Building Ohmic Contact Interfaces toward Ultrastable Zn Metal Anodes

Establishing Ohmic contact with ultra-thin semiconductor layer through magnetron sputtering for dendrite-free Zn metal batteries

The improvement in reversibility and kinetics for Zn metal anodes is crucial to facilitate the further application of aqueous zinc ion batteries. However, the abnormal surface-caused dendrites and parasitic reactions significantly impede the commercial application. Herein, we established Ohmic contact by fabricating an ultrathin semiconductor ZnTe (∼150 nm) layer on the Zn surface via magnetron sputtering to form an electron enrichment region for zinc ions attraction. Particularly, the ZnTe with a higher work function than that of Zn could render a spontaneous electron transfer from Zn to ZnTe, accelerating the zinc ions diffusion, and repelling water and negative sulfate radicals. As a result, the ultrathin ZnTe layer decreases the nucleation and deposition barrier of Zn leading to homogeneous deposition, and restrains the Zn from corrosion and hydrogen evolution reaction. The ZnTe-modified symmetric cells can stably cycle for over 2,400 h and 1,100 h at current density 1 mA cm-2 with area capacity of 1 mAh cm-2 and 5 mAh cm-2, respectively. The full cell matched with CaV8O20·nH2O shows a 63 % capacity retention after 3,000 cycles at 3 A/g. Our work demonstrates that the construction of Ohmic contact could be an effective way to obtain highly reversible Zn anodes and promote the development of aqueous zinc ions batteries.

Tunable interfacial charge transfer in a nickel sulfide/red phosphorus composite for efficient benzyl alcohol selective oxidation: Effect of nickel sulfide crystal phase

Red phosphorus (RP) has recently attracted considerable attention in the field of photocatalysis owing to its remarkable optical properties. However, the rapid recombination of photogenerated carriers presents a substantial challenge for the application of RP in the selective photocatalytic oxidation of benzyl alcohol. Herein, a series of nickel sulfide (NiS) materials with different crystal phase, including α-NiS, β-NiS and α-β-NiS, were employed to modulate the interfacial charge transfer in RP for photocatalytic oxidation of benzyl alcohol (BA) coupled with H2 evolution. A comprehensive array of experimental and theoretical analyses has demonstrated that the Ohmic junction formed between β-NiS and RP is more conducive to enhancing the separation and migration of carriers in comparison to the Schottky junction formed between α-NiS and RP. As expected, the β-NiS/RP exhibited superior photocatalytic performance, achieving higher yields of benzaldehyde (6.79 μmol g-1 h-1) and H2 (7.16 μmol g-1 h-1) compared to α-NiS/RP, α-β-NiS(glo)/RP and α-β-NiS(fla)/RP. The observed enhancement in photocatalytic activity can primarily be attributed to the distinct carrier separation mechanisms, specifically the Ohmic contact in the β-NiS/RP system and the Schottky junction in the α-NiS/RP system. This study introduces an effective strategy for optimizing carrier migration mechanisms in composite catalysts via crystal phase modulation, thereby providing valuable insights into the design of highly efficient photocatalysts for energy and environmental applications.

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.

Practical issues toward high-voltage aqueous rechargeable batteries

This review offers a critical and exhaustive examination of the current state and innovative advances in high-voltage Li, Na, K, and Zn aqueous rechargeable batteries, an area poised for significant technological breakthroughs in energy storage systems. The practical issues that have traditionally hampered the development of aqueous batteries, such as limited operating potential windows, challenges in stable solid-electrolyte interphase (SEI) formation, the need for active materials optimized for aqueous environments, the misunderstood intercalation chemistry, the unreliable assessment techniques, and the overestimated performance and underestimated physicochemical and electrochemical drawbacks, are highlighted. We believe that this review not only brings together existing knowledge but also pushes the boundaries by providing a roadmap for future research and development efforts aimed at overcoming the longstanding challenges faced by the promising aqueous rechargeable batteries.

Suppressing Hydrogen Evolution and Dendrite Formation on a Zn Anode by Coating In2O3 with Tailored Affinity to H* and Zn

To suppress the hydrogen evolution reaction (HER) and dendrite formation on the Zn anode in aqueous Zn-ion batteries, a submicrometer In2O3 coating on the Zn anode (referred to as Zn@In2O3) was constructed via magnetron sputtering. Density functional theory (DFT) and experimental data show that the In2O3 coating suppresses the HER because of its weaker interactions with H* compared with Zn, inhibiting the Volmer step. At the same time, the In2O3 coating exhibits a moderate affinity for Zn*, higher than that on Zn but lower than that at the In2O3-Zn interface, thus facilitating the desolvation of the hydrated Zn2+ ions while promoting its deposition on the Zn substrate beneath the In2O3 coating. The resultant suppression of side reactions and dendrite growth significantly enhance the reversible plating/stripping of Zn. The optimized Zn@In2O3 stably cycles over 6400 h with a low voltage hysteresis of 9.5 mV at 1 mA cm-2 and 1 mAh cm-2 in symmetric cells. The average Coulombic efficiency of Zn plating/stripping is increased from 95.8 to 99.6% owing to the In2O3 coating. Moreover, when coupled with the Mn0.15V2O5·nH2O cathode, the Zn@In2O3 battery maintains a capacity retention of 78.6% after 2000 cycles at 5 A g-1. This facile and economical modification of Zn anodes provides an idea for realizing the practical application of AZIBs.

Enabling high-performance multivalent metal-ion batteries: current advances and future prospects

The battery market is primarily dominated by lithium technology, which faces severe challenges because of the low abundance and high cost of lithium metal. In this regard, multivalent metal-ion batteries (MVIBs) enabled by multivalent metal ions (e.g. Zn2+, Mg2+, Ca2+, Al3+, etc.) have received great attention as an alternative to traditional lithium-ion batteries (Li-ion batteries) due to the high abundance and low cost of multivalent metals, high safety and higher volumetric capacities. However, the successful application of these battery chemistries requires careful control over electrode and electrolyte chemistries due to the higher charge density and slower kinetics of multivalent metal ions, structural instability of the electrode materials, and interfacial resistance, etc. This review comprehensively explores the recent advancements in electrode and electrolyte materials as well as separators for MVIBs, highlighting the potential of MVIBs to outperform Li-ion batteries regarding cost, energy density and safety. The review first summarizes the recent progress and fundamental charge storage mechanism in several MVIB chemistries, followed by a summary of major challenges. Then, a thorough account of the recently proposed methodologies is given including progress in anode/cathode design, electrolyte modifications, transition to semi-solid- and solid-state electrolytes (SSEs), modifications in separators as well as a description of advanced characterization tools towards understanding the charge storage mechanism. The review also accounts for the recent trend of using artificial intelligence in battery technology. The review concludes with a discussion on prospects, emphasizing the importance of material innovation and sustainability. Overall, this review provides a detailed overview of the current state and future directions of MVIB technology, underscoring its significance in advancing next-generation energy storage solutions.

