Compared with existing lithium-ion battery systems, lithium-sulfur batteries have higher theoretical energy density, lower cost, and environmental friendliness, and are one of the ideal candidates for the next generation of high specific energy battery systems. Sulfur (S8) is a typical anion-valued conversion reaction cathode material. The advantage is its high theoretical capacity, but the disadvantage is that the intermediate state product of the electrochemical reaction, lithium polysulfide, is very soluble in ether electrolytes and shuttles to the metal lithium anode. The reaction, known as the "shuttle effect", is the most important reason for limiting the cycle life of lithium-sulfur batteries. At the same time, during the discharge process, the liquid lithium polysulfide will form a Li2S insulating layer covering the surface of the positive electrode, hindering the conduction of electrons and ions, and reducing the rate performance of the battery. Therefore, the key to solving these problems lies in effectively controlling the migration of lithium polysulfide. Associate researcher Suo Liumin of the E01 group of the Clean Energy Key Laboratory of the Institute of Physics of the Chinese Academy of Sciences / National Research Center for Condensed Matter Physics in Beijing and MIT professor Li Juhe and Dr. Xue Weijiang cooperated in the early stage of the "embed-transform" mixed electrode Based on the study of the energy density of lithium-sulfur battery cells (Nature Energy, 4, 374–382, 2019), a multifunctional coating of Chevrel phase Mo6S8 separator with high electron-ion conductivity and electrochemical activity was developed for the first time, which was successful Solve the above problems, and apply it to the research of lithium-sulfur soft battery. The new coating successfully inhibited the formation of Li2S insulating layer, and realized ultra-fast charging and discharging of traditional sulfur positive electrode (25 minutes full / empty). The coating has a strong adsorption force for lithium polysulfide, which successfully prevents lithium polysulfide from "shutting" to the lithium negative electrode side, and realizes a long life cycle of industrial-grade high-load sulfur positive electrode. More importantly, unlike traditional non-active coatings, which will reduce the energy density of the entire battery, this new coating can match the compacted sulfur positive electrode and increase the energy density by more than 20%. At the same time, the researchers collaborated with Brookhaven National Laboratory in the United States to use the world's most advanced synchrotron full-field X-ray tomography (FFXT) technology for the first time in the actual battery operation process The evolution mechanism of the coating material is described. In addition, the performance test of the soft-pack battery further shows that the use of the multi-functional coating can double the cycle life, which is of great significance for the commercialization of lithium-sulfur batteries. The results of this study were published in Matter, a new materials journal of Cell, with the title of Manipulating sulfur mobility enabling advanced Li-S batteries. Related work was supported by the Ministry of Science and Technology's Key R & D Program (2018YFB0104400) and the National Natural Science Foundation of China (51872322). Guanghan Longrun Science and Trade Technology Trade Co., Ltd. , https://www.kairungongju.com
Figure 1. Characterization of PP @ LixMo6S8 related properties and schematic diagram of its working principle in lithium-sulfur batteries 
Figure 2. In-situ 3D tomography of PP @ LixMo6S8 multifunctional diaphragm 
Figure 3. Electrochemical performance of PP @ LixMo6S8 functional separator in button-type lithium-sulfur battery 
Figure 4. Comparison of PP @ LixMo6S8 functional diaphragm and carbon-coated PP @ C diaphragm 
Figure 5. Electrochemical performance of soft-pack battery using PP @ LixMo6S8 functional separator