Effect of Mg/Al doping at the Co site on the structural and electrochemical performance of LiCoO2 cathode materials

Abstract

LiCoO₂, which is one of the earliest commercially available cathode materials for lithium-ion batteries, continues to attract significant research interest owing to its favorable electrochemical properties. However, its practical application is hindered by challenges such as the low Li⁺ diffusion rate and structural instability during charge–discharge cycles. Al and Mg are the most common dopants used with transition metal-based layered oxides of cathode materials. In this work, Mg/Al was selected for Co site doping, and the influence of doping on the structural stability and electrochemical performance were investigated, with a special focus on lithium ion diffusion behavior. This study was based on the density functional theory and integrated electronic structure (DOS), bond length, migration energy barriers, diffusion coefficients and operating voltage into a unified framework, revealing the synergistic effects of Al/Mg doping. The findings revealed that both Mg and Al doping effectively enhanced the conductivity of LiCoO₂. The calculated migration energy barriers of lithium ions along the b axis were reduced to 0.40 eV and 0.42 eV in the Mg- and Al-doped systems, respectively. This simultaneously increased the diffusion rate of Li⁺ and the operating voltage.