Effect of Al2O3-coated o-LiMnO2 cathodes prepared at various temperatures on the 55°C cycling behavior

The electrochemical cycling behavior of Al2O3-coated orthorhombic LiMnO2 (o-LiMnO2) cathodes prepared at various temperatures (150-700degreesC) is reported. While the coated o-LiMnO2 cathodes prepared at 600 and 700degreesC show that Al atoms are uniformly distributed throughout the particle, those prepared at 400 and 500degreesC show that Al atoms are mainly located at the surface region. This difference significantly affects both the discharge capacity and the cycle life of the electrodes, and lower temperature heat-treatment of the coated o-LiMnO2 results in a higher capacity and a better cycle life during 55degreesC cycling. In particular, coated cathodes prepared at 400degreesC exhibit the best cycling performance, maintaining a maximum capacity of bare o-LiMnO2, with a minimal capacity loss. Moreover, capacity fading is closely related to Mn dissolution from LiMn2O4 and Li2Mn2O4 phases appeared over the 3 and 4 V cycling, respectively. (C) 2001 The Electrochemical Society.