Enhancing Structural Stability and Electrochemical Properties of Co-Less Ni-Rich Layer Cathode Materials by Fluorine and Niobium Co Doping

A solid-state approach was used to synthesize Li(Ni0.925Co0.03Mn0.045)0.996Nb0.004O1.98F0.02 with double ion doping. The structure parameters, micromorphology, and element valence distribution of all materials were thoroughly investigated by XRD, SEM, EDS, XPS, and HR-TEM. The results show that the distribution of F and Nb is uniform both on the surface and inside the particles and that F and Nb ions have an impact on the valence state of Ni ions on the surface of the material. In addition, the lattice parameter c is raised and the (003) crystal plane spacing is widened by the introduction of both F and Nb ions. The Li(Ni0.925Co0.03Mn0.045)0.996Nb0.004O1.98F0.02 electrode shows a higher discharge specific capacity (169.12 mAh g–1) at 10C and excellent cycling performance with a capacity retention of 83.60% after 150 cycles. Comparison of CV, dV/dq, EIS, SEM, and HR-TEM after cycling for all electrodes reveals that the particles doped with F and Nb maintained intact morphology and showed varying degrees of decrease in polarization and impedance.