Ultra-flexible anti-freezing cellulose conductive hydrogel for energy storage and self-powered sensors

Integrating superior flexibility, conductivity, energy harvesting and broad working temperatures into cellulose hydrogel for deformable energy storage and self-powered sensors has become urgent. Herein, an ultra-flexible anti-freezing conductive versatile hydrogel is developed via synchronously regulating polyvinyl alcohol (PVA) with cellulose nanocrystals (CNCs) and covalent organic frameworks (COFs) to form a multiple hydrogen-bonded ordered network under phytic acid (PA) crosslinking synergy. Introducing COFs into hydrogel network provides continuous protons transport channel while PA generates protons and permanently secures the hierarchical structure of hydrogel, and thus endowing the hydrogel with exceptional proton conductivity (2.46 S/m), ultra-flexibility (tensile strain of 725 %), and outstanding antifreeze conductivity (withstand −40 °C). With these attributes, the hydrogel assembled supercapacitor exhibits stable energy storage capacity (84.7 mF/cm²) and bending resilience (endure bending angles of 180°), whereas the hydrogel-based triboelectric nanogenerator (TENG) presents excellent electrical output performance. Moreover, the designed hydrogel strain sensor demonstrates high sensing sensitivity, enabling stable monitoring of various joint movements and subtle facial expressions. Overall, this study presents a promising approach for designing biomass-based versatile hydrogels with outstanding mechanical performance and energy harvesting and storage functionality for emerging applications in self-powered flexible sensors.