Synthesis and characterisation of the new oxyfluoride Li<sub>5</sub>SiO<sub>4</sub>F



Dong, Bo, Yan, Jinhui, Walkley, Brant, Inglis, Kenneth K, Blanc, Frederic ORCID: 0000-0001-9171-1454, Hull, Stephen and West, Anthony R
(2018) Synthesis and characterisation of the new oxyfluoride Li<sub>5</sub>SiO<sub>4</sub>F. SOLID STATE IONICS, 327. pp. 64-70.

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Abstract

A new polymorphic phase, Li5SiO4F, with Li+ ion dynamics that are structurally distinct from Li4SiO4, is described. The γ polymorph forms at 750–775 °C, melts incongruently at 800 °C and crystallizes in a monoclinic unit cell: a = 8.67(1) Å b = 16.51(1) Å c = 11.23(2) Å β = 96.61(4) ° and V = 1602.3(3) Å3. The α polymorph forms at 650 °C and appears to be metastable. The γ polymorph has a Li+ ion conductivity of 1.2 × 10−7 S cm−1 at 40 °C, that is several orders of magnitude higher than both the α polymorph and Li4SiO4, with an associated activation energy of 0.51(1) eV. Variable temperature 19F and 7Li static NMR measurements show the absence of F− mobility but the existence of Li+ mobility and confirm that Li+ is the main charge carrier in both polymorphs of Li5SiO4F. 7Li line narrowing NMR experiments suggest that the barrier to local Li hopping is fairly small (0.2–0.3 eV) with faster Li+ ion dynamics in γ-Li5SiO4F compared to α-Li5SiO4F. γ-Li5SiO4F has negligible electronic conductivity, is stable in contact with Li metal and is a new type of stoichiometric, mixed anion, Li+ ion conductor.

Item Type: Article
Uncontrolled Keywords: Lithium silicon oxyfluoride, Li+ ion conductor, Solid state electrolyte
Depositing User: Symplectic Admin
Date Deposited: 11 Dec 2018 09:48
Last Modified: 14 Oct 2023 08:30
DOI: 10.1016/j.ssi.2018.10.014
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3029860