Improving the electrochemical properties of Mn-rich Li1.20[Mn0.54Ni0.13Co0.13]O2 by Nb and F co-doping

Abstract The typical sol-gel method was adopted to synthesize the pristine Li 1.20 [Mn 0.54 Ni 0.13 Co 0.13 ]O 2 and Li 1.20 [Mn 0.54- x Ni 0.13 Co 0.13 Nb x ]O 1.95 F 0.05 ( x  = 0, 0.01, 0.02, 0.03). And the effects of Nb 5+ and F − substitution on the lattice structures, particles morphologies and electrochemical properties were comprehensively studied by using the X-ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and galvanostatic charge-discharge tests. The results demonstrated that the Nb 5+ and F − doping modification could increase the lattice parameter of a and c , and would not obviously change the morphologies of cathode particles. Besides, the electrochemical properties of Li 1.20 [Mn 0.54 Ni 0.13 Co 0.13 ]O 2 were significantly improved after the Nb 5+ and F − doping. Among all samples, the Li 1.20 [Mn 0.52 Ni 0.13 Co 0.13 Nb 0.02 ]O 1.95 F 0.05 delivered the highest discharge capacity of 117.1 mAh g −1 at 5C high rate and the most stable capacity retention of 92.5% at 0.5C rate after 200 cycles. The Electronic Impedance Spectroscopy (EIS) analysis reflected that the Nb 5+ and F − doping could relieve the increase of charge transfer resistance and the ohmic resistance of interaction between electrolyte and cathode during cycling.