| Layered double hydroxides?LDHs?are well known as anionic or hydrotalcite-like compounds.LDHs have received extensive attention due to their high surface area caused by the layered structure and the diversity of different metal ions.In particular,the type and proportion of anion between the layers and layers of the LDHs are adjustable,and the structural flexibility is very high.It shows excellent performance in the fields of electrochemistry,electrocatalysis,adsorption and antibacterial,etc.,especially as a kind of extremely promising psedocapacitor electrode material,it has a good application potential.In this thesis,LDH was prepared by sol-gel method,and its structure and characterization were regulated.Based on this,LDH/conductive polymer composite electrode material with controllable structure was designed and prepared.Conductive polymers?polypyrrole,polyaniline,and polythiophene?were used as substratum to conduct vertical growth of LDH.At the same time,nano-channels for high-speed transmission of electrons and electrolyte ions were constructed on the microscopic scale,and the structure of LDH/conductive polymer composite electrode materials was investigated.A synergistic enhancement effect between LDH and conductive polymers was found.The results of the study showed that conducting polymers can significantly increase the electronic conduction rate of LDH.The specific capacitances of polypyrrole@LDH,polyaniline@LDH and polythiophene@LDH were 2187.1 F·g-1,2298.1 F·g-1 and 1938.5 F·g-1,respectively,at the current density of 1 A·g-1.These values were significantly higher than that of pure NiAl-LDH(762.5 F·g-1 at a current density of 1 A·g-1).In addition,the polypyrrole@LDH had the highest specific capacitance retention rate of 62.9%at a large current density of 20 A·g-1,indicating that it had the optimal capacitance performance.In order to further improve the performance of the supercapacitor,the three components of graphene,polypyrrole,and LDH were composited.Firstly,polypyrrole was coated on the surface with graphene as a substrate,and then the structure of LDH/graphene/polypyrrole composite material was optimized on the microscopic scale.The graphene/polypyrrole composite with high conductivity was fabricated.LDH not only provided nanochannels for the high-speed transmission of electrons and electrolyte ions,but also served as a structural support,helping to improve the capacitive properties of electrode materials.Electrochemical tests showed that the specific capacitance was as high as 2394.9 F·g-1 at a current density of 1A·g-1,and it could maintain 1719.6 F·g-1 even at a high current density of 20 A·g-1.At the same time,and the specific capacitance did not show any decay after 10,000 times charge-discharge cycle at the current density of 10 A·g-1.These results showed that the composite material not only had high specific capacitance,but also had excellent rate characteristics and ultra-high cycle stability.It was proved that there was a strong synergistic effect between graphene,polypyrrole and LDH,which provided a new basis for the preparation of excellent ultracapacitor electrode materials. |
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