Chapter2 1 2. Fabric-Integrated, Ionic Liquid-Based Supercapacitor as a Tunable and Flexible Power Source

Abstract With the introduction of flexible and wearable electronic technologies such as displays, antenna’s, etc., there has been an increased need for integrable, easily scalable, and safe electric power sources. Advances in flexible lithium-ion batteries have been recently reported, however they may still suffer from potential thermal runaways. In this chapter we review the progress in the topic of wearable energy storage devices. These devices have taken the form of both sheets and fibers entirely made of active material. We also discuss the advantages and drawbacks of each forms. Finally, we present our own work revealing a simplistic way to integrate working carbon electrode materials into suitable textile and to functionalize the obtained flexible structure with ionic liquid thus creating fabric supercapacitors. These devices can then be connected easily in series (9 V) or in parallel (high current), depending on the current or voltage requirements. The area of the electrodes can also be tuned to sustain higher capacitances. We report an energy density of 48 Wh/kg for a functional device at 3 V working window, which reveals no losses in energy density after 10,000 bending cycles.