Influence of Vinylene Carbonate Additive on the Li4Ti5O12 Electrode/Electrolyte Interface for Lithium-Ion Batteries

Abstract

The effect of Vinylene Carbonate (VC) additive upon the properties of the Solid Electrolyte Interphase (SEI) formed on top of Li4Ti5O12 (LTO) electrodes at 60°C, in relation with electrochemical data has been studied. Half cells LTO/Li were cycled at 60°C with VC-free and VC-containing electrolytes over 30 cycles and electrodes were analyzed by XPS after the first and tenth cycles. Scanning Auger Microscopy (SAM) analysis have also been performed after the first lithiation. XPS results show that for both electrolytes, a SEI is formed during lithiation of LTO electrodes and partially dissolved during delithiation. The use of VC promotes the formation of a thicker SEI since the first cycle, more stable toward dissolution and enhances the amount of organic compounds at the expense of LiF. SAM chemical mappings confirm the formation of a thicker and homogeneously distributed SEI at the first cycle for a VC-containing electrolyte. The dissolution process observed during delithiation mainly involves LiF without VC and Li2CO3 with VC. The formation of a thicker SEI implies higher capacity losses, which is consistent with electrochemical data showing higher capacity losses for a VC-containing electrolyte. VC additive is nonetheless expected to enhance the passivation of LTO electrodes over long cycling.