JP3146063B2 - Metal oxide / hydrogen secondary batteries - 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 secondary 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, attention has been paid to a metal oxide / hydrogen secondary battery in which a hydrogen electrode is formed 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, is capable of safe operation, and is excellent in characteristics and reliability. is there.

As the hydrogen storage alloy used for the hydrogen negative electrode of the secondary battery, LaNi ₅ has been frequently used. Also, 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 widely used. Since MmNi ₅ uses Mm as a rare earth component, it is inexpensive and practical compared to LaNi ₅ using only an expensive La element as a rare earth component.

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, and B are also used.

However, the metal oxide / hydrogen secondary battery provided with the negative electrode containing the hydrogen storage alloy powder has a problem that the charge / discharge cycle life varies. The direct cause of determining the charge / discharge cycle life is that the hydrogen storage alloy powder constituting the negative electrode is pulverized as the charge / discharge cycle progresses, and the negative electrode is deteriorated. Therefore, the difference in charge / discharge cycle characteristics is
This is due to the difference in progress of pulverization depending on the properties of the hydrogen storage alloy. The difference in pulverization is considered to be due to impurities in the hydrogen storage alloy, variations in alloy homogeneity due to variations in alloy manufacturing conditions, and the like, but is not clear at this stage.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the conventional problems, and includes a rare earth-based hydrogen storage alloy having a specific surface area determined by a BET method at the time of hydrogrinding. It is an object of the present invention to provide a metal oxide / hydrogen secondary battery having a cycle life of:

[0007]

The present invention relates to a metal oxide / hydrogen secondary battery comprising a positive electrode, an alkaline electrolyte and a negative electrode mainly composed of a rare earth-based hydrogen storage alloy. to 30 ° C., 5 to 10 atm specific surface area by the BET method and triturated once hydrogenated under hydrogen pressure of (gauge pressure) is 0.02 m ² / g or more, the hydrogen of the rare earth system to be less than 0.05 m ² / g A metal oxide / hydrogen secondary battery using an occlusion alloy.

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

[0009] The ratio by the BET method at the time of the above-mentioned hydro pulverization
The use of a hydrogen storage alloy whose surface area is in the above range is as follows:
This is for the following reasons. The specific surface area is 0.
050m^Two / G of hydrogen storage alloy,
Charge / discharge cycle of secondary battery with negative electrode containing hydrogen storage alloy
The service life of the vehicle can be further improved. Meanwhile, the ratio table
Area is 0.020m^Two / G of hydrogen storage alloy
It is difficult to manufacture due to manufacturing technology.

The hydrogen storage alloy negative electrode is manufactured by the following method. First, a hydrogen storage alloy whose specific surface area by the BET method at the time of the hydrogrinding becomes a specific range is mechanically pulverized or hydrogenated and pulverized to a powdery state. Then,
A paste is prepared by blending a polymer binder and, if necessary, a conductive powder with the hydrogen storage alloy powder. Subsequently, the paste is coated on a conductive core as a current collector and fixed to produce a hydrogen storage alloy negative electrode.

[0011] Examples of the polymer binder incorporated 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.

As the conductive powder to be mixed in the paste, for example, carbon black, graphite and the like can be mentioned. It is desirable that the mixing ratio of the conductive powder is in the range of 0.1 to 4 parts by weight based on 100 parts by weight of the hydrogen storage alloy powder.

The conductive core, which is a current collector to which the paste is applied, may be, for example, a two-dimensional structure such as punched metal, expanded metal, or wire mesh, or a three-dimensional structure such as foamed metal or reticulated sintered metal fiber. Structures and the like can be given.

As the positive electrode, for example, a non-sintered nickel oxide electrode is used. The non-sintered nickel oxide electrode includes a paste having a composition containing a polymer binder in addition to nickel hydroxide, such as a sintered fiber substrate, a foamed metal, a non-woven plated substrate, or a punched metal substrate. It is manufactured by the method of filling into. Examples of the polymer binder include those similar to the polymer binder in the hydrogen storage alloy negative electrode.

The aqueous alkaline solution used as the alkaline electrolyte may be, for example, a 25 to 31% by weight aqueous potassium hydroxide solution to which an aqueous 15 to 50 g / l lithium hydroxide solution is added.

