Construction Of Core–shell Nanomaterials And Their Electrochemical Performance For Supercapacitor Electrode Materials

With the exhaustion of fossil fuels,there is imperative to strengthen the exploitation and utilization of sustainable sources of energy.If want to achieve the effective use of renewable energy,we must develop the efficient energy storage device of environmental protection.Supercapacitor is a new efficiency energy storage device between traditional capacitor and chemical battery.Its energy density is higher than conventional capacitors and power density is also superior to chemical battery.Moreover,supercapacitor also has a number of advantages,such as long cycle life,environmental friendly and high safety level.As an important part of supercapacitor,electrode materials play a decisive role for improving the performance of supercapacitor.Research emphasis of this article is to build unique core-shell metal oxide through simple hydrothermal,electrochemical deposition and co-precipitation method in different substrate and improving the electrochemical performance of electrode materials by this rational structure.MnO₂ core-shell nanostructure has in-situ grown on carbon spheres?MnO₂-MnO₂/C?via an effective two-step hydrothermal method.Such nanostructure enhances the specific surface area of MnO₂,and effectively decreases the ion diffusion and charge transport resistance in the electrode reaction.Meanwhile,the core-shell nanowires are interconnected with each other forming a highly stable structure,make the composite electrode has good cycle stability.Results of the electrochemical test reveal that the MnO₂-MnO₂/C electrode exhibits good rate performance and electrochemical reversibility,showed specific capacitances?225 F/g?2.1 times higher than that of MnO₂/C composite and excellent cycling stability with the retention ratio of 90%after 5000 cycles.Three-dimensional NiCo₂O₄ core-shell nanowire arrays were fabricated on nickel foam?NiCo₂O₄-NiCo₂O₄/NF?viaafacilehydrothermalmethodandthesubsequent electrodeposition method.This core-shell electrode material not only shortens the ion diffusion paths but also provides a large number of electroactive sites for redox reaction,exhibited a superior electrochemical performance,including high specific capacitance of 2041F/g,good rate performance and an excellent long-term cyclic stability that can retention the maximum capacitance of 85%after 3000 cycles in the current density of 50 mA/cm².NiCo₂O₄ nanowires were prepared by hydrothermal method,and carbon fiber paper?CFP?was used as the flexible substrate.The growth of NiCo₂O₄ nanowires on the carbon paper substrate were explored under the different reaction time,and the optimal reaction time was determined.NiCo₂O₄ nanowires grown on a carbon paper substrate were acted as the"skeleton"for the further deposition of NiCo₂O₄ nanosheets with co-precipitation method,finally the core-shell NiCo₂O₄ nanowires?NiCo₂O₄-NiCo₂O₄/CFP?were constructed on the flexible substrates successfully.The electrode of the core-shell NiCo₂O₄ nanowires could effectively improve the utilization rate and pseudo-capacitance characteristics of the electrode materials,and had a good cycle life at the same time?The specific capacitance maintained at about 92%of the initial capacity after 1000 cycles?.