Mg²⁺and Mn²⁺ bimetallic co-doped Na₃V₂(PO₄)₃ as advanced cathode for sodium-ion batteries

Na₃V₂(PO₄)₃ with open 3D framework structure is perceived as the most potential cathode material for sodium-ion batteries (SIBs). Nevertheless, its electrochemical properties are generally restricted by the larger radius of Na⁺ and the intrinsic poor electrical conductivity. Herein, we adopt a unique bimetallic doping strategy to prepare Mg²⁺ and Mn²⁺ co-doped Na₃V_2−x(Mg_0.5Mn_0.5)_x(PO₄)₃ [NVP-(MM)_x (x = 0, 0.01, 0.02)] through a high temperature solid state reaction. The as-prepared NVP-(MM)_0.01 presents a high initial discharge capacity of 107.7 mA h g⁻¹ at 1 C. Furthermore, NVP-(MM)_0.01 displays a highly rate capability (75.5 mA h g⁻¹ at 15 C) and excellent cycling performance (71 mA h g⁻¹ after 1000 cycles at 20 C). Electrochemical results exhibit that Mg²⁺ and Mn²⁺ co-doped with appropriate proportion can enhance the electronic conductivity and sodium storage kinetics process of Na₃V₂(PO₄)₃ effectively. Our work provides a novel idea to construct high performance SIBs via a bimetallic co-doped strategy.