Co3O4-modified P2–Na2/3Mn0.75Co0.25O2 cathode for Na-ion batteries with high capacity and excellent cyclability

Abstract Co3O4 modification is introduced to improve the Na-storage characteristic of P2–Na2/3Mn0.75Co0.25O2 through a solid-state reaction. The synergistic effects of Co3O4 modification and Co ions doping have significantly promoted sodium storage characteristics, in particular, cyclability at high-rate of the pristine oxide. The pseudo-capacitance effects of Co3O4 modified layer can also offer electrochemical contributions to the pristine oxide. 2 wt% Co3O4 modified cathode achieves 164.1 mAh g−1 at 0.1 C with the capacity retention of 85.6% at 100th cycle, 111.4 mAh g−1 at 1 C with the retention of 72.3% at 400th cycle, 85.7 mAh g−1 at 5 C with the retention rate of 73.5% at 1000th cycle, and 68.6 mAh g−1 at 10 C with 82.0% capacity retention after 1000 cycles. Especially, 2 wt% Co3O4 modified cathode can reach up to the capacity retention of 90.1% at 1 C at 120 cycles, 90.4% at 5 C after 350 cycles and 90.7% at 10 C over 640 cycles. The high-rate cycling performance of the modified cathode is also involved in its high reversible P2–P3 transition during Na+ insertion/extraction. Therefore, the excellent Co3O4 modified cathode will provide impetus for future developments and applications of sodium-ion batteries.