Synthesis and characterization of Zr-doped LiNi0.4Co0.2Mn0.4O2 cathode materials for lithium ion batteries

Abstract

Li(Ni_0.4Co_0.2Mn_0.4)_1−xZr_xO₂ (x = 0, 0.01) was synthesized by a typical sol–gel method. The morphology, structure and electrochemical properties were characterized by SEM, XRD, charge–discharge tests, Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The X-ray diffraction patterns showed that the substituted elements slightly enlarged the interlayer spacing and obtained a higher degree of the well-ordered crystallographic form. The doped sample Li(Ni_0.4Co_0.2Mn_0.4)_0.99Zr_0.01O₂ delivered good electrochemical properties. The initial discharge capacities were 162.4 mA h g⁻¹, 157.5 mA h g⁻¹, 135.3 mA h g⁻¹, 124.3 mA h g⁻¹ at 0.2C, 0.5C, 1.0C and 2.0C, respectively. After 50 cycles, the capacity retentions were 80.5%, 70.9%, 73.4% and 68.5% at the corresponding rates, respectively. The improved electrochemical performance could be ascribed to the enhanced diffusion rate of Li⁺ and improved crystal structure.