Influence of Nb Doping on Electrochemical Performance of Nanostructured Cation Disordered Li1+x/100Ni1/2-x/100Ti1/2-x/100Nbx/100O₂ Composites Cathode for Li-Ion Batteries.

Li-excess cation-disordered rock-salts Li1+x/100Ni1/2-x/100Ti1/2-x/100Nbx/100O₂ (x = 0, 5, 10, 15, 20) were synthesized in this study, and effects of Nb doping on their electrochemical performance were also investigated. X-ray diffraction (XRD) indicated that the rock-salt structure was maintained, but with lower crystallization. The scanning electron microscopy (SEM) displayed Nb-doped samples' morphology and particles were uniformly distributed within 100 nm. The transmission electron microscopy (TEM) analysis also confirmed that these Nb-doped samples still maintained the cationdisordered rock-salt structure. Charge-discharge test showed that the electrochemical performance was greatly improved after Nb-doping. The Li1.2Ni0.3Ti0.3Nb0.2O₂ sample delivered highest capacity of up to 226.5 mAh·g-1, at 20 mA·g-1 density. Moreover, the sample still delivered 130 mAh·g-1 capacity of even 400 mA·g-1 density. This result indicates that the Nb-doping improved the cycling performance and rate capacity. In addition, electrochemical impedance spectroscopy (EIS) test showed that the Nb-doping further enhanced mobility of Li-ions when forming the 0-TM channel.