Recent Advances in Vanadium‐Based Aqueous Rechargeable Zinc‐Ion Batteries

Aqueous zinc‐ion batteries (AZIBs) have attracted considerable attention as promising next‐generation power sources because of the abundance, low cost, eco‐friendliness, and high security of Zn resources. Recently, vanadium‐based materials as cathodes in AZIBs have gained interest owing to their rich electrochemical interaction with Zn²⁺ and high theoretical capacity. However, existing AZIBs are still far from meeting commercial requirements. This article summarizes recent advances in the rational design of vanadium‐based materials toward AZIBs. In particular, it highlights various tactics that have been reported to increase the intercalation space, structural stability, and the diffusion ability of the guest Zn²⁺, as well as explores the structure‐dependent electrochemical performance and the corresponding energy storage mechanism. Furthermore, this article summarizes recent achievements in the optimization of aqueous electrolytes and Zn anodes to resolve the issues that remain with Zn anodes, including dendrite formation, passivation, corrosion, and the low coulombic efficiency of plating/stripping. The rationalization of these research findings can guide further investigations in the design of cathode/anode materials and electrolytes for next‐generation AZIBs.     

Electrolytes and Interphases in Sodium‐Based Rechargeable Batteries: Recent Advances and Perspectives

For sodium (Na)‐rechargeable batteries to compete, and go beyond the currently prevailing Li‐ion technologies, mastering the chemistry and accompanying phenomena is of supreme importance. Among the crucial components of the battery system, the electrolyte, which bridges the highly polarized positive and negative electrode materials, is arguably the most critical and indispensable of all. The electrolyte dictates the interfacial chemistry of the battery and the overall performance, having an influence over the practical capacity, rate capability (power), chemical/thermal stress (safety), and lifetime. In‐depth knowledge of electrolyte properties provides invaluable information to improve the design, assembly, and operation of the battery. Thus, the full‐scale appraisal of both tailored electrolytes and the concomitant interphases generated at the electrodes need to be prioritized. The deployment of large‐format Na‐based rechargeable batteries also necessitates systematic evaluation and detailed appraisal of the safety‐related hazards of Na‐based batteries. Hence, this review presents a comprehensive account of the progress, status, and prospect of various Na⁺‐ion electrolytes, including solvents, salts and additives, their interphases and potential hazards.     

Defect Engineering in Manganese‐Based Oxides for Aqueous Rechargeable Zinc‐Ion Batteries: A Review

The development of advanced cathode materials for aqueous the zinc ion battery (ZIB) represents a crucial step toward building future large‐scale green energy conversion and storage systems. Recently, significant progress has been achieved in the development of manganese‐based oxides for ZIB via defect engineering, whereby the intrinsic capacity and energy density have been enhanced. In this review, an overview of the recent progress in the defect engineering of manganese‐based oxides for aqueous ZIBs is summarized in the following order: 1) the structures and properties of the commonly used manganese‐based oxides, 2) the classification of the various types of defect engineering commonly reported, 3) the various strategies used to create defects in materials, and 4) the effects of the various types of defect engineering on the electrochemical performance of manganese‐based oxides. Finally, a perspective on the defect engineering of manganese‐based oxides is proposed to further enhance their electrochemical performance as a ZIB cathode.     

A Room‐Temperature Molten Hydrate Electrolyte for Rechargeable Zinc–Air Batteries

Aqueous Zn‐based batteries are attracting extensive interest because of their economic feasibility and potentially high energy density. However, poor rechargeability of Zn anode in conventional electrolytes resulting from dendrite formation and self‐corrosion hinders their practical implementation. Herein, a Zn molten hydrate composed of inorganic Zn salt and water is demonstrated as an advantageous electrolyte for solving these issues. In this electrolyte, dendrite‐free Zn deposition/dissolution reaction with a high Coulombic efficiency (≈99%) as well as long‐term stability, free from CO₂ poisoning are realized. The resultant Zn–air cell exhibits a reversible capacity of 1000 mAh g_(catalyst)^?1 over 100 cycles at 30 °C. Combined with the intrinsic safety associated with aqueous chemistry and cost benefit of the raw material, the present Zn–air battery makes a strong candidate for large‐scale energy storage.     

