Prioritizing Hetero-Metallic Interfaces via Thermodynamics Inertia and Kinetics Zincophilia Metrics for Tough Zn-Based Aqueous Batteries

Engineering low-cost multifunctional carbon interface layer with hydrophobic negative surface and oriented zinc deposition dynamics for dendrite-free zinc ion batteries

Aqueous zinc-ion batteries (AZIBs) are ideal for next-generation energy storage due to low cost, safety, and eco-friendliness, but Zn anode issues like dendrites, hydrogen evolution, and corrosion limit their lifespan. This study engineers a low-cost multifunctional nitrogen-doped porous carbon (NC) interface layer with a three-dimensional (3D) zincophilic structure and a hydrophobic, negatively charged surface for Zn anode. Its conductive 3D structure enables the uniform distribution of the electric field, suppressing dendrite formation and promoting even Zn2+ deposition. On the one hand, the hydrophobic surface minimizes water-zinc interactions, while on the other hand, the negative charge facilitates selective Zn2+ transport and repels sulfate anions, thereby significantly reducing hydrogen evolution and corrosion. Additionally, rich zincophilic sites not only lower the deposition overpotential but also induce (002) crystal-oriented growth, further stabilizing the interface and extending battery life. As a result, symmetric cells assembled with NC-coated Zn electrodes exhibit an impressive cycling life of over 2800 h at a current density of 2 mA cm-2. At higher current densities (10 and 20 mA cm-2), the cells maintain cycling lifetimes of over 1300 and 1000 h, respectively, demonstrating exceptional stability. This work is expected to provide a simple, practical and scalable strategy for developing efficient and stable AZIBs.

Spatially Coupling Electronic-Ionic Transport in Organic Mixed Conductors as Cathodes for Efficient Zn-V Batteries

In conventional electrodes, concentration polarization by unbalanced charge transport and solid-state diffusion resistance result in sluggish reaction kinetics, hindering the practical application of zinc-ion batteries. Here, we propose an integrated mixed electronic-ionic conductor by spatially coupling charge transport pathways, which could achieve redistribution and fast transport of charge (Zn2+/e-). Operando electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy revealed the charge transport mechanisms and intrinsic conducting characteristics at timescale. Through confinement by vanadium oxide, dual-conductive pathways were self-assembled at the nanoscale and provided effective charge storage. This provided high charge density and accelerated ionic diffusion in the bulk phase, resulting in more active sites and faster reaction kinetics. Moreover, reversible ionic channels from the self-doping/de-doping process reduced the dissolution of active materials by protons and enabled conversion chemistry, improving cycling stability at low current density. Consequently, the modulated cathode (PEDOT-SO3-ZnVO) delivered a high-rate performance of 310/148 mAh g-1 (0.2/10 A g-1) at 10 mg cm-2. Importantly, the conventional electrode at 21 mg cm-2 achieved an ultra-high areal capacity of 6.0 mAh cm-2 and superior cycling stability (79.1% retention over 100 cycles at 0.2 A g-1). This work opens the way for the precise modulation of the electrochemical performance of functional nanomaterials.

Overcoming the Challenges in Aqueous Zinc Metal Batteries: Underlying Issues and Mitigation Strategies

The increasing demand for green and clean energy harvesting and their judicious storage call for pursuing new energy storage technologies. Building better batteries has drawn significant attention to fulfilling the energy demand by delivering the stored electrical energy at the anticipated time and minimal cost. Li-ion batteries play a crucial role in transitioning to a sustainable energy landscape. However, their safety and environmental issues are of concern. Zn-based batteries provide more sustainable solutions due to their low cost, enhanced safety, and environmental benignity. Still, poor thermodynamic reversibility and stability of Zn anode in the aqueous electrolytes prevent its practical application. Significant efforts such as Zn anode surface engineering and electrolyte and/or interface modification alleviate these issues. However, in-depth studies of the root causes associated with the reversibility and stability issues of Zn electrodes are still deficient. Hence, this review focuses on the underlying causes of the major issues (dendrite, hydrogen evolution, corrosion, and passivation) associated with Zn anodes. Furthermore, we have summarized the technological advances that have been made to address these issues. Finally, some promising future directions and perspectives are provided for a further in-depth understanding of thermodynamic irreversibility and to improve the overall performance of the Zn anode.

Positively Charged Quasi-Metal-Organic Framework to Reconstruct an Electric Double Layer for a Durable Zn Metal Anode

To reveal the construction principle of an electric double layer (EDL) on a Zn anode, a positively charged artificial solid electrolyte interphase (SEI) is established by a quasi-metal-organic framework with open metal sites (OMSs). As illustrated by theoretical calculation and in situ Raman and Fourier transform infrared spectroscopy characterization, the OMSs are introduced successfully and unsaturated Ce sites bond with SO42- anions as transfer sites for Zn2+, leading to a homogeneous ion distribution within the inner Helmholtz plane (IHP). Therefore, the distribution of Zn2+-H2O-SO42- in the EDL has been adjusted due to the regulating effect by a SEI. Besides, the regulated EDL reduces the concentration of SO42- and free H2O in the IHP, thus promoting uniform Zn2+ deposition and anticorrosion properties of the Zn anode. As a result, the Q-Ce-808@Zn anode demonstrates exceptional cycling stability over 4200 h (1 mA cm-2) and 1300 h (20 mA cm-2).

Sabatier Principle Inspired Bifunctional Alloy Interface for Stable and High-Depth Discharging Zinc Metal Anodes

Achieving stable Zn anodes that can effectively couple with Zn-free cathodes is essential for advancing high-performance Zn metal batteries. Here, we propose a Sabatier principle inspired bifunctional transition-metal (TM) interface to enable homogeneous Zn dissolution during discharging and dendrite-free Zn deposition during charging. Among various TM-coated Zn (TM@Zn) electrodes, Cu@Zn exhibits the highest reversibility and structural stability, attributed to the optimal interaction between Cu and Zn. The heteroatomic interaction-dependent electrochemical performance parallels the Sabatier principle. Morphological analyses reveal that bare Zn anodes display detrimental etching pits during stripping, which is different from the uniform dissolution for Cu@Zn electrodes. During subsequent plating, the conductive interface serves as a secondary current collector for uniform Zn deposition in Cu@Zn, thus demonstrating a bifunctional nature. Atomic observations disclose the working mechanisms of this interface as a gradual phase transition from Cu to CuZn5 during cycling. The Cu@Zn anodes exhibit an ultralong cycling lifespan of over 8000 h at a low current of 1 mA cm-2 and over 250 h at a high depth of discharge of 80 %. They also demonstrate practical feasibility by maintaining 88.7 % capacity retention after 1000 cycles in Cu@Zn||VO2 full cells. This work provides new insights into the Sabatier chemistry inspired bifunctional layers for Zn metal battery system.

Non-coordinating charge transfer enables ultrafast desolvation of hydrated zinc ions in the outer Helmholtz layer for stable aqueous Zn metal batteries

The formation of a strong coordination structure, [Zn(H2O)6]2+ often increases direct contact between the solvated H2O and Zn anodes in the inner Helmholtz layer, which exacerbates undesirable side reactions and dendrite growth, hindering the practical application of aqueous Zn metal batteries. Here, we show that the solvated H2O can be effectively minimized by an artificial solid electrolyte interphase (SEI) consisting of highly nitrogen-doped amorphous carbon (NC) and perfluorosulfonic acid polymer (Nafion). Theoretical and experimental analyses reveal that NC raises the Fermi level of the composite SEI and activates the non-coordinating charge transfer from the SEI to [Zn(H2O)6]2+, which leads to ultrafast desolvation of hydrated Zn-ions in the outer Helmholtz layer; while the Nafion framework ensures selective transport channels for Zn ions. Remarkably, the derived NC-Nafion@Zn symmetric cell exhibits a long lifespan (3400 h, 1 mA cm-2; 2000 h, 5 mA cm-2); moreover, the NC-Nafion@Zn//Mn4O3-carbon nanotubes full battery delivers ultralong cycling stability of 9300 cycles at 2 A g-1 with a high retention of 91.3%.

