Search

Ni-rich layered oxides are the most promising cathode materials for high-energy-density Li-ion batteries. Full utilization of their potential resulting from high nickel content, mainly high capacity, is impaired due to the rapid performance degradation. Mitigating the main limitations of Ni-rich materials is possible through element doping. In this work, a series of LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode materials doped with sodium and/or neodymium was synthesized and systematically studied (XRD, SEM, TEM, STEM-EDX, XPS, galvanostatic charge/discharge tests, cyclic voltammetry). The strategies of single-element and dual-element doping were applied to study the effect of Na and Nd doping on the electrochemical performance of the modified NMC622 materials. The Na-doped NMC622 material exhibited improved capacity retention of 80.5% after 100 cycles, which is superior to the undoped one (62.7%), possibly owing to enlarged Li layer spacing and decreased Li ion migration activation energy. For the Nd-doped NMC622 cathode material, both the initial discharge capacity and capacity retention were much improved compared to the undoped NMC622. This can be related to the enhanced structural stability brought by the formation of strong bonds between neodymium and oxygen atoms. In contrast, the dual-doping of Na and Nd in NMC622 material resulted in much poorer electrochemical and cycling performance, but the reason for this is unclear. The experimental data suggest that the combination of Na and Nd dopants caused the deterioration of crystal structure, possibly due to the introduced impurities. This consequently affected the structural stability of the dual-doped material, leading to the lowest discharge capacity and capacity retention among the studied NMC622 materials.

The growing demand for efficient lithium-ion batteries to power vehicles and energy storage entails improving cathode material properties. Maintaining the stability of Ni-rich layered structure oxide cathodes is critical for long-term Li-ion battery operation. In this work, a series of LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode materials doped with selected rare earth metal ions (La, Nd, Eu) of various concentrations (0.5-1.5 mol%) was synthesized and systematically studied (XRD, XPS, TEM, STEM-EDX, galvanostatic charge/discharge tests, cyclic voltammetry). The main goal of the research was to suppress the mixing of Ni/Li cations, which influences the electrochemical performance of LiNi0.6Mn0.2Co0.2O2 cathode materials by introducing rare earth elements using co-precipitation. The results showed that the La, Nd, Eu-doped materials exhibit significantly improved electrochemical properties, such as capacity, rate performance, capacity retention and Li+diffusivity compared to the pristine material. A clear dependence of the doped Ni-rich cathode material capacity on the degree of Ni/Li cation mixing was determined. The presence of a dopant (La, Nd or Eu) with a large radius, the tendency to form strong bonds with oxygen, and electrochemically inactive reduces Ni/Li disordering. It stabilizes the cathode structure, ensuring its better performance. The optimal content of La, Nd and Eu is 1.0, 0.5, and 0.5 mol%, respectively.