Enhanced Stretchability and Resilience of PVA–Sucrose Composite Hydrogel and Its Application to All-In-One Supercapacitors

Although the addition of polysaccharides such as agarose increases the mechanical strength of the poly(vinyl alcohol) (PVA) hydrogel crosslinked with borax, the stretchability and resilience of the hydrogel decrease because of the high entanglement of polymer strands. To address these adverse effects of polysaccharides, herein, we propose the use of a monomeric saccharide, sucrose. Compared with the conventional PVA–borax–agarose (PBA) hydrogel, the PVA–borax–sucrose (PBS) hydrogel exhibits considerably enhanced tensile elongation and recoverability while maintaining comparable mechanical strength because of the less restricted movement of polymer strands owing to the monomeric characteristic of sucrose bonded to them. The addition of 1 wt % sucrose allows the hydrogel to elongate up to 150% and fully recover after the removal of the pulling force; these results are considerably superior to the 87.5% elongation and 85.7% recoverability of the PBA hydrogel. The PBS hydrogel is also used as a base substrate for the electrode and electrolyte layers of a supercapacitor to obtain stretchable all-in-one energy storage devices. To impart electrical conductivity and capacitive properties, indium tin oxide nanoparticles (NPs) are incorporated into the hydrogel. We introduce the pre-hydroxylation of the NP surface, which enables the NPs to chemically bind to the polymer network, to prevent the release of the NPs from the hydrogel. The fabricated supercapacitor exhibits an areal capacitance of 7.4 μF/cm2 at a scan rate of 50 mV/s, with a capacitance retention of 79.1% over 5000 galvanostatic charge–discharge cycles.