Nonpassivated Silicon Anode Surface

A stable solid-electrolyte interphase (SEI) has been proven to be a key enabler to most advanced battery chemistries, where the reactivity between electrolyte and the anode operating beyond electrolyte stability limits must be kinetically suppressed by such SEI. The graphite anode used in state-of-the-art Li-ion batteries (LIBs) presents the most representative SEI example. Due to the similar operation potentials between graphite and silicon (Si), a similar passivation mechanism has been thought to apply on Si anode when using the same carbonate-based electrolytes. In this work, we found that the chemical formation process of a proto-SEI on Si is closely entangled with incessant SEI decomposition, detachment and reparation, which lead to continuous lithium consumption. Using a special galvanostatic protocol designed to observe the SEI formation prior to Si lithiation, we were able to deconvolute the electrochemical formation of such dynamic SEI from the morphology and mechanical complexities of Si, and showed that a pristine Si anode could not be fully passivated in carbonate-based electrolytes.