Synthesis and charge–discharge properties of LiNi 1− x− yCo xM yO 2 (M=Al, Ga) compounds

Abstract

The synthesis and electrochemical characteristics of LiNi 1− x− y Co x M y O 2 (M=Al, Ga) compounds for use as positive-electrode (cathode) materials in rechargeable lithium batteries are investigated. Layered LiNi 1− x− y Co x M y O 2 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 LiNi 1− x− y Co x M y O 2 are examined by impedance spectroscopy and charge–discharge tests in half-cell and practical lithium batteries. The discharge capacities of the LiNi 1− x− y Co x M y O 2 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 LiNi 0.8Co 0.18Ga 0.02O 2 compound, in particular, delivers approximately 210 mAh g −1 of discharge capacity with good reversibility.