Changes in the microstructure of Li3.1Mn0.91Cr1.09O4 cathode materials have been studied with cycled electrodes at 21 or 55 degreesC. During cycling, the structure of Li3.1Mn0.91Cr1.09O4 maintained its original hexagonal symmetry. However, a decreased peak intensity ratio of 003 to 104 with little lattice-constant shifts was observed. These are due to increased cation-mixing and dissolution of Mn3+ ions in the electrolyte, thus leading to structural degradation of the material. Hence, the cathode exhibited a specific discharge capacity decay of 29% from its initial capacity (220 mAh/g) after 60 cycles between 4.5 and 2 V with a 0.1 C rate at 21 degreesC. (C) 2001 Elsevier Science BN. All rights reserved.