Unveiling stability: Surface amidation-mediated covalent coupling for diminished volumetric changes in silicon/reduced graphene oxide (Si/RGO) composites as Li-ion battery anodes

Abstract

The preservation of Silicon nanoparticles (Si NPs)’ structural integrity and surface protection during cycling is vital for optimal Si-graphene electrodes, controlling volumetric changes during lithiation/delithiation. Weak physical adherence of Si NPs to the carbon matrix compromises electrode performance, highlighting the need for effective bonding mechanisms. This research focuses on Si/reduced graphene oxide (Si/RGO) composites, employing a scalable, low-temperature synthesis method to examine effect of bonding between Si NPs and RGO in mitigating the volumetric fluctuations during cycling. Characterization techniques, including FTIR, XRD, Raman spectroscopy, SEM, EDX and TGA confirm successful synthesis, offering structural and chemical insights. Electrochemical assessments, including EIS, CV, and GCD, reveal that covalently coupled Si/RGO composites outperform counterparts, demonstrating superior rate and cyclic performance. The first delithiation capacity of 1275 mAh g⁻¹ surpasses directly assembled Si/RGO and pristine RGO-based anodes, with corresponding values of 736 and 511 mAh g⁻¹, respectively and is retained to 670 mAh g⁻¹ (1.8 times the capacity compared to a graphite anode) at 0.1 A g⁻¹ after 100 cycles. Furthermore, the research challenges the notion that a high reduction temperature is obligatory for achieving high conductivity in RGO, as observed through improved charge/electron transfer kinetics, detailed in subsequent sections.