JPH06251800A - Manufacture of sealed nickel-hydrogen secondary battery - Google Patents

Abstract

PURPOSE:To take out high discharge capacity in a large electric current from the initial stage of actual use time by carrying out preliminary charging at a rated constant rate prior to charging and discharging processing of initial activation, and carrying out ageing processing for constant range time at a constant range temperature after charging and discharging are carried out. CONSTITUTION:A preliminary charging process of the second process is carried out until capacity becomes 5-100% of rated capacity in a temperature area of 15-30 deg.C, and in the next third process, charging and discharging are carried out on a battery obtained in the second process, and a positive electrode active material is activated, and battery capacity is increased up to rated capacity. The fourth process is an ageing process, and a battery obtained in the third process is left as it is in a temperature area of 30-60 deg.C for 6-48 hours. Thereby, viscosity of injected electrolyte is reduced, and this viscosity-reduced electrolyte infiltrates into a fine crack caused in the positive electrode active material or hydrogen storage alloy of a negative electrode, and as a result, an effective area of a positive electrode or the negative electrode contributive to battery reaction is increased. Thereby, activation of the positive electrode active material and the negative electrode is heightened, so that high discharge capacity can be taken out from the initial stage of discharge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sealed nickel-hydrogen secondary battery, and more specifically, a sealed nickel-hydrogen secondary battery capable of taking out a high discharge capacity from the initial stage of actual use. To a method of manufacturing.

[0002]

2. Description of the Related Art Recently, nickel-hydrogen secondary batteries have been attracting attention as high-capacity secondary batteries. This nickel-hydrogen secondary battery operates with hydrogen as a negative electrode active material, and usually has a negative electrode sheet formed by supporting a sheet-like conductive base material with a hydrogen storage alloy that reversibly stores and releases hydrogen. A positive electrode sheet formed by filling a conductive base material such as a sheet-like nickel porous body with nickel hydroxide that operates as a positive electrode active material, and an electrically insulating separator interposed between the both electrode sheets. Power generation element,

[0003]

[Outer 1]

Injecting an alkaline electrolyte such as an aqueous potassium hydroxide solution into the can,

[0005]

[Outside 2]

The entire structure is manufactured in a closed structure. By the way, the active material of the positive electrode incorporated in the above-mentioned battery is mainly composed of nickel hydroxide. But recently,
Furthermore, Co, CoO, Ni, etc. are added to improve the function as a positive electrode active material.

Among these additives, cobalt components such as Co and CoO enhance the conductivity of the whole positive electrode active material, and Ni functions as a conductive material, so that nickel hydroxide as an active material and a conductive group are used. It works to increase the conductivity with the material and improve the utilization rate of the positive electrode active material. The battery manufactured in this manner is then charged and discharged repeatedly at a predetermined current value to activate the positive electrode active material, and then charged to the rated capacity before shipment. It

[0008]

The degree of initial activation of the above-mentioned active material varies depending on the current used during charging and discharging and the number of repetitions of charging and discharging. This affects the discharge capacity of the battery when it is actually used. For example,
In the battery having the above-described structure, the initial stage of discharge during actual use is repeated in a state where the charge / discharge cycle of charging 150% of the rated value and then discharging the battery voltage to 1 V is repeated about 1 to 3 times. At a discharge rate as low as about 0.2 C, the rated discharge capacity is shown, but at a high discharge rate of 1 C or higher, the discharge capacity becomes low.

Therefore, in order to realize the rated discharge capacity in a stable state even at a large current in the initial stage of actual use, the charge / discharge cycle under the above-mentioned conditions is, for example, 10 times.
It is necessary to repeat the process more than once to further activate the active material. However, repeating the charge / discharge cycle a number of times is complicated in terms of work and causes a problem of increasing the overall manufacturing cost.

The present invention solves the above-mentioned problems in the initial activation treatment of the sealed nickel-hydrogen secondary battery, and even when the number of repetitions of the charge / discharge cycle is one, in the initial stage of actual use, An object of the present invention is to provide a method for producing a sealed nickel-hydrogen secondary battery capable of obtaining a stable rated discharge capacity even with a large current.

