Effect of Nb 5+ Doping and LiNbO 3 Coating on the Structure and Surface of a LiNi 0.8 Mn 0.2 O 2 Cathode Material for Lithium-Ion Batteries

Layered LiNi x Mn 1−x O 2 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 Ni 2+ in the cathode materials affects structural stability. Here, Nb 5+ was doped into the structure of LiNi 0.8 Mn 0.2 O 2 (NM82) to broaden the lithium-ion migration channels and alleviate the degree of ion mixing. LiNbO 3 particle was coated on the surface of LiNi 0.8 Mn 0.2 O 2 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% Nb 2 O 5 (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 LiNbO 3 particle coating on the surface of NM82 decreased polarization and charge transfer resistor. Nb 5+ in the host structure suppressed structural degradation and enhanced discharge capacity. This study determined the influence of Nb 5+ substitution and LiNbO 3 cladding on the structure and surface of LiNi 0.8 Mn 0.2 O 2 and provides insights into commercial application of high-energy density layered structures of LiNi x Mn 1−x O 2 cathode materials.