LITHIUM ION SECONDARY BATTERY, LITHIUM ION SECONDARY BATTERY NEGATIVE ELECTRODE, BATTERY PACK, ELECTRIC VEHICLE, ELECTRICITY STORAGE SYSTEM, POWER TOOL, AND ELECTRONIC APPARATUS

摘要

A lithium ion secondary battery is provided with a positive electrode, a negative electrode containing an active material, and an electrolytic solution, wherein the active material includes a core portion capable of occluding and releasing lithium ions, an amorphous or low-crystalline coating portion disposed on at least a part of the surface of the core portion, and a fibrous carbon portion disposed on at least a part of the surface of the coating portion, and the coating portion contains Si and O as constituent elements, while the atomic ratio y (O/Si) of O relative to Si satisfies 0.5≦̸y≦̸1.8.