Synthesis Of Transition Metal Sulfides And Their Application In Lithium-ion Battery

Transition metal compounds have been considered as promising electrode materials for lithium-ion batteries (LIBs) because of their excellent electrochemical performances. Among them, metal sulfides have attracted much attention owing to their high capacities.In this dissertation, a series of nanostructural transition metal sulfides were synthesized by a simple electrodeposition route. And we compared their electrochemical properties by different synthesis process、different synthesis method、 compositing with organic compounds and so on. Furthermore, nanostructural metal sulfides were used as electrodes for Li-ion intercalation, and the relationships between the electrochemical properties and the intrinsic characteristics of these mateials were also investigated in detail. The main contents and results are as following:(1) Porous NiS nanoparticles on Ni foam substrate were synthesized via an electrodeposition route. It was found that the size of these nanoparticles were found to be ca.100-200 nm, and they were also distributed on the Ni foam substrate. Furthermore, these materials were used as the electrode in LIBs and their properties were also investigated. For instance, a discharge capacity of 0.092 mAh cm-2 (～550 mAh g-2) was reached at a current density of 0.1 mA cm-2 after 50 cycles, corresponding to 93.2% of its second discharge capacity.(2) CoS nanomaterials were synthesized respectively by using an electrodeposition rout and a hydrothermal method. It was found that the obtaind CoS were porous nanosheets with a thickness of 200-300 nm and a width of 10 nm. The cell made of CoS nanosheets exhibited a discharge capacity of 0.123 mAh cm-2 after 100 cycles at a current density of 0.1 mA cm-2. However, the cell composed of CoS obtained from a hydrothermal route showed a poor electrochemical performance.(3) The composites composed of MoS2 and PANI were synthesized by using a two-step electrodeposition rout. It was found that the electrochemical properties of MoS2 were efficiently enhanced after electrodeposition with PANI layer. For example, when the electrodeposition cycles were 20,10,5 and 0, the Coulombic efficiencies of the initial cycle were respectively 75.4%,71.7%,75.8% and 62.7% at a current density 0.2 mA cm-2, and the capacity retention of 49%,52%,57% and 40% was also be kept, respectively. In a word, the electrochemical performance of materials composited with PANI can be improved greatly.