High capacity, temperature-stable lithium aluminum manganese oxide cathodes for rechargeable batteries

Manganese oxides are of great interest as low cost and environmentally sound intercalation cathodes for rechargeable lithium batteries, but have suffered from limited capacity and instability upon cycling at the moderately high temperatures (50-70 degrees C) encountered in many applications. Here, we show that LixAl0.05Mn0.95O2 of both the monoclinic and orthorhombic ordered rock salt structures exhibit stable cycling and high discharge capacities at elevated temperatures, after an initial transient associated with a spinel like phase transformation. In cells utilizing Li anodes tested at 55 degrees C, rechargeable capacities of 150 mAh/g for the orthorhombic and 200 mAh/g for the monoclinic phase and energy densities similar to 500 Wh/kg were achieved over more than 100 cycles (2.0-4.4 V). At low current densities, charge capacities approached the theoretical limit. The temperature stability and excellent electrochemical performance, combined with nontoxicity and low raw materials cost, make these compounds attractive cathodes for advanced lithium batteries. (C) 1999 The Electrochemical Society. S1099-0062(98)07-062-1. All rights reserved.