Observation of Li+ jumps in solid inorganic electrolytes over a broad dynamical range: A case study of the lithium phosphidosilicates Li8SiP4 and Li14SiP6

Abstract

7Li NMR spectroscopy is known to be very sensitive to translational motion in solids and therefore highly suited for investigating temperature-dependent Li+ dynamics. A number of different NMR methods are available for choosing the dynamical range of the observed Li+ jump frequencies present in inorganic solid-state electrolytes. This includes 7Li spin-alignment echo NMR spectroscopy, static 7Li lineshape analysis, and 7Li spin-lattice relaxometry that can be used to detect Li+ jumps in the Hz, kHz, and MHz range, respectively. We introduce and discuss these NMR techniques with respect to their theoretical description and practical application to investigate the Li+ dynamics at different time scales for the two solid-state electrolytes Li8SiP4 and Li14SiP6. The data evaluation for all methods is discussed in detail, focusing on the determination of Li+ jump frequencies and activation energies for the investigated self-diffusion processes in a given structure.

Keywords

• Lithium-ion dynamics
• Solid-state electrolytes
• Lithium phosphidosilicates
• Spin-alignment echo
• Relaxometry
• Battery materials