that can fully demonstrate its performance has yet been put to practical use.

The reason for this is that the zinc electrode is soluble in the alkaline electrolyte, and thus is repeatedly eluted and precipitated in the alkaline electrolyte. For this reason, the deformation of the zinc electrode occurs, the effective reaction area decreases, and the battery performance deteriorates. In addition, zincate ions eluted into the electrolytic solution at the time of discharging may not be uniformly electrodeposited on the zinc electrode surface at the time of charging, and may be a core of dendrite generation. Therefore, the dendrite that does not repeat charging and discharging grows and penetrates through the separator, and a short circuit occurs inside the battery. As a result, the cycle life of the battery is shortened.

In order to solve such a problem in the zinc electrode, it has been proposed to add various metals or metal oxides and metal hydroxides. By adding the additive in this way, it is intended to increase the hydrogen overvoltage of zinc to prevent the growth of zinc dendrites, and to make the charge and discharge reaction of the zinc electrode uniform, thereby suppressing the deformation of the electrode plate of the zinc electrode. Is what you do.

However, since the additive powder and the active material are usually mixed in a dry system, it is difficult to uniformly mix the additive powder and the active material.

Therefore, as disclosed in JP-A-53-85349, JP-A-61-118967, etc., there have been proposed ones using a zinc alloy as a negative electrode active material. With such a structure, the self-discharge of the battery is suppressed, and the additive component is present in the zinc particles serving as the nucleus of the charge / discharge reaction, so that the effect of the additive is exhibited from the beginning.

Problems to be Solved by the Invention By the way, when the zinc particles used as the active material have a large particle size, the surface area of zinc is reduced and the active material utilization rate is reduced, or it becomes easy to become a core of generation of dendrites. Therefore, the particle size of the zinc particles is suitably 100 μm or less. In this case, the zinc electrode is manufactured by adjusting the particle size ratio and the mixing ratio with zinc oxide. However, in the above structure, the addition amount of the additional element is at most 1 wt%, and it is difficult to suppress the generation and growth of dendrite with such a small addition amount.

Therefore, an object of the present invention is to provide an alkaline zinc storage battery having excellent cycle characteristics by suppressing self-discharge and deformation of an electrode plate and suppressing growth of dendrite.

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for manufacturing an alkaline zinc storage battery having a positive electrode, a negative electrode containing zinc as a main active material, and an alkaline electrolyte, comprising indium, thallium, gallium, and tin. After preparing zinc alloy particles containing at least one or more additional elements selected from the group consisting of, bismuth and lead, a zinc oxide layer is formed on the surface of the zinc alloy particles.

Operation With the above configuration, the cycle characteristics are improved, which is considered to be due to the following reason.

(1) Suppression of dendrite by surface modification Since a zinc oxide layer is formed on the surface of the zinc alloy, the surface of the zinc particles is coated with the zinc oxide particles by mixing the zinc particles and the zinc oxide particles as in the related art. As compared with the case, the surface of the zinc alloy can be completely covered. This alleviates the current concentration on the zinc particles, and increases the contact area, thereby improving the charging efficiency of the zinc oxide in contact with the zinc particles. As a result, dendrite precipitation can be prevented.

(2) Suppression of Deformation of Electrode Plate by Uniform Distribution of Additives By using a zinc alloy, the additive elements are uniformly distributed in the zinc electrode, so that the effect of the additive is exhibited from the beginning of the cycle. Therefore, the hydrogen overvoltage shifts to the base side, and no current flows locally. Accordingly, charging efficiency is improved, and changes with time such as elution of the active material and deformation of the electrode plate are reduced.

(3) Suppression of Self-Discharge Zinc dissolves in the electrolytic solution to generate hydrogen gas, but if covered with zinc oxide as in the above configuration, it is difficult to dissolve in the electrolytic solution, so self-discharge is suppressed.

(4) Suppression of passivation of zinc active material at the time of discharge Since the additional element is present in the surface zinc oxide layer, polarization increases and the reaction becomes uniform, so that the concentration of current is drastically suppressed. . Therefore, it is possible to suppress the formation of a dense zinc oxide layer that is hardly reduced by charging on the surface of the zinc particles during discharging, that is, the passivation of the zinc active material.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 3.
This will be described below.

Example 1 FIG. 1 is a cross-sectional view of an AA size nickel-zinc storage battery having a nominal capacity of 500 mAh.
And a negative electrode 2 using zinc as an active material, and these positive and negative electrodes 1.
The electrode group 4 including the separator 3 interposed between the two is spirally wound. The electrode group 4 is contained in a heat-shrinkable tube 5 and arranged in an outer can 6 also serving as a negative electrode terminal. A sealing body 8 is attached to the upper opening of the outer can 6 via a packing 7, and a coil spring 9 is provided inside the sealing body 8. When the internal pressure inside the battery rises abnormally, this coil spring
It is configured to be pressed in the direction to release the gas inside to the atmosphere. Further, the sealing body 8 and the positive electrode 1 are connected by a positive electrode conductive tab 10, and
The negative electrode 2 and the negative electrode 2 are connected by a negative electrode conductive tab 11.

In the above configuration, the negative electrode 2 was manufactured as follows.

