Quantitative measurement of solid electrolyte interphase growth on Si-based anode materials

Symmetric cells have been developed to evaluate electrode degradation directly associated with solid electrolyte interphase (SEI) growth in Li-ion cells. This limits their applications to only certain anodes, such as graphite and Li 4 Ti 5 O 12 . In this work, symmetric cells have been applied to investigate the degradation of high energy density anodes, such as Si-alloys, which undergo multiple degradation mechanisms, including mechanical failure and SEI growth. A Li inventory model has been developed to correlate the symmetric cell capacity fade and the multiple anode degradation mechanisms. Using symmetric cells with a pseudo-reference electrode, it was found that irreversible capacity caused by anode degradation can be partially compensated by a positive shift in electrode upper endpoint potential, which is key to interpreting degradation mechanisms. Importantly, a feasible method to measure Li consumption due to SEI growth on Si-alloys has been established using symmetric cells. This method could help battery researchers develop technologies to lower the SEI growth rate on Si-alloys. • Quantitative measurement of Si-based anode coulombic efficiency. • Electrolyte degradation and mechanical degradation independently measured. • Si-alloy coulombic efficiency measured independently in graphite blended electrodes. • Electrolyte degradation dependance on Si-alloy composition and cycling temperature. • New perspectives on symmetric cell use and data interpretation.