Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Ryoichi Tanaka

Masaya Okochi

Yutaka Kawatate

Kaoru Inoue

Masatoshi Nagayama

Shoichiro Watanabe

Hideya Asano

Yosuke Kita

Hideyasu Takatsuji

A positive electrode active material for a lithium ion secondary battery is a lithium-containing composite oxide represented by the chemical formula: Li(CoMgAl)MO, where M is at least one element selected from the group consisting of Na and K, and the values a, b, c, x, y and z respectively satisfy 0&#x2266;a&#x2266;1.05, 0.005&#x2266;x&#x2266;0.15, 0.0001&#x2266;y&#x2266;0.01, 0.0002&#x2266;z&#x2266;0.008, 0.85&#x2266;b&#x2266;1.1 and 1.8&#x2266;c&#x2266;2.1. This makes it possible to improve a high temperature storage characteristics and safety of the lithium ion secondary battery.

Lithium ion secondary battery

A lithium ion secondary battery comprising: a positive electrode; a negative electrode; and a non-aqueous electrolyte, the positive electrode comprising a positive electrode active material and a binder, the positive electrode active material comprising a lithium-containing composite oxide represented by the chemical formula:Li(CoMgM)Owhere M is at least one selected from Ni, Mn and Al, 0&#x2266;a&#x2266;1.05, 0.005&#x2266;x&#x2266;0.025, 0&#x2266;y&#x2266;0.25, 0.85&#x2266;b&#x2266;1.1, and 1.8&#x2266;c&#x2266;2.1.

Lithium ion secondary cell

A lithium ion secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the positive electrode comprises a positive electrode active material, a conductive agent and a binder, the positive electrode active material comprises a lithium-containing composite oxide represented by the formula Li(CoMgM)O, where M is at least one selected from Ni and Al, 0&#x2266;a&#x2266;1.05, 0.03&#x2266;x&#x2266;0.15, 0&#x2266;y&#x2266;0.25, 0.85&#x2266;b&#x2266;1.1 and 1.8&#x2266;c&#x2266;2.1, and the amount of the conductive agent contained in the positive electrode is not more than 3.0 parts by weight per 100 parts by weight of the positive electrode active material.

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Izumiotsu, Japan

Ryoichi Tanaka