One-step fabrication of binder-free three-dimensional Co 3 O 4 electrodes by Reactive Spray Deposition Technology for ap
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Research Letter
One-step fabrication of binder-free three-dimensional Co3O4 electrodes by Reactive Spray Deposition Technology for application in high-performance supercapacitors Yang Wang and Junkai He, University of Connecticut, 97 N Eagleville Rd, Storrs, CT 06269, USA Justin Roller, Thermo Fisher Scientific, 5350 NE Dawson Creek Drive, Hillsboro, OR 97124, USA Radenka Maric, University of Connecticut, 97 N Eagleville Rd, Storrs, CT 06269, USA Address all correspondence to Yang Wang at [email protected] (Received 26 January 2018; accepted 28 March 2018)
Abstract Binder-free three-dimensional Co3O4 electrodes are fabricated by an economical and scalable one-step flame combustion method, namely Reactive Spray Deposition Technology. The electrodes are composed of porous nanostructured Co3O4 uniformly distributed throughout the conductive substrate. In the absence of any further optimization on the processing conditions, the as-synthesized electrodes demonstrate high capacitance of 567 F g−1 at 1.5 A g−1, excellent rate capability, and stable cycling performance with a capacity retention ratio of 96.7% after 1000 charge/discharge cycles from the three-electrode half-cell testing. This study presents the pathway to a significantly simplified manufacturing process of three-dimensional electrodes with the desirable porous nanostructure.
Introduction In recent years, supercapacitors have drawn considerable attention from researchers as an alternative energy storage device. They offer benefits such as high-power density, fast charge/discharge capability, and excellent cycling stability.[1,2] Some of their diverse applications include brake energy recuperation, power tools, and uninterrupted power supply.[3,4] Supercapacitors (pseudocapacitors) primarily store energy via Faradic pseudocapacitance arising from the reversible redox reactions on the surface of the electrode materials. Transition metal oxides are frequently studied as the electrode materials for pseudocapacitors, such as NiO, Co3O4, ZnO, Fe3O4, SnO2, CuO, and MnO2.[4–10] In addition, the conducting polymers have also been investigated as the electrode materials for pseudocapacitors, which include polyaniline, polypyrrole, poly[3,4-ethylenedioxythiophene], and so on.[11–13] The mechanism of energy storage in the conducting polymers is based on both the electrical double layer and the rapid faradic charge transfer. Co3O4 is of special interest for investigation primarily due to its high theoretical-specific capacitance and excellent redox activity. However, low-power handling capability and poor cycling performance significantly hinder its application in highperformance supercapacitors. One of the effective solutions to these challenges is to fabricate three-dimensional Co3O4 electrodes with the porous nanostructure, which shortens the transport pathway lengths of the electrons and the ions and thus enhances the kinetics of the Faradaic redox reactions. High surface-to-volume ratio of the nanostructure provides additional electroactive sites for the redox reacti
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