JP2001196092A - Sealed nickel-hydrogen battery and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cycle characteristics of a nickel-hydrogen battery employing a centered cubic hydrogen storage alloy for the negative pole. SOLUTION: The closed nickel-hydrogen battery provides a negative pole with hydrogen storage alloy particles. The particles are those of the centered cubic hydrogen storage alloy. On at least a part of the surface, there is a Ni- diffused layer containing a centered cubic phase similar to TiNi. In addition, there is at least one element of lithium and sodium inside the battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed nickel-metal hydride storage battery using a hydrogen storage alloy capable of reversibly electrochemically storing and releasing hydrogen, and a method for manufacturing the hydrogen storage alloy electrode.

[0002]

2. Description of the Related Art A nickel-metal hydride storage battery using a hydrogen storage alloy capable of reversibly absorbing and releasing hydrogen for a negative electrode has a theoretical capacity density larger than that of a cadmium electrode, and does not have deformation and dendrite formation unlike a zinc electrode. Therefore, long life
Because it is pollution-free and has a high energy density,
Future development is expected. Hydrogen storage alloys currently commercialized in nickel-metal hydride storage battery, AB ₅ type (A: La, Zr, affinity of large elements with hydrogen, such as Ti, B: Ni, Mn, transition element such as Cr) of La
(Or Mm) -Ni-based multi-component alloy. However, since this alloy has a capacity close to the theoretical value and a large capacity increase cannot be expected in the future, a nickel-metal hydride storage battery using a novel hydrogen storage alloy material having a larger discharge capacity is desired.

[0003] AB_FiveLarger hydrogen storage than type alloy
Ti-V-based hydrogen storage alloys
You. A negative electrode for nickel-metal hydride storage batteries using this alloy system
For example, Ti_xV_yNi_zAlloy (JP-A-6-2286)
No. 99, JP-A-7-268513, JP-A-7-268513
-268514) has been proposed. Also,
V to improve discharge capacity and cycle characteristics_1-abcd
Ti_aCr_bM_cL _dAlloy (M is Mn, Ni, etc., L is rare earth
(Y) or the like (Japanese Patent Laid-Open No. 11-1999).
144728).

[0004]

However, Ti-
When a V-Ni-based hydrogen storage alloy is used for a negative electrode of a nickel-metal hydride storage battery, although the discharge capacity is higher than that of a La (or Mm) -Ni-based multi-component alloy, the cycle characteristics are improved and the capacity is further increased. desired. V _{1-a- bcd}
Further improvement in cycle characteristics is also desired for the Ti _a Cr _b M _c L _d alloy. An object of the present invention is to provide a sealed nickel-metal hydride storage battery having a large discharge capacity and little cycle deterioration.

[0005]

Means for Solving the Problems The inventors of the present invention aimed at improving the characteristics of the negative electrode in view of the composition of the hydrogen storage alloy and the surface treatment, and as a result of repeated studies, completed the present invention. . That is, the sealed nickel-metal hydride storage battery of the present invention includes a negative electrode made of hydrogen storage alloy particles, wherein the alloy particles are hydrogen storage alloy particles having a body-centered cubic structure, and at least a part of the surface thereof. It has a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi, and contains at least one element of Li and Na in a battery.

Here, it is preferable that at least one element of Li and Na is contained in the Ni diffusion layer. At least one element of Li and Na is
It may be contained in the electrolyte as lithium hydroxide or sodium hydroxide. In this case, the electrolyte contains at least one of lithium hydroxide and sodium hydroxide and potassium hydroxide, the concentration of potassium hydroxide is 70 wt% or more, and the specific gravity of the electrolyte is 1.20 to 1.40. Is preferred.

[0007] hydrogen-absorbing alloy having the body-centered cubic structure, formula _{V 1-abcd Ti a Cr b} M c L d (M is Mn, F
e, Co, Cu, Nb, Zn, Zr, Mo, Ag, H
f, at least one element selected from the group consisting of Ta, W, Al, Si, C, N, P, and B; L is at least one element selected from the group consisting of rare earth elements and Y; .2 ≦ a ≦ 0.5, 0.1 ≦ b ≦ 0.4, 0 ≦
An alloy represented by c ≦ 0.2 and 0 <d ≦ 0.03) is preferable.

