LiMn 2 -x Er x O 4 ( x ≤ 0.02) materials were synthesized by a rheological phase reaction method. The thermal behavior of the materials was examined by thermogravimetric and differential scanning calorimetry. X-ray diffraction showed that the samples ( x ≤ 0.02 ) exhibited the same phase as the pure spinel. The lattice parameter of the Er-doped spinel was smaller than that of the undoped one and decreased with increasing doping level. Cyclic voltammograms showed two reversible processes corresponding to the typical response of spinel LiMn 2 O 4 and revealed an insertion-extraction reaction occurring at two stages in the 4-V region. The electrochemical performances of the samples were studied and displayed a better reversibility and cyclability.