Manganese‐Based Prussian Blue Analogs Synthesized by Two‐Step Precipitation as Cathode Materials for Magnesium‐Ion Batteries

Prussian blue analogs (PBAs) are promising cathode candidates for magnesium‐ion batteries (MIBs), but manganese‐based PBA (MnHCF) suffers from severe Jahn–Teller distortion and sluggish Mg 2+ diffusion kinetics caused by the high charge density of divalent Mg 2+ . Herein, Co‐doped MnHCF (CoMnHCF) with a well‐defined hollow square structure is fabricated via a citrate‐assisted two‐step precipitation method, which achieves simultaneous crystal phase regulation, morphology optimization and coordination environment tuning specifically for Mg 2+ storage. The microstructure, morphology and Mg‐storage performance are systematically characterized by XRD, FTIR, SEM/EDS, CV, GCD, EIS and ex situ XRD. Results demonstrate that Co doping transforms MnHCF from a monoclinic block/bar‐like structure to a cubic/tetragonal hollow square architecture with enhanced crystallinity andmodulated cyanide coordination environment. CoMnHCF exhibits significantly enhanced electrochemical performance: 86.14% capacity retention after 200 cycles at 50 mA g −1 , 72.78% after 1000 cycles at 500 mA g −1 , and only 71.7% increase in charge‐transfer resistance after 1000 cycles. This improvement arises from reduced phase transitions, enhanced ion transport kinetics and lower migration energy barriers. This study confirms Co doping is an effective strategy for MnHCF modification, providing an excellent cathode candidate for MIBs and new insights for Prussian blue analog structural engineering.