Silicon ($\mathrm{Si}$)-graphite (Gr) composite anodes are crucial for high-energy-density lithium-ion batteries; however, the unclear correlations between component spatial distribution and performance hinder their practical application. Herein, based on a coupled electrochemical-mechanical model integrated with experimental validation, we systematically evaluate layered and homogeneous electrode configurations. Simulation results show that the migration of $\mathrm{Si}$ from the current collector to the separator side maximizes the transport of ${\mathrm{Li}}^{+}$ and electrons, thereby reducing the ${\mathrm{Li}}^{+}$ concentration gradient and lowering the electrode polarization. Positioning $\mathrm{Si}$ near the separator (top-layered $\mathrm{Si}$) promotes synchronized lithiation between $\mathrm{Si}$ and Gr, effectively suppressing interfacial ${\mathrm{Li}}^{+}$ crosstalk. In contrast, homogeneous models reveal that $\mathrm{Si}$ lithiation significantly reduces the lithiation degree of adjacent Gr regions. This leads to complex interactions among ${\mathrm{Li}}^{+}$ fluxes, electrolyte concentration gradients, and stress-strain fields, resulting in inferior lithiation kinetics compared to top-layered $\mathrm{Si}$ configurations. Experimental verification confirms superior cycling stability in top-layered $\mathrm{Si}$ architectures. These findings highlight the limitations of $\mathrm{Si}$ near the bottom current-collector side and homogeneous designs, providing guidance for optimizing electrode structures to mitigate polarization and capacity fading.

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• Electric polarization
• Electrochemistry
• Lithium-ion batteries
• Strain
• Transport phenomena
• Composite materials
• Finite-element method
• Multiscale modeling