Microwave-assisted Synthesis And Electrochemical Performance Of Carbonate/Hydroxide-transition Metal Compounds

With the development of human society,the demand for energy is increasing,and traditional fossil energy can no longer meet the needs of human long-term development.Therefore,the development and utilization of new energy storage equipment has become a current research hotspot.Supercapacitors are considered to be the promising energy storage devices due to their high-power density,long cycle life,and good charge-discharge performance.Although there are many methods to prepare electrode materials for supercapacitors,such as hydrothermal synthesis,electrodeposition,and template method,these conventional methods not only cost a lot of time but also consume a lot of manpower and financial resources.The microwave-assisted hydrothermal method has the characteristics of shortening the reaction time and promoting the nucleation which helps to obtain a uniform product.In this paper,sea urchin-like Mn CO3-Co（CO3）0.5OH（MC）and three-dimensional Ni-Co Layered double hydroxides（LDHs）（NC）compounds were prepared via the microwave-assisted hydrothermal method,and their electrochemical properties as supercapacitor electrode materials were also explored.（1）The MC compounds were first synthesized by the microwave-assisted hydrothermal method and the influence of different times on the structure and morphology of the samples were also explored.The increase of time has no obvious effect on the structure of the MC samples but has a certain impact on the morphology of the surface nanoneedles.The MC-10 electrode was used as electrode materials in the supercapacitors for the electrochemical properties test in a three-electrode system,which delivered a high specific capacitance of 839.58 F g^-1 at 1 mAcm^-2 and excellent cycling stability with an 82.12%retention rate at a high current density of 6 mAcm^-2after 8000 cycles.（2）The NC microsphere composites were synthesized rapidly under microwave-assisted conditions,and the effects of microwave reaction time and temperature on the crystal structure,morphology,and electrochemical properties of NC composites were investigated.The results showed that the increase of reaction time and temperature will have a significant impact on the structure and morphology which caused differences in electrochemical performance.The NC-100-10 electrode exhibited excellent electrochemical performance,which delivered a high specific capacitance of 774.93 F g^-1 at 1 mAcm^-2 and excellent cycling stability with a 90.75%retention rate at a high current density of 3 mAcm^-2 after 5000 cycles.