JPH04110403A - Manufacture of hydrogen storage alloy electrode - Google Patents

Abstract

PURPOSE:To manufacture a hydrogen storage alloy electrode having excellent initial stage characteristic and rapid electric charging characteristic by pulverizing or pulverizing and preserving a hydrogen storage alloy cast ingot in water while holding this to hydrogen generating electric potential to manufacture hydrogen storage alloy powder. CONSTITUTION:The hydrogen storage alloy cast ingot is pulverized or pulverized and preserved in the water while being held to the hydrogen generating electric potential to manufacture the hydrogen storage alloy powder. As the concrete method for holding the hydrogen storage alloy cast ingot to the hydrogen generating electric potential, before pulverizing the hydrogen storage alloy cast ingot in the water, the hydrogen is stored into the alloy cast ingot or this ingot is beforehand held under electric charge condition or pulverized while being held under electric charge condition, etc. Further, in the above water, beforehand, metal constituting the above hydrogen storage alloy or oxide thereof or hydroxide thereof is added, or metal, metal oxide or metal hydroxide generating oxidation-reduction reaction with more noble electric potential than oxidation-reduction potential of the above metal is added or the above water is desirable to use as buffer solution holding the pH to the constant. By this method, development of hydroxide layer developed on surface of the hydrogen storage alloy powder is controlled and the initial characteristic and the rapid electric charge characteristic in the electrode can be drastically improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a hydrogen storage alloy electrode used in a metal-hydrogen alkaline storage battery.

In recent years, metal-hydrogen alkaline storage batteries have been attracting attention as a new type of alkaline storage battery to replace the Ni-Sigal 1'mium battery, which can have a higher energy density than the Ni-Sigal 1'mium battery. A hydrogen storage alloy is used as the negative electrode of this battery.

By the way, the method for producing the above-mentioned hydrogen storage alloy generally involves two steps: melting the hydrogen storage alloy material, producing a hydrogen storage alloy ingot, and pulverizing the hydrogen storage alloy ingot in water. The hydrogen-absorbing alloy powder is prepared by the following steps:

However, when the hydrogen storage alloy ingot is crushed in water as in the conventional manufacturing method described above, some of the hydrogen storage alloy components are eluted into the water, and the aqueous solution becomes weakly alkaline (p l-18 to 1).
0). In such an alkaline solution, most of the metals constituting the hydrogen storage alloy become hydroxides <Iη
Since the hydrogen storage alloy is in the oxidation-reduction potential, the parts that are kept at a potential equal to or more noble can become active sites and form a hydroxide film on the surface of the hydrogen storage alloy. become. As a result, there was a problem in that initial characteristics and rapid charging characteristics deteriorated.

The present invention was made in view of the current situation, and is the first 7
The object of the present invention is to provide a method for manufacturing a hydrogen storage alloy electrode that can improve 11 characteristics and rapid charging characteristics.

In order to achieve the above object, the present invention crushes or crushes and stores a hydrogen storage alloy ingot in water while maintaining it at a hydrogen generation potential. The method is characterized by comprising a step of producing a hydrogen storage alloy powder.

There are three specific methods for maintaining the hydrogen storage alloy ingot at a hydrogen generation potential:

■Before crushing the hydrogen-absorbing alloy ingot in water, the alloy ingot is made to absorb hydrogen.

■Before crushing the hydrogen storage alloy ingot in water, keep the alloy υf ingot in a charged state.

■While maintaining the hydrogen storage alloy ingot in a charged state at J=6, crush the alloy ingot.

In addition, in the method for manufacturing a hydrogen storage alloy electrode, which includes the step of crushing or crushing and storing a hydrogen storage alloy ingot in water, the water contains in advance a hydrogen storage alloy constituting the hydrogen storage alloy, or the metal in step 1. The oxides and hydroxides cooperate ■]
It is characterized by being

Specifically, when L a N i is used as the hydrogen storage alloy, Ni may be added to water.

