Li2B3O4F3, a new lithium-rich fluorooxoborate

• Published in: Journal of solid state chemistry 2012-02, Vol.186, p.104-108
• Main Authors: Pilz, Thomas, Nuss, Hanne, Jansen, Martin
• Format: Article
• Language: English
• Subjects: Acentric borate; Charge; Condensed matter: structure, mechanical and thermal properties; Conversion; Cross-disciplinary physics: materials science; rheology; Crystallization; Exact sciences and technology; Inorganic compounds; Lithium; Lithium fluorooxoborate; Lithium ion conductivity; Lithium ions; Materials science; Materials synthesis; materials processing; Physics; Solid state; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Triangles
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2011.11.053

The new lithium fluorooxoborate, Li2B3O4F3, is obtained by a solid state reaction from LiBO2 and LiBF4 at 553K and crystallizes in the acentric orthorhombic space group P212121 (no. 19) with the cell parameters a=4.8915(9), b=8.734(2), and c=12.301(2)Å. Chains of fluorinated boroxine rings along the b axis consists of BO3 triangles and BO2F2 as well as BO3F tetrahedra. Mobile lithium ions are compensating the negative charge of the anionic chain, in which the fourfold coordinated boron atoms bear a negative formal charge. Annealing Li2B3O4F3 at temperatures above 573K leads to conversion into Li2B6O9F2. The title compound is an ionic conductor with the highest ion conductivity among the hitherto know lithium fluorooxoborates, with conductivities of 1.6×10−9 and 1.8×10−8Scm−1 at 473 and 523K, respectively. Repetition unit of Li2B3O4F3. [Display omitted] ► Li2B3O4F3 is the third member within the family of lithium fluorooxoborates. ► It shows the highest lithium ion conductivity among them. ► Chains of interconnected fluorinated boroxine rings run along the b axis. ► Acentric space group meets the requirement for second harmonic generation.