Practical Evaluation of Anionic Redox in Li‐rich Cathode: An Electrochemical Study

Abstract Lithium‐rich (Li‐rich) manganese‐based layered oxide materials are promising candidates for positive electrode materials due to their high energy density. However, challenges such as transition metal cation migration and irreversible anionic redox hinder their application. This study employs various electrochemical methods to systematically investigate three types of cathode materials: LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NCM622), Li 1.12 Ni 0.39 Mn 0.49 O 2 (Li1.12), and Li 1.2 Ni 0.2 Mn 0.6 O 2 (Li1.2). The findings indicate that an increase in lithium content leads to higher participation of anions in Anion Redox Reactions (ARRs), resulting in an augmented capacity. However, this also brings about significant polarization. The activation process of Li‐rich materials triggers the ARRs mechanism, resulting in a sharp increase in resistance. Voltage drops during shelving and cycling are closely tied to the ARRs occurring at high potentials in Li‐rich materials. To make the best use of the additional capacity associated with ARRs, it is essential to adjust the formation/cycling voltage in accordance with the characteristics of positive electrode materials with varying lithium contents. This study offers valuable insights for the design and utilization of Li‐rich materials.