Cross-linked siloxane-based copolymer binder with combined hardness and softness for stable silicon anodes in Li-ion batteries

Silicon has become one of the most emerging anode materials in Li-ion batteries due to its excellent specific capacity. The incorporation of binders can significantly reduce the volume expansion of silicon during the cycling process. In this work, a novel type of cross-linked siloxane-based copolymer, poly (tert-butyl acrylate-co-vinyl tri-lactate ethyl silane) (TBA-VTLES) was designed and utilized as the binder for the silicon anode in Li-ion batteries to alleviate the inner stress of adverse volume changes and improve the electrochemical performance. The hard TBA and soft VTLES were interwoven into a 3D network to achieve the adhesive action via free radical polymerization. The soft chains in TBA-VTLES can enhance the cohesion of the copolymer to disperse residual stress, and thus avoid structural damage during lithiation. Meanwhile, the rigid chains can provide sufficient mechanical strength to maintain the integrity of silicon anode during de-lithiation. Moreover, the presence of TBA-VTLES can improve the adhesive strength between the copper collector and the binder. This novel type of siloxane-based copolymer binder with hardness and softness provides a feasible way to improve the silicon anode performance of Li-ion batteries. Graphical abstract The synthesized cross-linked copolymer binder can improve the interfacial interaction and electrochemical performance of Si anode-- present in Graphical abstract figure-- need or not.