The Electrochemical Stabilization of Silicon Anodes via a Locally Concentrated LiNO3 Complex

Abstract

The solid electrolyte interphase (SEI) plays an integral role in regulating the stability of lithium-ion batteries, particularly those employing next-generation anode materials like lithium (Li)-metal or silicon (Si). Herein, a locally concentrated additive framework is designed to incorporate a LiNO3 sacrificial additive into conventional carbonate-containing electrolytes to heighten electrochemical stability in such systems. Though LiNO3 is effectively insoluble in carbonate solvents, it is introduced in moderate amounts to the electrolyte in the form of a highly concentrated diglyme complex, which is then dispersed and diluted throughout the bulk carbonate electrolyte in a homogenous, liquid, phase-stable solution. The addition of this additive complex considerably enhances the electrochemical stability of 4 V systems containing Li-metal or Si anodes over the course of cycling as well as during potentiostatic holds. It is shown that the sacrificial reduction of LiNO3 leads to the formation of favorable nitrogen-containing species on the surface of Si, like what is known to occur with Li-metal. However, the initial deposition of these products is found to transform the SEI towards having greater inorganic character overall, with significantly more embedded LiF throughout. These insights expand our understanding of electrolyte and SEI design for electrochemically resilient next-generation anode systems.