First, 1.0% by weight of indium is added to zinc metal. Next, after these are melted, the surface of the zinc alloy obtained by the injection method is wet-oxidized to form a zinc oxide layer on the surface of the zinc alloy. Thereby, a surface modification active material is created. The average particle size of the surface-modified active material is about
20 μm, and the proportion of the surface zinc oxide layer is about 20% by weight. Next, the surface modifying active material (60% by weight)
, Zinc oxide (33% by weight), metal indium (2% by weight) as a conductive agent, and fluororesin (5%) as a binder.
% By weight) and kneaded by adding water.
An active material sheet is manufactured using a roller. Thereafter, the active material sheet is adhered onto a current collector made of copper or the like, and is then subjected to pressure molding. Finally, the molded product was dried to produce a negative electrode 2.

The battery fabricated in this manner is hereinafter referred to as (A ₁ ) battery.

(Examples II to VIII)

A battery was fabricated in the same manner as in Example I, except that the elements shown in Table 1 below were used as the additional elements at the time of preparing the surface-modified active material.

The battery fabricated in this manner is referred to as a battery (A ₂ ) below.
(A ₈₎ is referred to as a battery.

After adding 1.0% by weight of indium to metallic zinc and melting them, a zinc alloy (45% by weight) obtained by an injection method, zinc oxide (48% by weight), and metallic indium (2%) were obtained.
% By weight) and a fluororesin (5% by weight), and a battery was fabricated in the same manner as in Example I, except that a negative electrode was fabricated using a mixed powder.

The battery fabricated in this manner is hereinafter referred to as (X) battery.

[Experiment]

The batteries (A ₁ ) to (A ₈ ) of the present invention and the battery (X) of the comparative example
The results of a cycle test with a battery are shown in FIGS. 2 and 3. The test conditions include charging at 1 / 4C for 5 hours, discharging at 1 / 4C current, and terminating the discharge when the battery voltage reaches 1.0V. When the battery capacity became 50% or less, the life of the battery was determined.

As is clear from FIGS. 2 and 3, it can be seen that the (X) battery of the comparative example has a cycle life of about 300 cycles. On the other hand, the (A ₂ ) battery of the present invention
(A ₆₎ does not become the cycle life to approximately 370 to 430 cycles in batteries, also (A ₁₎ only not reduced until the battery capacity even after 450 cycles of about 70% in the cell, further (A ₇₎ cells And (A ₈ ) It is recognized that the battery capacity is maintained at about 80% even after 450 cycles.

From these facts, the present invention (A ₁₎ cell ~ (A ₈₎ cells suggests that performance was significantly improved compared to the (X) batteries of the comparative examples. This is considered to be due to the following reason.

That is, in the batteries (A ₁ ) to (A ₈ ) of the present invention, since an oxide layer is present on the surface of the zinc alloy, current concentration is reduced, electrodeposition becomes uniform, and charging of zinc oxide in contact with the zinc alloy is performed. Efficiency can be improved. Therefore, full charge than having no surface oxide layer (X) and the battery is delayed, Zn (OH) ₄ ^2- reduction reactions at the negative electrode surface as a dendrite cause is believed to be due to be inhibited.

In particular, the battery life in which the mixture of indium and thallium (A ₇ ) and the battery in which indium, thallium and gallium are mixed (A ₈ ) have improved cycle life as compared with the battery in which only indium is mixed (A ₁ ). I have.

This is considered to be due to a synergistic effect of the added elements.
That is, in the case of indium alone, repetition of the charge / discharge cycle causes dissolution and uneven distribution of indium in the electrolytic solution. However, when thallium or gallium is added, dissolution of indium is suppressed, and polarization is caused by the added element. Is increased, and the current distribution at the time of charge / discharge is made uniform, so that it is considered that the charge / discharge reaction becomes uniform.

However, when the additive element is single, indium is most preferable.

In the above example, the wet oxidation method is used to oxidize the surface of the zinc alloy, but it has been confirmed that the same effect can be obtained by using the dry oxidation method.

Advantageous Effects of the Invention As described above, according to the present invention, since the additive is uniformly distributed inside the zinc alloy particles and in the surface zinc oxide layer, elution of the negative electrode along with the progress of the charge / discharge cycle, deformation can be suppressed. In addition, passivation of the zinc active material during discharge is suppressed. In addition, dendrite growth can be prevented by the surface oxide layer, and self-discharge can be suppressed. From these facts, there is an effect that the cycle characteristics of the alkaline zinc storage battery can be dramatically improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an alkaline zinc storage battery of the present invention, and FIG.
The figure shows the cycle characteristics of the batteries (A ₁ ) to (A ₄ ) of the present invention and the battery (X) of the comparative example, and FIG. 3 shows the (A ₅ ) of the present invention.
A battery ~ (A ₈₎ cycle characteristic diagram of (X) cell of the battery and the comparative example. 1 ... a negative electrode, 2 ... a positive electrode, 3 ... a separator.

Claims (1)

(57) [Claims] 1. A method for producing an alkaline zinc storage battery having a positive electrode, a negative electrode mainly composed of zinc, and an alkaline electrolyte, wherein at least one selected from the group consisting of indium, thallium, gallium, tin, bismuth and lead. A method for producing an alkaline zinc storage battery, comprising: forming a zinc alloy particle containing the above-described additive element; and forming a zinc oxide layer on the surface of the zinc alloy particle.