Synthesis And Electrochemical Performance Of MoS₂/Carbon Composite As Anode Materials For Lithium Ion Batteries

MoS2is of particular interest as alternatives for graphite anode materials used in commerciallithium ion batteries (LIBs) due to their high theoretical capacities and safer operation. Since thestacked structure of the layered molybdenum disulfide, with the intercalation/deintercalation of Liions, the structure of molybdenum disulfide will change, thus affecting the electrochemicalperformance. If the graphene-like MoS2nanosheets are uniformly dispersed on other mediums whichwith high conductivity, their aggregation can be effectively inhibited, which leads to enhancedelectrochemical properties. The main achievements are listed as below:1. We present a facile process to synthesize MoS2/OMC composites. MoS2/OMC composites wereprepared by hydrothermal route using ammonium tetrathiomolybdate/sodium molybdate, thioureaand ordered mesoporous carbon (OMC) as starting materials. The performance of the two materialshave improved significantly compare to the bulk MoS2. But the MoS2and OMC was not compositedwell of the material using ammonium tetrathiomolybdate as precursor, and the electrochemicalperformance was not good enough. That may because the MoS2was not composited well. While thecomposite synthesized using sodium molybdate and sulfocarbamide as precursors have goodperformance. And the uniformly dispersed of MoS2on OMC can buffer the volume change duringintercalation/deintercalation of Li ions, and then greatly improved the cycling performance.2. We doped nitrogen in to the structure of OMC for functionalizing carbon materials andcompounded with MoS2, using sodium molybdate and thiourea as precursors. The electrochemicalperformance has improved significantly. The irreversible capacity increased with the increasing ofthe nitrogen content. At the current density of100mA/g, the capacity of the compsite remains951mAh/g after50cycles when the nitrogen content of the OMC was5%.3. Not only the above-mentioned two kinds of precursors, but the sodium molybdate, L-cysteinewas also used for synthesized MoS2/graphene composite. The MoS2and graphene was notcomposited well of the material using ammonium tetrathiomolybdate as precursor, and theelectrochemical performance was not good enough. While the composite synthesized using sodiummolybdate and sulfocarbamide as precursors have good performance. Using sodium molybdate andL-cysteine as precursors the compsite exhibits best performance. Under the solution-phase reaction,L-cysteine formed a polymeric network structure, which facilitated the formation of atwo-dimensional structure for the compounds. These layered structural compounds could extensively improve the cycling behavior of the nanoplates in LIBs.4. We develop an efficient and scalable strategy for the PVP-assisted synthesis of MoS2/graphenevia a hydrothermal reaction. The PVP has an important effect on the products’ final morphologiesand electrochemical properties. It is interesting to find the (002) plane which indicates a wellstackedlayered structure was disappear with the increasing addition of PVP, so sample is more likely toform the nanosheet structure of MoS2on grapheme. The MoS2nanosheets with extremely short Liion insertion paths manifest improved lithium storage properties with a better cyclic performance,higher capacity and better rate capability. But excess addition of PVP is not conducive to theelectrochemical properties.