Attaining both low-cost, minimum environmental footprint, and high safety is important to facilitate the use of these systems on a larger scale. Harnessing electricity generated by renewable sources requires the development of versatile and robust energy storage systems (ESSs). (1) Storage of electricity produced via renewable energies is a critical link toward greener energy production and distribution worldwide. The use of renewable energies is imperative to lower the greenhouse gas emissions and progressively develop a society free of fossil fuel dependence. Our work clarifies several intriguing structural and redox-mediated aging mechanisms in the CuHCF cathode and pinpoints parameters that correlate with the performance, which will hold importance for the development of future Prussian blue analogue-type cathodes for aqueous rechargeable ZIBs. We also find that SO 4 2– anions reversibly insert into CuHCF during charge. This explains the progressive increase in the voltage of the charge/discharge plateaus upon repeated cycling. By tracking the K-edge fluorescence using operando XAS coupled with cyclic voltammetry, we successfully link the aging effect to the activation of the Fe 3+/Fe 2+ redox couple as a consequence of Cu dissolution. This is distinct from the charge compensation process where both the Cu 2+/Cu + and Fe 3+/Fe 2+ redox couples participate throughout the bulk.

This triggers Zn 2+ ions to enter newly formed Cu vacancies, in addition to native Fe vacancies already present in the bulk, which causes a reduction of nearby metal sites. We further conclude that Cu is the unstable species during aging, whose dissolution is significant at the surface of the CuHCF particles. Our data suggest that these peaks are unrelated to hypothetical Zn xCu 1– xHCF phases or to oxidic phases, but are caused by partial intercalation of ZnSO 4 into graphitic carbon. First, we identify a set of previously debated X-ray diffraction peaks appearing at early stages of cycling (below 200 cycles) in CuHCF. By combining high-angle annular dark-field-scanning electron transmission microscopy, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy, and elemental analysis, we reconstruct the picture of both the bulk and the surface. This allows us to distinguish between structure-related aging effects and charge compensation processes associated with electroactive metal centers upon Zn 2+ ion insertion/deinsertion. Here, we present an in-depth study of the CuHCF cathode by employing various X-ray spectroscopic techniques. However, both the Zn anode and the CuHCF cathode show unavoidable signs of aging during cycling, though the underlying mechanisms have remained somewhat ambiguous.

The zinc/copper hexacyanoferrate (Zn/CuHCF) cell has gained attention as an aqueous rechargeable zinc-ion battery (ZIB) owing to its open framework, excellent rate capability, and high safety.

Xps peak components fill