[0008] The present invention also provides a hydrogen storage alloy particle having a body-centered cubic structure, which is nickel-plated or mixed with a nickel powder to deposit Ni on the surface of the alloy particle and then heat-treated. The present invention provides a method for producing a hydrogen storage alloy electrode for a sealed nickel-metal hydride storage battery, the method including: The heat treatment is preferably performed at a temperature of 500 to 700 ° C. in an inert gas or vacuum. The present invention provides a hydrogen storage alloy particle having a body-centered cubic structure and having, on at least a part of its surface, a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi, at least lithium hydroxide and hydroxide. By heat-treating with an aqueous alkali solution containing at least one of sodium, at least one element of lithium and sodium is converted to Ni
Provided is a method for manufacturing a hydrogen storage alloy electrode for a sealed nickel-metal hydride storage battery, the method including a step of obtaining hydrogen storage alloy particles contained in a diffusion layer. The heat treatment temperature in the alkaline aqueous solution is 80
It is preferable that the temperature is not lower than ° C.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a sealed nickel-metal hydride storage battery using a high-capacity hydrogen-absorbing alloy having a body structure of a body-centered cubic structure as a negative electrode. It is based on the discovery that the cycle characteristics of a sealed nickel-metal hydride storage battery can be improved by the action of at least one element of Li and Na on a Ni diffusion layer containing a phase having a body-centered cubic structure of is there. The effect of improving the cycle characteristics is that Li and / or Na elements enter a crystal phase having a body-centered cubic structure similar to electrochemically active TiNi, thereby distorting the crystal surface structure, or It is considered that a specific element in the crystal phase is eluted, whereby the electrochemical reaction activity on the surface is further improved, and the gas absorbing ability in the sealed battery is increased.

In order to allow at least one element of Li and Na to act on a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi, Li and N
a or at least one of Li and Na in the electrolytic solution in order to efficiently act on a phase having a body-centered cubic structure similar to TiNi on the alloy surface. It is desirable to previously treat the alloy surface with an aqueous alkaline solution containing at least one of Li and Na.

As a method for producing a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi on the surface, there are a method in which Ni is deposited on the alloy surface by plating or mixing of powder, followed by heat treatment, and a method in which mechanical treatment is performed. There is a method of physically diffusing Ni on the alloy surface such as alloying. When heat treatment is performed, 500%
An alloy powder having a desired surface structure can be obtained by heat treatment at a temperature of up to 700 ° C. If the temperature is lower than 500 ° C, Ni
Does not spread. If the temperature is higher than 700 ° C., not only Ni diffuses further into the alloy to reduce the amount of hydrogen occlusion, but also the surface phase becomes Ti ₂ Ni, so that Li or Na is acted on. Even so, the electrode characteristics deteriorate.

[0012] The hydrogen storage alloy of the parent phase may be basically an alloy containing Ti. However, in order to satisfy the hydrogen storage amount and the characteristics as a battery electrode, the constituent elements and the added amount thereof must be adjusted. The following ranges are desirable. Ni, when added to the alloy, forms a Ti-Ni-based second phase, which not only causes a corresponding decrease in the amount of hydrogen storage, but also dissolves a small amount in the main phase and causes an increase in the hydrogen equilibrium pressure. As a result, the hydrogen storage amount decreases. Therefore, by removing Ni from the composition, the hydrogen storage amount increases. Ti has a larger atomic radius than V and Cr, thereby increasing the lattice size of the alloy, lowering the hydrogen equilibrium pressure and increasing the hydrogen storage capacity. If the addition amount is 0.2 or more in atomic ratio, a remarkable effect can be seen in increasing the occlusion amount. But,
When added in an amount of 0.5 or more, the hydrogen in the alloy is stabilized due to a decrease in the hydrogen equilibrium pressure, and the hydrogen is hardly released, so that the hydrogen storage amount decreases. Therefore, it is desirable to be 0.2 or more and 0.5 or less.