Further, in the method for manufacturing a hydrogen storage alloy electrode, which includes the step of crushing or crushing and storing a hydrogen storage alloy ingot in water, the water contains oxidized hydroxides of metals constituting the hydrogen storage alloy in advance. oxidation at a potential more noble than the reduction potential,
It is characterized by the addition of a metal, metal oxide, or metal hydroxide that causes a reduction reaction.

Specifically, when using aN + 5 as a hydrogen storage alloy, Cu2O or the like is added to water (just 1 liter is sufficient).

Furthermore, the present invention is characterized by having a step of producing a hydrogen-absorbing alloy powder by pulverizing or pulverizing and storing the hydrogen-absorbing alloy ingot in a buffer solution that keeps the pH constant.

As in the manufacturing method of the first invention, the hydrogen absorbing alloy ingot is crushed in water while maintaining the hydrogen generation potential b = Ni and CO, which are the main components of the hydrogen absorbing alloy, are Ni (r, i) does not enter the nail region 1 where it becomes hydroxide.
etc. remain in a metallic state and become a hydrogen-absorbing alloy powder. Therefore, there are sufficient active sites of Ni and Co on the alloy surface.

As in the above-mentioned second and third inventions, 1. A metal or metal that undergoes an oxidation or reduction reaction at a potential equal to or nobler than the oxidation-reduction potential of the metal hydroxide constituting the hydrogen storage alloy when crushed or stored in water; If the oxide or metal hydroxide is added to the water in advance, there will be sites other than the surface of the hydrogen storage alloy that will become active sites. As a result, the hydroxide of the alloy component will precipitate on the surface of the input metal, etc., so it is possible to suppress the formation of hydroxide on the surface of the hydrogen storage alloy powder. There will be sufficient active sites on the surface.

As in the fourth invention, when the hydrogen storage alloy ingot is crushed in a buffer solution in which the aqueous solution is kept constant, Ni and CO, which are the main components of the hydrogen storage alloy, become hydroxides and become metallic. In this state, it becomes a hydrogen-absorbing alloy powder. Therefore, 1. There are enough active points on the alloy surface.

) (↓J 1 line - The first embodiment of the present invention is revealed in FIGS. 1 and 2,
This will be explained below.

[Example I]

FIG. 1 is a cross-sectional view of a cylindrical nickel-hydrogen alkaline storage battery using hydrogen storage alloy electrodes produced according to the present invention, showing a positive electrode 1 made of sintered nickel, a negative electrode 2 containing a hydrogen storage alloy, and both positive and negative electrodes. 12 and a separator 3 inserted between the electrodes J! Y4 is spirally wound. This electrode group 4 is arranged in an exterior casing 6 which also serves as a negative electrode terminal, and the exterior end 6 and the positive and negative electrodes 2 are connected by a conductive tab 5 for the negative electrode. A sealing body 8 is attached to the upper opening of the exterior can 6 via a backing 7, and a coil spring 9 is installed inside the sealing body 8. This coil spring 9 is configured so that when the internal pressure inside the battery rises abnormally, it is pressed in the direction of the arrow and the internal gas is released into the atmosphere.

Furthermore, the positive electrode 1 is connected to the positive electrode 1 by a conductive tab 10 for the positive electrode.

Here, a cylindrical nickel-metal hydride alkaline storage battery with a ``Fuji'' structure was fabricated as follows.

First, commercially available 1. After weighing a and Ni so that the elemental ratio is 1:5, melting is performed in a high frequency melting furnace to create a molten metal, and by further cooling the molten metal, L
A hydrogen storage alloy ingot represented by a N i was prepared. Next, this hydrogen storage alloy ingot was allowed to store 10 cc of hydrogen per 1g6 of the alloy.

Thereafter, the ingot of the hydrogen storage alloy was crushed in water for 4 hours so that the particle size of the ingot was 50 μm or less.

At this time, water was added at 5℃ for 11g of hydrogen storage alloy ingot.
It is set so that

After this, PT as a binder is added to the hydrogen storage alloy powder.
FE (polytetrafluoroethylene) powder 5w45%
Add and knead to create Base I.

