Enhanced Electrochemical Properties of Lithium-Rich Cathode Materials by Magnesium Borate Surface Coating

摘要

Magnesium borate oxide (MBO) coated lithium-rich layered Li1.2Mn0.54Co0.13Ni0.13O2 particles are synthesized via a wet chemical coating method. The X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and X-ray photoelectron spectrometer results indicate that the cathode particles are uniformly covered with a MBO layer. The results of charge/discharge tests show that the MBO-coated electrode has enhanced electrochemical properties both in rate capability and cycling stability compared to the bare one. Specifically, 3 wt. % MBO-coated sample has capacity retention of 98.3 %, much more than the bare one of only 79.2 % after 100 cycles at 1 C. Furthermore, the MBO-coated electrode retains a superior high-rate capacity of 90 mAh g(-1) at 10 C. The remarkably enhanced rate capability and cycling stability of MBO-coated electrode is ascribed to the MBO coating layer efficiently isolating the bulk Li1.2Mn0.54Co0.13Ni0.13O2 from direct contact with the electrolyte, and facilitating both charge transfer reaction and the kinetics of lithium ion diffusion through the surface layer.