Research On Supercapacitor Electrode Material Of Binary Metal Oxide With High Specific Capacity

With the rapid development of global economy and the increasing consumption of fossil fuels,there are more and more environmental pollution problems.Therefore,the research and development of high-performance and environmental protection energy storage devices has become one of the urgent problems in the development of energy technology.Supercapacitor,due to its fast charge and discharge,excellent cycle and rate performance,ultra-high power density,environment-friendly,has become one of the most concerned energy storage devices.However,the low energy density greatly limits its development and becomes an urgent problem for supercapacitors.Asymmetric supercapacitors use two electrodes with different energy storage mechanisms as positive and negative electrodes,battery electrode as positive electrode and capacitor electrode as negative electrode.Battery electrode is used as energy source and capacitor electrode as power source.It can not only maintain ultra-high power density,but also achieve high energy density,making it a strong competitor of the new generation of energy storage devices.The electrode materials of asymmetric supercapacitors greatly affect the electrochemical performance of devices.Therefore,high performance electrode materials are helpful to further improve the performance of the device.In this paper,we choose excellent electrode materials and design reasonable structure,in order to improve the overall performance of the device,and hope to get an idea and strategy to design excellent electrode materials.（1）The three-dimensional hollow nano cubic structure assembled by NiMoO₄two-dimensional nanosheets was prepared by solvothermal and etching process.The three-dimensional structure was used to maintain stability,so as to slow down the change of volume and structure as much as possible in the process of redox reaction.The low dimensional nanosheets were used to provide specific surface area and rich reactive sites.Based on this idea,we also prepared high-performance NiMoO₄nanocubes.At a current density of 1 A/g,the specific capacity can reach 1093 F/g,and can maintain 679.5 F/g even at 10 A/g.The NiMoO₄//N-r Go device assembled with N-r Go has a capacity retention rate of 84.7%after 5000 cycles at a current density of 2 A/g.When the power density is 769W/kg,the energy density has reached 44.10 Wh/kg.When the power density is 7.7 k W/kg,the energy density is still as high as 23.68 Wh/kg.（2）Ni-Co oxides with more redox reactions were selected to fabricate stable three-dimensional hollow Ni Co₂O₄nanocubes by a simple one-step precipitation etching method.Multiple metal oxides not only provide more abundant electrons,but also increase the conductivity of the material,making the reaction easier.Under the above cooperation,the electrode has excellent electrochemical performance.The specific capacity of the electrode is 2400 F/g at the current density of 1 A/g and 940 F/g can be retained at 2 A/g.After the Ni Co2O4//N-r GO asymmetric supercapacitor device was assembled with N-r GO,the specific capacity reached 231 F/g at a current density of 1 A/g,and maintained 63.5 F/g at a high current density of 10 A/g,which confirmed its excellent electrochemical performance.（3）Using a one-step hydrothermal method to prepared the 3-dimensional NiMoO₄nanospheres,which are grown on the foamed nickel without binder.Nickel foam is used as substrate to make it as work electrode directly.The electrode is more firmly bonded to the substrate.No binder or conductive agent is needed to make the active material better contact with the electrolyte,which is favorable for the reaction.Two dimensional and ultra-thin NiMoO₄nanosheets were grown on the nanospheres,and there was almost no agglomeration between the nanosheets.The effect of temperature on the morphology was explored.The best nanospherical morphology was obtained by adjusting and controlling the temperature.At the same time,the specific surface area of the material was well utilized.The specific capacity of the sample NiMoO₄-140 was as high as 2100 F/g at 1 A/g current density.The specific capacity of NiMoO₄-160 reaches 1093 F/g at the same current density.It also shows excellent electrochemical performance.