The Impact of Intergrain Phases on the Ionic Conductivity of the LAGP Solid Electrolyte Material Prepared by Spark Plasma Sintering.
The Impact of Intergrain Phases on the Ionic Conductivity of the LAGP Solid Electrolyte Material Prepared by Spark Plasma Sintering.
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DOI：
10.1021/acsami.3c03839
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发表时间：
2023-08
影响因子：
9.5
通讯作者：
Sorina Creţu;David G. Bradley;Liye Feng;O. U. Kudu;L. Nguyen;Tuan‐Tu Nguyen;A. Jamali;J. Chotard;V. Seznec;J. Hanna;Arnaud Demortière;M. Duchamp
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作者：
Sorina Creţu;David G. Bradley;Liye Feng;O. U. Kudu;L. Nguyen;Tuan‐Tu Nguyen;A. Jamali;J. Chotard;V. Seznec;J. Hanna;Arnaud Demortière;M. Duchamp
Li1.5Al0.5Ge1.5(PO4)3(LAGP)具有良好的空气稳定性、良好的电化学稳定窗口和经济实惠的前驱体材料，是一种很有前途的全固态电池氧化物固体电解质。然而，晶界及其相关形貌和组成的存在阻碍了氧化物固体电解质离子导电性的进一步提高。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、其三维形貌和在不同烧结条件下形成的成分对整体LAGP离子电导率的影响之间的关系。采用放电等离子烧结方法在不同温度下烧结氧化物固体电解质材料，结合恒电位电化学阻抗谱、3DFIB-SEM层析、X射线衍射和固体核磁共振/材料模拟方法，深入分析了晶界相的形态、结构和成分对总离子电导率的影响。这项工作首次在纳米水平上建立了对LAGP形貌和晶界中形成的第二相的三维FIB-SEM层析分析，而相关的31P和27Al MAS核磁共振研究结合材料模拟表明，晶界材料由Li4P2O7和无序Li9Al3(P2O7)3(PO4)2相组成。定量的31P MAS核磁共振测量表明，对于680°C的SPS制备，当无序的Li9Al3(P2O7)3(PO4)2相占据晶界成分而高度有序的Li4P2O7相的贡献减少时，LAGP系统的离子导电性达到最佳；而27Al MAS核磁共振数据表明，在整个烧结温度范围内，每一相经历的结构变化都很小。
Li1.5Al0.5Ge1.5(PO4)3 (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 31P and 27Al MAS NMR study coupled with materials modeling reveals that the grain boundary material is composed of Li4P2O7 and disordered Li9Al3(P2O7)3(PO4)2 phases. Quantitative 31P MAS NMR measurements demonstrate that optimal ionic conductivity for the LAGP system is achieved for the 680 °C SPS preparation when the disordered Li9Al3(P2O7)3(PO4)2 phase dominates the grain boundary composition with reduced contributions from the highly ordered Li4P2O7 phases, whereas the 27Al MAS NMR data reveal that minimal structural change is experienced by each phase throughout this suite of sintering temperatures.