Enhancing the Reversibility and Kinetics of Heterovalent Ion‐Substituted Mn‐Based Prussian Blue Analogue Cathodes via Intervalence Charge Transfer
Lingtong Kong, Zhongxin Jing, Muhammad Mamoor, Yifan Jiang, Yanjun Zhai, Guangmeng Qu, Lu Wang, Bin Wang, Liqiang Xu
Abstract
Abstract Mn 3+ (d 4 ) in manganese‐based Prussian blue analogues (MnPBA) exhibits intrinsic orbital degeneracy upon sodiation/desodiation, resulting in severe Jahn–Teller distortion, which usually causes rapid capacity decay and sluggish kinetics. Unfortunately, traditional modification strategies are insufficient for electronic tuning of Mn 3+ to mitigate these issues. Herein, Intervalence Charge Transfer (IVCT) of manganese and iron to vanadium ions is unraveled in a series of novel V 3+ ‐substituted MnPBA to enhance electrochemical reaction reversibility and kinetics. IVCT drives electron distribution from localized to delocalized, achieves electronic coupling, and mitigates Jahn–Teller by transferring a single‐electron of Mn 3+ e g orbital. Notably, the reported Na 1.2 V 0.63 Mn 0.58 Fe(CN) 6 cathode demonstrates excellent rate capability (136.9 mAh g −1 at 20 mA g −1 and 94.9 mAh g −1 at 20 A g −1 ), remarkable long‐cycle stability (91.6 % capacity retention after 300 cycles at 20 mA g −1 and 90.7 % after 2000 cycles at 2 A g −1 ), and robust performance across a wide temperature range (98.59 % capacity after 300 cycles at −30 °C and 50 mA g −1 ), surpassing the majority of reported sodium‐ion cathodes. The intrinsic functioning mechanism of IVCT and quasi‐zero‐strain reaction mechanism were adequately understood through systematic in situ/ex situ characterizations. This study further develops electron‐tuning of PBA, opening a new avenue toward advanced sodium‐ion battery cathode materials.