A Sol‐Gel Derived Sodium Iron Pyrophosphate Sulfate Cathode Material for High‐Performance Sodium‐Ion Batteries

ABSTRACT Sodium‐ion batteries (SIBs) have shown significant potential for application in large‐scale energy storage systems due to their abundance of sodium resources, cost‐effectiveness, and environmental compatibility. Polyanionic cathode materials, with their unique crystal structure and high theoretical specific capacity, have become a focus of research in SIBs. In this study, we develop a novel pyrophosphate‐ and sulfate‐containing Na 2+2x Fe 2‐x P 2 O 7 SO 4 (NFPS) polyanionic chemical material featuring a three‐dimensional open‐framework structure for the first time via the sol‐gel method. The diffraction peaks are successfully indexed to the P na2 1 orthorhombic system for NFPS. In situ carbon‐coated NFPS cathode materials are prepared successfully with a lower‐cost biomass carbon source. The cathode material delivers an initial specific capacity of up to 101.46 mAh g −1 at 0.05 C and retains 83.56% of its capacity after 500 cycles at 5 C, demonstrating its feasibility for application in SIBs. This study provides an innovative NFPS polyanionic material and methods for developing high‐performance cathode materials for SIBs, which are expected to promote the application of SIBs in large‐scale energy storage.