Influence of Substrate in Roll-to-roll Coated Nanographite Electrodes for Metal-free Supercapacitors

Abstract

Due to the high electric conductivity and large surface area of nanographites, such as graphene and graphite nanoplatlets, these materials have gained a large interest for use in energy storage devices. However, due to the thin flake geometry, the viscosity of aqueous suspensions containing these materials is high even at low solids contents. This together with the use of high viscosity bio-based binders makes it challenging to coat in a roll-to-roll process with sufficient coating thickness. Electrode materials for commercial energy storage devices are often suspended by organic solvents at high solids contents and coated onto metal foils used as current-collectors. Another interesting approach is to coat the electrode onto the separator, to enable large-scale production of flat cell stacks. Here, we demonstrate an alternative, water-based approach that utilize slot-die coating to coat aqueous nanographite suspension with nanocellulose binder onto the paper separator, and onto the current collector as reference, in aqueous metal-free supercapacitors. The results show that the difference in device equivalent series resistance (ESR) due to interfacial resistance between electrode and current collector was much lower than expected and thus similar or lower compared to other studies with a aqueous supercapacitors. This indicates that electrode coated paper separator substrates could be a promising approach and a possible route for manufacturing of low-cost, environmentally friendly and metal-free energy storage devices.

High-Throughput Processing of Nanographite–Nanocellulose-Based Electrodes for Flexible Energy Devices

“…A detailed analysis of the devices’ performance at various charge densities and scan rates is discussed in Blomquist . The performance of these SCs is comparable to similar devices demonstrated on a batch scale by some of the authors of this work, thus showing that slot-die coating of nanographite–nanocellulose suspensions could be used to produce low-cost environmentally friendly conductive electrodes on a large scale. The influence of CMC-containing electrodes on the SC performance will be addressed in future studies.…”

Material properties and structure of natural graphite sheet

“…Natural graphite sheet (NGS) is a compressible, porous, electrically and thermally conductive material that has been used primarily to make sealing gaskets because of its ability to conform to rough surfaces, withstand high temperatures, and resist corrosive fluids. Presently, it is used—or considered to be used—in numerous applications, including bipolar plates in fuel cells and flow batteries for its electrical conductivity and chemical stability 1 , 2 , 3 , supercapacitors for its corrosion resistance 4 , 5 , adsorption cooling systems for its high thermal diffusivity 6 , heat spreaders for its high in-plane thermal conductivity 7 , 8 , heat exchangers for its thermal conductivity and corrosion resistance 9 , and heat sinks for its thermal conductivity, low weight, and ease of forming into complex shapes 10 , 11 . Multiple other names are used in the literature to refer to NGS, such as compressed exfoliated natural graphite (CENG), graphite foil, or flexible graphite.…”

Recent advances in energy storage with graphene oxide for supercapacitor technology

“…141 Additionally, cyclic voltammetry (CV) and galvanostatic charge-discharge measurements are employed to evaluate the capacitive behavior, including specic capacitance, energy density, and power density. [142][143][144][145] To enhance the SC performance of GO, various strategies are employed. Reduction of GO to produce reduced graphene oxide (rGO) can improve the electrical conductivity and electrochemical activity.…”