Next, we extend this analysis to all bilayers formed between oxides and chloride catholytes and once again use pie charts to represent the distribution of reaction products, as shown in Figure . Unsurprisingly, LiCl is the major product (in terms of mole fraction). La 2 Zr 2 O 7 is another common product of the reaction between LLZO and each of the chloride SEs considered here. All reaction products shown in Figure were mixed in a 1:1 molar ratio and then pressed into pellets to ensure good contact between the SEs during subsequent heat treatment. One pellet was heat-treated at 300 °C for 24 hours inside a fused quartz tube sealed under vacuum to accelerate the reaction between the two compounds; the resulting product is denoted "Mixed 300 °C". Another pellet was placed inside a fused quartz tube under vacuum and left at 25 °C for 24 hours to mimic similar SE mixing conditions but without any heat treatment; the resulting product is referred to as "Mixed 25 °C". The Mixed pellets and the pure (unmixed) compounds