Lithium can be intercalated into a wide variety of materials using nonaqueous electrochemical cells. The use of aqueous methods is less common because of the reactivity of many lithium intercalation compounds with water. Here we show that lithium can be intercalated into host compounds from aqueous LiOH solution, provided the chemical potential of the intercalated lithium is sufficiently lower than the chemical potential of lithium in lithium metal. Using LiMn2O4 as the host, we formed Li2Mn2O4 by intercalating Li from LiOH solution in an aqueous cell. This method may prove to be an economical way of preparing lithium transition metal oxides with high lithium contents for lithium-ion cell cathodes.