Methods for producing an electrode active material precursor, comprising; a) producing a mixture comprising particles of lithium hydrogen phosphate, having a first average particle size, and a metal hydroxide, having a second average particle size; and b) grinding said mixture in a jet mill for a period of time suitable to produce a generally homogeneous mixture of particles having a third average size smaller than said first average size. The precursor may be used as a starting material for making electrode active materials for use in a battery, comprising lithium, a transition metal, and phosphate or a similar anion.