Li Deintercalation‐Intercalation Reaction and Structural Change in Lithium Transition Metal Nitride, Li7MnN4

which has cubic symmetry, P43n, is prepared by heating a mixture of and in a gas stream. The Li ion is easily deintercalated in a cell forming over a wide range of . The specific capacity of the cell is about 210 mAhg −1 . With an increase in , a new phase which also has cubic symmetry but has a smaller lattice parameter appears. The original phase decreases with an increase in , and disappears at . A two‐phase reaction then occurs. In the range of , the lattice parameter of the second phase decreases with an increase in . The cell shows a good reversibility under high current density (1200 μA/cm 2 ). is thus suggested to be a good candidate for an electrode for a lithium secondary battery.