Open AccessIon dynamics in fluoride-containing polyatomic anion cathodes by muon spectroscopy
Author(s) -
Beth Johnston,
Peter J. Baker,
Serena Cussen
Publication year - 2021
Publication title -
jphys materials
Language(s) - English
Resource type - Journals
ISSN - 2515-7639
DOI - 10.1088/2515-7639/ac22ba
Subject(s) - polyatomic ion , ion , diffusion , fluoride , muon spin spectroscopy , chemistry , relaxation (psychology) , analytical chemistry (journal) , spectroscopy , activation energy , chemical physics , atomic physics , materials science , inorganic chemistry , muon , thermodynamics , social psychology , psychology , physics , organic chemistry , chromatography , quantum mechanics , particle physics
Polyatomic anion insertion electrodes present compositional and morphological variety, as well as the ability to tune operational voltages by influencing the nature of metal-oxygen bonding. Realizing the application of these compounds as electrodes in Li- and Na-ion batteries requires a detailed understanding of ion dynamics in these systems. Here is presented the microscopic Li-ion and Na-ion diffusion properties in LiFeSO 4 F and Na 2 FePO 4 F, respectively, using muon spin relaxation ( μ + SR) spectroscopy for the first time. Li-ion diffusion processes in the tavorite LiFeSO 4 F phase are found to proceed with an activation energy ( E a ) of 48(4) meV and a diffusion coefficient of 1.71 × 10 −9 cm 2 s −1 , while Na-ion mobility in Na 2 FePO 4 F has a calculated diffusion coefficient of 3.47 × 10 −10 cm 2 s −1 and a higher energy barrier to ion diffusion at 96(8) meV. This is the first such examination of fluoride-containing polyatomic cathodes using μ + SR, where the presence of the highly electronegative fluoride species was thought to preclude activation energy and diffusion coefficient determination due to strong μ + -F − interactions. These insights open up the possibility of studying a myriad of fluoride-containing electrode materials using the μ + SR technique.