Panasonic Corporation

Sanyo Electric Co., Ltd.

Kenichi Honoki

Kensuke Nakura

Masato Fujikawa

Shin-Ichi Yuasa

Even after the battery reaches the last stage of the end of life, the use can be continued. A charging system includes battery pack and charger. During the charge of lithium-ion secondary battery, charge control unit calculates the full charge capacity maintaining rate, sets a first charge current value on the basis of the full charge capacity maintaining rate, and charges the battery. When lithium-ion secondary battery reaches the last stage of the end of life, charge control unit sets a second charge current value lower than the first charge current value set based on the full charge capacity maintaining rate, and charges the battery.

Secondary battery charging system and method, and battery pack

A positive electrode includes a positive electrode current collector, and a positive electrode active material layer formed on the surface of the positive electrode current collector. The positive electrode active material layer includes: a lithium-containing nickel oxide represented by the general formula (1): LiNiCoAlMO, where M is a transition metal (excluding Ni and Co) or the like, 0.8&#x2266;x&#x2266;1.4, and 0&#x3c;(p+q+r)&#x2266;0.7); and lithium carbonate. The positive electrode active material layer has a high concentration region of the lithium carbonate and a low concentration region of the lithium carbonate. The high concentration region covers 2 to 80% of the total thickness of the positive electrode active material layer, the range starting from the surface thereof. The low concentration region covers the range remaining on the positive electrode current collector side of the positive electrode active material layer.

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Osaka, Japan

Kenichi Honoki