Murata Manufacturing Co., Ltd.

Taichi Katsumoto

Yoshiichi Horikoshi

Moriaki Okuno

Rie Watanabe

Masayuki Kageyama

Kazuki Honda

Takashi Sato

Takaaki Matsui

Shinji Hatake

Yuta Hirano

Taichi Kogure

Naoko Yamakawa

Keitaro Kitada

Futoshi Sato

Takuma Kawahara

Shinji Hayazaki

Secondary battery

A flat secondary battery includes an outer package member, a battery device, and an electrode terminal. The outer package member has a flat and columnar shape, and includes a pair of bottom parts and a sidewall part. The bottom parts are opposed to each other. The sidewall part lies between the bottom parts. At least a portion of a surface of the sidewall part is a curved surface. The battery device is contained inside the outer package member and includes a positive electrode and a negative electrode. The electrode terminal is provided to be exposed at the sidewall part and is coupled to one of the positive electrode and the negative electrode.

Flat secondary battery

A secondary battery includes a power generation element including a plurality of electrodes. The electrodes are stacked on each other in a stacking direction with a separator interposed therebetween. Each of the electrodes includes a current collector led out in a first direction intersecting the stacking direction. Each of a plurality of current collectors led out in the first direction includes an end part, and the end part includes a first bent part that is bent in a second direction intersecting the first direction. Each of a plurality of first bent parts overlaps and is in contact with an adjacent first bent part in the second direction. At least one of the first bent parts terminates at a middle point on an end face along the second direction of the power generation element.

A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer including a lithium-cobalt composite oxide. The lithium-cobalt composite oxide has a layered rock-salt crystal structure. The negative electrode includes a negative electrode active material layer including graphite. When the secondary battery is charged and discharged with an upper limit of a closed circuit voltage being set to 4.42 V or higher, a unit capacity (mAh/g) satisfies a condition represented by 168 mAh/g≤unit capacity (mAh/g)≤(−0.28×area rate (%)+178) mAh/g.

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Kyoto, Japan

Taichi Katsumoto