Synthesis and characterization of nanocrystalline layer Li(Li0.21Mn0.54Ni0.125Co0.125−x)AlxO2 for lithium-ion batteries application

In this study, undoped and doped nanopowders of Li(Li 0.21 Mn 0.54 Ni 0.125 Co 0.125− x )Al x O 2 ( x = 0, 0.02%, were 0.05, 0.075 and 10%) of Al impurity by the sol–gel method, and the effect of different percentages investigated on the structure and electrochemical properties of the samples. Structure and electrochemical properties of samples characterized by thermo-gravimetric analysis, differential thermal analysis (DTA), x-ray diffraction (XRD), field-scattering microscopy (FESEM), x-ray energy spectroscopy (EDS), Transmission Electron Microscopy (TEM), infrared spectroscopy (FTIR), and their results were evaluated. XRD tests were carried out to explore the samples’ structure, showing that the α-NaFeO 2 structure with R - 3 m space group for all the samples and structures samples does not change up to Al 0.10%. The FESEM images have shown that these samples have an assembly of cubic and hexagonal particles for doped and undoped Al impurity nanopowders. The particle size of undoped nanopowders is in the range of 30–100 nm, while with increased Al-doped in this material, the size of nanopowders seems to be decreased. The chemical analysis of EDS has proven the presence of Al in the samples. The shape of particles of TEM figures is nearly hexagonal and has the average grain size 60–100 nm. TG/DTA analysis for doped 0.05% Al and undoped samples showed weight loss in these nanopowders. In FTIR, the connection bonds and chemical elements used in this cathode were investigated. Electrochemical performance studied by charge–discharge test for nanopowders undoped and doped with 0.05% Al. The optimum amount of Al for the Co is x = 0.05 in consideration of the higher specific capacity rather than undoped nanopowders.