Electrolyte engineering for a thermally and electrochemically stable interphase on 4.6 V LiCoO<sub>2</sub> at 45 °C

The development of high-voltage cathodes (e.g., LiCoO₂) is crucial for high-energy-density batteries, but their operation above 4.5 V accelerates interfacial degradation, particularly at high temperatures. To address this, Chen et al. introduce a multi-additive electrolyte strategy that synergistically constructs a robust, inorganic-rich cathode electrolyte interphase (CEI). The additives are designed to decompose sequentially and complementarily, forming a composite CEI layer with enhanced thermal and electrochemical stability. This engineered interphase effectively suppresses CEI dissolution and transition metal leaching, enabling stable cycling of LCO at 4.6 V and 45 °C. The study provides a generalized and practicable paradigm for designing functional interphases, applicable to other high-voltage cathode systems under extreme conditions.