Enhancing the Reversibility and Kinetics of Heterovalent Ion‐Substituted Mn‐Based Prussian Blue Analogue Cathodes via Intervalence Charge Transfer

Mn3+ (d4) in manganese‐based Prussian blue analogues (MnPBA) exhibits intrinsic orbital degeneracy upon sodiation/desodiation, resulting in severe Jahn‐Teller distortion, which causes rapid capacity decay and sluggish kinetics. Unfortunately, traditional modification strategies are deficient for electronic tuning of Mn3+ to address these issues. Herein, Intervalence Charge Transfer (IVCT) of manganese and iron to vanadium ions is unraveled in a series of novel V3+‐substituted MnPBA to enhance electrochemical reaction reversibility and kinetics. Precisely, IVCT drives electron distribution from localized to delocalized, achieves electronic coupling and mitigates Jahn‐Teller by transferring a single‐electron of Mn3+ eg orbital. Notably, the reported Na1.2V0.63Mn0.58Fe(CN)6 cathode demonstrates incredible 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 mechanisms of IVCT and quasi‐zero‐strain reaction mechanisms 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.