Matsushita Electric Industrial Co., Ltd.

Yoshihiro Kashihara

Kunio Tsuruta

Katsuhiko Mori

Shuji Ito

Hizuru Koshina

Hajime Nishino

Kenjin Masumoto

Yasushi Hirakawa

Masaki Kitagawa

Toyoji Sugimoto

Kazuhiko Watanabe

Kazuo Saito

Kaoru Tsukamoto

Hisanori Sugimoto

Kojiro Ishikawa

Graphite powder for a negative electrode in prior arts, which allows lithium ions to repeat intercalation and deintercalation reversibly by charge and discharge, has failed to attain a specific capacity close to the theoretical capacity of 372 mAh per 1 g. Also, there was a problem in storage property at a high temperature when it is attempted to improve the high rate charge and discharge characteristics. An object of the present invention is to solve these problems. In the process of pulverizing flaky graphite particles of which plane interval (d002) of (002) plane is 3.350 to 3.360 angstroms, and crystallite size (Lc) in the C-axis direction is at least 1000 angstroms or more, the graphite particles are chamfered into disk- or tablet-like form, which are then sifted, so as to obtain a graphite powder, of which mean particle size is defined within the range of 10 to 30 microns, mean thickness of thinnest portion is defined to be 3 to 9 microns, and X-ray diffraction peak intensity ratio of (110)/(004) by a wide angle X-ray diffraction method is defined to be 0.015 or more. By using this powder, the conventional problems are solved in a favorable balance, and, while achieving high energy density, the high rate discharge performance and reliability when left at a high temperature can be enhanced.

Nonaqueous electrolyte secondary battery and method for manufacturing negative electrode of the same

An explosion-proof non-aqueous electrolyte battery is provided which has a current cutoff device for cutting off electrical connection within the battery with safety and certainty in the event of overcharge while remaining inoperable in normal use or in storage at an elevated temperature. A pair of an upper vent plate,and a lower vent plate,mechanically and electrically coupled with each other is provided on the sealing part of-the battery where the mechanical coupling of the pair of the upper vent plate,and the lower vent plate,is so configured as to rupture and cut off an electric current in the event the internal pressure of the battery case increases beyond a predetermined value, and the rupture pressure at which the mechanical coupling between the pair of upper vent plate,and the lower vent plate,is broken has been set to decrease as the spatial volume occupancy ratio of the battery increases.

Explosion-proof nonaqueous electrolyte secondary cell and rupture pressure setting method therefor

The present invention relates to an explosion-proof seal plate for a sealed cell and a production method thereof and aims at providing an explosion-proof seal plate and production method thereof, wherein problems of a risk of explosion of a cell due to an excessive pressure inside the cell caused by abnormal generation of a gas through a chemical reaction accompanying over charge or erroneous use of the cell or damaging of electronic equipment using the cell as the power source are solved, ignition and other accidents can be prevented with a high accuracy by reliably cutting off an electric current when the cell internal pressure increases, and the increase in the resistance due to permeation of an electrolyte can be limited. In order to accomplish this aim, the present invention provides a thin portion,having a breaking strength of 18-24 kg/cm,in the central portion of an upper metallic foil,made of aluminum and a thin portion,having a breaking strength of 10-13 kg/cm,in the central portion of a lower metallic foil,made of aluminum, wherein the diameter A of the thin portion,of the upper metallic foil and the diameter B of the thin portion,of the lower metallic foil,satisfy the relation AB. The two metallic foils are welded at the central portions with an insulating gasket interposed, and encased in a metallic case,made of aluminum having 4 vent holes, on top of which a temperature dependent resistor,and a metallic cap,having 4 vent holes are then placed. A seal plate is obtained by sealing the periphery of the metallic case,, with which it is possible to prevent accidents such as ignition and explosion of a cell by reliably allowing internal gas to exhaust in the event of generation of a large volume of gas under an abnormal condition of a sealed cell.

Explosion-proof seal plate for enclosed type cell and production method thereof

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Osaka, Japan

Yoshihiro Kashihara