NONAQUEOUS ELECTROLYTE SOLUTION TYPE LITHIUM ION SECONDARY BATTERY

摘要

Disclosed is a lithium ion secondary battery which uses a two-phase compound as a positive electrode active material and has excellent durability. The lithium ion secondary battery comprises: an electrode body that has a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material; and a nonaqueous electrolyte solution that contains a lithium salt in an organic solvent. The positive electrode active material is mainly composed of a lithium-containing two-phase compound and additionally contains particles that are formed from a lithium transition metal oxide having a lamellar structure. The particles of the lamellar oxide have an average particle diameter of 2 µm or less and are contained in the positive electrode active material in an amount of 5% by mass or less.