3-V AND 4-V LITHIUM MANGANESE OXIDE CATHODES FOR RECHARGEABLE LITHIUM BATTERIES

Two lithium manganese oxide materials based on the spinel structure have been synthesised by a new solution method which has the advantage that it can be carried out in air unlike previous sol-gel methods. One material is suitable as a 3 V and the other as a 4 V cathode in rechargeable lithium cells. In the case of the 3 V material the addition of a small amount of carbon to the solution during preparation yields a material with a significantly enhanced cycling performance. Cycling at discharge and charge current densities of 1 and 0.5 mA cm(-2), respectively (corresponding to a discharge rate of C/2) and between 3.7 and 2.0 V yields a capacity of 90 mAh g(-1) after 300 cycles for the material prepared using carbon. This represents an enhancement of the discharge capacity by 50% on the 300th cycle when compared with the same material without carbon. Cathodes fabricated from the 4 V material have been cycled at discharge and charging current densities of 1 and 0.5 mA cm(-2), respectively (corresponding to a discharge rate of C/2) between limits of 4.4 and 3.3 V. The specific discharge capacity obtained initially is 110 mAh g(-1) decreasing to 85 mAh g(-1) at 300 cycles.