The electrochemical performance of vanadium‐oxide‐based cathodes in aqueous zinc‐ion batteries (ZIBs) depends on their degree of crystallinity and composite state with carbon materials. An in situ ...electrochemical induction strategy was developed to fabricate a metal–organic‐framework‐derived composite of amorphous V2O5 and carbon materials (a‐V2O5@C) for the first time, where V2O5 is in an amorphous state and uniformly distributed in the carbon framework. The amorphous structure endows V2O5 with more isotropic Zn2+ diffusion routes and active sites, resulting in fast Zn2+ transport and high specific capacity. The porous carbon framework provides a continuous electron transport pathway and ion diffusion channels. As a result, the a‐V2O5@C composites display extraordinary electrochemical performance. This work will pave the way toward design of ZIB cathodes with superior rate performance.
In situ electrochemical induction of crystalline V2O3‐containing MIL‐88B(V) and carbon material yields a composite termed a‐V2O5@C. The a‐V2O5@C composites display appreciable electrochemical performance due to the unique amorphous structure of V2O5 and its composite state with carbon.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
Defect engineering is a strategy that is attracting widespread attention for the possibility of modifying battery active materials in order to improve the cycling stability of the ...electrodes. However, accurate investigation and quantification of the effect of the defects on the electrochemical energy storage performance of the cell are not trivial tasks. Herein, we report the quantification of vanadium-defective clusters (i.e., up to 5.7%) in the V
2
O
3
lattice via neutron and X-ray powder diffraction measurements, positron annihilation lifetime spectroscopy, and synchrotron-based X-ray analysis. When the vanadium-defective V
2
O
3
is employed as cathode active material in an aqueous Zn coin cell configuration, capacity retention of about 81% after 30,000 cycles at 5 A g
−1
is achieved. Density functional theory calculations indicate that the vanadium-defective clusters can provide favorable sites for reversible Zn-ion storage. Moreover, the vanadium-defective clusters allow the storage of Zn ions in V
2
O
3
, which reduces the electrostatic interaction between the host material and the multivalent ions.
Rechargeable aqueous zinc‐ion batteries (ZIBs) are promising energy‐storage devices owing to their low cost and high safety. However, their energy‐storage mechanisms are complex and not well ...established. Recent energy‐storage mechanisms of ZIBs usually depend on cationic redox processes. Anionic redox processes have not been observed owing to the limitations of cathodes and electrolytes. Herein, we describe highly reversible aqueous ZIBs based on layered VOPO4 cathodes and a water‐in‐salt electrolyte. Such batteries display reversible oxygen redox chemistry in a high‐voltage region. The oxygen redox process not only provides about 27 % additional capacity, but also increases the average operating voltage to around 1.56 V, thus increasing the energy density by approximately 36 %. Furthermore, the oxygen redox process promotes the reversible crystal‐structure evolution of VOPO4 during charge/discharge processes, thus resulting in enhanced rate capability and cycling performance.
Rezinking zinc batteries: Aqueous zinc‐ion batteries based on VOPO4 cathodes and a water‐in‐salt electrolyte displayed highly reversible oxygen redox chemistry at high voltages (see graph). The oxygen redox process not only led to increased capacity and a higher average operating voltage of the Zn/VOPO4 batteries, but also improved rate capability and cycling performance.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Current aqueous Zn batteries (ZBs) seriously suffer from dendrite issues caused by rough electrode surfaces. Despite significant efforts in prolonging lifespan of these batteries, little effort has ...been devoted to dendrite elimination in commercial‐grade cathode loading mass. Instead, demonstrations have only been done at the laboratory level (≤2 mg cm−2). Additionally, new dilemmas regarding change of the proton‐storage behavior and interface pulverization have emerged in turn. Herein, hydrogen‐substituted graphdiyne (HsGDY), with sub‐ångström level ion tunnels and robust chemical stability, is designed as an artificial interface layer to address these issues. This strategy prolongs the symmetric cell lifespan to >2400 h (100 days), which is 37 times larger than without protection (63 h). The simulation of dual fields reveals that HsGDY can redistribute the Zn2+ concentration field by spatially forcing Zn2+ to deviate from the irregular electric field. During practical use, the as‐assembled full batteries deliver a long lifespan 50 000 cycles and remain stable even at a commercial‐grade cathode loading mass of up to 22.95 mg cm−2. This HsGDY‐protection methodology represents great progress in Zn dendrite protection and demonstrates enormous potential in metal batteries.