Sn Penetrated Zincophilic Interface Design in Porous Zn Substrate for High Performance Zn-Ion Battery

Rechargeable zinc-ion batteries are considered an ideal energy storage system due to their low cost and nonflammable aqueous electrolyte. However, dendrite growth, hydrogen evolution reaction, and self-corrosion of zinc anode brought about serious safety risks including short circuits and electrode expansion. Therefore, a modified host-design strategy with a 3D porous structure and bulk-phase penetrated zincophilic interface is proposed to boost the stability and lifetime of the Zn anode. The porous Zn substrate is constructed by universal HCl etching and the uniform and tight Sn-penetrated zincophilic interface is formed by effective electron beam evaporation (EBE). The porous substrate can uniform zinc ion flux and the Sn coating could effectively improve zinc ion deposition behavior, thus inhibiting the risk of dendrites growth and side reaction. As a result, the 3D Zn substrate with Sn interface (3D Zn@Sn) exhibits prolonged galvanostatic cycling performance up to 4500 h with a low polarization of ≈25 mV (1 mA cm-2, 1 mAh cm-2) in the symmetric cell. The full cell assembled with KVOH@Ti could maintain a high specific capacity of 148.6 mAh g-1 after 500 galvanostatic cycles (10 A g-1). This work proposed an improved electrode design to realize the high performance of zinc ion batteries.

Strong Metal-Support Interaction to Invert Hydrogen Evolution Overpotential of Cu Coating for High-Coulombic-Efficiency Stable Zn Anode in Aqueous Zn-Ion Batteries

Cu exhibits strong zincophilic properties but suffers from a much lower hydrogen evolution reaction (HER) overpotential compared to Zn, which significantly undermines the coulombic efficiency and stability of the Zn anode. Consequently, Cu is regarded as an unsuitable coating for Zn anode protection. In this work, the HER overpotential of Cu versus Zn is inverted through strong metal-support interaction (SMSI) to modify the electronic structure of Cu. This interaction facilitates electron transfer, enriching positive charge and slowing down the adsorption kinetics of H+ on the Cu surface. As a result, at very low current densities of 0.2 and 2 mA cm⁻2, the Cu-coated-Zn||Cu cell achieves exceptionally high coulombic efficiencies of 99.11% and 99.91% over 2500 and 1600 h of cycling (100% depth of discharge (DOD)), which remarkably surpasses the performance of Zn anode protective coatings all reported. Moreover, a 1 Ah soft-packed full battery is not bulged and retains 94.7% of its initial capacity after 150 cycles. This study overturns the conventional concept by leveraging SMSI to tune the electronic structure, reverses the HER overpotential, and expands the range of viable metals for anode protection in aqueous metal batteries.

Benchmarking Corrosion with Anionic Polarity Index for Stable and Fast Aqueous Batteries Even in Low-Concentration Electrolyte

Despite aqueous electrolyte endowing batteries with the merits of safe operation, low-cost fabrication, and high ionic conductivity, water-induced corrosion, including spontaneous chemical and electrochemical hydrogen evolution corrosion, adversely affects lifespan and rate capability. There is still a lack of selection criteria for benchmarking corrosion behavior qualitatively. Through theoretical simulation, an anionic polarity index (API) tactic is proposed to resist corrosion by manipulating interfacial and solvated water concomitantly, thus realizing stable and fast Zn aqueous batteries (ZABs). As proof of concept, a low-cost zinc salt of 0.5 m zinc bis(4-hydroxybenzenesulphonate) (Zn(HBS)2) with low-API anion is prioritized. Combined in situ spectroscopic and electrochemical analyses reveal that, even in a low-concentration electrolyte, the low-API anion reduces interfacial water in the inner Helmholtz plane, shielding the chemical water dissociation. Meanwhile, their entering into the solvation sheath of Zn2+ lowers the solvent-separated ion pair, suppressing the electrochemical corrosion. The elaborated API-screened zinc salt endows fast plating kinetics of 50 mA cm-2 (119.1 mV polarization), high coulombic efficiency of 99.8%, dendrite-free cycling over 1600 h, and prolonged lifespan over 5000 cycles for the Zn-V cell. The results provide new metrics that can benchmark the success of ZABs for large-scale energy storage.

Strain-Modulated Deposition Mechanism on a Flexible Zinc Anode

Flexible aqueous zinc-ion batteries (AZIBs) are considered one of the most attractive flexible devices owing to their high theoretical capacity, low cost, and high security. However, the formation of Zn dendrites and the poor flexibility of the Zn material greatly impede the application of wearable AZIBs. Herein, by transferring graphene onto the surface of polyethylene terephthalate-indium tin oxide (PET-ITO-G), a substrate combining excellent flexibility and dendrite suppression ability was prepared. Meanwhile, a quantitative in situ strain application system was proposed to investigate the electrochemical and morphological characteristics of flexible Zn anode interface. The plating/stripping performance of the Zn|PET-ITO-G flexible device was demonstrated under various strains. Subsequent analysis indicated that the origin of its high stability under static bending strain came from the formation of densely packed Zn (101) upon cycling. In addition, PET-ITO-G could quickly recover to Zn (002) after the strain was relieved. A failure model of strain-modulated Zn deposition was proposed based on the formation of surface cracks and distorted surface current distribution. This work identified the main factors that constrained the long cycling life of a flexible metal anode and provided a feasible approach for a systematic study on the influence of in situ strain on flexible batteries.

Fundamentals, Advances and Perspectives in Designing Eutectic Electrolytes for Zinc-Ion Secondary Batteries

Zinc-ion secondary batteries have been competitive candidates since the "post-lithium-ion" era for grid-scale energy storage, owing to their plausible security, high theoretical capacity, plentiful resources, and environment friendliness. However, many encumbrances like notorious parasitic reactions and Zn dendrite growth hinder the development of zinc-ion secondary batteries remarkably. Faced with these challenges, eutectic electrolytes have aroused notable attention by virtue of feasible synthesis and high tunability. This review discusses the definition and advanced functionalities of eutectic electrolytes in detail and divides them into nonaqueous, aqueous, and solid-state eutectic electrolytes with regard to the state and component of electrolytes. In particular, the corresponding chemistry concerning solvation structure regulation, electric double layer (EDL) structure, solid-electrolyte interface (SEI) and charge/ion transport mechanism is systematically elucidated for a deeper understanding of eutectic electrolytes. Moreover, the remaining limitations and further development of eutectic electrolytes are discussed for advanced electrolyte design and extended applications.

Regulating Interfacial Wettability for Fast Mass Transfer in Rechargeable Metal-Based Batteries

The interfacial wettability between electrodes and electrolytes could ensure sufficient physical contact and fast mass transfer at the gas-solid-liquid, solid-liquid, and solid-solid interfaces, which could improve the reaction kinetics and cycle stability of rechargeable metal-based batteries (RMBs). Herein, interfacial wettability engineering at multiphase interfaces is summarized from the electrolyte and electrode aspects to promote the interface reaction rate and durability of RMBs, which illustrates the revolution that is taking place in this field and thus provides inspiration for future developments in RMBs. Specifically, this review presents the principle of interfacial wettability at macro- and microscale and summarizes emerging applications concerning the interfacial wettability effect on mass transfer in RMBs. Moreover, deep insight into the future development of interfacial wettability is provided in the outlook. Therefore, this review not only provides insights into interfacial wettability engineering but also offers strategic guidance for wettability modification and optimization toward stable electrode-electrolyte interfaces for fast mass transfer in RMBs.

