Facile synthesis of Li₂ZrO₃-modified LiNi_0.5Mn_0.5O₂ cathode material from a mechanical milling route for lithium-ion batteries

Li₂ZrO₃-modified LiNi_0.5Mn_0.5O₂ materials with improved electrochemical performance were directly synthesized by a simple mechanical milling route with ZrO₂, Li₂CO₃ and Ni_0.5Mn_0.5(OH)₂ precursors and a high temperature calcination in air atmosphere. The influences of ZrO₂ contents on the microstructures and electrochemical properties of LiNi_0.5Mn_0.5O₂ electrode materials were investigated through X-Ray diffraction, scanning electron microscope, energy dispersive spectroscopy and electrochemical tests. The results showed that ZrO₂ can be completely converted into Li₂ZrO₃ in the form of a coating layer covering the surface of LiNi_0.5Mn_0.5O₂ after a heat treatment process. Li₂ZrO₃ coating can be formed and dispersed homogenously on the surface of 1 mol% Li₂ZrO₃-modified LiNi_0.5Mn_0.5O₂ materials. The electrochemical tests confirmed 1 mol% Li₂ZrO₃-modified LiNi_0.5Mn_0.5O₂ materials exhibited the best discharge capacity of 158.3 mAh g⁻¹ after 100 cycles between 2.75 and 4.35 V at 0.2 C, with an excellent capacity retention of 97.2% and higher discharge capacity at −20 °C than that of the pristine LiNi_0.5Mn_0.5O₂. The enhanced cycling stability and low temperature performance may be attributed to the remarkable synergistic effects of Li₂ZrO₃ protective layer and its homogeneous distribution on LiNi_0.5Mn_0.5O₂ surface with low Li/Ni cation mixing, high electric conductivity and good structure stability.