Structure Engineering on Prussian Blue Analog Anode Toward Rapid Na‐Ion Storage

Abstract Developing high‐rate electrode materials is a critical enabler of fast‐charging Na‐ion battery (NIB). Prussian blue analog (PBA) with rapid charge transfer channels has shown significant potential as high‐rate NIB cathodes; however, the fast‐charging capability of reported PBA‐based anodes remains limited. This challenge primarily stems from the complete transformation of their original PBA‐based crystal structures during synthesis processes, resulting in loss of the inherent rapid charge transfer channels. Herein, a Ni‐Fe based PBA (Ni 3 [Fe(CN) 6 ] 2 ) with a representative PBA‐based crystal structure is presented as a prototype to investigate its potential as a NIB anode, and structural modification strategies are implemented to unlock its rapid Na‐ion storage. First, conversion reaction mechanism is demonstrated in the Ni 3 [Fe(CN) 6 ] 2 during sodiation, with a theoretical specific capacity of 357.2 mAh g −1 . However, its reversible capacities after long‐term cycling and at high rates are low. To address these issues, structural optimization strategies including S incorporation, configurational entropy modulation, and coordination environment regulation are utilized. Consequently, its fast‐charging (≈40 s per charge with 245.0 mAh g −1 input) and excellent cycling capabilities are realized. This study demonstrates the feasibility of PBA as high‐rate NIB anodes, and promotes the further investigation into structural optimization strategies aimed at developing other fast‐charging electrodes.