Unveiling the Effect of Surface and Bulk Structure on Electrochemical Properties of Disproportionated SiO_x Anodes

Abstract As a promising lithium‐ion battery anode materials, silicon suboxides (SiO_x) exhibit elusive microstructure with atomic‐scale disproportionation which reveals a strong relation to performance. Generally, the structure of SiO_x could be tuned via high‐temperature treatment. In this work, disproportionated SiO_x are prepared to systematically discuss the internal relationship among microstructure, physicochemical properties and electrochemical performance. After annealing, amorphous SiO₂ and nanocrystalline Si appear, and the SiO₂ accumulating on the surface results in large resistance and low Li‐ion diffusivity, which leads to large overpotential and poor performance. If mechanical milling is employed followed by annealing, the SiO₂ layer can be crushed, SiO_x and Si with electrochemical activity are uncovered. Further research on the SiO_x with diverse degrees of disproportionation indicates that proper amount of Si and SiO₂ determines the optimal electrochemical performance. This result gives an in‐depth understanding and probable guidance to the modification investigation of SiO_x anode for Li‐ion batteries.