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

Manganese oxides are of great interest as low cost and environmentally soun d intercalation cathodes for rechargeable lithium batteries, but have suffe red from limited capacity and instability upon cycling at the moderately hi gh temperatures (50-70 degrees C) encountered in many applications. Here, w e show that LixAl0.05Mn0.95O2 of both the monoclinic and orthorhombic order ed rock salt structures exhibit stable cycling and high discharge capacitie s at elevated temperatures, after an initial transient associated with a sp inel like phase transformation. In cells utilizing Li anodes tested at 55 d egrees 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 w ere achieved over more than 100 cycles (2.0-4.4 V). At low current densitie s, charge capacities approached the theoretical limit. The temperature stab ility and excellent electrochemical performance, combined with nontoxicity and low raw materials cost, make these compounds attractive cathodes for ad vanced lithium batteries. (C) 1999 The Electrochemical Society. S1099-0062( 98)07-062-1. All rights reserved.