Synthesis Of Molybdenum Sulfide And Copper Oxide Nanostructures And The Investigation Of Their Electrochemical Properties

The main objective in this thesis is about3d metal oxides and sulfides as anode materials for lithium batteries showing low initial coulomb efficiency, poor cycle performance, and large loss of the irreversible capacity. We have chosen molybdenum sulfide, cooper oxide as the research objects, and developed several methods to improve the cycle stability of the battery and coulomb efficiency by preparing nanostructured materials and graphene-based composites. Compared with bulk materials, nanoscale materials have unique properties, which have a broad application prospect in the filed of electrochemical sensor.In this paper, we have prepared different copper oxides and CuO/graphene hybrid nanomaterials. We have also studied the electrochemical properties of CuO-modified electrodes for non-enzymatic hydrogen peroxide sensors. The main research contents and the results are as folowing:1. Preparation of molybdenum disulfide nanomaterials for Li-ion battery application(1) Synthesis of flower-like molybdenum disulfide for Li-ion battery applicationThree-dimensional flower-like molybdenum disulfides composed of nanoflakes were synthesized by hydrothermal process using sodium molybdate and thioacetamide as reactants. The morphology and microstructure of the products have been characterized by XRD, SEM, TEM, and HRTEM. Besides, the electrochemical performance of the prepared product as Li-ion battery electrode has been investigated, which exhibits the specific capacity of-1342.8mAh/g. which is higher than nubbly molybdenum disulfide, The unique structures of molybdenum disulfide nanoflakes make them be the most promising alternative anode materials for lithium-ion batteries.(2) Synthesis of MoS2/graphene composite materials for Li-ion battery application.Using the graphene oxide with oxygen functional groups as precursors of graphene, nanoflakes MoS2/graphene composite is synthesized by hydrothermal method using sodium molybdate and thiourea as reactants. We found that when we use this composite as anode materials, the cycle stability of the battery performance has been improved, this is because graphene can enhance the electronic conductivity of MoS2and can be buffer in the composite. Electrochemical test result also shows that the composites show obvious synergistic effect, makes the capacity of the composite significantly greater than pure MoS2electrode and pure graphene electrode and the capacity of both. For example, MoS2/graphene composites show the reversible capacity of583.5mAh g-1after50cycles with the current density of67mA g-1, corresponding to75.5%of the first charging capacity.2. Preparation of cooper oxide nanomaterials for electrochemical application(1) Rapid microwave-assisted synthesis of ball-in-ball CuO microspheres and application as a H2O2sensorIn this part, we have synthesized ball-in-ball CuO microspheres by a one-step microwave-assisted process using Cu(NO3)2·2H2O, NH3·H2O,0.1M NaOH solution and anhydrous ethanol as raw materials. Compared with other synthesis methods, this approach is very quick (10min), low cost, non-toxic and no any surfactant. XRD, SEM, TEM and SAED technology were used to analysis microstructure. The result shows that copper oxide has "ball-in-ball" morphology, and the formation mechanism for the ball-in-ball CuO architectures has been discussed. The material has aslo been studied as hydrogen peroxide sensor.(2) Preparation of CuO/graphene and the application in Li-ion batteryWe have synthesized different CuO/graphene composite with NH3-H2O、 Cu(CH3COO)2·H2O and GO produced by Hummers method as raw materials. We get about80-100nm rhombic CuO/graphene and5nm granular CuO/graphene composite by microwave method with low power and short time. The morphologies of as-prepared products were studied by XRD, SEM, TEM. Besides, the electrochemical performances of the two prepared products as Li-ion battery electrode have been investigated.