JPS59215659A - Flat type lithic battery - Google Patents

Abstract

PURPOSE:To make a battery have such excellent characteristics as being low in internal resistance and less in its unevenness, by grinding a surface being opposed to a positive pole of carbon fluoride of a dished metal case, and applying a carbon film to the surface before drying. CONSTITUTION:A positive pole 3 composed of carbon fluoride, as a main component, housed in a dished metal case 1 having a rising part 2 in and around and a metallic lithic negative pole 6 being forcibly pressed to the inner surface of a dished metal sealing lid 4 having a sleeve 5 in and around are opposed with each other via a separator 7, while an upper end of the rising part 2 in and around the metal case 1 is bent to the side of the sealing lid 4 and sealed up via a gasket 8. A surface 10 to be contacted with a positive pole black flux 3 at the inner surface of the metal case 1 in a suchlike battery is ground by a grinder, sandpaper, etc., and a carbon film 11 is applied to this ground surface 12 before drying.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to flat lithium batteries, and particularly to improvements in the positive electrode current collector.

Conventional Structure and Its Problems A typical structure of a flat lithium battery is shown in FIG. In the figure, reference numeral 1 denotes a dish-shaped metal case made of stainless steel or the like having a rising portion 2 on the periphery, and houses a positive electrode mixture 3 containing carbon hepta-noide as a main component.

Reference numeral 4 denotes a dish-shaped sealing lid made of stainless steel or the like and having a sleeve 5 around the periphery, and metal lithium 6, which is a negative electrode active material, is pressed into contact with the inner surface. 7 is a separator impregnated with a non-aqueous electrolyte. 08 is a gasket made of polypropylene or the like, and the upper end 9 of the rising part of the case is bent inward to seal it. Reference numeral 10 denotes the inner surface of the metal case, and a carbon film 11 is usually applied to the surface in contact with the positive electrode mixture 3 and dried. carbon film 11
0 The purpose is to improve the electrical contact between the metal case 1 and the positive electrode mixture 3, but there is a thin strong oxide film on the surface of the metal case 1, and the electrical contact between this oxide film and the carbon film is The disadvantage is that the contact is not always sufficient and therefore the internal resistance of the battery is relatively high.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the drawback that the internal resistance of the battery in the conventional example is high.

Structure of the Invention In order to achieve the above object, the present invention is characterized in that the surface of the inner surface of the metal case in contact with the positive electrode mixture is polished with a grinder, sand vapor, etc., and a carbon film is applied and dried on this polished surface. It is.

At this time, even if a part of the inner surface of the case, that is, a part in contact with the positive electrode mixture 3, is polished 12 with a grinder, sandpaper, etc. as shown in Fig. 2 to remove the oxide film, the oxide film may be reoxidized over time. Since a film is formed, it goes without saying that the shorter the time required to form a carbon film after polishing, the better; however, according to experimental results, polishing can be carried out virtually immediately if the polishing is done for up to 6 hours. There is no discernible difference. In the conventional example, the carbon film was directly applied and dried on the inner surface of the case 10, but if the process is continuous, such as polishing immediately before applying the carbon film and applying the carbon film in the next step, an oxide film will be formed. This is effective because there is almost no time left to do so.

DESCRIPTION OF EXAMPLES In order to confirm the effects of the present invention, a fluorocarbon lithium battery having a diameter of 20 cm and a height of 1.6 nm was manufactured as a prototype with the configuration shown in FIG. The surface of the current collecting carbon film coated inside the metal case used had a diameter of 10 mm.

The inner surface of the case was polished to a depth of approximately 20 μm using a GRIT NO240 sand vapor. It took 3 minutes to apply the carbon film (e) after polishing.

The results were as follows.

Trial production quantity 10 pieces 10 pieces Average internal resistance value 20.6Ω 14-3Ω〃
Maximum value: 27 Ω 16 Ω Minimum value: 16 Ω 12.6 Ω Compared to conventional products, the product of the present invention has a smaller average internal resistance value or extremely small fluctuation width.

Effects of the Invention As is clear from the examples described above, the battery of the present invention has extremely good characteristics such as low internal resistance and small variation thereof.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a typical structure of a flat lithium battery, and FIG. 2 is a sectional view showing the structure of a flat lithium battery in an embodiment of the present invention. 1...Dish-shaped metal case, 3...Positive electrode mixture, 4...-Sealing lid, 6...Negative electrode, 10
...Inner surface of the case, 11...Carbon film, 1
2... Polishing section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] A positive electrode mainly made of fluorocarbon, which is housed in a dish-shaped metal case with a raised portion on the periphery, and a metal lithium negative electrode, which is pressed into contact with the inner surface of a dish-shaped metal sealing lid with a sleeve on the periphery, are opposed to each other via a separator. At the same time, the battery was sealed by bending the upper end of the peripheral rising part of the metal case toward the sealing lid side via a gasket, and the portion of the dish-shaped metal case facing the fluorocarbon positive electrode was polished, a carbon film was applied, and it was dried. A flat lithium battery characterized by: