Nec Energy Devices, Ltd.

Yoshimasa Yamamoto

Hiroo Takahashi

Masanori Hirai

Masaaki Matsuu

Kouzou Takeda

Provided is a secondary battery with a high electric characteristic and reliability that prevents the short circuit between a positive electrode and a negative electrode by an insulating member and that prevents or reduces the volume increase and deformation of a battery electrode assembly. A secondary battery includes a battery electrode assembly in which positive electrodeand negative electrodeare alternately laminated while separatoris interposed therebetween. Positive electrodeand negative electrodeinclude current collectorsand active materials, each surface of current collectorsis provided with an application portion and a non-application portion of active materials, and the active materialsinclude a thin portion whose thickness is small. A charging capacity ratio A/C between negative electrodeand positive electrodethat face each other at an outer edge portion containing the thin portion is greater than the charging capacity ratio A/C between negative electrodeand positive electrodethat face each other at a center side with respect to the outer edge portion.

Secondary battery

Provided is a battery in which collector foil is unlikely to break. In a lithium-ion secondary battery, as for a distance from a connection section between a positive electrode tab and the positive electrode terminal to a boundary section between applying and non-applying sections of positive-electrode active material in a direction perpendicular to a stacking direction, compared with a reference positive electrode having the boundary section that is located farthest to the connection section by straight-line distance, a layer of a positive electrode that is stacked in such a way as to be farthest from the reference positive electrode has a smaller distance from a boundary of the applying and non-applying sections of the positive-electrode active material to a connection section with the positive electrode tab in a direction perpendicular to a stacking direction.

Growing community of inventors

Sagamihara, Japan

Yoshimasa Yamamoto