Replacing Metals: Carbon Fibers Derived from a Poly(Ionic Liquid) as a Current Collector

New technologies for energy storage are crucial to increasing the functionality of industrial green energy. There is a race to develop cutting edge batteries, supercapacitors, and fuel cells. The demands of energy storage devices necessitates that all the components be optimized, effective and cheap. Out of all the components in batteries and supercapacitors, current collectors have received less attention. In supercapacitors, the demanding requirements for a current collector are higher than that of batteries, since its faster rate capability means that a high conductivity is critical. Thus, supercapacitors can be considered a benchmark for performance of current collectors in batteries. The golden standard is platinum, albeit its high cost and weight hinders the wide-spread application of supercapacitors.

In this context we developed a new current collector, by electrospinning poly(ionic liquid)s (PILs), crosslinking and carbonizing. PILs are an emerging class of polymers that feature an ionic liquid species in each monomer repeating unit, combining the advantages of polymers and ionic liquids. Electrospinning is a technique to produce continuous fibers with diameters of a few micrometers down to tenths of nanometers. Electrospun fibers have the advantages of being stand-alone, and having a high surface area, continuity of the material, and low percolation threshold. The spun fibers were crosslinked to maintain their structure and carbonized to 950°C to increase their conductivity. Up to now, the conductivity of amorphous carbons was too low to replace the current collector in supercapacitors. However, these PILs fibers show performance that matches that of platinum, and works in both aqueous and organic electrolytes. Their high macroporosity makes them lightweight, at least two order of magnitude lower than a typical platinum collector. The high conductivity, low weight, and scalability of the production method establish the potential these carbon fibers have in replacing platinum as a current collector in supercapacitors.