Solid Electrolytes: Extremely Fast Charge Carriers in Garnet-Type Li6La3ZrTaO12 Single Crystals

The development of all-solid-state electrochemical energy storage systems,such as lithium-ion batteries with solid electrolytes, requires stable,electronically insulating compounds with exceptionally high ionicconductivities. Considering ceramic oxides, garnet-type Li7La3Zr2O12andderivatives, see Zr-exchanged Li6La3ZrTaO12(LLZTO), have attracted greatattention due to its high Li+ionic conductivity of 10−3Scm−1at ambienttemperature. Despite numerous studies focussing on conductivities ofpowder samples, only few use time-domain NMR methods to probe Li iondiffusion parameters in single crystals. Here we report ontemperature-variable NMR relaxometry measurements using both laboratoryand spin-lock techniques to probe Li jump rates covering a dynamic timewindow spanning several decades. Both techniques revealed a consistentpicture of correlated Li ion jump diffusion in the single crystal; the dataperfectly mirror a modified BPP-type relaxation response being based on aLorentzian-shaped relaxation function. The rates measured could beparameterized with a single set of diffusion parameters. Results from NMRare completely in line with ion transport parameters derived from conductivityspectroscopy.