Tough Electrodes: Carbon Nanotube Fibers as the Ultimate Current Collectors/Active Material for Energy Management Devices

The assembly of nanocarbons (carbon nanotubes, graphene) into macroscopic architectures has led to a new type of mesoporous graphitic materials with an exceptional combination of high surface area, electrical conductivity,and toughness. With a porosity close to that of an activated carbon and tensile properties in the high-performance range, macroscopic carbon nanotube (CNT) fibers are ideal current collectors for lightweight robust devices, such as supercapacitors, batteries, biofuel cells, solar cells,and energy scavengers. In this Perspective, we discuss the basic properties of CNT ensembles compared to other carbon electrodes and present examples of their operation as part of electrochemical and electronic devices. We show the possibility to assemble the nanocarbon building blocks hierarchically and combine them with additional phases (e.g., metal oxides, semiconductors,and polymer electrolytes) to produce large-surface electronic junctions and interfaces for electrochemical energy storage. The challenges ahead include understanding better the interactions at the interface between nanocarbon electrode and active phase and how they can be chemically tailored to exploit more efficiently interfacial charge transfer and accumulation processes.