Novel 3D Nanoporous Zn–Cu Alloy as Long‐Life Anode toward High‐Voltage Double Electrolyte Aqueous Zinc‐Ion Batteries

The recharge ability of zinc metal‐based aqueous batteries is greatly limited by the zinc anode. The poor cycling durability of Zn anodes is attributed to the dendrite growth, shape change and passivation, but this issue has been ignored by using an excessive amount of Zn in the past. Herein, a 3D nanoporous (3D NP) Zn–Cu alloy is fabricated by a sample electrochemical‐assisted annealing thermal method combined, which can be used directly as self‐supported electrodes applied for renewable zinc‐ion devices. The 3D NP architectures electrode offers high electron and ion transport paths and increased material loading per unit substrate area, which can uniformly deposit/strip Zn and improve charge storage ability. Benefiting from the intrinsic materials and architectures features, the 3D NP Zn–Cu alloy anode exhibits high areal capacity and excellent cycling stability. Further, the fabricated high‐voltage double electrolyte aqueous Zn–Br₂ battery can deliver maximum areal specific capacity of ≈1.56 mAh cm^?2, which is close to the level of typical commercial Li‐ion batteries. The excellent performance makes it an ideal candidate for next‐generation aqueous zinc‐ion batteries.     

Recent Progress in Electrically Rechargeable Zinc–Air Batteries

Over the past decade, the surging interest for higher‐energy‐density, cheaper, and safer battery technology has spurred tremendous research efforts in the development of improved rechargeable zinc–air batteries. Current zinc–air batteries suffer from poor energy efficiency and cycle life, owing mainly to the poor rechargeability of zinc and air electrodes. To achieve high utilization and cyclability in the zinc anode, construction of conductive porous framework through elegant optimization strategies and adaptation of alternate active material are employed. Equally, there is a need to design new and improved bifunctional oxygen catalysts with high activity and stability to increase battery energy efficiency and lifetime. Efforts to engineer catalyst materials to increase the reactivity and/or number of bifunctional active sites are effective for improving air electrode performance. Here, recent key advances in material development for rechargeable zinc–air batteries are described. By improving fundamental understanding of materials properties relevant to the rechargeable zinc and air electrodes, zinc–air batteries will be able to make a significant impact on the future energy storage for electric vehicle application. To conclude, a brief discussion on noteworthy concepts of advanced electrode and electrolyte systems that are beyond the current state‐of‐the‐art zinc–air battery chemistry, is presented.     

Layered Ca0.28MnO2·0.5H2O as a High Performance Cathode for Aqueous Zinc‐Ion Battery

Aqueous zinc‐ion batteries are promising candidates for grid‐scale energy storage because of their intrinsic safety, low cost, and high energy intensity. However, lack of suitable cathode materials with both excellent rate performance and cycling stability hinders further practical application of aqueous zinc‐ion batteries. Here, a nanoflake‐self‐assembled nanorod structure of Ca_0.28MnO₂·0.5H₂O as Zn‐insertion cathode material is designed. The Ca_0.28MnO₂·0.5H₂O exhibits a reversible capacity of 298 mAh g^?1 at 175 mA g^?1 and long‐term cycling stability over 5000 cycles with no obvious capacity fading, which indicates that the per‐insertion of Ca ions and water can significantly improve reversible insertion/extraction stability of Zn²⁺ in Mn‐based layered type material. Further, its charge storage mechanism, especially hydrogen ions, is elucidated. A comprehensive study suggests that the intercalation of hydrogen ions in the first discharge plat is controled by both pH value and type of anion of electrolyte. Further, it can stabilize the Ca_0.28MnO₂·0.5H₂O cathode and facilitate the following insertion of Zn²⁺ in 1 m ZnSO₄/0.1 m MnSO₄ electrolyte. This work can enlighten and promote the development of high‐performance rechargeable aqueous zinc‐ion batteries.     

