Coupling Cation Disorder and Anion Redox to Mitigate Voltage Hysteresis in Layered Na‐Storage Cathodes
Shiyong Chu, Qi Wang, Shuqi Kang, Haibo Zhao, Sheng Xu, Cheng Chen, Liang Zhang, Shaohua Guo
Abstract
Abstract Anion‐activated cathodes can achieve high energy density through the redox reactions of both cations and anions. However, they suffer from significant voltage hysteresis due to unfavorable order‐to‐disorder structural transitions and severe anion redox polarization during (de)sodiation. Here, disrupting the ordered superstructures in the pristine cathodes is proposed to mitigate the detrimental order‐to‐disorder transition and the anion redox polarization. Despite the comparable ionic radii of Mg 2+ (0.72 Å) and Cu 2+ (0.73 Å), substituting Mg 2+ with Cu 2+ in ordered Na 0.67 Mn 0.74 Li 0.13 Mg 0.13 O 2 (MLM) disrupts the superstructure, observed in Na 0.67 Mn 0.74 Li 0.13 Cu 0.13 O 2 (MLCu13). Ordered MLM exhibits voltage hysteresis of 1.78 and 1.12 V during the first two cycles, attributed to the order‐to‐disorder transition and the formation of O 2 ‐like species. In contrast, MLCu13, benefiting from the disruption of the ordered superstructure, shows significantly reduced voltage hysteresis (1.04 and 0.52 V) by suppressing both the order‐to‐disorder transition and the formation of O 2 ‐like species. This approach enhances oxygen redox reversibility, elevates reduction voltages, and increases the average discharge voltage, demonstrating that constructing pre‐disordered configurations mitigates voltage hysteresis via stabilizing the framework and suppressing anion polarization. The findings demonstrate that constructing a pre‐disordered configuration serves as an effective approach to mitigate voltage hysteresis in layered anion‐activated cathodes for sodium‐ion batteries.