[0013] Cr facilitates activation and imparts corrosion resistance in an alkaline electrolyte. In order to obtain this effect, it is necessary to add 0.1 or more in atomic ratio. However, Cr increases the hydrogen equilibrium pressure and forms a TiCr ₂ phase, so that a large amount of Cr decreases the hydrogen storage amount. In order to suppress this, the addition amount needs to be 0.4 or less. By adding a small amount of rare earth elements such as La and Ce or Y, the amount of hydrogen occlusion further increases. It is considered that these elements serve as a deoxidizing agent and remove impure oxygen in the alloy. By precipitating these elements as a second phase and making them hardly contained in the parent phase, the composition of the parent phase is hardly affected, and only the hydrogen storage amount without changing the hydrogen equilibrium pressure or the like. Can increase. Even if the addition amount of these rare earth elements and / or Y is 3 atomic% (atomic ratio 0.03) or more with respect to the mother alloy, no further improvement in the effect is recognized.

In addition to the above elements, Mn, Fe, Co, C
u, Nb, Zn, Zr, Mo, Ag, Hf, Ta, W,
Al, Si, C, N, P, and B can be added as needed. These elements change the lattice size in accordance with the atomic radius, control the hydrogen equilibrium pressure, increase the amount of hydrogen occlusion that can be used as an electrode, and reduce Mn, N
b, Mo, Ta, and Al increase Fe, C
o, Cu, Zn, Zr, Ag, Hf, W, Si, N,
P and B respectively contribute to an increase in discharge capacity and cycle life due to an increase in electrode activity. The total amount of these additives is preferably 0.2 or less. If it exceeds 0.2, a phase other than the body-centered cubic structure is precipitated, and the hydrogen storage amount decreases. V
Is an element necessary for causing the body-centered cubic structure to exist stably and increasing the amount of hydrogen occlusion, and the amount is automatically determined by the amount of other elements.

[0015] The surface of the hydrogen storage alloy particles described above includes N containing a phase having a body-centered cubic structure similar to TiNi.
Although the amount of hydrogen storage is smaller than that of the method of forming the i-diffusion layer, it is possible to produce a body-centered cubic structure similar to TiNi by simply adding Ni to a hydrogen-absorbing alloy whose crystal structure is a body-centered cubic structure. It is possible.

In order to allow at least one element of Li and Na to act on a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi, Li and Na are placed inside the battery.
Is a method in which at least one of lithium hydroxide and sodium hydroxide is present in the electrolytic solution. In this case, from the viewpoint of the conductivity of the electrolyte, the potassium hydroxide in the electrolyte is 70 wt.
% Or more, and the specific gravity of the electrolyte is desirably 1.20 to 1.40. In order to cause at least one element of Li and Na to act on a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi, an alloy powder such as Li or N
There is a method of treating with an alkaline aqueous solution containing a. At this time, if the treatment temperature with the aqueous alkali solution is lower than 80 ° C., the effect is small. 80 ° C for full effect
It is desirable that this is the case.

[0017]

The present invention will be described in more detail with reference to the following examples. The production of the alloy can be performed by arc melting, an Ar gas atomizing method, a roll quenching method, a rotating electrode method, or the like, using a commercially available raw material. The alloy was subjected to mechanical pulverization after being subjected to hydrogenation pulverization, and classified to a desired particle size. The alloy having a particle size of 40 μm or less was used.

Example 1 In this example, alkali treatment of hydrogen storage alloy particles was studied. Ti _0.3 V _0.53
An alloy having a composition of Cr _0.15 La _0.02 was produced by a gas atomizing method. Ni powder is added to the powder classified into a predetermined particle size of this alloy.
After applying 10 wt% Ni to the surface using an electroless plating solution, heat treatment was performed at 600 ° C. for 3 hours. 100 parts by weight of this alloy powder was treated with 200 parts by weight of an aqueous alkali solution having the composition shown in Table 1 for 1 hour, then washed with water and dried. Water is added to the alloy powder thus obtained to form a paste, which has a porosity of 9%.
The foamed nickel porous material having a thickness of 5% and a thickness of 0.8 mm was filled. This was dried at 120 ° C., pressed with a roller press, and then cut to obtain a hydrogen storage alloy electrode having a width of 3.5 cm, a length of 14.5 cm, and a thickness of 0.50 mm.