Aqueous Zn‐based batteries suffering from the dendrite issue show a short lifespan, especially at commercial‐grade cathode loading mass. Hydrogen‐substituted graphdiyne with ion tunnels is employed to eliminate dendrites, based on ion redistribution, achieving a long lifespan of 10 000 cycles at a cathode loading mass of 22.95 mg cm−2. This work sheds light on tackling the dendrite issue encountered by metal batteries.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
A peroxidase catalyzes the oxidation of a substrate with a peroxide. The search for peroxidase-like and other enzyme-like nanomaterials (called nanozymes) mainly relies on trial-and-error ...strategies, due to the lack of predictive descriptors. To fill this gap, here we investigate the occupancy of
e
g
orbitals as a possible descriptor for the peroxidase-like activity of transition metal oxide (including perovskite oxide) nanozymes. Both experimental measurements and density functional theory calculations reveal a volcano relationship between the
e
g
occupancy and nanozymes’ activity, with the highest peroxidase-like activities corresponding to
e
g
occupancies of ~1.2. LaNiO
3-
δ
, optimized based on the
e
g
occupancy, exhibits an activity one to two orders of magnitude higher than that of other representative peroxidase-like nanozymes. This study shows that the
e
g
occupancy is a predictive descriptor to guide the design of peroxidase-like nanozymes; in addition, it provides detailed insight into the catalytic mechanism of peroxidase-like nanozymes.
The search for peroxidase-like as well as other enzyme-like nanozymes mainly relies on trial-and-error strategies, due to the lack of predictive descriptors. Here, the authors fill this gap by ...investigating the occupancy of e g orbitals as a possible descriptor for the peroxidase-like activity of transition metal oxide nanozymes
Transition metal nitrides are promising energy storage materials in regard to good metallic conductivity and high theoretical specific capacity, but their cycling stability is impeded by the huge ...volume change caused by the conversion reaction mechanism. Here, a simple strategy to produce an intercalation pseudocapacitive‐type vanadium nitride (VN) by one‐step ammonification of V2C MXene for sodium‐ion batteries is reported. Profiting from a distinctive layered structure pillared by Al atoms in the layer spacing, it delivers a high capacity of 372 mA h g−1 at 50 mA g−1 and a desirable rate performance. More importantly, it shows remarkably long cycling stability over 7500 cycles without capacity attenuation at 500 mA g−1. As expected, it is found that the intercalation pseudocapacitance plays an important role in the excellent performance, by using in situ X‐ray diffraction and ex situ X‐ray absorption structure characterization. Even more remarkable, are the high energy and power density of the sodium‐ion capacitor after coupling with a carbon‐based cathode. The hybrid device possesses an energy density of 78.43 Wh kg−1 at power density of 260 W kg−1. The results clearly show that such a unique‐layered VN with outstanding Na storage capability is an excellent new material for energy storage systems.
