Small Things Make a Big Difference: the Small-molecule Cross-linker of Robust Water-soluble Network Binders for Stable Si Anodes

Silicon(Si) with high theoretical capacity has attracted tremendous attention as the next-generation anode material for Li-ion batteries, but the huge expansion during cycling restricts its practical application. Designing a low-cost, accessible robust network binder is a facile and effective approach to suppress the volume change effect and achieve the commercial application of Si anodes. Different previous studies focused on the network binder macromolecule main chain, this manuscript pays attention to the study of small-molecule cross-linker. Herein, cross-linked network binders using alginate acid and two kinds of cross-linkers, i.e., D-sorbitol and isosorbide(Alg-DS and Alg-IS binders) are synthesized. It was found that not only the chemical structure of the cross-linker but also the physicochemical property, such as melting point affect greatly the mechanical properties of the network binder. As a result, the Si anode with an Alg-DS binder dried below the melting point of DS shows the best cycling stability with a high capacity of 2249.8 mA·h/g and a retention rate as high as 95.9% after 100 cycles. This study gives a new view to design robust network binders for stable Si anodes.