Weakly solvated electrolyte enables the robust solid electrolyte interface on SiOx anodes for lithium-ion battery

Abstract

Silicon oxide (SiOx) anodes are considered to be the promising alternative to graphite anodes for lithium-ion batteries. However, the traditional carbonate electrolyte fails to generate the effective solid electrolyte interface (SEI) on SiOx anodes to well adapt the large volume expansion of SiOx particles. Herein, a weakly solvated perfluorinated electrolyte with dual lithium salts was designed to match SiOx anodes. The perfluorinated solvent with weakened solvation ability and the strong coordination of Li+-DFOB− and Li+-TFSI− lead to an anion-dominated solvated shell, which induces the formation of inorganics-rich SEI. The high-strength bonds (Li-F, B-F, B-O, B-N et al.) enable high mechanical strength and rapid ion migration of the SEI film, thereby effectively accommodating the volume expansion of SiOx and avoiding continuous decomposition of the electrolyte. Furthermore, as designed electrolyte also shows excellent flame retardancy and high voltage stability. Consequently, the SiOx anode exhibits remarkably improved cycling performance in contrast to that in traditional carbonate electrolyte, maintaining 1073.7 mAh/g after 300 cycles at 1.0 A/g when paired with metal Li, and presents excellent compatibility with commercial cathodes including LiFePO4 and LiNi0.8Co0.1Mn0.1O2. This work provides a new inspiration and path for the design of electrolyte highly matched with silicon oxide anodes.