A Three-Tiered Golf Anode towards Ultralong-Life Zn-Mn Aqueous Batteries

Zn-Mn aqueous batteries (ZMABs) are widely recognized as a promising candidate for large-scale energy storage due to their cost-effectiveness, high safety and environmental friendliness. However, the practical application of ZMABs is hindered by inherent electrical contact loss, hydrogen evolution and dendrite growth on traditional anodes. Here, a three-tiered golf anode with high conductivity is developed to simultaneously enhance the reversibility of Zn and Mn metals. The three-tiered golf anode is achieved by inner zinc powder, intermediate carbon and outer bismuth layer, which can effectively enhance the Gibbs free energy and mitigate the volume change of the anode, thus enabling stable Zn-Mn cycling. As a proof of concept, Zn-Mn full cells (coupled to CNT@MnO2) achieve an ultralong cycle life with 94.6 % capacity retention at 2 A g-1 after 16,000 cycles. This study presents valuable insights into the structural design of anodes aimed at enhancing the stability and durability of ZMABs.

"Pumping" Trace Cu Impurity out of Zn Foil for Sustainable Aqueous Battery Interface

Dendritic zinc (Zn) electrodeposition presents a significant obstacle to the large-scale development of rechargeable zinc-ion batteries. To mitigate this challenge, various interfacial strategies have been employed. However, these approaches often involve the incorporation of foreign materials onto Zn anode surface, resulting in increased material costs and processing complexities, not to mention the compromised interface endurability due to structural and compositional heterogeneity. Realizing that Cu atoms typically exist as trace impurities in commercial Zn, a novel approach is demonstrated that leverages these Cu impurities to create a Cu-rich surface for effective modulation of Zn electrodeposition. By simply heating commercially available Zn foil with a naturally oxidized surface, not only the internal Cu atoms are thermally activated to become diffusible, their diffusion is also navigated toward the surface via oxygen attraction. The resulting Cu-rich surface effectively regulates Zn electrodeposition, comparable to conventional interfacial strategies, yet exhibits superior cycling durability. 3D in situ microscopy confirms that this Cu-rich surface enables dendrite-free, compact, and (101)-oriented Zn electrodeposition, contrasting with the traditional (002)-oriented dendrite-suppression mechanism. By transforming trace Cu impurity within Zn foil into a Cu-rich surface, this work demonstrates a straightforward, cost-effective and efficient method for controlling Zn electrodeposition.

Innovative Design of a Double-Layer Gradient Coating for Dendrite-Free and Ultrastable Zinc Anodes

The rampant "top-growth" dendrites, hydrogen evolution reaction (HER), and zinc (Zn) self-corrosion severely impede the further development of rechargeable aqueous zinc ion batteries. To address these challenges, a novel double-layer gradient coating consisting of a zincophilic Sn inner layer and an organic polymer outer layer (OSA/PAM@Sn) is constructed on the surface of the Zn anode. The organic outer layer, composed of cross-linked oxidized sodium alginate and polyacrylamide (OSA/PAM), not only serves as a physical barrier to isolate active water but also accelerates Zn2+ diffusion by facilitating the desolvation process of [Zn(H2O)6]2+ due to its plentiful polar functional groups, thereby effectively suppressing the detrimental HER and Zn self-corrosion. Simultaneously, the loose Sn inner layer can offer abundant nucleation sites to induce uniform "bottom-to-top" Zn deposition with low overpotential. Benefiting from the synergistic effect of the designed double-layer gradient coating, the OSA/PAM@Sn-Zn anode exhibits remarkable reversibility, with lifespans of over 5000 and 1200 h at 1 mA cm-2-1 mAh cm-2 and 5 mA cm-2-5 mAh cm-2 in symmetric cells, respectively. Additionally, the MnO2||OSA/PAM@Sn-Zn full battery also displays an improved rate performance and cycle stability. This work emphasizes the importance of synergistic effects in interface design to achieve side reaction-free and dendrite-free Zn anodes.

Design of Highly Stable Binder-Free Sn-Al Sol Coating for Zinc Metal Anode

The construction of artificial solid electrolyte interfaces on zinc anodes is recognized as an effective strategy to mitigate zinc dendrite formation and side reactions; however, existing methods are often complex and time-consuming. In this study, we successfully fabricated a highly stable Sn-Al sol protective layer on the surface of the zinc anode using a simple spray-coating technique. This protective layer significantly enhances the electrochemical performance of zinc symmetric cells, achieving stable cycling for over 2500 h at 1 mA cm-2. In Zn//Cu half-cells, the Sn-Al sol coating improves charge-discharge efficiency and cycling stability, with over 500 and 950 cycles at 1 and 5 mA cm-2, respectively. The average charge-discharge efficiency during stable cycling reaches 95.7%, in contrast to 85.0% for bare Zn, indicating improved utilization of Zn2+. Additionally, the Sn-Al sol coating offers enhanced corrosion resistance and effectively promotes uniform Zn2+ growth along the (101) crystal plane, reducing dendrite formation. Overall, this simple spray-coating approach presents significant potential for high-stability modifications of zinc anodes, offering a novel strategy for the industrial application of zinc-ion batteries.

Delocalized Electron Engineering of MXene-Immobilized Atomic Catalysts toward Fast Desolvation and Dendritic Inhibition for Low-Temperature Zn Metal Batteries

Rechargeable low-temperature aqueous zinc metal batteries (LT-AZMBs) are considered as a competitive candidate for next-generation energy storage systems owing to increased safety and low cost. Unfortunately, sluggish desolvation kinetics of hydrated [Zn(H2O)x]2+ and inhomogeneous ion flux cause detrimental hydrogen evolution reactions (HER) and Zn dendrite growth. Herein, the atomic iron well-implanted onto MXene via defect capture (SAFe@MXene) has been initially proposed to modulate Zn plating. The SAFe@MXene serves as kinetic promoters to enhance interfacial desolvation of [Zn(H2O)x]2+ to prevent HER and uniformizes Zn2+ flux for smooth deposition, as confirmed by theoretical simulation, Raman and electrochemical tests. Consequently, under 0 °C, the SAFe@MXene-modulated Zn electrodes deliver long-term stability of 800 h with lower overpotentials even at 5 mA cm-2 or higher plating/stripping capacity. The full cell with a MnO2 cathode stabilizes a high capacity-retention of nearly 100% after 1000 cycles at 1 A g-1, suggesting great promise for high-performance LT-AZMBs.

Challenges and opportunities in 2D materials for high-performance aqueous ammonium ion batteries

Aqueous ammonium ion batteries (AAIBs) have attracted considerable attention due to their high safety and rapid diffusion kinetics. Unlike spherical metal ions, NH4 + forms hydrogen bonds with host materials, leading to a unique storage mechanism. A variety of electrode materials have been proposed for AAIBs, but their performance often falls short in terms of future energy storage needs. Hence, there is a critical need to design and develop advanced electrode materials for AAIBs. 2D materials, with their tunable interlayer spacing, remarkable interfacial chemistry and abundant surface functional groups, are an ideal choice for electrode materials for NH4 + storage. This review highlights the latest research on 2D electrode materials for AAIBs, providing insights into their working principles, NH4 + storage mechanisms and control strategies for designing high-performance AAIBs. Furthermore, a summary and future perspectives on 2D electrode materials in the development of AAIBs are provided, aiming to promote the advancement of high-performance AAIBs.

Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High-Performance Aqueous Zinc-Vanadium Batteries

A zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn-ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi-functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high-valence Al3+ plays dual roles of competing with Zn2+ for solvation and forming a Zn-Al alloy layer with a homogeneous electric field on the anode surface to mitigate the side reactions and dendrite generation. The Al-containing cathode-electrolyte interface (CEI) considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn||Zn cell with KASO exhibits an ultra-long cycle of 6000 h at 2 mA cm-2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS-KASO electrolyte showed excellent cycling stability, including Zn powder||VO2 cells and Zn||VO2 pouch cells. Even better, the full cell exhibits excellent cycling stability at low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm-2). This study offers a straightforward and practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.

