Thin film nanocarbon composites for supercapacitor applications

Porous nanocarbon and carbon-multi walled carbon nanotubes (MWCNT)-nanocomposite films are processed on stainless steel collectors for high performance supercapacitor applications. The processing of these films starts with a solution-based fabrication of porous polyvinylidene fluoride (PVDF) or porous PVDF-MWCNT-nanocomposite films on the collector, followed by pyrolysis under nitrogen atmosphere at the moderate temperature of 550 °C. The resulting films replicate the porous structure of the parent films yielding a range of hierarchical pore sizes. The surface properties and chemistry of the films are tuned via surface modification with single walled CNT (SWCNT) and Ni(OH)2-Nanoparticles using a novel method that is based on reactions taking place at the interface between the substrate and a Leidenfrost layer. The electrochemical properties of the different film structures are characterized in 1 M KOH aqueous electrolyte and in ethylene glycol based electrolytes. Single electrodes (three-electrode setup) with outstanding specific capacitance values of up to 689 F g−1 (597 mF cm−2) are obtained. Supercapacitors in ethylene glycol based electrolytes deliver energy densities of up to 10.2 Wh kg−1 and power densities of up to 5 kW kg−1 with a potential working range of 2 V. In all cases, long-term charge-discharge stability is demonstrated.

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