Design and Regulation of Anthraquinone's Electrochemical Properties in Aqueous Zinc-Ion Batteries via Benzothiadiazole and Its Dinitro Derivatives

Organic cathode materials are widely considered as highly promising for aqueous zinc-ion batteries (AZIBs) due to their tunable properties, low cost, and ease of processing and synthesis. Benzothiadiazoles have demonstrated significant potential as organic electrode materials in AZIBs, owing to their strong electron-accepting capabilities and the presence of multiple reversible redox sites in anthraquinone. In this study, we designed a polymer, poly(2-methyl-6-(7-methyl-5,6-dinitrobenzo[c][1,2,5]thiadiazol-4-yl)anthracene-9,10-dione) (PBDQ), with multielectron transfer capability through a copolymerization approach. Additionally, we synthesized another polymer, poly2,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)anthracene-9,10-dione(PBDQ-N), by introducing two electron-withdrawing nitro groups on the aromatic ring of benzothiadiazole. The introduction of nitro groups, with their unique electronic properties, enhances electron delocalization and increases the number of electrochemically active sites, thereby promoting faster zinc-ion insertion/extraction reactions. Experimental results show that both PBDQ and PBDQ-N exhibit excellent electrochemical properties due to the abundance of active sites and extended π-conjugation. Among them, PBDQ-N demonstrates outstanding performance, including an ultrahigh specific capacity of 446.2 mAh g-1 at 0.1 A g-1 and excellent cycle life exceeding 20,000 cycles at 10 A g-1. Moreover, the lower lowest-unoccupied molecular orbital (LUMO) energy level and improved conductivity of PBDQ-N provide a fast electron transfer rate, resulting in a higher Zn2+ diffusion coefficient (3.47 × 10-11-2.6 × 10-8 cm2 s-1) and exceptional rate performance (234.6 mAh g-1 at 10 A g-1). Theoretical calculations and ex situ characterizations confirm that C═O, C═N, and N═O groups all participate as active sites in Zn2+ storage. This work highlights how molecular design and the introduction of functional groups, such as nitro groups, can effectively regulate the electrochemical properties of organic polymers in AZIBs. It also demonstrates the impact of these strategies on the electrochemical performances of these materials when they are used as cathodes in aqueous zinc-ion batteries.

Engineering of Charge Density at the Anode/Electrolyte Interface for Long-Life Zn Anode in Aqueous Zinc Ion Battery

The aqueous zinc ion battery emerges as the promising candidate applied in large-scale energy storage system. However, Zn anode suffers from the issues including Zn dendrite, Hydrogen evolution reaction and corrosion. These challenges are primarily derived from the instability of anode/electrolyte interface, which is associated with the interfacial charge density distribution. In this context, the recent advancements concentrating on the strategies and mechanisms to regulate charge density at the Zn anode/electrolyte interface are summarized. Different characterization techniques for charge density distribution have been analysed, which can be applied to assess the interfacial zinc ion transport. Additionally, the charge density regulations at the Zn anode/electrolyte interface are discussed, elucidating their roles in modulating electrostatic interactions, electric field, structure of solvated zinc ion and electric double layer, respectively. Finally, the perspectives and challenges on the further research are provided to establish the stable anode/electrolyte interface by focusing on charge density modifications, which is expected to facilitate the development of aqueous zinc ion battery.

Highly Reversible Dendrite-Free Zinc Anode Enabled by a Bilayered Inorganic-Metal Interface Layer

The unavoidable dendrite growth and side reactions are two major issues that lead to unsatisfactory cycling stability of the Zn metal anode and premature battery failure, which constrains the wide practical application of aqueous Zn-ion batteries. Herein, a bilayered zinc fluoride-indium interface-modified zinc anode (ZnF2-In@Zn) is in situ-constructed to solve these two issues through a simple solution-dipping strategy. The outer ZnF2 layer assures sufficient desolvation of hydrated Zn2+ and even Zn2+ flux; meanwhile, the interior In layer further contributes to the uniform distribution of the electric field and lower energy barrier of Zn2+ nucleation, achieving dendrite-free and side reaction-free Zn deposition. With synergistic regulation from the bilayered composite interface, the ZnF2-In@Zn anode exhibits outstanding cycling stability (over 4200 h at 1 mA cm-2), achieving a cumulative capacity of over 5250 mAh cm-2 even under a high current density of 5 mA cm-2. This work proposes an advanced understanding of reasonable interface engineering for tackling multiple challenges faced by metal anodes.

Ferroelectric Interfaces for Dendrite Prevention in Zinc-Ion Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) are increasingly recognized as promising energy storage systems for mini-grid and mini-off-grid applications due to their advantageous characteristics such as high safety, affordability, and considerable theoretical capacity. However, the long-term cycling performance of ZIBs is hampered by challenges including the uncontrolled dendrite formation, the passivation, and the occurrence of the hydrogen evolution reaction (HER) on the Zn anode. In this study, enhancing ZIB performance by implementing oxide material coatings on Zn metal, serving as a physical barrier at the electrode-electrolyte interfaces to mitigate dendrite growth and suppress the HER is concentrated. Specifically, the mechanisms through which the n-type semiconductor TiO2 coated Zn anode establishes ohmic contact with Zn, and the high-dielectric BaTiO3 (BTO) coated Zn anode fosters Maxwell-Wagner polarization with ferroelectric properties, significantly inhibiting dendrite growth and side reactions, thereby resulting in a highly stable Zn anode for efficient aqueous ZIBs is explored. This advanced BTO/Zn electrode demonstrates an extended lifespan of over 700 h compared to bare Zn and TiO2/Zn anodes. Additionally, full-cell aqueous ZIBs incorporating BTO/Zn//VO2 (B) batteries exhibit superior rate capabilities, high capacity, and sustained cycle life.

