Electrochemical Performance of a Layered-Spinel Integrated Li[Ni1/3Mn2/3]O2 as a High Capacity Cathode Material for Li-Ion Batteries

Li­[Ni1/3Mn2/3]­O2 was synthesized by a self-combustion reaction (SCR), characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, and studied as a cathode material for Li-ion batteries at 30 °C and 45 °C. The structural studies by XRD and TEM confirmed monoclinic Li­[Li1/3Mn2/3]­O2 phase as the major component, and rhombohedral (LiNiO2), spinel (LiNi0.5Mn1.5O4), and rock salt Li0.2Mn0.2Ni0.5O as minor components. The content of the spinel phase increases upon cycling due to the layered-to-spinel phase transition occurring at high potentials. A high discharge capacity of about 220 mAh g–1 is obtained at low rate (C/10) with good capacity retention upon cycling. However, LiNi0.5Mn1.5O4 synthesized by SCR exhibits a discharge capacity of about 190 mAh g–1 in the potential range of 2.4–4.9 V, which decreases to a value of 150 mAh g–1 after 100 cycles. Because of the presence of the spinel component, Li­[Ni1/3Mn2/3]­O2 cathode material exhibits part of its capacity at potentials around 4.7 V. Thus, it can be considered as an interesting high-capacity and high-voltage cathode material for high-energy-density Li-ion batteries. Also, the Li­[Ni1/3Mn2/3]­O2 electrodes exhibit better electrochemical stability than spinel LiNi0.5Mn1.5O4 electrodes when cycled at 45 °C.