The stabilization of layered Manganese Oxides for use in Rechargeable Lithium Batteries

ABSTRACTThe layered structure LixTiS2 and LixCoO2 are excellent reversible cathodes for lithium batteries. However, layered lithium manganese oxides are metastable relative to the spinel form on cycling in lithium batteries. They may be stabilized in the layer form by insertion of larger ions such as potassium in the interlayer region, which minimizes the diffusion of the manganese ions from the MnO2 blocks. Their low conductivity is an impediment to their use in high rate batteries. Cobalt can be doped into the layered alkali manganese dioxides, MxMn1-yCoyO2 for M = K or Na, during the hydrothermal synthesis from the alkali permanganates. A single phase is obtained up to about 5% mole cobalt. The cobalt doping is found to enhance the conductivity by two orders of magnitude relative to pure KxMnO2.