LITHIUM ION SECONDARY CELL

摘要

Provided is a lithium ion secondary battery capable of realizing a high energy density while maintaining output. A lithium ion secondary battery D1 according to the present invention includes an electrode having an active material mix layer 31 on both surfaces of a current collector 35. The active material mix layer 31 has a smaller void ratio in a current collector side region 34 of the active material mix layer 31 and a surface side region 32 of the active material mix layer 31 than in an intermediate region 33 between the current collector side region 34 and the surface side region 32 of the active material mix layer 31.