Rational Design of Prussian Blue Analogues for Ultralong and Wide-Temperature-Range Sodium-Ion Batteries

Architecting Prussian blue analogue (PBA) cathodes with optimized synergistic bimetallic reaction centers is a paradigmatic strategy for devising high-energy sodium-ion batteries (SIBs); however, these cathodes usually suffer from fast capacity fading and sluggish reaction kinetics. To alleviate the above problems, herein, a series of early transition metal (ETM)-late transition metal (LTM)-based PBA (Fe-VO, Fe-TiO, Fe-ZrO, Co-VO, and Fe-Co-VO) cathode materials have been conveniently fabricated via an "acid-assisted synthesis" strategy. As a paradigm, the FeVO-PBA (FV) delivers a superb rate capability (148.9 and 56.1 mAh/g under 0.5 and 100 C, respectively), remarkable cycling stability over 30,000 cycles, high energy density (259.7 Wh/kg for the full cell), and a wide operation-temperature range (-60-80 °C). In situ/ex situ techniques and density functional theory calculations reveal the quasi-zero-strain and multielectron redox mechanisms of the FeVO-PBA cathode during cycling, supporting its higher specific capacity and stable cycling. It is considered that the d-d electron compensation effect between Fe and V enhanced the reversibility and kinetics of redox reactions and simultaneously improved the electronic conductivity and structural stability of the FeVO-PBA cathode. This work may pave a new way for the rational design of high-performance cathode materials with bimetallic reaction centers for SIBs.