Synthesis and Electrochemical Characterization of Pr-doped Li-rich Mn-based Layered Oxides Li[Li0.2Mn0.54Ni0.13Co0.13]O2 for Li-ion Batteries

Li-rich Mn-based layered oxides, which are considered as solid solutions of xLi2MnO3.(1-x)LiMn0.33Ni0.33Co0.33)O2 have attracted much attention for their high theoretical capacity (>250 mAh g-1) and operating voltage (>3.5 V vs. Li/Li+). In this research work, synthesis, electrochemical investigation of Li1.2Mn0.54Ni0.13Co0.13O2 and influence of the doping Pr3+ ion on its structure and properties has been investigated. These Li-rich cathode materials with the general formula of Li1.2Mn0.54-xNi0.13Co0.13PrxO2 (x=0, 0.01, 0.03, 0.05) have been synthesized by a hydrothermal method. The synthesis of samples and increase of cell volume was confirmed by X-ray diffraction. The stoichiometric ratios for x=0.03 according to experimental formula of Li1.2Mn0.50Ni0.12Co0.13Pr0.02O2 were determined by inductively coupled plasma (ICP) method. In order to better understand the morphology of the synthesized samples, SEM analysis was applied and in order to specify particles distribution, EDS images were prepared. The purpose of this study is achieving better electrochemical properties such as cycle performance. The ability of these materials as a cathode in Li-ion batteries was studied with cyclic voltammetry, Electrochemical Impedance Spectroscopy (EIS) and galvanostatic charge/discharge methods. The doped compound with x=0.03 exhibited the higher columbic efficiency and cycle performance, which delivering an initial discharge capacity of 247 mAh g-1 at 0.05 C and 195 mAh g-1 after 10 cycles with capacity retention of 79%, compared to pristine sample with capacity retention of 62% retention. The columbic efficiency of the pristine sample was promoted from 79% to 83% for the doped sample. The results of EIS demonstrated that doping with Pr3+ ions reduces the charge transfer resistance from 696 μΩ to 252 μΩ and facilitates the Li ion diffusion