| abstract |
Provided is a lithium ion secondary battery having a large energy density and an improved capacity retention rate after repeated use even under high voltage application (cycle characteristics), and excellent in safety. A lithium ion secondary battery containing a negative electrode for reversibly intercalating and deintercalating lithium ions, a positive electrode containing lithium vanadium phosphate, and a non-aqueous electrolytic solution containing lithium fluoroethyl phosphate as an electrolyte can be obtained. |