The synthesis of carbon microspheres film composed of nano-onions and its application as flexible supercapacitors

Flexible electrodes with superior mechanical and electrochemical properties are essential for flexible supercapacitors. A convenient and scalable colloidal filmassisted chemical vapor deposition（CF-CVD） method is developed for the one-step fabrication of the carbon microspheres films composed of carbon nano-onions（CMS-CNO films）. The influence of growth conditions（such as growth temperature, time, and gas ratio） during CF-CVD process on the carbon structures and the growth mechanism of the CMS-CNO films have been investigated. By controlling the growth conditions, the controllable preparation of CMS-CNO films is realized.Such binder-free films can be used for the assembly of flexible supercapacitors, and unique architecture can achieve excellent performance. Benefitting from the composite of nano-micro zero dimensional structures, the performance of the film in supercapacitors is remarkably improved. At the current density of 5 mA cm-2,the area-specific capacity can be 903 mF cm-2. When the current density is increased to 500 mA cm-2, the area-specific capacity can be increased to 729 mF cm-2. This simple and low-cost preparation process and the superb electrochemical performance suggest great potential applications of CMS-CNO films in flexible supercapacitors.