Colloidal Synthesis and Electrochemistry of Surface Coated Nano-LiNi0.80Co0.15Al0.05O2

Nano-crystalline LiNi0.80Co0.15Al0.05O2 with and without an electrochemically inactive Al2O3 surface coating has been successfully prepared by a colloidal synthesis method followed by a chemical lithiation reaction. In situ high temperature X-ray diffraction studies evidenced the slowness of the lithiation reaction due to diffusion and suggested longer calcination holding times at temperatures below 500 degrees C. At 550 degrees C, lithiated compounds were obtained although calcinations to 750 degrees C are necessary to obtain ordered layered structures. Ex situ XRD studies and cyclic voltammograms revealed a single-phase solid solution mechanism taking place during the first charge unlike the two-phase reaction activation mechanism seen for micron-sized material. While nano-crystalline LiNi0.80Co0.15Al0.05O2 exhibits cycle stability at 2.4mA g(-1) and a good rate capability even at 240 mA g(-1) in the galvanostatic tests, the specific charge of the surface coated material fades more quickly. These results are caused by the material characteristics such as small particle size and significant amount of microstrains, high degree of cation mixing, and increased compositional inhomogeneity among the nano-particles, compared to the uncoated material. (C) 2017 The Electrochemical Society. All rights reserved.