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

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.