Effects of Gd3+ doping on the microstructure and electrochemical properties of Li1.20[Mn0.54Ni0.13Co0.13]O2 as cathode for lithium-ion batteries

To enhance the electrochemical properties of the Mn-based lithium-rich layered cathode materials, Li-1.20[Mn0.54-x Gd (x) Ni0.13Co0.13]O-2 (x = 0, 0.01, 0.02 and 0.03) were synthesized by using the carbonate co-precipitation method. The X-ray diffraction, scanning electron microscope, galvanostatic charge-discharge tests and electrochemical impedance spectroscopy techniques have been carried out to investigate the influences of the Gd3+ doping modification. And the results showed the lower cation mixing degree and superior electrochemical properties were obtained for the LMNCO by the Gd3+ doping. With the Gd3+ doping amount increasing, the capacity retentions after 100 cycles enhanced from 88.5 to 90.9% and then decrease to 86.7% with x = 0.01, 0.02 and 0.03, respectively. While the un-doped LMNCO only delivered the capacity retention of 85.1%. Besides, the discharge capacity of Li-1.20[Mn0.52Gd0.02Ni0.13Co0.13]O-2 was 29.4 mAh g(-1) larger than that of un-doped sample at 5 C high rate. The electrochemical impedance spectroscopy results indicated that the Gd3+ doping modification could restrain the growth speed of charge transfer impedance of LMNCO during the charge and discharge process.