Facile and Scalable Synthesis of 3D Structures of V10O24·12H2O Nanosheets Coated with Carbon toward Ultrafast and Ultrastable Zinc Storage

Ethylene Glycol-Choline Chloride Based Hydrated Deep Eutectic Electrolytes Enabled High-Performance Zinc-Ion Battery

Aqueous rechargeable zinc-ion batteries (ARZIBs) are considered as an emerging energy storage technology owing to their low cost, inherent safety, and reasonable energy density. However, significant challenges associated with electrodes, and aqueous electrolytes restrict their rapid development. Herein, ethylene glycol-choline chloride (Eg-ChCl) based hydrated deep-eutectic electrolytes (HDEEs) are proposed for RZIBs. Also, a novel V10O24·nH2O@rGO composite is prepared and investigated in combination with HDEEs. The formulated HDEEs, particularly the composition of 1 ml of EG, 0.5 g of ChCl, 4 ml of H2O, and 2 M ZnTFS (1-0.5-4-2 HDEE), not only exhibit the lowest viscosity, highest Zn2+ conductivity (20.38 mS cm-1), and the highest zinc (Zn) transference number (t+ = 0.937), but also provide a wide electrochemical stability window (>3.2 V vs ZnǁZn2+) and enabledendrite-free Zn stripping/plating cycling over 1000 hours. The resulting ZnǁV10O24·nH2O@rGO cell with 1-0.5-4-2 HDEE manifests high reversible capacity of ≈365 mAh g-1 at 0.1 A g-1, high rate-performance (delivered ≈365/223 mAh g-1 at 0.1/10 mA g-1) and enhanced cycling performance (≈63.10% capacity retention in the 4000th cycle at 10 A g-1). Furthermore, 1-0.5-4-2 HDEE support feasible Zn-ion storage performance across a wide temperature range (0-80 °C) FInally, a ZnǁV10O24·nH2O@rGO pouch-cell prototype fabricated with 1-0.5-4-2 HDEE demonstrates good flexibility, safety, and durability.

Facile synthesis of Bi2Se3/nitrogen-doped carbon dot nanoplates for aqueous zinc ion battery cathodes

Bi2Se3 is a promising cathode material for aqueous zinc ion batteries (AZIBs), but its limited capacity and poor cycling stability deter its further use in the development of AZIBs. To solve this issue, Bi2Se3/NCD composites have been synthesized via a simple two-step solvothermal method. The introduction of nitrogen-doped carbon dots (NCDs) provides more active sites and makes the composite surface rich in functional groups, which facilitates contact with aqueous electrolytes. The results showed that Bi2Se3/NCDs improved the zinc storage properties of Bi2Se3 as a cathode material. The discharge specific capacity is 318 mA h g-1 at 0.1 A g-1. The cycling performance of Bi2Se3/NCDs was also relatively excellent compared to that of Bi2Se3. This work offers a productive and feasible strategy for metal chalcogenides (MCs) as cathode materials for AZIBs to improve the zinc storage capacity.

How About Vanadium-Based Compounds as Cathode Materials for Aqueous Zinc Ion Batteries?

Aqueous zinc-ion batteries (AZIBs) stand out among many monovalent/multivalent metal-ion batteries as promising new energy storage devices because of their good safety, low cost, and environmental friendliness. Nevertheless, there are still many great challenges to exploring new-type cathode materials that are suitable for Zn2+ intercalation. Vanadium-based compounds with various structures, large layer spacing, and different oxidation states are considered suitable cathode candidates for AZIBs. Herein, the research advances in vanadium-based compounds in recent years are systematically reviewed. The preparation methods, crystal structures, electrochemical performances, and energy storage mechanisms of vanadium-based compounds (e.g., vanadium phosphates, vanadium oxides, vanadates, vanadium sulfides, and vanadium nitrides) are mainly introduced. Finally, the limitations and development prospects of vanadium-based compounds are pointed out. Vanadium-based compounds as cathode materials for AZIBs are hoped to flourish in the coming years and attract more and more researchers' attention.

