Lotus root-like porous Na2MnPO4F·Na3V2(PO4)2F3/C as a high-performance cathode material for sodium-ion batteries

Na2MnPO4F has become a promising cathode candidate for next generation sodium ion batteries by virtue of its high working potential and theoretical capacity, but its electrochemical performance is restricted by its low electronic conductivity and sluggish Na+ diffusion. In this study, Na3V2(PO4)2F3 is introduced into the Na2MnPO4F cathode material to improve the electron/ionic conductivity by generating lattice defects and providing active sites for Na+ transportation. The structure, morphology and electrochemical properties of xNa2MnPO4F·yNa3V2(PO4)2F3/C materials are investigated thoroughly. It is found that the electrochemical performance of Na2MnPO4F is significantly elevated by the modification of Na3V2(PO4)2F3. The optimized lotus root-like porous Na2MnPO4F·Na3V2(PO4)2F3/C cathode material delivers the first specific discharge capacity of 126.6 mAh·g−1 at 0.05C, which is close to the theoretical specific capacity. Furthermore, the Na2MnPO4F·Na3V2(PO4)2F3/C cathode material also presents good rate performance (76.9 mAh·g−1 at 1C rate), and remains 93.2% capacity retention after 400 cycles. This paper demonstrates a promising guide to construct Na2MnPO4F-based cathode materials with superior electrochemical performance for sodium ion batteries.