Branched Ether‐Driven Electrolyte Engineering for Resilient Inorganic‐Polymeric Interface on Micro‐Silicon Anodes in High‐Energy Li‐Ion Batteries

Abstract Micro silicon (µm‐Si) is considered an ideal anode material for next‐generation lithium‐ion batteries owing to its high specific capacity and cost‐effectiveness. However, SEIs formed in traditional electrolytes lack sufficient elasticity and mechanical strength due to organic/low‐polymeric compounds and limited inorganic components, exacerbating their corrosion/aging and causing electrode collapse. The low ICE and prelithiation requirement also hinders the practical development of Si anodes. Here, a novel branched ether solvent, dipropylene glycol methyl propyl ether (DPMPE), with high steric hindrance and asymmetric structure, enabling its electrolyte system to simultaneously generate LiF‐rich inorganics and polyether component via in situ electrochemical polymerization in SEI, is proposed. The boron‐based additive forms boron‐containing polymer species synergizing with polyether to build a more durable bi‐polymeric SEI. MALDI‐TOF‐MS detect the polymerization species in SEIs, elucidating their polymerization mechanism. The optimized electrolyte enables stable cycling of µm‐Si anodes at 4 mAh cm ⁻² with 93.03% ICE. The electrolyte‐induced CEI layer effectively suppresses ether solvent decomposition on the cathode. Consequently, the NCM811//µm‐Si coin cell retains 80.9% capacity after 200 cycles, while non‐prelithiated 70 mAh pouch cells also exhibit stable cycling. A 2‐Ah NMC811//SiO/Gr pouch cell retains 81.86% capacity after 200 cycles under lean electrolyte conditions (3 g Ah ⁻¹ ).