Bulk Oxygen Stabilization via Electrode-Electrolyte Interphase Tailored Surface Activities of Li-Rich Cathodes

The O3-type Li-rich layered oxides (LLOs) are approaching industrial applications as high-energy cathode materials for Li-ion batteries (LIBs), however, they suffer from rapid performance decay associated with oxygen activities. The interplay between surface and bulk transformations in LLOs, especially the electrochemical behaviors of oxygen anions, remains elusive. Here, by regulating the surface of an O3-type LLO (Li1.13Mn0.517Ni0.256Co0.097O2) using an all-fluorinated electrolyte, an enhanced capacity retention from 57.4% to 85.3% and a suppressed voltage decay from 1.34 mV cycle(-1) to 0.58 mV cycle(-1) within 300 cycles are realized. The performance enhancement is attributed to the thin, uniform, robust, and compact F-rich cathode-electrolyte interphase (CEI), which suppresses various types of oxygen-related surface degradation and, more importantly, stabilizes the bulk oxygen reactions. Through the combined experimental and theoretical studies, this work directly reveals the intriguing association between the surface and bulk oxygen activities and demonstrates that optimizing the interphase is an effective approach for improving the stability of high-energy battery cathodes involving oxygen redox reactions.

Automated summary

This study successfully improves the capacity retention and suppresses voltage decay of Li-rich layered oxides by regulating the surface of the material. The enhanced performance is attributed to the thin, uniform, robust, and compact cathode-electrolyte interphase (CEI) which suppresses surface degradation and stabilizes bulk oxygen reactions.