MoO42−-mediated engineering of Na3V2(PO4)3 as advanced cathode materials for sodium-ion batteries

Sodium vanadium phosphate [Na3V2(PO4)3] with high voltage platform, low cost and environment friendliness has been considered as one of the most promising candidates as cathodes for high-performance sodium-ion batteries. However, the sodium storage property of Na3V2(PO4)3 is limited because of its low electronic conductivity and poor kinetic performance. Herein, MoO42--doped Na(3+2x)V2(PO4)(3-x)MoO4(x) [NVP-MoO4 (x), x = 0, 0.05, 0.10, 0.15] have been developed and prepared by a feasible solid-state reaction. The optimal NVP-MoO4 (0.10) delivers a high initial capacity of 108.9 mA h g-1 and presents an excellent capacity retention of 91.5% at 1 C after 150 cycles. In addition, the NVP-MoO4 (0.10) shows a good rate capability, delivering a relatively high capacity of 84.2 mA h g-1 at 50 C. The results of sodium storage measurement and density of states calculation indicate that MoO42- doping can significantly enhance the structural stability, promote the kinetics behavior and boost the electronic conductivity of the materials. In-situ XRD test reveals that the electrochemical reaction of the NVP-MoO4 (0.10) exhibits a highly reversible phase transition process. This work provides a new insight for the design of advanced cathodes for high-performance sodium-ion batteries by the strategy of unique anion doping.