Intermolecular Cross‐Linking Reinforces Polymer Binders for Durable Alloy‐Type Anode Materials of Sodium‐Ion Batteries

Abstract Sodium‐ion batteries show promising potential for large‐scale energy storage. However, the large size and heavy mass of Na + always results in huge volume change and inferior electrochemical stability, especially in alloy‐type anode materials. Here, molecular engineering of the polymer binders, i.e., cross‐linking of poly(acrylic acid) with glycerin (PAA‐GLY), reinforces the mechanical properties, eliminates the active protons of PAA, and benefits electrolyte diffusion, thereby remarkably improving electrochemical performance. Using µ‐Sn as an example, the cycle life at 2 A g −1 is extended from ≈26 cycles of PAA to ≈2000 cycles of PAA‐GLY. Meanwhile, the initial Coulombic efficiency is promoted to 90.3%, allowing the fabrication step of electrode presodiation for full cells to be eliminated. Thus, the full cells run 300 cycles at 2 A g −1 . In addition, the binder allows the thick electrode to exhibit an areal capacity of 6.8 mAh cm −2 . This binder is also applied for µ‐Bi and µ‐Sb. The simple operation, remarkable improvement, and wide applications indicate the promising prospects of this strategy for advanced electrodes in sodium ion batteries.