JPH09204930A - Nickel hydrogen storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the performance deterioration with the lapse of time of a nickel hydrogen secondary battery using a hydrogen storage allow powder having a composition containing aluminum in a negative electrode. SOLUTION: In a nickel hydrogen secondary battery using a hydrogen storage alloy powder having a composition containing aluminum in a negative electrode, aluminum hydroxide or aluminate (xM2 O.yAl2 O3 .H2 O) is added to an electrolyte or the negative electrode. Thus, the capacity deterioration with the lapse of time can be prevented, and the reason is that it is assumed that the added aluminum hydroxide or aluminate is dissolved in the electrolyte and the aluminic acid ion is present in a form such as Al(OH)4 (H2 O)<2-> , Al(OH)6 (H2 O)<3-> . Therefore, the Al in the hydrogen storage alloy powder is prevented from being eluted to the alkaline electrolyte in the form of aluminic acid ion, and the capacity deterioration with the lapse of time by the pulverization progress or reduction in reactivity by the lack of Al in the hydrogen storage alloy powder can be prevented.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a nickel-metal hydride secondary battery.

[0002]

2. Description of the Related Art For example, a hydrogen storage alloy electrode used as a negative electrode of a nickel metal hydride battery is conventionally formed by applying a paste formed by mixing a hydrogen storage alloy powder with a binder onto a metal current collector. Have been. As the hydrogen storage alloy, some of Ni in LaNi ₅ and MmNi ₅ , Co,
It is common to substitute Al and Mn to suppress pulverization (disintegration) and improve the life.

Further, the hydrogen storage alloy powder contains Cu, Ni and C.
It is possible to deposit a plating film such as o or a PTFE film to suppress the oxidation, corrosion and pulverization of the film, for example, Japanese Patent Laid-Open No. 6-163.
No. 072 and Japanese Patent Laid-Open No. 6-223824.

[0004]

However, since the hydrogen-absorbing alloy powder itself contacts the gas-solid-liquid three-phase interface to carry out the battery reaction, the hydrogen-absorbing alloy powder can be applied to the plating film or the PTFE film. Nevertheless, it is difficult to prevent oxidation and corrosion because it comes into contact with an electrolytic solution composed of an aqueous solution of a strong alkali (alkali metal hydroxide) and also with oxygen during overcharge. On the other hand, the inventors took out a hydrogen storage alloy from a battery whose capacity decreased by repeating charge and discharge,
As a result of quantitative analysis of alloying elements, it was found that Al was remarkably reduced as compared with other elements constituting the hydrogen storage alloy.

Namely, the Al of the hydrogen storage alloy powder, in contact with the electrolyte solution comprising strong alkali aqueous solution aluminate ions _{Al (OH) 4 (H 2} O) 2 -, Al (OH)
₆ (H ₂ O) ^3- becomes dissolved in the electrolyte, and as a result,
It is presumed that there is a problem that a decrease in the amount of Al in the hydrogen storage alloy powder causes a decrease in the capacity of the hydrogen storage alloy powder.

The present invention has been made in view of the above problems, and a solution thereof is to prevent deterioration of performance of a nickel-hydrogen secondary battery using a hydrogen-absorbing alloy powder having a composition containing aluminum for a negative electrode with time. It should be an issue.

[0007]

The battery according to claim 1 is a nickel-hydrogen secondary battery using a hydrogen storage alloy powder having a composition containing aluminum for a negative electrode, and aluminic acid or a salt thereof (xM ₂ O.yAl ₂ O). ₃ · H ₂ O) was added to the electrolyte or the negative electrode. According to the experiment, it was possible to prevent the capacity deterioration over time.

Assuming the reason for this, the added aluminum hydroxide or aluminate is dissolved in the electrolytic solution, and the aluminate ion in the electrolytic solution is Al (OH) ₄ (H
₂ O) ₂ ^-, is estimated to be present in the _{Al (OH) 6 (H 2} O) 3- in these ways. Therefore, Al in the hydrogen storage alloy powder is prevented from being eluted in the form of aluminate ions into the alkaline electrolyte, and pulverization progresses due to lack of Al in the hydrogen storage alloy powder and deterioration of reactivity over time. It seems that capacity deterioration can be prevented.

