Effect of Nb⁵⁺ Doping and LiNbO₃ Coating on the Structure and Surface of a LiNi_0.8Mn_0.2O₂ Cathode Material for Lithium-Ion Batteries

Layered LiNixMn1−xO2 structures with high discharge specific capacity and low cost are anticipated as the next-generation of high-energy density cathode active materials. However, the mixed arrangement of Li+ and Ni2+ in the cathode materials affects structural stability. Here, Nb5+ was doped into the structure of LiNi0.8Mn0.2O2 (NM82) to broaden the lithium-ion migration channels and alleviate the degree of ion mixing. LiNbO3 particle was coated on the surface of LiNi0.8Mn0.2O2 to form a spherical compound and reduce the erosion of HF and the dissolution of transition metals, which helped ameliorate the cyclic and structural stabilities of cathode materials. NM82 modified 1% Nb2O5 (LN/NM82-1.0) exhibited maximum discharge specific capacitance (177.7 mAh g−1 at 1.0C following 200 cycles) and excellent thermal stability (189.0 mAh g−1 at 1.0C following 200 cycles at 60 °C). The corresponding capacity retentions of this material were 87.54% and 85.37%, as LiNbO3 particle coating on the surface of NM82 decreased polarization and charge transfer resistor. Nb5+ in the host structure suppressed structural degradation and enhanced discharge capacity. This study determined the influence of Nb5+ substitution and LiNbO3 cladding on the structure and surface of LiNi0.8Mn0.2O2 and provides insights into commercial application of high-energy density layered structures of LiNixMn1−xO2 cathode materials.