JPH0482170A - Manufacture of angular nickel hydrogen storage battery - Google Patents

Abstract

PURPOSE:To eliminate increase in thickness of battery with that of electrode plate group and to improve injecting property of electrolite by allowing a metal case to contain an electrode plate group with a thickness being 95% or less of the inner diameter of the metal case in the laminating direction, performing charging/discharging by one cycle after enclosing the metal case, and compressing the metal case in the thickness direction of the electrode plate group. CONSTITUTION:An electrode plate group is accommodated in a metal case 21 and an alkaline electrolyte is injected. After that, a positive terminal 29 and elastic body 26 are provided in an insulating gasket 27, and a sealing member accommodating a metallic cover plate 28 connected with a positive electrode plate 24 is pressed in an opening of the case 21. Collector terminals 31 and 30 are formed on the electrode plates 24 and 22, respectively and are collectively connected with the cover plate 28 and the case 21. The opening of the metal case 21 is folded for sealing, to thus obtain a battery. The battery is charged, and discharged with a current of 1CmA to be 1V in battery voltage, after which the side surfaces of the case 21 is compressed from the thickness direction of the electrode plate group by a press such that the thickness of the pressed portion is to be 95% of that of the battery.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a prismatic battery in which a positive electrode plate and a negative electrode plate are laminated with a separator in between. The present invention relates to a method for manufacturing a prismatic nickel-metal hydride storage battery.

(Prior Art) In recent years, as devices become smaller and lighter, prismatic batteries with high volumetric efficiency have been developed. Furthermore, in recent years, development of alkaline storage batteries using a hydrogen-absorbing metal in the negative electrode has become active in order to further increase the capacity of cylindrical batteries.

By the way, as a conventional prismatic alkaline storage battery, for example, a nickel-cadmium storage battery, one having the structure shown in FIG. 5 is known. That is, in FIG. 5, 1 is a rectangular parallelepiped metal case container with a bottom that also serves as a negative electrode terminal. Inside this container 1, a power generation element 5 is arranged, which is constructed by laminating in this order a negative electrode plate 2 mainly composed of cadmium, a separator 3, and a positive electrode plate 4 mainly composed of nickel oxide. There is. This positive electrode plate 4. A current collector terminal II, 10 is formed on each negative electrode plate 2, and a current collector terminal 11 is formed on each of the negative electrode plates 2.
and 10 are collectively connected to the metal lid 8 and the metal case container 1, respectively. Reference numeral 9 denotes a sealing plate containing an elastic body 6 having a mechanism for discharging gas to the outside when the internal pressure of the battery increases. Each member such as the power generation element inside 1 is sealed.

Among the above-mentioned power generation elements, a sintered electrode plate in which a sintered body of nickel powder is impregnated and filled with a solution active material has been used as the positive electrode plate, but conventionally, the electrode capacity density is up to 450 mA.
h/cc, and in order to achieve even higher capacity, it has become necessary to improve the capacity density.

Therefore, a paste-type electrode plate was developed that uses a method of directly filling an active material into a three-dimensional structure substrate such as foamed metal or sintered fiber, which is advantageous in increasing the electrode capacity density. A capacitance density of is obtained.

(Problems to be Solved by the Invention) In conventional nickel-cadmium storage batteries that employ nickel oxide for the positive electrode and cadmium oxide and metal cadmium for the negative electrode, the thickness of the positive electrode increases and the thickness of the negative electrode decreases during the charging process. Moreover, in the discharge process, each has an opposite tendency.

On the other hand, in a nickel-metal hydride alkaline storage battery that has a hydrogen storage alloy as its main component in the negative electrode, the hydrogen storage alloy absorbs hydrogen in the negative electrode during the charging process, so the thickness of the negative electrode increases slightly, and this overlaps with the increase in the thickness of the positive electrode. The increase in plate group thickness is more pronounced than in nickel-cadmium batteries. This phenomenon is more pronounced in non-sintered positive electrode plates, such as paste-type electrode plates, than in sintered positive electrode plates.Furthermore, if the positive electrode is an unformed electrode, chemical formation occurs during the first charge. Since the thickness increases significantly, the electrolyte may be pushed out of the separator and may be discharged to the outside through the safety valve. This swelling of the electrodes causes the battery to swell in the thickness direction, which may cause alkaline electrolyte leakage in prismatic batteries in which the opening end of the metal case is caulked as a sealing method.

