Structure and Conductivity in LISICON Analogues within the Li 4 GeO 4 -Li 2 MoO 4 System

• Published in: Inorganic chemistry 2023-07, Vol.62 (30), p.11876-11886
• Main Authors: Zhang, Ludan, Malys, Marcin, Jamroz, Jan, Krok, Franciszek, Wrobel, Wojciech, Hull, Stephen, Yan, Haixue, Abrahams, Isaac
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c01222

New solid electrolytes are crucial for the development of all-solid-state lithium batteries with advantages in safety and energy densities over current liquid electrolyte systems. While some of the best solid-state Li -ion conductors are based on sulfides, their air sensitivity makes them less commercially attractive, and attention is refocusing on air-stable oxide-based systems. Among these, the LISICON-structured systems, such as Li Zn GeO and Li V Ge O , have been relatively well studied. However, other systems such as the Li GeO -Li MoO system, which also show LISICON-type structures, have been relatively little explored. In this work, the Li Ge Mo O solid solution is investigated systematically, including the solid solution limit, structural stability, local structure, and the corresponding electrical behavior. It is found that a γ-LISICON structured solution is formed in the range of 0.1 ≤ < 0.4, differing in structure from the two end members, Li GeO and Li MoO . With increasing Mo content, the β-phase becomes increasingly more stable than the γ-phase, and at = 0.5, a pure β-phase (β-Li Ge Mo O ) is readily isolated. The structure of this previously unknown compound is presented, along with details of the defect structure of Li Ge Mo O ( = 0.2) based on neutron diffraction data. Two basic types of defects are identified in Li Ge Mo O involving interstitial Li -ions in octahedral sites, with evidence for these coming together to form larger defect clusters. The = 0.2 composition shows the highest conductivity of the series, with values of 1.11 × 10 S cm at room temperature rising to 5.02 × 10 S cm at 250 °C.