SEALED SECONDARY BATTERY

摘要

The main purpose of the present invention is to improve the safety of a sealed secondary battery. The present invention relates to a sealed secondary battery which is provided with: a battery case which has a bottomed cylindrical shape, and an opening; a sealing body for sealing the opening of the battery case; and a wound electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator therebetween. An annular thinned portion is formed in the bottom of the battery case. The surface area of a region surrounded by the annular thinned portion is at least 10% of the surface area of the bottom of the battery case. The volume energy density of the sealed secondary battery is at least 500Wh/L.