Investigation of In Situ Cross-linked Polyacrylic Acid-PEG Binder for Si-dominant Anodes in Lithium-Ion Full Cells

Abstract Silicon (Si) is a highly promising anode material for lithium-ion batteries due to its high theoretical capacity. However, its practical use is limited by significant volume changes and resulting degradation during cycling. To enhance the mechanical stability of the Si anode, polyacrylic acid (PAA), a prominently used binder, was cross-linked in situ during electrode fabrication with the bifunctional and ion-conducting poly(ethylene glycol) diglycidyl ether (PEGDGE). The resulting binder architecture was designed to strengthen the binder network while accommodating substantial volume changes during cycling. The epoxide-containing PEGDGE was incorporated into the binder or as functionalization on the silicon particles. The resulting pure silicon anodes exhibited strong adhesion and cohesion, contributing to improved electrochemical performance, as determined by cyclic voltammetry and long-term galvanostatic cycling (up to 150 cycles at 1C until state of health 80%). Post-mortem analysis revealed well-maintained electrode morphology and the formation of a LiF-rich, stable solid electrolyte interphase (SEI) as identified by SEM and XPS, respectively. These results highlight the potential of the cross-linker to enhance the structural integrity and the electrochemical performance of silicon anodes.