Zn/Ti/F synergetic-doped Na0.67Ni0.33Mn0.67O2 for sodium-ion batteries with high energy density

Abstract

P2–Na_0.67Ni_0.33Mn_0.67O₂ is a promising cathode for sodium-ion batteries due to its high theoretical capacity, but it elicits a harmful phase transformation and severe fading of capacity above 4.2 V. Here, we report creation of a Zn/Ti/F synergetic-doped Na_0.67Ni_0.33Mn_0.67O₂ cathode material using a typical sol–gel method. Benefiting from the synergistic effect of Zn/Ti/F doping, the structure was stabilized and the phase transition of P2–O2 was inhibited. In particular, Na_0.67Ni_0.28Zn_0.05Mn_0.62Ti_0.05O_1.95F_0.05 (NNZMTOF) exhibited improved rate capability (79.5 mA h g⁻¹ at 10C) and excellent cycling stability (86% capacity retention after 1000 cycles at 10C). The assembled NNZMTOF//hard carbon full-cell could deliver a high energy density of 320.5 W h kg⁻¹. Therefore, such a Zn/Ti/F synergetic-doping strategy provides an effective and simple approach for designing layered oxide cathode materials with high energy density.