JPH0231978Y2 - - Google Patents

Description

[Detailed Description of the Invention] <<Industrial Application Field>> This invention relates to an improvement of a flat battery that is generally referred to as a button type or coin type battery.

<<Prior Art>> FIG. 1 shows the assembly process of a flat battery with a typical conventional structure. This battery includes a flat bottomed cylindrical positive electrode can 10, a disk-shaped positive electrode mixture 16 crimped to the inner bottom surface of the positive electrode can 10, and an electrolytic solution placed on the top surface of the positive electrode mixture 16. A positive electrode side assembly consisting of a separator 18 including a plate-shaped negative electrode terminal plate 12, a disc-shaped negative electrode 20 crimped to the inner surface of this negative electrode terminal plate 12, and a negative electrode 20 fitted to the periphery of the negative electrode terminal plate 12. Attached annular sealing gasket 14
The negative electrode side assembly consisting of the above is fitted onto the inner circumferential surface and inner bottom surface of the positive electrode can 10, and the opening edge portion of the positive electrode can 10 is curled inward to compress the sealing gasket 14, thereby sealing the battery. It has a structure that seals the inside.

<<Problems to be solved by the invention>> The above-mentioned conventional flat battery had a problem in that air was easily trapped inside the battery. If the battery case is sealed with air remaining in the separator 18, the internal resistance of the battery will increase due to the gap, and in extreme cases, this will cause large variations in the total height of the battery.

The present inventors have discovered that this air entrapment occurs in the following manner when the above-described negative electrode assembly is fitted to the positive electrode assembly.

The sealing gasket 14 is made of plastic having appropriate elasticity, and has a shape that encloses the peripheral edge of the negative electrode terminal plate 12 with an inner tube 14a and an outer tube 14b. This inner cylinder 10a has a tapered shape.
In the assembly process shown in FIG. 1, when the peripheral edge of the separator 18 containing a large amount of electrolyte comes into close contact with the inner surface of the inner cylinder 14a, the recessed space of the negative terminal plate 12 is closed by this annular contact area. Become. When the negative electrode assembly is strongly pushed into the positive electrode assembly, the air in the space that is about to be closed will pass through the gap created at the contact area and the pores of the separator 18 itself, and the air will leak between the positive electrode can 10 and the gasket 14. Escape to the outside through the gap between them. However, with conventional models, this air removal was not done well, and a large amount of air was likely to be trapped due to looseness during assembly.

As a countermeasure to the above problem, it has been proposed to reduce the diameter of the separator 18 to weaken the space-occluding property caused by this. However, this method causes a new problem in that an internal short circuit is likely to occur where the positive electrode mixture 16 and the negative electrode 20 are in direct contact with each other.

Furthermore, if the diameter of the positive electrode mixture is made smaller, a space is created around it and the pressure increase is alleviated, so it is also proposed to reduce the diameter of the positive electrode mixture 16 to prevent the above-mentioned space blockage from occurring. It was done. However, with this method, the filling amount of the positive electrode mixture is significantly reduced.

It has also been proposed to make the separator 18 extremely thin so that a gap is easily formed between it and the inner cylinder 14a of the gasket, and to increase its air permeability so that air can escape smoothly. However, with this method, the reliability as a separator is significantly lowered, and the electrolyte retention performance is also lowered.

This idea was devised in view of the conventional problems mentioned above, and its purpose was to eliminate the above-mentioned air entrapment during battery assembly by means that do not adversely affect battery performance, and to provide stable battery construction with low internal resistance. The purpose of this invention is to make it possible to realize a flat battery with improved performance.

<Means for Solving the Problems> In the flat battery according to this invention, the sealing gasket has an inner cylinder and an outer cylinder that embrace the periphery of the negative electrode terminal plate, and the sealing gasket has an inner cylinder and an outer cylinder. It is characterized by the formation of a large number of vertical grooves for air venting along the axial direction.

<<Operation>> In this invention, when the above-mentioned negative electrode side assembly is fitted to the positive electrode side assembly, even if the peripheral edge of the separator containing the electrolyte contacts the inner surface of the inner cylinder of the sealing gasket, the inner surface of the inner cylinder Since the above-mentioned vertical grooves are formed, the vertical grooves serve as an escape route for the air in the internal space that is about to be blocked, and the air smoothly escapes to the outside through this.

<<Example>> Fig. 2 is a diagram showing the assembly process of a flat battery to which the present invention is applied, and Fig. 3 shows the shape of a sealing gasket which is the main part of the present invention.

The basic structure of the flat battery of this invention is the same as the conventional one, including a flat bottomed cylindrical positive electrode can 10 and a disk-shaped positive electrode mixture 1 crimped onto the inner bottom surface of the positive electrode can 10.
6 and a separator 18 containing an electrolytic solution placed on the upper surface of this positive electrode mixture 16, and a dish-shaped negative electrode terminal plate 12 and a separator 18 that is crimped onto the inner surface of this negative electrode terminal plate 12. a disk-shaped negative electrode 20;
A negative electrode side assembly consisting of an annular sealing gasket 14 fitted and attached to the peripheral edge of the negative electrode terminal plate 12 is fitted to the inner peripheral surface and inner bottom surface of the positive electrode can 10, and the positive electrode can 1
By curling the opening edge portion of 0 inward, the sealing gasket 14 is compressed and the inside of the battery is sealed.

