The high-voltage LiNi_0.5Mn_1.5O₄ spinel cathode is becoming more attractive for lithium-ion batteries because it offers fast, 3-dimesional Li-ion diffusion with high power density. However, its commercialization is hampered by capacity fade due to the aggressive reaction between the cathode and the electrolyte with dissolution of the active material observed under high-voltage operating conditions.

In this study, a Li-ion conductor, Li₃VO₄, was coated onto the micron-sized LiNi_0.5Mn_1.5O₄ powders via wet chemistry followed by a low temperature thermal-treatment.

The experimental results showed that Li₃VO₄-coated LiNi_0.5Mn_1.5O₄ cathode material exhibits much better cycling stability and rate capability than pristine LiNi_0.5Mn_1.5O₄ at both room temperature (25°C) and high temperatu...[ Read more ]

The high-voltage LiNi_0.5Mn_1.5O₄ spinel cathode is becoming more attractive for lithium-ion batteries because it offers fast, 3-dimesional Li-ion diffusion with high power density. However, its commercialization is hampered by capacity fade due to the aggressive reaction between the cathode and the electrolyte with dissolution of the active material observed under high-voltage operating conditions.

In this study, a Li-ion conductor, Li₃VO₄, was coated onto the micron-sized LiNi_0.5Mn_1.5O₄ powders via wet chemistry followed by a low temperature thermal-treatment.

The experimental results showed that Li₃VO₄-coated LiNi_0.5Mn_1.5O₄ cathode material exhibits much better cycling stability and rate capability than pristine LiNi_0.5Mn_1.5O₄ at both room temperature (25°C) and high temperature (60°C). The sample coated with 2 wt. % Li₃VO₄ shows the optimum electrochemical performance with a capacity of 124.6 mAh/g at 20C (2940 mA/g) at room temperature, compared to that of 112.7 mAh/g for the pristine sample. The capacity retention at 1C (147 mA/g) and 60°C is 90.5% at cut-off voltage of 4.9V, while the pristine LiNi_0.5Mn_1.5O₄ retains only 83.9% of its initial capacity. XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) results reveal that the Li₃VO₄ coating layer reinforced the surface of matrix material, which benefited structural stability of LiNi_0.5Mn_1.5O₄ during long-term cycling. CV (cyclic voltammetry) and EIS (electrochemical impedance spectroscopy) tests indicate that the improvement of the electrochemical performances could be attributed to a higher Li⁺ conductivity, the suppression of Mn and Ni dissolution from LiNi_0.5Mn_1.5O₄ and the decreased polarization during cycling with Li₃VO₄ layer on LiNi_0.5Mn_1.5O₄ surface acting as a relatively stable protective barrier as well as an excellent Li-ion conductor. Furthermore, Li₃VO₄ coating remarkably reduced the amount of the heat released in DSC measurement, thus improved the thermal stability of LiNi_0.5Mn_1.5O₄.