Revealing the size-dependent electrochemical Li-storage behaviors of SiO-based anodes

Abstract

Silicon monoxide (SiO) is a potential high-capacity anode material for lithium-ion batteries. The complexity of the lithiation process for SiO and challenges in the characterization of the lithiated products are fundamental aspects that underpin the discovery of the reaction mechanisms. In this work, we investigate the size-dependent (micro- and submicro-) electrochemical behaviors of SiO electrodes in terms of the irreversibility/reversibility of electrochemical lithiation/delithiation, interfacial/bulk stability, and interplay between SiO and graphite particles in the blended electrode. The irreversible Li⁺ consumption falls into three categories: O-participating electrochemical reactions of the Li–Si–O system, volume variation–induced inert Li_xSi alloy, and continued side reactions caused by the decomposition of the electrolyte. Reducing the particle size of SiO could hinder the formation of isolated inert Li_xSi alloys. However, the interfacial decomposition of the electrolyte is serious due to the high specific surface area. For the SiO/graphite blended electrode, it is confirmed that the graphite particles can buffer the volume change of SiO particles to some extent (<20 wt%), and the by-products of the SiO-related electrolyte decomposition would in turn hinder the lithiation/delithiation process of graphite particles. After decreasing the particle size of SiO, a more homogeneously distributed electrode is obtained and the cycling stability can be improved.