JP3044495B2 - Metal oxide / hydrogen battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal oxide / hydrogen battery using a metal oxide as a positive electrode active material and hydrogen as a negative electrode active material.

[0002]

2. Description of the Related Art At present, in metal oxide / hydrogen batteries,
Attention has been paid to a type in which the hydrogen negative electrode is made of a hydrogen storage alloy. The reason is that this battery system originally has a high energy density, is advantageous in terms of volumetric efficiency, can operate safely, and is excellent in characteristics and reliability. .

As a hydrogen storage alloy used for a hydrogen negative electrode of this type of battery, LaNi ₅ has been frequently used. In addition, an alloy of Ni with a misch metal (hereinafter referred to as Mm), which is a mixture of lanthanum-based elements such as La, Ce, Pr, Nd, and Sm, that is, MmNi ₅ is also widely used. La as a rare earth component such as LaNi ₅
A hydrogen storage alloy containing only an element is certainly excellent as a battery negative electrode material, but is not practical because La is expensive. For this reason, rare earth components include Mm and M
A mixture of rare earth elements which can be obtained by subjecting m to a simple treatment is used.

As for LaNi ₅ and MmNi ₅ , a part of Ni is replaced with Al, Mn, Fe, Co, Ti, C
Multi-element materials substituted with elements such as u, Zn, Zr, Cr and B are also used. The above-mentioned hydrogen storage alloy is used as a negative electrode material in the form of a powder obtained by mechanical pulverization or hydrogenation pulverization when producing an electrode.

[0005]

SUMMARY OF THE INVENTION A hydrogen storage alloy negative electrode comprises:
The crushed hydrogen storage alloy powder is kneaded with a polymer binder or a conductive material to form a paste, and then a conductive core as a current collector is dipped into a coating tank containing the paste, and then vertically pulled up. It is manufactured by removing excess paste through a slit, pressing the whole after drying, and pressing.

However, when manufactured by the above-described method,
Even when the paste composition and the kneading conditions are constant, there is a problem that the paste application state varies depending on the alloy lot. That is, it is difficult to obtain a hydrogen storage alloy electrode in which the amount of alloy contained per electrode is stable,
This leads to variations in battery performance such as cycle life. The difference in the paste application state is caused by the difference in the fluidity of the paste. Therefore, it is considered that the dispersion of the application state is caused by the fact that the fluidity of the paste differs depending on the alloy lot.

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and it is an object of the present invention to provide a metal oxide / hydrogen battery having a stable performance including a rare earth-based hydrogen storage alloy electrode with a stable coating. It is.

[0008]

Means for Solving the Problems The present inventors have found that when producing a negative electrode made of a rare earth hydrogen storage alloy, the state of paste application is related to the average particle size and particle size distribution of the hydrogen storage alloy powder. Focusing on this, the present invention has been reached. That is, the present invention relates to a metal oxide-hydrogen battery including a positive electrode, an alkaline electrolyte, and a negative electrode mainly composed of a rare earth hydrogen storage alloy, wherein the negative electrode has an average particle size of 35 ± 10 μm by a laser diffraction method. A metal oxide comprising a rare earth hydrogen storage alloy powder in which particles having a particle size of 10 μm or less are 13% by volume or less and particles which do not pass through a 200 mesh screen are 1% by weight or less.
It relates to a hydrogen battery.

The rare earth hydrogen storage alloy has a general formula of LmAx
(Where Lm is at least one rare earth element containing La, and A is Ni, Co, Mn, Al, B, Cu, Zr
And at least one element selected from the group consisting of V and V, wherein x is 4.8 to 5.2).

The rare earth-based hydrogen storage alloy powder is desirably produced by an impact-type pulverizer from the viewpoint of obtaining a stable particle size and cost. For example, a hammer mill method can be used.

The reason why the average particle size of the hydrogen storage alloy powder by laser diffraction is 35 ± 10 μm and the particles having a particle size of 10 μm or less are 13% by volume or less is that the paste was produced from an alloy powder having an average particle size of more than 45 μm. In this case, the fluidity is low, and the thickness of the electrode tends to be uneven when applied to the conductive core. If the average particle size is less than 25 μm or the particles having a particle size of 10 μm or less are larger than 13% by volume, the fluidity is too high and the paste applied to the conductive core runs off. In the above case, the application state of the electrode becomes unstable, and the battery capacity and the cycle life are reduced.

The reason that the amount of particles that do not vortex the 200 mesh screen is set to 1% by weight or less is that the presence of a trace amount of particles of 200 mesh or more increases the fluidity of the paste and causes the same problem as described above. It is. A more desirable ratio is 0.5% or less.

Examples of the polymer binder to be mixed in the paste include sodium polyacrylate, polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC) and the like. It is desirable that the compounding ratio of the polymer binder is in the range of 0.5 to 5 parts by weight based on 100 parts by weight of the hydrogen storage alloy powder.

Examples of the conductive powder to be mixed in the paste include carbon black, graphite and the like. It is desirable that the compounding ratio of the conductive powder is 0.1 to 4.0 parts by weight based on 100 parts by weight of the pearl occlusion alloy powder.

Examples of the conductive core as the current collector include those having a two-dimensional structure such as punched metal, expanded metal, and wire mesh.

The non-sintered nickel oxide electrode used as the positive electrode may be made of a paste having a composition containing a polymer binder in addition to nickel hydroxide, for example, a sintered fiber substrate, a foamed metal, a nonwoven-plated substrate, It is created by a method of filling a punched metal substrate or the like. Examples of the polymer binder include those similar to the polymer binder in the hydrogen storage alloy negative electrode.

