JP2988974B2 - Prismatic nickel-metal hydride storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a prismatic battery in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, particularly a hydrogen storage metal for the negative electrode, a nickel oxide for the positive electrode, and a nickel oxide for the positive electrode. The present invention relates to a prismatic nickel-metal hydride storage battery.

(Prior Art) In recent years, prismatic batteries with high volumetric efficiency have been developed along with the reduction in size and weight of devices. Recently, alkaline storage batteries using a hydrogen storage metal for the negative electrode have been actively developed for the purpose of further increasing the capacity of cylindrical batteries.

Meanwhile, a conventional prismatic alkaline storage battery, for example, a nickel cadmium storage battery having a structure shown in FIG. 4 is known. That is, in FIG. 4, reference numeral 1 denotes a bottomed rectangular parallelepiped metal case container also serving as a negative electrode terminal.
Inside the container 1, there is disposed a power generating element 5 configured by laminating a negative electrode plate 2 mainly composed of cadmium, a separator 3, and a positive electrode plate 4 mainly composed of nickel oxide in this order. I have. Current collecting terminals 11 and 10 are formed on the positive electrode plate 4 and the negative electrode plate 2, respectively.
And 10 are collectively a metal cover 8 and a metal case 1 respectively.
It is connected to the. Reference numeral 9 denotes a sealing plate having a built-in elastic body 6 having a mechanism for discharging gas to the outside when the internal pressure of the battery is increased. The sealing plate 9 is formed by caulking an opening end of the metal case 1 via an insulating gasket 7 to thereby provide a container. Each member such as a power generation element in 1 is sealed.

Among the above-mentioned power generating elements, as the positive electrode plate, a sintered type electrode plate in which a sintered body of nickel powder is impregnated and filled with a solution-type active material has been used, but conventionally the electrode capacity density is up to 450 mAh / c.
It is on the order of c, and it has become necessary to increase the capacity density in order to further increase the capacity.

Therefore, a paste-type electrode plate was developed by directly filling the 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 capacity density has been obtained.

(Problems to be Solved by the Invention) In a conventional nickel-cadmium storage battery employing 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 in the charging process. In the discharge process, each has the opposite tendency. On the other hand, in a nickel-metal hydride storage battery having a hydrogen storage alloy as a main component in the negative electrode,
In the charging process, the thickness of the negative electrode slightly increases in the negative electrode because the hydrogen storage alloy absorbs hydrogen, and the thickness of the electrode plate group increases with the increase in the positive electrode thickness more remarkably than in the nickel cadmium battery. This phenomenon is more prominent in non-sintered electrode plates represented by paste electrode plates than in sintered electrode plates,
Further, when the positive electrode is an unformed electrode, the thickness is greatly increased by the formation at the time of the first charge, so that the electrolyte may be pushed out from the separator, and the electrolyte may be discharged outside through the safety valve. Since the battery swells in the thickness direction due to such swelling of the electrodes, a rectangular battery employing caulking of the opening end of the metal case as a sealing method may cause leakage of the alkaline electrolyte.

When a high-capacity battery is to be constructed using a non-sintered positive electrode plate, for example, a paste-type electrode plate, the capacity density of the positive electrode plate is required to be 500 mAh / cc or more. Since the paste-type electrode plate is formed by applying and drying a paste-like material containing an active material on a porous substrate, swelling is caused by charge and discharge, and as a result, the required amount of electrolyte is a sintered electrode. However, unlike the case of a cylindrical battery, the rectangular battery does not have a space corresponding to the core of the spiral electrode group, so the injectability of the electrolyte is extremely high. Inferior to In the event that the electrolyte is insufficient, the electrode reaction becomes non-uniform, causing a shortage of the battery capacity and an imbalance in the electrode capacity due to the deterioration of the electrode, resulting in a reduction in the charge / discharge cycle life. . further,
As described above, since the non-sintered electrode plate swells and takes the electrolyte from the separator into the electrode, it becomes difficult to secure an appropriate amount of the electrolyte in the separator, and the charge / discharge cycle life is shortened. There have been various problems, such as the situation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to improve the injectability of the electrolyte without increasing the battery thickness due to the increase in the thickness of the electrode plate group, and to improve the discharge characteristics and cycle deterioration. To provide a prismatic nickel-metal hydride storage battery having a small size.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides 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 also serving as a negative electrode terminal. And a prismatic nickel-metal hydride storage battery containing an alkaline electrolyte, which are formed by alternately laminating the electrodes through the separator in the horizontal direction, and the positive electrode has an electrode capacity density of 500 mAh / cc or more. A nickel electrode is provided, and the positive electrode plate and the negative electrode plate before insertion of the metal case are respectively pressed, and the thickness of the group of electrode plates in which the pressed electrode plates are stacked is the inner diameter of the metal case in the stacking direction. 90% or less.

