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 1/3 Mn 2/3 ]O 2 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 1/3 Mn 2/3 ]O 2 phase as the major component, and rhombohedral (LiNiO 2 ), spinel (LiNi 0.5 Mn 1.5 O 4 ), and rock salt Li 0.2 Mn 0.2 Ni 0.5 O 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 0.5 Mn 1.5 O 4 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 1/3 Mn 2/3 ]O 2 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 1/3 Mn 2/3 ]O 2 electrodes exhibit better electrochemical stability than spinel LiNi 0.5 Mn 1.5 O 4 electrodes when cycled at 45 °C.