Boosting high voltage cycling of LiCoO2 cathode via triisopropanolamine cyclic borate electrolyte additive

Abstract

Energy density of lithium-ion batteries (LIBs) can be promoted by raising the charge cutoff voltage, which faces the challenges of accelerated structural and interfacial degradation. Introducing a functional electrolyte additive is considered as an effective approach by forming a robust and protective cathode electrolyte interphase (CEI). Herein, triisopropanolamine cyclic borate (TPCB) additive is probed for the first time as an electrolyte additive to significantly enhance the interfacial stability of LiCoO2 (LCO) cathode at high charge cutoff voltages (≥4.6 V). With optimized 0.5% TPCB in electrolyte, a thin (about 8 nm) and dense CEI layer, containing C–N, B–O/B–F species and less LiF, is generated to suppress the decomposition of electrolyte at high voltages and alleviate structure damage of LCO during long-term cycling. As a result, the LCO cathode in the TPCB-modified electrolyte displays remarkably enhanced capacity retention of 82.2% after 200 cycles at 1C at high charge cut-off 4.6 V, exceeding that of 63.2% in the Base electrolyte.