Manganese oxide particles and lithium manganese oxide particles have been produced with an average diameter less than about 500 nm. The particles have a high degree of uniformity including a very narrow distribution of particles sizes. Methods are described for producing metal oxides by performing a reaction with an aerosol including a metal precursor. In particular, the particles can be formed by laser pyrolysis. The lithium manganese oxide particles can be formed by the heat treatment of nanoparticles of manganese oxide. Alternatively, lithium manganese oxide particles can be formed directly by laser pyrolysis. The lithium manganese oxide particles are useful as active materials in the positive electrodes of lithium based batteries. Improved batteries result from the use of the uniform nanoscale lithium manganese oxide particles.