Scalable spray-coated graphene-based electrodes for high-power electrochemical double-layer capacitors operating over a wide range of temperature

Abstract

Advancements in electrochemical double-layer capacitor (EDLC) technology require the concomitant use of novel efficient electrode materials and viable electrode manufacturing methods. Cost-effectiveness, scalability and sustainability are key-drivers for fulfilling product development chain accepted by worldwide legislations. Herein, we report a scalable and sprayable "green " electrode material-based ink based on activated carbon and single-/fewlayer graphene (SLG/FLG) flakes. We show that, contrary to commercial reduced graphene oxide, defect-free and flat SLG/FLG flakes reduce the friction of ions over the electrode films, while spray coating deposition of our ink maximises the electrolyte accessibility to the electrode surface area. Sprayed SLG/FLG flakes-based EDLCs display superior rate capability performance (e.g. , specific energies of 31.5, 23.7 and 12.5 Wh kg − 1 at specific powers of 150, 7500 and 30000 W kg − 1 , respectively) compared to both SLG/FLG flakes-free devices and commercial-like EDLCs produced by slurry-coating method. The use of SLG/FLG flakes enables our sprayed EDLCs to operate in a wide range of temperature (− 40/ + 100°C) compatible with ionic liquid/organic solvent-based electrolytes, overcoming the specific power limits of AC-based EDLCs. A prototype EDLCs stack consisting of multiple large-area EDLCs, each one displaying a capacitance of 25 F, demonstrates the industrial potential of our technology.

Graphene-Based Electrodes in a Vanadium Redox Flow Battery Produced by Rapid Low-Pressure Combined Gas Plasma Treatments

“…212 , 213 The thorough characterization of the WJM-produced graphene flakes is reported in the Supporting Information ( Figures S9 and S10 ). Importantly, as shown in previous works, 209 WJM-produced SLG/FLG flakes are pristine graphene flakes that do not exhibit basal plane defects, as also evidenced by Raman analysis (see Figure S10b ). Consequently, they can guarantee superior electrical properties compared to other commercialized graphene derivatives, including graphene oxide and reduced graphene oxide.…”

“…In order to maintain an industrial approach for the electrode fabrication, single-/few-layer graphene (SLG/FLG) flakes were produced through scalable wet-jet milling (WJM) exfoliation of graphite in N -methyl-2-pyrrolidone dispersion (see details in the Supporting Information ). 207 − 209 Briefly, the WJM exfoliation process makes use of a high pressure (180–250 MPa) to transform a graphite dispersion in two jet streams, which then recombine in a small nozzle (diameter between 0.3 and 0.1 nm), where the generated shear forces cause the exfoliation of the graphite in single-/few-layer graphene flakes. 207 , 208 , 210 By applying three consecutive WJM passes on nozzles with diameters of 0.3, 0.15, and 0.1 nm, respectively, our WJM protocols lead to a highly concentrated dispersion (∼10 g L –1 ) of graphene flakes with an exfoliation yield of ∼100% and a graphene production rate of ∼2 g min –1 .…”

Low-Temperature Graphene-Based Paste for Large-Area Carbon Perovskite Solar Cells

“… 65 , 66 This exfoliation method provides a production rate of graphene flakes of ∼0.4 g min –1 (on a single WJM apparatus) and an exfoliation yield of 100%. 65 , 66 These features make the WJM-produced graphene flakes affordable for massive applications (contrary to other highly conductive graphitic materials, e.g., carbon nanotubes). 67 Differently from other chemical exfoliation and chemical/thermal reduction methods used for the production of graphene derivatives (e.g., reduced graphene oxides), 68 , 69 the WJM exfoliation process preserves the chemical purity of the starting graphite.…”

Hybrid Organic/Inorganic Photocathodes Based on WS2 Flakes as Hole Transporting Layer Material

“…[ 86–88 ] Furthermore, 2D TMDs can be prepared in form of liquid dispersions by means of scalable liquid‐phase exfoliation (LPE) methods, [ 89–93 ] such as wet‐jet milling exfoliation. [ 94–96 ] This possibility enables large‐scale and cost‐effective solution processing, [ 97,98 ] through spray coating, [ 99 ] vacuum filtration, [ 90 ] ink‐jet printing, [ 100,101 ] and drop‐casting methods. [ 102 ] Finally, 2D TMDs have been widely established as ECs for the HER, [ 9,91,103,104 ] which means that they can stably operate under cathodic HER operation.…”