Abstract:The reversible electrochemical insertion of zinc into host materials has been shown to be very promising for large‐scale energy storage applications. In particular, copper hexacyanoferrate (CuHCF) and its derivatives from the Prussian Blue family enable a fast and reversible (de‐)insertion of zinc ions when operated in a zinc‐based aqueous electrolyte. In this work, the effect of the concentration of a zinc sulfate‐containing aqueous neutral solution on the aging of CuHCF and copper‐zinc hexacyanoferrate mixtu… Show more
“…Therefore, the rate performance demonstrates that a 50-fold increase in current rate only results in a 6.4% total capacity loss, which is an outstanding advantage over other electrode materials in Fig. 4 b and Table S4 [ 46 – 48 , 50 – 54 ]. Furthermore, the long-span cycling performance at a high current rate of 30 C is shown in Figs.…”
Section: Resultsmentioning
confidence: 90%
“…And the cycling performance is far superior to other PBAs as displayed in Fig. 3 d [ 46 – 48 ]. Fig.…”
Aqueous ammonium ion batteries are regarded as eco-friendly and sustainable energy storage systems. And applicable host for NH4+ in aqueous solution is always in the process of development. On the basis of density functional theory calculations, the excellent performance of NH4+ insertion in Prussian blue analogues (PBAs) is proposed, especially for copper hexacyanoferrate (CuHCF). In this work, we prove the outstanding cycling and rate performance of CuHCF via electrochemical analyses, delivering no capacity fading during ultra-long cycles of 3000 times and high capacity retention of 93.6% at 50 C. One of main contributions to superior performance from highly reversible redox reaction and structural change is verified during the ammoniation/de-ammoniation progresses. More importantly, we propose the NH4+ diffusion mechanism in CuHCF based on continuous formation and fracture of hydrogen bonds from a joint theoretical and experimental study, which is another essential reason for rapid charge transfer and superior NH4+ storage. Lastly, a full cell by coupling CuHCF cathode and polyaniline anode is constructed to explore the practical application of CuHCF. In brief, the outstanding aqueous NH4+ storage in cubic PBAs creates a blueprint for fast and sustainable energy storage.
“…Therefore, the rate performance demonstrates that a 50-fold increase in current rate only results in a 6.4% total capacity loss, which is an outstanding advantage over other electrode materials in Fig. 4 b and Table S4 [ 46 – 48 , 50 – 54 ]. Furthermore, the long-span cycling performance at a high current rate of 30 C is shown in Figs.…”
Section: Resultsmentioning
confidence: 90%
“…And the cycling performance is far superior to other PBAs as displayed in Fig. 3 d [ 46 – 48 ]. Fig.…”
Aqueous ammonium ion batteries are regarded as eco-friendly and sustainable energy storage systems. And applicable host for NH4+ in aqueous solution is always in the process of development. On the basis of density functional theory calculations, the excellent performance of NH4+ insertion in Prussian blue analogues (PBAs) is proposed, especially for copper hexacyanoferrate (CuHCF). In this work, we prove the outstanding cycling and rate performance of CuHCF via electrochemical analyses, delivering no capacity fading during ultra-long cycles of 3000 times and high capacity retention of 93.6% at 50 C. One of main contributions to superior performance from highly reversible redox reaction and structural change is verified during the ammoniation/de-ammoniation progresses. More importantly, we propose the NH4+ diffusion mechanism in CuHCF based on continuous formation and fracture of hydrogen bonds from a joint theoretical and experimental study, which is another essential reason for rapid charge transfer and superior NH4+ storage. Lastly, a full cell by coupling CuHCF cathode and polyaniline anode is constructed to explore the practical application of CuHCF. In brief, the outstanding aqueous NH4+ storage in cubic PBAs creates a blueprint for fast and sustainable energy storage.
“…The development of aqueous PBA-based ZIBs is still at its infant stage, and despite considerable advances in the recent past, there are various processes related to aging and capacity fade that are still not well-understood. 28 − 32 This is what motivates this study.…”
Section: Introductionmentioning
confidence: 90%
“…Furthermore, Zn 2+ ions have been reported to become irreversibly trapped in CuHCF, which is proposed to trigger phase segregation and formation of new nonstoichiometric Zn-rich phases (Zn x Cu 1– x CuHCF). 28 , 29 , 32 , 33 These phases are thought to be responsible for new X-ray diffraction (XRD) peaks that appear with cycling, although some of the peaks have not yet been conclusively identified. 28 , 30 , 34 The Zn 2+ trapping and formation of new Zn-rich phases have been proposed to be responsible for shifting the Zn + ion insertion (or the charge/discharge voltage plateaus) to higher potentials.…”
Section: Introductionmentioning
confidence: 99%
“… 28 , 29 , 32 , 33 These phases are thought to be responsible for new X-ray diffraction (XRD) peaks that appear with cycling, although some of the peaks have not yet been conclusively identified. 28 , 30 , 34 The Zn 2+ trapping and formation of new Zn-rich phases have been proposed to be responsible for shifting the Zn + ion insertion (or the charge/discharge voltage plateaus) to higher potentials. 29 , 32 Nevertheless, uncertainties still remain around both the mechanism of Cu dissolution and the origin of these new diffraction peaks, especially at early stages of cycling.…”
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. However, both
the Zn anode and the CuHCF cathode show unavoidable signs of aging
during cycling, though the underlying mechanisms have remained somewhat
ambiguous. Here, we present an in-depth study of the CuHCF cathode
by employing various X-ray spectroscopic techniques. 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. 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. First, we identify a set of previously debated X-ray
diffraction peaks appearing at early stages of cycling (below 200
cycles) in CuHCF. Our data suggest that these peaks are unrelated
to hypothetical Zn
x
Cu
1–
x
HCF phases or to oxidic phases, but are caused by
partial intercalation of ZnSO
4
into graphitic carbon. We
further conclude that Cu is the unstable species during aging, whose
dissolution is significant at the surface of the CuHCF particles.
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. 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. 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 explains the progressive
increase in the voltage of the charge/discharge plateaus upon repeated
cycling. We also find that SO
4
2–
anions
reversibly insert into CuHCF during charge. 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.
Quasi‐neutral aqueous zinc‐ion (Zn‐ion) batteries are nowadays among the most promising energy storage devices for smart‐grid applications. However, their practical use remains hindered by the low Zn electrodeposition efficiency at the negative electrode, which is especially reduced due to the parasitic evolution of gaseous hydrogen. Indium is a non‐toxic metal showing poor hydrogen evolution kinetics, but it is also very expensive. Therefore, an optimized mixture of bismuth and indium particles has been used as the substrate for the Zn electrodeposition and dissolution reaction to increase its reversibility and its efficiency in a quasi‐neutral ZnSO4 solution. This strategy not only allowed to prolong the cycle life of a full Zn‐ion cell of 10 times at 0.5 C due to the suppression of the hydrogen evolution reaction, as proved by the operando DEMS analysis, but also led to very homogeneous zinc deposits over prolonged cycling at realistic charge and current densities.
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