Interconnected Carbon Nanosheets Derived from Hemp for Ultrafast Supercapacitors with High Energy

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Author list: Wang H, Xu ZW, Kohandehghan A, Li Z, Cui K, Tan XH, Stephenson TJ, King'ondu CK, Holt CMB, Olsen BC, Tak JK, Harfield D, Anyia AO, Mitlin D

Publisher: American Chemical Society

Place: WASHINGTON

Publication year: 2013

Journal: ACS Nano (1936-0851)

Journal acronym: ACS NANO

Volume number: 7

Issue number: 6

Start page: 5131

End page: 5141

Number of pages: 11

ISSN: 1936-0851

eISSN: 1936-086X

Languages: English-Great Britain (EN-GB)

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Abstract

We created unique interconnected partially graphitic carbon nanosheets (10-30 nm in thickness) with high specific surface area (up to 2287 m(2) g(-1)), significant volume fraction of mesoporosity (up to 58%), and good electrical conductivity (211-226 S m(-1)) from hemp bast fiber. The nanosheets are ideally suited for low (down to 0 degrees C) through high (100 degrees C) temperature ionic-liquid-based supercapacitor applications: At 0 degrees C and a current density of 10 A g(-1), the electrode maintains a remarkable capacitance of 106 F g(-1). At 20, 60, and 100 degrees C and an extreme current density of 100 A g(-1), there is excellent capacitance retention (72-92%) with the specific capacitances being 113, 144, and 142 F g(-1), respectively. These characteristics favorably place the materials on a Ragone chart providing among the best power-energy characteristics (on an active mass normalized basis) ever reported for an electrochemical capacitor: At a very high power density of 20 kW kg(-1) and 20, 60, and 100 degrees C, the energy densities are 19, 34, and 40 Wh kg(-1), respectively. Moreover the assembled supercapacitor device yields a maximum energy density of 12 Wh kg(-1), which is higher than that of commercially available supercapacitors. By taking advantage of the complex multilayered structure of a hemp bast fiber precursor, such exquisite carbons were able to be achieved by simple hydrothermal carbonization combined with activation. This novel precursor-synthesis route presents a great potential for facile large-scale production of high-performance carbons for a variety of diverse applications including energy storage.

Keywords

biomass, carbon nanosheets, energy storage, Ionic liquid, Supercapacitor

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