JP3094618B2 - Manufacturing method of hydrogen storage alloy electrode for alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a hydrogen storage alloy electrode for an alkaline storage battery.

[0002]

2. Description of the Related Art Alkaline storage batteries widely used as various power sources can be expected to have high reliability, and small batteries can be used for various portable equipment and large batteries can be used for industrial purposes for any reason. Have been.

In most cases, a nickel electrode is used as a positive electrode in this alkaline storage battery. The characteristics have been improved from the pocket type to the sintering type, and the sealing has been made possible and the use has expanded.

On the other hand, at present, a cadmium electrode is mainly used as a negative electrode, but a nickel-hydrogen storage battery using a hydrogen storage alloy electrode has been attracting attention in order to achieve a higher energy density, and many proposals have been made on a manufacturing method and the like. I have. Improvements in rapid charge / discharge properties as well as high energy density are being pursued.

For example, there is known a technique of forming a porous metal layer by plating the surface of particles with nickel or copper in order to improve the hydrogen storage alloy powder, particularly the oxidation resistance, and the utilization and moldability. Also, nickel,
Addition of copper, nickel oxyhydroxide powder, immersion in an alkaline solution, and the like have been proposed.

In addition, when applied to a sealed type, it has been attempted to add a fluororesin or a catalyst to improve the absorption of oxygen gas from the positive electrode during charging and hydrogen gas which may be generated during overcharging. ing.

[0007]

As a method of producing a hydrogen storage alloy electrode, a method of sintering an alloy powder and filling the alloy powder into a porous body having a two-dimensional or three-dimensional structure such as foamed, fibrous, or punched metal is used. And a paste type of coating.
In any case, there is room for improvement particularly in the discharge characteristics at the beginning of the charge / discharge cycle. Particularly, in the case of an alloy containing an AB ₂ Laves phase based on Zr—Ni as a hydrogen storage alloy, the capacity eventually becomes high, but the initial activation is a problem. If the acceptability of the initial charge is poor, the sealed type battery becomes a battery of the negative electrode rule, causing problems in high-rate discharge characteristics, self-discharge, life, and the like.

An object of the present invention is to provide a method for manufacturing a hydrogen storage alloy electrode for an alkaline storage battery, which has improved initial discharge characteristics and high-rate discharge characteristics.

[0009]

In order to achieve this object, a method for producing a hydrogen storage alloy electrode for an alkaline storage battery according to the present invention comprises:
AB ₂ L based on hydrogen storage alloy, especially Zr-Ni
The aves phase powder is mixed with a nickel salt solution, immersed in an alkaline solution, washed with water, and used as a hydrogen storage alloy electrode to conduct electricity in the oxidation direction. In this case, the energization in the oxidation direction is set to the extent that the generation of nickel oxyoxide is completed.
Preferably, the alkaline solution contains lithium hydroxide. Further, the present invention is effective for removing a metal or an oxide layer which does not require an alkali treatment of an alloy or for modifying the surface. Since the present invention involves immersion in an alkali during this step, for example, alkali immersion such as immersion at a high temperature is used. May be used in combination.

[0010]

When an AB ₂ Laves phase based on Zr—Ni is used as a hydrogen storage alloy, its initial properties are rather poor. Therefore, it is necessary to improve additives, particle surfaces, and affinity with hydrogen for improvement. And so on. Among these, there is nickel oxyhydroxide as an additive. However, particularly when the AB ₂ Laves phase based on Zr—Ni was used, even if this powder was added to the alloy, the effect was somewhat to some extent. However, when nickel oxyoxide is formed on the surface of the alloy particles from a nickel salt solution as in the present invention, the contact with the surface of the hydrogen storage alloy is much more than mere mixing and changes the surface of the hydrogen storage alloy like a kind of plating Will be. When lithium hydroxide is contained in the alkaline solution, nickel oxyhydroxide is doped with lithium, so that the conductivity is improved.

In other words, it is important to form nickel hydroxide on the surface of the hydrogen storage alloy, which is proposed above, rather than simply mixing it, by forming nickel hydroxide on the surface of the hydrogen storage alloy, and converting it to nickel with a reducing agent. This is the same as the improvement in the initial activity that could not be obtained by simply adding nickel powder. In the present application, the operation is simple because a reducing agent is not required and only energization in the oxidation direction is required.

