Application Of Composite Conductive Agent And ZIF-67 Derived Carbon Material Modified Separator In Lithium-sulfur Battery

Lithium-sulfur（Li-S）batteries have received extensive attention due to their high theoretical specific capacity.However,Li-S batteries still have problems such as low utilization of active material（S）,"shuttle effect"caused by polysulfides（Li PSs）,and poor cycle stability,which make them unable to be commercialized.To this end,great efforts have been made.In recent years,through the design and synthesis of S host materials,the modification of modified separators,and the improvement of lithium anodes,the performance of Li-S batteries has been significantly improved.In this paper,based on the related problems of Li-S batteries,the following researches were carried out on the influence of conductive additives on batteries performance and the modification of separators to improve the performance of Li-S batteries:（1）Firstly,the conductive carbon black/acetylene black composite conductive agent was prepared,and then its effect on the electrochemical performance of Li-S battery cathode was studied.Compared with the commonly used acetylene black conductive agent,the specific discharge capacity of the KB-S cathode prepared by the composite conductive agent is 1016.5 m Ah g^-1at 0.1 C,and remains 652.2 m Ah g^-1after 150 cycles,with a cycle retention rate of about 64.1%,which has higher capacity retention and better cycle stability.（2）The cobalt-based MOF material ZIF-67 was first synthesized and then carbonized to prepare a cobalt-doped carbon material（Co-C）.A self-supporting thin film modified separator（CNT/Co-C-PP）was prepared by means of vacuum filtration.The reaction kinetics and catalytic effect on Li PSs were investigated by electrochemical methods,and the results showed that Co-C captures Li PSs through its strong chemisorption ability to soluble Li PSs.Under the synergistic effect of CNT and Co,the rapid transport of Li⁺in the reaction process is promoted,the redox reaction kinetics of Li PSs are improved,and the transformation of Li PSs is promoted.CNT/Co-C-PP slowed down the shuttle effect to a greater extent and improved the utilization of S.Using the CNT/Co-C-PP separator,the Li-S batteries have an initial capacity of 1043.8m Ah g^-1in cycling tests at a current density of 0.5 C,with a capacity decay of 0.07%per cycle after 450 cycles.