Room-Temperature Crosslinkable Natural Polymer Binder for High-Rate and Stable Silicon Anodes

Abstract

Natural polymers with abundant side functionalities are emerging as a promising binder for high-capacity yet large-volume-change silicon anodes with a strong and reversible supramolecular interaction that originates from secondary bonding. However, the supramolecular network solely based on hydrogen bonding is relatively vulnerable to repeated deformation and has an insufficient diffusivity of lithium ions. Herein, reported is a facile but efficient way of incorporating the natural polymers with an ionically conductive crosslinker, which can construct a robust network for silicon anodes. The boronic acid in the crosslinker spontaneously reacts with natural polymers to generate boronic esters at room temperature without any kind of triggers, which gives a strong and dynamic covalent bonding to the supramolecular network. The other component in the crosslinker, polyethylene oxide, contributes to the enhanced ionic conductivity of polymers, leading to outstanding rate performances even at a high mass loading of silicon nanoparticles (>2 mg cm(-2)). The small portion of the proposed crosslinker can modulate the strength of the entire network by balancing the covalent crosslinking and self-healing secondary interaction along with the fast lithium-ion diffusion, thus enabling the extended operation of silicon electrodes.