Polyhydroxy Hydrogel Electrolyte with In Situ Tuned Interface Chemistry for Ultra-Stable Biosensing-Compatible Zinc Batteries

Aqueous zinc batteries (ZBs) represent a promising sustainable and safe energy storage technology, yet their widespread adoption is impeded by persistent interfacial instabilities at Zn anodes. This study reports a polyhydroxy hydrogel electrolyte (PASHE) with in situ regulated interface chemistry suitable for biosensing compatible ZBs. Benefiting from the well-integrated interface via in situ strategy, the hydroxyl-rich L-sorbose in PASHE establishes kinetically favorable Zn²⁺ transport pathways and regulates interfacial ion-adsorption hierarchies, synergistically homogenizing ion distribution and promoting preferential crystallographic orientation. Furthermore, PASHE constructs a low water-activity microenvironment via interfacial preferential adsorption, oxygen-rich solid electrolyte interphase evolution, and Zn²⁺ solvation sheath reconstruction. These effects enable Zn (002)-textured electrodeposition and inhibitory side reactions, achieving dendrite-free Zn plating/stripping with exceptional stability (3300 h in Zn//Zn cells) and near-perfect reversibility (average coulombic efficiency of 99.6% over 1200 cycles in Zn//Cu cells). This strategy delivers unprecedented cyclability in flexible Zn//I₂ batteries (94.9% retention after 9000 cycles) and Zn-ion hybrid capacitors (98.0% after 43,000 cycles). Notably, we demonstrate an integrated biosensing platform that couples PASHE-based biosensor with cascaded Zn//I₂ batteries, realizing real-time monitoring of physiological signals and biomechanical motions. This work proposes dual strategies of in situ approach and functional additive to design hydrogel electrolytes, bridging high-performance ZBs with next-generation biosensing technologies.