Galvanostatic experiments were conducted on the cells at 22°C using a Bio-Logic VMP-3 cell test system. Several Li/NaK/LLZTO/NaK/Li cells were subjected to galvanostatic cycling at nominal current densities (i.e., based on initial electrode areas) from 0.25 to 3 mA cm -2 using 0.25 mA cm - 2 increments at nominal areal capacities of 6 mAh cm -2 per half-cycle (30 μm lithium plating thickness).