Flexible Quasi-solid-state Supercapacitors Based On Activated Carbon Cloth

With the rapid development of portable electronic devices, there is a straightforward push for efficiently and advanced energy storage devices which are able to store more energy and flexible. At present there is no energy storage products on the market can meet the needs, so we designed a series of flexible carbon-based supercapacitors, hoping to meet the marketing requirements for flexible energy storage products. In this study,commercial high conductivity carbon fiber cloth was used as the base material to improve the electrochemical properties of supercapacitors by electrochemical activation,chemical vapor deposition and high temperature calcination. The composite electrochemical active materials (carbon nanotubes, transition metal oxide) as an electrode material for flexible supercapacitors. The processed electrodes were assembled into a series of flexible all solid-state energy storage devices by gel electrolyte. We discussed a series flexible supercapacitors based on commercial carbon cloth:symmetrical supercapacitor(denoted as S1)assembled by activated carbon cloth assembled , symmetrical pseudo-capacitance supercapacitor(denoted as S2 ) assembled by Nano-Nickel particles/multi-walled carbon nanotubes and asymmetric pseudo-capacitance supercapacitor (denoted as S3) assembled by metal oxide film/multi-walled carbon nanotubes composite electrodes .The electrodes of device S1 was prepared by constant voltage electrochemical activation, following by high temperature calcination treatment. The capacity of the electrodes increased by more than 100 times compared with untreated carbon cloth, and the synthesis process is simple and environmentally friendly, which is suitable for industrial production.The electrodes of device S2 was prepared by one-step method straightforwardly synthesis the Nano-nickel particles/multi-walled carbon nanotubes combination electrodes as positive and negative supercapacitor electrodes. This combination electrodes not only can make use of the faraday capacitance of high-active nickel particles embedded in the multi-walled carbon nanotubes in positive voltage range, but also make use of double electric layer capacitance of multi-walled carbon nanotubes in the negative voltage range. By excavating the latent energy from the full voltage range to maximize the capacity utilization. For the first time we made a pseudo-supercapacitor that do not need to distinguish between positive and negative, which means that the positive and negative charging p can be symmetrical.Device S3 utilized a dense mesh multi-walled carbon nanotube coated with a transition metal oxide active material (nickel oxide and iron oxide films) based on carbon cloth as the positive and negative electrodes. The structure can improve the space utilization of the conductive carbon cloth and enhance the capacitor provided by the positive and negative faraday reaction. This metal oxide film/multi-walled carbon nanotubes compositions was able to provide much more pseudo-capacitance with a stable discharge voltage.This study could provide some novel and facile strategy for the development of advanced energy storage devices with high safety and convenience. The as-prepared flexible composite presented ideal capacitive behavior with excellent performance for both positive and negative electrodes. The devices delivers high special energy and power densities, good rate capability, outstanding mechanical stability, and long cycling life.