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Ultrafast hydrothermal assembly of nanocarbon microfibers in near-critical water for 3D microsupercapacitors
- Zhai, Shengli, Wei, Li, Karahan, H. Enis, Wang, Yanqing, Wang, Chaojun, Montoya, Alejandro, Shao, Qian, Wang, Xin, Chen, Yuan
- Carbon 2018 v.132 pp. 698-708
- capacitance, carbon, carbon nanotubes, electric power, energy, energy conservation, energy density, graphene oxide, hot water treatment, temperature
- Translating the advantages of carbon nanomaterials into macroscopic energy storage devices is challenging because the desirable nanoscale properties often disappear during assembly processes. Here we describe a new nonequilibrium subcritical hydrothermal method capable of independently manipulating the temperature and pressure to create unique assembly conditions crossing the commonly used liquid-vapor boundary. Highly conductive and dense-packed yet ion-accessible nanocarbon microfibers can be obtained from graphene oxide sheets, single-walled carbon nanotubes, and a nitrogen-doping crosslinker under 20 min of hydrothermal assembly, 80% energy saving compared to standard hydrothermal methods, and one of the shortest time in the field of hydrothermal processing of carbon nanomaterials. Using those microfibers, we built microsupercapacitors that reach a high volumetric capacitance of 52 F cm−3, energy density of 7.1 mWh cm−3, and power density of 1645.7 mW cm−3, respectively. We further demonstrate the 3D integration of multiple fiber microsupercapacitors that reduces the device footprint by 75% while expanding the operational voltage and current window. This strategy is a promising tool for harmoniously assembling carbon nanostructures as energy storage components for various energy applications.