A spiral electrode group is formed by combining the hydrogen storage alloy negative electrode with a positive electrode and a separator.
After storing in a / 5 A size battery case and injecting a KOH aqueous solution having a specific gravity of 1.30 as an electrolyte, the opening of the battery case was sealed with a sealing plate and a gasket to produce a sealed battery. The positive electrode was a known foamed nickel electrode having a width of 3.5 cm and a length of 11 cm. A lead plate was connected to the positive electrode, and the lead plate was welded to a positive electrode terminal. As the separator, a polypropylene nonwoven fabric provided with hydrophilicity was used.
This battery has a nominal capacity of 1.6 Ah due to positive electrode capacity regulation. The battery thus prepared was subjected to a 0.2
After charging and discharging at 1C for 15 hours and discharging at 0 and 2C to 1V, charging at 1C for 1 hour at 25 ° C.
The charge / discharge at C to 1 V was repeated. The number of cycles until the capacity falls below 60% of the initial value is shown in Table 1 as life.

[0020]

[Table 1]

As is clear from Table 1, the present invention uses an alloy powder obtained by heat-treating a hydrogen storage alloy having a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi with an alkaline aqueous solution containing Na or Li. According to the battery No. 1-2
Nos. To 1-9 are Nos. Of Comparative Examples. It turns out that it is excellent in cycle life compared with 1-1. As for the temperature of the alkali treatment, the results in Table 1 show that the effect is large at 80 ° C. or higher. In addition, pretreatment with an aqueous alkali solution has an advantage that an electrolyte having a high conductivity can be used.

Example 2 In this example, an electrolytic solution was studied. An alloy having a composition of Ti _0.3 V _0.53 Cr _0.15 La _0.02 was produced by a gas atomizing method. A 10% by weight Ni was applied to the surface of the powder of the alloy classified into a predetermined particle size using a Ni electroless plating solution, and then heat-treated at 600 ° C. for 3 hours. A sealed nickel-metal hydride storage battery of 4/5 A size was produced in the same manner as in Example 1 except that the electrolyte shown in Table 2 was used. The battery thus manufactured was subjected to a charge / discharge test under the same conditions as in Example 1.
The results are shown in Table 2.

[0023]

[Table 2]

When at least one of Li and Na is put in the electrolytic solution, the cycle life is improved as in the first embodiment. This is presumably because Li and Na acted on the Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi on the alloy surface with the progress of charging and discharging and the progress of time. However, LiOH or NaOH in the electrolyte
Since the electric conductivity is lower than that of KOH, the amount of KOH is desirably 70 wt% or more from the viewpoint of high-rate discharge characteristics. Similarly, the specific gravity of the electrolytic solution is preferably 1.20 or more and 1.40 or less. Putting at least one of Li and Na in the electrolytic solution as in this embodiment has advantages such as easy operation in the process. It is also effective to combine with the method of treating with the aqueous solution containing at least one of lithium hydroxide and sodium hydroxide at the stage of the alloy powder used in Example 1.

Example 3 In this example, the alloy composition was studied. Alloys having various compositions shown in Table 3 were produced by arc melting. No. 3-35 and 3-3
Except for the alloy used for 5 ′, 10 wt% of Ni was applied to the surface using a Ni electroless plating solution, and then heat treatment was performed at 600 ° C. for 3 hours. As electrolyte, KOH 80 wt%, Na
Except for using an electrolyte having a specific gravity of 1.31 containing 17 wt% of OH and 3 wt% of LiOH, the sealed nickel-metal hydride storage battery No. of 4/5 A size was manufactured in the same manner as in Example 1.
3-1 to 3-35 were produced. As a comparative example, specific gravity 1.
Comparative battery No. 31 using the KOH aqueous solution of No. 31 3-1'-
3-35 'was similarly produced. The battery thus manufactured was subjected to a charge / discharge test under the same conditions as in Example 1. The results are shown in Tables 3 to 6.

