Intercalation-Type SiOC Anode Exclusively Composed of SiO₃C Tetrahedral Unit for Stable Lithium-Ion Batteries

Silicon oxycarbide (SiOC) has been considered as a potential anode for lithium-ion batteries (LIBs) due to high theoretical capacity, low volume expansion, and abundant resources. However, the uncontrolled tetrahedral structure in the SiOC often leads to unsatisfactory specific capacity and cycling stability, hindering the practical application in LIBs. Herein, a facile I₂-catalyzed condensation reaction between ethylene glycol (EG) and vinyltriethoxysilane (VTES) has been proposed to prepare SiOC exclusively composed of SiO₃C tetrahedral units for the first time. This unique atomic configuration results in an intercalation-dominated lithium storage mechanism for I-SiOC anode, in which the reversible lithium storage primarily occurs at O sites, as demonstrated by the experimental data and theoretical calculations. Then SiOC electrode can deliver a high capacity of 1164.8 mAh g^-1 at 0.1 A g^-1 with an initial Coulombic efficiency of 84.1%, and exhibits no observable capacity decay after 2000 cycles at 1 A g^-1. When paired with an NCM811 cathode in a pouch cell, the full cell achieves a high energy density of 358.8 Wh kg^-1 and retains a high capacity ratio of 81.0% after 1300 cycles at 1 C. This work demonstrates that the structural engineering of a tetrahedral structure can be an efficient approach to design high-performance SiOC-based anodes.