Recent Progress in Multivalent Metal (Mg,Zn, Ca,and Al) and Metal‐Ion Rechargeable Batteries with Organic Materials as Promising Electrodes

The emerging demand for electronic and transportation technologies has driven the development of rechargeable batteries with enhanced capacity storage. Especially, multivalent metal (Mg, Zn, Ca, and Al) and metal‐ion batteries have recently attracted considerable interests as promising substitutes for future large‐scale energy storage devices, due to their natural abundance and multielectron redox capability. These metals are compatible with nonflammable aqueous electrolytes and are less reactive when exposed in ambient atmosphere as compared with Li metals, hence enabling potential safer battery systems. Luckily, green and sustainable organic compounds could be designed and tailored as universal host materials to accommodate multivalent metal ions. Considering these advantages, effective approaches toward achieving organic multivalent metal and metal‐ion rechargeable batteries are highlighted in this Review. Moreover, organic structures, cell configurations, and key relevant electrochemical parameters are presented. Hopefully, this Review will provide a fundamental guidance for future development of organic‐based multivalent metal and metal‐ion rechargeable batteries.     

Advanced Filter Membrane Separator for Aqueous Zinc‐Ion Batteries

Aqueous zinc‐ion batteries with low cost and inherent safety are considered to be the next‐generation energy storage device. However, they suffer from poor cycling stability and low coulombic efficiency caused by the serious zinc dendrites during the cycling. In this work, a porous water‐based filter membrane is first proposed as separator due to its good toughness and uniform pore distribution. The results demonstrate that the symmetrical cell using a filter membrane can cycle over 2600 h with a low voltage hysteresis of 47 mV. Moreover, an aqueous Zn//NaV₃O₈·1.5H₂O cell based on the filter membrane is constructed, which demonstrates a high capacity retention of 83.8% after 5000 cycles at 5 A g^?1. The mechanism research results reveal that the excellent dendrites inhibiting the ability of the filter membrane should be attributed to its uniform pore distribution rather than its composition. This work proposes a filter membrane separator and reveals the great influence of separator on the zinc stripping/plating process, which will shed light on the development of high‐performance aqueous zinc‐ion batteries.     

Unlocking the Potential of Disordered Rocksalts for Aqueous Zinc‐Ion Batteries

Owing to the intense charge repulsion of multivalent ions and intrinsic slugggish kenetics, vast and fast storage of zinc ions into electrode materials has remained unattainable. Here, an efficient strategy to unlock the electrochemical activity of rocksalt vanadium oxynitride is developed via the substitution of low‐valent oxygen for high‐valent nitrogen, forming disordered rocksalt with abundant vacancies/defects due to the charge‐compensating function. Unexpectedly, the disordered rocksalt not only provides plentiful active sites for zinc ions but is also beneficial for the rapid diffusion of zinc ions, owing to the large presence of vacancies/defects in the matrix. Hence, a very high reversible capacity (603 mAh g^?1, 0.2C) and high rate capability (124 mAh g^?1at 600C) are achieved for zinc storage. This should open a new and efficient avenue for the design of electrode materials with both high energy and power densities for aqueous zinc‐ion batteries.     

Joint Charge Storage for High‐Rate Aqueous Zinc–Manganese Dioxide Batteries

Aqueous rechargeable zinc–manganese dioxide batteries show great promise for large‐scale energy storage due to their use of environmentally friendly, abundant, and rechargeable Zn metal anodes and MnO₂ cathodes. In the literature various intercalation and conversion reaction mechanisms in MnO₂ have been reported, but it is not clear how these mechanisms can be simultaneously manipulated to improve the charge storage and transport properties. A systematical study to understand the charge storage mechanisms in a layered δ‐MnO₂ cathode is reported. An electrolyte‐dependent reaction mechanism in δ‐MnO₂ is identified. Nondiffusion controlled Zn²⁺ intercalation in bulky δ‐MnO₂ and control of H⁺ conversion reaction pathways over a wide C‐rate charge–discharge range facilitate high rate performance of the δ‐MnO₂ cathode without sacrificing the energy density in optimal electrolytes. The Zn‐δ‐MnO₂ system delivers a discharge capacity of 136.9 mAh g^?1 at 20 C and capacity retention of 93% over 4000 cycles with this joint charge storage mechanism. This study opens a new gateway for the design of high‐rate electrode materials by manipulating the effective redox reactions in electrode materials for rechargeable batteries.     

