Humidity-modulated properties of hydrogel polymer electrolytes for flexible supercapacitors

Hydrogel polymer electrolytes (HPEs) are essential components in building flexible solid-state supercapacitors, which promising power sources for future and wearable electronics. HPEs reported so far have shown a wide range of properties with various compositions. In this paper, we demonstrate that relative humidity (RH) significantly influences the electrochemical mechanical HPEs, turn, determines output supercapacitors assembled such HPEs. Using polyvinyl alcohol phosphoric acid hydrogel (PVA-H3PO4) as model HPE, showed water content PVA-H3PO4 increases RH can reach equilibrium at each level. By using atomic force microscope, impedance spectroscopy, cyclic voltammetry, found stiffness, ionic conductivity, interfacial capacitance prepared precisely controlled levels vary orders magnitude. As result, flexibility energy performance based all be modulated by RH. We believe result provides new approach to optimizing supercapacitor applications.