In the case of Li6PS5Cl, an Arrhenius behavior was observed across the entire measured temperature range (bottom panel in Figure ). The investigated temperature range is smaller than that measured for Li10SnP2S12 because of time constraints, namely the substantially longer data acquisition times required for Li in this system. Again, the overall magnitude of 𝜏 SAE -1 for the Li6PS5Cl compound is smaller than for the Li compound. There is also a lower activation barrier for Li, determined here to be 0.226 ± 0.033 eV. The activation barrier for Li6PS5Cl is determined to be 0.269 ± 0.035 eV. T1 relaxation times. To further elucidate the isotope effect on ionic transport in these solid ionic conductors, 𝑇 1 relaxation measurements were performed for all Li and Li enriched solid electrolytes (Figure ). Similar to the SAE method, the inverse relaxation time 𝑇 1 -1 is proportional to the ion jump rate, so Arrhenius behavior can be related to an activation barrier. Conversely, this NMR spectroscopy method is able to probe ion dynamics that are faster than what the SAE method is able to capture. Thus, 𝑇 1 relaxation provides a complimentary transport perspective, as well as independent validation of the SAE results.