LiMn2O4 spinel, which has known performance deficiency in rechargeable lithium batteries at elevated temperatures, is coated with grains of LiCoO2 through a novel micro-emulsion process. The resulting composite is characterized by elemental analysis, thermogravimetric analysis, differential scanning calorimetry, powder X-ray diffraction (XRD), and scanning and transmission electron microscopies. For assessment of electrochemical performance, the coated spinel is charged and discharged under typical conditions of battery application, and its cycleability and storage characteristics are determined at 55°C. The results show substantially improved high-temperature performance, with a small reduction in capacity and specific energy relative to the pristine spinel.