Preparation of a high performance LiNi0.6Co0.2Mn0.2O2 cathode material by using citric acid as a complexing agent

Abstract

During the preparation of a LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode material by a hydroxide coprecipitation method, the use of ammonia water (complexing agent) is likely to cause ammonia pollution environmental problems. In this paper, citric acid is used as the complexing agent to replace ammonia water to carry out research on the green preparation of the NCM622 cathode material. The obtained samples were characterized and analyzed by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, particle size distribution and the corresponding electrochemical performance tests. The research results show that the prepared NCM622 precursor has a spherical secondary particle structure, in which the primary particles are tightly bound and the surface of the particles is smooth. After calcination at 800 °C for 12 h, the obtained NCM622 electrode material has the maximum content of spherical secondary particles and a complete layered structure. It also has a low cation mixing degree and high discharge specific capacity and good cycle performance and rate performance. The NCM622 sample has an initial discharge specific capacity of 208.6 mA h g⁻¹ at 0.1C and its capacity retention rate after 100 cycles at 0.5C is as high as 98.0%. All these show that the use of citric acid instead of ammonia water as the complexing agent to prepare the NCM622 electrode material via the hydroxide coprecipitation method is a good strategy, which is not only environmentally friendly, but also can prepare the NCM622 cathode material with better electrochemical performance, showing broad application prospects.