Synergy of Epoxy Chemical Tethers and Defect‐Free Graphene in Enabling Stable Lithium Cycling of Silicon Nanoparticles

Abstract We report a new approach for nanosilicon–graphene hybrids with uniquely stable solid electrolyte interphase. Expanded graphite is gently exfoliated creating “defect‐free” graphene that is non‐catalytic towards electrolyte decomposition, simultaneously introducing high mass loading (48 wt. %) Si nanoparticles. Silane surface treatment creates epoxy chemical tethers, mechanically binding nano‐Si to CMC binder through epoxy ring‐opening reaction while stabilizing the Si surface chemistry. Epoxy‐tethered silicon pristine–graphene hybrid “E‐Si‐pG” exhibits state‐of‐the‐art performance in full battery opposing commercial mass loading (12 mg cm −2 ) LiCoO 2 (LCO) cathode. At 0.4 C, with areal capacity of 1.62 mAh cm −2 and energy of 437 Wh kg −1 , achieving 1.32 mAh cm −2 , 340.4 Wh kg −1 at 1 C. After 150 cycles, it retains 1.25 mAh cm −2 , 306.5 Wh kg −1 . Sputter‐down XPS demonstrates survival of surface C‐Si‐O‐Si groups in E‐Si‐pG after repeated cycling. The discovered synergy between support defects, chemical‐mechanical stabilization of Si surfaces, and SEI‐related failure may become key LIB anode design rule.