Preparation And Characteristics Of Transition Metal Compound/Carbon-based Composite Electrode Materials For Supercapacitors

Supercapacitors possess numerous merits such as low internal resistance,high current efficiency and rapid charging rate as a new storage energy device.However,the low energy density limits the commercial application field of supercapacitors.Proverbially,the properties of supercapacitors are directly dependent upon the properties of electrode materials.Among them,transition metal compounds have attracted much attention due to the high theoretical specific.However,the low intrinsic conductivity and large volume expansion have become the key restraints on its application.In this paper,the preparation technology of electrode materials is optimized to prepare supercapacitors with better performance from two aspects of how to prepare composite materials with excellent performance and expand the working voltage.The main research works of this thesis are as follows:(1)The composite materials of activated carbon nanotubes(ACNTs)and nickel sulfide(Ni S)nanoparticles were successfully synthesized by simple hydrothermal reaction and low temperature annealing treatment.Meanwhile,the electrochemical performance of Ni S/ACNTs composite electrode was detailedly studied in KOH electrolyte with different molar concentrations.It is found that ACNTs are used as a good conductive carrier for the deposition of Ni S,effectively alleviating the agglomeration of Ni S nanoparticles,which is conducive to the improvement of electrochemical performance.Due to the synergistic effect of battery-type materials and electrical double layer capacitive(EDLC)materials,the Ni S/ACNTs electrode exhibits a high specific capacitance of 1068 F g^-1at a current density of 8.0 A g^-1.The assembled Ni S/ACNTs//AC ASCs deliver a favourable energy density of 13.3 Wh kg^-1at a power density of 6.8 k W kg^-1.(2)The NiS/MoS₂/GR composites were prepared by growing mixed phase Ni S/Mo S₂/GR nanocomposites on graphene sheets via a simple one-step hydrothermal and calcination method.In the mixed phase of Ni S/Mo S₂,Ni and S directly form Ni-S coordination bond,which supplies enough active sites and is beneficial to the improve performance.Based on the advantages of nanostructure composite composition,the Ni S/Mo S₂/GR delivers a high specific capacitance of1028 F g^-1at a current density of 1.0 A g^-1.In addition,Ni S/Mo S₂/GR//AC ASCs assembled with Ni S/Mo S₂/GR composites as cathode and AC as anode have a high energy density of 20.7 Wh kg^-1and a good cycling performance.(3)The KOH-activated biomass-derived porous carbon(BPC)were synthesized via carbonization and KOH activation using water caltrops as a carbon source.The Ni Co-LDHs/BPC composite materials were successfully prepared through a facile one-step solvothermal method according to different nickel-cobalt molar ratios.BPC with high specific surface area(SSA)and good electrical conductivity is an ideal conductive body for direct deposition of homogeneous Ni Co-LDHS materials.Due to the synergistic effect between Ni Co-LDHs-1 and BPC,the prepared Ni Co-LDHS-1/BPC electrode exhibits a high specific capacitance of 2047 F g^-1at a current density of 1 A g^-1.In addition,the Ni Co-LDHs-1/BPC//BPC/PPy ASCs delivers a high specific capacitance of 139 F g^-1at 1 A g^-1,a high energy density of 49Wh kg^-1.