Preparation Of NiCo(Mn)-LDH/Multilayer Graphene Composite And Its Supercapacitor Performance

The synergistic effect between multiple metal hydroxides can improve the poor cycle stability of single metal hydroxides,which is an important research direction of pseudo capacitor electrode materials.However,the high resistivity makes its high theoretical capacity unable to play.Multi-element metal hydroxides and multi-layer graphene with simple process and low cost are compounded,Nickel cobalt(manganese)hydroxide was grown on the surface of multilayer graphene by hydrothermal method,and its electrochemical properties of the composite were studied.The main contents are as follows:(1)Nickel cobalt hydroxide/multilayer graphene composites were prepared by hydrothermal method.The effects of the molar ratio of nickel to cobalt,the amount of urea and the total amount of nickel and cobalt on the electrochemical properties of the composites were studied.When the total amount of nickel and cobalt is 1 m M,the molar ratio of nickel and cobalt ions is 6:4,and the amount of urea is 100 mg,the electrochemical performance of the sample is the best.The specific capacity of the composite is 2206.98 F g^-1at 1 A g^-1.The specific capacity retention rate was88.09%at 10 A g^-1.The specific capacity retention rate is 22.2%after 5000 cycles of charge and discharge at 4 A g^-1.Asymmetric supercapacitors were prepared by using nickel cobalt hydroxide/multilayer graphene composite as cathode material and activated carbon as anode material.Under the voltage range of 0-1.6 V and current density of 1 m A cm^-2,the specific capacity,power density and energy density of the asymmetric supercapacitor are 89.23 F g^-1,129.05 W kg^-1and 31.73 Wh kg^-1respectively.At 4 m A cm^-2current density,the specific capacity retention rate is 87%after 1000 cycles of charge and discharge.(2)Nickel cobalt manganese trihydrate/multilayer graphene composites were prepared by hydrothermal method.The effects of different molar ratio of NiCoMn metal ions on the electrochemical properties of the composite were studied.When the molar ratio of nickel,cobalt and manganese is 5:2:3,the sample has the best electrochemical performance.The specific capacity of the composite is 1774.4 F g^-1at 1 A g^-1.The capacity retention was 86.13%at 10 A g^-1.The specific capacity retention is 60.78%after 5000 cycles of charge and discharge at 4 A g^-1.The electrochemical properties of NiCoMn metal hydroxide/multilayer graphene composite were studied by using active carbon as anode material and NiCoMn metal hydroxide/multilayer graphene composite as cathode material.Under the specific current density of 1 m A cm^-2,the specific capacity is 60 F g^-1,the power density is 151.5 W kg^-1,and the energy density is 21.34 Wh kg^-1.The specific capacity retention rate is 90%after 1000 cycles of charge and discharge at 4 m A cm^-2.