Preparation And Electrochemical Properties Of Carbon Nanotubes/layered Double Hydroxide Nanocomposite Material

The demand for energy is rapidly growing in modern life.The high-performance and green energy storage devices have gained significant attention.Supercapacitors are considered as novel energy storage devices due to their advantages of fast charge-discharge,high power density,long cycle life and security and so on.The performance of the supercapacitor mainly relies on electrode material.LDHs are widely used in supercapacitor electrode materials because of their high specific capacitance,high reversible charge-discharge capacity,high anion exchange capacity,multiple reversible redox sites and low cost.Introducing carbon material to LDHs could effectively combine the redox reactive property of LDHs with the high conductivity,high stability of carbon materials.It is an effective way to improve the system conductivity and electron transport capabilities.Finally,the nanocomposite of LDHs and carbon materials remarkably improve the electrochemical characteristics.In this thesis,CNTs/NiAl-LDH and CNTs/CoNiFe-LDH nanocomposites were prepared by a facile one-step homogeneous precipitation method.The morphology,structure and electrochemical properties of the nanocomposite were then systematically studied.The CNTs/NiAl-LDH nanocomposite exhibited a high specific capacitance of 694 F g-1 at 1 A g-1.The specific capacitance of the CNTs/NiAl-LDH nanocomposite still retained 87% when the current density was increased from 1 to 10 A g-1.These results indicated that the CNTs/NiAl-LDH nanocomposite displayed a higher specific capacitance and rate capability than NiAl-LDH.Furthermore,the capacitance of the CNTs/NiAl-LDH nanocomposite kept at least 92% after 3000 cycles at 20 A g-1,suggesting excellent cycling durability.The result indicated that the participation of CNTs improved the electrochemical properties of the CNTs/NiAl-LDH nanocomposite.The CNTs/NiAl-LDH nanocomposites exhibit excellent electrochemical properties,especially the cycling stability at a high current density.It can be used as one of candidate electrode materials for supercapacitor.A novel electrode material of CNTs/CoNi Fe-LDH exhibited a higher specific capacitance of 1045 F g-1 at 1 A g-1 and a superior rate capability of 73% at 20 A g-1.The specific capacitance and rate capability of CNTs/CoNiFe-LDH were superior to CoNiFe-LDH under the same conditions.Additionally,the CNTs/CoNiFe-LDH displayed an excellent electrochemical stability with specific capacitance retention of 80% at 20 A g-1 after 1000 cycles.The result indicated that the novel CNTs/NiAl-LDH nanocomposites exhibit excellent electrochemical properties.It can be used as one of candidate electrode materials for supercapacitor.