RETRACTED: Hydrothermal MgF2 surface treatment of LiNi0.5Mn1.5O4 high voltage cathode materials for lithium-ion batteries

Abstract

The LiNi0.5Mn1.5O4 cathode material is one of the popular electrode materials for research in the field of full cell operating at high voltage over 4.9 ​V. With increasing the high voltage, the spinel LiNi0.5Mn1.5O4 (LNMO) suffers from irreversible capacity fading during cycling and limited cycle life. In this work, it is shown the MgF2 surface modification of the LiNi0.5Mn1.5O4 cathode material via a facile hydrothermal method with an additional heat treatment step. The effect of MgF2 coating amount on the electrochemical cycling behavior of the LiNi0.5Mn1.5O4 electrode is investigated at the high upper voltage limit of 4.9 ​V. The cycling performance and rate capability of the LNMO electrode are related to the amount of MgF2 coating. The electrochemical performance of the MgF2-coated LNMO decreased with increasing MgF2 coating amount but showed enhanced properties, compared to the pristine material. The 1 ​wt% MgF2-coated LNMO have the best electrochemical performance, showing higher specific capacities and lower surface resistance after 150 cycles at various current densities. Obtained the electrochemical performance suggested that the MgF2 thin coating layer (1 ​wt%) obtained via the hydrothermal method plays an important role in stabilizing the positive electrode/electrolyte interface and the host structure, and can prevent the formation of side reaction components and improve lithium-ion diffusion resulting in the stabilization of cathode surface compared to the pristine material.