Lithiated manganese oxide cathodes for rechargeable lithium batteries

Lithiated manganese oxides Li/sub x/Mn/sub y/O/sub 2/ prepared at the low temperature of 400-450/spl deg/C exhibited significantly different electrochemical properties than the spinel phase, LiMn/sub 2/O/sub 4/, formed at 650-850/spl deg/C. The former was nonstoichiometric and yielded a capacity of /spl sim/0.7 LiMn/sub 2/ unit at /spl sim/2.8 V in polymer electrolyte-based Li cells. Its excellent rechargeability was demonstrated by more than 100 charge/discharge cycles. Spinel Li/sub 2/Mn/sub 4/ was formed by heating either a mixture of LiOH and MnO/sub 2/ or LiCO/sub 3/ and MnCO/sub 3/. The latter reaction yielded micron-sized LiMn/sub 2/O/sub 4/. Its capacity of /spl sim/0.8 Li/Mn/sub 2/O/sub 4/ at /spl sim/4 V was highly reversible. AA-size Li-ion cells with spinel LiMn/sub 2/O/sub 4/ exhibited 100 Wh/Kg and 280 Wh/l.