The cathode materials Li1-x[Ni0.5Mn1.5]O-4 prepared by coprecipitation from acetate solution by oxalic acid and annealing at 900 degrees C in air had the preferred disordered Ni and Mn on the 16d octahedral sites of a spinel Fd (3) over barm structure. The coprecipitation method provides better crystallinity than the Fd (3) over barm phase previously obtained by quenching from the melt. Polycrystalline octahedral-shaped particles with smooth surfaces contained trace amounts of a LiyNi1-yO impurity that introduced some Mn(III) into the spinel phase. Half-cells cycled at 0.2 C rate between 3.5 and 4.8 V versus Li exhibited a flat voltage V approximate to 4.7 V with a small step at x approximate to 0.5 and a capacity at room temperature of 130 mAh g(-1) that showed no fade after 50 cycles. A small capacity fade was initiated with a cut-off voltage >= 4.9 V; a significant capacity loss between 2 and 5 C cycling rates was reversible to 134 mAh g(-1) on returning to 0.1 C after 50 cycles at 10 C between 3.5 and 5.0 V. Published by Elsevier B.V.