Layered vanadium nitride (VN) pillared by Al atoms is reported with outstanding Na+ storage performance and its intercalation pseudocapacitive mechanism is verified by ex situ XAS and in situ XRD measurements. The dynamics of sodium ions in this layered VN anode are analyzed to explain its pseudo‐capacitance contribution. Moreover, a sodium‐ion hybrid capacitor is constructed to demonstrate practical applications.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Prussian blue and its analogues (PBAs) have been proposed as promising cathode materials for sodium‐ion batteries (SIBs) due to high theoretical capacity and low cost, but they often suffer from poor ...electronic conductivity and structural instability. Herein, a stepwise hollow cubic framework structure is first designed and a hybridized hierarchical film synthesized from single‐crystal PBA nanoframes/carbon nanotubes (CNTs) composite is demonstrated as a binder‐free ultrahigh rate sodium ion cathode. This hierarchical configuration offers improved tolerance for lattice expansion, reduced sodium ion diffusion path, enhanced electronic conductivity, and optimized redox reactions, thereby achieving the excellent rate capability, high specific capacity, and long cycle life. As expected, the developed FeHCFe nanoframes/CNTs electrode film exhibits a super high rate capacity of 149.2 mAh g−1 at 0.1C and 35.0 mAh g−1 at 100C. Moreover, it displays an excellent cycling stability with about 92% capacity retention at 5C after 500 cycles. This work will pave a new way to engineer advanced electrode materials for ultrahigh rate SIBs.
A hierarchical film hybridized using as‐synthesized stepwise hollow Prussian blue cubes and carbon nanotubes is designed as a cathode material for ultrahigh rate sodium ion batteries. The film demonstrates improved tolerance for lattice expansion, reduced sodium ion diffusion path, enhanced electronic conductivity, and optimized redox reactions, thereby achieving the ultrahigh rate performance, superior capacity, and excellent cycling stability.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Molybdenum disulfide (MoS2) has attracted much attention as a promising alternative to Pt-based catalysts for highly efficient hydrogen generation. However, it suffers sluggish kinetics for driving ...the hydrogen evolution reaction (HER) process because of inert basal planes, especially in alkaline solution. Here, we show a combination of heteroatom doping and phase transformation strategies to engineer the in-plane structure of MoS2, that trigger their catalytic activities. Systematic characterizations are performed with advanced aberration-corrected microscopy and X-ray techniques, indicating that an as-designed MoS2 catalyst has a distorted zigzag-chain superlattice in metallic phase, while its in-plane structure was engineered via the incorporation of cobalt and oxygen species. The optimal Co, O dual-doped metallic phase molybdenum disulfide (1T-MoS2) electrocatalyst shows a significantly enhanced HER activity with a low overpotential of 113 mV at 10 mA cm–2 and corresponding small Tafel slope of 50 mV dec–1, accompanied by the robust stability in alkaline media. The calculated turnover frequency is higher than 6.65 H2 s–1 at an overpotential of 200 mV. More in-depth insights from the first-principle calculations illustrate that the water dissociation as a rate-determining step was largely accelerated by the in-plane Co–O–Mo species and fast electron transfer of the catalyst. Benefiting from ingenious design and fine identifications, this work provides a fundamental understanding of the relationships among heteroatom doping, phase transformation, and performance for MoS2-based catalysts.
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IJS, KILJ, NUK, PNG, UL, UM
Buffer reactions can prevent changes induced by external causes. Here, we demonstrate the significant buffer role of a very small amount of Mn in a self-optimized cathode for an aqueous Zn-ion ...battery. Our
operando
X-ray characterization studies reveal that the dissolution of most of the Mn in MnV
2
O
4
during the first charging cycle induces atomic re-arrangement to form a disordered vanadium oxide phase with 0.88 at% Mn. Interestingly, the residual Mn ions exhibit voluntary migration between tetrahedral and octahedral sites during Zn
2+
de/intercalation. This Mn migration not only stabilizes the main structure of the vanadium-based electrode, but also modulates the Fermi surface of V 3d against excessive drift. As result, the optimized cathode delivers an excellent capacity of 610.2 mA h g
−1
at 0.2 A g
−1
and long-term cycling stability over 4000 cycles. This buffer contribution
via
tunable metal ions exhibits high potential for applications in long-life metal-ion batteries and related fields.
A significant buffer effect from manganese ions is discovered to tune the atomic structure and valence state of an electrode material, resulting in a high-performance zinc battery.
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