Lithium manganese oxide (LiMn2O4) used as a positive-electrode material in lithium-ion batteries is prepared by a new water-in-oil emulsion process. An aqueous solution containing lithium and manganese cations is emulsified in kerosene by adding sorbitan monooleate as the surfactant. When the precursor solution is agitated by a magnetic mixer, impure products are obtained. LiMn2O4 is formed along with residual Mn2O3 at elevated temperatures because of insufficient dispersion and mixing of the reactive cations. When a homogenizer with a greater agitation speed is used, however, a well-mixed precursor solution is prepared, and pure LiMn2O4 with a Fd 3m structure is synthesized after calcination at 800°C for 1h. LiMn2O4 powder prepared by the homogenizer has higher crystallinity, smaller particle size, and narrower size distribution than that prepared by the magnetic stirrer. Compared with powder prepared by the solid-state method, the LiMn2O4 powder exhibits smaller particle size and less agglomeration. Moreover, the emulsion process significantly shortens the heating time required. The prepared LiMn2O4 powder has a high discharge capacity (120.4mAhg−1) on the first cycle and good cycleability.