Structural heterogeneity in solid-state batteries can impact material utilization and fracture mechanisms. Dense crystallographically oriented lithium cobalt oxide cathodes serve as a model electrode system for exploring how density variability contributes to stress relief and build up during cycling. Real- and reciprocal-space operando and ex-situ synchrotron based experiments are utilized to understand structural changes across multiple length scales contribute to stress generation and fracture. Nanotomography uncovers a depth-dependent porosity variation in the pristine electrode and highlights preferential fracture in regions of lower porosity during delithiation. Energy-dispersive X-ray diffraction and 3D X-ray absorption near-edge spectroscopy (XANES) reveal the underutilization of cathode material in these regions. 3D XANES also confirms preferential delithiation near the subgrain boundaries. Chemo-mechanical modeling coupled with site-specific mechanical characterization demonstrate how stress accumulation in dense regions of the electrode leads to fracture and underutilization of active material. Our findings reveal the importance of materials design to alleviate stress in small-volume changing cathodes.

中文翻译：

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固态阴极不均匀性对利用率和断裂动力学的影响

固态电池的结构异质性会影响材料利用率和断裂机制。致密晶体取向的锂钴氧化物阴极用作模型电极系统，用于探索密度变化如何有助于应力消除和循环过程中的积累。利用实空间和倒易空间操作以及异位同步加速器实验来了解跨多个长度尺度的结构变化导致应力产生和断裂。纳米断层扫描揭示了原始电极中与深度相关的孔隙率变化，并强调了脱锂过程中孔隙率较低区域的优先断裂。能量色散 X 射线衍射和 3D X 射线吸收近边光谱 (XANES) 揭示了这些区域中阴极材料的利用不足。 3D XANES 还证实了亚晶界附近的优先脱锂。化学机械建模与特定位置的机械表征相结合，证明了电极致密区域的应力积累如何导致活性材料的断裂和利用不足。我们的研究结果揭示了材料设计对于减轻小体积变化阴极的应力的重要性。