Optimization of the Zinc Deposition Interface by Sn Nanoparticles for Fast-Charging Zinc Metal Anodes

The electrodeposition behavior of zinc metal anodes critically correlates with the electrode surface properties. The tendency for inhomogeneous deposition of zinc is more severe, especially under high current density. Herein, the surface structure of zinc and zinc deposition substrates is reconstructed with a uniform metal tin (Sn) coating via a simple evaporation method. Sn nanoparticles can serve on metal nuclei to reduce the Zn nucleation barrier and enable more nucleation sites for even deposition. Moreover, the mechanical stability of the electrode surface is improved via Zn-Sn alloying. Consequently, the uniform Zn deposition/dissolution behavior on Sn-modified two- and three-dimensional copper substrates is reflected in the stable Coulombic efficiency and reduced polarization. The Sn@Zn electrode is endowed with superior stability at a high current density (800 h at 20 mA cm-2). More encouragingly, the full cell installed with a carbon nanotube/MnO2 cathode maintains enduring stability (700 cycles) at 1 A g-1. This work enlightens metal alloy as an effective and instructive modification strategy toward stabilized zinc anodes.

Monodentate Acetate Anion Enhanced Hydrogel Electrolyte for Long-Term Lifespan Zn-Air Batteries

Flexible Zn-air batteries (FZABs) hold significant promise in diverse application scenarios with high safety and compatibility yet are still impeded by byproduct formation and poor water retention. Here, the neutral hydrogel electrolyte GAHE is engineered by in situ polymerizing acrylamide (AM) in a solution composed of cationic guar gum (CGG) and acetate salts to conquer the above challenges. The acetate anions (OAc-) exert a pH near 7 to effectively inhibit the side reactions triggered by H+. Meanwhile, the monodentate OAc- ions in LiOAc have fast ion diffusion kinetics and form hydrogen bonds between the released carbonyl groups and H2O to further suppress water activity for great side reaction prevention and water retention. Additionally, the in situ polymerization strategy realizes a polymer with high mechanical properties and great electrochemical interfacial stability and further improves the water retention property with hydrophilic groups. Consequently, GAHE gives the FZABs a lifespan of 2050 h at room temperature and 2940 h at -35 °C. This work provides concepts for electrolyte design for water retention and side reaction inhibition properties of aqueous devices.

Gradient Distribution of Zincophilic Sites for Stable Aqueous Zinc-Based Flow Batteries with High Capacity

Current collectors, as reaction sites, play a crucial role in influencing various electrochemical performances in emerging cost-effective zinc-based flow batteries (Zn-based FBs). 3D carbon felts (CF) are commonly used but lack effectiveness in improving Zn metal plating/stripping. Here, a current collector with gravity-induced gradient copper nanoparticles (CF-G-Cu NPs) is developed, integrating gradient conductivity and zincophilicity to regulate Zn deposition and suppress side reactions. The CF-G-Cu NPs electrode modulates Zn nucleation and growth via the zincophilic Cu/CuZn5 alloy has been confirmed by density functional theory (DFT) calculations. Finite element simulation demonstrates the gradient internal structure effectively optimizes the local electric/current field distribution to regulate the Zn2+ flux, improving bottom-up plating behavior for Zn metal and mitigating top-surface dendrite growth. As a result, Zn-based asymmetrical FBs with CF-G-Cu NPs electrodes achieve an areal capacity of 30 mAh cm-2 over 640 h with Coulombic efficiency of 99.5% at 40 mA cm-2. The integrated Zn-Iodide FBs exhibit a competitive long-term lifespan of 2910 h (5800 cycles) with low energy efficiency decay of 0.062% per cycle and high cumulative capacity of 112800 mAh cm-2 at a high current density of 100 mA cm-2. This gradient distribution strategy offers a simple mode for developing Zn-based FB systems.

Innovative Zinc Anodes: Advancing Metallurgy Methods to Battery Applications

Aqueous zinc metal batteries (AZMBs) are emerging as a powerful contender in the realm of large-scale intermittent energy storage systems, presenting a compelling alternative to existing ion battery technologies. They harness the benefits of metal zinc's high safety, natural abundance, and favorable electrochemical potential (-0.762 V vs Standard hydrogen electrode, SHE), alongside an impressive theoretical capacity (820 mAh g-1 and 5655 mAh cm-3). However, the electrochemical performance of ZMBs is impeded by several challenges, including poor compatibility with high-loading cathodes and persistent side reactions. These issues are intricately linked to the inherent physicochemical properties of the zinc metal anodes (ZMAs). Here, this review delves into the traditional methods of ZMAs production, encompassing extraction, electrodeposition, and rolling processes. The discussion then progresses to an exploration of cutting-edge methodologies designed to enhance the electrochemical performance of ZMAs. These methods are categorized into alloying, pre-treatment of substrate, advanced electrodeposition techniques, and the development of composite anodes utilizing zinc powder. The review offers a comparative analysis of the merits and drawbacks of various optimization strategies, highlighting the beneficial outcomes achieved. It aspires to inspire novel concepts for the advancement and innovation of next-generation zinc-based energy storage solutions.

Highly Reversible Zn Anode Design Through Oriented ZnO(002) Facets

The practical implementation of aqueous Zn-ion batteries presents formidable hurdles, including uncontrolled dendrite growth, water-induced side reactions, suboptimal Zn metal utilization, and intricate Zn anode manufacturing. Here, large-scale construction of a highly oriented ZnO(002) lattice plane on Zn anode (ZnO(002)@Zn) with thermodynamic inertia and kinetic zincophilicity is designed to address such problems. Both theoretical calculations and experiment results elucidate that the ZnO(002)@Zn possesses high Zn chemical affinity, hydrogen evolution reaction suppression, and dendrite-free deposition ability due to the abundant lattice oxygen species in ZnO(002) and its low lattice mismatch with Zn(002). These features synergistically promote ion transport and enable homogeneous Zn deposition. Consequently, the ZnO(002)@Zn anode displays a stable and prolonged cycling lifespan exceeding 500 h even under a larger depth of discharge (85.6%) and realizes an impressive average Coulombic efficiency of 99.7%. Moreover, its efficacy is also evident in V2O5-cathode coin cells and pouch cells with not only high discharge capacity but also exceptional cycling stability. This integrated approach presents a promising avenue for addressing the challenges associated with Zn metal anodes, thereby advancing the prospects of aqueous Zn-ion battery technologies.

Tailoring Zn2+ Flux by an Ion Acceleration Layer Modified Separator for High-Rate Long-Lasting Zn Metal Anodes

A large concentration gradient originating from sluggish ion transport on the surface of Zn metal anodes will result in uneven Zn2+ flux, giving rise to severe dendrite growth, especially at high current density. Herein, an ion acceleration layer is introduced by a facile separator engineering strategy to realize modulated Zn2+ flux and dendrite-free deposition. Zinc hexacyanoferrate as the modifying agent featuring strong zincophilicity and rapid diffusion tunnel can enable fast trap for Zn2+ near the electrode surface and immediate transport onto deposition sites, respectively. The ion acceleration effect is substantiated by improved ion conductivity, decreased activated energy, and promoted Zn2+ transference number, which can moderate concentration gradient to guide homogenous Zn2+ flux distribution. As a result, the separator engineering guarantees Zn||Zn symmetrical cells with long-term stability of 2700 h at 2 mA cm-2, and 1770 h at a large current density of 10 mA cm-2. Moreover, cycling stability and rate capability for full cells with different cathodes can be substantially promoted by the modified separator, validating its superior practical feasibility. This study supplies a new scalable approach to tailoring ion flux near the electrode surface to enable robust Zn metal anodes at a high current density.

