Synthesis and electrochemical studies of the 4 V cathode, Li(Ni2/3Mn1/3)O2

Layered Li(Ni2/3Mn1/3)O2 compounds are prepared by freeze-drying, mixed carbonate and molten salt methods at high temperature. The phases are characterized by X-ray diffraction, Rietveld refinement, and other methods. Electrochemical properties are studied versus Li-metal by charge–discharge cycling and cyclic voltammetry (CV). The compound prepared by the carbonate route shows a stable capacity of 145 (±3) mAh g−1 up to 100 cycles in the range 2.5–4.3 V at 22 mA g−1. In the range 2.5–4.4 V at 22 mA g−1, the compound prepared by molten salt method has a stable capacity of 135 (±3) mAh g−1 up to 50 cycles and retains 96% of this value after 100 cycles. Capacity-fading is observed in all the compounds when cycled in the range 2.5–4.5 V. All the compounds display a clear redox process at 3.65–4.0 V that corresponds to the Ni2+/3+–Ni3+/4+ couple.