Zn Metal Anodes for Zn-Ion Batteries in Mild Aqueous Electrolytes: Challenges and Strategies

Rice powder template for hausmannite Mn3O4 nanoparticles and its application to aqueous zinc ion battery

In this study, a simple calcination route was adopted to prepare hausmannite Mn3O4 nanoparticles using rice powder as soft bio-template. Prepared Mn3O4 was characterized by Fourier Transform Infra-Red Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray microanalysis (EDX), Powder X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) and Solid state UV-Vis spectroscopic techniques. Mn-O stretching in tetrahedral site was confirmed by FTIR and Raman spectra. % of Mn and O content supported Mn3O4 formation. The crystallinity and grain size was found to be 68.76% and 16.43 nm, respectively; tetragonal crystal system was also cleared by XRD. TEM clarified the planes of crystal formed which supported the XRD results and BET demonstrated mesoporous nature of prepared Mn3O4 having low pore volume. Low optical band gap of 3.24 eV of prepared Mn3O4 nanoparticles indicated semiconductor property and was used as cathode material to fabricate CR-2032 coin cell of Aqueous Rechargeable Zinc Ion Battery (ARZIB). A reversible cyclic voltammogram (CV) showed good zinc ion storage performance. Low cell resistance was confirmed by Electrochemical Impedance Spectroscopy (EIS). The coin cell delivered high specific discharge capacity of 240.75 mAhg-1 at 0.1 Ag-1 current density. The coulombic efficiency was found to be 99.98%. It also delivered excellent capacity retention 94.45% and 64.81% after 300 and 1000 charge-discharge cycles, respectively. This work offers a facile and cost effective approach for preparing cathode material of ARZIBs.

Design Strategy of High Stability Vertically Aligned RGO@V2O5 Heterostructure Cathodes for Flexible Quasi-Solid-State Aqueous Zinc-Ion Batteries

Among various cathodes for aqueous zinc-ion batteries (AZIBs), vanadium-based oxides have garnered significant attention in research circles owing to their exceptionally high theoretical specific capacity. However, the outstanding zinc storage capacity of vanadium pentoxide is constrained by its irreversible dissolution in an aqueous solution. Here, we propose a laser reduction of graphene oxide and construct a heterostructure of V2O5 coated with vertically aligned reduced graphene oxide (VrGO). The VrGO nanosheets effectively suppress the dissolution of V2O5 and provide channels for the efficient transport of zinc ions and electrons, so the electrochemical reaction kinetics of the electrode are improved. The AZIB based on the VrGO@V2O5 heterostructure cathode has a high specific capacity of 254.9 mAh g-1 at 0.2 A g-1 and excellent cycle stability with a capacity retention rate of 90.1% after 5000 cycles of charge and discharge. When assembled into a flexible quasi-solid-state AZIB, the capacity of the device is reduced by only 2% after 1000 bending cycles, showing good potential for wearable applications. This work provides a reliable strategy for designing flexible AZIB with high electrochemical performance and structural stability.

Enhancing the Performance of Reversible Zn Deposition by Ultrathin Polyelectrolyte Coatings

Modifying the surfaces of zinc and other metallic substrates is considered an effective strategy to enhance the reversibility of the zinc deposition and stripping processes. While a variety of surface modification strategies have been explored, their ability to be practically implemented is not always trivial due to the associated high costs and complexity of the proposed techniques. In this study, we showcase a straightforward method for preparing ultrathin polyelectrolyte coatings using polydiallyldimethylammonium chloride (PDDA) and polyethylenimine (PEI). The coatings, characterized by their electrostatic charge and hydrophobicity, suppress side reactions and even out the electrodeposition process across the substrate surface. The PDDA-coated anodes demonstrate significantly reduced voltage hysteresis, uniform zinc morphology, improved self-discharge rates, and an impressive Coulombic efficiency exceeding 99% over prolonged cycling. Our findings highlight the potential that such cost-effective and straightforward surface treatments could be widely applied in Zn metal-based batteries.

