Sustained releasing superoxo scavenger for tailoring the electrode-electrolyte interface on Li-rich cathode

Abstract

Triggering O-related anionic redox reactivity can introduce additional capacity in Li-rich layered oxide (LRLO) cathode, while, activated oxygen species also threatens to electrode-electrolyte interface stability. Herein, revealed by in-situ SERS/Raman, we demonstrate that enrichment of superoxo-related species on LRLO surface would significantly aggravate electrolyte degradation by nucleophilic attack, and confuse/deteriorate the architecture of cathode electrolyte interface (CEI) on LRLO. Through rational introducing LiBOB as a boron-contained electrolyte additive, enhanced CEI was achieved with BOB-derived cross-linking and B-F/BxOy polymeric components. More importantly, benefitting from its synergy effect with LiPF6, the sustained release of LiDFOB acts as a superoxo scavenger, which efficiently eliminates related nucleophilic attack. Tailoring the CEI into a uniform, dense, and stable passivate protection front-face, LiBOB additive enhances the cycling stability of LRLO, delivered 92.5% capacity retention (300 cycles). This work arouses reconsideration on the design/modification principle of electrolyte for LRLO cathode, and emphasizes the in-situ superoxo scavenging process.