Molecule polarity and steric hindrance design to nominate organosilicon additive for high-voltage LiCoO2

High-voltage LiCoO₂ (LCO) exhibits high capacity but suffers severe electrolyte decomposition and parasitic reactions. The cathode electrolyte interphase (CEI) is supposed to protect the cathode interface and enhance interfacial stability. However, in LiPF₆-based electrolytes, unavoidable acidic species like HF could corrode CEI, further facilitating side reactions. In general, organosilicon additives could not only capture acidic species but also participate in CEI formation. Here, we report an organosilicon design on optimizing molecular polarity and steric hindrance effect by tuning the phenyls and methoxy configuration. The designed Trimethoxyphenylsilane (TRSE) displays outstanding HF capture, LCO surface approaching tendency as well as anions binding ability, which could effectively suppress interfacial side reactions and assist advanced CEI construction to enhance the cycling stability at high voltage. As a result, the HF-limited electrolyte circumstances and the CEI with LiF and Si-F ingredients enrichment dramatically enhance capacity retention (∼32 % higher after 100 cycles at 1 C) and rate performance (∼80 mAh/g vs. ∼10 mAh/g at 10 C). This study offers fundamental insights into the advanced electrolyte additives design for high-voltage LCO batteries.