High-energy lithium-ion batteries (LIBs) can be realized with the use of nickel-rich materials, however, their reversible operation requires long-term cathode-electrolyte interfacial (CEI) stability, especially for high-temperature applications, but how the CEIs evolves during operation is still a mystery. The unstable CEIs have been recently ascribed to them generating/disappearing/regenerating during Li extraction/insertion by in situ Fourier Transform Infrared Spectroscopy spectrum. Herein, a strategy of insoluble CEI is proposed toward addressing the interfacially induced deterioration of cathodes with a focus on Ni-rich layered oxides. Incorporating unsaturated units (C-C/C-C) to siloxane as electrolyte additives advances the commercial LiNiCoMnO/graphite cells up to around 300 cycles at 60 °C with more than 85% capacity retention, along with the LiCoO cells reaching ≈90% capacity retention over 350 cycles under 80 °C. The experimentally and theoretically detailed investigation shows that the higher unsaturation bond with high reactive sites show more polymerization via a 3D topological pathway to form insoluble CEI species, leading to suppression of parasitic reactions, corrosive acid, transition-metal dissolution, stress corrosive cracking, and impedance growth. The scientific discoveries of this study highlight the pivotal role of electrode–electrolyte interactions and recapitulates the tried-and-true “electrolyte” approach for the future development of high-energy batteries under extreme temperature conditions.