Study On Morphology And Properties Of Metallic Compounds Based On Supercapacitor

Supercapacitors are a new type of energy storage devices and have attracted widespread attention due to their high power density,fast charge/discharge rates and long cycle life.As a member of supercapacitors,pseudocapacitors undergo rapid and reversible oxidation-reduction reactions to store and convert energy.Lots of researches are focused on metal-based compound nanosheet arrays electrodes and these electrodes directly grow on a certain conductive substrate as a binder-type material.This design allow the electrode material to come into close contact with the substrate to form a certain array element,and the gap between the arrays is beneficial for the diffusion of electrolyte ions,thereby increasing the utilization of the material.In addition,the core-shell structure material is formed by the combination of different types of electrodes,so as to achieve the synergistic effect of different components.In this paper,the electrodes containing magnesium,cobalt,nickel and molybdenum were synthesized by controlling and optimizing the structure and morphology of the electrode materials,and the effects of structure and morphology on the performance of the electrode were analyzed.The main experimental work and achievements are as follows:1.The Co-Mg compound@NiMoO₄ nanosheet arrays electrode with core-shell structure was prepared on the Ni foam via two-step hydrothermal method,and its electrochemical performance was also investigated.The capacitance performance of the integrated electrode was improved remarkably due to the synergistic effect of core-shell nanosheet structure and the Co-Mg compound@NiMoO₄ electrode had better electrochemical performance than the first layer of electrode.Under the optimum preparation conditions,NiMoO₄ was directly heated on the double hydroxide structure for 6h and its area-specific capacitance and mass-specific capacitance of the integrated electrode were 6.50 F·cm^-22 and 2031 F·g^-11 at the current density of 5 mA·cm^-2.Using activated carbon as negative electrode and optimum electrode material as positive electrode,and the two materials are assembled into asymmetric supercapacitor device.The device had a maximum energy density and power density of 57 Wh·kg^-11 and 4.8kW·kg^-1,separately,while the device also showed excellent electrochemical performance and cycle life.2.A large area of CoMoO₄ nanosheet arrays electrode was successfully prepared on Ni foam via simple hydrothermal method.The various morphology of the electrodes were obtained by controlling the hydrothermal reaction time and these electrodes were directly subjected to electrochemical performance test.The results showed that CoMoO₄could exhibit good capacitance characteristics,and the CoMoO₄ electrode had excellent electrochemical properties at the hydrothermal time of 12h.The area specific capacity and mass specific capacity of CoMoO₄ electrode were 3.93 F·cm^-22 and 1310 F·g^-11 at the current density of 5 mA·cm^-2,respectively.Moreover,the capacity retention rate was90%after 10000 cycles at a current density of 40 mA·cm^-2.This results could be attributed to the reversible electrochemical properties of CoMoO₄ electrode materials as well as the unique open space structure formed by the nanosheet arrays.3.The NiMoO₄ nanosheet arrays was synthesized via similar methods and the influence of the hydrothermal time on the electrochemical results of the electrode was discussed.while the current density was 5 mA·cm^-2,the specific capacity was 3.05F·cm^-2,and the specific capacity was maintained at 1.82 F·cm^-22 even the current density was increased to 40 mA·cm^-2.In addition,the NiMoO₄ electrode had excellent cycling capacity and the capacitance maintained at 87%compared with the initial capacity after10000 charge and discharge cycles.