Covalent Organic Frameworks in Aqueous Zinc-Ion Batteries

The development and utilization of green renewable energy are imperative with the aggravation of environmental pollution and energy crisis. In recent years, the exploration of electrochemical energy storage systems has gradually become a research hotspot in energy. Among them, aqueous zinc-ion batteries (ZIBs) have progressively developed into highly competitive and efficient energy storage devices owing to their inherent safety, natural abundance, and higher theoretical capacity. However, the practical application of ZIBs suffers from the limitation of challenges such as the absence of proper cathode materials and the unavoidable zinc dendrites and side reactions of Zn anode. Covalent organic frameworks (COFs) are an attractive class of electrode materials due to their inherent advantages, like structural designability, high stability, and ordered-open channels, bestowing them with great potential to overcome the problems of ZIBs. In this review, we concentrate on the discussion of designed strategies of COFs applied to ZIBs. Furthermore, the methods of using COFs to solve the challenging problems of cathode development, anode modification, and electrolyte optimization for ZIBs are summarized. Finally, the existing difficulties, solution measures, and prospects of COFs for ZIBs applications are discussed. Our commentary hopes to serve as a valuable reference for developing COFs-based ZIBs.

Ferroelectric-Enhanced cathode kinetics toward High-Performance aqueous Zinc-Ion batteries

Rechargeable aqueous zinc ion batteries (AZIBs) offer promising potential for large-scale energy storage systems due to their high affordability and safety. However, their practical applications are hindered by the undesired rate capability and cycling stability of the used cathode, attributed to sluggish ions kinetics during charge-discharge process. Herein, we propose an electric field balancing strategy to regulate the electrolyte ions behavior by constructing a ferroelectric interface on the cathode surface using a prototypical of MnO2-based cathode. An appropriate thickness coating of ferroelectric materials coating (i.e., β-PVDF) on the MnO2 surface is theoretically and experimentally demonstrated to enhance the ion kinetics due to the optimized electrical distribution during electrochemical operations. Further comprehensive electrochemical mechanism studies reveal that the ferroelectric interface on the MnO2@β-PVDF not only promotes the diffusion of Zn2+ but also reduces the electrochemical overpotential (17.6 mV), resulting in improved electrochemical reversibility and capacity performance. The resultant MnO2@β-PVDF cathode exhibits the highest capacity of 277.6 mAh g-1 (at 0.1 A g-1) and capacity retention of 68.6% after 120 cycles, surpassing both the pristine MnO2 and non-ferroelectric materials coated MnO2 electrodes. This success presents a new approach to enhance the overall electrochemical performance of the cathodes for the practical application of AZIBs.

ZnF2 -Riched Inorganic/Organic Hybrid SEI: in situ-Chemical Construction and Performance-Improving Mechanism for Aqueous Zinc-ion Batteries

Uncontrolled dendrites growth and serious parasitic reactions in aqueous electrolytes, greatly hinder the practical application of aqueous zinc-ion battery. On the basis of in situ-chemical construction and performance-improving mechanism, multifunctional fluoroethylene carbonate (FEC) is introduced into aqueous electrolyte to construct a high-quality and ZnF₂ -riched inorganic/organic hybrid SEI (ZHS) layer on Zn metal anode (ZMA) surface. Notably, FEC additive can regulate the solvated structure of Zn²⁺ to reduce H₂ O molecules reactivity. Additionally, the ZHS layer with strong Zn²⁺ affinity can avoid dendrites formation and hinder the direct contact between the electrolyte and anode. Therefore, the dendrites growth, Zn corrosion, and H₂ evolution reaction on ZMA in FEC-included ZnSO₄ electrolyte are highly suppressed. Thus, ZMA in such electrolyte realize a long cycle life over 1000 h and deliver a stable coulombic efficiency of 99.1 % after 500 cycles.

Inhibition of Zinc Dendrites Realized by a β-P(VDF-TrFE) Nanofiber Layer in Aqueous Zn-Ion Batteries

Uncontrollable Zn dendrite formations and parasitic side reactions on Zn electrodes induce poor cycling stability and safety issues, preventing the large-scale commercialization of Zn-ion batteries. Herein, to achieve uniform Zn deposition and suppress side reactions, an electrospun ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) copolymer, a P(VDF-TrFE) nanofiber layer, is introduced as an artificial solid-electrolyte interface on a Cu substrate acting as a current collector. The aligned molecular structure of β-P(VDF-TrFE) can effectively suppress localized current density on the Cu surface, lead to uniform Zn deposition, and suppress side reactions by preventing direct contact between electrodes and aqueous electrolytes. The half-cell configuration formed by the newly fabricated electrode can achieve an average coulombic efficiency of 99.2% over 300 cycles without short-circuiting at a current density of 1 mA cm^-2 and areal capacity of 1 mAh cm^-2. Stable cycling stability is also maintained for 200 cycles at a current density of 0.5 A g^-1 in a full-cell test using MnO₂ as a cathode.

