High capacity lithium-manganese-nickel-oxide composite cathodes with low irreversible capacity loss and good cycle life for lithium ion batteries

We report a method to eliminate the irreversible capacity of 0.4Li2MnO3·0.6LiNi0.5Mn0.5O2(Li1.17Ni0.25Mn0.583O2) by decreasing lithium content to yield integrated layered-spinel structures. XRD patterns, High-resolution TEM image and electrochemical cycling of the materials in lithium cells revealed features consistent with the presence of spinel phase within the materials. When discharged to about 2.8 V, the spinel phase of LiM2O4 (M=Ni, Mn) can transform to rock-salt phase of Li2M2O4 (M=Ni, Mn) during which the tetravalent manganese ions are reduced to an oxidation state of 3.0. So the spinel phase can act as a host to insert back the extracted lithium ions (from the layered matrix) that could not embed back into the layered lattice to eliminate the irreversible capacity loss and increase the discharge capacity. Their electrochemical properties at room temperature showed a high capacity (about 275 mAh g-1 at 0.1 C) and exhibited good cycling performance.