Crystal Structure and Li-Ion Transport in Li₂CoPO₄F High-Voltage Cathode Material for Li-Ion Batteries

Abstract

In this work, we provide a structural and computational investigation of the Li2CoPO4F high-voltage cathode material by means of neutron powder diffraction (SG Pnma, a = 10.4528(2) Å, b = 6.38667(10) Å, c = 10.8764(2) Å, RF = 0.0145), crystal chemistry approaches (Voronoi–Dirichlet partitioning and bond valence sums mapping), and density functional theory. The material reveals low energy barriers (0.12–0.43 eV) of Li hopping and a possible 3D channel system for Li-ion migration. It is found that only one Li per formula unit can be extracted within the potential stability window of the commercially available electrolytes. The interrelation between dimensionality, topology and energetics of Li-ion diffusion and peculiarities of the Li2CoPO4F crystal structure are discussed in detail.