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

Highlights: • The LaCoO₃-coated LNMO cathode material was successfully prepared via a hydrothermal process. • Significant increase of Li⁺ diffusivity and decrease of Mn³⁺ ion contents could be obtained in the LaCoO₃-coated LNMO. • LNMO@LCO-1 exhibited superior rate performance of 105.8 mAh g⁻¹ at 5 C and excellent cycling stability with a high capacity retention of 82.8% after 500 cycles at 5 C and 25 °C. • LNMO@LCO-1 exhibited an excellent high-temperature cycling stability with a high capacity retention of 99.5% after 200 cycles at 1 C and 55 °C. • The improved electrochemical performance of LNMO@LCO-1 material was related to a lower charge-transfer resistance, a higher Li⁺ diffusion coefficient, and a thinner solid electrolyte interface layer after LaCoO₃ coating. -- Abstract: A LiNi_0.5Mn_1.5O₄ cathode material was successfully coated with a thin nanolayer of LaCoO₃ via a hydrothermal process. The LaCoO₃-coated LiNi_0.5Mn_1.5O₄ 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 LiNi_0.5Mn_1.5O₄. The content of oxygen vacancies also remarkably increased on the surface of the LaCoO₃-coated LiNi_0.5Mn_1.5O₄ materials according to the X-ray photoelectron spectroscopy results. Electrochemical measurements indicated that the 1 wt% LaCoO₃-coated LiNi_0.5Mn_1.5O₄ (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 LiNi_0.5Mn_1.5O₄.