3D Leaf-Like Copper-Zinc Alloy Enables Dendrite-Free Zinc Anode for Ultra-Long Life Aqueous Zinc Batteries

Metallic zinc exhibits immense potential as an anode material for aqueous rechargeable zinc batteries due to its high theoretical capacity, low redox potential, and inherent safety. However, practical applications are hindered by dendrite formation and poor cycling stability. Herein, a facile substitution reaction method is presented to fabricate a 3D leaf-like Cu@Zn composite anode. This unique architecture, featuring a 3D network of leaf-like Cu on a Zn foil surface, significantly reduces nucleation overpotential and facilitates uniform Zn plating/stripping, effectively suppressing dendrite growth. Notably, an alloy layer of CuZn5 forms in situ on the 3D Cu layer during cycling. DFT calculations reveal that this CuZn5 alloy possesses a lower Zn binding energy compared to both Cu and Zn metal, further promoting Zn plating/stripping and enhancing electrochemical kinetics. Consequently, the symmetric Cu@Zn electrode exhibits remarkable cycling stability, surpassing 1300 h at 0.5 mA cm-2 with negligible dendrite formation. Furthermore, full cells comprising Cu@Zn||VO2 exhibit superior capacity and rate performance compared to bare Zn anodes. This work provides a promising strategy for constructing highly stable and efficient Zn anodes for next-generation aqueous zinc batteries.

Synergetic bifunctional Cu-In alloy interface enables Ah-level Zn metal pouch cells

Rechargeable aqueous zinc-metal batteries, considered as the possible post-lithium-ion battery technology for large-scale energy storage, face severe challenges such as dendrite growth and hydrogen evolution side reaction (HER) on Zn negative electrode. Herein, a three-dimensional Cu-In alloy interface is developed through a facile potential co-replacement route to realize uniform Zn nucleation and HER anticatalytic effect simultaneously. Both theoretical calculations and experimental results demonstrate that this bifunctional Cu-In alloy interface inherits the merits of low Zn-nucleation overpotential and high HER overpotential from individual copper and indium constituents, respectively. Moreover, the dynamical self-reconstruction during cycling leads to an HER-anticatalytic and zincophilic gradient hierarchical structure, enabling highly reversible Zn chemistry with dendrite-free Zn (002) deposition and inhibited HER. Moreover, the improved interface stability featured by negligible pH fluctuations in the diffusion layer and suppressed by-product formation is evidenced by in-situ scanning probe technology, Raman spectroscopy, and electrochemical gas chromatography. Consequently, the lifespan of the CuIn@Zn symmetric cell is extended to more than one year with a voltage hysteresis of 6 mV. Importantly, the CuIn@Zn negative electrode is also successfully coupled with high-loading iodine positive electrode to fabricate Ah-level (1.1 Ah) laminated pouch cell, which exhibits a capacity retention of 67.9% after 1700 cycles.

Dynamically Favorable Ion Channels Enabled by a Hybrid Ionic-Electronic Conducting Film toward Highly Reversible Zinc Metal Anodes

Aqueous zinc ion batteries show great promise for future applications due to their high safety and ecofriendliness. However, nonuniform dendrite growth and parasitic reactions on the Zn anode have severely impeded their use. Herein, a hybrid ionic-electronic conducting ink composed of graphene-like carbon nitride (g-C3N4) and conductive polymers (CP) of poly(3,4ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is introduced to Zn anode using a scalable spray-coating strategy. Notably, the g-C3N4 promotes a screening effect, disrupting the coulombic interaction between the PEDOT+ segments and PSS- chains within CP, thereby reducing interfacial resistance and homogenizing the surface electric field distribution of the Zn anode. Furthermore, the abundant N-containing species and ─SO3 - groups in g-C3N4/CP exhibit strong zincophilicity, which accelerates the diffusion of Zn2+ and disrupts the solvation structure of Zn(H2O)6 2+, thus improving the Zn2+ transfer capability. Consequently, the g-C3N4/CP can powerfully stabilize the Zn2+ flux and thus enable a high coulombic efficiency of 99.47% for 1500 cycles and smooth Zn plating/stripping behaviors more than 3000 h at a typical current density of 1 mA cm-2. These findings shed new light on the Zn electrodeposition process under the mediation of g-C3N4/CP and offer sustainability considerations in designing more stable Zn-metal anodes with enhanced reversibility.

Electrolyte Additive Molecule Disassembly to Reveal the Roles of Individual Groups in Zn Electrode Stabilities in Aqueous Batteries

Zn metal anodes experience dendritic growth and hydrogen evolution reactions (HER) in aqueous batteries. Herein, we propose an interface regulation strategy with a trace (1.4 × 10-4 mol kg-1) all-in-one epicatechin (EC) electrolyte additive to solve the above issues and reveal the roles of individual functional groups. By the disassembly of EC into simple molecules combined with entire molecule investigations, we show that phenol and ether sites preferentially anchor on the Zn surface, while the hydroxyl group pointing outward enters Zn2+ solvation shells at the interface. It modifies the following desolvation path, which not only enables uniform deposition with the thermodynamically favored plate morphology but also inhibits HER. With these synergistic effects of trace EC additive, the lifespan of symmetric cells extends to 8.5 times that of the baseline ZnSO4 electrolyte. The capacity retention of Zn//MnO2 full batteries with N/P = 3 also increases from 59.1 to 85.6% after 500 cycles.

Multiple Heterointerfaces and Heterostructure Engineering in MXene@Co-P-S Hybrids Promote High-Performance Sodium-Ion Half/Full Batteries

In this paper, heterogeneous cobalt phosphosulfide (Co4S3/Co2P) nanocrystals anchoring on few-layered MXene nanosheets (MXene@Co4S3/Co2P) were prepared by in situ growth and the subsequent high-temperature phosphorization/sulfidation processes. Thanks to the synergistic effect and the abundant phase interfaces of Co4S3, Co2P, and MXene, the electron transfer and Na+ diffusion processes were greatly accelerated. Meanwhile, the high electrical conductivity of MXene nanosheets and the heterogeneous structure of Co4S3/Co2P effectively avoided the MXene restacking and the agglomeration of phosphosulfide particles, thus mitigating volumetric expansion during charging and discharging. The results show that the MXene@Co4S3/Co2P heterostructure presents good rate capability (251.08 mAh g-1 at 1 A g-1) and excellent cycling stability (198.69 mAh g-1 after 407 cycles at 5 A g-1). Finally, the storage mechanism of Na+ in the heterostructure and the multistep phase transition reaction were determined by ex situ X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS) analyses. This study provides a new perspective on the formation of metal phosphosulfide and MXene hybrids with multiple heterointerfaces as well as demonstrates MXene@Co4S3/Co2P composites as the promising anode material in sodium-ion batteries.

Oriented Metal Stripping for Highly Reversible Zinc Anode

Aqueous zinc metal batteries are a viable candidate for next-generation energy storage systems, but suffer from poor cycling efficiency of the Zn anode. Emerging approaches aim to regulate zinc plating behavior to suppress uncontrolled dendrites, while the stripping process is seldom considered. Herein, an oriented metal stripping strategy is demonstrated to stabilize the Zn anode by removing high-index facets for exposing the (002) plane through the addition of anionic additive sodium citrate (SC). Consequently, high-index facets that coordinate strongly with SC are preferentially stripped out due to a reduced stripping barrier, rendering stable (002) facet preponderant in epitaxial plating. After repeat stripping/plating, the ultra-high proportion of 93% for (002) and large-size grains of ≈100 µm (six times larger than before) can be obtained. Zn anode shows continuous 25 000 cycles with low overpotential at 100 mA cm-2 in symmetric cells and more than 70 h of stable operation even at an ultra-high depth of discharge of 92.3%. Moreover, an extremely long lifespan of 12 000 cycles at 10 A g-1 with a high capacity retention of 89% is achieved by the assembled Zn//I2 battery. This work provides a distinctive approach to improving the stripping process to design highly efficient zinc anodes for promising aqueous zinc metal batteries.

