These results show that there is a tradeoff considering the electrochemical stability window and the ionic conductivity of Li3YBrxCl6-x. While the ionic conductivity is highest at x=4.5 in the monoclinic phase, the electrolyte starts to oxidize at 3V, similar to Li3YBr6. Small Br concentrations, here represented by x=1.5, increase the ionic conductivity significantly in the 𝑃3 ̅ 𝑚1 phase, but remains to have the high oxidation potential of Li3YCl6.