Revealing the Failure Mechanism of Partially Lithiated Silicon-Dominant Anodes Based on Microscale Silicon Particles

Abstract

Due to its high capacity, rate capability and attractive cost position, the partial lithiation of silicon microparticles in anodes for Lithium Ion Batteries (LIB) is a material concept worth considering. Limitations in cycling stability and volume change currently limit its deployment to niche applications with moderate cycle life requirements and thus prevent a broader market introduction. The present study discusses the failure mechanism of LIB cells based on partially lithiated silicon dominant anodes. The loss of active lithium is reflected in a comparatively strong capacity decrease, especially at low cut-off voltages. The developed electrochemical methodology enables to differentiate between various loss contributions, such as lithium loss by electronic particle decoupling or particle isolation, trapping of mobile lithium and immobilization of lithium in the solid electrolyte interphase (SEI). The study identifies the continuous formation of SEI as the main failure mechanism, while particle decoupling, in addition, mainly contributes when operating at low discharge voltages. Approaches to increasing the cell performance consequently lie in the optimization of the electronic particle connection and in the development of improved electrolyte systems and/or pre-lithiation strategies to improve the cycle stability of silicon-based LIB cells.