Mo_4.8Si₃C_0.6/MoC/SiOC Nanocomposite: A kinetics-Enhanced Anode Material for Lithium-Ion Batteries

Silicon oxycarbide (SiOC) is a promising anode material for lithium-ion batteries, yet its practical application is limited by low initial Coulombic efficiency (ICE), sluggish ion kinetics, and poor intrinsic electrical conductivity. Herein, SiMoOC-based ceramic nanocomposites derived from molybdenum-containing polysiloxane were prepared for lithium-ion storage. The molecular structure of the preceramic precursors and resulted chemical composition of the nanocomposites enable in situ formation of both Nowotny phase (Mo_4.8Si₃C_0.6) and MoC nanocrystals within the SiOC matrix. The Mo_4.8Si₃C_0.6/MoC/SiOC nanocomposites exhibit strongly enhanced electrochemical performance with the reversible capacity up to 883.59 mAh g^-1, notably demonstrating an increased ICE from 67.7% to 75.9%, retaining a specific capacity of 455.2 mAh g^-1 after 500 cycles at a high current density of 1 A g^-1. The enhanced performance can be attributed to the Mo_4.8Si₃C_0.6 and MoC nanocrystals with appropriate combination and microstructure: the highly conductive Mo_4.8Si₃C_0.6 nanoparticles synergistically construct an efficient conductive network with ultrafine MoC nanocrystals, which not only contribute reversible capacity as active sites but also effectively regulate the solid electrolyte interphase (SEI). This unique microstructure comprehensively optimizes electrode reaction kinetics by constructing multidimensional lithium-ion transport pathways and enriching active sites, simultaneously achieving high specific capacity, high reaction reversibility, and long-term cycling stability.