High Performance Composite Lithium-Rich Nickel Manganese Oxide Cathodes for Lithium-Ion Batteries.

Li_1.0[Li_1/7Mn_4/7 Ni_2/7]O₂ cathode material was prepared by a facile, one-pot synthesis method. The structure of the material was determined by Rietveld refinement of structural models using high-resolution synchrotron X-ray and neutron powder diffraction data and was found to consist of two distinct phases. The major phase, with composition Li_1.25(3)Ni_0.17(1)Mn_0.61(1)O₂, close to the well-characterized Li_1.2Ni_0.2Mn_0.6O₂ composition can be described as an intergrowth structure of Li₂MnO₃ and LiMn_0.5Ni_0.5O₂ domains and the second phase is a lithium-deficient layered structure with refined composition Li_0.85(1)Ni_0.57(1)Mn_0.55(1)O₂. The composite cathode has a high initial discharge capacity of 250 mAh/g which drops to 225 mAh/g on the 2^nd discharge cycle. This capacity is maintained on subsequent cycles. Time-resolved in-situ synchrotron XRD data was used to study the changes in the lattice parameters and phase evolution of the two phases during Li-insertion and extraction. [ABSTRACT FROM AUTHOR]