Floating zone crystal growth, structure, and properties of a cubic Li 5.5 La 3 Nb 1.5 Zr 0.5 O 12 garnet-type lithium-ion conductor
Floating zone crystal growth, structure, and properties of a cubic Li 5.5 La 3 Nb 1.5 Zr 0.5 O 12 garnet-type lithium-ion conductor
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立方Li 5.5 La 3 Nb 1.5 Zr 0.5 O 12 石榴石型锂离子导体的浮区晶体生长、结构和性能
DOI：
10.1039/d3ta04606k
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发表时间：
2023
影响因子：
11.9
通讯作者：
Khan, Mojammel
中科院分区：
文献类型：
--
作者：
Ramette, Caleb;Pressley, Lucas;Avdeev, Maxim;Lee, Minseong;Kushwaha, Satya;Krogstad, Matthew;Sarker, Suchismita;Cardon, Paul;Ruff, Jacob;Khan, Mojammel
石榴石型锂离子导体系列Li5+xLa3Nb2−xZrxO12(0≤x≤2)在室温下具有较高的离子电导率，是锂离子电池中很有前途的固体电解质。然而，以前还没有关于≤x≤1的单晶生长或表征的报道。为了全面了解这类材料的结构-性能关系的趋势，我们使用浮动区(FZ)方法生长了直径4 mm，长10 mm的Li5.5La3Nb1.5Zr0.5O12单晶。用劳厄中子单晶衍射仪观察到两种不同的Li位：24d四面体和96h八面体。利用基于中子单晶衍射数据的最大熵方法(MEM)绘制了Li核密度图，并估算了Li在相邻的四面体和八面体位置之间的迁移瓶颈，以及Li在分裂的八面体位置之间的离域。电化学阻抗法测得Li5.5La3Nb1.5Zr0.5O12的室温锂离子电导率为1.37×10−4 S cm−1。电化学阻抗谱测定的Li迁移活化能为0.50 eV，介电弛豫法为0.47 eV。锂离子跳跃尝试频率估计为1.4 7×10 12 Hz，成功迁移的时间尺度为10−7至10−6 S。
As a promising candidate for solid-state electrolytes in Li-ion batteries, the garnet-type Li-ion conductor series Li5+xLa3Nb2−xZrxO12 (LLNZO) (0 ≤ x ≤ 2) exhibits high ionic conductivity at room temperature. However, no previous single-crystal growth or characterization has been reported for LLNZO compositions 0 ≤ x ≤ 1. To obtain a complete understanding of the trend in the structure–property relationship in this class of materials, we used the floating zone (FZ) method to grow a single crystal of Li5.5La3Nb1.5Zr0.5O12 that was 4 mm in diameter and 10 mm in length. Using Laue neutron single-crystal diffraction, two distinct Li sites were observed: tetrahedral 24d and octahedral 96h sites. The maximum entropy method (MEM) based on neutron single-crystal diffraction data was used to map Li nuclear density and estimate that the bottleneck of Li transport exists between neighboring tetrahedral and octahedral sites, and that Li is delocalized between split octahedral sites. Room-temperature Li-ion conductivity in Li5.5La3Nb1.5Zr0.5O12 measured with electrochemical impedance spectroscopy (EIS) was 1.37 × 10−4 S cm−1. The Li migration activation energy was estimated to be 0.50 eV from EIS and 0.47 eV from dielectric relaxation measurements. The Li-ion jump attempt rate was estimated to be 1.47 × 1012 Hz while the time scale of successful migration is 10−7 to 10−6 s.