Abstract:

Cycle stability and specific capacity of cathode materials for sodium ion batteries play an important role in achieving their wide application. Based on the strategy of introducing specific heteroelements to optimize the structural stability and specific capacity of cathode materials, O3-Na_0.9Ni_0.5-xMn_0.3Ti_0.2Sb_xO₂ (NMTSb_x, x=0, 0.02, 0.04, 0.06) was prepared by a simple solid-state reaction method, and effects of Sb doping amount on the sodium storage properties of Na_0.9Ni_0.5Mn_0.3Ti_0.2O₂ cathode materials were investigated. The characterization results show that the electrostatic repulsion force between oxygen atoms in the transition metal layer is reduced after Sb doping, while the lattice spacing is expanded, which is conducive to deintercalation of Na⁺. Meanwhile, the strong electron delocalization caused by Sb doping decreases energy of the whole system, leading to a stable structure, more conducive to cyclic charging and discharging. The electrochemical test shows that initial discharge specific capacity of undoped NMTSb₀ is 122.8 mAh·g⁻¹ at 1C(240 mA·g⁻¹), and the capacity retention rate is only 41.5% after 200 cycles. But initial discharge specific capacity of doped NMTSb_0.04 is 135.2 mAh·g⁻¹ at 1C, and the capacity retention rate is up to 70% after 200 cycles. This study shows that Sb doped O3 type Na_0.9Ni_0.5Mn_0.3Ti_0.2O₂ cathode material can significantly improve initial discharge specific capacity and capacity retention rate of sodium ion batteries. Our results suggest that Sb doping strategy might be a useful approach for preparation of high stable sodium ion batteries..

Key words: Sb doping, O3 type, cathode material, solid phase method, wide voltage, Na-ion battery