Hydrogen Bonding-Reinforced Hydrogel Electrolyte for Flexible, Robust, and All-in-One Supercapacitor with Excellent Low-Temperature Tolerance

Flexible supercapacitors are promising energy storage devices for emerging wearable electronics. However, due to the poor mechanical strength, complicated device manufacturing process, and unsatisfactory low-temperature tolerance, their overall performance for practical applications is hindered. Herein, we report a hydrogen bonding-reinforced, dual-crosslinked poly(vinyl alcohol), acrylic acid, and H 2 SO 4 (PVA-AA-S) hydrogel electrolyte for all-in-one flexible supercapacitors. The PVA-AA-S hydrogel demonstrates excellent compressive/tensile properties and high ionic conductivity. It tolerates compressive stress of 0.53 MPa and is stretchable up to 500%. The hydrogel-based all-in-one supercapacitor shows promising electrochemical performance under various harsh conditions. The device energy density and power density reach up to 14.2 μWh cm –2 and 0.94 mW cm –2, respectively. Furthermore, it retains nearly 80% capacitance after being stored at −35 °C for 23 days. The excellent performance of the hydrogel electrolyte originates from its abundant strong hydrogen bonding between polymer chains and water molecules.