For doped Li 3 OCl, supervalent doping is predicted to increase the concentration of both V Li and O Cl , with the preferentially formed defect depending on synthesis conditions, while subvalent doping is predicted to preferentially increase the concentration of V Cl ahead of Li i under all considered synthesis conditions. Supervalent doping is predicted to be effective at increasing the ionic conductivity, particularly under Lipoor synthesis conditions. Subvalent doping at moderate doping levels, however, is predicted to decrease the room-temperature ionic conductivity, due to two complementary effects. First, subvalent doping at low-tomoderate dopant concentrations decreases the concentration of lithium vacancies more rapidly than it increases the concentration of lithium interstitials. Second, increasing the number of lithium interstitials formed under synthesis conditions causes increased "quenching" of lithium vacancies when cooling to room temperature through recombination of V Li as [V Li + Li i ] Frenkel pairs. Although sufficiently high levels of subvalent doping are predicted to increase ionic conductivity relative to undoped Li 3 OCl, the ionic conductivity thus obtained is significantly lower than predicted for supervalent doping at equivalent dopant concentrations. We therefore do not expect subvalent doping to be a practical doping strategy for increasing the ionic conductivity of Li 3 OCl.