Specifically, in a non-aqueous electrolyte battery, the positive electrode can 10 and the negative electrode terminal plate 12 are made of stainless steel plates. The sealing gasket 14 is made of polyolefin plastic having appropriate elasticity, and has an inner cylinder 14a and an outer cylinder 14b that enclose the periphery of the negative electrode terminal plate 12. The positive electrode mixture 16 is made by adding a conductive agent and a binder to manganese dioxide, kneading and molding the mixture. As the negative electrode 20, a lithium disk is used. The separator 18 is made of polypropylene nonwoven fabric, and is impregnated with a non-aqueous electrolyte.

Particularly in this invention, as shown in detail in FIGS. 2 and 3, the inner cylinder 1 of the sealing gasket 14 is
A large number of vertical grooves 14c for venting air are formed along the axial direction on the inner surface of 4a. The inner cylinder 14a is formed in a tapered shape, and vertical grooves 14c are formed in the tapered inner surface radially and in the vertical direction. This vertical groove 14c is continuously formed so as to reach the bottom surface of the sealing gasket 14 from the upper edge of the inner cylinder 14a. Sealing gasket 14
The vertical grooves 14c can be formed at the same time during the integral molding.

Since the vertical groove 14c is formed on the inner surface of the inner cylinder 14a of the sealing gasket 14 in this way, the negative electrode terminal plate 12, the negative electrode 2
0. When fitting the negative electrode side assembly consisting of the sealing gasket 14, the peripheral edge of the separator 18 containing a large amount of electrolyte comes into contact with the inner surface of the gasket inner cylinder 14a, and the recessed space on the negative electrode terminal plate 12 side is closed. Even if the gasket 14 is about to be closed, the vertical grooves 14c ensure an escape route for air to reach the bottom side of the sealing gasket 14 from the recessed space. Therefore, when the negative electrode assembly is strongly pushed in, the air in the recessed space is easily discharged through the vertical groove 14c and is discharged to the outside through the gap between the sealing gasket 14 and the positive electrode can 10. As a result, air is no longer trapped in the separator 18.

The effectiveness of this device was confirmed through the following comparative tests. Fifty CR2025 (diameter 20 mm, total thickness 2.5 mm) flat lithium batteries were fabricated, each with the conventional structure shown in Figure 1 and the invented one shown in Figure 2, and their internal resistances were calculated. It was measured.
As a result, the average value of internal resistance was 13.2 compared to the conventional one.
Ω, whereas in the case of the present invention, it was clearly smaller at 9.3Ω. Also, the standard deviation of internal resistance is
While the conventional one had a relatively large variation of 1.9Ω, the inventive one had a very small variation of 0.6Ω.

In the above embodiment, the bottom of the sealing gasket 14 is in contact with the inner bottom surface of the positive electrode can 10, and is compressed using this as a seat. The present invention is not limited to this structure. Another typical structure of a flat battery is a structure in which the entire inner bottom surface of the positive electrode can is filled with the positive electrode mixture, and the bottom surface of the sealing gasket is in contact with the upper surface of the positive electrode mixture. The present invention can also be applied to this structure in the same manner as described above, and the same effects as described above can be obtained.

<<Effects of the invention>> As explained in detail above, according to this invention, by the simple means of forming a large number of vertical grooves on the inner surface of the inner cylinder of the sealing gasket, it can be achieved without any disadvantages in battery performance. Air is effectively discharged during assembly, eliminating harmful air entrapment phenomena, and realizing a flat battery with low internal resistance and stable performance.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the assembly process of a conventional flat battery, FIG. 2 is a cross-sectional view showing the assembly process of a flat battery according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view of the sealing gasket in FIG. FIG. DESCRIPTION OF SYMBOLS 10... Positive electrode can, 12... Negative electrode terminal plate, 14... Sealing gasket, 14a... Inner cylinder, 14b... Outer cylinder, 14
c... Vertical groove, 16... Positive electrode mixture, 18... Separator,
20...Negative electrode.

Claims (1)

[Scope of utility model registration request] The positive electrode side consists of a flat cylindrical positive electrode can with a bottom, a disk-shaped positive electrode mixture crimped to the inner bottom surface of the positive electrode can, and a separator containing an electrolyte placed on the top surface of this positive electrode mixture. For the assembled product, there is a negative electrode side assembly consisting of a dish-shaped negative electrode terminal plate, a disc-shaped negative electrode crimped to the inner surface of the negative electrode terminal plate, and an annular sealing gasket fitted and attached to the periphery of the negative electrode terminal plate. In a flat battery having a structure in which the product is fitted into the inner periphery of the positive electrode can and the opening edge of the positive electrode can is curled inward to compress the sealing gasket and seal the inside of the battery. , the sealing gasket has an inner cylinder and an outer cylinder that embrace the periphery of the negative terminal plate, and a number of vertical grooves for air venting are formed on the inner surface of the inner cylinder along its axial direction. flat battery.