An Areal‐Energy Standard to Validate Air‐Breathing Electrodes for Rechargeable Zinc–Air Batteries

Rechargeable zinc–air batteries may become safe, sustainable, low‐cost, and energy‐dense alternatives to Li‐ion batteries for many applications, but problems associated with today's air‐breathing electrodes limit zinc–air performance. To overcome this challenge, researchers have investigated hundreds of air‐breathing electrode variations over the last decade. Unfortunately, the efficacy of these variations remains ambiguous due to nonstandardized cycling protocols that map to areal‐energy values spanning five orders of magnitude. To compete with Li‐ion batteries, researchers should cycle zinc–air cells at 35 mWh cm_geo^?2, but only 8, of the 100 publications reviewed here, breach this threshold. Once the community cycles zinc–air cells at the proposed areal energy and better understands failure mechanisms, lab‐scale results will translate to practical advancements.     

Recent Advances in Rechargeable Magnesium‐Based Batteries for High‐Efficiency Energy Storage

Benefiting from higher volumetric capacity, environmental friendliness and metallic dendrite‐free magnesium (Mg) anodes, rechargeable magnesium batteries (RMBs) are of great importance to the development of energy storage technology beyond lithium‐ion batteries (LIBs). However, their practical applications are still limited by the absence of suitable electrode materials, the sluggish kinetics of Mg²⁺ insertion/extraction and incompatibilities between electrodes and electrolytes. Herein, a systematic and insightful review of recent advances in RMBs, including intercalation‐based cathode materials and conversion reaction‐based compounds is presented. The relationship between microstructures with their electrochemical performances is comprehensively elucidated. In particular, anode materials are discussed beyond metallic Mg for RMBs. Furthermore, other Mg‐based battery systems are also summarized, including Mg–air batteries, Mg–sulfur batteries, and Mg–iodine batteries. This review provides a comprehensive understanding of Mg‐based energy storage technology and could offer new strategies for designing high‐performance rechargeable magnesium batteries.     

Sandwich‐Like Reduced Graphene Oxide/Carbon Black/Amorphous Cobalt Borate Nanocomposites as Bifunctional Cathode Electrocatalyst in Rechargeable Zinc‐Air Batteries

The inhibitively high cost of the noble‐metal‐containing materials has become a major obstacle for the large‐scale application of rechargeable zinc‐air batteries (ZABs). To solve this problem in a practical way, a green and scalable method to prepare sandwich‐like reduced graphene oxide /carbon black/amorphous cobalt borate nanocomposites (rGO/CB/Co‐B_i) is reported. These composites are shown to be a highly efficient and robust bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this system, the spontaneous assembly of the GO sheet and CB nanoparticles is demonstrated by noncovalent interactions to build the sandwich‐like structure with hierarchical pore distribution. The impressive ORR and OER activities of the obtained nanocomposite are attributed to the high conductivity, large surface area, and the hierarchically porous channels. With room‐temperature synthesis and significant activities shown in the demonstrative battery test, the prepared nanocomposite can potentially serve as an alternative for noble‐metal‐based rechargeable ZAB cathode materials.     

Strategies for Dendrite‐Free Anode in Aqueous Rechargeable Zinc Ion Batteries

Ongoing interest is focused on aqueous zinc ion batteries (ZIBs) for mass‐production energy storage systems as a result of their affordability, safety, and high energy density. Ensuring the stability of the electrode/electrolyte interface is of particular importance for prolonging the cycling ability to meet the practical requirements of rechargeable batteries. Zinc anodes exhibit poor cycle life and low coulombic efficiency, stemming from the severe dendrite growth, and irreversible byproducts such as H₂ and inactive ZnO. Great efforts have recently been devoted to zinc anode protection for designing high‐performance ZIBs. However, the intrinsic origins of zinc plating/striping are poorly understood, which greatly delay its potential applications. Rather than focusing on battery metrics, this review delves deeply into the underlying science that triggers the deposition/dissolution of zinc ions. Furthermore, recent advances in modulating the zinc coordination environment, uniforming interfacial electric fields, and inducing zinc deposition are highlighted and summarized. Finally, perspectives and suggestions are provided for designing highly stable zinc anodes for the industrialization of the aqueous rechargeable ZIBs in the near future.     

Hierarchical Structures Based on Two‐Dimensional Nanomaterials for Rechargeable Lithium Batteries

Two‐dimensional (2D) nanomaterials (i.e., graphene and its derivatives, transition metal oxides and transition metal dichalcogenides) are receiving a lot attention in energy storage application because of their unprecedented properties and great diversities. However, their re‐stacking or aggregation during the electrode fabrication process has greatly hindered their further developments and applications in rechargeable lithium batteries. Recently, rationally designed hierarchical structures based on 2D nanomaterials have emerged as promising candidates in rechargeable lithium battery applications. Numerous synthetic strategies have been developed to obtain hierarchical structures and high‐performance energy storage devices based on these hierarchical structure have been realized. This review summarizes the synthesis and characteristics of three styles of hierarchical architecture, namely three‐dimensional (3D) porous network nanostructures, hollow nanostructures and self‐supported nanoarrays, presents the representative applications of hierarchical structured nanomaterials as functional materials for lithium ion batteries, lithium‐sulfur batteries and lithium‐oxygen batteries, meanwhile sheds light particularly on the relationship between structure engineering and improved electrochemical performance; and provides the existing challenges and the perspectives for this fast emerging field.     

