Sulfolane-dissolved lithium nitrate in carbonate-based composite polymer electrolyte enables dual-interface stabilization for LiCoO2 Battery at 4.6 V

LiCoO 2 (LCO) stands as one of the dominant cathode materials in commercial lithium-ion batteries due to its high energy density and extended cycle life. However, irreversible structural phase transitions (O3 to H1–3) are triggered when the LCO is charged beyond 4.4 V, accompanied by lattice oxygen release and cobalt dissolution. These phenomena aggravate cathode electrolyte interfacial side reactions, ultimately resulting in progressive capacity decay and coulombic efficiency deterioration. Herein, capitalizing on the high solubility of LiNO 3 in sulfolane (SUL), a novel carbonate-based composite polymer electrolyte (CPE) was engineered to in-situ construct cathode electrolyte interface (CEI) layer enriched with Li 3 N, Li 2 O, Li 2 SO 4 , Li 2 SO 3 , and RSO 3 Li through LiNO 3 decomposition, effectively suppressing cobalt dissolution. Remarkably, capacity retention of 73.93 % was reached after 100 cycles under 4.6 V. This work highlights a synergistic SUL-LiNO 3 interfacial modulation strategy, offering a pioneering electrolyte design paradigm for 4.6 V-class LCO batteries.