The Design And Synthesis,as Well As The Capacitive Performances Of Metal Sulfide And Nitrogen Doped Carbon Materials

Supercapacitors represent a category of green,efficient,safe and long lifetime energy devices owing prominent advantages in rate capabilities and power densities,therefore can be potentially applied as power delivery and charge-discharge speed oriented power sources for start-up and shut-down devices,auxiliary power supplies,pulse facilities and portable electronics.Electrode material is the major arena where the charge storage and migration occur,the designing of efficient faradic electrode materials with optimized electrons/ions migration channels and structural tenacities and the asymmetric devices assembly manner are the key approaches to enhance the charge storage capacities,energy densities and cycleabilities of supercapacitors,which are also the major investigation and application focus in this fields.Metal sulfides are a significant type of faradic materials with high faradic acitvities and narrow optical band gap energy,therefore can offer high specific capacitances.The synthesis of bimetallic sulfides,sulfides based heterostructures and composites can further improve the faradic activities of sulfides electrodes throught the interactions between different elements and components.Furthermore,the construction of hierarchical architectures can enhance the specific surface areas,electrons/ions conductivities and structural tenacities of active materials,therefore can comprenehsively improve the charge storage capacities,rate capabilities and cycleabilities of sulfids electrodes,thus enable the fabrication of efficient and long lifetime supercapacitors.In this thesis,the design and preparation of bimetallic sulfides,heterostructural sulfides and composites with different archtectures and the resultant applicational performances in asymmetric supercapacitors were involved.Additionally,nitrogen element doped carbonaceous materials were also synthesized,characterized and the capacitive performances were analyzed,so as to improve the power delivery ability of asymmetric supercapacitors by virtue of the electric double layer capacitive feature.The total content of this thesis are summarized as follows:1.Co Ni₂S₄-rGO composite active electrode was prepared by tandem deposition of CoNi₂S₄ and reduced graphene oxide?rGO?onto Ni foam substrate via a two-step hydrothermal procedure,the rGO coating layar onto CoNi₂S₄ nanoarrays can obviously improve the cycleability of the electrode without sacrificing of total charge storage capacity.The CoNi₂S₄-rGO composite electrode can offer a high specific capacitance of 1988 Fg^-1 at 1 Ag^-1,and decent rate capability and cycleability were achieved simultaneously.The asymmetric supercapacitor?ASC?based on the CoNi₂S₄-rGO electrode and carbon ink derived porous carbon electrode,denoted as CoNi₂S₄-rGO//AC ASC,can offer a wide voltage window of 1.6 V,therefore can deliver a high energy density(E_cell)of 52 Whkg^-1 and good cycleability,thus can be used as high E_cellell and long lifetime capacitive device.2.Porous Co₃S₄@Ni₃S₄ heterostructured composite arrays electrode was prepared by hydrothermal deposition of Co precursor nanowires arrays onto Ni foam substrate,followed by sulfidation treatment and coating using Ni foam as current collector and Ni source for sheath layer.The Co₃S₄@Ni₃S₄heterostructured arrays electrode can provide high areal capacitance(3.6 Fcm^-2 at 0.8 mAcm^-2),considerable rate capability and cycleability.The Co₃S₄@Ni₃S₄//PC ASC based on this heterostructured porous arrays electrode offers an areal capacitance of 0.513 Fcm^-2(2 mAcm^-2),therefore is capable of delivering E_cells of 0.18⁰.035 mWhcm^-2 within power density range of 1.39⁶3.3 mWcm^-2,and slow self-discharge behavior and good cycleability can also be ensured simultaneously.3.3-dimensional network Co₃O₄@Ni₃S₄ composite active layer assembled by interconnected laminar primary units were deposited onto Ni foam current collector by hydrothermal deposition of Co₃O₄ and the subsequent sulfidation deposition of Ni₃S₄.Electrochemical tests showed that the Co₃O₄@Ni₃S₄ network electrode chan offer a high areal capacitance of 4.92 Fcm^-2 at 1 mAcm^-2,and 0.94 Fcm^-2 can still be preserved with the current density increased to 30 mAcm^-2.4.Fullerent soot was used as carbon motif for preparation of N doped porous carbon microspheres by doping of different N source and the followed activation treatment.This type of N doped carbonaceous materials demonstrated high electrochemical and electrocatalytic activities.The influences of doping and activation treatment temperature and the N element content on the capacitive performance of electrode were investigated in acidic electrolyte,high specific capacitance of 230 Fg^-1(1 Ag^-1)can be offered by the N doped carbon material,therefore can be employed as high capacity carbonaceous electrode material.