Study On Selenide Cathode Materials For High Energy Density Hybrid Supercapacitor

Supercapacitors are a new kind of energy storage device.In the field of energy storage,supercapacitors have received considerable attention due to their enormous power density and long cycle life.However,compared to batteries,low energy density is the main obstacle limiting the commercial application of supercapacitors.Transition metal selenides have attracted considerable attention due to their excellent electrical conductivity,high theoretical capacity,and structural diversity.In this thesis,we mainly used electrochemical deposition method to design and prepare selenide supercapacitor electrode materials,compared and analyzed the effects of experimental parameters on the morphology and properties of the composite materials,and assembled asymmetric supercapacitors.A series of practical applications of selenides have been studied.The main content of this thesis as follows:（1）Binder free CoSe nanoparticles were successfully prepared on a carbon cloth substrate grown with vertical graphene by different electrochemical deposition methods.The results make clear that the electrode material composed by constant voltage deposition at-1 V voltage exhibits porous morphology and excellent performance.When the current density is 1 A·g^-1,the capacity can reach 485.5 F·g^-1.Assembled with activated carbon CoSe@VG/CC//AC asymmetric supercapacitors have an energy density of 26Wh·kg^-1.After 10000 cycles,the capacity retention rate was approximately 85.68%.（2）Binder free NiCoSe₂ nanoparticles were successfully prepared on a carbon cloth substrate grown with vertical graphene by different electrochemical deposition methods.The results show that the electrode material prepared by constant voltage deposition at-1 V voltage exhibits best property.The specific capacity is 1236 F·g^-1 when the current density is 1 A·g^-1.Assembled with activated carbon NiCoSe₂@VG/CC//AC asymmetric supercapacitors have an energy density of 51.0 Wh·kg^-1.After 10000 cycles,the capacity retention rate is approximately 90.4%.（3）Nitrogen doping was carried out on a carbon cloth substrate grown with vertical graphene by plasma chemical vapor deposition,and then self-supporting NiCoSe₂nanoparticles were successfully prepared by constant voltage deposition at a voltage of-1 V.The obtained electrode material exhibits outstanding property due to the synergistic effect of Ni and Co,as well as the improvement of conductivity due to N doping.The specific capacity is 1958 F·g^-1 when the current density is 1 A·g^-1.Assembled with activated carbon NiCoSe₂@N-VG/CC//AC asymmetric supercapacitor with a superme energy density of 57.14 Wh·kg^-1.After 10000 cycles,the capacity retention rate of the asymmetric supercapacitor is about 95.7%.The above results show that transition metal selenide as electrode material of supercapacitor has great application prospects.