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

Abstract

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), which is an ideal option for large-scale energy storage. However, the practical application of P2-type Na0.67Ni0.3Mn0.7O2 is limited by the capacity constraints and unwanted phase transitions, presenting significant challenges to the widespread application of SIBs. To address these challenges and optimize the electrochemical properties of the P2 phase cathode material, this study proposes a Cu and Zn co-doped strategy to improve the electrochemical performance. The incorporation of Cu/Zn can stabilize the P2-phase structure against P2-O2 phase transitions, thus enhancing its electrochemical properties. The as-obtained P2-type Na0.67[Ni0.3Mn0.58Cu0.09Zn0.03]O2 cathode material shows an 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.