According to the present invention, it is possible to provide a metal oxide / hydrogen battery having a uniform performance and a stable performance of the hydrogen storage alloy electrode.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the metal oxide / hydrogen battery of the present invention will be described in detail. The composition is LmNi _4.2 Co _0.2
After mechanically pulverizing the alloy represented by Mn _0.3 Al _0.3 , the particle size was measured by a laser diffraction method and a sieve residue, and various particle sizes shown in Table 1 were prepared. No. 1 to
In No. 6, particles having a large particle size were removed with a 200 mesh sieve after mechanical pulverization. No. 1, 4, 6, and 7 are comparative examples. In the above composition formula, Lm is a rare earth element and is composed of the following weight%. La: 45.1%, Ce: 4.6%,
Pr: 12.1%, Nd: 37.0%, other rare earth elements: 1.2%.

A paste was mixed and prepared by adding PTFE, sodium polyacrylate and CMC as a binder and carbon black and water as a copper electric agent to each of the hydrogen storage alloy powders. Next, the punched metal as a current collector is transported into a coating tank containing the paste, and is vertically pulled up from the coating tank. Then, excess paste is removed through a slit to be applied to the surface of the punched metal. did. Subsequently, after drying, the resultant was cut with a roller press to prepare 100 pieces of hydrogen storage alloy negative electrodes.

The weight and thickness of the electrode were examined as the paste of the paste in the production of each of the above-mentioned hydrogen storage alloy negative electrodes. Each control value is 10.0 ± 0.5g, 0.4
0 ± 0.02 mm, and the numbers out of this range are also shown in Table 1 as defectives. Regarding the thickness, three places were measured for one electrode, and those out of the range even at one place were counted as defective. A in Table 1
Is 200 mesh sieve after mechanical pulverization, B
Is only mechanical grinding.

[0021]

[Table 1]

A paste containing nickel hydroxide and cobalt oxide was prepared. This paste was filled into a sintered nickel fiber substrate, dried, pressed, and cut to produce a non-sintered nickel positive electrode.

The hydrogen storage alloy electrode and the non-sintered nickel oxide electrode were wound through a 0.20 mm thick nonwoven fabric made of polyamide to form an electrode group. This electrode group is
It is inserted into the space of AA size of the acrylic resin container with the pressure detector 5 attached, and this space is filled with KOH7 standard, LiOHl
A specified electrolyte was injected and sealed, and a test cell as shown in FIG. 1 was assembled. That is, the test cell includes a battery case including the case body 1 and the cap 2 made of the acrylic resin. A space 3 having the same inner diameter and height as the metal container of the AA-size battery is formed in the center of the case body 1, and an electrode group 4 is housed in the space 3, and the electrolyte 3 Is housed.

The cap 2 is air-tightly fixed on the case body 1 with bolts 8 and nuts 9 via a rubber sheet 6 and an O-ring 7. A negative electrode lead 10 from a hydrogen storage alloy negative electrode and a positive electrode lead 11 from a non-sintered nickel positive electrode are led out between the rubber sheet 6 and the O-ring 7.

Each of these test cells was subjected to a charge / discharge cycle test. Table 2 shows the results. Table 2 shows the number of cycles when the internal pressure of the battery reached 20 kg / cm ² by repeating 1C discharge and 1C charge.

[0026]

[Table 2]

The cycle life is not affected only by the amount of alloy, but changes even due to abnormality of the alloy such as segregation of alloy components even if the amount of alloy is the same. Therefore, in order to keep the conditions constant, the cycle life is correlated with the surface area of the alloy powder at the time of hydrogrinding. ~ 0.20
m ² / g is used.

[0028]

As is clear from Tables 1 and 2, the average particle diameter by laser diffraction is 35 ± 10 μm, and the particle diameter is 10 μm.
A negative electrode using a mechanically ground hydrogen storage alloy in which the following particles are 13% by volume or less and 1% by weight or less of particles that do not pass through a 200 mesh sieve is a metal oxide having a uniform coating state and stable performance.・ A hydrogen battery can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a test cell used in an embodiment of the present invention.

[Explanation of symbols]

 1 case body 2 cap 3 space 4 electrode group 5 pressure detector 10 negative electrode lead

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kazuta Takeno 3-4-1-10 Minamishinagawa, Shinagawa-ku, Tokyo Examiner at Toshiba Battery Co., Ltd. Michiko Sakai (56) References JP-A-2-65058 (JP) JP-A-2-306541 (JP, A) JP-A-63-141258 (JP, A) JP-A-63-264867 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H01M 4/24-4/26 H01M 4/38

Claims (3)

(57) [Claims] 1. A metal oxide / hydrogen battery comprising a positive electrode, an alkaline electrolyte, and a negative electrode mainly composed of a rare earth hydrogen storage alloy, wherein the negative electrode has an average particle size of 35 ± 10 μm as determined by laser diffraction. 13 particles having a particle size of 10 μm or less
A metal oxide / hydrogen battery comprising a rare earth hydrogen storage alloy powder having a volume percentage of not more than 1% by weight and a particle not passing through a 200 mesh sieve. 2. The method according to claim 1, wherein the rare-earth hydrogen storage alloy has a general formula Lm
Ax (where Lm is at least one rare earth element including La, and A is Ni, Co, Mn, Al, B, Cu,
2. The metal oxide according to claim 1, wherein the metal oxide has at least one element selected from the group consisting of Zr and V, and x is 4.8 to 5.2.
Hydrogen battery. 3. The metal oxide / hydrogen battery according to claim 1, wherein said rare earth hydrogen storage alloy powder is obtained by pulverizing a hydrogen storage alloy ingot with an impact type pulverizer.