Further, when a high-capacity battery is constructed using a non-sintered positive electrode plate, for example, a paste-type positive electrode plate, the capacity density of the positive electrode plate is required to be 500 mAh/cc or more.

The paste-type electrode plate is formed by applying a paste-like material containing an active material to a porous substrate and drying it.
Swelling occurs during charging and discharging, and as a result, the amount of electrolyte required is larger than in the case of sintered electrode plates, but unlike the case of cylindrical batteries, prismatic batteries have a spiral electrode group. Since there is no space corresponding to the winding core, the injectability of the electrolyte is extremely poor. In addition, in the event that a shortage of electrolyte occurs, uneven electrode reactions will occur, resulting in insufficient battery capacity and imbalance in electrode capacity due to electrode deterioration, leading to a reduction in charge/discharge cycle life. .

Furthermore, as mentioned above, the non-sintered electrode plates swell and take electrolyte from the separator into the electrode, making it difficult to secure an appropriate amount of electrolyte in the separator.
This may reduce the charge/discharge cycle life.
There were various problems.

The present invention was made to solve the above problems, and
The purpose is to provide a prismatic nickel-metal hydride storage battery that does not have an increase in battery thickness due to an increase in the thickness of the electrode plate group, improves the injectability of electrolyte, has good discharge characteristics, and exhibits little cycle deterioration.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a strip-shaped nickel positive electrode plate and a negative electrode plate mainly composed of a hydrogen storage metal in a bottomed rectangular cylindrical metal case that also serves as a negative polarity terminal. In the manufacturing method of a prismatic nickel-metal hydride storage battery containing a group of electrode plates and an alkaline electrolyte, which are stacked alternately in the horizontal direction with separators in between, the positive electrode is an unformed, non-sintered type with an electrode capacity density of 500 mAh/cc or more. It is equipped with a nickel electrode, and the thickness of the electrode plate group before insertion into the metal case is 95% or less of the inner diameter in the stacking direction of the metal case. This is characterized by compressing the metal case from the thickness direction of the group to reduce its thickness.

(Function) According to the present invention, it is possible to suppress the swelling of the square metal case in the thickness direction, to easily inject an appropriate amount of electrolyte, and to maintain the electrolyte retention property of the separator in a good state. Therefore, a high capacity prismatic battery with good charge/discharge cycle characteristics and large discharge characteristics and excellent space efficiency can be obtained.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 is a longitudinal cross-sectional view of a prismatic nickel-metal hydride battery, which is an example of the present invention, immediately after the power generation element is housed.

As shown in the figure, a nickel substrate having a three-dimensional network structure is filled with a paste-like active material mainly composed of nickel hydroxide in a bag-like separator 23 with a thickness of 0.2 mm.

A dried and pressed unformed positive electrode plate 24 with an electrode capacity density of 500 mAh/cc and a paste-like active material mainly composed of a hydrogen storage alloy were filled into a punched metal substrate and dried.

The pressed negative electrode plates 22 are stacked alternately to form the electrode plate group 2.
5 was formed. At this time, the thickness of the positive and negative electrodes was adjusted so that the capacity balance between the positive electrode and the negative electrode was appropriate, and the thickness of the electrode plate group was 95% of the thickness of the inner surface of the metal case. Thereafter, the electrode group is housed in a bottomed rectangular metal case 21 with a thickness of 0.4 mm obtained by deep drawing a steel plate with nickel plating on both sides, and after injecting an alkaline electrolyte, it is inserted into an insulating gasket 27. Positive electrode terminal 299 elastic body 26
A sealing member containing a metal cover plate 28 connected to the positive electrode plate 24 is press-fitted into the opening of the metal case 21 and placed. This positive electrode plate 24. Each negative electrode plate 22 has a current collector terminal 3.
1.30 are formed, and the respective current collecting terminals 31 and 30 are collectively connected to the metal lid body 28 and the metal case 21, respectively. Then, the opening of the metal case 21 was bent and sealed to complete a sealed prismatic battery.

Then, continue to charge for 8 hours with 0.2Cm human current,
After discharging with a current of ICm^ until the battery voltage reaches 1■, press the sides of the metal case 21 from the direction of the thickness of the electrode plate group so that the thickness of the pressed part becomes 95% of the thickness of the battery. did. A cross-sectional view of this state is shown in FIG.

Next, in order to confirm the effects of the present invention, the following batteries were manufactured using the same electrode configuration as in the above example, and the battery properties of each battery at the time of manufacture were examined.

