Fiber-reinforced monolithic supercapacitors with interdigitated interfaces†
Supercapacitors will serve as essential components of distributed energy storage networks and structural power devices in many emerging technologies. Current supercapacitors are engineered, however, using ‘sandwich’ architecture that undermines their physical integrity under stress and at high temperatures due to delamination. It also limits the successful integration of charge storage and load-bearing functions needed to increase the net stored charge. Bridging the requirement for high mechanical and thermal integrity of supercapacitors as structural energy storage elements is still challenging. Addressing these long-standing problems, we demonstrate here a process of developing structural monolithic supercapacitors (MSCs) where all the components are interdigitated by strong nanofibers synthesized from polyaramid fiber (Kevlar® 49). The monolithic design is realized using a one-step stratified assembly of a graphene–polyaramid nanofiber (PANF) and boron nitride–PANF nanocomposites acting as electrodes and separator, respectively. MSCs demonstrate an optimum combination of mechanical flexibility and robustness, distributing the stress at interfaces and preventing delamination. Also, combination of thermal stability with fast heat dissipation enables MSCs to operate at high temperature (∼100 °C). Hence, we envisage that MSCs could open prospects for their utilization as a structural energy and power system.