Interplay of matrix porosity and phase interfaces in lithium-ion transport of Sn–CS nanocomposites

Tin-carbon-silica (Sn-CS) nanocomposites are promising anode materials for lithium-ion batteries owing to their high theoretical capacity and structural stability. However, their performance is critically influenced by matrix porosity and interfacial transport barriers. In this work, a three-dimensional multiphysics model was developed to elucidate lithium-ion diffusion and charge transport across tin, carbon, and silica phases. The simulations reveal that an intermediate porosity of ∼40% offers the best balance between ionic mobility and structural integrity, while excessive porosity disrupts electronic pathways and low porosity limits electrolyte infiltration. Phase-resolved analysis highlights tin as the most efficient diffusion medium, whereas silica interfaces create significant bottlenecks that induce steep lithium concentration gradients and up to 20% capacity loss at high charge rates. Model validation against experimental data confirms the accuracy of the predictions. These findings demonstrate that tuning porosity and interfacial architecture can effectively mitigate diffusion limitations, providing a rational design strategy for next-generation Sn-based nanocomposites. Beyond anodes, the presented multiphysics approach offers a generalizable framework for understanding and optimizing transport processes in multifunctional nanostructured materials.