Ion dynamics in fluoride-containing polyatomic anion cathodes by muon spectroscopy

Polyatomic anion insertion electrodes present compositional and morphological variety, as well the ability to tune operational voltages by influencing nature of metal-oxygen bonding. Realising application these compounds in Li- Na-ion batteries requires a detailed understanding ion dynamics systems. Here is presented microscopic Li-ion diffusion properties LiFeSO4F Na2FePO4F, respectively, using muon spin relaxation (μ+SR) spectroscopy for first time. processes tavorite phase are found proceed with an activation energy (Ea) 48 meV coefficient 1.71×10-9 cm2 s-1, while mobility Na2FePO4F has calculated 3.60×10 10 s 1 higher barrier at 102 meV. This such examination fluoride-containing polyatomic cathodes μ+SR, where presence highly electronegative fluoride species was thought preclude determination due strong μ+-F interactions. These insights open up possibility studying myriad electrode materials μ+SR technique.