Preparation And Properties Study Of Disordered Mesoporous Carbon/sulfur Composite

Rechargeable lithium/sulfur (Li/S) batteries have been proposed as the mostpromising high-performance batteries for the next generation due to their high theoreticalcapacity and low cost. However, the poor electrical conductivity and structural stability ofelemental sulfur and the dissolution of the polysulfides have confined the utilization ofelemental sulfur and the cyclic retention of capacity. In this paper, the S/C composite wasprepared to improve the electrical conductivity and structural stability of elemental sulfurand delay the dissolution and diffusion of polysulfides.The disordered mesoporous carbon with20nm pore size was prepared using ZnOnanoparticles as templates. The C/S composite prepared from the disordered mesoporouscarbon shows a higher discharge capacity of902.3mAh/g (composite) during the firstcycle and a better cyclic retention of65%after60cycles than the corresponding cathodeprepared by elemental sulfur. The function mechanism of C/S composite during cycleswas studied to improve the cyclability of the cathode more. The results show that the overloading of the sulfur in mesoporous carbon/sulfur composite depresses the contribution ofmesoporous carbon to the cyclability.Then the properties of the mesoporous carbon were improved by reheating strategyand adding new pore-forming agents. The results show that the sulfur utilization of C/Scomposite has been enhanced due to the improvement of the graphite degree and electricalconductivity of the reheated mesoporous carbon. The C/S composite prepared frommesoporous carbon reheated by1000℃shows a high sulfur utilization of84%during thefirst cycle. The C/S composite prepared from hierarchically porous carbon synthesized byadding KHCO3pore-forming agent shows a high discharge capacity of1066.6mAh/g(composite) during the first cycle and a good cyclic retention of73%after60cycles.As for the preparation of the C/S composite, the S/C composites were synthesized viasublimate diffusion and regular chemical reaction methods separately and then reheated at155℃.The results show that the C/S composite synthesized by regular chemical reactionhas poor sulfur utilization and cyclic retention due to the existence of more free sulfur and the C/S composite after reheating at155℃shows better sulfur utilization and cyclicretention than the C/S composite before reheating. Besides, a novel C/S compositeprepared by in-situ chemical reaction shows a high sulfur utilization of84%during thefirst cycle and a excellent cyclic retention of81%after50cycles.