One of the limitations of the study presented here is that we consider dopants as ideal, i.e, they affect the defect chemistry of Li 3 OCl only through their effect on the the Fermi energy. In reality, direct dopant-defect interactions may be significant . For example, supervalent dopants, such as Mg 2+ , are predicted to kinetically trap lithium vacancies , which will reduce ionic conductivities relative to the values presented in this work. Despite this limitation, we expect our results to accurately describe quantitative trends for different synthesis conditions and doping strategies for Li 3 OCl.