Synthesis And Electrochemical Properties Of Transition Metal Sulfides And Their Composite Materials

Transition-metal sulfides have attracted great attention for their applications in the fields of catalysts, supercapacitor and Li-ion batteries due to their unique physical and chemical properties. CuS and Cobalt sulfides with different stoichiometric compositions such as Co1-xS, CoS, CoS2, Co3S4and Co9S8have been considered as the most promising candidate for next generation anode materials of lithium ion battery due to their high electrical conductivity, high theoretical capacity, good thermal stability and environmentally friendly. In this work, Co1-xS, CuS, and Co1-xS@C, Co9S8-GNS, CoS/carbon cloth composite materials have been synthesized via hydrothermal and solvothermal methods, and the effect of structures and morphology on electrochemical properties have been analyzed.By utilizing different surfactants, various morphologies and structures of Co1-xS have been synthesized by hydrothermal method, and the function of surfactants in controlling particle shape and structure have been introduced. Furthermore, the electrochemical properties of Co1-xS with addition of CTAB and PVP have been investigated, respectively.The novel3D hierarchical flower-like Co1-xS architectures have been successfully synthesized via a hydrothermal process using trisodium citrate (Na3Cit) as chelating agent. The effect of concentration of the Na3Cit on the morphology of obtained nanocompo sites have been analyzed, a possible growth mechnism for this hierarchical flower-like Co1-xS have proposed on the basis of a series of time-dependent experiments. And the electrochemical properties of3D hierarchical flower-like Co1-xS and the Co1-xS microspheres synthesized without addition of Na3Cit have been compared.The Co1-xS@C composites have been synthesized via a hydrothermal process using glucose and the flower-like Co1-xS synthesized with addition of Na3Cit as start materials. The electrochemical properties of the composites have been discussed. The results indicate that the electrochemical properties couldn’t be improved by surface coating with carbon.A facile solvothermal process have developed for synthesising the Co9S8/graphene nanosheets (Co9S8-GNS) composite based on the presence of graphene oxide (GO), CoCl2·6H2O and thiourea. The crystalline structure and morphology of the as-prepared products have been characterized, and the results demonstrate that the Co9S8nanoparticles with the diameter of50-60nm are uniformly distributed on the creasy graphene sheets. And the composite can dramatically improve the cycle stability and rate capability of Co9S8as an anode material for lithium ion batteries. The hierarchial CoS nanowire/carbon cloth composite have been prepared by a two-step hydrothermal method. By using the hierarchial CoS nanowire/carbon cloth as both a new class of binder-free anode and current collecters to replace copper were fabricated, which displayed a high initial discharge capacity of4886mAh·g-1, and second discharge capacity reduced to1810mAh·g-1, but in the following charge/discharge process, it shows the good cycle performance.The CuS have been synthesized by hydrothermal method, and the effects of reaction temperature, reaction time and solvent on morphology hanve been studied. The uniform size and morphology of CuS microspheres with layer structure have been prepared via the hydrothermal process at200℃for24h using the mixed solution of deionized water and ethanol as solvent. The initial discharge capacity of CuS is much higher than that of previous reports.