JPH0815079B2 - Hydrogen storage electrode - Google Patents

Description

TECHNICAL FIELD The present invention relates to a battery using an alkali as an electrolytic solution, particularly to a negative electrode of a secondary battery.

Conventional technology Various batteries are widely used as power sources for portable devices, memory backup, mobile, stationary, etc. Of these, rechargeable batteries that can be used repeatedly are widely used mainly because of their resource saving and cost reduction.

A typical example is a lead storage battery, but recently, an alkaline storage battery that has features such as high rate discharge, long life, high reliability, and high energy density has also been applied to considerable applications.

As is well known, the alkaline storage battery system widely used at present is a nickel-cadmium system. The positive electrode includes silver oxide and an air electrode. Iron, zinc, and hydrogen are used for the negative electrode. As an alkaline storage battery, the nickel-cadmium system is excellent in reliability including high-rate discharge and life, and is resistant to overdischarge and overcharge. However, from the viewpoint of higher energy density and low pollution, the hydrogen electrode has recently been attracting attention, and the battery using the hydrogen gas diffusion electrode is also used for space with high reliability.

A battery using a metal hydrogen compound such as the present invention even with the same hydrogen electrode does not need a gas container used for a hydrogen gas diffusion electrode, and can adopt the same structure as a conventional open type or closed type, so that many Can be used for various purposes.

Problems to be Solved by the Invention Currently, Ti ₂ Ni, LaN are used as negative electrodes for metal hydrogen compounds.
i ₅ , CaNi _5, etc. are taken up. Of these, T
Although i ₂ Ni has relatively excellent initial charge and discharge characteristics, the current situation is that the capacity decreases significantly due to repeated charge and discharge. CaNi ₅ shows almost the same behavior, and Ca has a problem in durability against caustic alkali. LaNi ₅ has a slightly smaller capacity than these, is expensive, and is inferior in terms of temperature characteristics.

The present invention improves the energy density by improving such a conventional hydrogen storage alloy negative electrode so as to increase the discharge capacity per volume in particular as compared with the current cadmium electrode. Further, the present invention provides a hydrogen storage alloy negative electrode excellent in life, high-rate discharge characteristics and the like, which is not inferior to that of a cadmium electrode and further aims at low pollution.

Means for Solving the Problems To achieve this object, the present invention has a general formula of Ti _1-x Zr _x
An alloy represented by Fe _α-yz Ni _y Mz is used as the negative electrode. In this case, M is Mg, Ca, V, Nb, Cr, Mo, Mn, Co, Cu, Z.
At least one selected from n, B, Al, C, Si, and Sn is used.

Further, in this alloy system, its composition is of course important, x = 0.01 to 0.4, α = 0.85 to 1.15, y = 0.1 to 0.6, z = 0.
.About.0.5, .alpha.-yz.gtoreq.0.4 is a range which provides the excellent negative electrode of the present invention.

When Co is used as M, z = 0.05 to 0.3 is the optimum composition.

The base of the alloy of the present invention is a TiFe alloy,
TiFe alloys are superior in terms of durability against alkali and price. Further, as a hydrogen storage alloy, although it has a problem in initial activation, it is an alloy having excellent storage and release characteristics of hydrogen. However, the ability to occlude and release hydrogen electrochemically is extremely inferior, and almost no discharge capacity of the so-called electrode is obtained.

However, Ti-Zr-Fe-
It was clarified and proposed that the characteristics of the negative electrode were significantly improved by using a Ni-based material, and that the discharge capacity at a 5-hour rate also showed 200 mAh / g or more. In the present invention, by further improving this, the durability (life) can be further increased by 10 to 30% as compared with the Ti-Zr-Fe-Ni-based electrode.
The Zr-Fe-Ni-M system is used and this is used.

In other words, by using Ti _1-x Zr _x Fe _yz Ni _z , the discharge capacity and life are dramatically improved compared to the original TiFe alloy, and this is further improved by Ti _1-x Zr _x Fe _α-yz The durability is improved by using Ni _y Mz.

Further, it has been found that, when Co is used as M, in addition to such an effect, it is useful for improving the gas absorption capacity (catalytic action) required in the closed type.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples.

Commercially available Ti, Zr, Fe, Ni having a purity of 99.5% or more and each metal as the fifth component shown in Table 1 were weighed so as to have the respective compositions shown in Table 1, and each was melted by heating in an argon arc melting furnace. Alloys having respective compositions of samples No. 1 to No. 28 were obtained. These are just one example of the effective composition of the present invention. For comparison, sample Nos. 29-32 were added as an example of the original Ti _1-x Zr _x Fe _yz Ni _z .

