Surface-Dependent Stability of the Interface between Garnet Li7La3Zr2O12 and the Li Metal in the All-Solid-State Battery from First-Principles Calculations
Surface-Dependent Stability of the Interface between Garnet Li7La3Zr2O12 and the Li Metal in the All-Solid-State Battery from First-Principles Calculations
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DOI：
10.1021/acsami.9b23019
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发表时间：
2020-04-08
影响因子：
9.5
通讯作者：
Tateyama, Yoshitaka
中科院分区：
文献类型：
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作者：
Gao, Bo;Jalem, Randy;Tateyama, Yoshitaka
石榴石型Li7La3Zr2O12(LLZO)固体电解质因其在大气条件下具有良好的化学稳定性而备受关注，适合于实用化的全固态电池。然而，最近的工作观察到LLZO/Li界面的电化学不稳定。在这里，我们用基于密度泛函理论框架的高通量界面结构搜索方案进行了全面的第一性原理研究，揭示了不稳定性的根源。基于构建的低指数表面相图，我们发现配位不饱和(即配位数<；6)的Zr位广泛存在于低能LLZO表面。一旦LLZO表面与Li金属接触，这些未配位的Zr位就会减少，从而导致LLZO/Li界面的化学不稳定。此外，计算的界面形成能和粘附能表明，Li在LLZO表面的润湿性与端接结构有关。为了防止LLZO对Li金属的还原，需要采取控制合成气氛等方法。本文的分析结合第一性原理的全面计算，为合理优化ASSB中LLZO电解液与锂金属阳极之间的界面提供了新的视角。
The garnet-type Li7La3Zr2O12 (LLZO) solid electrolyte is of particular interest because of its good chemical stability under atmospheric condition, suitable for practical all-solid-state batteries (ASSBs). However, recent works observed electrochemical instability at the LLZO/Li interfaces. Herein, we have revealed the origin of the instability by performing a comprehensive first-principles investigation with a high-throughput interface structure search scheme, based on the density functional theory framework. Based on the constructed phase diagrams of low-index surfaces, we found that the coordinatively unsaturated (i.e. coordination number < 6) Zr sites exist widely on the low-energy LLZO surfaces. These undercoordinated Zr sites are reduced once the LLZO surface is in contact with the Li metal, leading to chemical instability of the LLZO/Li interface. Besides, the calculated formation and adhesion energies of interfaces suggest that the Li wettability on the LLZO surface is dependent on the termination structure. The employment of the approaches such as by controlling the synthesis atmosphere are needed for preventing the reduction of LLZO against the Li metal. The present analysis with comprehensive first-principles calculations provides a novel perspective for the rational optimization of the interface between LLZO electrolyte and Li metal anode in the ASSB.