Regulating solvated sheath with anion chelant enables 4.6 V ultra-stable commercial LiCoO2.

Abstract

Increasing cut-off voltage of lithium cobalt oxide (LCO) (> 4.6 V) is an effective strategy to satisfy the ever-increasing demand for high energy density. However, the irreversible phase transition significantly destroys the structure of high-voltage LCO, especially the surface lattice. Considering that the structural stability of LCO is primarily dominated by the intrinsic merits of electrode-electrolyte interface (EEI), we explored and disclosed the operating mechanism of anion chelating agent tris(pentafluorophenyl) borane (TPFPB) and regulate the CEI layer on LCO electrode. Benefiting from the high HOMO energy level and preferential decomposition of TPFPB-PF6-, a robust LiF-rich CEI layer is constructed and greatly improves the stability of electrode/electrolyte interface. The well-designed electrolyte composed of 1 mol L-1 LiPF6 in EC/EMC with TPFPB additives endows Li/LCO half cells and 4 Ah Gr/LCO pouch cell with enhanced cycling stability under a high voltage condition. This work provides pave a new direction for the development of economical high-voltage LIBs.