Achieving Stable Orientational Zinc Deposition for Reversible Zinc Anode through Supramolecular Anchoring Mechanism

Aqueous zinc-ion batteries have been impeded by the hydrogen evolution reaction (HER), uncontrolled zinc dendrites, and side reactions on the Zn anode. In this work, a Zn-polyphenol supramolecular network is rationally designed for stabilizing Zn anodes (ZPN@Zn) even at high current density. Theoretical calculations and experiments show that the zinc-polyphenol supramolecular layer effectively inhibits the hydrogen evolution reaction by capturing water molecules through strong hydrogen bonding networks while also facilitating the rapid replenishment of Zn2+ ions at the interface through supramolecular anchoring. Additionally, it results in preferential deposition of Zn on the (002) plane, thereby contributing to nondendritic and highly reversible Zn plating/stripping behaviors even under high rates. Concomitantly, the ZPN@Zn achieves superior stability of nearly 1200 h at a high current density of 20 mA cm-2 and maintains a high CE efficiency of 99.86% after 3000 cycles at 1 mAh cm-2 and 5 mA cm-2. Remarkably, the full cell assembled with ZPN@Zn and NaV3O8 (NVO) endures 25 000 cycles at 20 A g-1, achieving an impressive performance for the realization of dendrite-free Zn anodes by supramolecular modulation.

A "Zn2+ in Salt" Interphase Enabling High-Performance Zn Metal Anodes

Zinc metal is a promising anode candidate for aqueous zinc ion batteries due to its high theoretical capacity, low cost, and high safety. However, its application is currently restricted by hydrogen evolution reactions (HER), by-product formation, and Zn dendrite growth. Herein, a "Zn2+ in salt" (ZIS) interphase is in situ constructed on the surface of the anode (ZIS@Zn). Unlike the conventional "Zn2+ in water" working environment of Zn anodes, the intrinsic hydrophobicity of the ZIS interphase isolates the anode from direct contact with the aqueous electrolyte, thereby protecting it from HER, and the accompanying side reactions. More importantly, it works as an ordered water-free ion-conducting medium, which guides uniform Zn deposition and facilitates rapid Zn2+ migration at the interface. As a result, the symmetric cells assembled with ZIS@Zn exhibit dendrite-free plating/striping at 4500 h and a high critical current of 14 mA cm-2. When matched with a vanadium-based (NVO) cathode, the full battery exhibits excellent long-term cycling stability, with 88% capacity retention after 1600 cycles. This work provides an effective strategy to promote the stability and reversibility of Zn anodes in aqueous electrolytes.

Accelerated and Guided Zn2+ Diffusion via Polarized Interface Engineering Toward High Performance Wearable Zinc-Ion Batteries

Rechargeable aqueous Zn-ion batteries (ZIBs) are considered as a new energy storage device for wearable electronic equipment. Nowadays, dendrite growth and uneven deposition of zinc have been the principal problems to suppress the development of high-performance wearable zinc-ion batteries. Herein, a perovskite material of LaAlO3 nanoparticle has been applied for interface engineering and zinc anode protection. By adjusting transport channels and accelerating the Zn2+ diffusion, the hydrogen evolution reaction potential is improved, and electric field distribution on the Zn electrode surface is regulated to navigate the fast and uniform deposition of Zn2+. As a proof of demonstration, the assembled LAO@Zn||MnO2 batteries can display the highest capacity of up to 140 mAh g-1 without noticeable decay even after 1000 cycles. Moreover, a motor-driven fan and electronic wristwatch powered by wearable ZIBs can demonstrate the practical feasibility of LAO@Zn||MnO2 in wearable electronic equipment.

Zincophilic Nanospheres Assembled as Solid-Electrolyte Interphase on Zn Metal Anodes for Reversible High-rate Zn-Ion Storage

Aqueous Zn-ion batteries (ZIBs) are considered to be one of the most promising energy storage devices in the post-lithium-ion era with fast ionic conductivity, safety, and low cost. However, excessive accumulation of zinc dendrites will fracture and produce dead zinc, resulting in the unsatisfied utilization rate of Zn anodes, which greatly restricts the lifespan of the battery and reduces the reversibility. In this paper, by constructing a protective layer of ZnSnO3 hollow nanospheres in situ growth on the surface of the Zn anode, more zincophilic sites are established on the electrode surface. It demonstrates that uniform deposition of Zn ions by deepening the binding energy with Zn ion and its unique hollow structure shortens the diffusion distance of Zn ions and enhances the reaction kinetics. The assembled Zn-ion hybrid supercapacitor (ZHSC) of ZnSnO3@Zn//AC achieved a long-term lifespan with 4000 cycles at a current density of 10 mA cm-2 with a Coulombic efficiency of 99.31% and capacity retention of 79.6%. This work offers a new path for advanced Zn anodes interphase supporting the long cycle life with large capacities and improving electrochemical reversibility.

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.

Heterointerfaces: Unlocking Superior Capacity and Rapid Mass Transfer Dynamics in Energy Storage Electrodes

Heterogeneous electrode materials possess abundant heterointerfaces with a localized "space charge effect", which enhances capacity output and accelerates mass/charge transfer dynamics in energy storage devices (ESDs). These promising features open new possibilities for demanding applications such as electric vehicles, grid energy storage, and portable electronics. However, the fundamental principles and working mechanisms that govern heterointerfaces are not yet fully understood, impeding the rational design of electrode materials. In this study, the heterointerface evolution during charging and discharging process as well as the intricate interaction between heterointerfaces and charge/mass transport phenomena, is systematically discussed. Guidelines along with feasible strategies for engineering structural heterointerfaces to address specific challenges encountered in various application scenarios, are also provided. This review offers innovative solutions for the development of heterogeneous electrode materials, enabling more efficient energy storage beyond conventional electrochemistry. Furthermore, it provides fresh insights into the advancement of clean energy conversion and storage technologies. This review contributes to the knowledge and understanding of heterointerfaces, paving the way for the design and optimization of next-generation energy storage materials for a sustainable future.

