PolymerBrush-GraftedSilicon Nanoparticles as a Binder-FreeAnode for Enhanced Lithium-Ion Battery Performance

Silicon (Si) anodes offer a high theoretical energy capacity but face challenges due to significant volume changes during cycling, which lead to Si particle pulverization, electrode delamination, and ultimately poor cycle-life performance. This study introduces Si nanoparticles grafted with polymer brushes as a binder-free, high-performance lithium-ion battery anode material. Si nanoparticles are initially coated with poly{(3,4-ethylenedioxythiophene)-<i>co</i>-3-[1-ethyl-2-(2-bromoisobutyrate)]thiophene} (P(EDOT-<i>co</i>-EBBT)), which acts as both an electrical conductor and a surface initiator for surface-initiated atom transfer radical polymerization (SI-ATRP). Through SI-ATRP, poly(methacrylic acid) (PMAA) brushes are then grafted, forming a Si@P(EDOT-<i>co</i>-EBBT)-<i>g</i>-PMAA brush structure. The chemical structure of the Si@P(EDOT-<i>co</i>-EBBT)-<i>g</i>-PMAA brush is characterized by infrared spectroscopy, while its core–shell structure is confirmed through scanning electron microscopy and transmission electron microscopy. The Si composite anode exhibits a high charge capacity of 2694 mA h g^–1 at 0.2C, enhanced C-rate performance, and good cycle-life stability. Rheological measurements indicate strong interactions between the PMAA brushes of Si nanoparticles, enabling PMAA to function effectively as a binder. Peeling tests show improved adhesion properties for the Si@P(EDOT-<i>co</i>-EBBT)-<i>g</i>-PMAA composite electrode. Electrochemical impedance spectroscopy reveals reduced resistance, and cyclic voltammetry confirms a high redox diffusion coefficient for the Si@P(EDOT-<i>co</i>-EBBT)-<i>g</i>-PMAA brush anodes. This approach, utilizing polymer-grafted Si nanoparticles as a binder-free anode, significantly enhances the performance of lithium-ion batteries and represents a promising advancement in anode material development.