论文标题
钙钛矿固体电解质中低晶型电阻的原子尺度起源
Atomic-scale origin of the low grain-boundary resistance in perovskite solid electrolytes
论文作者
论文摘要
氧化物固体电解质（OS）具有提高锂离子电池的安全性和能量密度的潜力，但是它们的高晶型（GB）电阻是一般的瓶颈。在研究最精心良好的钙钛矿OSE中，LI3XLA2/3-XTIO3（LLTO），GBS的离子电导率约为大约三个数量级。相反，相关的LI0.375SR0.4375TA0.75ZR0.25O3（LSTZ0.75）钙钛矿表现出低GB耐药性，原因尚不清楚。在这里，我们使用了通过异常校正的扫描透射电子显微镜和光谱，以及主动的学习矩张量电位，以揭示LSTZ0.75 GBS的原子尺度结构和组成。首次采用振动电子能量损失光谱，以表征LSTZ0.75 GBS中原本不可衡量的LI分布。我们发现，LSZ0.75的GBS不存在LI耗竭，这是LLTO较低GB离子电导率的主要原因。取而代之的是，LSTZ0.75的低GB电阻率归因于形成独特的有缺陷的立方钙钛矿界面结构，该结构包含丰富的空缺。我们的研究提供了对低GB电阻率的原子尺度机制的见解，并阐明了设计具有高离子电导率的OS的可能路径。
Oxide solid electrolytes (OSEs) have the potential to achieve improved safety and energy density for lithium-ion batteries, but their high grain-boundary (GB) resistance is a general bottleneck. In the most well studied perovskite OSE, Li3xLa2/3-xTiO3 (LLTO), the ionic conductivity of GBs is about three orders of magnitude lower than that of the bulk. In contrast, the related Li0.375Sr0.4375Ta0.75Zr0.25O3 (LSTZ0.75) perovskite exhibits low GB resistance for reasons yet unknown. Here, we used aberration-corrected scanning transmission electron microscopy and spectroscopy, along with an active learning moment tensor potential, to reveal the atomic scale structure and composition of LSTZ0.75 GBs. Vibrational electron energy loss spectroscopy is applied for the first time to characterize the otherwise unmeasurable Li distribution in GBs of LSTZ0.75. We found that Li depletion, which is a major reason for the low GB ionic conductivity of LLTO, is absent for the GBs of LSTZ0.75. Instead, the low GB resistivity of LSTZ0.75 is attributed to the formation of a unique defective cubic perovskite interfacial structure that contained abundant vacancies. Our study provides insights into the atomic scale mechanisms of low GB resistivity and sheds light on possible paths for designing OSEs with high total ionic conductivity.
