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Designing a multifunctional separator with abundant ion migration paths is crucial for tuning the ion transport in rocking‐chair‐type batteries. Herein, a polydopamine‐functionalized PVDF (PVDF@PDA) nanofibrous membrane is designed to serve as a separator for aqueous zinc‐ion batteries (AZIBs). The functional groups (OH and NH) in PDA facilitate the formation of ZnO and ZnN coordination bonds with Zn ions, homogenizing the Zn‐ion flux and thus enabling dendrite‐free Zn deposition. Moreover, the PVDF@PDA separator effectively inhibits the shuttling of V‐species through the formation of VO coordination bonds. As a result, the Zn/NH4V4O10 battery with the PVDF@PDA separator exhibits enhanced cycling stability (92.3% after 1000 cycles at 5 A g−1) and rate capability compared to that using a glass fiber separator. This work provides a new avenue to design functionalized separators for high‐performance AZIBs. A polydopamine‐functionalized PVDF (PVDF@PDA) nanofibrous membrane is designed as a separator for aqueous zinc‐ion batteries. The PVDF@PDA separator homogenizes the Zn‐ion flux distribution to achieve the dendrite‐free Zn deposition via the metal‐PDA coordination chemistry. Moreover, the PVDF@PDA separator inhibits the shuttle of V‐species. Benefiting from the separator, the Zn/NH4V4O10 full cell retains 92.3% capacity after 1000 cycles at 5 A g−1.

Rational architecture design of the artificial protective layer on the zinc (Zn) anode surface is a promising strategy to achieve uniform Zn deposition and inhibit the uncontrolled growth of Zn dendrites. Herein, a red phosphorous‐derived artificial protective layer combined with a conductive N‐doped carbon framework is designed to achieve dendrite‐free Zn deposition. The Zn–phosphorus (ZnP) solid solution alloy artificial protective layer is formed during Zn plating. Meanwhile, the dynamic evolution mechanism of the ZnP on the Zn anode is successfully revealed. The concentration gradient of the electrolyte on the electrode surface can be redistributed by this protective layer, thereby achieving a uniform Zn‐ion flux. The fabricated Zn symmetrical battery delivers a dendrite‐free plating/stripping for 1100 h at the current density of 2.0 mA cm–2. Furthermore, aqueous Zn//MnO2 full cell exhibits a reversible capacity of 200 mAh g–1 after 350 cycles at 1.0 A g–1. This study suggests an effective solution for the suppression of Zn dendrites in Zn metal batteries, which is expected to provide a deep insight into the design of high‐performance rechargeable aqueous Zn‐ion batteries. An artificial protective layer based on zinc‐phosphorus (ZnP) alloying reaction is designed to regulate the deposition behavior of Zn ions. The synergistic effect of the ZnP alloy artificial protective layer and carbon framework enables a uniform electric field strength distribution and a homogeneous Zn‐ion flux on the electrode surface, which results in the dendrite‐free Zn plating/stripping.

Rechargeable aqueous zinc-ion batteries (ZIBs) have resurged in large-scale energy storage applications due to their intrinsic safety, affordability, competitive electrochemical performance, and environmental friendliness. Extensive efforts have been devoted to exploring high-performance cathodes and stable anodes. However, many fundamental issues still hinder the development of aqueous ZIBs. Here, we critically review and assess the energy storage chemistries of aqueous ZIBs for both cathodes and anodes. First, this review presents a comprehensive understanding of the cathode charge storage chemistry, probes the existing deficiencies in mechanism verification, and analyzes contradictions between the experimental results and proposed mechanisms. Then, a detailed summary of the representative cathode materials and corresponding comparative discussion is provided with typical cases encompassing structural features, electrochemical properties, existing drawbacks, and feasible remedies. Subsequently, the fundamental chemical properties, remaining challenges, and improvement strategies of both Zn metal and non-Zn anodes are presented to thoroughly explore the energy storage chemistry of ZIBs and pursue the development of high-performance ZIBs. Furthermore, the progress of mechanistic characterization techniques and theoretical simulation methods used for ZIBs is timely reviewed. Finally, we provide our perspectives, critical analysis, and insights on the remaining challenges and future directions for development of aqueous ZIBs. Graphical Abstract

