Al/Ga-Doped Li7La3Zr2O12 Garnets as Li-Ion Solid-State Battery Electrolytes: Atomistic Insights into Local Coordination Environments and Their Influence on 17O, 27Al, and 71Ga NMR Spectra
Al/Ga-Doped Li7La3Zr2O12 Garnets as Li-Ion Solid-State Battery Electrolytes: Atomistic Insights into Local Coordination Environments and Their Influence on 17O, 27Al, and 71Ga NMR Spectra
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DOI：
10.1021/jacs.9b12685
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发表时间：
2020-02-12
影响因子：
15
通讯作者：
Morris, Andrew J.
中科院分区：
文献类型：
--
作者：
Karasulu, Bora;Emge, Steffen P.;Morris, Andrew J.
Li7La3Zr2O12(LLZO)石榴石具有高的稳定性和离子导电性，是下一代全固态锂离子电池最有前途的固体电解质之一。为了帮助确定不同的超价掺杂对晶体结构和位置偏好的影响，我们结合了固态O-17，(27)AI和Ga-71魔角旋转(MAS)核磁共振谱和密度泛函理论(DFT)计算。基于密度泛函理论对未掺杂和Al和/或Ga掺杂的LLZO变体的缺陷组态分析揭示了原子的局域网络与观察到的核磁共振信号之间的相互作用。具体来说，Al-27和Ga-71核磁共振谱中观察到的两个特征既是由于四配位Li1/24d中多面体配位/位置对称性的偏离(而不是其他Li2/96h或La位置的掺杂)，也是由于与这些掺杂位置共享氧原子的占据的相邻Li2位置的数量所致。尖锐的Al-27和Ga-71共振来自于位于高度对称的四面体24d位置的掺杂，具有四个共享角点的LiO4邻居，而更广泛的特征来自于高度扭曲的掺杂位置，具有较少的或没有直接的LiO，邻居。Al-27/Ga-71四极耦合的大小与掺杂位的变形之间的关系。建立了X={Al/Ga})的XO4/XO5/XO6。这些体系的O-17 MAS核磁共振谱提供了对氧连接网络的洞察：来自掺杂剂配位氧的O-17信号被解析并用于进一步表征掺杂剂和其他位置的微环境。
Li7La3Zr2O12 (LLZO) garnets are among the most promising solid electrolytes for next-generation all-solid-state Li-ion battery applications due to their high stabilities and ionic conductivities. To help determine the influence of different supervalent dopants on the crystal structure and site preferences, we combine solid-state O-17, (27)AI, and Ga-71 magic angle spinning (MAS) NMR spectroscopy and density-functional theory (DFT) calculations. DFT-based defect configuration analysis for the undoped and Al and/or Ga-doped LLZO variants uncovers an interplay between the local network of atoms and the observed NMR signals. Specifically, the two characteristic features observed in both Al-27 and Ga-71 NMR spectra result from both the deviations in the polyhedral coordination/site-symmetry within the 4-fold coordinated Li1/24d sites (rather than the doping of the other Li2/96h or La sites) and with the number of occupied adjacent Li2 sites that share oxygen atoms with these dopant sites. The sharp Al-27 and Ga-71 resonances arise from dopants located at a highly symmetric tetrahedral 24d site with four corner-sharing LiO4 neighbors, whereas the broader features originate from highly distorted dopant sites with fewer or no immediate LiO, neighbors. A correlation between the size of the Al-27/Ga-71 quadrupolar coupling and the distortion of the doping sites (viz. XO4/XO5/XO6 with X = {Al/Ga}) is established. O-17 MAS NMR spectra for these systems provide insights into the oxygen connectivity network: O-17 signals originating from the dopant-coordinating oxygens are resolved and used for further characterization of the microenvironments at the dopant and other sites.