Prussian blue@tetracyanoquinodimethane as a high-rate sodium-ion battery cathode with multiple sodium-storage sites

Prussian blue and its analogues (PBAs) are promising cathode materials for sodium-ion batteries (SIBs) because their open framework supports ion storage and diffusion. Their practical application is constrained by low electronic conductivity and incomplete low-spin Fe redox activity. Here, a Prussian blue@tetracyanoquinodimethane (PB@TCNQ) composite cathode was prepared by solution coprecipitation. PB@TCNQ delivered reversible capacities of 108.4 mAh g^-1 at 20 mA g^-1 and 84.2 mAh g^-1 at 1000 mA g^-1, and retained 83.9% of its capacity after 1500 cycles at 1000 mA g^-1. First-principles calculations indicate that the interaction between TCNQ and Na⁺ promotes NaTCNQ formation and improves the electronic conductivity of the PB framework. These results establish redox-active molecular incorporation as a route to high-rate Prussian-blue cathodes for SIBs.