Preparation Of Co-based Double Metal Oxide And Graphene Composites And The Research On Capacitance Performance

Supercapacitors are characterized by high power density,high charge and discharge efficiency and safety,which are widely used in aerospace,transportation,and electronic equipment.Electrode materials are the most important component of supercapacitor that matter the overall performance.Co-based double metal oxides which are tantalum capacitor materials have high theoretical specific capacities.Graphene which is an electrode material of the electric double layer capacitor has a high conductivity,a large specific surface area,and a good cycle stability.In this dissertation,,the composite material of cobalt-based double metal oxides and graphene are prepared,which not only can exert the high specific capacity of cobalt-based double metal oxides,but also can exert the high cycle stability of graphene.It improves the electrochemical performance of the entire supercapacitor and has important research significance and application value.The main contents are as follows:1.We have prepared a Co-Ni double metal oxide/graphene composite with aerogel structure by combustion drying method.The three-dimensional aerogel structure has a continuous and abundant pore structure.This material has a specific capacity up to 1694 F g^-1 at the current density of 1 A g^-1.After 3000 cycles,the capacity is maintained at 82%which shows high specific capacity and cycle stability.The asymmetric supercapacitor assembled by cobalt-nickel double metal oxide/graphene//graphene has a specific capacity of 127 F g^-1 at the current density of 1 A g^-1,a power density of 238.18 W kg^-1 and an energy density of 57.15 Wh kg^-1.The capacity retention rate is 87.5%after 3000 cycles,showing a good cycle stability.The composite aerogel material not only reduces the internal resistance but also increases the specific surface area of the electrode,thereby improving the overall performance of the capacitor.2.The nanosphere-type manganese-cobaltate/graphene composites are synthesized by one-step hydrothermal method.The nanosphere-type manganese cobaltate is formed while being uniformly attached to the graphene surface.The specific capacity of the composite material at the current density of 1 A g^-1 was as high as 1719 F g^-1 and the capacity retention rate was 93%after 3,000 charge and discharge cycles,which showes a very good electrochemical performance.The voltage window of the assembled cobalt-manganese double metal oxide/graphene//graphene asymmetric supercapacitor is expanded to 1.7 V.At the current density of 1 A g^-1,the power density is 452.9 W kg^-1 and the energy density can reach 25.1 Wh kg^-1.The experimental operation of this method is simple with the low cost.the electrochemical performance of the material is very good.3.The graphene negative electrode prepared by the optimization of the binder,the additive,and the solvent effectively avoids the agglomeration phenomenon.The symmetric supercapacitor assembled by graphene has a specific capacity of 97 F g^-1,a power density of 120.9 W kg^-1 and an energy density of up to 14 Wh kg^-1 at the current density of 1 A g^-1.And after 3000 cycles,the capacity is almost no attenuation,showing a excellent cycle stability.Finally,the prepared manganese cobaltate/graphene composite was analyzed by market economy,the result shows that this material has broad application prospects and high market value.