Simulation-guided SiOx–graphite anode design for mitigating reaction heterogeneity and enhancing fast-charging performance in lithium-ion batteries

SiO x –graphite composite anodes offer high energy density and improved rate capability owing to the high theoretical capacity of SiO x (∼1400 mAh g −1 ); however, their cycle life under fast-charging conditions remains severely limited. This study presents a simulation-guided design strategy for SiO x –graphite composite anodes with enhanced fast-charging performance and cycle stability. Three-dimensional electrochemo-mechanical simulations reveal that conventional uniformly blended composite anodes exhibit preferential lithiation of both graphite and SiO x near the separator, where local electrochemical polarization promotes Li plating and mechanical constraint on nonuniform expansion generates stress, while the region near the current collector remains underutilized. Guided by these mechanistic insights and systematic design sweeps across the compositional parameter space, a bilayer composite anode with a depth-dependent SiO x distribution is proposed, wherein an elevated SiO x fraction near the separator suppresses Li plating and stress accumulation while a reduced fraction near the current collector promotes graphite lithiation—collectively homogenizing the reaction distributions without compromising energy density. Validated in LiNi 0.8 Co 0.1 Mn 0.1 O 2 full cells, the optimized bilayer anode achieves capacity retentions of 74.1% and 65.1% after 100 and 300 cycles, respectively, at 4C charging, outperforming the uniformly blended anode, with suppressed electrode swelling and no observable Li plating after cycling. This work demonstrates that simulation-guided compositional grading of SiO x along the electrode thickness provides a practical and scalable strategy for simultaneously improving fast-charging performance, cycle stability, and structural integrity in Li-ion batteries.