Nanosized lithium manganate powders are successfully synthesized via a newly developed reverse-microemulsion (RμE) process. Monophasic LiMn2O4 powders are obtained after calcining the precursor powders at 700°C. The particle size of the spinel compound significantly depends on the concentration of the aqueous phase. Increasing the water-to-oil volume ratio results in an increase in the particle size. While the aqueous phase is equal to 0.5 M, the size of the obtained LiMn2O4 powder is around 60-70 nm. It is found that the specific capacity of nanosized LiMn2O4 particles is greater than that of submicron particles. The large surface area of ultrafine particles is considered to facilitate the intercalation and deintercalation of lithium ions during the cycling test.