In Situ Constructing Metal-Organic Complex Interface Layer Using Biomolecule Enabling Stabilize Zn Anode

Aqueous zinc-ion batteries (ZIBs) are considered as a promising candidate for next-generation large-scale energy storage due to their high safety, low cost, and eco-friendliness. Unfortunately, commercialization of ZIBs is severely hindered owing to rampant dendrite growth and detrimental side reactions on the Zn anode. Herein, inspired by the metal-organic complex interphase strategy, the authors apply adenosine triphosphate (ATP) to in situ construct a multifunctional film on the metal Zn surface (marked as ATP@Zn) by a facile etching method. The ATP-induced interfacial layer enhances lipophilicity, promoting uniform Zn2+ flux and further homogenizing Zn deposition. Meanwhile, the functional interlayer improves the anticorrosion ability of the Zn anode, effectively suppressing corrosion and hydrogen evolution. Consequently, the as-prepared ATP@Zn anode in the symmetric cell exhibits eminent plating/stripping reversibility for over 2800 h at 5.0 mA cm-2 and 1 mAh cm-2. Furthermore, the assembled ATP@Zn||MnO2 full cells are investigated to evaluate practical feasibilities. This work provides an efficient and simple strategy to prepare stabilized Zn anode toward high-performance ZIBs.

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.

Design Strategies toward High-Performance Zn Metal Anode

Rechargeable aqueous Zn-ion batteries (AZIBs) are one of the most promising alternatives for traditional energy-storage devices because of their low cost, abundant resources, environmental friendliness, and inherent safety. However, several detrimental issues with Zn metal anodes including Zn dendrite formation, hydrogen evolution, corrosion and passivation, should be considered when designing advanced AZIBs. Moreover, these thorny issues are not independent but mutually reinforcing, covering many technical and processing parameters. Therefore, it is necessary to comprehensively summarize the issues facing Zn anodes and the corresponding strategies to develop roadmaps for the development of high-performance Zn anodes. Herein, the failure mechanisms of Zn anodes and their corresponding impacts are outlined. Recent progress on improving the stability of Zn anode is summarized, including structurally designed Zn anodes, Zn alloy anodes, surface modification, electrolyte optimization, and separator design. Finally, this review provides brilliant and insightful perspectives for stable Zn metal anodes and promotes the large-scale application of AZIBs in power grid systems.

Dendrite-Free Zinc Anodes Enabled by Exploring Polar-Face-Rich 2D ZnO Interfacial Layers for Rechargeable Zn-Ion Batteries

Zinc metal is a promising candidate for anodes in zinc-ion batteries (ZIBs), but its widespread implementation is hindered by dendrite growth in aqueous electrolytes. Dendrites lead to undesirable side reactions, such as hydrogen evolution, passivation, and corrosion, causing reduced capacity during prolonged cycling. In this study, an approach is explored to address this challenge by directly growing 1D zinc oxide (ZnO) nanorods (NRs) and 2D ZnO nanoflakes (NFs) on Zn anodes, forming artificial layers to enhance ZIB performance. The incorporation of ZnO on the anode offers both chemical and thermal stability and leverages its n-type semiconductor nature to facilitate the formation of ohmic contacts. This results in efficient electron transport during Zn ion plating and stripping processes. Consequently, the ZnO NFs-coated Zn anodes demonstrate significantly improved charge storage performance, achieving 348 mAh g-1, as compared to ZnO NRs (250 mAh g-1) and pristine Zn (160 mAh g-1) anodes when evaluated in full cells with V2O5 cathodes. One significant advantage of ZnO NFs lies in their highly polar surfaces, promoting strong interactions with water molecules and rendering them exceptionally hydrophilic. This characteristic enhances the ability of ZnO NFs to desolvate Zn2+ ions, leading to improved charge storage performance.

Defect-Rich Functional HfO2-x for Highly Reversible Zn Metal Anode

Interface engineering attracted tremendous attention owing to its remarkable ability to impede dendrite growth and side reactions in aqueous zinc-ion batteries. Artificial interface layers composed of crystalline materials have been extensively employed to stabilize the Zn anode. However, the diffusion kinetics of Zn2+ in highly crystalline materials are hindered by steric effects from the lattice, thereby limiting the high-rate performance of the cell. Here, defect-rich HfO2-x polycrystals derived from metal-organic frameworks (MOFs) (D-HfO2-x) are developed to enhance the Zn deposition behavior. The discrepancy of dielectric constants between metallic Zn and HfO2 enables the building of an electrostatic shielding layer for uniform Zn deposition. More importantly, the oxygen vacancies in D-HfO2-x provide abundant active sites for Zn2+ adsorption, accelerating the kinetics of Zn2+ migration, which contributes to the preferential exposure of the Zn (002) plane during plating. Consequently, the D-HfO2-x-modified Zn anode delivers ultrastable durability of over 5000 h at 1 mA cm-2 and a low voltage hysteresis of 30 mV. The constructed defective coating provides a guarantee for the stable operation of Zn anodes, and the innovative approach of defective engineering also offers new ideas for the protection of other energy storage devices.

Synergistic Modulation of Mass Transfer and Parasitic Reactions of Zn Metal Anode via Bioinspired Artificial Protection Layer

Rechargeable aqueous zinc-ion batteries are regarded as promising energy storage devices due to their attractive economic benefits and extraordinary electrochemical performance. However, the sluggish Zn2+ mass transfer behavior and water-induced parasitic reactions that occurred on the anode-electrode interface inevitably restrain their applications. Herein, inspired by the selective permeability and superior stability of plasma membrane, a thin UiO-66 metal-organic framework layer with smart aperture size is ex-situ decorated onto the Zn anode. Experimental characterizations in conjunction with theoretical calculations demonstrate that this bio-inspired layer promotes the de-solvation process of hydrated Zn2+ and reduces the effective contact between the anode and H2 O molecules, thereby boosting Zn2+ deposition kinetics and restraining interfacial parasitic reactions. Hence, the Zn||Zn cells could sustain a long lifespan of 1680 h and the Zn||Cu cells yielded a stable coulombic efficiency of over 99.3% throughout 600 cycles under the assistance of the bio-inspired layer. Moreover, pairing with δ-MnO2 cathode, the full cells also demonstrate prominent cycling stability and rate performance. From the bio-inspired design philosophy, this work provides a novel insight into the development of aqueous batteries.

