Preparation And Energy Storage Performance Of Two-dimensional Layered Material And Its Composites

With the rapid depletion of fossil energy,the energy crisis makes people's demand for new renewable energy more urgent.The contradiction between the low power density of secondary batteries and the growing demand for electrochemical energy storage makes it important to find new alternative energy storage devices.Supercapacitors are favored by researchers because of their superior power density,extremely short charging time,and long cycle life.Therefore,materials with a two-dimensional layered structure were selected as the research objects in this paper.The following research results were obtained:?1?NiCo₂S₄@GR nanocomposites with hyperdispersed NiCo₂S₄ nanoparticles on the surface of Graphene sheets was synthesized by ethanolamine assisted solvothermal method.In a three-electrode system,a specific capacitance of 1708 F g^-1 was exhibited at a current density of 1.0 A g^-1.When the material is assembled with activated carbon as a asymmetric supercapacitor?based on the total mass of the active material?,at a power density of 850.0Wkg^-1,the energy density is as high as 68.5 Wh kg^-1,and the ultrahigh power density is at 17.0kW kg^-1,the energy density is still as high as 37.7 Wh kg^-1.The excellent electrochemical performance makes Ni Co₂S₄@GR nanocomposites become one of the most promising electrode materials for electrochemical energy storage devices.?2?A series of Ni_xCo₂Al-LDH with Nanosheet structures were synthesized by hydrothermal reaction among which,NiCo₂Al-LDH exhibited the best electrochemical performance in supercapacitors.In a three-electrode system,a specific capacitance of 2369.4 F g^-1 was exhibited at a current density of 1.0 A g^-1.When assembled with activated carbon into an asymmetric supercapacitor?based on the total mass of the active material?,an ultra-high energy density of 91.0 Wh kg^-1 can be achieved at a power density of 758.2 Wkg^-1 and even at a high power density of 22.7 kW k At g^-1,it still has an energy density of 50.5 Wh kg^-1.The feature of long cycle life and high rate performance of the device brings more possibilities for the application of NiCo₂Al-LDH in supercapacitors.?3?CoSe₂@GR nanocomposites grown on graphene surface were prepared by a simple one-step hydrothermal method.In a three-electrode system,a specific capacitance of 2369.4 F g^-1 was exhibited at a current density of 1.0 A g^-1.When assembled with activated carbon into an asymmetric supercapacitor?based on the total mass of the active material?with a PVA/KOH gel as the solid electrolyte,the flexible device has a high voltage of 1.7 V and reaches a maximum energy density of 66.4 Wh kg^-1 at a power density of at 850.0 W kg^-1,when the maximum power density is 27.2 W kg^-1,the energy density is still as high as 30.2 Wh kg^-1.Due to its high electrochemical activity and high electrical conductivity,CoSe₂@GR nanocomposites become one of the promising electrode materials for flexible electrochemical energy storage devices.