水系锌离子电池的研究进展

锌离子电池是近年来发展起来的一种新型二次水系电池, 具有高能量密度、高功率密度、放电过程高效安全、电池材料无毒廉价、制备工艺简单等优点, 在大型储能等领域具有很高应用价值和发展前景。本文综述了水系锌离子电池的研究进展, 对金属锌作负极的优点和面临的处理问题进行总结, 对已报导的正极材料中锌离子电池的电化学性能和反应机制进行分析, 并通过分析目前多价离子的脱嵌特性对锌离子电池正极材料的发展进行预测。     

A High‐Energy and Long‐Life Aqueous Zn/Birnessite Battery via Reversible Water and Zn2+ Coinsertion

Aqueous rechargeable Zn/birnessite batteries have recently attracted extensive attention for energy storage system because of their low cost and high safety. However, the reaction mechanism of the birnessite cathode in aqueous electrolytes and the cathode structure degradation mechanics still remain elusive and controversial. In this work, it is found that solvation water molecules coordinated to Zn²⁺ are coinserted into birnessite lattice structure contributing to Zn²⁺ diffusion. However, the birnessite will suffer from hydroxylation and Mn dissolution with too much solvated water coinsertion. Through engineering Zn²⁺ primary solvation sheath with strong‐field ligand in aqueous electrolyte, highly reversible [Zn(H₂O)₂]²⁺ complex intercalation/extraction into/from birnessite cathode is obtained. Cathode–electrolyte interface suppressing the Mn dissolution also forms. The Zn metal anode also shows high reversibility without formation of “death‐zinc” and detrimental dendrite. A full cell coupled with birnessite cathode and Zn metal anode delivers a discharge capacity of 270 mAh g^?1, a high energy density of 280 Wh kg^?1 (based on total mass of cathode and anode active materials), and capacity retention of 90% over 5000 cycles.     

H+‐Insertion Boosted α‐MnO2 for an Aqueous Zn‐Ion Battery

Rechargeable Zn/MnO₂ batteries using mild aqueous electrolytes are attracting extensive attention due to their low cost, high safety, and environmental friendliness. However, the charge‐storage mechanism involved remains a topic of controversy so far. Also, the practical energy density and cycling stability are still major issues for their applications. Herein, a free‐standing α‐MnO₂ cathode for aqueous zinc‐ion batteries (ZIBs) is directly constructed with ultralong nanowires, leading to a rather high energy density of 384 mWh g^?1 for the entire electrode. Greatly, the H⁺/Zn²⁺ coinsertion mechanism of α‐MnO₂ cathode for aqueous ZIBs is confirmed by a combined analysis of in situ X‐ray diffractometry, ex situ transmission electron microscopy, and electrochemical methods. More interestingly, the Zn²⁺‐insertion is found to be less reversible than H⁺‐insertion in view of the dramatic capacity fading occurring in the Zn²⁺‐insertion step, which is further evidenced by the discovery of an irreversible ZnMn₂O₄ layer at the surface of α‐MnO₂. Hence, the H⁺‐insertion process actually plays a crucial role in maintaining the cycling performance of the aqueous Zn/α‐MnO₂ battery. This work is believed to provide an insight into the charge‐storage mechanism of α‐MnO₂ in aqueous systems and paves the way for designing aqueous ZIBs with high energy density and long‐term cycling ability.     

Recent Advances toward the Rational Design of Efficient Bifunctional Air Electrodes for Rechargeable Zn–Air Batteries

Large‐scale application of renewable energy and rapid development of electric vehicles have brought unprecedented demand for advanced energy‐storage/conversion technologies and equipment. Rechargeable zinc (Zn)–air batteries represent one of the most promising candidates because of their high energy density, safety, environmental friendliness, and low cost. The air electrode plays a key role in managing the many complex physical and chemical processes occurring on it to achieve high performance of Zn–air batteries. Herein, recent advances of air electrodes from bifunctional catalysts to architectures are summarized, and their advantages and disadvantages are discussed to underline the importance of progress in the evolution of bifunctional air electrodes. Finally, some challenges and the direction of future research are provided for the optimized design of bifunctional air electrodes to achieve high performance of rechargeable Zn–air batteries.     

