Applications Of Pitch-derived Ordered Mesoporous Carbon-nickel Sulfide Composites For Efficient Lithium Storage

Lithium-ion batteries have inherent advantages such as high energy/power density,low power consumption,high cost performance,and environmental protection,which are widely used in electronic products,electric vehicles,smart grids,aerospace and other fields.Since the energy density of traditional lithium-ion batteries is restricted by graphite anode materials,new anode lithium storage materials with high capacity,excellent rate performance,environmental friendliness,and low cost are in urgent need of development.Nickel sulfide has the advantages of abundant resources,strong thermal stability and high theoretical lithium storage specific capacity,but its electronic and ionic conductivity is poor,and its particles are easy to agglomerate as well as pulverize during the lithium storage process,which still need the further optimization and modification.Therefore,this thesis takes nickel sulfide as the research object,and realizes the improvement of the above problems through composite mesoporous carbon.First,the preparation method was optimized to realize the effective composite of nickel sulfide and mesoporous carbon;then the electronic structure of the electrode material was adjusted by in-situ doping of iron atoms,the phase transition process was stabilized,and the electrical conductivity of the composite material was improved.Finally,through the adsorption of the dispersant,the particle size of nickel sulfide is reduced,so that it can be evenly distributed on the carbon skeleton,and the diffusion and transmission distance of lithium ions in the electrode is shortened.A series of nickel sulfide-mesoporous carbon composites with good lithium storage properties were obtained in the end.The sepecific research contents are as follows:（1）Research on the preparation and lithium storage performance of Ni₃S₂/mesoporous carbon composites.Using pitch as the carbon source,SBA-15 as the template,and nickel diethyldithiocarbamate as the metal source and sulfur source,the nickel sulfide loading was realized in situ while the surface was anchored to the template and carbonized.The effects of different mixed solvents on the morphology,structure and lithium storage performance of the materials were investigated.The nickel sulfide-mesoporous carbon composites prepared with carbon disulfide as the solvent maintained a capacity of 713.2 m Ah g^-1when cycling 200 cycles at a current density of 0.2 A g^-1.（2）Research on Ni S/mesoporous carbon composites and their lithium storage performance regulated by Fe-doped Controlling.Ferric acetylacetonate was added as an iron source during the preparation of the nickel sulfide-mesoporous carbon composite material to realize the in-situ iron doping of the composite material.The structure of the composite is optimized after iron doping,and the lithium storage performance is extremely enhanced,and the capacity can reach 1307.1m Ah g^-1when cycling 200 cycles at a current density of 0.2 A g^-1.Iron doping can inhibit the growth of Ni₃S₂particles.At the same time,the surface carbon graphitization degree and electrical conductivity of the material are improved,and the mesoporous carbon layer spacing is widened,which is conducive to the diffusion and transport of Li⁺in the bulk phase,and alleviates the volume effect and polarity phenomenon of the conversion reaction.（3）Research on Ni₃S₂/mesoporous carbon composites and their lithium storage performance regulated byβ-cyclodextrin dispersion.A series of composite materials were prepared through high temperature carbonization and de-template treatment by usingβ-cyclodextrin as dispersant.Meanwhile,the role ofβ-cyclodextrin in the preparation of materials was studied.The obtained material has a structure in which carbon nanofibers are staggered on the surface of mesoporous carbon,and the in-situ grown Ni₃S₂particles are uniformly dispersed on the mesoporous carbon framework.Among them,Ni₃S₂/C-CD（1/50）as the anode material of lithium ion battery can reach 855.6 m Ah g^-1when cycling 200 cycles at 0.2 A g^-1current density,and it can maintain a specific capacity of 891.5 m Ah g^-1even after 1000 cycles at 0.5 A g^-1.