With the development of modern science and technology, flexible, wearable, foldable and intelligent electronic devices are the mainstream direction of development. Energy storage devices that provide energy for electronic products are also gradually developing in the direction of light, thin and tough. Flexible supercapacitor is a kind of energy storage device, which has the characteristics of high capacity, fast charging and discharging speed, safety and environmental protection. It has a broad application prospect in the emerging electronic intelligent equipment and other high-tech. Carbon textiles such as carbon fiber and carbon nanotube gauze have been widely studied as flexible electrode active materials and show excellent electrochemical performance. However, because most of the products are aqueous electrolyte, their discharge voltage is lower than 2V, which greatly reduces the energy output of these flexible supercapacitors and limits their development and practical application.
   the team of Zhang Yuegang, International Laboratory of Suzhou Institute of nanotechnology and nanobionics, Chinese Academy of Sciences, recently combined electrospinning technology and high-temperature pyrolysis technology to prepare three-dimensional multi-level structure of vertical carbon tubes grown on one-dimensional carbon fibers and study its electrochemical performance. The growth of vertical carbon nanotube arrays on carbon fibers improves the specific surface area, conductivity, porosity and wettability of the electrolyte. At the same time, the three-body ionic liquid electrolyte is used to replace the traditional aqueous electrolyte to expand the output voltage to 4V, which effectively improves the energy output of the flexible electric container. The specific capacity of the flexible capacitor with ionic liquid as electrolyte reaches 70.7 WH / kg at 30 ° C and current density of 0.5a/g, and 98.8 WH / kg at 60 ° C and current density of 1A / g. The flexible capacitor assembled with this material also shows ultra-high cycle stability, and its capacity retention rate is 97% after 20000 charge discharge cycles. The excellent performance of the three-dimensional flexible carbon electrode material benefits from the use of vertical carbon tubes to store and accumulate charges, while the carbon fiber conductive substrate transports charges to form a three-dimensional conductive network, which greatly promotes the movement speed of electrons and ions and reduces the resistance of the material itself. The related achievements have been published as cover articles in chemistry of materials (DOI: 10.1021/cm 503784x).
   the flexible carbon fiber was used to replace the hard silicon or metal substrate to grow carbon nanotube arrays. At the same time, PVP solid decomposition was used to provide carbon source to avoid the use of combustible gas. The cactus like three-dimensional flexible carbon electrode material was synthesized, which not only reduced the cost, but also improved the safety of preparation. It is expected to be synthesized on a large scale and applied in the future New flexible electronic energy storage equipment.
The above work has been strongly supported by the National Natural Science Foundation of China and the natural science foundation of Jiangsu Province.