| Popis: |
Nano-engineering of electrode through a versatile spray coating and subsequent electrochemical controlled modifications with metal oxide have been explorated toward a specific design of electroactive material targeting an increase energy densities in supercapacitors while maintaining high power densities. Exploiting pseudocapacitance and nanostructuration by combining transition metal oxides and nanostructured carbon materials in one electrode is considered as one of the best ways to achieve these performances. In this study, carbon nanotubes/graphene/manganese dioxide nanostructured films were designed as supercapacitors electrodes. MnO2 is a well-known pseudocapacitive material used to increase the energy density allowing quite good cyclability of thousand cycles. The selected carbon nanomaterials generate high conductivity and their association is an efficient way to insure large surface area to maintain a high power density. The challenge is to assemble these materials into a nanostructured electrode with controlled homogeneity, morphology, and composition. Our approach consists in synthesizing MnO2 by anodic electrodeposition directly onto the conductive nanostructured carbon framework. The association of carbon nanotubes and graphene in a specific multi-layered organization by spray aim at creating a porosity controlled network in the electrodes with highly accessible and electroactive surface. The carbon nanomaterials were deposited onto a current collector by dynamic automated spray gun deposition, an easily scalable, reproducible and industrially suitable method used for nanostructuration of thin films. Materials were characterized by SEM, XPS, microporosity analysis; their electrochemical behavior has been evaluated by cyclic voltammetry and impedance spectroscopy and their performances and cyclability by galvanostatic charge/discharge experiments. Results demonstrate that the capacitance can reach up to 190 F/g (110 F/cm3) for binder free electrodes thanks to a control of the MnO2 morphology, particle size and mass loading. |
