Electrochemical Stabilization of PTFE in Thick Dry‐Processed Hard Carbon Electrodes via Inorganic‐Rich SEI Engineering for Scalable and Durable Sodium‐Ion Batteries

ABSTRACT Polytetrafluoroethylene (PTFE)‐based dry‐process electrode manufacturing represents a promising strategy for the low‐cost, scalable production of high‐loading electrodes. However, the practical application of high‐loading dry‐processed hard carbon (HC) anodes in sodium‐ion batteries is still hindered by their unsatisfactory electrochemical performance, while the mechanism underlying performance fading remains unclear. Here, dry‐processed sodium iron pyrophosphate phosphate (NFPP) cathodes and HC anodes were fabricated via PTFE fibrillation and their Na + storage performance were systematically evaluated from electrode to pouch cell level. The dry electrodes exhibited superior kinetics and high‐loading capability. Importantly, NFPP performance remained unaffected, while dry‐processed HC suffered from capacity decay, originating from side reactions between PTFE and sodiated HC. Guided by this insight, an optimized electrolyte was developed to form a stable inorganic‐rich SEI that suppresses PTFE reduction, thereby enabling high‐loading dry electrodes with high energy density and excellent electrochemical performance, as evidenced by a capacity retention exceeding 83% after 1700 cycles at 45°C in a 1000 mAh sodium‐ion pouch cell.