JPH0427675B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a thermoplastic resin sealing material processed into a window frame shape on the peripheral surfaces of a pair of opposing battery containers, and the sealing material is sealed by thermal welding. The present invention relates to an improvement in a flat battery in which a power generation element is housed in a battery chamber formed by a battery.

Structure of conventional example and its problems Figure 1 shows a cross-sectional view of each component of a typical battery that has been conventionally proposed as this type of flat battery, and Figure 2 shows a cross-sectional view of the configured battery. shows.

In Figures 1 and 2, 1 is a stainless steel foil negative electrode container, 2 is a negative lithium electrode crimped to the container 1, and 3 is a polypropylene nonwoven fabric separator crimped to the negative electrode 2, which seals the battery. Prior to this, they are integrated as shown in Figure 1.

4 is a positive electrode container made of stainless steel foil, and 5 is a positive electrode mixture layer having manganese dioxide as an active material, which is in close contact with the container 4, and both are integrated as shown in FIG. 1 before constructing a battery. 6 is a polyethylene sealing material processed into a window frame shape.

The separator 3 and the positive electrode mixture layer 5 are impregnated with an electrolytic solution in which lithium perchlorate is dissolved in propylene carbonate, and each of these battery elements is stacked and the peripheral portion is pressurized and heated to form a sealing material 6. Positive electrode container 4
The state shown in FIG. 2 is obtained by heat welding and sealing the peripheral surfaces of the negative electrode container 1. Fig. 2 shows a state in which the sealing material 6 flows and deforms due to melting or softening during thermal welding, and extends into the outer circumference 6' of the battery and the battery compartment 6''. ,
A particular problem is that the sealing material 6'' extending into the battery chamber reduces the space volume inside the battery chamber and causes the battery to expand.An even more serious problem is that the sealing material 6'' has heated up and flowed. 6 compresses and deforms the end portion 3' of the separator 3, melts or softens and breaks, and also presses and deforms the end face of the positive electrode mixture layer 5, causing the mixture to fall off. The outer periphery or the fallen part of the positive electrode mixture layer 5 comes into contact with the negative electrode 2 or the negative electrode container 1 through the deformed or broken part 3' of the separator 3, causing an internal short circuit.

In order to avoid these problems, in anticipation of the extension of the sealing material 6 into the battery chamber, the areas of the positive electrode mixture layer 5, negative electrode 2, and separator 3 should be reduced, and the distance between the sealing material 6 and the inner wall should be reduced. Make it bigger or
Methods of lowering the temperature and pressure of thermal welding have been adopted, but there have been problems such as sacrificing the discharge capacity of the battery and lowering the reliability of the battery's sealing performance.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the problems of the prior art and to obtain a flat battery that prevents internal short circuits and has excellent sealing reliability and discharge capacity.

Structure of the Invention The present invention provides a power generating element in a battery chamber formed by interposing a thermoplastic resin sealing material processed into a window frame shape on the peripheral edges of a pair of opposing battery containers, and sealing the battery chamber by thermal welding. In a flat battery containing at least one of the battery containers, the peripheral surface in contact with the sealing material of at least one of the battery containers is flat, and a part thereof is formed with an annular protrusion protruding toward the sealing material. It is characterized in that the convex portion is embedded in a seal-like shape, and the sealing material and each peripheral edge surface of a pair of opposing battery containers are sealed by heat welding.

In the present invention, by doing as described above, the annular convex part embeds the sealing material, and the density of the sealing material resin at that part increases, and the degree of sealing improves. Even if the entire peripheral surface of the seal is weaker than that of a flat one, a sufficient degree of sealing can be obtained. Thereby, the extension into the interior of the battery chamber can be reduced, and a flat battery without expansion or internal short circuit can be constructed.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 and FIG. 4 show cross-sectional views of a battery constructed with each component of a flat battery according to the present invention.

The difference from FIGS. 1 and 2 is that a convex portion 1' extending toward the sealing material side is provided on the surface of the peripheral edge of the negative electrode container 1 that comes into contact with the sealing material 6. As shown in the sketch, two protrusions 1' are continuously provided in an annular shape around the periphery of the negative electrode container 1. In this case, the sealing material 6 changes from the state shown in FIG.
The sealing material 6 is transformed into the state shown in FIG. 4 by heat welding, and the state of the sealing material 6 from FIGS. 1 to 2 is such that it extends toward the outer periphery of the battery and into the battery chamber. The protrusion 1' blocks the flow of the sealant 6, and the annular protrusion embeds the sealant, increasing the density of the sealant resin at that location and improving the degree of sealing. Even though the compression is weaker than the conventional one where the entire peripheral surface is flat, a sufficient degree of sealing can be obtained, so the compression is slightly weakened,
The outer periphery of the battery and the extension into the battery chamber are extremely small, and the battery is sealed in a state where there is virtually no concern about deformation or destruction of internal elements of the battery, which would be a particular problem.

In the above example, a protrusion was formed on one of the battery containers before assembly, but as shown in Figure 2, after temporarily finishing it flat, the process of forming the protrusion by reheating was performed. In addition, it is also effective to form a convex portion.

The size of the convex portion on the peripheral surface of the battery container may be adjusted appropriately depending on the thermal deformation characteristics, width, thickness, etc. of the sealing member. Convex portions may be provided on both sides.

Although FIG. 4 shows an example in which two convex portions are formed in an annular shape, the effect can be obtained if there is one or more convex portions.
Furthermore, without necessarily insisting on continuous protrusions, for example, hemispherical protrusions may be continuously arranged at regular intervals on the peripheral surface of the battery container to form a substantially annular shape. This improves adhesive strength and prevents the sealant from extending into the battery compartment, and reduces the cross-sectional area of the resin toward the inside of the battery in the part of the sealant that corresponds to the convex part, which prevents water from entering from outside and from inside the battery. Evaporation of the electrolyte can be prevented.

Effects of the Invention As described above, according to the present invention, a flat battery with stable quality, which is free from internal short circuits, prevents moisture infiltration and dissipation at the sealing part, and improves storage characteristics as a battery, is provided. Can be configured.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the component structure of a conventional battery;
The figure is a longitudinal sectional view of a conventional battery, FIG. 3 is a sectional view of the component structure of a battery according to an embodiment of the present invention, FIG. 4 is a longitudinal sectional view of a battery according to an embodiment, and FIG. This is a sketch. 1... Negative electrode container, 1'... Convex portion, 2... Negative electrode,
3... Separator, 4... Positive electrode container, 5... Positive electrode mixture layer, 6... Seal material.

Claims (1)

[Claims] 1. A flat battery chamber in which a power generating element is housed in a battery chamber formed by interposing a window frame-shaped thermoplastic resin sealant on the peripheral edges of a pair of opposing battery containers and sealing them by heat welding. In a battery, at least one of the battery containers has a flat peripheral surface that is in contact with the sealing material, and a part thereof is formed with an annular protrusion protruding toward the sealing material, and the annular protrusion is pressed into contact with the sealing material by applying pressure and heating. A flat battery characterized in that the sealing material and each peripheral surface of a pair of opposing battery containers are sealed by thermal welding.