Achieving a balance of rapid Zn2+ desolvation and hydrogen evolution reaction inertia at the interface of the Zn anode

It is difficult to achieve fast kinetics of Zn2+(H2O)6 desolvation as well as HER inertia at the same electrolyte/Zn interface during long-term cycling of Zn plating/stripping in aqueous Zn-ion batteries. Herein, an effective interface construction strategy with hydrophilic transition metal oxides was proposed to achieve that balance using a CeO2 layer coating. The hydrophilic CeO2 layer can bring a balance between improving the access to the anode surface for Zn2+(H2O)6 electrolyte ions, providing uniform Zn2+ nucleation sites and HER inertia. What's more, Zn corrosion can be significantly inhibited benefiting from this coating layer. The efficiency of aqueous Zn-ion batteries showed a great enhancement. Ultra-long plating/stripping stability up to 1600 h and excellent recovery (returning to 0.5 from 20 mA cm-2) for the symmetric CeO2@Zn system were observed. A full cell with the MnO2 cathode (CeO2@Zn//MnO2) with good reversibility and stability (∼600 cycles) was fabricated for practical application. Our work provides a fundamental understanding and an essential solution to deal with the balance between rapid desolvation and inhibition of the hydrogen evolution reaction, which is important for promoting the practical application of rechargeable Zn batteries.

Interfacial chemistry in multivalent aqueous batteries: fundamentals, challenges, and advances

As one of the most promising electrochemical energy storage systems, aqueous batteries are attracting great interest due to their advantages of high safety, high sustainability, and low costs when compared with commercial lithium-ion batteries, showing great promise for grid-scale energy storage. This invited tutorial review aims to provide universal design principles to address the critical challenges at the electrode-electrolyte interfaces faced by various multivalent aqueous battery systems. Specifically, deposition regulation, ion flux homogenization, and solvation chemistry modulation are proposed as the key principles to tune the inter-component interactions in aqueous batteries, with corresponding interfacial design strategies and their underlying working mechanisms illustrated. In the end, we present a critical analysis on the remaining obstacles necessitated to overcome for the use of aqueous batteries under different practical conditions and provide future prospects towards further advancement of sustainable aqueous energy storage systems with high energy and long durability.

Interface engineering enabled by sodium dodecyl sulfonate surfactant for stable Zn metal batteries

Aqueous zinc-ion batteries are emerging as powerful candidates for large-scale energy storage, due to their inherent high safety and high theoretical capacity. However, the inevitable hydrogen evolution and side effects of the deposition process limit their lifespan, which requires rational engineering of the interface between anode and aqueous electrolyte. In this paper, an anionic surfactant as electrolyte additive, sodium dodecyl sulfonate (SDS), is introduced to deliver highly reversible zinc metal batteries. Unlike traditional surfactants, the solvation structure is not affected by SDS, which tends to adsorb on the (002) crystal plane of Zn with the purpose of effectively limiting the water molecules adsorption. Attributed to the natural hydrophobic part of SDS, a dynamic electrostatic shielding layer and a unique hydrophobic interface are constructed on the anode. Assisted by the above merits, the adverse surface corrosion, hydrogen evolution and dendrite growth are significantly inhibited without the sacrifice in the deposition kinetics of Zn ions. As a result, the Zn||Zn symmetric batteries demonstrate an increased cycle life of 2000 h (1 mA cm-2, 1 mA h cm-2) with the presence of SDS additive. Such strategy provides a new avenue for the developing advanced electrolytes to be applied in aqueous energy storage systems.

Biomass-derived polymer as a flexible "zincophilic-hydrophobic" solid electrolyte interphase layer to enable practical Zn metal anodes

Aqueous zinc ion batteries (AZIBs) face significant challenges stemming from Zn dendrite growth and water-contact attack, primarily due to the lack of a well-designed solid electrolyte interphase (SEI) to safeguard the Zn anode. Herein, we report a bio-mass derived polymer of chitin on Zn anode (Zn@chitin) as a novel and robust artificial SEI layer to boost the Zn anode rechargeability. The polymeric chitin SEI layer features both zincophilic and hydrophobic characteristics to target the suppressed dendritic Zn formation as well as the water-induced side reactions, thus harvesting a dendrite-free and corrosion-resistant Zn anode. More importantly, this polymeric interphase layer is strong and flexible accommodating the volume changes during repeated cycling. Based on these benefits, the Zn@chitin anode demonstrates prolonged cycling performance surpassing 1300 h under an ultra-large current density of 20 mA cm-2, and a long cycle life of 680 h with a record-high zinc utilization rate of 80 %. Besides, the assembled Zn@chitin/V2O5 full batteries reveal excellent capacity retention and rate performance under practical conditions, proving the reliability of our proposed strategy for industrial AZIBs. Our research offers valuable insights for constructing high-performance AZIBs, and simultaneously realizes the high-efficient use of cheap biomass from a "waste-to-wealth" concept.

A Stable High-Performance Zn-Ion Batteries Enabled by Highly Compatible Polar Co-Solvent

Uncontrollable growth of Zn dendrites, irreversible dissolution of cathode material and solidification of aqueous electrolyte at low temperatures severely restrict the development of aqueous Zn-ion batteries. In this work, 2,2,2-trifluoroethanol (TFEA) with a volume fraction of 50% as a highly compatible polar-solvent is introduced to 1.3 M Zn(CF3SO3)2 aqueous electrolyte, achieving stable high-performance Zn-ion batteries. Massive theoretical calculations and characterization analysis demonstrate that TFEA weakens the tip effect of Zn anode and restrains the growth of Zn dendrites due to electrostatic adsorption and coordinate with H2O to disrupt the hydrogen bonding network in water. Furthermore, TFEA increases the wettability of the cathode and alleviates the dissolution of V2O5, thus improving the capacity of the full battery. Based on those positive effects of TFEA on Zn anode, V2O5 cathode, and aqueous electrolyte, the Zn//Zn symmetric cell delivers a long cycle-life of 782 h at 5 mA cm-2 and 2 mA h cm-2. The full battery still declares an initial capacity of 116.78 mA h g-1, and persists 87.73% capacity in 2000 cycles at -25 °C. This work presents an effective strategy for fully compatible co-solvent to promote the stability of Zn anode, V2O5 cathode and aqueous electrolyte for high-performance Zn-ion batteries.

Improvements and Challenges of Hydrogel Polymer Electrolytes for Advanced Zinc Anodes in Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are widely regarded as desirable energy storage devices due to their inherent safety and low cost. Hydrogel polymer electrolytes (HPEs) are cross-linked polymers filled with water and zinc salts. They are not only widely used in flexible batteries but also represent an ideal electrolyte candidate for addressing the issues associated with the Zn anode, including dendrite formation and side reactions. In HPEs, an abundance of hydrophilic groups can form strong hydrogen bonds with water molecules, reducing water activity and inhibiting water decomposition. At the same time, special Zn2+ transport channels can be constructed in HPEs to homogenize the Zn2+ flux and promote uniform Zn deposition. However, HPEs still face issues in practical applications, including poor ionic conductivity, low mechanical strength, poor interface stability, and narrow electrochemical stability windows. This Review discusses the issues associated with HPEs for advanced AZIBs, and the recent progresses are summarized. Finally, the Review outlines the opportunities and challenges for achieving high performance HPEs, facilitating the utilization of HPEs in AZIBs.

A dual-functional electrolyte additive displaying hydrogen bond fusion enables highly reversible aqueous zinc ion batteries

In recent years, aqueous zinc-ion batteries (AZIBs) have attracted significant attention in energy storage due to their notable advantages, including high safety, low cost, high capacity, and environmental friendliness. However, side reactions like hydrogen evolution and zinc (Zn) dendrites can significantly impact their Coulombic efficiency (CE) and lifespan. Effectively addressing these issues has become a focus of research in this field. In our study, dimethyl sulfoxide (DMSO) and nanodiamonds (NDs) were used to optimize the electrolyte of AZIBs. Benefiting from the hydrogen bond fusion of DMSO and NDs, which regulates the Zn deposition behavior, effectively inhibiting the growth of Zn dendrites, hydrogen evolution, and corrosion. The Zn | |Zn symmetric cells using NDs-DMSO-ZS demonstrate exceptional cycling stability for over 1500 h at 1 mA cm-2, while the Zn//Cu asymmetric cells achieve up to 99.8% CE at 2 mA cm-2. This study not only shows the application prospects of electrolyte optimization in enhancing AZIBs performance, but also provides a reference for the advancement of electrolyte technology in advanced AZIBs technology.

