Design,Preparation Of Carbon Based/Nickel Sulphide Nanocomposites And The Investigation On Their Electrochemical Properties

With the rapid development of industrialization,environmental pollution is increasingly acute,the research and development of renewable energy and energy storage technology is extremely imminent.Among many energy storage devices,lithium-ion batteries and supercapacitors are two more promising ones.Their electrochemical performance largely depends on the electrode materials.Therefore,in order to improve the performance of energy storage devices,the key is the research of high performance electrode materials.In this master thesis,carbon materials and nickel sulfide are the research objects,and the nanostructure of the composite is reasonably designed,giving full play to the synergistic effect of each component,so as to achieve the purpose of further optimizing the electrochemical performance of the energy storage device.The detailed studies are as follows:(1)Based on self-assembled three-dimensional carbon nanotubes(3D-CNTFs)substrate,the petal-like Ni₃S₂nanosheets have been successfully coated on 3D-CNTFs(Ni₃S₂@3D-CNTF)via a simple one-pot solvothermal method.Benefitting from the 3D porous network structure of carbon and abundant active sites of nanosized Ni₃S₂sheets,when Ni₃S₂@3D-CNTF composite were evaluated as anode materials for Li-ion batteries,it demonstrates a high reversible capacity of 968.2 mAh g^-1at 0.2 A g^-1,good rate performance of 524.1 mAh g^-1at 8 A g^-1,and long cycling stability of 93.6%capacity retention after 900 cycles at 4 A g^-1.(2)The self-assembled nickel(Ni)doped CNTFs(Ni-CNTFs)are used as the substrate,and as the source of Ni source.The Ni₃S₂particles were grown on Ni-CNTFs(Ni₃S₂/Ni-CNTFs)by the solvothermal reaction and in situ growth method.Ni₃S₂/Ni-CNTFs were synthesized by hydrothermal reaction and in-situ growth method.In the synthesis process,without an extra addition of Ni source,the growth of such Ni₃S₂nuclei formed will proceed on Ni-CNTFs substrate to naturally achieve inter-atomic bonding within the interfacial region,thus forming a well-adhered interface to be favorable for fluent charge transfer.In addition,CNTFs as the substrate not only improves the electrical conductivity and structural stability of the material,but also avoids the volume expansion of Ni₃S₂during charge/discharge.Hence,when Ni₃S₂/Ni-CNTFs was directly used as a supercapacitor electrode material,at the current density of 1 A g^-1,the specific capacity is as high as 614.4 m Ah g^-1.(3)Different morphologys of nickel sulfide(Ni S)on NH₄F and HNO₃respectively etched by carbon clothes(CC)have been successfully fabricated based on CC substrate,via solvothermal method.It was found that Ni S nanoparticals displaying plerogyra sinuosa-like structure grew on the surface of NH₄F etched carbon fibers(Ni S nanoparticals/CC),while,Ni S thin films forming Anthenea pentagonula-like structure distributed uniformly and continuously over the HNO₃etched carbon cloth substrate(Ni S nanosheets/CC).The composition and structure of the two composites were further analyzed,and the electrochemical performance of the two composite materials as the electrode material for the supercapacitor was measured,in order to explore the influence of the composite materials with different morphology on the electrochemical performance,which provided a reference for the structure construction of high-performance composite materials.