Molybdenum doping and MoSi2 coating for enhancing electrochemical performance of LiNi0.6Co0.1Mn0.3O2

Abstract

MoSi2 has a low density, high conductivity, and anti-fluorine structure. Therefore, we prepared MoSi2-modified LiNi0.6Co0.1Mn0.3O2 (NCM613) materials by a solid-state method using the precursors of MoSi2 and NCM613. Analysis using XRD, HRTEM, SEM and XPS reveals that a small amount of Mo from MoSi2 was doped into the NCM613 lattice, and the rest MoSi2 was coated on the material surface. DFT calculations show that Mo atom doping preferentially replaces Ni sites in the NCM613 transition metal layer to form more Ni2+. The capacity retention of the best modified sample NCM-0.5MoSi2 is 74.1% (from 174.0 to 129.0 mAh·g−1) after 300 cycles at 1 C, while the pristine material NCM-0 is only 49.6% (from 171.5 to 85.1 mAh·g−1). Furthermore, the lithium-ion diffusion coefficient of NCM-0.5MoSi2 is 3.44 × 10−12 cm2·s−1, higher than 2.73 × 10−12 cm2·s−1 of NCM-0. Improved electrochemistry results from Mo doping and MoSi2 coating, where Mo doping expands the lattice parameters of NCM613 and MoSi2 coating protects NCM613 from hydrofluoric acid (HF) corrosion. This work achieves the dual effect of Mo doping and MoSi2 coating through the modifier MoSi2, and provides a reference scheme for the improvement of other cathode materials.