Preparation And Electrochemical Properties Of Molybdenum Disulfide And Its Carbon Composites

With the continuous consumption and the incomplete combustion of non-renewable energy sources, the world is facing energy crisis and the serious problems of environmental pollution. However, as a kind of efficient and clean new energy storage device, the use of lithium ion batteries has received much attention. As a typical transition metal sulfides, MoS2 has an analogous structure to graphite. The interlayer space can provides an unusual environment to accommodate a variety of guest species such as Li+. And the theoretical specific capacity is almost twice as high as graphite. Therefore, MoS2 was investigated in some early studies as anode material for lithium ion batteries instead of graphite. However, the cycle stability of MoS2 is much worse than graphite due to its low electronic/inoic conductivity and its serious volume expansion effect during charging and discharging process. In addition, during the cell reaction, MoS2 can react with Li+ to form insoluble Li2S, and Li2S catalyze the decomposition of electrolyte to form a thick polymer layer that leads to irreversible capacity loss. In consequence, how to improve the cycle stability of MoS2 and keep its high capacity is becoming a key problem of MoS2 when it is used as anode material of lithium ion batteries.In this paper, on the one hand, we combine the carbon and MoS2 together to form MoS2/C composities to improve the electrochemical properties. On the other hand, we change the microstruture of materials to increase the lithium storage capacity and reduce the volume expansion effect of materials. The main research contents include:(1) Through a simple hydrothermal method, using glucose, sucrose and soluble starch as different carbohydrate organic carbon source, we synthesized MoS2/a-C composites, and characterized their morphology and structure. We also tested the electrochemical performance of the materials. The electrochemical properties results showed that MoS2/a-C composites had excellent lithium ion storage properties and MoS2/a-C-1 exhibits the most excellent electrochemical properties. The effects of different organic carbon sources on the electrochemical properties were investigated. The possible growth mechanism of the samples is also discussed.(2) MoS2/C globular nanoflowers is synthesized by CTAB aided hydrothermal method with subsequent simple heating process. By changing the microstructure of MoS2 to improve the electrochemical performance. As a kind of common cationic surfactant, the addition amount of CTAB not only has important influence on the morphology of materials, but also affects the electrochemical performance of materials, and MoS2/C-NF-0.05 shows the most excellent electrochemical properties. The effects of different addition amount of CTAB on the morphology and electrochemical properties of materials were investigated. The possible growth mechanism of the samples is also discussed.(3) Through simple thermal reduction process, using (NH4)2MoS4 as molybdenum source and sulfur source, SiO2 nanosphere as template, CTAB as surfactant and carbon source, we synthesized MoS2 and MoS2/C with different morphology. We also tested the electrochemical performance of the materials used as anode material of lithium ion batteries. Through different contrast experiment, we contrast the different influences of SiO2 nanosphere template and CTAB on morphology and electrochemical properties of materials. We also discussed the possible growth mechanism of the materials.