Aging-Responsive Phase Transition of VOOH to V10O24·nH2O vs Zn2+ Storage Performance as a Rechargeable Aqueous Zn-Ion Battery Cathode

Vanadium oxyhydroxide has been recently investigated as a starting material to synthesize different phases of vanadium oxides by electrochemical or thermal conversion and has been used as an aqueous zinc-ion battery (AZIB) cathode. However, the low-valent vanadium oxides have poor phase stability under ambient conditions. So far, there is no study on understanding the phase evolution of such low-valent vanadium oxides and their effect on the electrochemical performance toward hosting the Zn²⁺ ions. The primary goal of the work is to develop a high-performance AZIB cathode, and the highlight of the current work is the insight into the auto-oxidation-induced phase transition of VOOH to V₁₀O₂₄·nH₂O under ambient conditions and Zn²⁺ intercalation behavior thereon as an aqueous zinc-ion battery cathode. Herein, we demonstrate that hydrothermally synthesized VOOH undergoes a phase transition to V₁₀O₂₄·nH₂O during both the electrochemical cycling and aerial aging over 38-45 days. However, continued aging till 150 days at room temperature in an open atmosphere exhibited an increased interlayer water content in the V₁₀O₂₄·nH₂O, which was associated with a morphological change with different surface area/porosity characteristics and notably reduced charge transfer/diffusion resistance as an aqueous zinc-ion battery cathode. Although the fresh VOOH cathode had impressive specific capacity at rate performance, (326 mAh/g capacity at 0.1 A/g current and 104 mAh/g capacity at 4 A/g current) the cathode suffered from a continuous capacity decay. Interestingly, the aged VOOH electrodes showed gradually decreasing specific capacity with aging at low current and however followed the reverse order at high current. At a comparable specific power of ∼64-66 W/kg, the fresh VOOH and aged VOOH after 60, 120, and 150 days of aging showed the respective energy densities of 208.3, 281.2, 269.2, and 240.6 Wh/kg. Among all the VOOH materials, the 150 day-aged VOOH cathode exhibited the highest energy density at a power density beyond 1000 W/kg. Thanks to the improved kinetics, the 150 day-aged VOOH cathode delivered a considerable energy density of 39.7 Wh/kg with a high specific power of 4466 W/kg. Also, it showed excellent cycling performance with only 0.002% capacity loss per cycle over 20 300 cycles at 10 A/g.

Vanadium Oxide-Poly(3,4-ethylenedioxythiophene) Nanocomposite as High-Performance Cathode for Aqueous Zn-Ion Batteries: The Structural and Electrochemical Characterization

In this work the nanocomposite of vanadium oxide with conducting polymer poly(3,4-ethylenedioxythiophene) (VO@PEDOT) was obtained by microwave-assisted hydrothermal synthesis. The detailed study of its structural and electrochemical properties as cathode of aqueous zinc-ion battery was performed by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The initial VO@PEDOT composite has layered nanosheets structure with thickness of about 30-80 nm, which are assembled into wavy agglomerated thicker layers of up to 0.3-0.6 μm. The phase composition of the samples was determined by XRD analysis which confirmed lamellar structure of vanadium oxide V₁₀O₂₄∙12H₂O with interlayer distance of about 13.6 Å. The VO@PEDOT composite demonstrates excellent electrochemical performance, reaching specific capacities of up to 390 mA∙h∙g^-1 at 0.3 A∙g^-1. Moreover, the electrodes retain specific capacity of 100 mA∙h∙g^-1 at a high current density of 20 A∙g^-1. The phase transformations of VO@PEDOT electrodes during the cycling were studied at different degrees of charge/discharge by using ex situ XRD measurements. The results of ex situ XRD allow us to conclude that the reversible zinc ion intercalation occurs in stable zinc pyrovanadate structures formed during discharge.

Multiscale modulation of vanadium oxides via one-step facile reduction to synergistically boost zinc-ion battery performance

Accordion-like V10O24·12H2O was prepared via one-step reduction of commercial V2O5. Benefiting from the interlayer spacing, mixed valence, and superstructure, a superior performance was obtained for V10O24·12H2O as compared to that of V2O5.

Recent Developments and Challenges of Vanadium Oxides (Vx Oy ) Cathodes for Aqueous Zinc-Ion Batteries

The rapid depletion of lithium resources and the increasing demand for electrical energy storage have stimulated the pursuit of emerging electrochemical energy storage. Aqueous zinc ion batteries (ZIBs) are highly sought after for their low cost, high safety, and increased environmental compatibility. However, the search for suitable cathode materials is still tricky for a wide range of researchers. Vanadium oxides (V_x O_y ), with their abundant vanadium valence, easily deformable V-O polyhedrons, and tunable chemical compositions, are of significant advantage in developing emerging materials. This work provides a detailed review of different V_x O_y for the application in aqueous ZIBs. The current problems and optimization strategies of V_x O_y cathode materials are systematically discussed. Finally, the current challenges and possible directions for future research of V_x O_y cathode materials in aqueous ZIBs are presented.