Ultrasonic spray pyrolysis has been successfully applied to the synthesis of partially Cr-substituted lithium manganese oxide (LiCrxMn2-xO4(0 <= x <= 0.3)) particles from the precursor solution; LiNO3, Cr(NO3)(3)-9H(2)O, and Mn(NO3)(2)-6H(2)O were stoichiometrically dissolved into distilled water. The resulting powders were spherical nanostructured particles with a narrow particle size distribution. All the samples exhibited a pure cubic spinel structure in the X-ray diffraction (XRD) patterns. The morphology of as-prepared powders changed from spherical and porous to spherical and dense with an increasing amount of Cr substitution. The densification of particles progressed with the amount of Cr substitution. The as-prepared samples were sintered at 750 degrees C for 4 h in air and used as cathode active materials for lithium-ion batteries. Test experiments in the electrochemical cells Li vertical bar 1M LiClO4 in EC: DEC=1:1 vertical bar LiCrxMn2-xO4 demonstrated that the nanostructured LiCrxMn2-xO4 particles, prepared by the ultrasonic spray pyrolysis and then calcined at 750 degrees C for 4 h in air, were a promising cathode active material for 4 V lithium-ion batteries at high-charge-discharge and high-temperature operations.