In-situ analysis of solid-electrolyte interphase formation and cycle behavior of Sn battery anodes

Abstract

Tin is in principle one of the most promising candidates for a lithium-ion battery anode due to its larger capacity than that of commercial graphite anode. But, researchers are still confused about the capacity fade especially caused by the formation of solid electrolyte interface (SEI). Here, cyclic voltammetry is conducted in combination with a quartz crystal microbalance to characterize the growth of SEI in-situ, since detected mass change per charge (MPE) enables identification of the ab/desorbed species. In advanced analysis, we combine three different characteristics including mass spectra, real-time MPE and average MPE, for the overall and segmented study on the long-term SEI formation. Beside the formation of the organic and inorganic SEI layer in the first cycle, the SEI is continuously affected by the formation of Li2O during lithiation and the oxidation of Sn during de-lithiation, which was further proved by XRD, XPS, SEM and TEM results. Beside Li, a heavier species (probably Li2O) is reversibly cycled with a relative contribution of 23% compared to the cycled Li. We believe that the analysis strategy used here for the SEI on Sn provides a significant example for general in-situ SEI growth studies.