Interfacial Si–O–Zn Coordination in Chitosan Hydrogel Electrolytes Regulating (002)-Oriented Zn Deposition for Flexible Energy Storage and Sensing

Sustainable wearable electronics demand flexible energy-storage and sensing devices made by greener, low-impact routes. Aqueous zinc-based hydrogel electrolytes are attractive here, but their use is limited by uncontrolled zinc dendrite growth and by the difficulty of combining fast Zn2+ transport with controlled interfacial deposition. Most hydrogels resist dendrites only through passive physical confinement, without actively governing interfacial zinc deposition. Herein, using chitosan, a renewable polysaccharide obtained from chitin-rich seafood waste, we construct an interfacial Si–O–Zn coordination motif within a hydrogel electrolyte through a mild, all-aqueous, one-step in situ polymerization that requires no separate activation step. Chitosan and acrylamide form the matrix, zinc trifluoromethanesulfonate (Zn(OTf)2) is the zinc source, and nanosilicon acts as a functional filler. Chitosan bridges the organic and inorganic domains through its -NH2/-OH groups, while free Zn2+ ions coordinate with surface silanols to form interfacial Si–O–Zn coordination interactions. The optimized CAA-6-Si(3:1) electrolyte delivers a high ionic conductivity (36.04 ± 1.71 mS cm–1), a wide electrochemical stability window (2.56 V), and a Zn2+ transference number of 0.583. Spectroscopic and structural analyses reveal that the interfacial Si–O–Zn sites actively steer Zn2+ toward the low-energy (002) plane, suppressing dendrites rather than merely blocking them; accordingly, Zn || Zn symmetric cells cycle stably for 1820 h at 2 mA cm–2 and 535 h at 5 mA cm–2. The same electrolyte integrates readily into multiple flexible devices: zinc-ion hybrid capacitors retain 90.4% capacity after 50,000 cycles at 10 A g–1, with stable performance under bending, and strain sensors (gauge factor = 1.54) reliably monitor physiological signals. By coupling interfacial coordination chemistry to zinc deposition, this chitosan hydrogel electrolyte combines fast Zn2+ transport with (002)-oriented, dendrite-suppressed plating. Made from a renewable feedstock through a mild, low-impact process, it offers a sustainable route to flexible energy-storage and sensing devices.