(Operation) According to the present invention, swelling in the thickness direction of the rectangular metal case is suppressed, and it becomes easy to inject an appropriate amount of electrolyte, and it is possible to maintain the electrolyte retention of the separator in a good state. Therefore, a high-capacity prismatic battery having good charge-discharge cycle characteristics and large discharge characteristics and excellent space efficiency can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a longitudinal sectional view of a prismatic nickel-metal hydride battery according to an embodiment of the present invention.

As shown in the figure, a paste-like active material mainly composed of nickel hydroxide was filled in a 0.2 mm thick bag-like separator 23 on a nickel substrate having a three-dimensional network structure, dried and pressed, and had an electrode capacity density of 500 mAh / cc. An electrode group 25 was formed by alternately stacking the unformed positive electrode plate 24 and the negative electrode plate 22 filled with a paste-like active material mainly composed of a hydrogen storage alloy in a punched metal substrate, dried and pressed. 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 90% of the thickness of the inner surface of the metal case. Current collecting terminals 31 and 30 are formed on the positive electrode plate 24 and the negative electrode plate 22, respectively.The respective current collecting terminals 31 and 30 are collectively connected to the metal lid 28 and the metal case 21, respectively. . Thereafter, the electrode group is housed in a bottomed square metal case 21 of 0.4 mm pressure obtained by deep drawing of a steel plate plated with nickel on both sides, and after pouring an alkaline electrolyte, the positive electrode is placed in an insulating gasket 27. A sealing member having a terminal 29 and an elastic body 26 and containing a metallic lid plate 28 connected to the positive electrode 24 is pressed into the opening of the metal case 21 and placed. Then, the opening of the metal case 21 was bent and sealed to complete a sealed rectangular battery.

Next, using the positive electrode of the electrode capacity density shown in the following table, to manufacture each of 20 square nickel-metal hydride storage batteries in which the electrode plate group thickness is changed stepwise as shown below, with the charge and discharge cycle, 1) change in battery thickness, 2) presence or absence of liquid leakage, 3)
The change of short circuit rate and discharge capacity in charge / discharge cycle was investigated. The results of the above 1) to 3) are shown in the following table, and the results of the discharge capacity retention ratio in the charge / discharge cycle are shown in FIG.

In addition, the discharge capacity retention rate in the charge and discharge cycle of the battery is:
The cycle of charging these batteries at 0.2 CmA for 7 hours and discharging at 1 CmA until the battery voltage becomes 1 V is repeated, and the discharge capacity after the initial condition is 100%, and the capacity retention rate after the cycle is shown. is there.

As can be seen from the above results, in each of the examples of the present invention, the injection time was short, the swelling of the metal case was small, and no internal short circuit occurred. Further, the decrease in discharge capacity due to cycle charge / discharge is also superior to Comparative Examples 1 and 2. In Comparative Examples 1 and 2, the capacity after cycle charge / discharge was reduced because the electrolyte leaked from the safety valve due to a decrease in the amount of electrolyte in the battery and the outermost when the electrode group was inserted. The active material tends to be short-circuited by the shaved differential. This is because it can be done. Further, the present invention brings about a good effect in terms of vibration resistance and impact resistance.

In the above-described embodiment, punched metal is used as the substrate of the negative electrode plate. However, a two-dimensional structure substrate such as a wire mesh or a lath metal or a three-dimensional structure substrate such as a foamed metal may be filled.

(Effects of the Invention) As described above, according to the present invention, the swelling of the container accompanying the swelling of the power generation element during charge and discharge can be prevented from leaking the electrolytic solution, and the active material can be stored when the power generation element is stored. It is possible to provide a prismatic nickel-metal hydride battery having excellent cycle life and high energy density, which can prevent falling off and thereby prevent internal short circuit.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a prismatic nickel-metal hydride battery according to one embodiment of the present invention immediately after storage of a power generating element, FIG. 2 is a longitudinal sectional view showing a state of the battery of FIG. FIG. 4 is a diagram showing a retention rate of a battery capacity accompanying cycle charge / discharge, and FIG. 4 is a longitudinal sectional view of a conventional square 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 cover plate 29 ... Positive electrode terminal 30,31 …… Current collecting terminal

Continuation of front page (56) References JP-A-62-126566 (JP, A) JP-A-62-234876 (JP, A) JP-A-4-82170 (JP, A) (58) Fields studied (Int .Cl. ⁶ , DB name) H01M 10/30 H01M 10/34 H01M 10/28

Claims (1)

(57) [Claims] 1. A belt-shaped nickel positive electrode plate and a negative electrode plate mainly composed of a hydrogen storage metal are alternately overlapped with each other in a lateral direction via a separator in a bottomed rectangular cylindrical metal case also serving as a negative terminal. In a prismatic nickel-metal hydride storage battery containing an electrode group and an alkaline electrolyte, the positive electrode has an electrode capacity density of 50
An electrode group comprising an unformed non-sintered nickel electrode of 0 mAh / cc or more, and pressing the positive electrode plate and the negative electrode plate before inserting the metal case, and stacking the pressed electrode plates. Wherein the thickness of the metal case in the stacking direction is 90% or less of the inner diameter of the metal case in the stacking direction.