Understanding the Electrical Mechanisms in Aqueous Zinc Metal Batteries: From Electrostatic Interactions to Electric Field Regulation

Aqueous Zn metal batteries are considered as competitive candidates for next-generation energy storage systems due to their excellent safety, low cost, and environmental friendliness. However, the inevitable dendrite growth, severe hydrogen evolution, surface passivation, and sluggish reaction kinetics of Zn metal anodes hinder the practical application of Zn metal batteries. Detailed summaries and prospects have been reported focusing on the research progress and challenges of Zn metal anodes, including electrolyte engineering, electrode structure design, and surface modification. However, the essential electrical mechanisms that significantly influence Zn2+ ions migration and deposition behaviors have not been reviewed yet. Herein, in this review, the regulation mechanisms of electrical-related electrostatic repulsive/attractive interactions on Zn2+ ions migration, desolvation, and deposition behaviors are systematically discussed. Meanwhile, electric field regulation strategies to promote the Zn2+ ions diffusion and uniform Zn deposition are comprehensively reviewed, including enhancing and homogenizing electric field intensity inside the batteries and adding external magnetic/pressure/thermal field to couple with the electric field. Finally, future perspectives on the research directions of the electrical-related strategies for building better Zn metal batteries in practical applications are offered.

Achieving highly reversible zinc metal anode via surface termination chemistry

An oxidation layer on a Zn surface is considered to play a negative role in hindering the practical applications of aqueous zinc ion batteries (AZBs). Herein, we demonstrate the importance of Zn-surface termination on the overall electrochemical behavior of AZBs by revisiting the well-known bottleneck issues. Experimental characterizations in conjugation with theoretical calculations reveal that the formation of a dense Zn4(OH)6SO4·xH2O (ZSH) layer from the well-designed surface-oxide termination layer improves the interface stability of the Zn anode and reduces the dehydration energy of Zn(H2O)62+, thereby accelerating the interface transport kinetics of Zn2+. Moreover, instead of directly diffusing over the ZSH layer, a new "edge dehydration-along edge transfer" mechanism of Zn2+ is discovered. Owing to the presence of a Zn anode with a ZnO-derived ZSH layer, an ultrahigh stability of over 1200 h with a high cumulative-plated capacity of 6.24mAh cm-2 is achieved with a symmetrical cell. Furthermore, high cycling stability (over 1000 cycles) and Coulombic efficiency (99.07%) are obtained in the entire AZBs with a MnO2 cathode. An understanding of the oxygen surface termination mechanism is beneficial to Zn-anode protection and is a timely forward step toward the long-pursued practical application of AZBs.

Manipulating the Host-Guest Chemistry of Cucurbituril to Propel Highly Reversible Zinc Metal Anodes

Rechargeable aqueous zinc-ion batteries are practically plagued by the short lifespan and low Coulombic efficiency (CE) of Zn anodes resulting from random dendrite deposition and parasitic reactions. Herein, the host-guest chemistry of cucurbituril additive with Zn2+ to achieve longstanding Zn anodes is manipulated. The macrocyclic molecule of cucurbit[5]uril (CB[5]) is delicately designed to reconstruct both the CB[5]-adsorbed electric-double layer (EDL) structure at the Zn interface and the hydrated sheath of Zn2+ ions. Especially benefiting from the desirable carbonyl rims and suitable hydrophobic cavities, the CB[5] has a strong host-guest interaction with Zn2+ ions, which exclusively permits rapid Zn2+ flux across the EDL interface but retards the H2 O radicals and SO4 2- . Accordingly, such a unique particle redistributor warrants long-lasting dendrite-free deposition by homogenizing Zn nucleation/growth and significantly improved CE by inhibiting side reactions. The Zn anode can deliver superior reversibility in CB[5]-containing electrolyte with a ninefold increase of cycle lifetime and an elevated CE of 99.7% under harsh test conditions (10 mA cm-2 /10 mA h cm-2 ). The work opens a new avenue from the perspective of host-guest chemistry to propel the development of rechargeable Zn metal batteries and beyond.

An Ultrathin Inorganic Molecular Crystal Interfacial Layer for Stable Zn Anode

Zn metal anode suffers from dendrite growth and side reactions during cycling, significantly deteriorating the lifespan of aqueous Zn metal batteries. Herein, we introduced an ultrathin and ultra-flat Sb2 O3 molecular crystal layer to stabilize Zn anode. The in situ optical and atomic force microscopes observations show that such a 10 nm Sb2 O3 thin layer could ensure uniform under-layer Zn deposition with suppressed tip growth effect, while the traditional WO3 layer undergoes an uncontrolled up-layer Zn deposition. The superior regulation capability is attributed to the good electronic-blocking ability and low Zn affinity of the molecular crystal layer, free of dangling bonds. Electrochemical tests exhibit Sb2 O3 layer can significantly improve the cycle life of Zn anode from 72 h to 2800 h, in contrast to the 900 h of much thicker WO3 even in 100 nm. This research opens up the application of inorganic molecular crystals as the interfacial layer of Zn anode.

A Stable Triazole-Based Covalent Gel for Long-Term Cycling Zn Anode in Zinc-Ion Batteries

In this work, a functional covalent gel material is developed to resolve the severe dendritic growth and hydrogen evolution reaction toward Zn/electrolyte interface in aqueous zinc-ion batteries (ZIBs). A covalent gel layer with superior durability forms homogeneously on the surface of Zn foil. The covalent gel with triazole functional groups can uniformize the transport of Zn2+ due to the interactions between Zn2+ ions and the triazole groups in the covalent gel. As a consequence, the symmetrical battery with triazole covalent gel maintains stable Zn plating/stripping for over 3000 h at 1 mA cm-2 and 1 mAh cm-2 , and the full cell combined with a V2 O5 cathode operates steadily and continuously for at least 1800 cycles at 5 A g-1 with a capacity retention rate of 67.0%. This work provides a train of thought to develop stable covalent gels for the protection of zinc anode toward high-performance ZIBs.

An aqueous electrolyte densified by perovskite SrTiO3 enabling high-voltage zinc-ion batteries

The conventional weak acidic electrolyte for aqueous zinc-ion batteries breeds many challenges, such as undesirable side reactions, and inhomogeneous zinc dendrite growth, leading to low Coulombic efficiency, low specific capacity, and poor cycle stability. Here, an aqueous densified electrolyte, namely, a conventional aqueous electrolyte with addition of perovskite SrTiO3 powder, is developed to achieve high-performance aqueous zinc-ion batteries. The densified electrolyte demonstrates unique properties of reducing water molecule activity, improving Zn2+ transference number, and inducing homogeneous and preferential deposition of Zn (002). As a result, the densified electrolyte exhibits an ultra-long cycle stability over 1000 cycles in Zn/Ti half cells. In addition, the densified electrolyte enables Zn/MnO2 cells with a high specific capacity of 328.2 mAh g-1 at 1 A g-1 after 500 cycles under an extended voltage range. This work provides a simple strategy to induce dendrite-free deposition characteristics and high performance in high-voltage aqueous zinc-ion batteries.

