“All-in-Gel” design for supercapacitors towards solid-state energy devices with thermal and mechanical compliance

Abstract

Ionogels are semi-solid, ion conductive and mechanically compliant materials that hold promise for flexible, shape-conformable and all-solid-state energy storage devices. However, identifying facile routes for manufacturing ionogels into devices with highly resilient electrode/electrolyte interfaces remains a challenge. Here we present a novel all-in-gel supercapacitor consisting of an ionogel composite electrolyte and bucky gel electrodes processed using a one-step method. Compared with the mechanical properties and ionic conductivities of pure ionogels, our composite ionogels offer enhanced self-recovery (retaining 78% of mechanical robustness after 300 cycles at 60% strain) and a high ionic conductivity of 8.7 mS cm⁻¹, which is attributed to the robust amorphous polymer phase that enables facile permeation of ionic liquids, facilitating effective diffusion of charge carriers. We show that development of a supercapacitor with these gel electrodes and electrolytes significantly improves the interfacial contact between electrodes and electrolyte, yielding an area specific capacitance of 43 mF cm⁻² at a current density of 1.0 mA cm⁻². Additionally, through this all-in-gel design a supercapacitor can achieve a capacitance between 22–81 mF cm⁻² over a wide operating temperature range of −40 °C to 100 °C at a current density of 0.2 mA cm⁻².