Operando Neutron Diffraction Study of the Structural Degradation Mechanisms in Industrial Multi-Layer Stacked Li-ion Battery Pouch Cells

Operando neutron diffraction is ideal for probing structural changes in Li-ion battery electrodes such as graphite and Li transition metal oxides. Their sensitivity to Li, C and O, coupled with their ability to distinguish Ni, Mn and Co make it particularly suitable for studying bulk structural changes that underpin the electrochemical degradation in Li-ion batteries. However, they are often studied using modified bespoke electrochemical cells with (expensive) deuterated electrolytes and 7Li-enriched cathodes, that are far removed from conventional operating conditions. Hence, the results obtained can often not be directly transferred to real-world operations, thereby restricting their applicability. In this proposal, we intend to perform operando neutron diffraction studies of machine-fabricated multi-layer pouch cells built on the industrial pilot line at WMG, Uni. of Warwick, which have not been modified to aid neutron transmission. The increased thickness of these multi-layered cells preclude X-ray diffraction studies, rendering neutron diffraction as the only probe for electrode structural changes. Crucially, as confirmed through preliminary XPress access data, the high mass loading and machine-built quality of the cells permit high-quality diffraction data to be obtained from Polaris using these cells, without having to use deuterated electrolytes or isotope-enriched materials.

原位中子衍射（Operando neutron diffraction）是探测石墨、锂过渡金属氧化物等锂离子电池电极结构演变的理想手段。其对锂、碳、氧具有优异的探测灵敏度，且可精准区分镍、锰、钴元素，因此特别适用于研究支撑锂离子电池电化学退化的本体结构变化。然而，现有相关研究通常采用定制改装的电化学池，并搭配昂贵的氘代电解液与富集7Li的正极材料，这与电池的常规运行条件相去甚远，导致所得结果往往无法直接迁移至实际应用场景，极大限制了该技术的应用范围。在本研究提案中，我们计划针对华威大学（University of Warwick）WMG工业试点生产线制备的机器组装式多层软包电池开展原位中子衍射研究——此类电池未为优化中子透射性能进行任何改装。由于该多层电池厚度较大，无法开展X射线衍射表征，因此中子衍射成为唯一可用于探测电极结构变化的表征手段。至关重要的是，根据初步获取的XPress快速通道申请数据，此类电池具备较高的电极负载量与优良的机器组装一致性，可在无需使用氘代电解液或同位素富集材料的前提下，借助Polaris谱仪获取高质量的衍射数据。