Controlled Crystallization of Carbon-blended Prussian Blue Analogs for Advanced Sodium-Ion Batteries

Prussian blue analogs (PBAs) are a potential choice for cathodes in sodium-ion batteries. However, their electrochemical performance is hindered by intrinsic structural vacancies and weak electronic conductivity, resulting in a reduced reversible capacity, multiplicative ability, and cycle stability. Herein, the carbon-blended Na2CoFe(CN)6 (COHCF@C) prepared by a controlled crystallization method displays improved electrochemical characteristics. With 70% residual capacity after 200 cycles, the reversible specific capacity of the COHCF@C is 123 mAh g–1 at 1 C. Furthermore, the COHCF@C also exhibits higher structural stability in aqueous electrolytes. Based on experimental results, this enhancement can be attributed to the introduction of carbon, slowing down the crystallization process and resulting in higher crystallinity. Additionally, the reduced water content leads to fewer defects, which improves the utilization of active sites. Overall, the finding provides an experimental basis and theoretical guidance for the application of PBA cells.