Enhancing the structural stability and capacity retention of Ni-rich LiNi0.7Co0.3O2 cathode materials via Ti doping for rechargeable Li-ion batteries: Experimental and computational approaches

Highlights: • Titanium doped LiNi_0.7Co_0.3O₂ was synthesized by self-propagation combustion method. • Titanium doping expand the lattice parameter of c-axis and lowered the cation mixing content in the crystal structure. • LiNi_0.6Co_0.3Ti_0.1O₂ exhibits better phase reversibility and structural stability. • Density Functional Theory reveals that Li diffuse efficiently in LiNi_0.6Co_0.3Ti_0.1O₂ cathode materials owing to larger atomic distance of Li-O. -- Abstract: The Ni-rich cathodes are considered as the next generation candidate cathode material of lithium-ion batteries due to their high-energy–density and environmentally friendly. In this study, the Ni-rich, LiNi_0.7Co_0.3O₂ cathodes material was doped by titanium (Ti) via a self-propagating combustion method. The role of Ti species and its effects on the structural and electrochemical performance of the cathode materials were investigated through experimental and first principles studies. From the XRD results, all materials possessed a single phase with a hexagonal layered structure of the R-3m space group. The Rietveld refinement revealed that the lattice of the Ti-doped LiNi_0.7Co_0.3O₂ sample was found to be expanded in the c-axis and has a lower cation mixing as compared to the pristine samples, which can ease the movement of Li-ions during the delithiation/lithiation process. After 70th cycle, the discharge capacity of the Ti-doped LiNi_0.7Co_0.3O₂ sample possess an excellent capacity retention of 91.9% with a specific discharge capacity of 132.3 mAhg⁻¹ as compared to the pristine sample with only has 86.2 mAhg⁻¹. This can be explained by first-principles study where it was found that the Li-O distances for LNCT become expand after the delithiation process which ease the Li-ions diffusion during cycling. As a whole, the addition of Ti species into the Ni-rich layered cathode materials was found to stabilise the crystal structure of LiNi_0.7Co_0.3O₂ and subsequently improved the lithium-ion kinetics of the layered cathode materials_. Apart from lithium nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminium oxide (NCA), this study demonstrated that LiNi_0.6Co_0.3Ti_0.1O₂ can also serve as potential cathode material for rechargeable Li-ion batteries.