Next, 0.4 g of Cu powder was mixed with 0.1 g of the alloy powder, and the mixture was pressed into a pellet to form a negative electrode. A nickel oxide electrode having an excessive electric capacity is arranged at a counter electrode of the negative electrode, and the capacity is regulated by the hydrogen storage alloy negative electrode under the condition that the electrolytic solution composed of a KOH aqueous solution having a specific gravity of 1.30 is abundant. Charge and discharge were performed. Charging is 100 mA per 1 g of hydrogen storage alloy, and the first cycle is 8 hours,
The second and subsequent cycles were performed for 5.5 hours. The discharge was repeated at a charge current of 50 mA per gram of alloy and the terminal voltage was increased to 0.8 V. The maximum discharge capacity was shown in Tables 3 to 6. In the table, L was used unless otherwise specified. Mm represents misch metal.

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

As shown in Tables 3 to 6, the hydrogen-absorbing alloys of various compositions having a crystal structure of a body-centered cubic structure also have an L diffusion layer containing a phase having a body-centered cubic structure similar to TiNi.
It can be seen that the cycle life is improved by the action of i and Na. However, No. having no phase having a body-centered cubic structure similar to TiNi. For 3-34, the capacity of the battery was not sufficient before performing the charge / discharge cycle.
Since this does not contain Ti in the parent phase, it does not have a phase having a body-centered cubic structure similar to electrochemically active TiNi,
This is because it does not work as a negative electrode. In addition, No. 3-35
From the comparison between No. and 3-35 ', the cycle characteristics of a composition containing Ni inside the alloy are also improved by allowing Li or Na to act. However, in this case, No. 1 using plating and heat treatment was used. The cycle life is shorter than 3-1 to 3-33. This is thought to be due to the difference in the area of the Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi in contact with the electrolyte containing Li or Na. That is, it is considered that the effect of the present invention appears on the entire alloy particle surface by performing plating and heat treatment.

As is apparent from Tables 3 to 6, the formula V
_{1-abcd Ti a Cr b M} c L d (M is Mn, Fe, Co,
Cu, Nb, Zn, Zr, Mo, Ag, Hf, Ta,
At least one element selected from the group consisting of W, Al, Si, C, N, P, and B; L is at least one element selected from the group consisting of rare earth elements and Y;
2 ≦ a ≦ 0.5, 0.1 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.
2, 0 <d ≦ 0.03), alloy particles having a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi on the surface,
When at least one of a is applied, the effect is particularly large.

Example 4 In this example, a method of adhering Ni to the surface of alloy particles was examined. Ti _0.3 V _0.53
An alloy having a composition of Cr _0.15 La _0.02 was produced by a gas atomizing method. Ni was applied to the surface of the powder of the alloy classified into a predetermined particle size by various methods shown in Table 7. Using these alloy powders, a sealed nickel-metal hydride battery having a size of 4/5 A was produced in the same manner as in Example 1. The battery thus manufactured was subjected to a charge / discharge test under the same conditions as in Example 1. Table 7 shows the results. The electrolyte contains N
o. 4-1 to 4-7: KOH 80 wt%, NaOH
Specific gravity 1.3 including 17 wt% and 3 wt% of LiOH
No. 1 electrolyte solution From 4-1 'to 4-7', a KOH electrolyte having a specific gravity of 1.30 was used.

Next, Cu was added to 0.1 g of the alloy powder of this embodiment.
0.4 g of the powder was mixed and pressed into a pellet to prepare a negative electrode. A nickel oxide electrode having an excess electric capacity is arranged at the counter electrode of this negative electrode, and charge and discharge are performed in an open system in which the capacity is regulated by the hydrogen storage alloy negative electrode under the condition that the electrolytic solution composed of a KOH aqueous solution having a specific gravity of 1.30 is abundant. Was done. Charging is 100 mA per 1 g of hydrogen storage alloy, and the first cycle is 8 hours,
The second and subsequent cycles were performed for 5.5 hours. The discharge was repeated at a charge current of 50 mA per gram of alloy and the terminal voltage was increased to 0.8 V. The maximum discharge capacity was shown in Table 4.

[0035]

[Table 7]

As is clear from Table 7, a high discharge capacity cannot be obtained only by adding Ni to the surface, but a high discharge capacity can be obtained by alloying with heat treatment or mechanical force. And the presence of at least one of Li and Na in the electrolyte improved cycle characteristics.