Nucleophilic deposition behavior of metal anodes

Nucleophilic materials play important roles in the deposition behavior of high-energy-density metal batteries (Li, Na, K, Zn, and Ca), while the principle and determination method of nucleophilicity are lacking. In this review, we summarize the metal extraction/deposition process to find out the mechanism of nucleophilic deposition behavior. The key points of the most critical nucleophilic behavior were found by combining the potential change, thermodynamic analysis, and active metal deposition behavior. On this basis, the inductivity and affinity of the material have been determined by Gibbs free energy directly. Thus, the inducibility of most materials has been classified: (a) induced nuclei can reduce the overpotential of active metals; (b) not all materials can induce active metal deposition; (c) the induced reaction is not changeless. Based on these results, the influencing factors (temperature, mass, phase state, induced reaction product, and alloying reactions) were also taken into account during the choice of inducers for active metal deposition. Finally, the critical issues, challenges, and perspectives for further development of high-utilization metal electrodes were considered comprehensively.

Cation‐Selective Interface for Kinetically Enhanced Dendrite‐Free Zn Anodes

The Zn anode in aqueous zinc‐ion batteries (AZIBs) is severely impeded by uncontrolled dendrite growth and promiscuous water‐induced side reactions, resulting in low Coulombic efficiency (CE) and poor lifetime. Herein, a versatile Zn‐based laponite (Zn–LT) interface is constructed for uniform and rapid Zn deposition for long‐life AZIBs. The combined experimental results and theoretical simulations reveal that the abundant negatively charged channels in the Zn–LT layer permit cation penetration but shield anions to uniformly modulate Zn deposition. Moreover, Zn–LT not only acts as a desolvation layer to promote Zn deposition kinetics, but also effectively inhibit harmful Zn anode corrosion. Therefore, the functional Zn–LT interface enables the anode to deliver an average CE as high as 99.8% at 1 mA cm−2 and a long lifespan of >830 h at 10 mA cm−2 and 5 mA h cm−2. Moreover, the assembled MnO2||Zn–LT@Zn full battery exhibits prominent rate performance (123 mA h g−1 at 2 A g−1) and long‐term cycling stability (80.4% capacity retention at 1 A g−1 after 700 cycles). Furthermore, the fabrication of this Zn‐LT@Zn anode can be extended to rolling method, reflecting the industrial manufacturing potential.

Ionic Liquid "Water Pocket" for Stable and Environment-Adaptable Aqueous Zinc Metal Batteries

The strong reactivity of water in aqueous electrolytes toward metallic zinc (Zn), especially at aggressive operating conditions, remains the fundamental obstacle to the commercialization of aqueous zinc metal batteries (AZMBs). Here, a water-immiscible ionic liquid diluent 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide (EmimFSI) is reported that can substantially suppress the water activity of aqueous electrolyte by serving as a "water pocket", enveloping the highly active H₂ O-dominated Zn²⁺ solvates and protecting them from parasitic reactions. During Zn deposition, the cation Emim⁺ and anion FSI^- function respectively in mitigating the tip effect and regulating the solid electrolyte interphase (SEI), thereby favoring a smooth Zn deposition layer protected by inorganic species-enriched SEI featuring high uniformity and stability. Combined with the boosted chemical/electrochemical stability endowed by the intrinsic merits of ionic liquid, this ionic liquid-incorporated aqueous electrolyte (IL-AE) enables the stable operation of Zn||Zn_0.25 V₂ O₅ ·nH₂ O cells even at a challenging temperature of 60 °C (>85% capacity retention over 400 cycles). Finally, as an incidental but practically valuable benefit, the near-zero vapor pressure nature of ionic liquid allows the efficient separation and recovery of high-value components from the spent electrolyte via a mild and green approach, promising the sustainable future of IL-AE in realizing practical AZMBs.

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

Poor thermodynamic stability and sluggish electrochemical kinetics of metallic Zn anode in aqueous solution greatly hamper its practical application. To solve such problems, to date, various zincophilic surface modification strategies are developed, which can facilitate reversible Zn plating/stripping behavior. However, there is still a lack of systematic and fundamental understanding regarding the metrics of thermodynamics inertia and kinetics zincophilia in selecting zincophilic sites. Herein, hetero-metallic interfaces are prioritized for the first time via optimizing different hetero metals (Fe, Co, Ni, Sn, Bi, Cu, Zn, etc.) and synthetic solvents (ethanol, ethylene glycol, n-propanol, etc.). Specifically, both theoretical simulations and experimental results suggest that this Bi@Zn interface can exhibit high efficiency owing to the thermodynamics inertia and kinetics zincophilia. A best practice for prioritizing zincophilic sites in a more practical metric is also proposed. As a proof of concept, the Bi@Zn anode delivers ultralow overpotential of ≈55 mV at a high rate of 10 mA cm^-2 and stable cycle life over 4700 cycles. The elaborated "thermodynamics inertia and kinetics metalphilia" metrics for hetero-metallic interfaces can benchmark the success of other metal-based batteries.

A Seamless Metal-Organic Framework Interphase with Boosted Zn2+ Flux and Deposition Kinetics for Long-Living Rechargeable Zn Batteries

Zn metal has received immense interest as a promising anode of rechargeable aqueous batteries for grid-scale energy storage. Nevertheless, the uncontrollable dendrite growth and surface parasitic reactions greatly retard its practical implementation. Herein, we demonstrate a seamless and multifunctional metal-organic framework (MOF) interphase for building corrosion-free and dendrite-free Zn anodes. The on-site coordinated MOF interphase with 3D open framework structure could function as a highly zincophilic mediator and ion sifter that synergistically induces fast and uniform Zn nucleation/deposition. In addition, the surface corrosion and hydrogen evolution are significantly suppressed by the interface shielding of the seamless interphase. An ultrastable Zn plating/stripping is achieved with elevated Coulombic efficiency of 99.2% over 1000 cycles and prolonged lifetime of 1100 h at 10 mA cm^-2 with a high cumulative plated capacity of 5.5 Ah cm^-2. Moreover, the modified Zn anode assures the MnO₂-based full cells with superior rate and cycling performance.

