Effect of copper and iron substitution on the structures and electrochemical properties of LiNi0.8Co0.15Al0.05O2 cathode materials

Abstract

Abstract Cu and Fe are the main impurity elements in the hydrometallurgical regeneration of spent lithium‐ion batteries. Hence, it is important to study the effect of Cu and Fe doping on the structures and electrochemical properties of cathode materials. In this study, a series of Cu‐ and/or Fe‐doped LiNi0.8Co0.15Al0.05O2 cathode materials are synthesized by spray pyrolysis and high‐temperature solid‐state method. The inductively coupled plasma (ICP), X‐ray diffraction (XRD), and Rietveld refinement results reveal that Cu and Fe can incorporate into the crystal lattice and cation mixing is suppressed. The X‐ray photoelectron spectroscope (XPS) results show that the relative ratio of Ni2+/Ni3+ on the surface is effectively decreased. Electrochemical results display that the electrochemical performances of Cu‐ and/or Fe‐doped samples are improved when the atomic ratio of Ni to Cu and Ni to Fe is greater than 79.0 and 399.0, respectively. The dQ/dV, GITT, EIS, XRD, and XPS studies indicate that the structure stability, Li+ diffusion coefficient, and charge transfer can be increased by appropriate Cu and/or Fe substitution. The results suggest that appropriate Cu and Fe can be doped into LiNi0.8Co0.15Al0.05O2 as beneficial elements rather than removed as impurities.

Keywords

• Cu and Fe substitution
• hydrometallurgical recovery
• LiNi0.8Co0.15Al0.05O2
• lithium‐ion battery