Electrochemical performance of a layered-spinel integrated Li[Ni_1/3Mn_2/3]O₂ as a high capacity cathode material for li-ion batteries

Li[Ni_1/3Mn_2/3]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[Li_1/3Mn_2/3]O₂ phase as the major component, and rhombohedral (LiNiO₂), spinel (LiNi_0.5Mn_1.5O₄), and rock salt Li_0.2Mn_0.2Ni_0.5O 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, LiNi_0.5Mn_1.5O₄ 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[Ni_1/3Mn_2/3]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[Ni_1/3Mn_2/3]O₂ electrodes exhibit better electrochemical stability than spinel LiNi_0.5Mn_1.5O₄ electrodes when cycled at 45 °C.