According to the battery of claim 4, in the battery according to any one of claims 1 to 3, the amount of aluminum contained in aluminum hydroxide or aluminate is 0.1 with respect to the electrolytic solution used. The concentration is set to ˜1 wt%. If the amount of aluminum contained in aluminum hydroxide or aluminate is less than this, there is a problem that the effect of suppressing the capacity decrease due to charge and discharge cycles is reduced, and if it is more than this, the battery discharge characteristics decrease and self-discharge increases. The problem arises.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described based on the following examples. (Example) composition MmNi _3.6 Co _0.75 Al _0.3 Mn
Hydrogen storage alloy powder of _0.35 (La / Mm = 0.6) was mechanically pulverized to 100 mesh or less, and hydrogen storage alloy powder was immersed in 6NKOH aqueous solution at 60 ° C. for 24 hours to alkali-etch the alloy surface and wash with water. Then, it was dried (in air) to form a hydrogen storage alloy powder. This powder and MC (carboxymethyl cellulose) aqueous solution are kneaded to form a paste, the paste is filled in one foamed nickel current collector, dried at 70 to 80 ° C., and roll pressed to produce a hydrogen storage alloy electrode. did.

The hydrogen storage alloy electrode thus obtained was combined with a positive electrode made of a paste type nickel electrode through a separator made of a polypropylene nonwoven fabric to form an electrode unit.
A 2.3 ml solution of aluminum hydroxide dissolved in a KOH aqueous solution having a specific gravity of 1.28 as an electrolytic solution was injected into a battery containing the above electrode unit, and an AA size cylinder having a nominal capacity of 1100 mAh was sealed. Type battery (Example product 1) was constructed.

Next, a KOH aqueous solution having a specific gravity of 1.28 was added to 2.
Only 3 ml was injected into the battery containing the above electrode unit to form an AA size cylindrical sealed battery (Comparative Example 1 product) having a nominal capacity of 1100 mAh. Next, after making the hydrogen storage alloy powder 100 mesh or less, electroless plating of Ni 5 parts by weight with respect to the hydrogen storage alloy powder 95 parts by weight was carried out in the same manner as Comparative Example Product 2 except that the AA size cylindrical sealed battery (Comparative Example Two
Commodities). (Test) The above three types of batteries are charged at 0.1 C for 12 hours and discharged at 0.2 C to 1.0 V by carrying out 600 to 700 charge / discharge cycles to maintain the discharge capacity (discharge capacity / peak discharge). Capacity) was determined.

The product of this example showed almost no sudden drop in capacity retention rate even after 700 cycle tests, and had a larger capacity than the plated product (Comparative Example 2 product). As described above, according to this example, the cycle life could be extended by an extremely simple method of adding aluminum hydroxide. (Modification) In the above-mentioned examples, aluminum hydroxide was added to the electrolytic solution, but it is also possible to add or apply it to the paste for forming the negative electrode or the completed negative electrode. Instead of aluminum hydroxide, aluminate is used. Of course, lithium salt, sodium salt, potassium salt, or a mixture thereof can be used.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing changes in capacity retention rates of batteries of a product of this example and a product of a comparative example.

Claims (4)

[Claims] 1. A negative electrode formed by depositing a hydrogen storage alloy powder having a composition containing aluminum on a metal current collector, a positive electrode containing nickel as a main component, and an electrolytic solution containing an aqueous solution of an alkali metal hydroxide. A nickel-hydrogen secondary battery comprising: a nickel-hydrogen secondary battery, wherein aluminum hydroxide or an aluminate is added to the electrolytic solution or the negative electrode. 2. The nickel-hydrogen secondary battery according to claim 1, wherein the salt includes at least one of Li salt, Na salt, and K salt. 3. The nickel-hydrogen secondary battery according to claim 1, wherein the salt contains an alkali metal of the same kind as the electrolytic solution. 4. The amount of aluminum contained in the aluminum hydroxide or aluminate is 0.1 to the amount of the electrolytic solution.
The nickel-hydrogen secondary battery according to claim 1, which has a concentration of 1 wt%.