| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which enables the enhancement of cycle characteristics and initial charge and discharge characteristics.SOLUTION: A lithium ion secondary battery comprises: a positive electrode 21; a negative electrode 22; an electrolytic solution; and a separator 23 provided between the positive electrode 21 and the negative electrode 22, and impregnated with the electrolytic solution. The negative electrode 22 has a negative electrode active material layer 22B including negative electrode active material particles. The negative electrode active material particles each include a core part and a covering portion partially covering the surface of the core part. The core part contains a silicon-based material (SiO, where 0≤x<0.5), whereas the covering portion contains non-crystalline or low-crystallinity silicon-based material (SiO, where 0.5≤y≤1.8). |
