Study On High Performance Manganese Cobalt Based Oxides And Sulfides Electrode Materials For Supercapacitors

Supercapacitor is an effective energy storage device which can output and input electric energy at high power density and it has a promising prospect in the fields of smart grid,rail transit,high power weapon,etc.However,low energy density hinders its wide application.With respect to the low specific capacitance of supercapacitor electrode materials,developing structure design and property adjustment of transition metal oxides and sulfides,selecting four varieties of electrode materials with high faradaic capacitance,revealing the relationship between microstructure,surface morphology,specific surface area,distribution of pores,crystallinity,states of elements,conductivity and electrochemical performance,acquiring electrode materials with high specific capacitances.This offers theoretical foundation and new strategies for synthesizing innovative energy storage device with high power density,high energy density and long life.Specific contents are as follows:?1?Using precipitation method to produce MnO₂ amorphous nanoparticles and investigating the influence of annealing temperature on morphology,crystallinity and electrochemical properties.A lower annealing temperature leads to poor crystallinity of MnO₂,higher specific surface area and higher specific capacitance.The specific surface area of amorphous MnO₂ could reach 189.4m²/g and the specific capacitance is 170 F/g at 1 mV/s.?2?Modifying manganese oxide precursor to synthesize Mn₃O₄@C core-shell nanorod composite and studying the influence of modification on electrochemical properties of electrode materials.The thin,conductive and amorphous carbon layer on the surface of Mn₃O₄@C core-shell nanorod could facilitate the transportation ability of ions.Meanwhile,polycrystals of Mn₃O₄improve the penetration ability of ions in electrolyte,inducing a better electrochemical properties of Mn₃O₄@C core-shell nanorod than manganese oxide precursor.After 5000 cycles at 4 A/g,the retention of Mn₃O₄@C is 95%,implying an excellent cycling ability.?3?Studying on the relationship of different ratios of potassium permanganate and aniline with the electrochemical performance of resulted MnO₂-polyaniline?MP?nano-reticulation composite.With more aniline is used,the weight mass fraction of MnO₂ improves,the weight mass fraction of aniline drops and the charge transfer resistance of MP climbs up.The special nano-reticulation structure of MP composite facilitates the contact between active material and electrolyte and the electrons could transfer fast and easily in the conductive polyaniline skeletons,ensuring robust and immediate electrochemical reactions.The highest specific surface area of MP material is 480 m²/g and the specific capacitance could reach 497 F/g at 1 mV/s.?4?Cobalt sulfide hierarchical porous nanospheres?CoS-HPNs?are fabricated through two-steps solvothermal reactions successfully.Brownian snowball mechanism is put forward to explain the formation mechanism of cobalt sulfide HPNs,which is supported by first-principles calculations.The triangular relationship between specific capacitance,sulfidation time and specific surface area is carefully studied.The capacitance of cobalt sulfide are composed of double-layer capacitance and Faradic capacitance simultaneously.CoS-9h sample has the highest specific surface area of 145 m²/g and its specific capacitance is 932 F/g at a current density of 5 A/g.