Surface coating of lithium-manganese-rich layered oxides with delaminated MnO₂ nanosheets as cathode materials for Li-ion batteries

Lithium-manganese-rich layered oxides are of great importance as cathode materials for rechargeable lithium batteries. In this article, Li _1.2Mn_0.567Ni_0.167Co_0.066O ₂ is prepared by a co-precipitation method, and the delaminated MnO₂ nanosheets with different amounts, 1 wt%, 3 wt% and 5 wt%, are introduced for coating this material for the first time. The structure and morphology of these materials have been investigated via X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations. The results clearly demonstrate that the surface of lithium-manganese-rich layered oxides is covered by continuous delaminated MnO₂ nanosheets. The electrochemical properties including the discharge capacity, initial coulombic efficiency, rate capability and cycle stability of these coated materials have been greatly enhanced, which are obviously related to the delaminated MnO₂ nanosheet coating with good electrochemical activity and low charge transfer resistance. Moreover, the lithium-manganese-rich layered oxide coated with 3 wt% delaminated MnO ₂ nanosheets presents the best comprehensive electrochemical properties as well as improves the initial discharge capacity and coulombic efficiency by 299 mA h g^-1 and 88% respectively; the capacity retention after 50 cycles also reaches 93%, and the discharge capacity can be 157 mA h g^-1 even at a 5 C discharge rate.