Rational Screening of Artificial Solid Electrolyte Interphases on Zn for Ultrahigh-Rate and Long-Life Aqueous Batteries

Solid electrolyte interphase (SEI) on Zn anodes plays a pivotal role for high-rate and long-life aqueous batteries, because it effectively inhibits side reactions and dendritic growth. Many materials are explored as SEIs by a trial-and-error approach. Herein, an exercisable way is proposed to screen the potential SEIs on Zn anodes in view of dendrite-suppressing ability and charge-transfer property theoretically. As an output of this screening, Zn₃ (BO₃ )₂ (ZBO) is checked experimentally. In symmetrical cells, Zn@ZBO runs over 250 h at an ultrahigh current density of 50 mA cm^-2 for a large areal capacity 10 mAh cm^-2 . In full cells, Zn@ZBO||MnO₂ shows an impressive cumulative capacity (≈406 mAh cm^-2 ) under harsh conditions, i.e., a lean electrolyte condition (10 µL mAh^-1 ), limited Zn supply (negative/positive electrode capacity ratio, N/P ratio = 2.3), and high areal capacity (5.0 mAh cm^-2 ). The significance of this work lies in not only the first report of ZBO on Zn showing excellent electrochemical performance, but also a feasible way to screen the promising SEI materials for other metal anodes.

Monolayer Thiol Engineered Covalent Interface toward Stable Zinc Metal Anode

Interface engineering of zinc metal anodes is a promising remedy to relieve their inferior stability caused by dendrite growth and side reactions. Nevertheless, the low affinity and additional weight of the protective coating remain obstacles to their further implementation. Here, aroused by DFT simulation, self-assembled monolayers (SAMs) are selectively constructed to enhance the stability of zinc metal anodes in dilute aqueous electrolytes. It is found that the monolayer thiol molecules relatively prefer to selectively graft onto the unstable zinc crystal facets through strong Zn-S chemical interactions to engineer a covalent interface, enabling the uniform deposition of Zn²⁺ onto (002) crystal facets. Therefore, dendrite-free anodes with suppressed side reactions can be achieved, proven by in situ optical visualization and differential electrochemical mass spectrometry (DEMS). In particular, the thiol endows the symmetric cells with a 4000 h ultrastable plating/stripping at a specific current density of 1.0 mA cm^-2, much superior to those of bare zinc anodes. Additionally, the full battery of modified anodes enables stable cycling of 87.2% capacity retention after 3300 cycles. By selectively capping unstable crystal facets with inert molecules, this work provides a promising design strategy at the molecular level for stable metal anodes.

Interface Reversible Electric Field Regulated by Amphoteric Charged Protein-Based Coating Toward High-Rate and Robust Zn Anode

Metallic interface engineering is a promising strategy to stabilize Zn anode via promoting Zn²⁺ uniform deposition. However, strong interactions between the coating and Zn²⁺ and sluggish transport of Zn²⁺ lead to high anodic polarization. Here, we present a bio-inspired silk fibroin (SF) coating with amphoteric charges to construct an interface reversible electric field, which manipulates the transfer kinetics of Zn²⁺ and reduces anodic polarization. The alternating positively and negatively charged surface as a build-in driving force can expedite and homogenize Zn²⁺ flux via the interplay between the charged coating and adsorbed ions, endowing the Zn-SF anode with low polarization voltage and stable plating/stripping. Experimental analyses with theoretical calculations suggest that SF can facilitate the desolvation of [Zn(H₂O)₆]²⁺ and provide nucleation sites for uniform deposition. Consequently, the Zn-SF anode delivers a high-rate performance with low voltage polarization (83 mV at 20 mA cm^-2) and excellent stability (1500 h at 1 mA cm^-2; 500 h at 10 mA cm^-2), realizing exceptional cumulative capacity of 2.5 Ah cm^-2. The full cell coupled with Zn_xV₂O₅·nH₂O (ZnVO) cathode achieves specific energy of ~ 270.5/150.6 Wh kg^-1 (at 0.5/10 A g^-1) with ~ 99.8% Coulombic efficiency and retains ~ 80.3% (at 5.0 A g^-1) after 3000 cycles.

A Dendrite-Free Zn Anode Co-modified with In and ZnF2 for Long-Life Zn-Ion Capacitors

Aqueous Zn (zinc) metal batteries have gotten a lot of interest and research because of their great volumetric capacity, low production cost, and high use safety. However, the coulombic efficiency of the Zn metal anode is low due to Zn dendrites formed during the charging and discharging processes of the battery, and the corrosion problem of the Zn anode in the electrolyte also reduces the battery's cycling stability and hinders its practical application. In this paper, InF₃ has been used to decorate the surface of Zn foil, and In (indium) and ZnF₂ coatings have been introduced to the surface of metal Zn simultaneously. After 1400 h of plating and stripping cycles, a symmetrical battery assembled from the modified Zn foil can still maintain a low voltage hysteresis of 30 mV. The Zn-ion capacitor assembled by the InF₃-modified Zn foil (Zn@In&ZnF₂) and activated carbon delivers an energy density of 33.5 Wh kg^-1 and a power density of 1608 W kg^-1 at a current density of 2 A g^-1 and can still maintain almost 100% capacity after 10,000 cycles. This work is helpful to improve the cycling stability and the corrosion problem of aqueous Zn-based batteries.

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.

A Self-Regulated Electrostatic Shielding Layer toward Dendrite-Free Zn Batteries

Although aqueous Zn batteries have become a more sustainable alternative to lithium-ion batteries owing to their intrinsic security, their practical applications are limited by dendrite formation and hydrogen reactions. The first application of a rare earth metal type addition to Zn batteries, cerium chloride (CeCl₃ ), as an effective, low-cost, and green electrolyte additive that facilitates the formation of a dynamic electrostatic shielding layer around the Zn protuberance to induce uniform Zn deposition is presented. After introducing CeCl₃ additives, the electrochemical characterizations, in situ optical microscopy observation, in situ differential electrochemical mass spectrometry, along with density functional theory calculations, and finite element method simulations reveal resisted Zn dendritic growth and enhanced electrolyte stability. As a result, the Zn-Zn cells using the CeCl₃ additive exhibit a long cycling stability of 2600 h at 2 mA cm^-2 , an impressive cumulative areal capacity of 3.6 Ah cm^-2 at 40 mA cm^-2 , and a high Coulombic efficiency of ≈99.7%. The fact that the Zn-LiFePO₄ cells with proposed electrolyte retain capacity significantly better than the additive-free case is even more exciting.

