Modulus-Engineered Silicates-Buffering Matrix for Enhanced Lithium Storage of Micro-Sized SiOx Anodes.

Abstract

Microscale Silicon suboxide (SiO_x) is a promising anode material and elemental doping is an effective strategy to enhance the initial coulombic efficiency (ICE) and cycle stability of SiO_x by converting SiO₂ into the electrochemically inert silicates-buffering matrix. However, the impact of the silicates-buffering modulus on the electrochemical properties is not well understood. Herein, the modulus of the silicate-buffering matrix is found to be crucial to restraining internal cracks and improving the electrochemical properties of microscale SiO_x during cycling. Compared with the Li₂SiO₃ and MgSiO₃ buffering matrixes, Mg₂SiO₄ has a higher modulus and yield stress resulting in better resistance to Si expansion-induced cracks during cycling. Moreover, Mg₂SiO₄ has a smaller Li⁺ diffusion energy barrier than Li₂SiO₃ and MgSiO₃. Consequently, the microscale Mg-doped SiO_x with the Mg₂SiO₄ buffering matrix has a high ICE, excellent structural integrity, and small electrode expansion during cycling. The results provide insights into the design of microscale SiO_x anode materials by optimizing the silicates-buffering matrix for high-energy Li-ion batteries.