SODIUM SECONDARY BATTERY, CHARGE/DISCHARGE SYSTEM FOR SODIUM SECONDARY BATTERY, AND METHOD FOR CHARGING/DISCHARGING SODIUM SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a sodium secondary battery with high capacity, while using a sodium-containing vanadium phosphate compound as a positive electrode active material, and a method for charging/discharging the same.SOLUTION: A sodium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte having sodium ion conductivity. The electrolyte contains 20 mass% or more of an ionic liquid, the ionic liquid contains anions and cations, the cations contain sodium ions, and the positive electrode includes a positive electrode active material containing a sodium-containing vanadium phosphate compound.SELECTED DRAWING: Figure 1