Ultrafast hydrothermal assembly of nanocarbon microfibers in near-critical water for 3D microsupercapacitors

• Main Authors: Zhai, Shengli, Wei, Li., Karahan, Huseyin Enis, Wang, Yanqing, Wang, Chaojun, Montoya, Alejandro, Shao, Qian, Wang, Xin, Chen, Yue
• Other Authors: School of Chemical and Biomedical Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Chemical engineering; Capacitance; Energy Conservation
• Online Access: https://hdl.handle.net/10356/138966
• Institution: Nanyang Technological University

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.