Using a Couette–Taylor vortex flow reactor to prepare a uniform and highly stable Li[Ni0·80Co0·15Al0.05]O2 cathode material

Abstract

This study mainly focuses on the preparation technique of Ni-rich NCA hydroxide by a Couette–Taylor flow reactor (CTFR), by systematically optimizing the preparation parameters, including cylinder rotation speed and calcination temperature to study its electrochemical performance. Because of the uniform mixing and constant fluid motion of the Taylor vortex, we obtained spherical and uniform Ni0·80Co0·15Al0·05(OH)2 particles. The rotation speed of the inner cylinder determined the degrees of particle agglomeration and growth. X-ray diffraction and Rietveld refinement revealed that the sample prepared at 600 rpm had relatively large particles and a high degree of crystallinity; when calcined to 750 °C, it featured much smaller primary particles, a comparatively lower degree of cation mixing, and better layer structure ordering. The Ni-rich LiNi0·80Co0·15Al0·05O2 prepared under the optimal conditions delivered a high discharge capacity of 190.6 mAh g−1 at 0.1C, on par with that of commercially available NCA powders; it also exhibited a remarkable improvement in rate capability, with a discharge capacity of 138 mAh g−1 at 10C (101 mAh g−1 for a commercial sample). In long cycle life tests, the prepared NCA sample retained a high capacity (87.4%) after 100 cycles at 1C, compared with 70.0% for the commercial sample. Furthermore, cyclic voltammetry and electrochemical impedance spectroscopy demonstrated the importance of the calcination temperature on the electrochemical performance and structural stability of our Ni-rich cathodes. Our as-prepared NCA cathode materials, obtained using a CTFR, appear to have great potential for application in Li-ion batteries.