In Situ Room-Temperature Cross-Linked Highly Branched Biopolymeric Binder Based on the Diels–Alder Reaction for High-Performance Silicon Anodes in Lithium-Ion Batteries

Silicon (Si) is an auspicious anode material in next-generation lithium-ion batteries due to its exceptional theoretical gravimetric capacity, environmental friendliness, and high natural abundance. However, the practical application of Si anodes remains a "must-solve" challenge because of its drastic capacity fading that results from the inherent property of drastic volume expansion of Si during repeated lithiation and delithiation. Developing binders employed in robust electrodes has been considered an economical and practical method to affect the electrochemical performance of Si-based electrodes. Some natural polymers have demonstrated good adhesive properties with Si-active materials. However, they have limited capacity to keep the structural integrity of electrodes because the network structures solely based on weak hydrogen bonds are susceptible to deformation during cycling. Herein, we develop an in situ covalently cross-linked three-dimensional (3D) supramolecular network and apply it to the Si electrode to improve cycling performance. This network architecture is constructed using furan-modified branched arabinoxylan of corn fiber gum (CFG) and an ionically conductive cross-linker of maleimido-poly(ethylene glycol) (PEG) through the Diels-Alder reaction. The maleimide groups in PEG can react spontaneously with the furan groups in CFG at room temperature without any other stimulation, thus forming strong covalent bonds in the network. The cross-linked CFG-PEG binder has demonstrated robust adhesive properties with Si-active materials and the current collector. The branching of CFG and functional groups of PEG are conducive to improving the lithium-ion conductivity in the silicon anode, resulting in excellent rate performances. The Si anode with a cross-linked CFG-PEG binder exhibits superior cycling stability. As a result, an in situ cross-linking 3D network as a novel binder has a great potential for fabricating an advanced Si anode in next-generation Li-ion batteries.