Stable Zinc Anodes Enabled by a Zincophilic Polyanionic Hydrogel Layer

The practical application of the Zn-metal anode for aqueous batteries is greatly restricted by catastrophic dendrite growth, intricate hydrogen evolution, and parasitic surface passivation. Herein, a polyanionic hydrogel film is introduced as a protective layer on the Zn anode with the assistance of a silane coupling agent (denoted as Zn-SHn). The hydrogel framework with zincophilic -SO₃ ^- functional groups uniformizes the zinc ions flux and transport. Furthermore, such a hydrogel layer chemically bonded on the Zn surface possesses an anti-catalysis effect, which effectively suppresses both the hydrogen evolution reaction and formation of Zn dendrites. As a result, stable and reversible Zn stripping/plating at various currents and capacities is achieved. A full cell by pairing the Zn-SHn anode with a NaV₃ O₈ ·1.5 H₂ O cathode shows a capacity of around 176 mAh g^-1 with a retention around 67% over 4000 cycles at 10 A g^-1 . This polyanionic hydrogel film protection strategy paves a new way for future Zn-anode design and safe aqueous batteries construction.

A Functional Organic Zinc-Chelate Formation with Nanoscaled Granular Structure Enabling Long-Term and Dendrite-Free Zn Anodes

Aqueous Zn metal batteries suffer from rapid cycling deterioration due to the severe water corrosion and dendrite growth on Zn anodes. Herein, a highly antiwater Zn_x-diethylenetriaminepenta(methylene-phosphonic acid) interface layer with good zinc affinity and special nanoscaled 3D granular structure is designed on Zn metal to address these problems. Experimental results combined with theoretical analysis and COMSOL simulations reveal that the hydrophobic groups in such Zn-based organic complex are the decisive factor in preventing H₂O from damaging Zn anode surface. The massive Zn²⁺ attractive sites formed by interaction of methylene-phosphonic acid groups and Zn cause ion channel for fast zinc-ion adsorption and migration. And the developed nano granular architecture on the surface induces redistributed Zn²⁺ ion flux to realize homogenization with smooth and compact surface deposition. Under the synergism, such modified anodes exhibit long cycling lifespan over 1300 h with a relatively low polarization voltage at 5 mA cm^-2. Also, the assembled full cells (including Zn//V₂O₅ and Zn//MnO₂ cell) based on this anode are also demonstrated. The work provides a simple, low cost, and efficient pathway by combining the two concepts of structural design and constructing protective layers on the surface to prepare high-performance Zn anodes toward prospering aqueous zinc-metal batteries.

Crystal Plane Reconstruction and Thin Protective Coatings Formation for Superior Stable Zn Anodes Cycling 1300 h

Some new insights into traditional metal pretreatment of anticorrosion for high stable Zn metal anodes are provided. A developed pretreatment methodology is employed to prefer the crystal plane of polycrystalline Zn and create 3.26 µm protective coatings mainly consisting of organic polymers and zinc salts on Zn foils (ROZ@Zn). In this process, Zn metal exhibits a surface-preferred (001) crystal plane proved by electron backscattered diffraction. Preferred (001) crystal planes and ROZ coatings can regulate Zn²⁺ diffusion, promote flat growth of Zn, and prevent side reactions. As a result, ROZ@Zn symmetrical cells exhibit superior plating/stripping performance over 1300 h. Impressively, it is significantly prolonged over 40 times in comparison to the bare Zn symmetric cell at 5 mA cm^-2 . Moreover, Zn//MnO₂  button cells have a high capacity retention of 96.3% after 1600 cycles and pouch cells have a high capacity 122 mAh g^-1  after 200 cycle at 5 C. This work provides inspiration for high stable aqueous Zn metal batteries using the developed metal pretreatment of anticorrosion, which will be a viable, low-cost, and efficient technology. More interesting, it demonstrates the availability of reconstructing crystal planes by the largely heterogeneous reaction activation of the different crystal planes to H⁺ .

In Situ Constructing Coordination Compounds Interphase to Stabilize Zn Metal Anode for High-Performance Aqueous Zn-SeS2 Batteries

Aqueous zinc (Zn) metal batteries have been regarded as the most promising aqueous batteries due to their low redox potential, high theoretical capacity, and abundant Zn resources. Unfortunately, Zn dendrite growth and serious side reactions drastically curtail the cycle life, severely affecting their large-scale application. Herein, a multifunctional ordered Zn-aminotrimethylene phosphonic acid (Zn-ATMP) film is in situ modified on the surface of metal Zn via a facile etching process. The modified layer can not only retard the side reactions and suppress the corrosion rate, but also lower the Zn nucleation overpotential and accelerate diffusion and homogenize deposition of Zn²⁺ due to the strong Zn affinity. Consequently, the as-prepared Zn-ATMP@Zn anode in the symmetric cell enables long-term lifespan (over 1000 h) at 10.0 mA cm^-2 with a high areal capacity of 5 mAh cm^-2 . Furthermore, when assembled with a SeS₂ -based cathode, a long lifespan for over 280 cycles at 2 C can be achieved for the aqueous Zn-SeS₂ battery. This work provides a reliable strategy for constructing stabilized Zn anode and accelerating the development of an aqueous energy storage system.

Protonating imine sites of polyaniline for aqueous zinc batteries

PANI materials usually contain a certain amount of insulating components, e.g., imine (N-) and amine (-NH-) groups, limiting the electrochemical redox of PANI. Herein, we proposed a simple protonation strategy to activate the redox couples of the PANI cathode for aqueous Zn batteries, during which the insulating N- groups are partially converted to the conductive emeraldine salt (polarons -NH⁺-), endowing PANI more active sites and enhanced conductivity. The A-PANI electrode realizes efficient transitions of leucoemeraldine/emeraldine and emeraldine/pernigraniline, achieving a high discharge capacity of 183 mA h g^-1, long life span, and good energy density of 178 W h kg^-1 at the power density of 680 W kg^-1. These values are significantly superior to those of the original PANI electrode, indicating the high efficiency of the proposed strategy. This simple protonation method could be applicable for many electrochemical devices, such as supercapacitors, sensors, and batteries.