JPH04292860A - Metallic oxide, hydrogen battery - Google Patents

Abstract

PURPOSE:To obtain a battery with stable characteristics by constructing negative pole with rare earth hydrogen absorptive alloy powder with specific grain diameter. CONSTITUTION:In a battery equipped with a positive pole alkaline electrolyte, and a negative pole, having rare earth hydrogen absorptive alloy as a main ingredient, the negative pole is composed of rare earth hydrogen absorptivealloy powder, with average powder diameter of 35+ or -10mum including 13volume% or less, grains with diameter 10mum or less, and 1weight% or less powders which do not pass through a 200-mesh screen by a lazer diffraction method. By using hydrogen absorptive alloy powders of those sizes a battery with good conditions for a long period of time, can be obtained without uneven thickness of applied electrode, and too high fluidity of paste.

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

[Prior Art] Currently, in metal oxide/hydrogen batteries,
Types in which the hydrogen negative electrode is made of a hydrogen storage alloy are attracting attention. The reason for this is that this battery system inherently has a high energy density, is advantageous in terms of volumetric efficiency, is capable of safe operation, and is excellent in terms of characteristics and reliability. .

[0003] LaNi5 has been widely used as a hydrogen storage alloy for the hydrogen negative electrode of this type of battery. Furthermore, an alloy of misch metal (hereinafter referred to as Mm), which is a mixture of lanthanum-based elements such as La, Ce, Pr, Nd, and Sm, and Ni, that is, MmNi5, is also widely used. La as a rare earth component such as LaNi5
Hydrogen storage alloys containing only elements are certainly excellent as battery negative electrode materials, but they are not practical because La is expensive. Therefore, rare earth components such as Mm and M
Mixtures of rare earth elements such as those obtained by subjecting m to simple processing are used.

[0004] Regarding LaNi5 and MmNi5, a part of Ni is Al, Mn, Fe, Co, Ti, Cu.
, Zn, Zr, Cr, B, and other multi-element systems are also used. When producing the electrode, the above-mentioned hydrogen storage alloy is used as a negative electrode material in the form of a powder obtained by mechanically pulverizing or hydrogenally pulverizing.

[0005]

[Problem to be solved by the invention] The hydrogen storage alloy negative electrode is
The above-described pulverized hydrogen storage alloy powder is kneaded with a polymer binder and a conductive material to form a paste, and then a conductive core as a current collector is immersed in a coating tank containing this paste and then pulled up vertically. It is manufactured by removing excess paste through a slit, pressing the whole after drying, and performing a pressure molding process.

However, when produced by the above method,
Even if the paste composition and kneading conditions are constant, there is a problem in that the state of application of the paste varies depending on the alloy lot. In other words, 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. Differences in paste application state are caused by differences in paste fluidity. Therefore, the variation in the coating state is considered to be due to the fact that the fluidity of the paste differs depending on the alloy lot.

The present invention was made in order to solve the conventional problems, and aims to provide a metal oxide/hydrogen battery with stable performance, which includes a stable rare earth-based hydrogen storage alloy electrode in the form of a coating. It is.

[0008]

[Means for Solving the Problems] The present inventors have found that when manufacturing 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. The present invention was achieved by paying attention to this. That is, the present invention provides a metal oxide/hydrogen battery comprising a positive electrode, an alkaline electrolyte, and a negative electrode mainly made of a rare earth hydrogen storage alloy, in which the negative electrode has an average particle size of 35 ± 10 μm as measured by laser diffraction method, A metal oxide, characterized in that it is composed of rare earth hydrogen storage alloy powder, in which particles with a particle size of 10 μm or less account for 13% by volume or less, and particles that do not pass through a 200 mesh sieve account for 1% by weight or less.
Regarding hydrogen batteries.

The rare earth hydrogen storage alloy has the general formula LmAx
(In the formula, Lm is at least one rare earth element including La, and A is Ni, Co, Mn, Al, B, Cu, Zr
and V, and x is from 4.8 to 5.2) is preferred from the viewpoint of hydrogen storage ability.

[0010] The powder of the rare earth hydrogen storage alloy is desirably produced by an impact type pulverizer in view of obtaining stable particle size and cost. For example, a hammer mill method can be used.

[0011] The average particle size of the hydrogen-absorbing alloy powder determined by laser diffraction was 35 ± 10 μm, and the reason why the particles with a particle size of 10 μm or less were 13% by volume or less was because the paste was manufactured using an alloy powder with an average particle size larger 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. This is because if the average particle size is less than 25 μm or if the amount of particles with a particle size of 10 μm or less is greater than 13% by volume, the fluidity is too high and the paste applied to the conductive core will flow down. In the above case, the coating state of the electrode becomes unstable, resulting in a decrease in battery capacity and cycle life.

[0012] The reason why the amount of particles that are not swirled in a 200 mesh sieve is set to 1% by weight or less is because the presence of a small amount of particles larger than 200 mesh increases the fluidity of the paste, causing the same problem as above. It is. A more preferable ratio is 0.5% or less.

[0013] Examples of the polymer binder blended into the paste include sodium polyacrylate, polytetrafluoroethylene (PTFE), and carboxymethyl cellulose (CMC). The blending ratio of the polymer binder is preferably in the range of 0.5 to 5 parts by weight per 100 parts by weight of the hydrogen storage alloy powder.

