Synthesis and charge–discharge properties of LiNi1−x−yCoxMyO2 (M=Al, Ga) compounds

The synthesis and electrochemical characteristics of LiNi1−x−yCoxMyO2 (M=Al, Ga) compounds for use as positive-electrode (cathode) materials in rechargeable lithium batteries are investigated. Layered LiNi1−x−yCoxMyO2 is synthesized by solid-state reaction. The composition, structure, morphology, and particle size of the samples are characterized by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The electrochemical properties of LiNi1−x−yCoxMyO2 are examined by impedance spectroscopy and charge–discharge tests in half-cell and practical lithium batteries. The discharge capacities of the LiNi1−x−yCoxMyO2 compounds containing Al and Ga are above 190 mAh g−1. Cells using these cathode materials show good low-temperature discharge and high-rate discharge performance, as well as good cycleability. The LiNi0.8Co0.18Ga0.02O2 compound, in particular, delivers approximately 210 mAh g−1 of discharge capacity with good reversibility.