Highly Flexible and Stable Solid-State Supercapacitors Based on a Homogeneous Thin Ion Gel Polymer Electrolyte Using a Poly(dimethylsiloxane) Stamp

Abstract

To achieve both high structural integrity and excellent ion transport, designing ion gel polymer electrolytes (IGPEs) composed of an ionic conducting phase and a mechanical supporting polymer matrix is one of the promising material strategies for the development of next-generation all-solid-state energy storage systems. Herein, we prepared an IGPE thin film, in which an ion-diffusing phase containing ionic liquids and lithium salts was bicontinuously intertwined with a cross-linked epoxy phase, using a silicon elastomer-based stamping method, thus producing a homogeneous IGPE-based thin film with low surface roughness (R-rms = 0.5 nm). Following the optimization of the IGPE thin film in terms of the concentrations of ionic constituents, the film thickness, and various process parameters, the IGPE itself showed a high ionic conductivity of 0.23 mS/cm with a low activation energy for lithium-ion transport, as well as the high capacitance of approximately 10 mu F/cm(2) based on the metal-insulator-metal configuration. Furthermore, an all-solid-state supercapacitor containing two IGPE coating-activated carbon electrodes produced using our poly(dimethylsiloxane) (PDMS) stamping method exhibited high energy and power densities (44 W h/kg at 875 W/kg and 28 kW/kg at 3 W h/kg). It was also found that this supercapacitor showed a dramatic reduction (more than 50%) of the current-resistance (IR) drop, which is an indicator of low interface resistance, while maintaining the initial electrochemical performance even after severe mechanical deformation such as bending or rolling. Therefore, all these results support the fact that our developed PDMS stamping method enables the rendering of a high-performance ion gel polymer thin-film-based electrolyte with acceptable stability and mechanical flexibility for all-solid-state wearable energy storage devices.