Furthermore, this paste was pressed onto both sides of a current collector made of punched metal to produce a negative electrode 2.

Next, the negative electrode 2 and the sintered two-layer positive electrode 1 having a sufficiently larger capacity than the negative electrode 2 were wound together with a separator 3 made of nonwoven fabric interposed therebetween, to produce an electrode group 4. Thereafter, this electrode group 4 was inserted into the exterior end 6, and after a 30% by weight KOH aqueous solution was poured into the exterior end 6, the exterior end 6 was sealed to produce a cylindrical Ninkeru hydrogen storage battery. did. In addition, 1' of the battery thus produced
! I! The theoretical capacity is 1.000 mA, h.

The battery prepared in the above manner is hereinafter referred to as (A1) battery.

[Example ■] Example I described in - except that the treatment before crushing the hydrogen storage alloy ingot was not to absorb hydrogen but to pre-charge the hydrogen storage alloy ingot. A battery was fabricated in the same manner as above. Note that the preliminary charge amount is 20 mA per 1 g of hydrogen storage alloy.

The battery thus produced is hereinafter referred to as (A) battery.

(Example ■[] A battery was produced in the same manner as in Example ■ above, except that the hydrogen storage alloy ingot was not subjected to any pre-pulverization treatment and was crushed while applying a current of -5 rn△ to 1 g of hydrogen storage alloy. I made the saw.

The battery thus produced is hereinafter referred to as an (All) battery.

[Comparative example]

A battery was produced in the same manner as in Example 2 above, except that the hydrogen storage alloy ingot was not subjected to any pre-pulverization treatment (other than pulverization).

The battery thus produced is hereinafter referred to as the (X) battery.

〔experiment〕

” (A1) Battery by the manufacturing method of the present invention ~ (△,)
The oxygen concentration, initial capacity, and battery internal pressure of the battery and the battery (X) manufactured by the manufacturing method of Comparative Example were measured, and the results are not shown in Table 1 below. In addition, if the capacity is υ1, the charging current is 0.
This is the capacity after repeating the cycle of charging at 3C for 4 hours and discharging at /A 0.3C to a final discharge voltage of 10cm five times. In addition, the battery internal pressure is the pressure when one electric current is applied to the IC.

Table 1 Regarding 2-hour light and alloy oxygen concentration As shown in Table 1 above, (A
1) Battery - (A,) battery has a very low value of 0.132 to 0.35%, whereas the comparative example (X) battery manufactured using the manufacturing method has a high value of 50%. is recognized.

As shown in Table 1 of ``Regarding the initial 1u1 capacity'', (A1) battery to (A,) battery is very large, 20 mAh, while (X ) 950 m^h with batteries
The fact that it is so small is tolerable.

・About battery internal pressure" As shown in Table 1, (/\1) battery ~ (△, l
) battery has a very low value of 5.1 to 5.3al, mtea, while (X) battery has ]5], at
, m.

As shown in FIG. 2, the (A1) to (A,i) batteries of the present invention are superior in terms of alloy oxygen concentration, initial capacity, and battery internal pressure. In the range of 8 to IO, the hydrogen generation potential (shown in the figure) is N]
does not become a hydroxide but is in the state of metal N. Therefore, it is thought that the reason is that if the hydrogen-absorbing alloy ingot is crushed while maintaining the hydrogen-generating potential as described above, Ni(○■1)2 will not be generated on the surface of the hydrogen-absorbing alloy powder. It will be done.

Part 1 [Example ■] Instead of treating the hydrogen storage alloy ingot before crushing it, we added 100g of Ni(OH)2 to the water to be crushed in advance. A battery was produced in the same manner as in Example I of the first example except for the treatment.

The battery thus produced is hereinafter referred to as (B1) battery.

[Troublesome ability ■] N ] (01 () Instead of 2, Cu, 0 to 10
A battery was produced in the same manner as in Example 2 above, except that 0 g was added.

