Generating lithium fluoride-abundant interphase on layered lithium-rich oxide cathode with lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide

Abstract

Layered Li-rich oxides (LLROs) attract much attention due to their high capacities. However, the electrolyte decomposition and interfacial reactions especially driven by the catalysis effect of high-valance transition metal ions under high voltage cause severe performance recession, hindering their practical applications. Lithium fluoride (LiF) is an effective component in both cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) films. In this work, lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide (LiHFDF) is employed as a novel electrolyte additive for generating LiF-abundant interphase on LLRO. With the addition of LiHFDF, the capacity retention and Coulombic efficiency of the LLRO are improved noticeably. In addition, the interfacial side reactions and voltage decay issues are mitigated. Transmission electron microscopy and X-ray photoelectron spectroscopy measurements confirm that a compact and thin CEI film with more LiF is formed on the cathode surface for the cell using LiHFDF, which is beneficial for the enhancement of the electrochemical performance. Moreover, differential scanning calorimetry (DSC) investigations reveal that the LLRO electrode with LiHFDF has improved safety compared to that with the blank electrolyte. This work provides an effective LiF-generating electrolyte additive for high-voltage LLROs, which is believed to be positive for other high-voltage cathode materials.