Aqueous zinc‐ion batteries (ZIBs) have been intensively investigated as potential energy storage devices on account of their low cost, environmental benignity, and intrinsically safe merits. With the exploitation of high‐performance cathode materials, electrolyte systems, and in‐depth mechanism investigation, the electrochemical performances of ZIBs have been greatly enhanced. However, there are still some challenges that need to be overcome before its commercialization. Among them, the obstinate dendrites, corrosion, and hydrogen evolution reaction (HER) on Zn anodes are critical issues that severely limit the practical applications of ZIBs. To address these issues, various strategies have been proposed, and tremendous progress has been achieved in the past few years. In this article, we analyze the origins and effects of the dendrites, corrosion, and HER on Zn anodes in neutral and mildly acid aqueous solutions at first. And then, a scientific understanding of the fundamental design principles and strategies to suppress these problems are emphasized. Apart from these, this article also puts forward some requirements for the practical applications of Zn anodes as well as several cost‐effective‐modifying strategies. Finally, perspectives on the future development of Zn anodes in aqueous solutions are also briefly anticipated. This article provides pertinent insights into the challenges on anodes for the development of high‐performance ZIBs, which will greatly contribute to their practical applications. This article summarizes the causes and effects of Zn dendrites, corrosion, and hydrogen evolution reaction (HER) in aqueous zinc‐ion batteries (ZIBs). Moreover, recent advances in tackling these three issues toward zinc anode are systematically analyzed. Finally, several perspectives for the overall performance of zinc anodes have been put forward.

Zinc‐ion batteries (ZIBs) have been extensively investigated and discussed as promising energy storage devices in recent years owing to their low cost, high energy density, inherent safety, and low environmental impact. Nevertheless, several challenges remain that need to be prioritized before realizing the widespread application of ZIBs. In particular, the development of zinc anodes has been hindered by many challenges, such as inevitable zinc dendrites, corrosion passivation, and the hydrogen evolution reaction (HER), which have severely limited the practical application of high‐performance ZIBs. This review starts with a systematic discussion of the origins of zinc dendrites, corrosion passivation, and the HER, as well as their effects on battery performance. Subsequently, we discuss solutions to the above problems to protect the zinc anode, including the improvement of zinc anode materials, modification of the anode–electrolyte interface, and optimization of the electrolyte. In particular, this review emphasizes design strategies to protect zinc anodes from an integrated perspective with broad interest rather than a view with limited focus. In the final section, comments and perspectives are provided for the future design of high‐performance zinc anodes. A systematic and detailed summary of the research progress on zinc ion battery anodes is presented, including the causes of zinc dendrites, corrosion passivation and hydrogen evolution reaction on zinc anodes along with the existing strategies. Perspectives are provided for the future design of high‐performance zinc anodes.

Addition of organic compounds containing O/N heteroatoms to aqueous electrolytes such as ZnSO4 (ZS) solutions is one of the effective strategies to inhibit Zn anode dendrites and side reactions. However, addressing the stability of Zn plating/stripping at high current densities and areal capacities by this method is still a challenge, especially in capacitors known for high power and long life. Herein, an organic heterocyclic compound of 1, 4, 7, 10‐tetraazacyclododecane (TC) containing four symmetrically distributed N atoms is employed as ZS additive, expanding the life of Zn anodes from ≈ 30 h to 1000 and 240 h at deep plating/stripping conditions of 10 and 20 mA cm−2/mAh cm−2, respectively; the cumulative capacity is as high as 5.0 Ah cm−2 with 99% Coulombic efficiency, far exceeding reported additives. TC with higher binding energies than H2O for Zn species tends to adsorb to Zn (002) in a lying manner and participate in the solvation shell of Zn2+, thus avoiding Zn dendrites and side‐reaction damage, especially at high current densities. The TC‐endowed Zn anode's stability under such extreme conditions is verified in Zn‐ion capacitors (i.e., > 94.6% capacity retention after 28 000 cycles), providing new insights into the development of high‐power Zn‐based energy storage devices. An organic heterocyclic compound containing four symmetrically distributed N atoms has been proposed, which can substantially enhance the cycle life (up to 240–1000 h) of Zn anodes under deep plating/stripping conditions (10‐20 mA cm−2 and 10–20 mAh cm−2), along with high cumulative plated capacities of 2.4–5.0 Ah cm−2 and high Coulombic efficiency.

