Toward a fundamental understanding of the heterogeneous multiphysics behaviors of silicon monoxide/graphite composite anodes

Silicon monoxide (SiO) (silicon [Si] mixed with silicon dioxide [SiO2])/graphite (Gr) composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion batteries. The major bottleneck for SiO/Gr composite anode is the poor cyclability arising from the stress/strain behaviors due to the mismatch between two heterogenous materials during the lithiation/delithiation process. To date, a meticulous and quantitative understanding of the highly nonlinear coupling behaviors of such materials is still lacking. Herein, an electro-chemo-mechanics-coupled detailed model containing particle geometries is established. The underlying mechanism of the regulation between SiO and Gr components during electrochemical cycling is quantitatively revealed. We discover that increasing the SiO weight percentage (wt%) reduces the utilization efficiency of the active materials at the same 1 C rate charging and enhances the hindering effects of stress-driven flux on diffusion. In addition, the mechanical constraint demonstrates a balanced effect on the overall performance of cells and the local behaviors of particles. This study provides new insights into the fundamental interactions between SiO and Gr materials and advances the investigation methodology for the design and evaluation of next-generation high-energy-density batteries.