(1) If the metal case is not compressed from the thickness direction (
Comparative Example 1), (2) When the case was compressed from the thickness direction immediately after sealing (Comparative Example 2), (3) After sealing, the case was compressed from the thickness direction after 5 similar charge/discharge cycles. (Example 2), (4) A case in which the metal case was compressed in advance, the electrode plate group was inserted into the case whose thickness was reduced, and then the case was sealed (Comparative Example 3).

When the battery properties of these batteries were compared, the battery (1) in which the metal case was not compressed in the thickness direction swelled by about 0.1 to 0.15 mm after charging and discharging. (2)
If the metal case was compressed immediately after being sealed, the electrolyte from the safety valve could spout out during compression.

When these were subjected to 5 cycles of charging and discharging as described in (3) and then the metal case was compressed, a battery with good characteristics as in the above example was obtained. In the case of (4), the electrode group is inserted into a case whose thickness has been reduced in advance, which may cause the electrodes to crumble and cause short circuits due to the fine powder. , the advantage of high capacity as a nickel-metal hydride storage battery will be lost.

In addition, after charging these batteries at 0.2CmA for 7 hours, the battery capacity at each discharge rate when the discharge current was set stepwise is shown in Figure 3. C
Figure 4 shows the battery capacity retention rate when repeated cycles of discharging at mA until the battery voltage reached 1. Regarding the discharge characteristics, the discharge end voltage is 800 mV, the capacity at each discharge rate is 100% at 0.2 CmA discharge, and the discharge capacity after initial conditioning in the charge/discharge cycle is 100%. The capacity retention rate (%) after cycling is shown.

As can be seen from the above results, all of the Examples of the present invention have better discharge characteristics than Comparative Examples 1 and 2, and also have better charge/discharge cycle characteristics. This is because the metal case is compressed in the thickness direction of the electrode plate group, which reduces the distance between the positive and negative electrodes.By suppressing the paste-type electrode plate, which is relatively easy to collapse, the swelling of the electrode itself is suppressed. This is because an appropriate amount of electrolyte can be retained in the separator. Furthermore, it brings about good effects in terms of vibration resistance and impact resistance.

Although punched metal was used as the substrate of the negative electrode plate in the above embodiment, it may be filled in a two-dimensional structured substrate such as wire mesh or lath metal, or a three-dimensional structured substrate such as foamed metal.

(Effects of the Invention) As explained above, according to the present invention, the prismatic nickel-metal hydride storage battery has a long life and high energy density, suppresses the swelling of the container due to the swelling of the power generation element during charging and discharging, and has excellent large current discharge characteristics. can be provided.

[Brief explanation of the drawing]

Figure 17 is a vertical cross-sectional view of a prismatic nickel-metal hydride battery, which is an embodiment of the present invention, immediately after the power generation element is housed, and Figure 2 is a view of the metal case from the thickness direction of the electrode plate after one cycle of charging and discharging the battery in Figure 1. FIG. 3 is a diagram showing the retention rate of discharge capacity at each discharge rate of the batteries of Examples and Comparative Examples of the present invention, and FIG. FIG. 5, a diagram showing the maintenance rate, is a longitudinal cross-sectional view of a conventional prismatic nickel-cadmium storage battery. 21... Square metal case with bottom 22... Negative electrode plate 23... Separator 24... Positive electrode plate 25... Electrode plate group 26... Elastic body 27... Insulating gasket 28... Metallic Lid plate 29...Positive terminal 30.31...Collection terminal (8733) Agent: Patent attorney Yoshiaki Inomata (and others)
1 person) Rokudenden A (c to A) No. 1

Claims (1)

[Claims] (1) An electrode plate consisting of a strip-shaped nickel positive electrode plate and a negative electrode plate whose main component is a hydrogen-absorbing metal, which are alternately stacked horizontally with a separator in between, in a bottomed rectangular cylindrical metal case that also serves as a negative polarity terminal. In a method for manufacturing a prismatic nickel-metal hydride storage battery containing a battery pack and an alkaline electrolyte, the positive electrode is an unformed, non-sintered nickel electrode with an electrode capacity density of 500 mAh/cc or more, and the thickness of the electrode plate group before insertion into the metal case is It is equipped with a group of electrode plates that is 95% or less of the inner diameter of the metal case in the stacking direction, and after being sealed and charged and discharged for at least one cycle, the metal case is compressed from the thickness direction of the plate group to reduce its thickness. A manufacturing method for a prismatic nickel-metal hydride storage battery.