JPS60243978A - Metal-hydrogen secondary battery - Google Patents

Abstract

PURPOSE:To enable the maximum capacity to be achieved in the early stage after battery assembly by compressing and packing a gas into the internal space of a sealed-type container in which a positive electrode and a negative electrode containing a hydrogen-absorbing or discharging metal or an alloy are installed. CONSTITUTION:A positive electrode 3 containing a metal oxide and a negative electrode 4 containing a hydrogen-absorbing alloy are immersed in liquid potassium hydroxide electrolyte 11 poured in a container 1. They are electrically connected to a positive and a negative terminal 7 and 8, which are attached to an upper lid 2 and penetrate it, through a positive and a negative current collector 5 and 6. Argon gas is compressed and charged into the internal space of the container 1 through a valve 9 and a gas hole 10 which is formed in the upper lid 2. As a result, the surface of the hydrogen-absorbing electrode is pressed by the electrolyte 11 and a great amount of hydrogen is absorbed by the electrode. Therefore, a discharge capacity level almost equal to the maximum discharge capacity can be achieved during the initial stage of the charge-and-discharge cycle.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention is applicable to metal-hydrogen secondary batteries such as NilaGlu hydrogen batteries, which have an electrode comprising a metal or alloy having the ability to absorb and release hydrogen as a negative electrode. In particular, the present invention relates to a metal-hydrogen secondary battery that can obtain maximum capacity early after battery assembly without performing an activation process.

(b) Prior art A negative electrode for an alkaline secondary battery comprising a metal or an alloy capable of storing and releasing hydrogen has an equity of 11s49-
As seen in Publication No. 25135, a paste made by adding a fixing agent to hydrogen storage alloy powder is applied to a support, dried and sintered, and obtained. Various proposals have been made in the past, such as those obtained by fixing hydrogen-absorbing powder and acetylene black to a support using a binder, and since the negative electrode has a high energy density per unit weight, it is difficult to use high-density batteries. It is excellent as a constituent electrode.

However, a metal-hydrogen secondary battery equipped with a negative electrode made of a hydrogen storage electrode containing a hydrogen storage alloy and a positive electrode made of a metal oxide as an active material has a low initial capacity, and it is difficult to obtain a large capacity in the post-assembly stage of the battery. Therefore, there is a problem in that charging and discharging of several cycles are required. In order to solve this problem, hydrogen storage alloy powder is made to absorb hydrogen in advance by storing hydrogen in a sealed container, and then heating the hydrogen storage alloy powder to release the occluded hydrogen. Generally, a method of activating hydrogen storage alloy and manufacturing a negative electrode using the thus obtained hydrogen storage alloy is commonly used, but in this case, not only does the number of operations for activation increase, but the activated hydrogen storage alloy powder is extremely Because it is highly reactive and oxidizes rapidly in the air, it is not a sufficient solution because it is subject to restrictions in the environment in which it can be handled.

(c) Purpose of the Invention In view of the above, the present invention aims to provide a metal-hydrogen secondary battery that can obtain the maximum capacity at an early stage after battery assembly and eliminates the activation process that involves complicated operations. It is something.

,-2) Structure of the Invention The metal-hydrogen secondary battery of the present invention has a negative electrode comprising a metal or an alloy having the ability to absorb and release hydrogen, and a positive electrode in an internal space of a sealed battery case. The gas is filled under pressure, and the gas filled under pressure is nitrogen,
An inert gas such as argon is suitable.

(E) Example A nickel-hydrogen battery is a typical secondary battery that uses a hydrogen storage alloy for the negative electrode and a metal oxide for the positive electrode. An embodiment of the present invention will be described using a battery that refuses.

A slurry made by mixing carbonyl nickel powder with a thickener and water is applied to both sides of a thin current collector made of nickel-plated iron, dried, and then sintered in a reducing atmosphere to create porous A porous sintered nickel substrate with a density of 80 to 85% was prepared, and the pores were impregnated with a nickel nitrate solution using this as an active material holder, and a series of active material filling operations including alkali treatment, water washing, and drying were repeated. A nickel electrode plate filled with a predetermined amount of nickel hydroxide is obtained, and the nickel electrode plate thus obtained is cut to form a positive electrode. The dimensions of this positive electrode are 60 mm x 30 tm x 0, 6 m.

