原位硫化构筑FeSx纳米晶/金属有机骨架(MOFs)衍生碳杂化材料及其储锂限域效应研究

Iron(II) sulfides (FeSx) such as FeS and FeS2, have been researched greatly for the development of novel anode materials for lithium ion batteries owing to their high specific capacity, environment-friendliness, and earth-abundance. Nevertheless, FeSx suffers the inferior lithium storage performances resulted from the low electronic conductivity, large volume changes, and the dissolved polysulfides shuttles during the charge-discharge process. The project aims to synthesize FeSx nanocrystals/MOFs derived carbon hybrid materials with excellent lithium storage performances by in situ gas phase sulfidation of metal-organic frameworks (MOFs). The method is new which is involved of the in situ hybridation of MOFs derived carbon and FeSx nanocrystals. The influences of the sulfidation conditions on the crystal phase, size, and structures (hollow or solid) of FeSx nanocrystals, will be investigated, and then the confined formation mechanism of FeSx nanocrystals in the micro/nanopores of MOFs derived carbon will be discussed. On the basis of the structure-activity relationship between the structure and the charge-discharge performances of FeSx nanocrystals/MOFs derived carbon hybrid materials, the confinement effects of FeSx nanocrystals in the MOFs derived carbon on restraining the volume changes and the dissolved polysulfides shuttles will be presented. Furthermore, the electrochemical lithium storage mechanism will be elucidated. The project is expected to solve the bottleneck problems for the practical application of FeSx electrode materials in lithium ion batteries, and has important scientific significance and application value.

硫化亚铁(FeSx)如FeS和FeS2等因其理论比容量高、环境友好以及储量丰富等优点而有望成为新型锂离子电池负极材料，然而其储锂性能受到FeSx低电导率、充放电体积膨胀大和“聚硫离子”穿梭等本征缺陷的限制。针对以上问题，本项目拟通过气相法原位硫化金属有机骨架(MOFs)构筑具有良好储锂性能的FeSx纳米晶/MOFs衍生碳杂化材料，这是一种原位实现MOFs衍生碳和FeSx纳米晶同步杂化的新方法。研究硫化条件对FeSx纳米晶的晶相、晶粒尺寸、FeSx结构(空心或实心)等的影响，探索MOFs衍生碳限域合成FeSx纳米晶的机理；研究FeSx纳米晶/MOFs衍生碳杂化材料的结构与储锂性能之间的构效关系，揭示MOFs衍生碳对FeSx纳米晶的限域效应抑制充放电体积膨胀和“聚硫离子”穿梭的本质，阐明其电化学储锂机制，有望解决制约FeSx用于锂离子电池电极材料的瓶颈问题，具有重要的科学意义和应用价值。

开发廉价、高容量和安全的锂离子电池负极材料对发展二次储能电源技术至关重要。硫化亚铁材料由于具有材料资源丰富、制备简单、理论比容量高以及安全环保等优势而被广泛关注和研究。然而，由于硫化亚铁作为锂离子电池负极材料时以嵌入和转化反应为储锂机制，在充放电过程中存在较大体积膨胀/收缩效应，而且在此过程中伴随产生多硫化物离子，影响材料的循环可逆性；此外由于硫化亚铁材料的本征电子导电性较差，其倍率性能不能满足要求。针对硫化亚铁等材料存在的上述问题，本项目通过气相法原位硫化金属有机骨架(MOFs)制备多种性能优异的硫化亚铁复合碳材料，研究了系列复合材料的形成过程，采用非原位等检测方法揭示了系列复合材料的储锂机制，研究了复合材料的形貌、组分、微观结构以及化学键合等与储锂性能之间的构效关系，进一步揭示了材料组分中各元素对储锂过程中的体积膨胀效应以及多硫化物离子溶出和穿梭等问题的抑制作用，上述研究内容丰富和深化了电化学以及结晶化学等理论基础。本项目所开发的系列硫化物复合材料表现出了优异的电化学性能，如倍率性能、循环稳定性等，为下一代二次电池的开发奠定了一定的基础。