Surface Functionalization of Si Nanoparticles by Hydrosilylation: Access to High‐Performance Si Anodes for Li‐Ion Batteries

Silicon (Si) is the most promising anode material for Li‐ion batteries; yet, it suffers from large volume expansion of up to 300% and dynamic solid electrolyte interface (SEI) formation, resulting in rapid capacity decay and low cycle life. In this work, the surface of Si nanoparticles (SiNPs) with three different functional vinyl compounds, i.e., 4‐vinylpyridine, 1‐vinyl‐2‐pyrrolidinone, and acrylic acid, has been altered using a scalable hydrosilylation approach. Physical characterization reveals that the functional groups are covalently bound to the surface of the SiNPs and are extended for a few nanometers. The surface‐functionalized SiNPs overcome pulverization and unstable SEI formation, achieving a long life of 300 galvanostatic charge‐discharge (GCD) cycles at 200 mA g −1 . Particularly, 4‐vinylpyridine functionalized SiNPs (Si‐4VP) achieved an exceptional initial capacity of >3000 mAh g −1 . Such promising electrochemical performance is attributable to higher diffusion rates, resulting in a higher diffusive charge storage nature, as confirmed by kinetic studies. The findings conclusively demonstrate that controlled surface functionalization of SiNPs on the particle level is a scalable approach that results in exceptionally high capacity and long cycling stability of the Si anode in Li‐ion batteries.