Flexible CoO-graphene-carbon nanofiber mats as binder-free anodes for lithium-ion batteries with superior rate capacity and cyclic stability

Flexible mats composed of CoO-graphene-carbon nanofibers have been prepared by electrospinning and a subsequent thermal treatment. The flexible mats of CoO-graphene-carbon annealed at 650 degrees C exhibited discharge capacities of 760 and 690 mA h g(-1) at the 252nd and 352nd cycle, respectively, at a current density of 500 mA g(-1), which are much higher than those of pure carbon, graphene-carbon, and CoO-carbon nanofibers at the respective cycles. The CoO-graphene-carbon nanofibers can deliver a discharge capacity of 400 mA h g(-1) at a current density of 2 A g(-1), which is also higher than the values obtain for CoO-carbon and graphene-carbon nanofibers. The improved electrochemical properties of the flexible CoO-graphene-carbon nanofiber mats could be ascribed to the framework, which allows for fast diffusion of Li+, the presence of graphene, which enhances the conductivity and the mechanical properties of the mats, and the defective sites that arise from the introduced CoO and graphene which can store Li+. It is believed that the electrospinning method used to combine the material with graphene could be a useful approach to prepare flexible mats for lithium-ion batteries, supercapacitors, and fuel cells.