Lithium Ion Mobility in Lithium Phosphidosilicates: Crystal Structure, ⁷Li, ²⁹Si, and ³¹P MAS NMR Spectroscopy, and Impedance Spectroscopy of Li₈SiP₄ and Li₂SiP₂

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• 作者：Lorenzo Toffoletti ; Holger Kirchhain ; Johannes Landesfeind ; Dr. Wilhelm Klein ; Prof. Dr. Leo van&ensp ; Wü ; llen ; Prof. Dr. Hubert A. Gasteiger and Prof. Dr. Thomas F. Fä ; ssler
• 刊名：Chemistry - A European Journal
• 出版年：2016
• 出版时间：December 5, 2016
• 年：2016
• 卷：22
• 期：49
• 页码：17635-17645
• 全文大小：3367K
• ISSN：1521-3765

文摘

The need to improve electrodes and Li-ion conducting materials for rechargeable all-solid-state batteries has drawn enhanced attention to the investigation of lithium-rich compounds. The study of the ternary system Li-Si-P revealed a series of new compounds, two of which, Li₈SiP₄ and Li₂SiP₂, are presented. Both phases represent members of a new family of Li ion conductors that display Li ion conductivity in the range from 1.15(7)×10⁻⁶ Scm⁻¹ at 0 °C to 1.2(2)×10⁻⁴ Scm⁻¹ at 75 °C (Li₈SiP₄) and from 6.1(7)×10⁻⁸ Scm⁻¹ at 0 °C to 6(1)×10⁻⁶ Scm⁻¹ at 75 °C (Li₂SiP₂), as determined by impedance measurements. Temperature-dependent solid-state ⁷Li NMR spectroscopy revealed low activation energies of about 36 kJ mol⁻¹ for Li₈SiP₄ and about 47 kJ mol⁻¹ for Li₂SiP₂. Both compounds were structurally characterized by X-ray diffraction analysis (single crystal and powder methods) and by ⁷Li, ²⁹Si, and ³¹P MAS NMR spectroscopy. Both phases consist of tetrahedral SiP₄ anions and Li counterions. Li₈SiP₄ contains isolated SiP₄ units surrounded by Li atoms, while Li₂SiP₂ comprises a three-dimensional network based on corner-sharing SiP₄ tetrahedra, with the Li ions located in cavities and channels.