Mechanically Robust All-Hydrogel Supercapacitor Having Seamless Interfaces Among Components by Rapid Phase Transition of Physical Gels

In an integrated flexible electronic device, the interface between the components not only degrades the electrical performance but also makes it mechanically vulnerable. Therefore, interface engineering is important to ensure device stability. We propose a design strategy for the integration of flexible supercapacitors that maximizes the structural integrity between all-components based on an agarose hydrogel exhibiting rapid phase transition properties. The agarose/activated carbon electrode exhibited rapid gelation at room temperature to form a seamless interface with the carbon cloth current collector. Subsequently, the agarose electrolyte was introduced directly into the electrode in the liquid phase for a seamless integration between the electrode and electrolyte. As a result, the seamless interface improved both the electrochemical performance and mechanical strength, compared to that of the conventional sandwich-type supercapacitor. Considering that flexible electronic devices are subjected to repeated mechanical deformations, the device fabrication strategy using phase change materials proved to be very effective.