Effect of Niobium Doping on Structural Stability and Electrochemical Properties of LiNiO 2 Cathode for Li-Ion Batteries

Abstract

LiNiO 2 , a promising cobalt-free cathode, suffers from poor cyclic stability and inferior rate performance due to structural degradation. A strategy based on the synergistic effect of a strong Nb–O bond (753 kJ mol −1 ), high valence state (Nb 5+ ), and larger ionic radius (0.64 Å) was developed to improve the properties of LiNiO 2 . The synergistic effects can effectively improve lattice stability, lower Li + /Ni 2+ cation mixing, expand LiO 6 -slab spaces, enhance the conductivity and inhibit the H2–H3 phase transition, which can enhance the stability of the layered structure, accelerate Li + diffusion and alleviate mechanical damage. Therefore, LiN 0.99 Nb 0.01 O 2 exhibits higher capacity retention (91.4% after 100 cycles at 0.5C) and superior rate capability (143 mAh g −1 at 5C). As a comparison, the data of bare LiNiO 2 is 69.2% and 127 mAh g −1 under the same conditions. These results further demonstrate the effectiveness of the proposed doping strategy.