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Lithium Transport in Li4.4M0.4M′0.6S4 (M = Al3+, Ga3+, and M′ = Ge4+, Sn4+): Combined Crystallographic, Conductivity, Solid State NMR, and Computational Studies
Chemistry of Materials ( IF 8.6 ) Pub Date : 2018-09-13 00:00:00 , DOI: 10.1021/acs.chemmater.8b03175
Bernhard T. Leube 1 , Kenneth K. Inglis 1 , Elliot J. Carrington 1 , Paul M. Sharp 1 , J. Felix Shin 1 , Alex R. Neale 1, 2 , Troy D. Manning 1 , Michael J. Pitcher 1 , Laurence J. Hardwick 1, 2 , Matthew S. Dyer 1 , Frédéric Blanc 1, 2 , John B. Claridge 1 , Matthew J. Rosseinsky 1
Affiliation  

To understand the structural and compositional factors controlling lithium transport in sulfides, we explored the Li5AlS4–Li4GeS4 phase field for new materials. Both parent compounds are defined structurally by a hexagonal close packed sulfide lattice, where distinct arrangements of tetrahedral metal sites give Li5AlS4 a layered structure and Li4GeS4 a three-dimensional structure related to γ-Li3PO4. The combination of the two distinct structural motifs is expected to lead to new structural chemistry. We identified the new crystalline phase Li4.4Al0.4Ge0.6S4, and investigated the structure and Li+ ion dynamics of the family of structurally related materials Li4.4M0.4M0.6S4 (M = Al3+, Ga3+ and M′ = Ge4+, Sn4+). We used neutron diffraction to solve the full structures of the Al-homologues, which adopt a layered close-packed structure with a new arrangement of tetrahedral (M/M′) sites and a novel combination of ordered and disordered lithium vacancies. AC impedance spectroscopy revealed lithium conductivities in the range of 3(2) × 10–6 to 4.3(3) × 10–5 S cm–1 at room temperature with activation energies between 0.43(1) and 0.38(1) eV. Electrochemical performance was tested in a plating and stripping experiment against Li metal electrodes and showed good stability of the Li4.4Al0.4Ge0.6S4 phase over 200 h. A combination of variable temperature 7Li solid state nuclear magnetic resonance spectroscopy and ab initio molecular dynamics calculations on selected phases showed that two-dimensional diffusion with a low energy barrier of 0.17 eV is responsible for long-range lithium transport, with diffusion pathways mediated by the disordered vacancies while the ordered vacancies do not contribute to the conductivity. This new structural family of sulfide Li+ ion conductors offers insight into the role of disordered vacancies on Li+ ion conductivity mechanisms in hexagonally close packed sulfides that can inform future materials design.

中文翻译:

锂运输锂4.4中号0.4中号0.6 š 4(M =铝3+,镓3+,和中号'=葛4+,Sn的4+):组合晶体,电导率,固体NMR,和计算研究

为了了解控制硫化物中锂迁移的结构和组成因素,我们探索了新材料的Li 5 AlS 4 -Li 4 GeS 4相场。两个亲本化合物由六方密结构上定义的填充硫化物晶格,其中四面体的金属位点的不同安排给栗5个ALS 4的层状结构和Li 4周的GeS 4与γ-栗三维结构3 PO 4。两种不同结构基序的结合有望导致新的结构化学。我们确定了新的结晶相Li 4.4 Al0.40.6 š 4,并调查了结构和Li +的家族在结构上相关的材料中的离子动力学李4.4中号0.4中号0.6 š 4(M =铝3+,镓3+中号'=葛4+,Sn的4+)。我们使用中子衍射法解决了Al同源物的完整结构,该结构采用了分层的密堆积结构,并采用了新的四面体排列(M / M')位点和有序和无序锂空位的新颖组合。交流阻抗谱显示,室温下锂电导率在3(2)×10 –6至4.3(3)×10 –5 S cm –1范围内,活化能在0.43(1)和0.38(1)eV之间。在针对Li金属电极的电镀和剥离实验中测试了电化学性能,并显示了Li 4.4 Al 0.4 Ge 0.6 S 4相在200小时内具有良好的稳定性。可变温度7 Li固态核磁共振光谱和从头算的组合在选定的相上进行的分子动力学计算表明,低能垒为0.17 eV的二维扩散负责长距离锂的运输,其扩散途径由无序的空位介导,而有序的空位对电导率没有贡献。硫化物Li +离子导体的这一新的结构族提供了洞察空位在六方密堆积硫化物中Li +离子电导率机制中的作用的信息,可以为将来的材料设计提供参考。
更新日期:2018-09-13
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