LITHIUM ION SECONDARY BATTERY, NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, NEGATIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY, ELECTRIC MOTOR-DRIVEN TOOL, ELECTRIC VEHICLE AND ELECTRIC POWER STORAGE SYSTEM

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 a plurality of negative electrode active material particles. The negative electrode active material particles each include a core part, and a coating part coating at least part of the surface of the core part. The core part includes a silicon-based material (SiO, where 0≤x0.5), and the coating part includes an amorphous or low-crystallinity silicon-based material (SiO, where 0.5≤y≤1.8).SELECTED DRAWING: Figure 8