Mn doped NaV3(PO4)3/C anode with high-rate and long cycle-life for sodium ion batteries

Abstract Mn-doped NaV3(PO4)3/C (NaV3-3xMn3x(PO4)3/C) has been synthesized by a facile sol-gel method and evaluated as a promising anode candidate for sodium-ion batteries (SIBs). An effective investigation combining in-situ XRD and ex-situ TEM is conducted to reveal the structure transformation of NaV3-xMnx(PO4)3/C, confirming that Mn substitution can effectively suppresses the unfavorable phase transition and improve the highly structural reversibility. Furthermore, electrochemical measurements indicate that the Na-ion mobility and reaction kinetic of NaV3-3xMn3x(PO4)3/C electrode are significantly enhanced, resulting in enhanced electrochemical performance. Especially, the NaV2.91Mn0.09(PO4)3/C composite displays remarkable rate capability and long cycling stability (a capacity retention of 71.2% after 5000 cycles at an ultrahigh rate of 10C). The strategy with appropriate metal ion substitution is suitable for the electrochemical enhancement of polyanion materials, which provides a new insight to optimal design for SIB anodes.