The need for large‐scale electrochemical energy storage devices in the future has spawned several new breeds of batteries in which aqueous zinc ion batteries (AZIBs) have attracted great attention due to their high safety, low cost, and excellent electrochemical performance. In the current research, the dendrite and corrosion caused by aqueous electrolytes are the main problems being studied. However, the research on the zinc metal anode is still in its infancy. We think it really needs to provide clear guidelines about how to reasonably configure the system of AZIBs to realize high‐energy density and long cycle life. Therefore, it is worth analyzing the works on the zinc anode, and several strategies are proposed to improve the stability and cycle life of the battery in recent years. Based on the crystal chemistry and interface chemistry, this review reveals the key factors and essential causes that inhibit dendrite growth and side reactions and puts forward the potential prospects for future work in this direction. It is foreseeable that guiding the construction of AZIBs with high‐energy density and long cycle life in various systems would be quite possible by following this overview as a roadmap. Based on the crystal chemistry and interface chemistry, we organize this review to look back and put forward the design around the substrate, electrolyte, and their interface. These key points mainly pay close attention to inhibit dendritic growth and side reactions, then present the potential prospects for future work in this direction. It is foreseeable that this overview as a roadmap could realize accurate control of homogeneous Zn deposition and guide the construction of zinc batteries with high performance and reversibility.

Aqueous zinc‐metal batteries (AZMBs) have received tremendous attentions due to their high safety, low cost, environmental friendliness, and simple process. However, zinc‐metal still suffer from uncontrollable dendrite growth and surface parasitic reactions that reduce the Coulombic efficiency (CE) and lifetime of AZMBs. These problems which are closely related to the active water are not well‐solved. Here, an ultrathin crack‐free metal–organic framework (ZIF‐7 x ‐8) with rigid sub‐nanopore (0.3 nm) is constructed on Zn‐metal to promote the de‐solvation of zinc‐ions before approaching Zn‐metal surface, reduce the contacting opportunity between water and Zn, and consequently eliminate water‐induced corrosion and side‐reactions. Due to the presence of rigid and ordered sub‐nanochannels, Zn‐ions deposits on Zn‐metal follow a highly ordered manner, resulting in a dendrite‐free Zn‐metal with negligible by‐products, which significantly improve the reversibility and lifespan of Zn‐metals. As a result, Zn‐metal protected by ultrathin crack‐free ZIF‐7 x ‐8 layer exhibits excellent cycling stability (over 2200 h) and extremely‐high 99.96% CE during 6000 cycles. The aqueous PANI‐V 2 O 5 //ZIF‐7 x ‐8@Zn full‐cell preserves 86% high‐capacity retention even after ultra‐long 2000 cycles. The practical pouch‐cell can also be cycled for more than 120 cycles. It is believed that the simple strategy demonstrated in this work can accelerate the practical utilizations of AZMBs.

Rechargeable aqueous zinc (Zn) ion batteries (AZIBs) using low-cost and safe Zn metal anodes are considered promising candidates for future grid-scale energy storage systems, but the Zn dendrite problem severely hinders the further prospects of AZIBs. Regulating Zn depositing behaviors toward horizontal alignment is highly effective and thus has received huge attention. However, such a strategy is usually based on previous substrate engineering, which requires complex preparation or expensive equipment. Therefore, it is essential to develop a novel solution that can realize horizontally aligned Zn flake deposition via easy operation and low cost. Herein, we report an ultrathin and robust Kevlar membrane as the interlayer to mechanically suppress Zn dendrite growth. Compared to the randomly distributed flaky dendrites in the control group, the deposited Zn sheets would grow into parallel alignment with the existence of such interlayer. As the dendrites are effectively suppressed, Zn∥Cu asymmetric, Zn∥Zn symmetric, and Zn∥MnO 2 full batteries using Kevlar interlayer deliver significantly improved cycling stabilities. Furthermore, the Zn∥MnO 2 pouch cell using a Kevlar interlayer delivers stable cycling performance and shows stable operation during multi-angle folding. We believe this work provides a new possibility for regulating Zn deposition from a crystallographic perspective.

Aqueous rechargeable Zn-ion batteries are regarded as a promising alternative to lithium-ion batteries owing to their high energy density, low cost, and high safety. However, their commercialization is severely restricted by the Zn dendrite formation and side reactions. Herein, we propose that these issues can be minimized by modifying the interfacial properties through introducing electrochemically inert Al 2 O 3 nanocoatings on Zn meal anodes (Al 2 O 3 @Zn). The Al 2 O 3 nanocoatings can effectively suppress both the dendrite growth and side reactions. As a result, the Al 2 O 3 @Zn symmetric cells show excellent electrochemical performance with a long lifespan of more than 4,000 h at 1 mA·cm −2 and 1 mAh·cm −2 . Meanwhile, the assembled Al 2 O 3 @Zn//V 2 O 5 full cells can deliver a high capacity (236.2 mAh·g −1 ) and long lifespan with a capacity retention of 76.11% after 1,000 cycles at 4 A·g −1 .