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

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.