Multi- Scale Quantitative Imaging of Dynamic Processes in Beyond-Li-ion Nanobatteries

扫描透射电子显微镜（STEM）目前提供了关于电池材料在循环后发生的结构变化的独特原子尺度信息。然而，由于这些信息是在事后获得的，通常来自固态电极/电解质系统或来自在低温条件下观察到的固-液电极/电解质界面，因此Operando STEM方法在当前最先进的液体电解质和潜在的未来固态电解质中识别动态电池过程期间演变的化学物质的全部潜力尚未实现。目前Operando STEM对液体的限制是由电化学芯片设计引起的，其中液体电解质需要不切实际地薄以确保有足够的图像/分析质量/灵敏度-实验设置不能再现真实的电池的复杂性，因此观察结果难以与技术相关电池中的工艺相关联。在这里，我建议开发第一个“真实的”纳米电池Operando电池，用于快速和准确地测试主要超出锂离子化学物质，如水和/或非水锂和/或钙电池。这种水基和有机基电解质的比较，加上1+或2+离子，提供了一系列潜在的相互作用，可以检查，以了解发生在电极/电解质界面的基本过程，以及它们如何控制电池系统的整体性能和寿命。特别是，这里提出的新的实验设计将允许在纳摩尔浓度的束诱导辐解物种被直接识别，填补了目前的实验中的关键知识空白，它是不可能隔离的化学变化所造成的电子束在operando实验从复杂的反应电化学启动。为了进一步促进这种识别，该项目还将重点关注压缩传感STEM方法的使用，以优化采样策略并减少系统中的整体光束损伤，同时提高观测的时间分辨率。此外，电活性化学物质的交叉污染和交叉将通过这些实验策略的组合而最小化，从而允许实施和测试具有宽范围的性能增强添加剂的新型电极/电解质组合。这里的一个关键的新组件是质谱仪与纳米电池操作STEM电池的耦合，用于量化循环过程中产生的所有化学物质。这意味着水/非水Ca/Li电池可以进行独特的基准测试，并确定其未来应用的潜力。这项工作的最后一部分是使用重叠关联/全息图来绘制电极/电解质界面上的局部场变化。这项工作将主要集中在固态系统上，最初使用开放电池设计进行操作测试，然后扩展到液体电池中的Ca/Li电解质（考虑到稳定性和信号/噪声问题，这是一个更具挑战性的实验），允许将现有的液体电池设计与未来更安全的固态系统结合起来。该提案的总体目标是创建一个多模态Operando（S）TEM平台，可用于将纳米级结构/组成和场变化与离子扩散联系起来，从而提供核心特性，从而加速新电池化学的实施。

Scanning transmission electron microscopy (STEM) currently provides unique atomic scale information about the structural changes occurring in battery materials after cycling has taken place. However, as this information is obtained post-mortem, usually either from solid-state electrode/electrolyte systems or from solid-liquid electrode/electrolyte interfaces observed under cryogenic conditions, the full potential of Operando STEM methods to identify the chemical species evolving during dynamic battery processes in both current state-of-the-art liquid electrolytes and in potential future solid-state electrolytes, has yet to be realised. The current limitations in Operando STEM for liquids are caused by the electrochemical chip design, whereby the liquid electrolyte needs to be unrealistically thin to ensure that there is sufficient image/analytical quality/sensitivity - the experimental set-up does not reproduce the complexities of a real battery and hence the observations are difficult to correlate with processes in technologically relevant batteries. Here, I propose to develop a first "real" nanobattery Operando cell for rapid and accurate testing of primarily beyond Li-ion chemistries, such as aqueous and/or non-aqueous Li and/or Ca batteries. This comparison of water-based and organic-based electrolytes, coupled with either 1+ or 2+ ions, provides a range of potential interactions that can be examined to understand the fundamental processes occurring at electrode/electrolyte interfaces and how they control the overall properties and lifetime of the battery system. In particular, the new experimental design proposed here will allow beam induced radiolytic species at nanomolar concentrations to be identified directly, filling a key knowledge gap in current experimentation where it is impossible to isolate the chemical changes caused by the electron beam during the operando experiment from the complex reactions initiated electrochemically. To facilitate this identification even further, this project will also focus on the use of compressive sensing STEM methodologies to optimise the sampling strategies and reduce the overall beam damage in the system, while increasing the temporal resolution of the observations. Furthermore, cross-contamination and cross-over of the electroactive chemical species will be minimized by the combination of these experimental strategies, permitting the implementation and testing of novel electrode/electrolyte combinations with a wide range of performance enhancing additives. A key novel component here is the coupling of a mass spectrometer with the nanobattery operando STEM cell for quantification of all chemical species generated during cycling. This means aqueous/non-aqueous Ca/Li batteries can be uniquely benchmarked and their potential for future applications be defined. A final part of this work is to use ptychography/holography to map local field changes across electrode/electrolyte interfaces. This work will focus primarily on solid-state systems initially using an open cell design for the operando testing and then be extended to the Ca/Li electrolytes in the liquid cell (a more challenging experiment given the stability and signal/noise issues), permitting a direct connection between the existing designs for liquid cells and the future incorporation of safer, solid state systems. The overall goal of this proposal is to create a multi-modal Operando (S)TEM platform that can be used to link nanoscale structure/composition and field changes with ion diffusion, thereby providing the core properties that can then accelerate the implementation of new battery chemistries.