EAGER: COLLABORATIVE RESEARCH: Reversible Solid Electrolyte Interface (SEI) Layers for Advanced Li-ion Batteries and Beyond

虽然锂离子电池已经在消费电子产品上实现了商业化，但在远程电动汽车和大规模可再生能源存储方面，锂离子电池的需求仍然远远落后。有必要提高锂离子电池的能量密度，并研究“超越锂离子”电池技术，即采用高容量但低成本的材料，如硅、氧或硫电极。在电化学储能电池中，几乎所有的电池化学物质都超出了电解质的稳定性极限，电解质是一种溶解时产生导电溶液的物质。这些电池在很多情况下都能工作，因为电极材料-电解质反应导致在电极材料上形成一层保护材料层，称为固体-电解质界面层。这层保护层的机械和化学反应性决定了电池系统的能量、功率和长期循环稳定性；然而，关于这一保护层形成的基本知识是缺乏的。该研究项目正在研究一种新的固体电解质界面层形成机制，该机制将为电池的许多性能限制提供设计解决方案。该项目的研究成果将被整合到以能源为主题的教育活动中，供学生学习科学、技术、工程和数学（STEM）科目。这个由阿肯色大学和密歇根大学的研究小组合作的研究项目，通过使用硅/电解质界面作为模型系统，寻求一种全新的固体-电解质界面形成机制。通过在各种浓电解质中测试硅膜电极，进行了深入的电化学表征，以了解大块电解质中锂离子的配位环境及其对固体电解质界面层组成的影响。原位原子力显微镜被用来探测电池硅表面固体电解质界面层的形成和演化。理论模拟正在与材料表征相结合，以推进对源自浓缩电解质的固体-电解质界面层的基本理解。该研究项目旨在测试一种控制电极和电解质之间界面特性的新理论，该理论广泛适用于电池技术和许多其他能量存储和转换系统。

Although lithium ion batteries have been commercialized for consumer electronics, they still fall far behind the requirements needed for batteries used in long-range electric vehicles and large-scale renewable energy storage. There is a need to improve the energy densities of lithium ion batteries and to research "beyond lithium ion" battery technologies that employ high-capacity but low-cost materials such as silicon, oxygen or sulfur electrodes. Almost all battery chemistries in electrochemical energy storage cells operate beyond the stability limits of the electrolytes, substance that produce an electrically conducting solution when dissolved. These battery cells operate in many cases because electrode material-electrolyte reactions result in the formation of a protective material layer on the electrode material, called a solid-electrolyte interface layer. The mechanical and chemical reactivity properties of this protective layer dictate the energy, power and the long-term cycling stability of the battery system; however, fundamental knowledge on the formation of this protective layer is lacking. This research project is investigating a new solid-electrolyte interface layer formation mechanism that will enable design solutions for many of the performance limitations of batteries. The research outcomes of this project are being integrated into energy-themed educational activities for students to study science, technology, engineering and mathematics (STEM) subjects. This collaborative research project between research groups at the University and Arkansas and the University of Michigan seeks a fundamentally new solid-electrolyte interface formation mechanism by using silicon/electrolyte interfaces as a model system. Intensive electrochemical characterizations are being conducted by testing silicon film electrodes in various concentrated electrolytes to understand the coordination environments of lithium cations in the bulk electrolytes and its implications on the solid-electrolyte interface layer compositions. In situ atomic force microscopy is being employed to probe the formation and evolution of solid-electrolyte interface layers on silicon surfaces in a cell. Theoretical simulations are being combined with material characterizations to advance the fundamental understanding of solid-electrolyte interface layers derived from concentrated electrolytes. The research project is designed to test a new theory to control the interfacial properties between electrodes and electrolyte, one that is broadly applicable to battery technologies and many other energy storage and conversion systems.