Negative electrode active material for sodium secondary battery using molten salt electrolyte, negative electrode and sodium secondary battery using molten salt electrolyte

摘要

It is an object of the present invention to provide a high capacity density negative electrode active material and the like that can improve the cycle characteristics of a sodium secondary battery using a molten salt electrolyte. A negative electrode active material for a sodium secondary battery using a molten salt electrolyte, wherein the negative electrode active material is tricobalt tetroxide. The negative electrode active material preferably has an average particle diameter d50 of the tricobalt tetroxide of 10 μm or less and a maximum particle diameter dmax of 30 μm or less.