JP2545183Y2 - Flat lithium battery - Google Patents

Description

[Detailed description of the invention] << Industrial application field >> This invention relates to a flat lithium battery having a structure in which a positive electrode mixture is hardly peeled off from a current collecting net during an assembling process.

<< Conventional Technology >> For example, in a flat lithium battery, as a structure to improve the electrical contact between the positive electrode mixture and the positive electrode can, a current collecting net made of stainless steel net etc. is spotted at the center of the inner bottom surface of the positive electrode can. The positive electrode mixture is welded and pressure-bonded to the upper part of the current collecting net.

According to this structure, the bottom surface of the positive electrode mixture is encroached between the current collecting nets, so that greater electrical contact can be obtained.

《Problems to be solved by the invention》 However, in this structure, the positive electrode mixture is assembled inside the positive electrode can, the non-aqueous electrolyte is injected, and the external When the positive electrode mixture is peeled or cracked from the current collecting net, the electrical contact is reduced, and the yield and the performance are varied.

As a cause of this, as shown in FIGS. 3A to 3C, the spot welding portion a of the current collecting net 1 is
Two or more points ((A), (B) in the figure),
Alternatively, the current collecting net 1 is joined to the positive electrode can 2 in a completely fixed state because it is formed in an annular shape (FIG. 2C).

However, in this structure, the external force applied to the positive electrode can 2 is directly transmitted to the positive electrode mixture via the current collecting net 1 without being attenuated. In particular, the positive electrode mixture itself has a fragile property, and the non-aqueous electrolyte is Since it is impregnated, it tends to collapse, and cracks and peeling occur at the pressure-bonded portion with the current collecting net 1.

This invention solves the above-mentioned problem. Contrary to the conventional technology, the current collector net has a degree of freedom of movement, thereby giving an effect of damping external vibration, and forming a positive electrode mixture due to external vibration and impact. It is an object of the present invention to provide a flat lithium battery capable of preventing peeling and cracking.

<< Means for Solving the Problems >> In order to achieve the above object, the present invention provides a spot welding portion for the current collector net at two locations close to the periphery of the current collector net. Can swing or vibrate around the spot welding point.

<< Operation >> According to the above configuration, the current collecting net is joined to the positive electrode can with some degree of freedom of movement,
When an external force such as vibration or impact is applied to the positive electrode can, the positive electrode can is attenuated by the current collecting net.

<< Embodiment >> Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a coin-type lithium battery according to the present invention.

In the drawing, reference numeral 10 denotes a current collecting net spot-welded at the center of the inner bottom surface of the positive electrode can 12, and 14 denotes a positive electrode mixture crimped on the current collecting net 10, and after drying the positive electrode mixture, A separator 16 is laminated on the mixture 14, and a non-aqueous electrolyte is injected.

At the same time, in a separate step, a negative electrode terminal plate 22 having a lithium negative electrode 18 provided on the inner surface and a sealing gasket 20 fitted around the periphery is prepared.

Then, the negative electrode terminal plate 22 and the positive electrode can 12 are conveyed in the form of an assembly line, and in the final stage, the negative electrode terminal plate 22 is fitted to the positive electrode can 12, and the periphery of the positive electrode can 12 is sealed with a gasket.
By caulking toward 20, a coin-shaped battery in which the inside is sealed and a lithium negative electrode 18 and a positive electrode mixture 14 are vertically stacked with a separator 16 interposed therebetween is completed.

The current collecting net 10 used in the above assembly is, for example,
In the CR2450 battery, a net made by knitting a stainless steel wire of 0.08 mm in diameter to 60 mesh is punched out to form a disk having a diameter of 14.5 mm as shown in FIG. 2 (A), or as shown in FIG. As shown, it was formed into a square with a side of 10.2 mm.

In the case where the current collecting net 10 is disk-shaped, spot welding 24 having a diameter of 1 mm has been performed at two places close to the peripheral position (range surrounded by oblique lines) of 2 / 3r or more from the center O,
The current collecting net 10 is joined to the inner bottom surface of the positive electrode can 12 at the spot welding portion 24 to maintain the electrical connection state.

If the current collecting net 10 is rectangular, this area is divided into nine equal parts, and spot welding 24 with a diameter of 1 mm is performed at one of the corners (the part enclosed by oblique lines) approaching one of the corners. The current collecting net 10 is joined to the inner bottom surface of the positive electrode can 12 at the spot welding portion 24 to maintain the electrical connection state.

Therefore, regardless of the shape of the current collecting net 10, if external force such as vibration or impact in the rotational direction or the vertical direction of the positive electrode can 12 is applied, the current collecting net 10 Oscillation (rotation direction) or vibration (vertical direction) at the base point, the external force is attenuated by the freedom of this movement, and as a result, the positive electrode mixture crimped on the upper surface of the current collecting net 10
It prevents 14 cracks and peels.

A comparison was made between the CR2450 type battery when the conventional current collector net was fixedly spot-welded and the defective number due to peeling of the mixture in the assembly line in the spot welding structure of the current collector net according to the present invention. According to the present invention, the number of defective products was reduced to 50 per 1000 pieces, whereas the number of defective products was reduced to 0 pieces per 1,000 pieces.

<< Effects of the Invention >> As described in detail in the above embodiments, in the flat lithium battery according to the invention, when an external force such as vibration or impact is applied to the positive electrode can, the current collecting net is formed around the peripheral portion of the positive electrode can. Since the structure is capable of swinging or vibrating from two spot welding points, peeling and cracking of the positive electrode mixture during line transfer can be prevented, and the yield is improved.

In addition, there is no deterioration in performance due to invisible cracks and the like, and variations in performance are small.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an assembled state of a coin-type lithium battery according to the present invention. FIGS. 2A and 2B are plan views showing spot welding states of a current collecting net to a positive electrode can according to the present invention. FIGS. 3A to 3C are plan views showing a conventional spot welding state of a current collecting net to a positive electrode can. 10… Current collector net 12… Positive electrode can 14… Positive electrode mixture 16 …… Separator 18… Lithium negative electrode 22 …… Terminal plate 24 …… Spot welding

Claims (1)

(57) [Scope of request for utility model registration] 1. A current collector net spot-welded to the center of the inner bottom surface of a positive electrode can, a positive electrode mixture crimped on the current collector net, and a lithium negative electrode laminated on the positive electrode mixture with a separator interposed therebetween. And a non-aqueous electrolyte, and a flat lithium battery including a terminal plate that seals the positive electrode can, wherein two spots near the peripheral edge of the current collecting net are spot-welded to the current collecting net, Thus, the current collector net can swing or vibrate around the spot welding point as a base point.