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

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.