Promoting electrochemical performances of LiNi0.5Mn1.5O4 cathode via YF3 surface coating

Abstract

High voltage LiNi0.5Mn1.5O4 cathodes are of prime importance for the development of next generation lithium-ion batteries (LIBs) with high energy density. LiNi0.5Mn1.5O4, however, always was attacked by the generated HF from the electrolyte decomposition during cycling, leading to instable surface structure and poor Li+ diffusion kinetic property. In this regard, YF3 with good thermal stability and excellent structural stability in the HF containing electrolyte, is chosen as coating layer to modify the surface of LiNi0.5Mn1.5O4. Ex-situ electrochemical impedance spectroscopy study and inductively coupled plasma analysis indicate that YF3 coating layer on the surface of LiNi0.5Mn1.5O4 could act as protect medium to effectively suppress side reactions between the LiNi0.5Mn1.5O4 surface and electrolyte, and thus enhance its structural stability and kinetics properties during repeated electrochemical reactions. As a result, LiNi0.5Mn1.5O4 after YF3 modification shows the improved capacity retention of 84% after 100 cycles at 0.1C, and 78 mAh g−1 could be obtained at 2C, much higher than those of the pristine LiNi0.5Mn1.5O4 cathode (78%, 24 mAh g−1). Furthermore, differential scanning calorimetry result confirms the enhanced thermal stability of LiNi0.5Mn1.5O4 after YF3 coating. These findings open up chance to prepare high performance LiNi0.5Mn1.5O4 cathode and promote development of LIBs with high energy density.