Journal Article

Scalable synthesis of hierarchically structured carbon nanotube–graphene fibres for capacitive energy storage

Jiang, Wenchao, Goh, Kunli, Wang, Hong, Zhang, Qiang, Chen, Yuan, Dai, Liming, Yu, Dingshan, Wei, Li

2014

Overview

Micro-supercapacitors are promising energy storage devices that can complement or even replace batteries in miniaturized portable electronics and microelectromechanical systems. Their main limitation, however, is the low volumetric energy density when compared with batteries. Here, we describe a hierarchically structured carbon microfibre made of an interconnected network of aligned single-walled carbon nanotubes with interposed nitrogen-doped reduced graphene oxide sheets. The nanomaterials form mesoporous structures of large specific surface area (396 m 2  g −1 ) and high electrical conductivity (102 S cm −1 ). We develop a scalable method to continuously produce the fibres using a silica capillary column functioning as a hydrothermal microreactor. The resultant fibres show a specific volumetric capacity as high as 305 F cm −3 in sulphuric acid (measured at 73.5 mA cm −3 in a three-electrode cell) or 300 F cm −3 in polyvinyl alcohol (PVA)/H 3 PO 4 electrolyte (measured at 26.7 mA cm −3 in a two-electrode cell). A full micro-supercapacitor with PVA/H 3 PO 4 gel electrolyte, free from binder, current collector and separator, has a volumetric energy density of ∼6.3 mWh cm −3 (a value comparable to that of 4 V–500 µAh thin-film lithium batteries) while maintaining a power density more than two orders of magnitude higher than that of batteries, as well as a long cycle life. To demonstrate that our fibre-based, all-solid-state micro-supercapacitors can be easily integrated into miniaturized flexible devices, we use them to power an ultraviolet photodetector and a light-emitting diode. Hierarchical hybrid carbon fibres consisting of a network of nitrogen-doped reduced graphene oxide and single-walled carbon nanotubes are synthesized and subsequently used to make a supercapacitor with high volumetric energy density.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/301/299/161 / 639/925/357/73 / 639/925/918 / Carbon / Carbon fibers / Computer storage devices / Continuous fiber composites / Density / Electric batteries / Electric Capacitance / Electrical conductivity / Electrical resistivity / Electrodes / Electrolytes / Energy density / Energy storage / Engineering / Fibers / Fibres / Flux density / Graphene / Graphite - chemistry / Light emitting diodes / Lithium / Lithium batteries / Materials Science / Microelectromechanical systems / Nanomaterials / Nanotechnology / Nanotechnology and Microengineering / Nanotubes / Nanotubes, Carbon - chemistry / Nitrogen / Polyvinyl alcohol / Polyvinyl alcohols / Portable equipment / Separators / Silica / Silicon dioxide / Single wall carbon nanotubes / Storage batteries / Sulfuric acid / Supercapacitors / Surface area / Thin films / Ultraviolet detectors / Ultraviolet radiation