Multifunctional Phosphorus Doping: Integrating Enhanced Ionic/Electronic Transport and Interface Optimization for Silicon Oxycarbide Anodes

Abstract

Polymer-derived silicon oxycarbide (SiOC) is a promising anode material for lithium-ion batteries due to its high specific capacity, low operating potential, structural stability, and tunable components. However, its practical application is hindered by poor intrinsic electronic/ionic conductivity and unstable solid-electrolyte interphase (SEI). Herein, in this work, a phosphorus (P)-doped SiOC material was successfully synthesized, and the P is incorporated into the SiOC network via P–O–Si bonding. This P-doping strategy introduced additional free electrons and enhanced the ordering of free-carbon phase. Also, it induced the formation of LiF and Li₃PO₄-rich SEI. These modifications collaboratively led to good rate performance and cycling stability. The optimized SiOC-P electrode delivered a high reversible capacity of 860.1 mAh g⁻¹, an excellent capacity retention of 81.1% after 700 cycles at 1.0 A g⁻¹, and a good rate capacity of 383.4 mAh g⁻¹ even at 5.0 A g⁻¹. Density functional theory calculations also reveal that Si–O–P promotes the ionic/electronic transport among the SiOC-P bulk. This work offers valuable insights into heteroatom doping strategies for tailoring SiOC-based materials and facilitates their practical application in high-energy-density batteries.