LITHIUM ION SECONDARY BATTERY

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery suppressing drop in capacity and lengthening the life. SOLUTION: The lithium ion secondary battery 20 has a battery can 9. An electrode group 7 formed by winding a positive electrode plate 4 and a negative electrode plate 5 through a separator 6 is housed in the battery can 9. A PTFE shaft core 1 is used in the winding center of the electrode group 7. A nonaqueous electrolyte is poured in the battery can 9 and the electrode group 7 is impregnated with the nonaqueous electrolyte. The nonaqueous electrolyte is prepared by dissolving lithium hexafluorophosphate, which is a lithium salt, in an organic solvent. A water absorbent and an acid neutralizer are contained in the shaft core 1 and a thin film 3 wound on the outer peripheral part of the electrode group 7. A minute amount of moisture is adsorbed and removed by the water absorbent, and hydrofluoric acid produced by decomposition of the lithium salt is neutralized by the acid neutralizer. COPYRIGHT: (C)2010,JPO&INPIT