Effect of Al[sub 2]O[sub 3]-Coated o-LiMnO[sub 2] Cathodes Prepared at Various Temperatures on the 55°C Cycling Behavior

The electrochemical cycling behavior of Al 2 O 3 -coated orthorhombic LiMnO 2 ( o ­ LiMnO 2 ) cathodes prepared at various temperatures ( 150 ­ 700 ° C ) is reported. While the coated o ­ LiMnO 2 cathodes prepared at 600 and 700 ° C show that Al atoms are uniformly distributed throughout the particle, those prepared at 400 and 500 ° C 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 ­ LiMnO 2 results in a higher capacity and a better cycle life during 55 ° C cycling. In particular, coated cathodes prepared at 400 ° C exhibit the best cycling performance, maintaining a maximum capacity of bare o ­ LiMnO 2 , with a minimal capacity loss. Moreover, capacity fading is closely related to Mn dissolution from LiMn 2 O 4 and Li 2 Mn 2 O 4 phases appeared over the 3 and 4 V cycling, respectively.