Negative electrode active material for sodium ion secondary battery, and negative electrode for sodium ion secondary battery and sodium ion secondary battery using the same

摘要

PROBLEM TO BE SOLVED: To provide: a negative electrode active material for a sodium ion secondary battery high in discharge capacity and excellent in cycle characteristics; a negative electrode for a sodium ion secondary battery; and a sodium ion secondary battery.SOLUTION: A negative electrode active material for a sodium ion secondary battery of the present invention contains Sn, O and at least one selected from among Si, B and P, and also includes an amorphous phase.