[0012]

EXAMPLES The following embodiment method for producing hydrogen-absorbing alloy electrode for an alkaline storage battery of the present invention, AB ₂ as the hydrogen storage alloy
ZrMn _0.5 Cr _0.2 V, one of the Laves phase alloys
_A nickel nitrate solution saturated at 30 ° C. was added to the powder of _0.1 Ni _1.2 , mixed and dried at 60 ° C., and then 45 wt.
C. for 10 minutes. After washing with water and drying, a 2% by weight polyvinyl alcohol solution was added to form a paste, which was filled into a foamed nickel plate having a porosity of 95% and a thickness of 1.0 mm, and then pressed. This electrode was cut into a width of 33 mm and a length of 210 mm, and a lead plate was attached by spot welding.

A known foamed nickel electrode and a hydrophilically treated polypropylene nonwoven fabric separator were used as counter electrodes. 25% aqueous caustic potassium solution with specific gravity of 1.25 as electrolyte
g / L of lithium hydroxide was dissolved and used to form a sealed nickel-hydrogen storage battery. The battery was a SubC type. The nominal capacity is 3.0 Ah. The capacity of the negative electrode with respect to the positive electrode was set to 150%.

A current was applied to the battery thus obtained in the discharge direction (oxidation) at 200 mA for 1.5 hours. This battery is designated as A.

Next, for comparison, a battery prepared by adding a separately prepared nickel oxyhydroxide powder to the hydrogen storage alloy powder and omitting the energization (oxidation) in the discharge direction after the battery construction was added as B, and A and B were added. In both cases, normal formation was performed.

The initial discharge voltage and capacity during chemical formation were compared. When constant current charging of 150% of the capacity at 0.1 C (10 hour rate) and constant current discharging at 2.0 A to 0.9 V were repeated, A had an average voltage of 1.25 V and a discharge capacity of 3 cycles. Thereafter, it was almost constant and was 2.95 to 3.00 Ah. However, in the case of B, the average voltage was 1.23 V, and 10 cycles were required until the discharge characteristics improved and became almost constant.

After completion of the formation, 10 cells were used for each of the two batteries, and the rapid discharge characteristics were compared. When the ambient temperature was set to 30 ° C. and the battery was charged at 135% of capacity and then discharged at 1 C, the capacity retention ratio was 94 to 97% of the nominal capacity in A, whereas B was 94 to 97% of the nominal capacity.
Was 87 to 90%, and A was excellent. In the 2C discharge, the capacity retention ratio was 89-91% in A, whereas in B it was B
Was 78 to 82%, and A was also excellent.

[0018]

As is apparent from the above description of the embodiment, according to the method of manufacturing a hydrogen storage alloy electrode for an alkaline storage battery of the present invention, after adding a nickel salt solution to a hydrogen storage alloy powder,
An electrode is manufactured by immersing it in an alkaline solution to form a nickel-oxide-coated hydrogen storage alloy powder. After the battery has been constructed, it can be energized in the discharge (oxidation) direction to improve the initial characteristics, utilization, and high discharge characteristics. Become.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-269953 (JP, A) JP-A-2-263944 (JP, A) JP-A-4-1799053 (JP, A) Patent 2932711 (JP, A) B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) N01M 4/24-4/26 N01M 4/38

Claims (4)

(57) [Claims] 1. A method for manufacturing a hydrogen storage alloy electrode for an alkaline storage battery, wherein a nickel salt solution is added to and mixed with a hydrogen storage alloy powder, immersed in an alkali solution and washed with water. Law. 2. The method for producing a hydrogen storage alloy electrode for an alkaline storage battery according to claim 1, wherein the energization in the oxidation direction is such that generation of nickel oxyoxide is completed. 3. The method for producing a hydrogen storage alloy electrode for an alkaline storage battery according to claim 1, wherein the alkaline solution contains lithium hydroxide. 4. The method for producing a hydrogen storage alloy electrode for an alkaline storage battery according to claim 1, wherein the hydrogen storage alloy contains an AB ₂ Laves phase based on Zr—Ni.