The battery thus produced is hereinafter referred to as a (B2) battery.

[Comparative Example] As a comparative example, the battery (X) of the first example is used.

[Experiment] The oxygen concentration, initial capacity, and battery internal pressure of the (B) battery (B2) battery manufactured by the manufacturing method of Ichihiki's invention and the (χ) battery manufactured by the manufacturing method of the comparative example were measured. The results are shown in Table 2 below. The experimental conditions were the same as those of the first embodiment.

Table 2 - Alloy Oxygen Concentration As shown in Table 2 above, (B
1) battery and (B2) battery, each has a value of 0.77.0.
It is recognized that the ratio is low at 65%, whereas it is high at 1.5% in the battery (X) produced by the manufacturing method of the comparative example.

As shown in Table 2 above regarding the initial jUl capacity, (B1) battery, (B,)
The batteries are 990 and 10 (17mAh), which are larger, while the (X) batteries are 950mA.
It is recognized that the value is smaller than Ah.

As shown in Table 2 of "About battery internal pressure", (B1) battery, (B,
) battery, the values are 7.7, 6.3 alm, respectively, which are lower, whereas for the (X) battery], 5.1a
It is acceptable that the values are as high as l and m.

As shown in FIG. 3, the (B1) battery and (B2) battery of the present invention are excellent in terms of alloy oxygen a degree, period capacity, and battery internal pressure. In the range of (pH 9 in the figure), CIi *
C: E/V of u 20 is in the area of Ni(○l-1)2. Therefore, if Cu20 etc. are placed in the water to be crushed in advance as described above, the generated Ni(○J1)
This is thought to be due to the fact that the formation of N i (OH) 2 on the surface of the hydrogen storage alloy powder is suppressed because 2 precipitates on the surface of Cuz O.

3rd ΩU- (Example I) The hydrogen storage alloy ingot was not treated before being crushed, and the crushing solution was a buffer solution (0, I) instead of water.
A battery was produced in the same manner as in Example I of the first example, except that N acetic acid: 0.1 moff/12 sodium acetate (4:1, p I-T-4) was used.

The battery thus produced is hereinafter referred to as a (C4) battery.

(Example ■) Except for using 0.1N acetic acid + O, imoρ/℃ strium acetate-1:2 (pH-5) as the buffer solution.
A battery was prepared in the same manner as in Example I of Seihi.

The battery produced in this manner is hereinafter referred to as a (C2) battery.

[Example ■] As a buffer solution, 0. ]N vinegar M: 0.1. mo℃
/! A battery was prepared in the same manner as in Example I above, except that sodium acetate-1:16 (pt-6) was used.

The battery thus produced is hereinafter referred to as a (C3) battery.

[Example ■] As a buffer solution, 0.03 molar! ,/f! ,'
A battery was prepared in the same manner as in Example I above, except that 0.03 mo of potassium dihydrogen phosphate, +2/1 sodium hydroxide, 1:2 (p l (=7)) was used.

The battery thus produced is hereinafter referred to as a (C4) battery.

[Example IV] As a buffer solution, 0,03mo°C/! Potassium dihydrogen phosphate di0.03mo, e/ffi Sodium hydroxide-
A battery was prepared in the same manner as in Example I above, except that 1:16 (pH-8) was used.

The battery thus produced is hereinafter referred to as a (C1) battery.

[Comparative example]

As a comparative example, the battery (X) of the first embodiment is used.

〔experiment〕

” (CI) battery by the manufacturing method invented by Shohiki ~ (C5
The oxygen concentration, capacity per cutting edge, and internal pressure of the battery were measured for the battery (X) manufactured by the manufacturing method of Comparative Example, and the results are shown in Table 3 below. The experimental conditions were the same as those of the first embodiment.

Table 3: Alloy Oxygen Concentration As shown in Table 3, the manufacturing method of the present invention (
For C1) batteries to (C5) batteries, 0.35 to 0.39%
, which is extremely low, whereas it is recognized that the (χ) battery produced by the manufacturing method of the comparative example has a high value of 1.50%.

