High performance polymer binders inspired by chemical finishing of textiles for silicon anodes in lithium ion batteries

Abstract

In the textile industry, chemical finishing of textiles by N-methylol acrylamide (NA) results in tenacious three-dimensional (3D) crosslinked polymer networks which can maintain wrinkle resistance of fabrics. Inspired by this chemical finishing method, we developed herein NA functionalized carboxymethyl cellulose (CMC) binders for Si anodes through free radical graft copolymerization of NA and acrylic acid (AA) onto CMC backbones. In this multifunctional binder, PAA and CMC with a high density of carboxyl groups offer binding ability with Si particles as well as with the copper (Cu) current collectors. Meanwhile, the methylol groups in NA condensate with the hydroxyl groups of CMC to form robust three-dimensional (3D) crosslinked networks. These help maintain integration of Si electrodes and build a stable SEI layer on the Si surface, leading to significant improvement in cycling performance of Si-based lithium ion batteries (LIBs) (94% capacity retention after 250 cycles). The high elastic modulus of the binders and weak interaction between the electrolyte and the binders are thought to account for the enhanced electrochemical performance of Si-based LIBs.