Enhancing the electrochemical performance of LiNi0.5Mn1.5O4 cathode material by a conductive LaCoO3 coating

Abstract

A LiNi0.5Mn1.5O4 cathode material was successfully coated with a thin nanolayer of LaCoO3 via a hydrothermal process. The LaCoO3-coated LiNi0.5Mn1.5O4 materials were systematically examined in terms of their crystalline structure, surface morphology, and electrochemical performance. Microscopic structural characterizations indicated that the LaCoO3 coating layer could effectively decrease the Mn3+ ion content to alleviate the Mn2+ dissolution and thus enhance the structural stability of LiNi0.5Mn1.5O4. The content of oxygen vacancies also remarkably increased on the surface of the LaCoO3-coated LiNi0.5Mn1.5O4 materials according to the X-ray photoelectron spectroscopy results. Electrochemical measurements indicated that the 1 wt% LaCoO3-coated LiNi0.5Mn1.5O4 (denoted as LNMO@LCO-1) showed optimal electrochemical behavior in terms of rate capability, long-time cycling performance, and elevated temperature stability. Cyclic voltammetry and electrochemical impedance spectroscopy analyses indicated that the LNMO@LCO-1 exhibited a higher lithium-ion diffusion coefficient and a lower charge-transfer resistance, illustrating that the LaCoO3 coating could accelerate the electrochemical kinetics behavior. Post-cycle surface morphology analyses and material aging experiments confirmed that a thinner solid electrolyte interface layer was generated on the surface of LNMO@LCO-1, which could alleviate the side reactions and reduce the surface impedance. This study demonstrated that LaCoO3, as a coating material, can enhance the electrochemical performance of LiNi0.5Mn1.5O4.