[0014] Examples of the conductive powder mixed in the paste include carbon black and graphite. The blending ratio of the conductive powder is preferably 0.1 to 4.0 parts by weight based on 100 parts by weight of the nium-ion storage alloy powder.

[0015] Examples of the conductive core which is 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 is made of a paste containing a polymer binder in addition to nickel hydroxide, for example, on a sintered fiber substrate, a foamed metal, a nonwoven plated substrate, or It is created by filling a punched metal substrate or the like. Examples of this polymer binder include those similar to the polymer binder in the hydrogen storage alloy negative electrode.

[0017] According to the present invention, a metal oxide/hydrogen battery having a uniform coating of a hydrogen storage alloy electrode and stable performance can be provided.

[0018]

[Examples] Examples of the metal oxide/hydrogen battery of the present invention will be described in detail below. Composition is LmNi4.2Co0.2
After mechanically pulverizing an alloy represented by Mn0.3Al0.3, the particle size was measured by laser diffraction method and sieve residue, and various particle sizes shown in Table 1 were prepared. Among these, No. 1~
No. 6 was mechanically pulverized and large particles were removed using a 200 mesh sieve. Also No. 1, 4, 6, and 7 are comparative examples. In the above compositional formula, Lm is a rare earth element and consists of the following weight percent. La: 45.1%, Ce: 4.6%,
Pr: 12.1%, Nd: 37.0%, other rare earth elements: 1.2%.

A paste was prepared by adding PTFE, sodium polyacrylate or CMC as a binder, and carbon black and water as a copper electrolyte to each of the hydrogen storage alloy powders. Next, the punched metal as a current collector is transported into a coating tank containing this paste, and after being lifted vertically from the coating tank, excess paste is removed through a slit and applied to the surface of the punched metal. did. Subsequently, after drying, 100 hydrogen storage alloy negative electrodes were each produced by cutting them using a roller press.

[0020] The weight and thickness of each of the above-mentioned hydrogen storage alloy negative electrodes were examined as the paste was applied in the manufacture of the negative electrode. The respective control values are 10.0±0.5g, 0.4
0±0.02 mm, and the number of sheets outside this range is considered to be defective and is also listed in Table 1. Regarding the thickness, each electrode was measured at three locations, and if even one location was out of range, it was counted as defective. In Table 1, A indicates the material passed through a 200 mesh sieve after mechanical pulverization, and B indicates only mechanical pulverization.

[0021]

[Table 1]

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

[0023] The hydrogen storage alloy electrode and the non-sintered nickel oxide electrode were wound through a 0.20 mm thick polyamide nonwoven fabric to prepare an electrode group. This electrode group
Insert the pressure detector 5 into the AA size space of the acrylic resin container, and fill this space with KOH7 standard and LiOHl.
A specified electrolytic solution was poured into the cell, the cell was sealed, and a test cell as shown in FIG. 1 was assembled. That is, this test cell includes a battery case consisting of 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 an AA size battery is formed in the center of the case body 1. An electrode group 4 is housed inside this space 3, and an electrolyte is accommodated.

The cap 2 is airtightly fixed onto 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 the hydrogen storage alloy negative electrode and a positive electrode lead 11 from the non-sintered nickel positive electrode are led out through between the rubber sheet 6 and the O-ring 7.

A charge/discharge cycle test was conducted on each of these test cells. The results are shown in Table 2. Note that Table 2 shows the number of cycles when the battery internal pressure reached 20 kg/cm2 by repeating 1C discharge and 1C charge.

[0026]

[Table 2]

The cycle life is not only affected by the amount of alloy, but also changes due to abnormalities in 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 and the surface area of the alloy powder when hydrogenated and crushed are correlated, so the alloy of this example has a surface area of 0.05 when the alloy powder is hydrogenated and crushed. ~0.20
m2/g is used.

[0028]

Effect of the invention: As is clear from Tables 1 and 2, the average particle size by laser diffraction is 35±10 μm, and the particle size is 10 μm.
The negative electrode, which uses a mechanically crushed hydrogen storage alloy containing 13% by volume or less of the following particles and 1% by weight or less of particles that do not pass through a 200 mesh sieve, is a metal oxide with uniform coating and stable performance.・Can provide hydrogen batteries.

[Brief explanation of drawings]

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

[Explanation of symbols]

1 case body 2 caps 3 spaces 4 electrode group 5 pressure detector 10 negative lead

Claims (3)

[Claims] Claim 1: A metal oxide/hydrogen battery comprising a positive electrode, an alkaline electrolyte, and a negative electrode mainly made of a rare earth hydrogen storage alloy, wherein the negative electrode has an average particle size of 35 ± 10 μm as measured by laser diffraction, Particles with a particle size of 10 μm or less are 1
1. A metal oxide/hydrogen battery comprising a rare earth hydrogen storage alloy powder having a particle size of 3% by volume or less, and 1% by weight or less of particles that do not pass through a 200 mesh sieve. [Claim 2] The rare earth hydrogen storage alloy has the general formula L
mAx (where Lm is at least one rare earth element including La, and A is Ni, Co, Mn, Al, B, Cu
, Zr, and V, and x is 4.8 to 5.2. Hydrogen battery. 3. The metal oxide according to claim 1, wherein the rare earth hydrogen storage alloy powder is obtained by crushing a hydrogen storage alloy ingot using an impact type crusher.
Hydrogen battery.