Large Scalable Preparation of Ti-Doped Na₄Fe₃(PO₄)₂P₂O₇ as Cathode Material for High Rate and Long-Life Sodium-Ion Batteries

Na₄Fe₃(PO₄)₂P₂O₇ (NFPP), with high theoretical capacity, excellent structural stability, wide raw material sources, and environmental friendliness, has drawn much attention in the field of large-scale energy storage. However, the intrinsic low electrical conductivity and complex synthesis process of NFPP limit its application. Herein, a green and scalable synthesis strategy was developed to prepare a NFPP/C composite using FePO₄ and Na₂CO₃ as source materials. Additionally, synergistic modification of the Ti-doping strategy and composite carbon coating is used to enhance the material’s low electrical conductivity, which will contribute to increased capacity for discharge and cycle stability. The prepared Ti-NFPP/C cathode exhibits excellent rate performance (66.7 mAh g^–1 at 30 C) and cycling stability (capacity retention of 93.8% after 2000 cycles at 10 C). Moreover, the full battery (Ti-Na₄Fe₃(PO₄)₂P₂O₇/C//HC) assembled with Ti-NFPP/C and hard carbon (HC) exhibits an energy density of 145 Wh kg^–1 at 0.5 C. These results provide a feasible approach for the industrialization of cathode materials for sodium-ion batteries.