Construction of Cu-Zn Co-doped layered materials for sodium-ion batteries with high cycle stability

Due to its high operational voltage and energy density, P2-type Na0.67Ni0.3Mn0.7O2 has become a leading cathode material for Sodium-ion batteries (SIBs), making it an ideal option for large-scale energy storage. However, the practical application of P2-type Na0.67Ni0.3Mn0.7O2 is limited due to the capacity constraints and unwanted phase transitions, presenting significant challenges to the widespread adoption of SIBs. To address these challenges and optimize the electrochemical properties of the P2 phase cathode material, this study proposes the Cu and Zn co-doped strategy, which involves the insertion of Cu/Zn into the transition metal (TM) layer to improve electrochemical performance. Furthermore, the incorporation of Cu/Zn can stabilize the P2-phase structure against P2-O2 phase transitions, further enhancing its electrochemical properties. The obtained P2-type Na0.67[Ni0.3Mn0.58Cu0.09Zn0.03]O2 cathode material shows impressive cycling stability, maintaining 80% capacity retention after 1000 cycles at 2 C. The Cyclic Voltammetry (CV) tests show that the Cu2+/Cu3+ redox reaction is also involved in charge compensation during the charge/discharge process. Cu/Zn co-doping suppresses P2-O2 phase transitions as shown by ex-situ X-ray diffraction analysis. Based on previous characterization, Cu/Zn co-doping can be used to effectively modify the structure of layered oxides, leading to enhanced practical applications