Next, LaNi 5 having a hydrogen storage capacity is mechanically crushed into a fine powder, and the thus obtained 1IaNi 5
We use polytetrafluoroethylene (PTFE) powder, which easily fiberizes and plastically deforms when subjected to a small shearing force.
LaNi 5 is added in an amount of 1 to 5% based on the weight of the powder, mixed uniformly with a mixer, and at the same time, polytetrafluoroethylene is made into fibers, which are placed on both sides of a current collector made of nickel sound pressure, and the amount of 1 ton/ A hydrogen storage electrode with a diameter of 60 m and a thickness of 1 tone was obtained by pressure molding at a pressure of -, and the hydrogen storage electrode thus obtained was used as a negative electrode.

Figure 1 is a sectional view of the nickel-hydrogen secondary battery (A) of the present invention manufactured using the above-mentioned positive and negative electrodes, showing the opening of the battery case body (1) made of polypropylene resin and the opening of the battery case body (1) made of polypropylene resin. The battery case is sealed by ultrasonic welding with the top cover (2), and the battery case body 11)
60% potassium hydroxide injected into the electrolyte (ID
The positive electrode (3) and negative electrode 14 immersed in 100cc
) are inserted into the upper lid (2) and housed in the positive and negative terminals (7) and (8) respectively; 5), (
6) and is electrically connected via the valve (9).
The internal space of the battery case was filled with argon gas under pressure through the gas inlet I]0) provided in the upper lid (2), and a comparative battery that had not been filled was charged with a current of 25 mA for 16 hours. After fully charging, set the final voltage to 1
, 0■, charging and discharging were repeated under cycle conditions of discharging a current of 50 mA. FIG. 2 is a discharge capacity diagram showing this result, and represents the relationship between the number of charge/discharge cycles and the discharge capacity. As is clear from FIG. 2, it can be seen that the battery of the present invention has an extremely short number of charge/discharge cycles to reach the maximum capacity and is very excellent.

The reaction that occurs at the negative electrode during charging in this charge/discharge cycle is as follows: H++e-→1ad (hydrogen actively adsorbed on the electrode surface) 1a. d −'p Hlattice (Hydrogen occluded inside the electrode) The hydrogen actively adsorbed on the electrode surface is occluded inside the electrode. Then, the hydrogen absorbed inside the electrode gradually increases, and when the saturation amount is occluded, a reaction occurs as shown in H + e - + lad 1 (a d -1-) 1 a d - + H2 ↑, and hydrogen gas is generated. . The saturated hydrogen storage amount of this hydrogen storage electrode varies depending on the type of hydrogen storage metal or alloy, but in general, no matter which hydrogen storage electrode is used, the hydrogen storage electrode's capacity increases as the surrounding pressure increases. The saturated hydrogen storage amount increases, and when a certain pressure is reached, no increase in the hydrogen saturated storage amount is observed even if the pressure is increased further.

Since the battery of the present invention is filled with argon gas under pressure, the gas in the internal space of the container located above the electrolyte pressurizes the surface of the electrolyte, and as a result, the surface of the hydrogen storage electrode, which is the negative electrode, is heated by the electrolyte. The reaction of 1(ad-+H1attice progresses more dominantly, and the reaction of 1(ad+H'aa-+H2↑) is delayed and an extremely large amount of hydrogen is occluded in the electrode. Therefore, it is considered that a value close to the maximum discharge capacity was obtained at the beginning of the charge/discharge cycle.

The gas that is pressurized and filled into the internal space of the battery case may be any gas that does not have an adverse effect on the battery, and may preferably be an inert gas such as nitrogen, argon, or helicum.

(F) Effects of the Invention In the metal-hydrogen secondary battery of the present invention, gas is generated in the internal space of a sealed battery case that houses a negative electrode comprising a metal or alloy capable of absorbing and releasing hydrogen, and a positive electrode. Since the battery is filled under pressure, maximum capacity can be obtained at an early stage after battery assembly, and activation processing that involves complicated operations can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a nickel-metal hydride battery according to an embodiment of the present invention, and FIG. 2 is a discharge capacity diagram of a battery according to the present invention and a comparative battery (6). (1)...Battery case body, (2)...Top lid, (3)...
・Positive electrode, f4)... Negative electrode, (5)... Positive electrode current collector,
(6)... Negative electrode current collector, (7)... Positive electrode terminal, (8
)...Negative terminal, (9)...Valve, tl[l...
・Gas inlet, (111... Electrolyte. Applicant: Shizuo Sano, Patent Attorney, Sanyo Electric Co., Ltd.

Claims (2)

[Claims] (1) A metal-hydrogen secondary battery in which gas is pressurized and filled into the internal space of a sealed battery case that houses a negative electrode and a positive electrode, which are made of a metal or alloy that has the ability to store and release hydrogen. (2) Claim No. 2, wherein the gas is an inert gas (
1) The metal-hydrogen secondary battery described in item 1).