Multidentate Coordination Chemistry Enables Adaptive Ionic Cross-Linking of Conductive Binder for Reversible Silicon Anodes.

Conductive binders present a potential solution to the volumetric instability of silicon anodes; yet their low molecular weight and limited mechanical robustness demand reversible interactions to establish stable, adaptive cross-linked networks. Building on this concept, coordination bonds with their reversible dynamics serve as a key strategy for constructing such adaptive polymer networks, though their structure-property relationships remain elusive. This work seeks to unveil the key mechanism by which ionic coordination structures govern the performance of conductive binders in silicon anodes and to establish a universal, coordination-based design strategy for ion-cross-linked binders. It is revealed that the multidentate bridge coordination between carboxylate groups and Fe3+ simultaneously reinforces mechanical strength and maintains uniform polymer-silicon interactions, achieving the balance essential for stable cycling. Benefiting from such coordination structure, the Fe3+-coordinated conductive binder well accommodates silicon's volume fluctuations, enabling reversible electrode deformation. The enhanced structural adaptability also spatially confines the growth of the solid-electrolyte interphase, preventing its thickening and the dilution of the LiF-rich phase by undesirable species. As a result, the rational binder design translates into a significant boost in the electrochemical performance of the silicon electrodes. Rooted in coordination chemistry, this work offers theoretical insights into the design of adaptive networks for high-volume-changing battery materials.