基于同步辐射X射线谱学的固态锂硫电池原位研究

Solid-state lithium sulfur battery, which adopts inorganic ionic conductor as separator and electrolyte, is a potential energy storage device with great safety, high theoretical energy density, and low cost. Nevertheless, the delayed development of solid-state lithium sulfur battery is due to the ambiguous understanding to its failure mechanism. Indeed, the unstable electrode/electrolyte interfaces is responsible for degradation of its electrochemical performance. In this proposal, based on the research progress on the conventional lithium sulfur battery and the mechanistic study of electrochemical energy storage, we will employ synchrotron based in-situ X-ray spectroscopic characterization techniques, in combination with conventional lab-based characterizations, such as X-ray diffraction, vibrational spectroscopy, and electron microscopy as well as theoretical simulations, to interpret the interfacial reaction mechanism. Therefore, this research project will concern following three aspects, a) the high performance solid-state electrolyte and its compatibility to sulfur cathode and lithium anode; b) development of synchrotron based in-situ methods to unveil the interfacial transport mechanism for lithium ions; c) interpretation of interface evolution and side reactions and their correlation to the stability of interface. The outcome of this project will undoubtedly shed light on understanding the underlying mechanism with respect to the reversible solid-state electrochemical processes and provide invaluable information for developing high performance and sustainable solid-state batteries.

锂硫电池具有理论能量密度高、成本低廉等优点。固态电解质的采用可以进一步解决其面临的安全性问题。目前固态锂硫电池的发展仍然处于初级阶段，人们对其失效机制的认识还非常有限，而这一机制在很大程度上与界面的不稳定性有直接关联。基于在锂硫电池、电化学储能机理等方面的研究基础，本项目申请提出以同步辐射原位谱学研究为主，结合电子显微、晶体衍射、振动光谱、电化学表征等实验室常规手段以及理论计算，深入开展针对固态锂硫电池性能的界面影响因素的研究。本项目将涉及以下方面：适用于锂硫电池的高性能固态电解质及其影响因素；发展原位同步辐射实验手段揭示锂离子的界面传输机制；通过研究电解质/电极界面演化过程和界面副反应理清界面稳定性的影响因素。可以预期本项目的研究成果将极大有利于深入理解固态锂硫电池中的可逆电化学过程，为实现高性能并满足可持续发展需要的固态电池提高科学依据。

固态电池的提出已经过多年，且已发展出多种成熟的电池结构。然而目前对固态锂硫电池的充放电反应机制以及容量衰减机理的认识还非常有限，而这一机制在很大程度上与界面的不稳定性有直接关联。基于团队在锂硫电池、电化学储能机理等方面的研究基础，项目申请提出以同步辐射原位谱学研究为主，结合电子显微、晶体衍射、振动光谱、电化学表征等实验室常规手段以及理论计算，深入研究影响固态锂硫电池性能的界面行为。主要成果包括：（1）成功构建了多种高性能硫电池正极，并设计了基于聚合物、LPSCl等多种固态电解质的原位表征模型电池;（2）发展了多种原位同步辐射X射线反应池；设计了同光束线站联用的手套箱和样品转移腔；开发了适用于锂硫电池体系研究的原位光学显微镜系统；(3)结合多种表征方法，观察了聚合物固态电解质锂硫电池工作过程中电极/电解质界面结构和化学环境的动态演变；揭示了电池中不同界面处硫物种的结构和分布，揭示了多硫化物在锂硫电池中迁移和扩散路径；探讨了单原子钴催化剂对提高锂硫电池动力学性能的作用机制。此外，本项目建立的原位表征方法学可拓展到其他电池领域，比如本项目利用原位同步辐射谱学技术初步探索了镁硫电池的储能机制以及衰减机理，这些方法学将为新型电池体系的研发与性能提升提供重要的理论指导。