The surface of spinel LiMn2O4 is modified with different quantities of a Mn4+-rich phase prepared by a facile sol-gel method to improve electrochemical properties at elevated temperatures. Impurity-free and uniform morphologies for the LiMn2O4 particles are demonstrated from the X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The Mn4+-rich phase modified on the surface of the LiMn2O4 alleviates the dissolution of manganese in the electrolyte, thus improving the cycling performance and rate capability relative to the bare LiMn2O4. 1wt.%-modified LiMn2O4 delivers a capacity retention of 92.7% and a discharge capacity of 113.5mAhg−1 after 200 cycles at 1C and 25°C, compared with that of 83.1%, and 100.8mAhg−1 for the bare LiMn2O4. In addition, after 100 cycles, a capacity retention of 88.6% at 1C is achieved for 1wt.%-modified LiMn2O4 at 55°C, which is higher than the 76.0% for the bare LiMn2O4. Furthermore, this sample shows the best rate capability among all samples. The Mn4+-rich phase is an appropriate candidate for modifying surfaces to suppress dissolution of manganese, thereby improving the electrochemical properties of LiMn2O4.