Polyaniline-coated prussian blue analog cathodes for high-performance aqueous zinc-ion batteries

Prussian Blue analogues (PBAs) are attractive cathode candidates for aqueous zinc-ion batteries (AZIBs) owing to their open framework and low cost, yet their application is hindered by poor electrical conductivity and limited structural stability. To address these issues, we synthesized a series of CuHCF@PANI-X composites (X = 10, 15, 30, 45) via in-situ oxidative polymerization, in which conductive polyaniline (PANI) was uniformly coated on the surface of copper hexacyanoferrate (CuHCF) particles. Morphological and structural analyses confirmed the formation of a dense and continuous core-shell architecture. BET results further revealed that PANI coating modified the pore architecture, reducing the accessible surface area while enlarging the mesopore diameter from ~2-3 nm to 15-20 nm, thereby facilitating Zn²⁺ transport. Electrochemical tests demonstrated that the optimized CuHCF@PANI-45 electrode delivered an initial capacity of 54.6 mAh·g -1 at 100 mA·g -1 and preserved 16.9 mAh·g -1 after 500 cycles, compared with only 2.1 mAh·g -1 for pristine CuHCF. Importantly, after 500 cycles, CuHCF@PANI-45 maintained 31% of its initial capacity, whereas pristine CuHCF retained only 6.6%, confirming its superior long-term durability. Moreover, the PANI layer promoted more reversible Fe³⁺/Fe²⁺ and Cu²⁺/Cu⁺ redox processes, thereby stabilizing the electrode structure during long-term cycling. These findings highlight that tuning the PANI coating content not only enhances conductivity and structural robustness but also optimizes the pore environment, offering an effective strategy for optimizing and practically applying PBA-based cathodes in aqueous zinc-ion batteries. • CuHCF@PANI core–shell cathodes were synthesized via in-situ polymerization. • PANI coating enhances conductivity, structural stability, and Zn 2+ transport. • CuHCF@PANI-45 delivers high capacity and long-term cycling stability in AZIBs.