Electrochemical and lithium-ion transport properties of layered Li-rich Li1.10(Ni0.32X0.01Co0.33Mn0.33)O2(X = Dy/Gd/Ho) positive electrodes

Abstract

Layer structured Li_1.10(Ni_0.32X_0.01Co_0.33Mn_0.33)O₂ (X = Dy/Gd/Ho) compounds were synthesized via the microwave assisted solvothermal route. The impacts of doping on the electrical and electrochemical properties of Li_1.10 (Ni_0.32X_0.01Co_0.33Mn_0.33)O₂ compounds were investigated. Rietveld refined XRD pattern showed Li_1.10 (Ni_0.32X_0.01Co_0.33Mn_0.33)O₂ compounds with layered hexagonal structure. SEM images revealed the compounds with micrometer sized grains. The Li_1.10 (Ni_0.33Co_0.33Mn_0.33)O₂ compound delivered an initial discharge capacity of 197 mAh/g at 0.2C and retained a capacity of 163mAh/g after 50^th cycle in the voltage window of 2.5-4.6V. The cycling stability of Li_1.10(Ni_0.33Co_0.33Mn_0.33)O₂ compound was improved with rare earth doping. Li_1.10(Ni_0.32Dy_0.01Co_0.33Mn_0.33)O₂ compound delivered the discharge capacity of 166 mAh/g after50^th cycle in the potential window 2.5-4.6V at 0.2C with 100% capacity retention. AC impedance studies displayed the electrical conductivity in the order of 10^-6 S/cm. Wagner polarization analysis revealed the improvement in electronic transference number via rare earth doping.