Preparation and electrochemical performance of Li-rich layered cathode material, Li[Ni_0.2Li_0.2Mn_0.6]O₂, for lithium-ion batteries

The Li-rich layered cathode material, Li[Ni_0.2Li _0.2Mn_0.6]O₂, was synthesized via a "mixed oxalate" method, and its structural and electrochemical properties were compared with the same material synthesized by the sol-gel method. X-ray diffraction (XRD) shows that the synthesized powders have a layered O ₃-LiCoO₂-type structure with the R-3m symmetry. X-ray photoelectron spectroscopy (XPS) indicates that in the above material, Ni and Mn exist in the oxidation states of +2 and +4, respectively. The layered material exhibits an excellent electrochemical performance. Its discharge capacity increases gradually from the initial value of 228 mA hg^-1 to a stable capacity of over 260 mA hg^-1 after the 10th cycle. It delivers a larger capacity of 258 mA hg^-1 at the 30th cycle. The dQ/dV curves suggest that the increasing capacity results from the redox-reaction of Mn ⁴⁺/Mn³⁺.