Synthesis And Electrochemical Performance Of Co,Ni And Fe Based Functional Nanomaterials For Supercapacitor

Supercapacitor（also called electrochemical capacitor）has been widely studied because of its high power density,good rate capability,fast charging and discharging rate,long-term cycling stability,wide temperature scope and simple preparation method.Supercapacitor is widely used in energy storage systems,mobile electronics,electric cars and hybrid vehicles.According to the equation E=1/2CV²,the energy density of the supercapacitor is proportional to the capacitance and the square of voltage window.Therefore,it is an effective method to improve the electrochemical properties of supercapacitor by preparing electrode materials with high capacitance and large voltage window.Cobalt,Nickel and Iron are used as the basic elements to prepare CoNiFe-LDH/CNFs nanocomposite and NiFe-LDH/RGO/CNFs nanocomposite.The morphology,composition and electrochemical properties of the obtained materials were systematically investigated by XRD,XPS,FE-SEM,TEM,FT-IR,TGA,CV,GCD and EIS.Except that the obtained materials were applied in asymmetric supercapacitor.The main research contents are as follows:（1）A novel CoNiFe-LDH/CNFs nanocomposite was developed through an easy in situ growth approach.The CoNiFe-LDH/CNFs nanocomposite displayed high specific capacitance(1203 F A g^-1)at 1 A g^-1.Considering the wonderful performance of the CoNiFe-LDH/CNFs nanocomposites,the asymmetric supercapacitor based on CoNiFe-LDH/CNFs as a positive electrode and activated carbon as a negative electrode was manufactured.It exhibited a high energy density(30.2 W h kg^-1)and the corresponding power density was 800.1 W kg^-1.It can be used as one of candidate electrode materials for supercapacitor.（2）A novel Ni Fe-LDH/RGO/CNFs nanocomposite was developed through an easy in situ growth approach.In addition,NiFe-LDH/CNFs,NiFe-LDH/CNTs and NiFe-LDH/RGO nanocomposites were prepared by the same method.The specific capacitance of NiFe-LDH/RGO/CNFs nanomaterial was 1330.2 F g^-11 at 1 A g^-1.It was larger than that of NiFe-LDH/CNFs,NiFe-LDH/CNTs and NiFe-LDH/RGO nanomaterials.Thus,asymmetric supercapacitor was assembled by using the NiFe-LDH/RGO/CNFs nanomaterial as the positive electrode material and activated carbon as the negative electrode material.It displayed high energy density of 33.7 W h kg^-1 at power density of 785.8 W kg^-1.Two flexible AC//LDH-RGO-CNFs ASC devices connected in series were able to light up a red LED indicator after being fully charged.This electrode material has excellent electrochemical properties and has good application prospect.