Rational Design of Cobalt-Based Prussian Blue Analogues via 3d Transition Metals Incorporation for Superior Na-Ion Storage

Abstract

Understanding the relationship between structure regulation and electrochemical performance is key to developing efficient and sustainable sodium-ion batteries (SIBs) materials. Herein, seven Cobalt-M-based (M=V, Mn, Fe, Co, Ni, Cu, Zn) Prussian blue analogues (CoM-PBAs) are designed as anodes for SIBs via a universal low-energy co-precipitation approach with the strategic inclusion of 3d transition metals. Density Functional Theory (DFT) simulation and experimental validation reveal that a moderate p-band center of cyanide linkages (-CN-) is more favorable for Na+ intercalation and diffusion, while the d-band center of metal cations is linearly related to electrode stability. Among seven CoM-based PBAs, CoV-PBAs possess the best sodium-ion adsorption/diffusion kinetics and overall cycling performance, including high specific capacity (565 mAh/g at 0.1 A/g), cycling stability (over 15000 cycles with 97.7% capacity retention), and superior rate capability (174.7 mAh/g at 30 A/g). In-situ/ex-situ techniques further demonstrate that the π-electron regulation by V introduction enhances the reversibility and kinetics of redox reactions. Moreover, the study identified the "p-band center" and "d-band center" may serve as key descriptors for quantifying the capability and stability of other-type bimetal Co-based anodes (oxides, phosphides, sulfides, and selenides) with similar theoretical capacity, offering a potentially transformative approach for selecting practical SIB electrode materials.