Lithium-manganese-nickel-oxide electrodes with integrated layered-spinel structures for lithium batteries

A series of lithium-manganese-nickel-oxide compositions that can be represented in three-component notation, xLi[Mn-1.5 Ni-0.5]O-4 center dot(1-x){Li2MnO3 center dot Li(Mn0.5Ni0.5)O-2}, in which a spinel component, Li[Mn1.5Ni0.5]O-4, and two layered components, Li2MnO3 and Li(Mn0.5Ni0.5)02, are structurally integrated in a highly complex manner, have been evaluated as electrodes in lithium cells for x=1, 0.75, 0.50, 0.25 and 0. In this series of compounds, which is defined by the Li[Mn1.5Ni0.5]O-4-{Li2MnO3 center dot Li(Mn0.5Ni(0.5))O-2} tie-line in the Li[Mn1.5Ni0.5]O-4-Li2MnO3-Li(Mn0.5Ni0.5)O-2 phase diagram, the Mn:Ni ratio in the spinel and the combined layered Li2MnO3Li(Mn0.5Ni0.5)O-2 components is always 3:1. Powder X-ray diffraction patterns of the end members and the electrochemical profiles of cells with these electrodes are consistent with those expected for the spinel Li[Mn1.5Ni0.5]O-4 (x=1) and for 'composite' Li2MnO3. Li(Mn0.5Ni0.5)O-2 layered electrode structures (x=0). Electrodes with intermediate values of x exhibit both spinel and layered character and yield extremely high capacities, reaching more than 250 mA h/g with good cycling stability between 2.0 V and 4.95 V vs. Li degrees at a current rate of 0.1 mA/cm(2). (c) 2006 Elsevier B.V. All rights reserved.