SODIUM ION SECONDARY BATTERY

摘要

A sodium ion secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator provided between the positive electrode and the negative electrode, and an electrolyte, the positive electrode active material containing a sodium-containing transition metal oxide that reversibly intercalates and deintercalates sodium ions, in the sodium-containing transition metal oxide in a fully charged state, the ratio of sodium atoms to transition metal atoms, i.e., Na/MT, satisfying Na/MT≦0.3, and the ratio of the total Cnt of the reversible capacity and the irreversible capacity of the negative electrode to the total Cpt of the reversible capacity and the irreversible capacity of the positive electrode, i.e., Cnt/Cpt, satisfying 1≦Cnt/Cpt.

主权项

1. A sodium ion secondary battery comprising:
a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator provided between the positive electrode and the negative electrode, and an electrolyte, the electrolyte being a nonaqueous electrolyte containing sodium ions, the positive electrode active material containing a sodium-containing transition metal oxide that reversibly intercalates and deintercalates sodium ions, the negative electrode active material containing at least one selected from the group consisting of a first material that reversibly intercalates and deintercalates sodium ions and a second material that is alloyed with sodium, in the sodium-containing transition metal oxide in a fully charged state, the ratio of sodium atoms to transition metal atoms, i.e., Na/MT, satisfying Na/MT≦0.3, and the ratio of the total Cnt of the reversible capacity and the irreversible capacity of the negative electrode to the total Cpt of the reversible capacity and the irreversible capacity of the positive electrode, i.e., Cnt/Cpt, satisfying 1≦Cnt/Cpt.