Preparation And Properties Of Nickel-doped Manganese Dioxide/Conductive Polymer Composite Electrode Materials

Manganese dioxide has attracted much attention in the field of supercapacitors because of its abundant sources,low prices,environmental friendliness,and higher theoretical capacity.However,poor conductivity,rate performance,and cycle stability severely limit its application.In order to improve the electrochemical performance of Mn02,three series of Mn02-based electrode materials are synthesized by modifying MnO₂ with using sol-gel method,in-situ polymerization method and in-situ gel method respectively,and the infrared spectrum?FT-IR?and Raman spectrum?Raman?,X-ray diffraction?XRD?,scanning electron microscope?SEM?,transmission electron microscope?TEM?,cyclic voltammetry?CV?,constant current charge and discharge?GCD?,and electrochemical impedance spectroscopy?EIS?to measurement the structural and electrochemical properties of materials.The sol-gel method is used to prepare nickel-doped manganese dioxide.The results demonstrate that the crystal structure of MnO₂ is ?-MnO₂ before and after doping with Ni.When the molar ratio of Ni and Mn is 0.03:1,the particle size of sample NMO-3 is 60 nm and the specific surface area is 82 m2/g.At a scan rate of 2 mV/s,the specific capacitance of the sample reaches a maximum of 221.39 F/g,which is an increase of 54.97%over that of undoped sample.At a current density of 0.5 A/g,the specific capacitance of NMO-3 is 138.07 F/g.After 2000 charge and discharge cycles,the specific capacitance of NMO-3 remains at 75.02%?Ni-MnO₂/PANi-co-PPy composites are synthesized by in-situ polymerization method.The results show that the copolymer layer is coated on the surface of Ni-MnO₂ to form core-shell structure,and the thickness of the PANi-co-PPy coating layer is 100 nm approximately.When the mass ratio of Ni-MnO₂ to aniline and pyrrole mixed monomer is 1:5,the specific capacitance of the NMP-5 reaches a maximum value as high as 445.49 F/g at a scan rate of 2 mV/s,which is twice than that of Ni-MnO₂.At a current density of 0.5 A/g,the specific capacitance of the NMP-5 is 385.67 F/g.After 5000 cycles,the specific capacitance of NMP-5 decreases to 61.65%of the initial value.The MnO₂/PPy/SLS ternary composites are synthesized by in-situ gel method.The results demonstrate that the addition of MnO₂ and SLS components cannot significantly affect the chemical structure of PPy.Without adding SLS,PPy grows on the surface of MnO₂ microspheres in an orderly manner to form sea urchin structures with a diameter of about 5 ?m,while after adding SLS,the morphology of the composites become nano size paticles with an average particle size of about 100 nm.When the molar ratio of Mn to pyrrole monomer is 1:5,and the mass ratio of SLS to pyrrole monomer is 10%,the specific capacitance of MPS-5-10%is 482.86 F/g at a scan rate of 2 mV/s.While at a current density of 0.2 A/g,the specific capacitance of MPS-5-10%is as high as 665.80 F/g.After 2000 cycles,the specific capacitance of MPS-5-10%reduces to 71.69%of the initial value.