Ultrafast Zn2+ Intercalation and Deintercalation in Vanadium Dioxide

Although rechargeable aqueous zinc‐ion batteries have attracted extensive interest due to their environmental friendliness and low cost, they still lack suitable cathodes with high rate capabilities, which are hampered by the intense charge repulsion of bivalent Zn²⁺. Here, a novel intercalation pseudocapacitance behavior and ultrafast kinetics of Zn²⁺ into the unique tunnels of VO₂ (B) nanofibers in aqueous electrolyte are demonstrated via in situ X‐ray diffraction and various electrochemical measurements. Because VO₂ (B) nanofibers possess unique tunnel transport pathways with big sizes (0.82 and 0.5 nm² along the b‐ and c‐axes) and little structural change on Zn²⁺ intercalation, the limitation from solid‐state diffusion in the vanadium dioxide electrode is eliminated. Thus, VO₂ (B) nanofibers exhibit a high reversible capacity of 357 mAh g^?1, excellent rate capability (171 mAh g^?1 at 300 C), and high energy and power densities as applied for zinc‐ion storage.     

Atomic‐Scale Structure Evolution in a Quasi‐Equilibrated Electrochemical Process of Electrode Materials for Rechargeable Batteries

Lithium‐ion batteries have proven to be extremely attractive candidates for applications in portable electronics, electric vehicles, and smart grid in terms of energy density, power density, and service life. Further performance optimization to satisfy ever‐increasing demands on energy storage of such applications is highly desired. In most of cases, the kinetics and stability of electrode materials are strongly correlated to the transport and storage behaviors of lithium ions in the lattice of the host. Therefore, information about structural evolution of electrode materials at an atomic scale is always helpful to explain the electrochemical performances of batteries at a macroscale. The annular‐bright‐field (ABF) imaging in aberration‐corrected scanning transmission electron microscopy (STEM) allows simultaneous imaging of light and heavy elements, providing an unprecedented opportunity to probe the nearly equilibrated local structure of electrode materials after electrochemical cycling at atomic resolution. Recent progress toward unraveling the atomic‐scale structure of selected electrode materials with different charge and/or discharge state to extend the current understanding of electrochemical reaction mechanism with the ABF and high angle annular dark field STEM imaging is presented here. Future research on the relationship between atomic‐level structure evolution and microscopic reaction mechanisms of electrode materials for rechargeable batteries is envisaged.     

Composite‐Structure Material Design for High‐Energy Lithium Storage

High‐energy storage devices are in demand for the rapid development of modern society. Until now, many kinds of energy storage devices, such as lithium‐ion batteries (LIBs), sodium‐ion batteries (NIBs), and so on, have been developed in the past 30 years. However, most of the commercially exploited and studied active electrode materials of these energy storage devices possess a single phase with low reversible capacity or unsatisfied cycle stability. Continuous and extensive research efforts are made to develop alternative materials with a higher specific energy density and long cycle life by element doping or surface modification. A novel strategy of forming composite‐structure electrode materials by introducing structure units has attracted great attention in recent years. Herein, based on previous publications on these composite‐structure materials, some important scientific points focusing on the design of composite‐structure materials for better electrochemical performances reveal the distinction of composite structures based on average and local structure analysis methods, and an understanding of the relationship between these interior composite structures and their electrochemical performances is discussed thoroughly. The lithiation/delithiation mechanism and the remaining challenges and perspectives for composite‐structure electrode materials are also elaborated.     

Electrically Rechargeable Zinc–Air Batteries: Progress,Challenges, and Perspectives

Zinc–air batteries have attracted much attention and received revived research efforts recently due to their high energy density, which makes them a promising candidate for emerging mobile and electronic applications. Besides their high energy density, they also demonstrate other desirable characteristics, such as abundant raw materials, environmental friendliness, safety, and low cost. Here, the reaction mechanism of electrically rechargeable zinc–air batteries is discussed, different battery configurations are compared, and an in depth discussion is offered of the major issues that affect individual cellular components, along with respective strategies to alleviate these issues to enhance battery performance. Additionally, a section dedicated to battery‐testing techniques and corresponding recommendations for best practices are included. Finally, a general perspective on the current limitations, recent application‐targeted developments, and recommended future research directions to prolong the lifespan of electrically rechargeable zinc–air batteries is provided.     

