Boosting Reversibility of Co-Doped P2-Type Na_0.67MnO₂ Multiple-Layer Oriented Stacking Nanosheets for Sodium-Ion Batteries

Layered P2-type Na0.67MnO2, a crucial category of cathode material for sodium-ion batteries (SIBs), faces numerous challenges, including its poor structural stability and Mn3+ dissolution, which result in an inadequate performance. Herein, the modified Na0.67MnO2 with Co doping was synthesized by the coprecipitation method, which has a hierarchical flake structure consisting of multiple-layer oriented stacking nanosheets. A systematic investigation was conducted to examine the influence of Co doping on the crystal structure and electrochemical performance of Na0.67MnO2. The optimal Na0.67Mn0.99Co0.01O2 cathode exhibits an initial discharge specific capacity of 154.3 mA h g–1 at 0.1C within a potential window of 2.0–4.0 V. The Na0.67Mn0.99Co0.01O2 cathode exhibits a high capacity retention of 90.3% at 1C after 100 cycles and maintains a capacity of 61.2 mA h g–1 even after 500 cycles at 5C. The superior electrochemical performance is derived from reasonable geometrical structure and chemical substitution, which can enhance the interfacial area with the electrolyte and decrease the diffusion energy barrier of sodium ions. This study may provide guidance for designing and constructing stable P2-type Na0.67MnO2 as a high-performance candidate for SIBs.