COMPOSITE METAL OXIDE AND SODIUM RECHARGEABLE BATTERY

摘要

Disclosed is a sodium rechargeable battery that can reduce the amount of rare metal elements, such as lithium and cobalt, used and has a larger discharge capacity after the repetition of charge and discharge than the conventional sodium rechargeable battery. Also disclosed is a composite metal oxide usable as a positive electrode active material for the sodium rechargeable battery. The composite metal oxide comprises Na, Mn, and M1 wherein M1 represents Fe or Ni. The Na : Mn : M1 molar ratio is a : (1 - b) : b wherein a is a value in the range of more than 0.5 and less than 1; and b is a value in the range of not less than 0.001 and not more than 0.5. The composite metal oxide is represented by formula (1): NaaMn1-bM1 bO2 wherein M1, a, and b are defined above. Further disclosed is a positive electrode active material for a sodium rechargeable battery, comprising the composite metal oxide.