High‐Performance Aqueous Zinc–Ion Battery Based on Layered H2V3O8 Nanowire Cathode

Rechargeable aqueous zinc–ion batteries have offered an alternative for large‐scale energy storage owing to their low cost and material abundance. However, developing suitable cathode materials with excellent performance remains great challenges, resulting from the high polarization of zinc ion. In this work, an aqueous zinc–ion battery is designed and constructed based on H₂V₃O₈ nanowire cathode, Zn(CF₃SO₃)₂ aqueous electrolyte, and zinc anode, which exhibits the capacity of 423.8 mA h g⁻¹ at 0.1 A g⁻¹, and excellent cycling stability with a capacity retention of 94.3% over 1000 cycles. The remarkable electrochemical performance is attributed to the layered structure of H₂V₃O₈ with large interlayer spacing, which enables the intercalation/de‐intercalation of zinc ions with a slight change of the structure. The results demonstrate that exploration of the materials with large interlayer spacing is an effective strategy for improving electrochemical stability of electrodes for aqueous Zn ion batteries.     

锌离子电容器正极材料研究进展

作为新型储能设备,水系锌离子电容器具有高功率密度、大能量密度、长循环寿命和高安全性等优异性能,在民用电子设备和军用电气化武器装备领域具有极高的应用前景,有望成为代替锂离子电池的新一代储能方案。本文系统梳理了活性炭正极材料、碳纳米管正极材料、石墨烯正极材料和生物质碳正极材料等碳基正极材料的储锌能力,总结了MXene正极材料在锌离子电容器领域的研究进展,归纳了过渡金属氧化物正极材料的锌离子储存性能,指出开发高容量、耐高压、耐低温正极材料的必要性与紧迫性。     

Recent Progress in Iron‐Based Electrode Materials for Grid‐Scale Sodium‐Ion Batteries

Grid‐scale energy storage batteries with electrode materials made from low‐cost, earth‐abundant elements are needed to meet the requirements of sustainable energy systems. Sodium‐ion batteries (SIBs) with iron‐based electrodes offer an attractive combination of low cost, plentiful structural diversity and high stability, making them ideal candidates for grid‐scale energy storage systems. Although various iron‐based cathode and anode materials have been synthesized and evaluated for sodium storage, further improvements are still required in terms of energy/power density and long cyclic stability for commercialization. In this Review, progress in iron‐based electrode materials for SIBs, including oxides, polyanions, ferrocyanides, and sulfides, is briefly summarized. In addition, the reaction mechanisms, electrochemical performance enhancements, structure–composition–performance relationships, merits and drawbacks of iron‐based electrode materials for SIBs are discussed. Such iron‐based electrode materials will be competitive and attractive electrodes for next‐generation energy storage devices.     

Langmuir–Blodgett Nanowire Devices for In Situ Probing of Zinc‐Ion Batteries

In situ monitoring the evolution of electrode materials in micro/nano scale is crucial to understand the intrinsic mechanism of rechargeable batteries. Here a novel on‐chip Langmuir–Blodgett nanowire (LBNW) microdevice is designed based on aligned and assembled MnO₂ nanowire quasimonolayer films for directly probing Zn‐ion batteries (ZIBs) in real‐time. With an interdigital device configuration, a splendid Ohmic contact between MnO₂ LBNWs and pyrolytic carbon current collector is demonstrated here, enabling a small polarization voltage. In addition, this work reveals, for the first time, that the conductance of MnO₂ LBNWs monotonically increases/decreases when the ZIBs are charged/discharged. Multistep phase transition is mainly responsible for the mechanism of the ZIBs, as evidenced by combined high‐resolution transmission electron microscopy and in situ Raman spectroscopy. This work provides a new and adaptable platform for microchip‐based in situ simultaneous electrochemical and physical detection of batteries, which would promote the fundamental and practical research of nanowire electrode materials in energy storage applications.     

A Corrosion‐Resistant and Dendrite‐Free Zinc Metal Anode in Aqueous Systems

Rechargeable aqueous zinc (Zn) ion‐based energy storage systems have been reviving recently because of their low cost and high safety merits; however, they still suffer from the problems of corrosion and dendrite growth on Zn metal anodes that cause gas generation and early battery failure. Unfortunately, the corrosion problem has not received sufficient attention until now. Here, it is pioneeringly demonstrated that decorating the Zn surface with a dual‐functional metallic indium (In) layer, acting as both a corrosion inhibitor and a nucleating agent, is a facile but effective strategy to suppress both drastic corrosion and dendrite growth. Symmetric cells assembled with the treated Zn electrodes can sustain up to 1500 h of plating/stripping cycles with an ultralow voltage hysteresis (54 mV), and a 5000 cycle‐life is achieved for a prototype full cell. This work will instigate the further development of aqueous metal‐based energy storage systems.