Achieving stable cathode-electrolyte interface via in-situ electrochemical structural rearrangement for high-voltage...

The cathode-electrolyte interphase (CEI) is vital in lithium ion batteries as its electron/ion transfer efficiency at the electrode-electrolyte boundary governs the overall reaction kinetics. However, the dynamic nature of the CEI during cycling compromises electrochemical stability, resulting in rapid capacity degradation. Herein, we propose a facile in-situ strategy to engineer a thin and robust CEI layer on LiCoO₂ (LCO) cathodes by making use of charge modulation between Co⁴⁺ and Mn³⁺. The passivization of reactive Co⁴⁺ sites at the surface effectively suppresses the continuous electrolyte decomposition and Co dissolution, subsequently mitigating surface structural phase distortion. Concurrently, the inhibited phase distortion stabilized the interfacial electric field, promoting the formation of a dynamically mechanically stable CEI with enhanced ionic conductivity. The modified LCO cathode achieves much better cycling stability, alongside improved rate capability. This work elucidates the critical interplay between charge modulation and CEI dynamics, offering a universally adaptable approach for designing high-performance layered oxide cathodes in metal-ion batteries.