A Hydrogel Electrolyte\ntoward a Flexible Zinc-Ion\nBattery and Multifunctional Health Monitoring Electronics

Abstract

The compact design of an environmentally adaptive battery\nand effectors\nforms the foundation for wearable electronics capable of time-resolved,\nlong-term signal monitoring. Herein, we present a one-body strategy\nthat utilizes a hydrogel as the ionic conductive medium for both flexible\naqueous zinc-ion batteries and wearable strain sensors. The poly(vinyl\nalcohol) hydrogel network incorporates nano-SiO₂ and cellulose\nnanofibers (referred to as PSC) in an ethylene glycol/water mixed\nsolvent, balancing the mechanical properties (tensile strength of\n6 MPa) and ionic diffusivity at −20 °C (2 orders of magnitude\nhigher than 2 M ZnCl₂ electrolyte). Meanwhile, cathode\nlattice breathing during the solvated Zn²⁺ intercalation\nand dendritic Zn protrusion at the anode interface are mitigated.\nBesides the robust cyclability of the Zn∥PSC∥V₂O₅ prototype within a wide temperature range (from −20\n to 80 °C), this microdevice seamlessly integrates a zinc-ion\nbattery with a strain sensor, enabling precise monitoring of the muscle\nresponse during dynamic body movement. By employing transmission-mode <i>operando</i> XRD, the self-powered sensor accurately documents\nthe real-time phasic evolution of the layered cathode and synchronized\nstrain change induced by Zn deposition, which presents a feasible\nsolution of health monitoring by the miniaturized electronics.