Recent developments strategies in high entropy modified lithium-rich layered oxides cathode for lithium-ion batteries

Abstract

LiNi0.5Mn0.2Co0.2O2 (NMC532) is a widely used cathode material in commercial lithium-ion batteries; however, it suffers from capacity degradation and poor rate performance. In this study, sol-gel combustion synthesis (SCS) with a controlled fuel-to-oxidizer ratio (fuel stoichiometric (FS) and fuel-rich (FR) compositions, the fuel-lean (FL)) respectively, was employed to improve the structural and electrochemical performance of the NMC532 cathode. The fuel-to-oxidizer ratio was found to significantly impact the exothermicity of the combustion reaction, which subsequently influenced the morphology, crystal structure, and electrochemical performance of the synthesized NMC532 material. The FL composition produced a well-defined layered structure, the largest crystallite size, and the lowest degree of cation mixing compared to the FS and FR compositions. The FL cell exhibited an initial discharge capacity of 180 mAh/g and the highest capacity retention of 92.2% when cycled at 0.1 C within a voltage range of 2.5–4.4 V. Additionally, it demonstrated superior rate capability, delivering capacities of 180, 178, 175, and 173 mAh/g at current densities of 1 C, 3 C, 5 C, and 10 C, respectively, within a voltage range of 3.0–4.6 V. The electrochemical impedance spectroscopy (EIS) measurements confirmed that the FL cell had the lowest polarization and impedance. The superior electrochemical performance of the FL cathode was ascribed to its improved structural properties.