Cretu Sorina, Bradley David G, Feng Li Patrick Wen, Kudu Omer Ulas, Nguyen Linh Lan, Nguyen Tuan Tu, Jamali Arash, Chotard Jean-Noel, Seznec Vincent, Hanna John V, Demortière Arnaud, Duchamp Martial
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore.
Laboratoire de Réactivité et de Chimie des solides (LRCS), Université de Picardie Jules Verne, CNRS UMR 7314, 33 rue Saint Leu, Amiens Cedex 80039, France.
ACS Appl Mater Interfaces. 2023 Aug 23;15(33):39186-39197. doi: 10.1021/acsami.3c03839. Epub 2023 Aug 9.
LiAlGe(PO) (LAGP) is a promising oxide solid electrolyte for all-solid-state batteries due to its excellent air stability, acceptable electrochemical stability window, and cost-effective precursor materials. However, further improvement in the ionic conductivity performance of oxide solid-state electrolytes is hindered by the presence of grain boundaries and their associated morphologies and composition. These key factors thus represent a major obstacle to the improved design of modern oxide based solid-state electrolytes. This study establishes a correlation between the influence of the grain boundary phases, their 3D morphology, and compositions formed under different sintering conditions on the overall LAGP ionic conductivity. Spark plasma sintering has been employed to sinter oxide solid electrolyte material at different temperatures with high compacity values, whereas a combined potentiostatic electrochemical impedance spectroscopy, 3D FIB-SEM tomography, XRD, and solid-state NMR/materials modeling approach provides an in-depth analysis of the influence of the morphology, structure, and composition of the grain boundary phases that impact the total ionic conductivity. This work establishes the first 3D FIB-SEM tomography analysis of the LAGP morphology and the secondary phases formed in the grain boundaries at the nanoscale level, whereas the associated P and Al MAS NMR study coupled with materials modeling reveals that the grain boundary material is composed of LiPO and disordered LiAl(PO)(PO) phases. Quantitative P MAS NMR measurements demonstrate that optimal ionic conductivity for the LAGP system is achieved for the 680 °C SPS preparation when the disordered LiAl(PO)(PO) phase dominates the grain boundary composition with reduced contributions from the highly ordered LiPO phases, whereas the Al MAS NMR data reveal that minimal structural change is experienced by each phase throughout this suite of sintering temperatures.
锂铝锗（磷酸）（LAGP）因其出色的空气稳定性、可接受的电化学稳定窗口以及具有成本效益的前驱体材料，是一种很有前景的全固态电池氧化物固体电解质。然而，氧化物固体电解质离子传导性能的进一步提升受到晶界及其相关形态和组成的阻碍。因此，这些关键因素是现代氧化物基固体电解质改进设计的主要障碍。本研究建立了晶界相的影响、其三维形态以及在不同烧结条件下形成的组成与整体LAGP离子传导率之间的关联。采用放电等离子烧结在不同温度下以高致密度烧结氧化物固体电解质材料，而恒电位电化学阻抗谱、三维聚焦离子束扫描电子显微镜断层扫描、X射线衍射和固态核磁共振/材料建模相结合的方法，对影响总离子传导率的晶界相的形态、结构和组成的影响进行了深入分析。这项工作首次对LAGP形态以及在纳米尺度上晶界中形成的第二相进行了三维聚焦离子束扫描电子显微镜断层扫描分析，而相关的磷和铝的魔角旋转核磁共振研究与材料建模表明，晶界材料由磷酸锂和无序的锂铝（磷酸）（磷酸）相组成。定量磷的魔角旋转核磁共振测量表明，当无序的锂铝（磷酸）（磷酸）相在晶界组成中占主导地位，而高度有序的磷酸锂相的贡献减少时，LAGP体系在680°C放电等离子烧结制备时可实现最佳离子传导率，而铝的魔角旋转核磁共振数据表明，在这一系列烧结温度下，每个相经历的结构变化最小。
