Engineering Purity and Electrical Conductivity of Na₄Fe₃(PO₄)₂(P₂O₇)/Carbon Booms the Electrochemical Performance in Sodium-Ion Batteries

Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) has emerged as a highly promising cathode material in sodium-ion batteries (SIBs). However, it suffers from the limited electrochemical performance due to the impurity and low electrical conductivity. Here, we demonstrate a high electrically conductive amorphous carbon-coated high-purity NFPP composite (NFPP/C-0.5) via a straightforward solid-state reaction method. The composite exhibits great improved electrochemical performance with a high capacity of 125 mA h g –1 at 0.1C, good rate performance (86 mA h g –1 at 20C), and a promising cycling stability of 98.1% capacity retention after 500 cycles at 5C. This advance in the electrochemical performance of the composite results from sucrose that plays a reducing role in the synthesis of NFPP to facilitate the phase purity of NFPP and becomes the electrically conductive amorphous carbon-coated NFPP to increase the electrical conductivity of NFPP/C-0.5. This work is beneficial for the design of cathode materials for SIBs.