[0016]

According to the present invention, when the hydrogen storage alloy used for the negative electrode is hydrogenated and pulverized once under hydrogen pressure of 2 to 30 ° C. and 5 to 10 atm (gauge pressure), the specific surface area by the BET method is 0.020 m 2. ^Two / G or more 0.050 m ² / G is selected from the group consisting of rare-earth hydrogen-absorbing alloys and mechanically or hydrogenated and used as the negative electrode active material, so that the metal oxide / hydrogen has a long cycle life and a small variation in the life. A secondary battery can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the metal oxide / hydrogen secondary battery of the present invention will be described in detail. Example 1 and Comparative Examples 1 to 3

The composition is LmNi _4.0 Co _0.4 Mn _0.3 Al
Of the rare earth hydrogen storage alloys represented by _0.3 , 10
When hydrogenated and pulverized once under a hydrogen pressure of 10 ° C. and 10 atm (gauge pressure), a material whose specific surface area by the BET method had the following value was prepared. As an example, 0.040 m ² /
g, 0.045m ² / G, and 0.07 as a comparative example
0m ² / G, 0.100 m ² / G. In the composition,
Lm is a rare earth element and consists of the following weight percentages: La:
45.1%, Ce: 4.6%, Pr: 12.1%, N
d: 37.0%, other rare earth elements: 1.2%.

A hydrogen storage alloy having the above composition and specific surface area is mechanically pulverized, and polytetrafluoroethylene, sodium polyacrylate, carboxymethyl cellulose as a polymer binder, and carbon black and water as a conductive agent are added to the alloy powder. And mixed to prepare four types of pastes. Subsequently, the pastes were applied to a punched metal as a current collector, dried, pressed, and cut to obtain four types of hydrogen storage alloy negative electrodes.

Also, a paste containing nickel hydroxide and cobalt oxide was prepared. This paste is filled into a nickel sintered fiber substrate, and after further drying, pressed all over,
By cutting, a non-sintered nickel positive electrode was produced.

The above-mentioned hydrogen storage alloy negative electrode and non-sintered nickel positive electrode were wound through a 0.20 mm thick nonwoven fabric made of polyamide to prepare an electrode group. This electrode group is inserted into an AA-sized space of an acrylic resin container provided with a pressure detector, and 7N KOH and 1N Li are inserted into this space.
An electrolytic solution containing OH 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 in the center of the case body 1
A space 3 having the same inner diameter and height as the metal container of the A-size battery is formed. Inside the space 3, an electrode group 4 is accommodated, and further an electrolyte is accommodated. The cap 2 is air-tightly fixed on the case body 1 by bolts 7 and nuts 8 via a rubber sheet 5 and an O-ring 6. The cap 2 has a pressure detector 9
Is attached. A negative electrode lead 10 from the 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 5 and the O-ring 6.

Each of the test cells was subjected to a charge / discharge cycle test. The results are shown in Table 1 below.
Table 1 shows that 1C discharging and 1C charging were repeated,
Battery internal pressure is 20kg / cm ² Shows the number of cycles when

[0023]

As is clear from Table 1, the specific surface area by the BET method at the time of the hydropulverization is 0.020 m.
^Two / G or more 0.050 m ² It can be seen that a metal oxide / hydrogen secondary battery having a long cycle life can be obtained by selecting a hydrogen storage alloy having a capacity of less than / g and using a negative electrode containing a powder obtained by pulverizing the hydrogen storage alloy.

[0025]

As described above in detail, according to the present invention, a high performance metal oxide / hydrogen secondary battery having a long cycle life and little variation in the life can be provided.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Case main body, 2 ... Cap, 4 ... Electrode group.

Continued on the front page. (72) Inventor Kaoru Hosobuchi 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo East Shiba Battery Co., Ltd. (72) Inventor Ichiro Saruwatari 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo East (56) References JP-A-4-112458 (JP, A) JP-A-5-36406 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4 / 38 H01M 4/24

Claims (1)

(57) [Claims] And 1. A container, a positive electrode accommodated in the container, an alkaline electrolyte housed in the container, the contents
A metal oxide-hydrogen secondary battery comprising a negative electrode housed in a vessel and containing a rare earth-based hydrogen storage alloy powder as an active material, wherein the negative electrode is at 2 to 30 ° C. and 5 to 10 atm (gauge pressure). the specific surface area by the BET method when crushed once hydrogenated under hydrogen pressure of) the 0.02 m ² / g or more, a metal which comprises a hydrogen storage alloy of a rare earth system less than 0.05 m ² / g Oxide / hydrogen secondary batteries.