Understanding the role of Na-doping on Ni-rich layered oxide LiNi0.5Co0.2Mn0.3O2

Na-doped Ni-rich layered oxide LiNi0.5Co0.2Mn0.3O2 cathode materials are synthesized via coprecipitation method in this work. The crystal structure, thermal stability as well as electrochemical performance are studied. Results show that when the Na-doping amount is less than and equal to 2%, the samples can exhibit better electrochemical performance than the parent compound. One reason is that the Na doping can reduce the cationic mixing in the compound, as confirmed by X-Ray powder diffraction (XRD). Beside, results from X-ray photoelectron spectroscopy (XPS) and galvanostatic intermittent titration technique (GITT) show that the introduced sodium can also impact the chemical environment of lithium, making the latter become more easily de-intercalated from the bulk material. However, as the Na-doping amount increases, the electrochemical properties of the samples were deteriorated. Furthermore, results from differential scanning calorimetry (DSC) measurement indicate that the added Na+ is also beneficial for improving the thermal stability of the layered oxide. (C) 2016 Elsevier B.V. All rights reserved.