Alternative Multifunctional Cyclic Organosilicon as an Efficient Electrolyte Additive for High Performance Lithium-Ion Batteries

Abstract

Three kinds of functional organosilicons electrolyte additives, i. e. octamethylcyclotetrasiloxane (D4), octamethylcyclotetrasiloxane (OMCTS) and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetra- siloxane (ViD4), are firstly used to produce high-performance LiNi0.6Co0.2Mn0.2O2 cathode for rechargeable Lithium-ion batteries (NCM622/Li half-cell) at a high potential. The electrochemical performance tests at 4.5V suggest that ViD4 is the most promising electrolyte additive than its counterparts. Moreover, the prepared NCM622/Li half-cell with 0.5wt.% ViD4 exhibits an improved energy density of 187.2mAhg−1 and a good discharge capacity retention of 83.6% at 1C rate after 150 cycles at 4.5V, which is relatively higher than that with D4 (81.3%), OMCTS (81.9%) and much better than the bare electrolyte (76.1%). The electrochemical characterizations, density functional theory calculation and surface analysis provide strong evidences that combined effects of the Si-O bond and vinyl functional group in ViD4 can promote the formation of a uniform cathode electrolyte interphase (CEI) film. Moreover, the ViD4-incorporated CEI film effectively enhances the interfacial stability between the NCM622 cathode and the electrolyte by suppressing the continuous decomposition of carbonate-based electrolyte and the exfoliation of these decomposition products. Hence, the ViD4-containing electrolyte shows a promising potential for the application in high energy density lithium-ion batteries.