Phosphorus-doped amorphous TiO2/C interface enables hierarchical SEI formation on micron-sized SiO anodes for ultra-stable lithium-ion batteries†

Abstract

Silicon monoxide (SiO) has shown huge potential as a powerful anode material for lithium-ion batteries (LIBs), yet its practical implementation is constrained by substantial volume fluctuation and erratic solid-electrolyte interphase (SEI) creation. In this study, we report a phosphorus-doped amorphous TiO₂/C hybrid coated SiO (TP-SiO/C) that simultaneously enhances electronic conductivity and constructs a robust inorganic-rich tri-component SEI composed of LiF, Li₂CO₃ and Li₃P. First-principles calculations demonstrate that phosphorus doping induces electronic structure modulation in TiO₂, lowering both bandgap energy and Li⁺ adsorption barriers, which synergistically accelerates interfacial charge transfer and Li⁺ desolvation kinetics. Comprehensive in situ and ex situ investigations reveal that the phosphorus-doped interface induces a distinct SEI formation pathway: preferentially formed inner Li₃P catalyzes the growth of a dense outer SEI rich in Li₂CO₃ and LiF. This hierarchical architecture significantly lowers the energy barriers for Li⁺ desolvation and diffusion across the SEI, enabling stable and fast interfacial transport. The constructed TP-SiO/C electrode maintains 730.9 mA h g⁻¹ after 500 cycles at 2 A g⁻¹ with 84.98% initial coulombic efficiency. This finding provides new insights into interfacial design for high-energy silicon-based anodes through targeted SEI composition regulation.