Coprecipitation was applied to prepare Mg–Mn hydroxide precursor for optimal synthesis of Mg-doped Li–Mn–O spinel. The as-obtained precursor was then mixed with LiOH followed by an annealing at 850 oC for 15h. The spinel prepared from coprecipitated precursor can deliver over 100mAhg−1 at a discharge rate as high as 10C (1.2Ag−1) and retain 100% of the initial capacity in the 45th cycle while the spinel prepared directly from the as-purchased metal salts yields both smaller initial capacity and lower capacity retention after cycling. It was found that the crystallinity is higher and the charge transfer resistance is lower for the spinel prepared via coprecipitated precursor, which maybe resulted from the more homogeneous distribution of metal ion in such a spinel, than that in the spinel prepared from as-purchased reagents.