Decoding the Intrinsic Link Between Interphase Stripping and Low Initial Coulombic Efficiency of Silicon Anodes in Li-Ion Batteries

Abstract

Silicon has emerged as a premier candidate for next-generation lithium-ion battery anodes. Nevertheless, the low initial Coulombic efficiency (ICE) hinders its commercialization. The mainstream view is that the continuous growth of the solid electrolyte interphase (SEI) on the silicon surface depletes the lithium inventory. In this work, a new mechanism is proposed that the SEI strips off the interphase with silicon as the silicon shrinks during discharge, which is the origin of the low ICE. A mathematical model is developed to describe this phenomenon, and the results demonstrate the ICE of 62%. Based on these findings, an external pressure inhibition mechanism of the interphase stripping is proposed, which can realize a 14% improvement. As a proof-of-concept, a capacity utilization improvement of 63% is also achieved under proper external pressure. This mechanistic and pressure modulation strategy establish a paradigm-shifting approach to overcome the limitations of silicon anodes.

Keywords: Silicon particle; Solid electrolyte interphase; interphase stripping, initial Coulombic efficiency.