- Regarding the initial capacity, as shown in Table 3 above, the (C,) to (C,) batteries have a very large initial capacity of 1012 to 1020 mAh, while the (X) battery has a very large initial capacity. 950mAh
It is recognized that it is small.

- Regarding battery internal pressure, as shown in Table 3 above, for (C+) to (C6) batteries, it is 5.1 to 5.5 al:m, which is very low, whereas (X) For batteries, 15, ], a
I can't help but notice that I'm getting taller.

As described above, the (C,) battery to (C6) battery of the present invention has problems in terms of alloy oxygen concentration, initial) u1 capacity, and battery internal pressure. 1
This is because Ni and Co, which are the main components of the hydrogen storage alloy, do not turn into hydroxides during crushing, but instead maintain their metallic state and become hydrogen storage alloy powder. Conceivable.

[Other matters]

■''-Note: In the three examples, explanations were given using the crushing of a hydrogen-absorbing alloy ingot, but Tuft L.? l! ,are doing.

■In the second embodiment above, N is used as the metal to be thrown into the water.
Although 1(OF+)2 and Cu2O are used, the present invention is not limited thereto, and various metals, metal oxides, and metal hydroxides can be used depending on the type of hydrogen storage alloy.

(2) The buffer solution used in the third embodiment is not limited to two series, but for example, a mixed solution of potassium hydrogen phthalate and thorium hydroxide (pH 4~
6), a mixed solution of potassium dihydrogen citrate and thorium hydroxide (p I-14 to 6),
A mixed solution of potassium dihydrogen citrate and sulfuric acid and zolium tetraborate (pH can be set to 4 to 6), a mixed solution of potassium dihydrogen phosphate and sulfuric acid to zolium tetraboric acid (pH 6 to 8)
), a mixed solution of dihydrogen phosphate and citric acid (p
(Can be set to Ei to 8).

■Although a cylindrical storage battery is used in the above three embodiments Q, the present invention is also applicable to a flat storage battery.

As explained above, according to the present invention, it is possible to suppress the formation of a hydroxide layer on the surface of the hydrogen-absorbing alloy powder, thereby dramatically improving the initial characteristics and rapid charging characteristics. It has the effect of being able to improve things.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a cylindrical nickel-metal hydride alkaline storage battery using the electrode of the present invention, and Figure 2 is a sectional view of a Ni-1-1,0 series (
Figure 3 is a graph showing the relationship between pH and E/V at 25°C).
pH and E/V in u-+-120 system (25°C)
It is a graph showing the relationship between 1...Positive electrode, 2...Electrode, 3...Separator. Patent applicant: Sanyo Electric Co., Ltd.

Claims (4)

[Claims] (1) While maintaining the hydrogen storage alloy ingot at a hydrogen generation potential,
A method for producing a hydrogen storage alloy electrode, comprising the step of producing a hydrogen storage alloy powder by crushing or crushing and storing in water. (2) A method for producing a hydrogen storage alloy electrode comprising the step of crushing or crushing and storing a hydrogen storage alloy ingot in water, wherein the water contains in advance a metal constituting the hydrogen storage alloy,
Or a method for producing a hydrogen storage alloy electrode, characterized in that an oxide or hydroxide of this metal is added. (3) A method for producing a hydrogen storage alloy electrode comprising the step of pulverizing or pulverizing and storing a hydrogen storage alloy ingot in water, in which the water is preliminarily treated with hydroxides of metals constituting the hydrogen storage alloy. A method for producing a hydrogen storage alloy electrode, characterized in that a metal, metal oxide, or metal hydroxide that causes an oxidation or reduction reaction at a potential higher than the redox potential is added. (4) A method for producing a hydrogen storage alloy electrode, which comprises the step of producing a hydrogen storage alloy powder by pulverizing or pulverizing and storing a hydrogen storage alloy ingot in a buffer solution that maintains a constant pH.