Advances in nanomaterials hold the key for resolving many formidable energy challenges in the 21st century. Although many revolutionary technologies have been developed for a clean, secure and sustainable energy future, economically viable devices with sufficient high energy and power densities for automobiles, portable electronics, and other power tools are still lacking. Supercapacitors (SCs) are poised to address our current energy storage and delivery needs by combining the high power, rapid switching, and exceptional cycle life of a capacitor with the high energy density of a battery. While activated carbon and carbon nanotubes (CNTs) are extensively used as supercapacitor electrodes due to their superior properties, their low specific capacitance (100-120 F/g) fundamentally limits the energy density of SCs. Defects in nanomaterials, which are often dismissed as material performance limiters, can enhance electrochemical properties and are central for improving the current SC performance. Here, we show that the structural, compositional, and morphological defects in carbon nanomaterials can improve the performance from 100-120 F/g to beyond 650-800 F/g. For instance, while helically coiled CNTs improve the double layer capacitance, N-doped CNTs exhibit an enhanced pseudo-capacitance and vacancies in graphene alter the quantum capacitance. Accordingly, we demonstrate that by controlling type, nature, and bonding environment of defects in carbon nanomaterials, one can efficiently tune the double-layer (via changes in surface area), pseudo (by inducing new redox activity) and quantum (through altering the density of states) capacitance of SCs. Most importantly, we developed scalable roll-to-roll processes for producing nanocarbon-based SCs employing various Al current collectors (ranging from simple kitchen Al foil to industry-standard Al cathode) for high energy and power density SCs at a low cost < $1 Wh/Kg. This work is supported by NSF-CMMI scalable nanomanufacturing SNM # 1246800 award, and is a result of strong collaboration with an industrial partner Cornell Dubilier, Liberty, SC. Co-authors include the team members of Profs. P. Bandaru (UCSD), Mark Roberts (Clemson) and R. Podila (Clemson).
Clemson University, Clemson Nanomaterials Center
You must be logged in and own this session in order to