Freestanding Ion Gels for Flexible, Printed, Multifunctional Microsupercapacitors.

Freestanding ion gels (FIGs) provide unique opportunities for scalable, low-cost fabrication of flexible microsupercapacitors (MSCs). While conventional MSCs employ a distinct electrolyte and substrate, FIGs perform both functions, offering new possibilities for device integration and multifunctionality while maintaining high performance. Here, a capillarity-driven printing method is demonstrated to manufacture high-precision graphene electrodes on FIGs for MSCs. This method achieves excellent self-alignment and resolution (width: 50 μm, device footprint: <1 mm2), 100% fabrication yield (48/48 devices), and is readily generalized to alternative electrode materials including multi-walled carbon nanotubes (MWCNTs). The devices demonstrate good performance, including high specific capacitance (graphene: 0.600 mF cm-2; MWCNT: 6.64 mF cm-2) and excellent stability against bending, folding, and electrical cycling. Moreover, this strategy offers unique opportunities for device design and integration, including a bifacial electrode structure with enhanced capacitance (graphene: 0.673 mF cm-2; MWCNT: 7.53 mF cm-2) and improved rate performance, print-and-place versatility for integration on diverse substrates, and multifunctionality for light emission and transistor gating. These compelling results demonstrate the potential of FIGs for scalable, low-cost fabrication of flexible, printed, and multifunctional energy storage devices.