The discharge capacity of each alloy shown in Table 1 was determined as follows. That is, each alloy is
It was a fine powder of 0 mesh or less. A nickel powder was used as a conductive agent in an amount of 10% by weight, a polyvinyl chloride powder was used as a binder in an amount of 3% by weight, and a carboxymethylcellulose aqueous solution having a concentration of 2.5% by weight was used to form a paste, which had a porosity of 95%, It was filled with foamed nickel having an average pore diameter of 150 μm and a thickness of 2.3 mm, pressurized at 400 kg / cm ² , and heated to 130 ° C. to melt polyvinyl chloride to obtain an electrode.

Each electrode thus obtained was cut into 50 × 60 mm,
A lead plate is attached and Ni net is used as the counter electrode
A cell was constructed using an electrolytic solution in which 20 g / l of lithium hydroxide was dissolved in 1.24 caustic potash. A mercury oxide electrode was used as the reference electrode, and discharge to -0.6 V was made to the reference electrode, and the capacity up to that point was converted to 1 gram of the alloy. In addition, charge is 8 hours rate, discharge is 5 hours rate, and measurement temperature is 25 degreeC.

Table 1 shows this discharge capacity as 100 cycles, 300 cycles, 50 cycles.
It shows 0 cycles and 1000 cycles.

As a result of examination in this way, the samples No. 1 to No. 29 in Table 1
In the general formula Ti _1-x Zr _x Fe _α-yz Ni _y Mz, M, Mg, C
It was found that at least one metal selected from a, V, Nb, Cr, Mo, Mn, Co, Cu, Zn, B, Al, C, Si and Sn is preferable. Furthermore, in a more detailed examination, x is 0.01 to 0.4, α = 0.85 to 1.15, y
= 0.1 to 0.6, z = 0 to 0.5, α-yz ≧ 0.4 is the alloy composition having the preferable characteristics, and it was found that the range is appropriate.

That is, it was found that this range was excellent in both initial capacity and life, and if it deviated from this composition range, 200 mAh / g, which was a tentatively desired standard, could not be obtained.

This was considered to be due to the decrease in hydrogen storage and desorption abilities due to the compositional shift from the effective alloy phase of TiFe as the base.

In comparison with the _{Ti 1-x Zr x Fe yz} Ni z shown in the sample _{No.29~32, Ti 1-x Zr x} Fe of the present invention
_It can be seen that the life characteristics of the _α-yz Ni _y Mz-based alloy are clearly improved.

Further, among them, M is Co and z is 0.05 to 0.
In addition to these effects, the alloy having the composition of 3 was found to be effective in improving the gas absorption capacity (catalytic activity) as a result of the evaluation of a sealed battery, which is another evaluation method. .

With regard to this gas absorption capacity, a particularly remarkable effect is observed when M is Co, and this effect may be closely related to battery life factors such as battery internal pressure and internal resistance of the sealed alkaline secondary battery. all right.

As described above, as a negative electrode for an alkaline battery, Ti _1-x Zr _x Fe
_α-yz Ni _y Mz system in which M is Mg, Ca, V, Nb, Cr, Mo, Mn, Co, C
u, Zn, B, Al, C, Si, composed of at least one metal selected from Sn, x = 0.01 ~ 0.4, α = 0.85 ~ 1.15, y = 0.1 ~ 0.
When an alloy having a range of 6, z = 0 to 0.5 and α-yz ≧ 0.4 is used, a negative electrode having a high capacity and a long life can be obtained.

This electrode is an open type electrode for alkaline batteries.
Although it is effective for any of the sealed types, in the case of the sealed type, an alloy in which M is Co and z = 0.05 to 0.3 is particularly preferable in terms of gas absorption capacity. The negative electrode of the present invention can be used as a counter electrode regardless of the type such as a nickel electrode, a silver oxide electrode and an air electrode.

Claims (2)

[Claims] 1. The general formula is Ti _1-x Zr _x Fe _α-yz Ni _y Mz, where M is Mg, Ca, V, Nb, Cr, Mo, Mn, Co, Cu, Zn, B, Al, C, S
At least one metal selected from i and Sn, x
= 0.01 to 0.4, α = 0.85 to 1.15, y = 0.1 to 0.6, z = 0 to 0.5,
A hydrogen storage electrode using an alloy with α-yz ≧ 0.4. 2. M in the general formula is Co, and z = 0.05 to 0.3.
The hydrogen storage electrode according to claim 1, wherein the alloy is