LiPF6 under pressure: a symmetry-mode-based structural analysis

Abstract

The lithium salt LiPF6 is a key component in commercial lithium-ion battery (LIB) electrolytes. However, its structural properties under pressure remain unexplored, despite increasing interest in the effect of pressure on electrolyte behaviour, and a growing interest in high pressure synthesis of new Li-hexafluoride cathode materials. Here, we present the first high pressure neutron diffraction study of solid LiPF6 up to 7.4 GPa. Refinements reveal that the ambient rhombohedral structure (space group R¯3) remains stable throughout, with pressure accommodated primarily by tilting of the corner-shared LiF6 and PF6 octahedra and contraction of the LiF6 units. This study establishes a foundation for understanding the phase behaviour of Li-based hexafluorides under extreme conditions.