Acid Scavenging via Ion-Exchange Resin Coating Enables Durable High-Temperature Sodium-Ion Batteries

O3-type layered transition metal oxides are regarded as frontrunners for sodium (Na)-ion batteries (NIBs) due to their high capacity and ease of synthesis, but their practical deployment is hindered by interfacial instability. Herein, we reveal that sulfate-based electrolyte additives, 1,3-propanediol cyclic sulfate (PCS) and 1,3,2-dioxathiolane 2,2-dioxide (DTD), effectively construct a robust cathode-electrolyte interphase (CEI) at 25 °C, but hydrolysis at 60 °C releases acidic protons. This acidity promotes the decomposition of NaPF6 to generate corrosive HF, leading to aggressive lattice corrosion, CEI and transition metal (TM) dissolution. To overcome this dilemma, we applied a functional sodium-type ion-exchange resin coating on the cathode to scavenge protons via spontaneous ion exchange. This strategy effectively eliminates corrosive impurities and suppresses TM dissolution, significantly improving the high-temperature cycling stability. This work provides critical insights into electrolyte additive instability and establishes a facile solution for stabilizing electrode interfaces, paving the way for durable, high-performance NIBs.