Nec Energy Devices, Ltd.

Envision Aesc Energy Devices Ltd.

Keiji Ide

Masanori Hirai

Akio Ukita

A secondary battery includes a battery electrode assembly in which positive electrodeand negative electrodeare stacked alternately with separatorinterposed therebetween. Positive electrodeand negative electrodeeach have current collectorand active material. Each surface of current collectorshas a coated portion and an uncoated portion of active materials. Active materialhas inclined portionshaving decreasing thickness. Insulatorsare arranged to cover boundariesbetween the coated portion and the uncoated portion of positive electrode. One or both of insulatorson both surfaces of positive electrode current collectorhave one endwhich is located on inclined surfaceand which is opposite to inclined portionof one or both of active materialson both surfaces of negative electrode current collector, and have other endwhich is located on uncoated portion of positive electrode

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Kanagawa, Japan

Keiji Ide