Methods for producing lithium iron phosphate or lithium manganese phosphate or lithium iron manganese phosphate, by colloidal synthesis are provided. Such methods include the operation of reacting a lithium salt, an iron(II) halide (and/or a manganese(II) halide) and a phosphorus compound, which, under the reaction conditions, is capable of releasing the phosphate ion, in the presence of an organic surfactant or a mixture of organic surfactants including an alkylamine or alkenylamine, in which the surfactant or mixture of surfactants is capable of dissolving the lithium salt and the iron halide (and/or the manganese halide), where used, in an organic solvent, which is liquid at room temperature, in which the surfactant or mixture of surfactants is soluble, the reaction being performed at a temperature not lower than 250° C.