Design Strategies for Silicon-Based Anodes in All-Solid-State Lithium-Ion Batteries: Phosphorus Doping, Silicide Composite Engineering, and Interfacial Insights

Abstract Silicon (Si)-based anodes are promising candidates for all-solid-state lithium-ion batteries (ASSLIBs) because of their high theoretical capacity; however, poor cycling stability remains a critical challenge. Herein, we systematically evaluated the charge–discharge properties of two Si-based active materials (phosphorus (P)-doped Si and iron disilicide (FeSi2)/P-doped Si composites) as ASSLIB anodes. Both materials have previously demonstrated superior electrochemical performance in liquid electrolyte cells. The Si reference electrode delivered an initial reversible capacity of ∼2440 mA h g(Si)–1; however, the capacity faded rapidly, with ∼13% of the initial capacity being lost within 10 cycles. Conversely, the P-doped Si electrode exhibited ∼10% higher initial capacity and superior capacity retention. The FeSi2/P-doped Si electrode maintained >90% of its capacity after 100 cycles. Particle size homogenization via sieving further improved charge–discharge cycling stability. Micro-Raman spectroscopy findings indicated that the high electronic resistivity of pure Si electrodes may give rise to more spatially variable Raman responses, potentially reflecting less uniform lithiation across the electrode surface. The reduced resistivity of P-doped Si and FeSi2/P-doped Si appeared to promote more spatially consistent Raman features, consistent with more uniform lithiation–delithiation behavior. The superior performance of the FeSi2/P-doped Si electrode was further attributed to, its order-of-magnitude, higher electronic conductivity in comparison with Si. Silicide incorporation reduced the molding and stack pressures required during cell fabrication, showing the potential of silicide-based electrodes to enable pressure-free ASSLIB construction. These findings collectively establish rational design strategies for Si-based anodes and identify silicide/Si composites as a viable pathway toward the practical realization of ASSLIBs.