As a method of adding Ni to the surface, when the plating and the powder were mixed, the plating covered the alloy surface more densely, so that good characteristics were obtained. In the heat treatment, the diffusion capacity of Ni hardly progresses at 400 ° C., so that the discharge capacity is low.
At 800 ° C., the diffusion was excessive, and the discharge capacity was reduced because the structure of the Ni diffusion layer had the same crystal structure as Ti ₂ Ni. The best characteristics were obtained at around 600 ° C.
Although a high discharge capacity was obtained by mechanical alloying using a ball mill, the crystallinity of the alloy was reduced, and the discharge capacity was slightly reduced as compared with the heat treatment.

[0038]

As described above, according to the present invention, excellent cycle characteristics are provided to a sealed nickel-metal hydride storage battery having a large discharge capacity using a hydrogen storage alloy having a body-centered cubic structure.

Continuing from the front page (72) Inventor Yoichiro Tsuji 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. ) 5H003 AA02 AA04 BA01 BB02 BC01 BD01 5H016 AA02 BB01 BB11 EE01 HH01 5H028 AA06 EE01 FF04 HH02 HH03 HH08

Claims (9)

[Claims] 1. A negative electrode comprising hydrogen storage alloy particles, wherein said alloy particles are hydrogen storage alloy particles having a body-centered cubic structure, and at least a part of the surface thereof has TiN
A sealed nickel-metal hydride storage battery comprising: a Ni diffusion layer containing a phase having a body-centered cubic structure similar to i; and at least one element of Li and Na in the battery. 2. The sealed nickel-metal hydride storage battery according to claim 1, wherein at least one element of Li and Na is contained in the Ni diffusion layer. 3. The sealed nickel-metal hydride battery according to claim 1, wherein at least one of Li and Na is contained in the electrolyte as lithium hydroxide or sodium hydroxide. 4. A hydrogen-absorbing alloy having the body-centered cubic structure, formula _{V 1-abcd Ti a Cr b} M c L d (M is Mn, F
e, Co, Cu, Nb, Zn, Zr, Mo, Ag, H
f, at least one element selected from the group consisting of Ta, W, Al, Si, C, N, P, and B; L is at least one element selected from the group consisting of rare earth elements and Y; .2 ≦ a ≦ 0.5, 0.1 ≦ b ≦ 0.4, 0 ≦
The sealed nickel-metal hydride storage battery according to claim 1, 2 or 3, which is an alloy represented by c ≦ 0.2, 0 <d ≦ 0.03). 5. The electrolytic solution contains at least one of lithium hydroxide and sodium hydroxide and potassium hydroxide, the concentration of potassium hydroxide is 70% by weight or more, and the specific gravity of the electrolytic solution is 1.20 to 1. The sealed nickel-metal hydride storage battery according to claim 3, wherein the number is 40. 6. The Ni diffusion layer is formed by applying Ni plating or mixing Ni powder to the hydrogen storage alloy particles having the body-centered cubic structure and attaching Ni to the surface of the alloy particles, followed by heat treatment. The method for producing a hydrogen-absorbing alloy electrode for a sealed nickel-metal hydride battery according to claim 1, wherein the method comprises a step. 7. The method for producing a hydrogen storage alloy electrode for a sealed nickel-metal hydride storage battery according to claim 6, wherein the heat treatment is performed in an inert gas or in a vacuum at a temperature of 500 to 700 ° C. 8. Hydrogen storage alloy particles having a body-centered cubic structure and having, on at least a part of the surface thereof, a Ni diffusion layer containing a phase having a body-centered cubic structure similar to TiNi, at least lithium hydroxide and water 3. A step of obtaining hydrogen storage alloy particles containing at least one element of lithium and sodium in a Ni diffusion layer by heat treatment with an aqueous alkali solution containing at least one of sodium oxide.
A method for producing a hydrogen-absorbing alloy electrode for a sealed nickel-metal hydride battery according to the above. 9. The heat treatment temperature of said alkaline aqueous solution is 8
The method for producing a hydrogen-absorbing alloy electrode for a sealed nickel-metal hydride battery according to claim 8, wherein the temperature is 0 ° C or higher.