Artificial Interphase Layer for Stabilized Zn Anodes: Progress and Prospects

The burgeoning Li-ion battery is regarded as a powerful energy storage system by virtue of its high energy density. However, inescapable issues concerning safety and cost aspects retard its prospect in certain application scenarios. Accordingly, strenuous efforts have been devoted to the development of the emerging aqueous Zn-ion battery (AZIB) as an alternative to inflammable organic batteries. In particular, the instability from the anode side severely impedes the commercialization of AZIB. Constructing an artificial interphase layer (AIL) has been widely employed as an effective strategy to stabilize the Zn anode. This review specializes in the state-of-the-art of AIL design for Zn anode protection, encompassing the preparation methods, mechanism investigations, and device performances based on the classification of functional materials. To begin with, the origins of Zn instability are interpreted from the perspective of electrical field, mass transfer, and nucleation process, followed by a comprehensive summary with respect to functions of AIL and its designing criteria. In the end, current challenges and future outlooks based upon theoretical and experimental considerations are included.

Engineering techniques to dendrite free Zinc-based rechargeable batteries

Rechargeable Zn-based batteries (RZBs) have garnered a great interest and are thought to be among the most promising options for next-generation energy storage technologies due to their low price, high levels of safety, adequate energy density and environmental friendliness. However, dendrite formation during stripping/plating prevents rechargeable zinc-based batteries from being used in real-world applications. Dendrite formation is still a concern, despite the fact that inhibitory strategies have been put up recently to eliminate the harmful effects of zinc dendrites. Thus, in order to direct the strategies for inhibiting zinc dendrite growth, it is vital to understand the formation mechanism of zinc dendrites. Hence, for the practical application of zinc-based batteries, is essential to use techniques that effectively prevent the creation and growth of zinc dendrites. The development and growth principles of zinc dendrites are first made clear in this review. The recent advances of solutions to the zinc dendrite problem are then discussed, including strategies to prevent dendrite growth and subsequent creation as much as possible, reduce the negative impacts of dendrites, and create dendrite-free deposition processes. Finally, the challenges and perspective for the development of zinc-based batteries are discussed.

A High-Energy-Density Magnesium-Air Battery with Nanostructured Polymeric Electrodes

The greenhouse emissions are biggest challenge of the present era. The renewable power sources are required to have characteristics of good charge capacity, energy density with proven charging discharging cycles for energy storage and applications. Mg-air batteries (MABs) are an alternative renewable power source due to their inexpensive cost. In particular, the previous reports presented the metal-air battery structure, with a specific energy overall output of 765 W h kg⁻¹. This paper is focused mainly on the MAB, which employed nanocomposite polymeric electrodes with a proven energy density of 545 W h kg⁻¹ and a charge capacity of 817 mA h g⁻¹ when electrolyzed at a cycling current density of 7 mA cm⁻².

Scientific Challenges and Improvement Strategies of Zn-Based Anodes for Aqueous Zn-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) have attracted widespread attention due to the intrinsic features of Zn-based anodes, mainly including high capacity, low cost, and low working potential together with high over-potential for hydrogen evolution reaction. Aqueous ZIBs are considered to be strong competitors and substitutes for lead-acid, nickel-metal hydrogen, nickel-cadmium, and even lithium-ion batteries. Great efforts have been made in the past few years towards the issues existed in aqueous ZIBs, mainly including alkaline and mild acidic systems. In this perspective, we illustrate the advantages, the main challenges, and the corresponding solution strategies of Zn-based anodes in various aqueous rechargeable ZIBs with alkaline and mild acidic electrolytes. Furthermore, feasible aqueous ZIBs for practical use are prospected.

Ammonium vanadate cathode materials with enhanced Zn storage by the optimization of electrolytes

Rechargeable metal ion batteries have been alternatives to traditional fossil fuels in the past decade. Thereinto, aqueous zinc-ion batteries (AZIBs) have attracted one’s widespread attention due to their high theoretical...