Synthesis Of Bimetallic NiMn Transition Metal Based Nanocomposites And Their Energy Storage Properties

Supercapacitors have attracted much attention due to their long cycle life,fast charge and discharge and high power density.They can meet the growing power demands of energy storage systems in the 21st century.Flexible supercapacitors have caused extensive research at home and abroad because of their wearability,light weight and bendability.In this paper,a series of composite electrode materials were synthesized based on NiMn-LDH nanosheets.We tested the morphology,the composition tructure and electrochemical properties of the composites and assembled the flexible solid state devices using the composite electrode materials.The detailed research contents are as follows:(1)NiCo2O4 nano wire arrays were synthesized on carbon cloth by hydrothermal method and annealing method.NiMn-LDH nanosheets were grown on NiCo2O4 nanowires by hydrothermal method to obtain NiCo2O4@NiMn-LDH with core-shell structure composite electrode material.The composite electrode material has a mass ratio capacitance of 278 mAh/g at 2 mA/cm2,and it has excellent rate performance(when the current density is increased from 2 mA/cm2 to 20 mA/cm2,the specific capacity retention ratio is 89.0%).In addition,it is assembled into the NiCo2O4@NiMn-LDH//AC flexible device with a maximum energy density of 47 Wh/kg and a maximum power density of 3079 W/kg.Moreover,the device has excellent cycle performance,and the capacitance can still maintain 95.6%of the initial capacitance after 5,000 cycles at 8 mA/cm2.The prepared NiCo2O4@NiMn-LDH material shows that the composite of transition metal oxide and transition metal hydroxide into a core-shell structure material has great potential value(2)NiCoP@NiMn-P was obtained by one-step phosphating of the NiCo2O4@NiMn-LDH composite electrode material.The electrode material has a mass ratio capacitance of 367 mAh/g at l.5 A/g(2 mA/cm2),and it has excellent rate performance(when the current density is increased from 1.5 A/g to 15 A/g,the specific capacity retention rate is 89.9%),NiCo2O4@NiMn-LDH was successfully converted into NiCoP@NiMn-P using one-step phosphating method,and its electrochemical performance was improved.This provides a new method for preparing the positive electrode materials of supercapacitors with high electrochemical performance.In addition,it was assembled into NiCoP@NiMn-P//AC(activated carbon)flexible device,and the maximum energy density of the device is 36 Wh/kg,the maximum power density is 4737 W/kg.