The interface interaction of sulfur-doped carbon boosting kinetics of Na4Fe3(PO4)2(P2O7) for high rate and stable sodium-ion batteries
Iron-based mixed phosphates are considered promising cathode materials for sodium-ion batteries (SIBs) due to low cost, non-toxicity, and high structural stability. However, their electrochemical performance is limited by poor electronic conductivity and sluggish ion diffusion. This study presents Na4Fe3(PO4)2(P2O7) with porous coral-like S-doped carbon (NFPP-U0.5%) as cathode material for SIBs. The porous coral-like structure of the S-doped carbon layer, along with C–S–Fe interaction, significantly enhances electronic conductivity and sodium ion diffusion. NFPP-U0.5% delivers excellent rate performance, achieving 80.3 mAh g−1 at 20 C. In-situ X-ray diffraction analysis reveals that the C–S–Fe interaction, combined with the unique carbon structure, contributes to a small lattice volume change during cycling. NFPP-U0.5% reached an ultra-long cycling life with capacity retention of 82.66% after 25,000 cycles at 20 C. The outstanding electrochemical performances and unique interface interaction demonstrate that S-doped carbon coating NFPP is of high potential as a cathode material for low cost and long-lasting cyclability energy storage systems.