NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which is arranged to keep a battery performance by combination with a particular separator and is improved in flame retardance by use of an electrolytic solution containing a particular flame-resistant agent.SOLUTION: A nonaqueous electrolyte secondary battery comprises a positive electrode, a negative electrode, a separator for separating the positive and negative electrodes, and an electrolytic solution arranged in the battery to come into contact with the positive and negative electrodes through the separator. The electrolytic solution contains an electrolytic substance and a phosphazene compound in an aprotic solvent. The separator is composed of a complex which includes a base material including a non-heat resistant resin, and a heat-resistant material covering the base material.