Phonon dispersion of the battery electrolyte parent material Li7La3Zr2O7

Ionic conductivity is central to many green technologies, including the Li-batteries that are now ubiquitous in our daily lives. In this context, there has been a recent drive to discover solid electrolyte materials that have conductivities approaching those of current state-of-the art liquid electrolytes. This is because solid electrolytes promise safer, more reliable, and longer-lived batteries. One particularly promising family of solid electrolyte materials is Li7-xLa3M2-xZrxO12 (M=Ta,Nb) (LLZO). We have recently carried out quasi-elastic neutron scattering experiments with polarization analysis to investigate the diffusion mechanism in one member of this family. We observed two dynamic processes, likely corresponding to local hops and long-range diffusion of lithium. Modelling of this spectrum is currently ongoing using state-of-the-art machine-learning-based molecular dynamics simulations. To complete our understanding of the diffusion mechanism in LLZO, we now wish to turn to the role of lattice vibrations – phonons – in promoting diffusion. As a first step to achieving this, we wish to carry out the first inelastic neutron scattering study on the non-conductive end member compound Li7La3Zr2O12.