Ultra-High Proportion of Grain Boundaries in Zinc Metal Anode Spontaneously Inhibiting Dendrites Growth

Aqueous Zn-ion batteries are an attractive electrochemical energy storage solution for their budget and safe properties. However, dendrites and uncontrolled side reactions in anodes detract the cycle life and energy density of the batteries. Grain boundaries in metals are generally considered as the source of the above problems but we present a diverse result. This study introduces an ultra-high proportion of grain boundaries on zinc electrodes through femtosecond laser bombardment to enhance stability of zinc metal/electrolyte interface. The ultra-high proportion of grain boundaries promotes the homogenization of zinc growth potential, to achieve uniform nucleation and growth, thereby suppressing dendrite formation. Additionally, the abundant active sites mitigate the side reactions during the electrochemical process. Consequently, the 15 μm Fs-Zn||MnO2 pouch cell achieves an energy density of 249.4 Wh kg-1 and operates for over 60 cycles at a depth-of-discharge of 23 %. The recognition of the favorable influence exerted by UP-GBs paves a new way for other metal batteries.

Organic Cations Texture Zinc Metal Anodes for Deep Cycling Aqueous Zinc Batteries

Manipulating the crystallographic orientation of zinc (Zn) metal to expose more (002) planes is promising to stabilize Zn anodes in aqueous electrolytes. However, there remain challenges involving the non-epitaxial electrodeposition of highly (002) textured Zn metal and the maintenance of (002) texture under deep cycling conditions. Herein, a novel organic imidazolium cations-assisted non-epitaxial electrodeposition strategy to texture electrodeposited Zn metals is developed. Taking the 1-butyl-3-methylimidazolium cation (Bmim+) as a paradigm additive, the as-prepared Zn film ((002)-Zn) manifests a compact structure and a highly (002) texture without containing (100) signal. Mechanistic studies reveal that Bmim+ featuring oriented adsorption on the Zn-(002) plane can reduce the growth rate of (002) plane to render the final exposure of (002) texture, and homogenize Zn nucleation and suppress H2 evolution to enable the compact electrodeposition. In addition, the formulated Bmim+-containing ZnSO4 electrolyte effectively sustains the (002) texture even under deep cycling conditions. Consequently, the combination of (002) texture and Bmim+-containing electrolyte endows the (002)-Zn electrode with superior cycling stability over 350 h under 20 mAh cm-2 with 72.6% depth-of-discharge, and assures the stable operation of full Zn batteries with both coin-type and pouch-type configurations, significantly outperforming the (002)-Zn and commercial Zn-based batteries in Bmim+-free electrolytes.

Hybrid Interface Chemistry Enabling Mixed Conducting via Ultrafast Microwave Polarization Toward Dendrite-Free Zn Anodes

Zn metal anodes in aqueous electrolytes suffer from interface issues including uncontrolled dendrite growth and undesired side reactions, resulting in their limited application in terms of short circuits and cell failure. Herein, a hybrid interface chemistry strategy is developed through ultrafast microwave polarization at the skin region of bare Zn. Owing to efficient Joule heating directed by abundant local hot spots at electron valleys, the rapid establishment of a dense interfacial layer can be realized within a minute. Stabilized Zn with suppressed side reactions or surface corrosion is therefore achieved due to the interfacial protection. Importantly, hybrid zincophilic sites involving laterally/vertically interconnected Cu-Zn intermetallic compound and Zn2+-conductive oxide species ensure mixed charge conducting (denoted as CuHL@Zn), featuring uniformly distributed electric field and boosted Zn2+ diffusion kinetics. As a consequence, CuHL@Zn in symmetric cells affords lifespans of 2800 and 3200 h with ultra-low polarization voltages (≈19 and 56 mV) at a plating capacity of 1.0 mAh cm-2 for 1 and 5 mA cm-2, respectively. The CuHL@Zn||MnO2 full cell further exhibits cycling stability with a capacity retention of over 80% for 500 cycles at 2 A g-1.

Dynamic Covalent Bonds Regulate Zinc Plating/Stripping Behaviors for High-Performance Zinc Ion Batteries

Artificial interfaces provide a comprehensive approach to controlling zinc dendrite and surface corrosion in zinc-based aqueous batteries (ZABs). However, due to consistent volume changes during zinc plating/stripping, traditional interfacial layers cannot consistently adapt to the dendrite surface, resulting in uncontrolled dendrite growth and hydrogen evolution. Herein, dynamic covalent bonds exhibit the Janus effect towards zinc deposition at different current densities, presenting a holistic strategy for stabilizing zinc anode. The PBSC intelligent artificial interface consisting of dynamic B-O covalent bonds is developed on zinc anode to mitigate hydrogen evolution and restrict dendrite expansion. Owing to the reversible dynamic bonds, PBSC exhibits shape self-adaptive characteristics at low current rates, which rearranges the network to accommodate volume changes during zinc plating/stripping, resisting hydrogen evolution. Moreover, the rapid association of B-O dynamic bonds enhances mechanical strength at dendrite tips, presenting a shear-thickening effect and suppressing further dendrite growth at high current rates. Therefore, the assembled symmetrical battery with PBSC maintains a stable cycle of 4500 hours without significant performance degradation and the PBSC@Zn||V2O5 pouch cell demonstrates a specific capacity exceeding 170 mAh g-1. Overall, the intelligent interface with dynamic covalent bonds provides innovative approaches for zinc anode interfacial engineering and enhances cycling performance.

Surface Engineering on Zinc Anode for Aqueous Zinc Metal Batteries

Rechargeable aqueous zinc metal batteries (AZMBs) are considered as a potential alternative to lithium-ion batteries due to their low cost, high safety, and environmental friendliness. However, the Zn anodes in AZMBs face severe challenges, such as dendrite growth, metal corrosion, and hydrogen evolution, all of which are closely related to the Zn/electrolyte interface. This article offers a short review on surface passivation to alleviate the issues on the Zn anodes. The composition and structure of the surface layers significantly influence their functions and then the performance of the Zn anodes. The recent progresses are introduced, according to the chemical components of the passivation layers on the Zn anodes. Moreover, the challenges and prospects of surface passivation in stabilizing Zn anodes are discussed, providing valuable guidance for the development of AZMBs.

Host-design strategies of zinc anodes for aqueous zinc-ion batteries

Aqueous zinc ion batteries (AZIBs) have garnered considerable interest as an eco-friendly, safe, and cost-effective energy storage solution. Although significant strides have been made in recent years, there remain technical hurdles to overcome. Herein, this review summarizes in detail the primary challenges confronting aqueous zinc ion batteries, including the rampant dendrite growth, and water-induced parasitic reactions, and proposes host-engineering modification strategies focusing on optimizing the structure design of the zinc anode substrates, involving three-dimensional structure design, zincophilicity regulation, and epitaxial-oriented modification, and comprehensively analyzes the structure-activity relationship between different modification strategies and battery performance. In addition, we highlight the research trends and prospects in future anode modification for aqueous zinc-ion batteries. This work offers valuable insights into advanced Zn anode constructions for further applications in high-performance AZIBs.

