Preparation Of Carbon Materials And Carbon-Based Composite Materials And Their Applications In Supercapacitors

Nowadays,energy problems have become the greatest focus attracting the world's attention and triggering tremendous efforts for energy storage and conversion.Owing to excellent cyclic stability,high energy density,superior power density,and environmental friendliness,electrochemical capacitors are considered as an ideal energy storage system.Supercapacitors can be divided into carbonbased double-layer capacitors and transition metal oxide or conductive polymer based pseudocapacitors.The capacitance performance,rate capability and cyclic stability are key parameters to investigate whether its performance is excellent for different supercapacitor electrode materials.These key parameters are closely related to the mechanical properties,specific surface area and pore structure of the materials.In addition,for the pseudocapacitor electrode materials,exposure of active site also has a great influence for capacitance performance.In the thesis,supercapacitor electrode materials with good mechanical properties,large surface area,porous structure and high exposure to active sites are prapared through material modification,template and other methods.This thesis is divided into three sections.3D N-doped mesoporous graphene?N-3DMG?is fabricated by using polyamide grafted graphene oxide as the precursor.The functionalization of graphene oxide not only avoids restacking of graphene sheets when graphene oxide is reduced,but also provides nitrogen source for the N-3DMG.When the N-3DMG is used for supercapacitor,it exhibits excellent specific capacitance,rate capability and cyclic stability.The 3D mesoporous structure and high N-doping content are believed to be responsible for the high capacitive performances.A new-style Co₃O₄/C@MoS₂ core-shell structured material is synthesized via a two-step calcinations and a solvothermal method using cobalt metal-organic frameworks?cobalt-MOFs,ZIF-67?and?NH₄?₂MoS₄ as the precursor of Co₃O₄/C and MoS₂,respectively,which is a new class of core-shell materials as supercapacitor electrode materials.The obtained Co₃O₄/C@MoS₂exhibits high specific capacitance,rate capability and cyclic stability.Moreover,the content of MoS₂ greatly influences the electrochemical performances of the obtained core-shell materials.The results demonstrate that the as-synthesized ZIF-67 can be used as a promising candidate for designing Co₃O₄ based core-shell materials used in supercapacitors.WO₃/polypyrrole?PPy?/graphene?G?composites are synthesized stepwisely by using attapulgite as the template.Because of the introduction and removal of the template,the composites have a regular morphology and holy structure.The addition of G and PPy can effectively enhance the electrical conductivity and mechanical property of the composites,greatly improving the capacitive performance of WO₃.Therefore,the WO₃/PPy/G composites exhibit excellent specific capacitance,rate capability and cyclic stability compared to single component.