Engineering an Insoluble Cathode Electrolyte Interphase Enabling High Performance NCM811//Graphite Pouch Cell at 60 °C. Issue 33 (21st July 2022) - Chen, Yuqing
Abstract: 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 LiNi0.8 Co0.1 Mn0.1 O2 /graphite cells up to around 300 cycles at 60 °C with more than 85% capacity retention, along with the LiCoO2 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. Abstract : Insoluble cathode electrolyte interphases (CEI) derived from unsaturated siloxane additives make commercial pouch cell cycle stably with insignificant capacity fade even under elevated temperature. The unsaturated bonds electrochemical polymerize when oxidising, thus enhancing the stability of the CEI, which effectively suppresses the stress corrosive cracking, and side reactions under high‐temperature conditions.