Towards ultra-wide voltage window (3.2 V) aqueous symmetric supercapacitors triggered by hybridizing FeNiCo oxides with Ni(pyrithione)2 on FeNi foam

Abstract

The low decomposition voltage (~1.23 V) of water enormously restricts the workable voltage of aqueous symmetrical supercapacitors (SSCs), which correspondingly limits the energy densities and frustrates the commercialization of aqueous SSCs. Herein, the voltage window of an all-solid-state symmetrical supercapacitors (ASSC) can be extended via employing a novel self-supporting hybrid electrode constructed by coupling FeNiCo oxides with Ni(pyrithione)2 on FeNi foam (denoted as NiPT@FeNiCo oxides/FNF) as both cathode and anode, which was synthesized using two-step hydrothermal processes. Primarily due to the introduction of redox-active pyrithione ligand chelating Ni ions supplemented by multiple pairs of reversible redox reactions to suppress water splitting, the assembled ASSC device exhibits an extra-wide workable voltage window up to 3.2 V with ultrahigh energy exporting densities (69.9 Wh kg−1 at 173.9 W kg−1, and 29.1 Wh kg−1 even at an elevated 2437.6 W kg−1). The energy density feature of this assembled ASSC device is superior to most existing transition metal oxide-based supercapacitors and even asymmetric or hybrid devices heretofore reported. After 10,000 cycles, this assembled ASSC device records a 92.5 % retention of initial area specific capacity. Our work offers a robust combination strategy to design high-potential electrode materials for constructing high-voltage ASSCs.