Synthesis Of Co-based Spinel Electrode Materials On Ni Foam And Their Application In Supercapacitors

The properties of electrode materials are directly related to the energy storage capacity of supercapacitors.The preparation of the electrode materials with excellent electrochemical performance,good stability and good conductivity has been the main research direction of researchers.Due to their structural characteristics and good electrochemical activity,transition metal oxides overcome the shortcoming of poor electrochemical performance of carbon materials,and show good cycle stability.As a new battery-type electrode material of supercapacitors,the spinel transition metal oxides?AB₂O₄?have remarkable electrochemical performance and attracted increasing attention in recent years.Co-based spinel electrode materials are one of the leading electrode materials with excellent performance.The intention of this thesis is to design and synthesize a new Co-based spinel electrode material with outstanding performance,and combine it with AC to improve the energy density of the ASC device.We choose Ni foam as the conductive substrate and directly grow the Co-based spinel materials on it to form the electrode material with 3D structure.By changing the reaction conditions,the factors that affect the properties of the materials were explored,and the experimental data and theoretical support for the practical application of the material were provided.The research of this thesis has achieved the following results:1.MgCo₂O₄ nanosheet arrays were directly grown on Ni foam as conductive substrate by a simple and effective one-step solvothermal method,and its electrochemical performance was tested by making a binder-free electrode.The effects of reaction temperature and solvent on the composition and morphology of the product were also studied,and the optimum conditions were found.The results showed that the MgCo₂O₄ nanosheet arrays directly grown on Ni foam exhibited high specific capacity of 853.06 C g^-1 at the current density of 1 mA cm^-2.And the material also had good cycle stability,which can be used as a substrate for further preparation of core-shell composite materials.2.Based on MgCo₂O₄ nanosheet,a simple and controllable two-step solvothermal method was designed and used to directly grow the MgCo₂O₄@MnO₂ core-shell nanosheet arrays structure on Ni foam,and the effect of the reaction time on the morphology and property of the products was also investigated.The results showed that the MgCo₂O₄@MnO₂ composite electrode had the best property at the reaction time of2 h,and maintained 91.45%of its initial capacity after 5000 cycles.Moreover,an all-solid-state ASC with PVA-KOH gel as electrolyte and an aqueous ASC with 1 mol/L KOH solution as electrolyte were assembled by using this material,both showing high energy density and cycling stability.The energy density of all-solid-state ASC device was 4.8 Wh kg^-1 at the high power density of 3526.7 W kg^-1,while that of the aqueous ASC device was 26.44 Wh kg^-1 at the power density of 289.9 W kg^-1 and 13.96 Wh kg^-1 at a higher power density of 3865.3 W kg^-1.3.MgCo₂O₄@MMoO₄?M=Co,Ni?nanosheet arrays were also prepared by a two-step solvothermal method,and their electrochemical properties as battery-type electrode materials were also tested.The specific capacity of the two composite materials using as electrode materials could reach 1089.94 C g^-1 and 1111.57 C g^-1respectively,and they also had good cycling ability.MgCo₂O₄@MMoO₄//AC ASCs were assembled using 1 mol/L KOH solution as the electrolyte and both of them showed high energy density and excellent cycle stability.