Design And Fabrication Of Bimetallic Compound-based Composites And Their Application In Supercapacitors

In recent years,with the worsening fossil energy crisis and environmental pollution problems,it is of extraordinary significance to develop renewable clean energy sources and corresponding advanced energy storage devices.Of which,supercapacitors have drawn much attention and have been widely used in many fields due to their rapid charge-discharge rate,high power density,long service life,low maintenance cost and high reliability.Considering that the electrode material is the fundamental factor that affects the overall performance of supercapacitor,it is imperative to explore high-performance electrode materials with high specific capacitance and rate capability,excellent energy and power density,low cost and long cycle-life.In this dissertation,a series of functional nanocomposites based on bimetallic compounds were rationally designed and synthesized by soft chemical methods,and their electrochemical properties as supercapacitor electrode materials were investigated systematically.The relationship between the structure,morphology,composition of as-prepared nanocomposite materials and their electrochemical performance were deeply discussed.The main contributions of this dissertation can be described as follows:(1)Preparation and electrochemical properties study of manganese ferrite/carbon black/polyaniline ternary composite.A manganese ferrite/carbon black/polyaniline ternary nanohybrid(MCBP)was successfully prepared via a facile two-step strategy:ultrafine MnFe2O4 nanoparticles were uniformly loaded on the surface of acid-modified carbon black by solvothermal reaction,followed by the uniform wrapping of polyaniline film via in situ polymerization.Material characterization results showed that the MCBP ternary nanohybrid possesses unique strongly coupled nanostructure.Compared with the corresponding single component materials or binary hybrids,MCBP ternary nanohybrid displayed obviously enhanced electrochemical properties,including extraordinary rate performance and excellent cycling stability.A symmetric supercapacitor device based on the MCBP ternary nanocomposite also possessed superior rate performance and long cycle life with outstanding cycling stability.(2)Preparation and electrochemical performance study of carbon black/nickel cobaltite composite.A carbon black/nickel cobaltite nanocomposite(CB/NCO)was successfully fabricated via a facile two-step approach including chemical coprecipitation and follow-up annealing treatment.Material characterization results exhibited that the NiCo2O4 component in the as-obtained nanohybrid was stably existed in the form of ultrafine nanoparticles with high dispersion,and intimately coupled with carbon black substrate.Compared with pure NiCo2O4,CB/NCO nanohybrid displayed a significant enhancement in both specific capacitance and rate capability.An aqueous asymmetric supercapacitor(ASC)device was constructed with CB/NCO nanohybrid and activated carbon(AC)as the positive and negative electrode,respectively.The assembled device delivered high energy density and power density as well as an excellent long cycle-life and cycling stability.(3)Preparation and electrochemical performance study of nickel cobalt double hydroxide nanosheets arrays supported on Ni foam.Without adding any alkali sources,a series of acetate anion,intercalated nickel-cobalt layered double hydroxides(A-NiCo-LDHs)were successfully prepared by a facile one-step solvothermal reaction combined with the in-situ hydrolysis of precursor.Accordingly,a series of binder-free hybrid electrodes(A-NiCo-LDH/NF)were constructed by grow A-NiCo-LDHs nanosheets array on the nickel foam,which can be directly applied as electrodes for supercapacitors and avoid using polymer binders and conductive additives.Benefiting from the unique morphological structure and strong synergistic effects between the components,A-NiCo-LDH/NF hybrid electrodes possessed significantly enhanced electrochemical performance in comparison with corresponding powdery samples,including high specific capacitance,excellent rate performance and long-term cycling stability.(4)Preparation and electrochemical performance study of nickel cobalt sulfide nanosheets array supported on Ni foam.In this section,a facile two-step approach was developed to construct a binder-free electrode composed of interconnected nickel cobalt sulfide(NiCo-S)nanosheets array loaded on Ni foam(NiCo-S/NF),wherein NiCo-S/NF hybrid electrodes were obtained via an in situ sulfuration of above-mentioned A-NiCo-LDH/NF electrodes.Benefiting from the special highly open nanostructure and remarkable synergistic effects between the components,the optimized NiiCo1-S/NF hybrid electrode showed ultrahigh specific capacitance,outstanding rate performance and excellent cycling stability.An aqueous ASC device was assembled sing Ni-Co1-S/NF electrode and Nitrogen-doped graphene(NG)as the positive and negative electrode,respectively.The assembled device possessed considerable high energy density and power density,as well as outstanding long cycle-life and long-term cycling endurance.