Matsushita Electric Industrial Co., Ltd.

Other

Toyoji Sugimoto

Hizuru Koshina

Masaki Kitagawa

Kaoru Inoue

Shusaku Goto

Shoji Yamaguchi

Manabu Hayashi

Yui Takahashi

Shuji Ito

Hajime Nishino

Kunio Tsuruta

Yoshihiro Kashihara

Kaoru Tsukamoto

Hisanori Sugimoto

Kojiro Ishikawa

Enhancement of the storage property at a high temperature and discharge characteristics at a low temperature of a nonaqueous electrolyte secondary cell is intended. A negative electrode material which is prepared by covering the surface of a nucleus made of a graphite powder with a carbonaceous matter, the graphite powder having a specified plane interval, spectrum value, mean particle size, specific surface area, tapping density, and (110)/(004) X-ray peak intensity ratio, is used in the nonaqueous electrolyte secondary cell.

Nonaqueous electrolyte secondary cell with a plural-layer carbonaceous negative electrode

A binder made of a mixture of a first binder component including styrene butadiene copolymer containing styrene at between 20% and 70%, and a second binder component selected from at least one of styrene butadiene copolymer containing styrene at between 80% and 100% and polystyrene is used for the negative electrode of rechargeable batteries comprising a carbon material and the binder. The use of the negative electrode comprising the carbon material and binder results in good resistance to peeling of a coated film, and thus ease of handling of a negative electrode sheet. Consequently, rechargeable batteries with good low-temperature discharge characteristics are supplied at good yield.

Negative electrode for secondary cell, negative plate for secondary cell, and secondary cell comprising the same

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

Graphite material capable of absorbing and desorbing lithium is employed as the negative electrode material of a non-aqueous electrolyte secondary battery, the negative electrode material being bound by at least one type of material selected from the group consisting of polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-vinyl acetate copolymer, and polypropylene. A non-aqueous electrolyte secondary battery with a high anti-peeling strength of the electrode mix, superiority in the ease of handling, a high reliability in mass production, a superior low-temperature discharge characteristic and cycle characteristic is provided by employing the negative electrode in combination with a rechargeable positive electrode and a non-aqueous liquid electrolyte.

Non-aqueous electrolyte secondary cell, negative electrode therefor, and method of producing negative electrode

Nonaqueous electrolyte secondary battery comprising carbon particles with a plural-layer structure

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Fujiidera, Japan

Toyoji Sugimoto