[0011]

In order to achieve the above object, in the present invention, a positive electrode carrying nickel hydroxide, a negative electrode carrying a hydrogen storage alloy and a separator arranged between the two electrodes are used. 15-
In the temperature range of 30 ° C., a step of precharging the sealed battery to a capacity of 5 to 100% of its rated capacity (hereinafter referred to as the second step); charging and discharging are repeated in the temperature range of 15 to 30 ° C. And increasing the capacity of the sealed battery to the rated capacity (hereinafter referred to as the third step); aging the obtained sealed battery in a temperature range of 30 to 60 ° C. for 6 to 48 hours (hereinafter, referred to as the third step). 4 steps); is provided as an essential step, and a method for manufacturing a sealed nickel-hydrogen secondary battery is provided.

In the method of the present invention, first, in the first step,
A sealed battery having a predetermined structure is manufactured according to a conventional method. As the positive electrode, for example, a positive electrode active material paste prepared by mixing nickel hydroxide powder, Co powder, CoO powder, Ni powder, or the like at a predetermined ratio, and further adding, for example, an aqueous solution of carboxymethyl cellulose to the sponge is used. A preferable example is one filled with a porous nickel porous body.

As a preferable example of the negative electrode, there may be mentioned one prepared by applying a slurry containing a predetermined hydrogen storage alloy powder and a carboxymethylcellulose aqueous solution to a punching nickel sheet. A porous and electrically insulating separator is interposed between the positive electrode and the negative electrode to form a power generating element, the power generating element is housed in a can body, and then a predetermined alkaline electrolyte is poured therein. By covering the can with a lid and sealing the whole, a sealed battery having a target structure is manufactured.

The second step is a step of precharging the sealed battery obtained in the first step. This preliminary charging is preferably performed within 14 hours after the end of the first step. This precharging prevents a situation in which the cobalt component in the positive electrode active material is excessively oxidized and a hydrogen storage alloy forming the negative electrode is excessively eluted during charge / discharge in the third step described later, Therefore, it is carried out for the purpose of suppressing an increase in battery internal pressure during charging and suppressing an internal short circuit of the battery.

Pre-charging is performed in the temperature range of 15 to 30 ° C. If the temperature is lower than 15 ° C., it is difficult to achieve the above effects, and if the temperature is higher than 30 ° C., the charging efficiency of the positive electrode decreases and it becomes impossible to secure a predetermined amount of pre-charging electricity. Is. Also, this preliminary charging
It is performed until it reaches 5 to 100% of the rated capacity. When the charge is less than 5%, the discharge capacity in the initial stage of the obtained battery cannot be increased even when the charge and discharge in the third step is performed, and conversely, when the charge is more than 100%, the above-mentioned preliminary This is because the purpose of charging cannot be achieved.

In the third step, the battery obtained in the second step is charged and discharged to activate the positive electrode active material, and at the same time, the capacity of the battery is increased to the rated capacity. In the present invention, this charging / discharging may be performed at least once. This is an effect brought about by combining the second step of the former stage and the fourth step of the latter stage. For example, current: 0.2C, 7.5
After being charged for 150 hours (150% of the rating), the battery may be discharged to 1V.

Prior to the above-mentioned third step, if the battery after the second step is left in the temperature range of, for example, 15 to 30 ° C. for at least 1 hour, the electrolytic solution is sufficiently infiltrated and the first step is performed. The effects of the three steps can be more effectively exhibited. The fourth step is a step of aging the battery having the rated capacity obtained in the third step. Specifically, 30-60 ℃
It is left in the temperature range of 6 to 48 hours.

By carrying out this aging step, the activity of the positive electrode active material is increased and the activity of the negative electrode is also increased, so that a high discharge capacity can be taken out from the initial stage of discharge. This means that when exposed to the above temperatures,
The viscosity of the injected electrolyte solution decreases, and the electrolyte solution with reduced viscosity penetrates into fine cracks generated in the positive electrode active material and the hydrogen storage alloy of the negative electrode during charge and discharge in the third step, and as a result, the battery It is considered that this is an effect brought about by increasing the effective areas of the positive electrode and the negative electrode that contribute to the reaction.

When the aging temperature is lower than 30 ° C., the viscosity of the electrolytic solution is not sufficiently lowered and the above effects cannot be obtained. If the aging temperature is higher than 60 ° C, the separator and the hydrogen storage alloy are deteriorated, which is inconvenient. When the aging time is shorter than 6 hours, the above effect cannot be obtained because the electrolyte solution is not sufficiently permeated into the negative electrode, and even when it is longer than 48 hours, the effect reaches saturation and is meaningless.

