P3-type K0.45Mn0.8Cu0.2O2 Cathode Material for Sodium-Ion Batteries

P3-type K0.45Mn0.8Cu0.2O2 and K0.45MnO2 layered oxides were prepared and studied as cathode materials for sodium-ion batteries. The impact of Cu substitution for Mn and the electrochemical performance of both samples were comprehensively investigated. Of particular interest is the P3-type K0.45Mn0.8Cu0.2O2, which exhibited enhanced diffusion capability and improved structural stability, resulting in an impressive reversible capacity of 109 mAh g-1 at 20 mA g-1 within the voltage range of 1.5-4.0 V (Na+/Na), superior rate capability of 74 mAh g-1 at 500 mA g-1, and excellent cycling performance with 86% capacity retention after 150 cycles at 20 mA g-1. The substitution of Cu for Mn effectively mitigates Na+/vacancy ordering and complex phase transition observed in P3-K0.45MnO2. Post-cycling phase characterization indicates the presence of excess K ions in the layers, contributing to the stabilization of the layered structure. This previously unreported class of P3 cathode material introduces new perspectives for the advancement of layered cathode materials for high-performance and cost-effective sodium-ion batteries.