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

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.

Automated summary

The partial lithiation of silicon microparticles in LIB anodes is a promising material concept with high capacity and rate capability, but is currently limited by cycling stability and volume change issues, restricting its market potential. This study identifies the continuous formation of SEI as the main failure mechanism, while particle decoupling plays a role at low discharge voltages. Improving cell performance involves optimizing electronic particle connection and developing enhanced electrolyte systems or pre-lithiation strategies to enhance the cycle stability of silicon-based LIB cells.