Abstract:
Hydrogel materials have gained significant research attention due to their unique three-dimensional polymeric network structure, which not only retains large volumes of water but also enables the incorporation of various functional guest molecules within their tunable porous architecture. In developing stretchable energy storage devices, hydrogels' high-water content and softness properties make them ideal candidates for flexible electronics, particularly in applications like supercapacitors and rechargeable batteries. In this study, we used a double-network hydrogel where the first network, composed of a copolymer of 2-(acryloyloxy) ethyl trimethyl ammonium chloride and acrylic acid (AAc), forms a rigid, brittle matrix. The second network, made of polyvinyl alcohol (PVA), interpenetrates this structure, transforming it into a soft, ductile matrix with enhanced mechanical strength due to the flexibility of PVA. The electrochemical performance was evaluated by a two-electrode system under various scan rates of cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Here, we have reported the formation of controllable nanochannels in double network hydrogel-based electrolytes, which improved ion transport and boosted supercapacitor performance. The 100 nm (7%) porous double-network hydrogel-based electrolyte achieved an ionic conductivity of 12.6 mS/cm and a specific capacitance of 189.3 mF/cm² at a current density of 0.1 mA/cm². In comparison, the non-porous double-network hydrogel-based electrolyte had an ionic conductivity of 2.5 mS/cm and a specific capacitance of 74.7 mF/cm². Additionally, the pores generated by 300 nm (7%) and 500 nm (5%) porous DN hydrogel electrolyte displayed a specific capacitance of 183.3 mF/cm² and 159.0 mF/cm², respectively, at a current density of 0.1 mA/cm². Whereas filter paper as a separator instead of 100 nm (7%) porous DN hydrogel electrolyte has a specific capacitance of 81.77 mF/cm² at a current density of 0.1 mA/cm² and ionic conductivity of 0.89 mS/cm. These findings highlighted that nanochannel formation within double-network hydrogels significantly enhances capacitive performance and positions them as promising materials for supercapacitor applications.
Keywords: Double network hydrogel, electrolyte, nanochannel, silica nanoparticle, supercapacitor