Study On The Building Of Nanostructured Ni（OH）₂/MWCNTs Composites And Their Electrochemical Performance

Nickel hydroxide is one of the widely used electrode materials for application in supercapacitors due to its high theoretical specific capacitance.However,the low conductivity of nickel hydroxide results in its poor high rate performance.Muti-walled carbon nanotubes（MWCNTs）have excellent electrical conductivity and can carry high current density.Therefore,different methods were used in this dissertation to combine MWCNTs with Ni（OH）₂ to form nanostructured composites.The conductivity and electrochemical performance of Ni（OH）₂ was thus improved due to the synergistic effect of MWCNTs and Ni（OH）₂.The main experimental results are listed as follows:（1）In-situ assembly of nanostructured MWCNTs/Ni（OH）₂:The homogeneous mixture of MWCNTs and NiCl₂?6H₂O with different mass ratios was ground in a mortar to form the NiCl₂?6H₂O/MWCNTs working electrode.Then,theβ-Ni（OH）₂ nanosheets were in-situ formed in the current collect after the electrochemical activation of electrode in 3 M KOH.The as-preparedβ-Ni（OH）₂ nanosheets had more higher specific capacitance of 2001.4 F g^-1 at lower current density of 3.2 A g^-1 and 429.7 F g^-1 at high current density of 28.0 A g^-1.（2）Self-assembled of nanostructured MWCNTs/Ni（OH）₂:Ni（OH）₂ and modified MWCNTs were combined closely through the electrostatic attraction.The as-prepared30 wt%MWCNTs/Ni（OH）₂ composite had a specific capacitance of 1568.8 F g^-1 at low current density of 2.4 A g^-1 and 1052.6 F g^-1 at high current density of 48 A g^-1.The specific capacitance of composite remained 95%of its original value after 4000 cycles,which proves the high cycle stability of composite.（3）In-situ growth of nanostructured MWCNTs/Ni（OH）₂ composites:In order to combine MWCNTs with Ni（OH）₂ closely,Ni²⁺was adsorbed on the surface of modified MWCNTs at 40?C in water bath.The Ni（OH）₂ was grown in situ on the surface of modified MWCNTs to form Ni（OH）₂/MWCNTs composites.This method further simplified the synthesis process and improved the electrochemical performance of Ni（OH）₂.The composite had a specific capacitance of 2400 F g^-1 at low current density of2.6 A g^-1,and remained a high value of 1000 F g^-1 at high current density of 53.4 A g^-1,The supercapacitors composed with composite as electrode exhibited a high energy storage performance:it had the energy density of 44.68 Wh kg^-1 at power density of283.69 W kg^-1.