Suppressing Ni/Li disordering in LiNi0.6Mn0.2Co0.2O2 cathode material for Li-ion batteries by rare earth element doping
Magdalena Zybert, Hubert Ronduda, Karolina Dąbrowska, Andrzej Ostrowski, Kamil Sobczak, Dariusz Moszyński, Bartosz Hamankiewicz, Zbigniew Rogulski, Wioletta Raróg‐Pilecka, W. Wieczorek
Abstract
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.