Quantifying lithium loss in amorphous silicon thin-film anodes via titration-gas chromatography

Abstract

Silicon with a high theoretical capacity (3,579 mAh/g) is a promising anode candidate for lithium-ion batteries. However, commercialization is still impeded by low Coulombic efficiency, caused by solid electrolyte interphase (SEI) formation and trapped lithium (Li)-silicon (Si) alloy during repeated volume change. Quantifying capacity losses from each factor is crucial to formulate rational design strategies for further improvement. In this work, titration-gas chromatography and cryogenic transmission electron microscopy are applied to characterize the evolution of trapped Li-Si alloy and SEI growth in a silicon thin-film anode. It is found that continuous growth of the SEI is the dominant factor for lithium inventory loss during cycling, with only a marginal increase in trapped Li-Si alloy. This study offers a quantitative approach to differentiate Li in the SEI from trapped Li in Li-Si alloy through a silicon thin-film anode, providing unique insights into identifying critical bottlenecks for developing Si anodes. Li loss in silicon anode is a combination of SEI formation and trapped Li-Si alloy TGC quantifies the amount of trapped Li-Si alloy Cryo-TEM reveals the trapped Li-Si alloy intermix with SEI Growth of SEI is the dominant factor for capacity decay in Si thin-film anodes Silicon-based anodes for use in lithium-ion batteries are promising, but their fast degradation is not fully understood. Bao et al. apply gas titration chromatography for trapped Li-Si alloy quantification, revealing that interphase-consumed lithium is the primary reason for inferior cycle stability.