Tailoring Stress and Ion-Transport Kinetics via a Molecular Layer Deposition-Induced Artificial Solid Electrolyte Interphase for Durable Silicon Composite Anodes

Silicon is considered as a blooming candidate material for next-generation lithium-ion batteries due to its low electrochemical potential and high theoretical capacity. However, its commercialization has been impeded by the poor cycling issue associated with severe volume changes (∼380%) upon (de)­lithiation. Herein, an organic–inorganic hybrid film of titanicone via molecular layer deposition (MLD) is proposed as an artificial solid electrolyte interphase (SEI) layer for Si anodes. This rigid-soft titanicone coating with Young’s modulus of 21 GPa can effectively relieve stress concentration during the lithiation process, guaranteeing the stability of the mechanical structure of a Si nanoparticles (NPs)@titanicone electrode. Benefiting from the long-strand (Ti–O–benzene–O–Ti−) unit design, the optimized Si NPs@70 cycle titanicone anode delivers a high Li+ diffusion coefficient and a low Li+ diffusion barrier, as revealed by galvanostatic intermittent titration (GITT) investigations and density functional theory (DFT) simulations, respectively. Ultimately, the Si NPs@70 cycle titanicone electrode shows high initial Coulombic efficiency (84%), long cycling stability (957 mAh g–1 after 450 cycles at 1 A g–1), a stable SEI layer, and good rate performances. The molecular-scale design of the titanicone-protected Si anodes may bring in new opportunities to realize the next-generation lithium-ion batteries as well as other rechargeable batteries.