[0020]

Example: Ni (OH) ₂ powder 100 having a particle size of 1 to 60 μm
5 parts by weight of CoO powder having a particle size of 0.1 to 10 μm and 10 parts by weight of carbonyl nickel powder having a specific surface area of 1 to ³ m ² / g and a filament diameter of 1 μm or less are mixed with 1.2 parts by weight. % Aqueous solution of carboxymethyl cellulose was added to prepare a paste of the positive electrode active material.

Average pore diameter 0.3 mm, porosity 96%, length 72 m
A sponge-like nickel porous body with m, width 41 mm, and thickness 1.6 mm was prepared, filled with a certain amount of the above paste, dried at 80 ° C. for 1 hour, and further a pressure of 500 kg / cm ² was applied. The packing density of Ni (OH) ₂ , CoO and Ni
A positive electrode sheet having a thickness of 0.62 mm, which is 2.6 g / ml, was manufactured.

Next, by the arc melting method, the composition: MmNi
After producing a hydrogen storage alloy represented by _3.3 Co _1.0 Mn _0.4 Al _0.3 , this was pulverized to obtain an alloy powder under 150 mesh (Tyler sieve). Then, deionized water 1
A slurry comprising 400 parts by weight of the alloy powder, 60 parts by weight of Ni powder, and 1 part by weight of an aqueous solution of carboxymethyl cellulose was prepared with respect to 00 parts by weight, and a punching nickel sheet having a porosity of 38% (thickness 0.07 mm, hole diameter) was prepared. (1.5 mm) is soaked in each slurry and then pulled up, then dried in air and rolled at a pressure of ² ton / cm ² to give a total thickness of 0.4
The negative electrode sheet is mm.

A nylon sheet having a thickness of 0.18 mm and a porosity of 65% was sandwiched between the positive electrode sheet and the negative electrode sheet as a separator, and the whole was wound to produce a power generating element, which was then housed in a cylindrical container. An electrolyte solution consisting of potassium hydroxide, sodium hydroxide and lithium hydroxide with a specific gravity of 1.36 was poured, and the whole was sealed with a lid, AA size 1100 m
I used Ah batteries. In this sealed cylindrical battery, the group tolerance is 94% and the space volume occupied by the electrolyte is 95%.
%It has become.

This battery was precharged at a temperature of 20 ° C. under a current of 0.2 C for 1 hour, and was charged to 20% of the rated value. Then, after leaving it at 20 ° C. for 16 hours, it was charged at 0.2 ° C. for 7.5 hours and discharged at 0.2 C to 1 V at a temperature of 20 ° C. Then, the battery was left to stand in a constant temperature bath at 40 ° C. for 24 hours for aging.

The battery thus obtained was charged at 0.2 C for 7.5 hours and then discharged to 1.0 V at 1 C. The discharge capacity was 1045 mAh, and an initial utilization rate of about 95% was obtained. . For comparison, batteries were prepared in the same manner as in Example, except that the above-mentioned pre-charging was not performed,
The internal pressure of the battery at the end of charging at 4.5 hours after 1C was 22 kgf / cm ² , and the internal pressure was 12 kgf / cm 2.
Rose to ² . In the case of the battery of the present invention, the internal pressure at the end of charging was 10 kgf / cm ² .

As another comparison, a battery was manufactured in the same manner as in Example except that the aging treatment was not performed, and the discharge capacity at 1C of the battery was measured and found to be 880 mAh. The initial utilization rate dropped to 80%.

[0027]

As is apparent from the above description, according to the method of the present invention, it is possible to take out a high discharge capacity with a large current from the initial stage of actual use and to keep the internal pressure low. This is an effect brought about by performing a pre-charge of about 5 to 100% of the rating prior to the charge / discharge treatment of the initial activation and performing an aging treatment at 30-60 ° C. for 6-48 hours after the charge / discharge. .

Claims (1)

[Claims] 1. A power generating element comprising a positive electrode supporting nickel hydroxide, a negative electrode supporting a hydrogen storage alloy, and a separator arranged between the two electrodes is housed in a can body, and an alkaline electrolyte is placed in the can body. Step of injecting and then sealing to make a sealed battery; step of precharging the sealed battery to a capacity of 5 to 100% of its rated capacity in a temperature range of 15 to 30 ° C; temperature of 15 to 30 ° C Step of repeating charge and discharge in the temperature range to increase the capacity of the sealed battery to the rated capacity; the obtained sealed battery in a temperature range of 30 to 60 ° C. for 6 to 4
A method of manufacturing a sealed nickel-hydrogen secondary battery, which comprises, as an essential step, a step of aging for 8 hours.