Mitigation of cation mixing of LiNiO2-based cathode materials by Li-doping for high-performing lithium-ion battery

Element doping of transition metal (TM) ions is commonly employed in the enhancement of structural and interfacial stability of layered nickel-rich cathode materials to construct high energy density lithium-ion batteries. However, one of the main factors for structural evolution and poor electrochemical stability of the layered nickel-rich cathode materials is the inherent Li+/Ni2+ disorder caused by dopants. To regulate the cation mixing, herein, the Li-doping is introduced into the TM slabs of the LiNiO2-based materials. Benefited from the charge compensation of the TM layers, the doped Li+ ions lead to the alleviation of the Li+/Ni2+ disorder generated during the synthesis stage and electrochemical charge/discharge cycles. It is demonstrated that proper amount of the doped Li+ ions would enhance the stability of the crystal lattice, improve the Li+ diffusion between electrode and electrolyte, and suppress the microcrack formation in the secondary grains of the materials. This is verified by the synergistic effect of Li/Mn co-doping, in particular, the LiNiO2-based layered material with 11 mol% Li and 1 mol% Mn exhibits great improvement in long-term cycling stability with capacity retention 71.11% after 200 cycles at 0.5C. The Li-doping strategy might provide a new perspective to the enhancement of structural stability of the layered nickel-rich materials for lithium-ion batteries in the future.