Prussian blue analogue-based superstructure nanoarrays for sodium ion hybrid supercapacitors

Supercapacitors (SCs) have attracted significant attention due to their remarkable traits of high-power density and prolonged cyclability. Despite the extensive exploration of Prussian blue analogues (PBAs) with three-dimensional (3D) open frameworks as SC electrodes, their instability and low conductivity have impeded their advancement in practical SC applications. In this study, we present a straightforward immersion-based technique to produce a superstructure nanoarray of CoNiFe-based PBA (CoNiFePBA). The unique superstructure comprises ultrathin nanosheets assembled into a half-open hollow configuration, fostering abundant active surface sites, a stable framework, and efficient channels for ion/electron transfer, consequently enabling effective charge storage. Furthermore, the integration of ternary metals not only offers numerous redox reaction centers but also heightens synergistic effects, resulting in enhanced capacity and cycling stability. As a result, the CoNiFePBA electrode delivers outstanding specific capacity (96.85 mAh g⁻¹ at 0.5 A g⁻¹) and enduring cycling stability (92.25 % after 10,000 cycles). Notably, the hybrid SC built on the CoNiFePBA demonstrates an exceptionally broad voltage window (2.1 V) and a high energy density. This work underscores the immense potential of CoNiFePBA superstructure nanoarrays for driving high-performance SC technology forward.