基于“微胶囊”结构的锂硫电池正极材料设计、制备及性能研究

Low sulfur utilization and poor cycling stability are considered as the key problems for the application of lithium-sulfur (Li-S) batteries. Bearing these problems in mind, particular structured matrices embodied with e- conductive carbon wall for S/Li2S deposition and Li+ conductive window will be designed and then synthesized in this project. Several natural high molecular polymers and lithium sulfide are chosen as the sources of carbon microcapsule and sulfur core respectively. Based on the microcapsule structure, cathode materials with high sulfur dispersion, low sulfur loss and little expansion effect will be designed and synthesized. More specifically, in order to improve the utilization of sulfur, microcapsule wall is chosen as the carrier to disperse sulfur. Moreover, bi-functional microcapsule wall is used as the protective layer for trapping the polysulfides effectively; the gap between the microcapsule wall and the microcapsule core is employed for buffering the expansion stress, for avoiding the structural collapsing during charge and discharge process. This project is expected to provide alternative idea and methodology for excellent sulfur fixation and good cycling stability, and to promote the Li-S battery development in both scientific research and practical application aspects.

针对高比能锂硫电池正极材料存在的硫利用率低、循环稳定性差等问题，本项目拟从构建抑制多硫化物“穿梭效应”的物理屏障出发，以高分子材料为囊壁碳源、固态电解质为囊壁孔道锂离子导体、硫化锂为囊芯硫源，制备使活性物质满足“分散度高、溶解流失少、膨胀效应小”要求的“微胶囊”结构正极材料。采用胶囊壁内壁作为活性物质的载体，使其高度分散，提高利用率；利用具有离子传导、电子传导双功能特性的胶囊壁作为活性物质的保护壳，消除/抑制电解液传导锂离子带来的多硫化物溶解流失问题，充分发挥固硫效能；借助囊壁与囊芯间的空隙以缓解反应过程中硫电极的体积膨胀，避免充放电过程中囊壁碳材料的结构坍塌，保持电极的完整性。本项目的实施，将为锂硫电池实现活性物质的高效利用和有效固定提供新思路、开辟新途径，对推进锂硫电池的发展具有重要科学意义和实用价值。