Studies of a layered-spinel Li[Ni1/3Mn2/3]O2 cathode material for Li-ion batteries synthesized by a hydrothermal precipitation

This work continues our research on integrated “layered-spinel” high-capacity cathode material Li[Ni1/3Mn2/3]O2 [30]. This material operated at potentials >4.6 V and demonstrated an advantageous cycling stability compared to high-voltage spinel LiNi0.5Mn1.5O4. In the present study, the Li[Ni1/3Mn2/3]O2 material was synthesized by a hydrothermal precipitation. The Rietveld analysis of XRD patterns indicated the presence of two layered structure phases: a monoclinic Li2MnO3 (about 58%) and a rhombohedral LiNiO2 (24%), along with spinel LiNi0.5Mn1.5O4 (17%) and rock salt Li0.2Mn0.2Ni0.5O (1%) phases. We demonstrate an interesting phenomenon of this electrode activation upon cycling from 100 to 220 mAh g−1 in the potential range of 2.3-4.9 V and stabilization followed by lowering the capacity to 89.5% of the maximal value after 100 cycles. It is suggested that the high capacity resulted from the activation of Li[Li1/3Mn2/3]O2 and participation of spinel component upon cycling to potential ≥4.5 V.