Micro-nano biphasic conductive stress adaptive cathode for sodium ion batteries

Mechanical stress and strain induce intragranular disintegration and deactivation of the cathode material, which consequently impedes ion and electron transport leading to degraded capacity stability during prolonged cycling. Herein, a micro-nano biphasic conductive and stress-adaptive cathode (FeHCF-QD) composed of iron hexacyanoferrate (FeHCF) and carbon quantum dots (CQDs), was developed to address these issues. The distinctive, inside-out random distribution of CQDs in FeHCF-QD cubes not only can bridge the fractured electronic and ionic transfer channels but also significantly reduce the internal impedance, polarization and mechanical stress. Additionally, a pouch cell assembled with the FeHCF-QD and hard carbon (HC) demonstrates excellent rate performance (188.3 mA h at 3 C) and cycling stability (78.3% capacity retention after 800 cycles). These results indicate that enhancing the electronic conductivity and structural stability of Prussian blue analogs (PBAs) is crucial for their commercialization in sodium-ion batteries (SIBs).