Improving the structural and cyclic stabilities of P2-type Na0.67MnO2 cathode material via Cu and Ti co-substitution for sodium ion batteries

An air-stable Na_0.67Mn_0.7Cu_0.15Ti_0.15O₂ (NMCT) has been synthesized using a solid-state method. It displays a reversible capacity of 170 mA h g^-1 and a capacity retention of 82.5% after 300 cycles. NMCT also exhibits good structural stability upon electrochemical de/intercalation processes as observed by operando XRD. And the result shows that the unit-cell volume change of NMCT during the whole process of Na⁺ de/intercalation is only 3.2%. These data indicate that NMCT is a promising cathode material for sodium ion batteries (SIBs).