Stabilizing Zn/electrolyte Interphasial Chemistry by a Sustained-Release Drug Inspired Indium-Chelated Resin Protective Layer for High-Areal-Capacity Zn//V2O5 Batteries

For zinc-metal batteries, the instable chemistry at Zn/electrolyte interphasial region results in severe hydrogen evolution reaction (HER) and dendrite growth, significantly impairing Zn anode reversibility. Moreover, an often-overlooked aspect is this instability can be further exacerbated by the interaction with dissolved cathode species in full batteries. Here, inspired by sustained-release drug technology, an indium-chelated resin protective layer (Chelex-In), incorporating a sustained-release mechanism for indium, is developed on Zn surface, stabilizing the anode/electrolyte interphase to ensure reversible Zn plating/stripping performance throughout the entire lifespan of Zn//V2O5 batteries. The sustained-release indium onto Zn electrode promotes a persistent anticatalytic effect against HER and fosters uniform heterogeneous Zn nucleation. Meanwhile, on the electrolyte side, the residual resin matrix with immobilized iminodiacetates anions can also repel detrimental anions (SO4 2- and polyoxovanadate ions dissolved from V2O5 cathode) outside the electric double layer. This dual synergetic regulation on both electrode and electrolyte sides culminates a more stable interphasial environment, effectively enhancing Zn anode reversibility in practical high-areal-capacity full battery systems. Consequently, the bio-inspired Chelex-In protective layer enables an ultralong lifespan of Zn anode over 2800 h, which is also successfully demonstrated in ultrahigh areal capacity Zn//V2O5 full batteries (4.79 mAh cm-2).

Regulating Desolvation Activation Energy and Zn Deposition via a CTAB-Intercalated Mg-Al-Layered Double-Hydroxide Protective Layer for Durable Zn Metal Anodes

While aqueous Zn-ion batteries (AZIBs) are widely considered as a promising energy storage system due to their merits of low cost, high specific capacity, and safety, the practical implementation has been hindered by the Zn dendrite growth and undesirable parasitic reactions. To address these issues, a unique hydrophobic-ion-conducting cetyltrimethylammonium bromide-intercalated Mg-Al-layered double-hydroxide protective layer was constructed on the Zn anode (OMALDH-Zn) to modulate the nucleation behavior and desolvation process. The hydrophobic cetyl group long chain can inhibit the hydrogen evolution reaction and Zn corrosion by repelling water molecules from the anode surface and reducing the desolvation activation energy. Meanwhile, the Mg-Al LDH with abundant zincophilic active sites can modulate the Zn2+ ion flux, enabling the dendrite-free Zn deposition. Benefiting from this interfacial synergy, a long cycle life (>2300 h) with low and stable overpotential (<18 mV at 1 mA cm-2) and excellent Coulombic efficiency (99.4%) for symmetrical and asymmetrical batteries were achieved. More impressively, excellent rate performance and long cyclic stability have been realized by OMALDH-Zn//MnO2 batteries in both coin-type and pouch-type devices. This low-cost, simple, and high-efficiency coordinated modulation method provides a reliable strategy for the practical application of AZIBs.

Spontaneous grain refinement effect of rare earth zinc alloy anodes enables stable zinc batteries

Irreversible interfacial reactions at the anodes pose a significant challenge to the long-term stability and lifespan of zinc (Zn) metal batteries, impeding their practical application as energy storage devices. The plating and stripping behavior of Zn ions on polycrystalline surfaces is inherently influenced by the microscopic structure of Zn anodes, a comprehensive understanding of which is crucial but often overlooked. Herein, commercial Zn foils were remodeled through the incorporation of cerium (Ce) elements via the 'pinning effect' during the electrodeposition process. By leveraging the electron-donating effect of Ce atoms segregated at grain boundaries (GBs), the electronic configuration of Zn is restructured to increase active sites for Zn nucleation. This facilitates continuous nucleation throughout the growth stage, leading to a high-rate instantaneous-progressive composite nucleation model that achieves a spatially uniform distribution of Zn nuclei and induces spontaneous grain refinement. Moreover, the incorporation of Ce elements elevates the site energy of GBs, mitigating detrimental parasitic reactions by enhancing the GB stability. Consequently, the remodeled ZnCe electrode exhibits highly reversible Zn plating/stripping with an accumulated capacity of up to 4.0 Ah cm-2 in a Zn symmetric cell over 4000 h without short-circuit behavior. Notably, a ∼0.4 Ah Zn||NH4V4O10 pouch cell runs over 110 cycles with 83% capacity retention with the high-areal-loading cathode (≈20 mg cm-2). This refining-grains strategy offers new insights into designing dendrite-free metal anodes in rechargeable batteries.

Horizontally Arranged Zn Platelet Deposition Regulated by Bi2O3/Bi toward High-Rate and Dendrite-Free 3D Zn Composite Anode

Aqueous Zn-metal battery is considered as a promising energy-storage system. However, uncontrolled zinc dendrite growth is the main cause of short-circuit failure in aqueous Zn-based batteries. One of the most efficient and convenient strategies to alleviate this issue is to introduce appropriate zincophilic nucleation sites to guide zinc metal deposition and regulate crystal growth. Herein, this work proposes Bi2O3/Bi nanosheets anchored on the cell wall surface of the 3D porous conductive host as the Zn deposition sites to modulate Zn deposition behavior and hence inhibit the zinc dendrite growth. Density functional theory and experimental results demonstrate that Bi2O3 has a super zinc binding energy and strong adsorption energy with zinc (002) plane, as a super-zincophilic nucleation site, which results in the deposition of zinc preferentially along the horizontal direction of (002) crystal plane, fundamentally avoids the formation of Zn dendrites. Benefiting from the synergistic effect Bi2O3/Bi zincophilic sites and 3D porous structure in the B-BOGC host, the electrochemical performance of the constructed Zn-based battery is significantly improved. As a result, the Zn anode cycles for 1500 cycles at 50 mA cm-2 and 1.0 mAh cm-2. Meanwhile, the Zn@B-BOGC//MnO2 full cell can operate stably for 2000 cycles at 2.0 A g-1.

Biomimetic Superstructured Interphase for Aqueous Zinc-Ion Batteries

The practical application of aqueous zinc-ion batteries (AZIBs) is greatly challenged by rampant dendrites and pestilent side reactions resulting from an unstable Zn-electrolyte interphase. Herein, we report the construction of a reliable superstructured solid electrolyte interphase for stable Zn anodes by using mesoporous polydopamine (2D-mPDA) platelets as building blocks. The interphase shows a biomimetic nacre's "brick-and-mortar" structure and artificial transmembrane channels of hexagonally ordered mesopores in the plane, overcoming the mechanical robustness and ionic conductivity trade-off. Experimental results and simulations reveal that the -OH and -NH groups on the surface of artificial ion channels can promote rapid desolvation kinetics and serve as an ion sieve to homogenize the Zn2+ flux, thus inhibiting side reactions and ensuring uniform Zn deposition without dendrites. The 2D-mPDA@Zn electrode achieves an ultralow nucleation potential of 35 mV and maintains a Coulombic efficiency of 99.8% over 1500 cycles at 5 mA cm-2. Moreover, the symmetric battery exhibits a prolonged lifespan of over 580 h at a high current density of 20 mA cm-2. This biomimetic superstructured interphase also demonstrates the high feasibility in Zn//VO2 full cells and paves a new route for rechargeable aqueous metal-ion batteries.

A Long-Life and Excellent Rate-Capability Aqueous Zn-Benzoquinone Battery Enabled by Iodine-Catalyzed Cathode

Benzoquinone (BQ) is considered to be a desirable cathode material for aqueous zinc-based batteries. The major limitations of BQ electrode are the severe sublimation and poor electrical conductivity, which results in serious mass loss during electrode preparation and inferior rate performance. In this study, iodine (I2) species are utilized as an efficient catalyst for the highly reversible conversion of BQ/BQ2- couple in the Zn-BQ battery system, wherein N-doped porous carbon is employed as a host material for anchoring the BQ molecule. In the combination electrode (denoted as BQ-I@NPC) with 1wt% I2 additive where I2 can serve as a carrier to accelerates the Zn2+ transmission, and reduce the voltage hysteresis of the electrode. As a result, the BQ-I@NPC cathode delivers a high specific capacity of ≈482 mAh g-1 at 0.25 A g-1, realizing a high energy density of 545 Wh kg-1 (based on BQ), which is the highest values among reported organic cathode materials for aqueous Zn-based batteries. Also, a high BQ loading (8 mg cm-2) can be attained, and achieving a superior cycling stability with a capacity retention of ≈80% after 20,000 times at 10 C. The work proposes an effective approach toward high performance organic electrode materials.