Hydrothermal Synthesis And Electrochemical Properties Of Metal Sulfides （FeS₂and MoS₂）

The main purpose of this research is to explore new metal sulfides electrodematerials for lithium ion secondary battery．Natural pyrite FeS2as the electrodematerials of1.5v lithium battery．In recent years, there has been increasing interestin FeS2electrode material for lithium ion batteries because of its high theoreticalcapacity(890mAhg-1)，low cost and non-toxicity．Molybdenum disulfide is a typeof grapheme structure of layered compounds and its layers is advantageous toprovide more space for lithium ion embedded．XRD，SEM，TEM，charge-dischargetest，cyclic voltammograms and AC impedance have been carried on thepreparation，morphology and structure characterization，to the electrode materialmodification and the performance．This research mainly divided into two parts：First，By hydrothermal of FeS2electrode material， produced Li/FeS2button oftest battery to study the discharge characteristics under different current densities.And glucose in the hydrothermal synthesis process to carbon-coated，be modifiedto study the discharge performance at different current densities．Studies haveshown that the hydrothermal synthesis of FeS2that significant improvement incycling performance after conducting carbon-coated．The effects of currentcollectors on the electrochemical performance of FeS2electrode have beeninvestigated by applying three types of current collectors，including an Al foil，aCu foil and a Ni foil．The results show that Ni current collector can greatlyimprove the discharge capacity and cycle ability of FeS2electrode compared to theAl current collector．The results are not limited to the FeS2electrodes，can beextended to other metallic sulfide electrodes．Second，this study using hydrothermal synthesis of molybdenum disulfide，by changing the hydrothermal conditions，different morphology of molybdenumdisulfide was synthesized. In the solution of PH value is less than1with thesurfactant PVP(Polyvinylpyrrolidone)，the molybdenum disulfide nanoparticleswas prepared and its electrochemical performance was tested，under the currentdensity of100mA g-1, the initial discharge specific capacity can be as high as 1915.1mAh g-1，after20cycles can remain744.8mAh g-1．And without the PVP，under the current density of100mA g-1，the initial discharge specific capacityonly1096.1mAh g-1，after20cycles the specific capacity is675.5mAhg-1．Battery capacity improvement may be associated with the particle size ofmolybdenum disulfide，the smaller the particle size，and the smaller lithium ionmigration path，help to lithium ion embedded．In the buffer PH=4，preparationof the is by the layer assembly into flowerlike molybdenum disulfide．With thePVP synthesis of nanometer is a solid ball．On the same charge and discharge test，the test results show that the flowerlike molybdenum disulfide of theelectrochemical properties is better than that of spherical. The improvement of theperformance of the electrode materials is related to flower appearance．Thecombination of nanosheeets not only increase the surface contact between theelectrode and the electrolyte，provide more space for lithium ions embedded, butalso effectively shorten the lithium ion migration path．...