Research On Preparation And Electrochemical Performance Of Cathode Composites And Separators For Lithium-Sulfur Battery

Electrochemical energy storage research has been taken into account to relieve the escalating conflict between growing energy requirements and reducing coal resources. As one of the high energy density electrochemical energy storage system, lithium sulfur batteries have unparalleled advantages compared to lithium-ion batteries. Research on composite materials of sulfur and different carbons has become a hot spot. In order to improve the capacity and cycle performance of lithium-sulfur batteries, this dissertation mainly completed the following work:Firstly, we tested and analyzed three composites of sulfur with different morphologies of carbon. The results showed, the cycling performance of S/CNT and S/KB composites was better than S/AB composite, which was the sulfur adsorption on surfaces or cavities of the CNT and KB, suppressing the dissolution of polysulfide ions.Secondly, we designed a trilayer carbon nanotube (CNT)/Al2O3/polypropylene (PP) separator, by means of simple tape-casting of Al2O3 and CNT layers onto a commercial PP separator, respectively. The CNT layer could suppress the shuttle and enhance the cell performance of Li-S batteries; An inorganic Al2O3 interlayer in the trilayer not only has the advantages on thermal stability and electrolyte intake, but also can provide the strong shield for CNT from penetrating the separator. The capacity maintained 807.8mAh/g at 100 cycles and 745mAh/g on 2C current density of the CNT/Al2O3/PP separator.Finally, we prepared highly safe electrolyte for the lithium-ion batteries with dimethyl methylphosphonate (DMMP). Compared with the common electrolyte of 1M LiPF6/EC+DEC (1:1, w/w), the DMMP-based electrolytes could be used as a "fire extinguisher" with good fire-retarding property.