From Physical Cross-Linking to Tailored Phosphorylation: Unlocking High-Performance and Biocompatible Xanthan-Konjac Hydrogels for Zinc-Ion Batteries.

Abstract

Natural polymer-based hydrogel electrolytes, though biocompatible and cost-effective, often exhibit poor mechanical strength and ionic conductivity, limiting their use in high-performance energy storage. Phos-XK, a novel hydrogel electrolyte derived from xanthan gum (XG) and konjac glucomannan (KGM), has been developed via physical cross-linking and targeted phosphorylation. Specifically, physical cross-linking forms a robust 3D network that provides a stable structural foundation. Building on this, the phosphorylation process introduces phosphate monoesters (MPE) and diesters (DPE) in a precisely controlled ratio. MPE groups enhance ionic conductivity by facilitating Zn²⁺ desolvation and ion migration, while DPE strengthens mechanical integrity through enhanced cross-linking. These distinct roles of MPE and DPE are confirmed through both theoretical calculations and experimental results. Optimizing the phosphorylation ratio achieves a balance between mechanical strength (2.524 MPa) and ionic conductivity (20.72 mS cm^-1), resulting in remarkable electrochemical performance, including an extended cycle life exceeding 3000 h and a high Coulombic efficiency of 99.45% in Zn//Cu batteries. Moreover, Phos-XK is biocompatible and biodegradable, ideal for sustainable energy storage. This work highlights the potential of bio-based materials to overcome the limitations of traditional hydrogel electrolytes and stresses the importance of molecular engineering in achieving high-performance, eco-friendly energy storage.