Roll-to-Roll Production of Spray Coated N-doped Carbon Nanotube Electrodes for Supercapacitors

Although nanocarbons are being increasingly used in energy storage, there has been a lack of inexpensive, continuous and scalable synthesis methods. Here we present a scalable roll-to-roll spray coating process for synthesizing supercapacitors from randomly oriented multi-walled carbon nanotubes electrodes on Al foils, which yield high power and energy densities ($\sim$ 700 mW/cm$^{3}$ and 1 mWh/cm$^{3})$ and cycle stability (\textgreater 10000 cycles) on par with Li-ion thin film batteries. Our cost analysis shows that the R2R spray coating process can produce supercapacitors with 10 times the energy density of conventional activated carbon devices at $\sim$ 17{\%} lower cost.