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

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, LiNi0.7Co0.3O2 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 LiNi0.7Co0.3O2 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 LiNi0.7Co0.3O2 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 LiNi0.7Co0.3O2 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 LiNi0.6Co0.3Ti0.1O2 can also serve as potential cathode material for rechargeable Li-ion batteries.