POSITIVE ELECTRODE ACTIVE SUBSTANCE FOR SODIUM SECONDARY CELL, POSITIVE ELECTRODE FOR SODIUM SECONDARY CELL, AND SODIUM SECONDARY CELL

摘要

Provided is a positive electrode active substance for a sodium secondary cell, with which it is possible to obtain a sodium secondary cell having a high energy density. Also provided are a positive electrode for a sodium secondary cell and a sodium secondary cell. The positive electrode active substance for a sodium secondary cell comprises a compound metal oxide that has an α-NaFeO2-type crystal structure and is represented by formula (1). Naa(FewNixMny-zTiz)O2 (1) (Here, a is 0.6 to 1.0; w is greater than 0 but less than 0.5; x is greater than 0 but less than 0.5; y is greater than 0.03 but 0.5 or less; z is 0.03 or greater but less than 0.5; w + x + y = 1.0; and y>z.)