Covalent–Organic Frameworks: Advanced Organic Electrode Materials for Rechargeable Batteries

Covalent–organic frameworks (COFs), featuring structural diversity, framework tunability and functional versatility, have emerged as promising organic electrode materials for rechargeable batteries and garnered tremendous attention in recent years. The adjustable pore configuration, coupled with the functionalization of frameworks through pre‐ and post‐synthesis strategies, enables a precise customization of COFs, which provides a novel perspective to deepen the understanding of the fundamental problems of organic electrode materials. In this review, a summary of the recent research into COFs electrode materials for rechargeable batteries including lithium‐ion batteries, sodium‐ion batteries, potassium‐ion batteries, and aqueous zinc batteries is provided. In addition, this review will also cover the working principles, advantages and challenges, strategies to improve electrochemical performance, and applications of COFs in rechargeable batteries.     

Advanced Organic Electrode Materials for Rechargeable Sodium‐Ion Batteries

Benefiting from the high abundance and low cost of sodium resource, rechargeable sodium‐ion batteries (SIBs) are regarded as promising candidates for large‐scale electrochemical energy storage and conversion. Due to the heavier mass and larger radius of Na⁺ than that of Li⁺, SIBs with inorganic electrode materials are currently plagued with low capacity and insufficient cycling life. In comparison, organic electrode materials display the advantages of structure designability, high capacity and low limitation of cationic radius. However, organic electrode materials also encounter issues such as high‐solubility in electrolyte and low conductivity. Here, recently reported organic electrode materials, which mainly include the reactions based on either carbon‐oxygen double bond or carbon‐nitrogen double bond, and doping reactions, are systematically reviewed. Furthermore, the design strategies of organic electrodes are comprehensively summarized. The working voltage is regulated through controlling the lowest unoccupied molecular orbital energies. The theoretical capacity can be enhanced by increasing the active groups. The dissolution is inhibited with elevating the intermolecular forces with proper molecular weight. The conductivity can be improved with extending conjugated structures. Future research into organic electrodes should focus on the development of full SIBs with aqueous/aprotic electrolytes and long cycling stability.     

Recent Advances in Non‐Aqueous Electrolyte for Rechargeable Li–O2 Batteries

The rechargeable Li–O₂ battery has attracted much attention over the past decades owing to its overwhelming advantage in theoretical specific energy density compared to state‐of‐the‐art Li‐ion batteries. Practical application requires non‐aqueous Li–O₂ batteries to stably obtain high reversible capacity, which highly depends on a suitable electrolyte system. Up to now, some critical challenges remain in developing desirable non‐aqueous electrolytes for Li–O₂ batteries. Herein, we will review the current status and challenges in non‐aqueous liquid electrolytes, ionic liquid electrolytes and solid‐state electrolytes of Li–O₂ batteries, as well as the perspectives on these issues and future development.     

Metal‐Organic Framework Cathodes Based on a Vanadium Hexacyanoferrate Prussian Blue Analogue for High‐Performance Aqueous Rechargeable Batteries

Despite the unique advantages of the metal‐organic framework of Prussian blue analogues (PBAs), including a favorable crystallographic structure and facile diffusion kinetics, the capacity of PBAs delivered in aqueous systems has been limited to ≈60 mA h g^?1 because only single species of transition metal ions incorporated into the PBAs are electrochemically activated. Herein, vanadium hexacyanoferrate (V/Fe PBA) is proposed as a breakthrough to this limitation, and its electrochemical performance as a cathode for aqueous rechargeable batteries (ARBs) is investigated for the first time. V/Fe PBAs are synthesized by a simple co‐precipitation method with optimization of the acidity and molar ratios of precursor solutions. The V/Fe PBAs provide an improved capacity of 91 mA h^?1 under a current density of 110 mA g^?1 (C‐rate of ≈1.2 C), taking advantage of the multiple‐electron redox reactions of V and Fe ions. Under an extremely fast charge/discharge rate of 3520 mA g^?1, the V/Fe PBA exhibits a sufficiently high discharge capacity of 54 mA h g^?1 due to its opened structure and 3D hydrogen bonding networks. V/Fe PBA‐based ARBs are the most promising candidates for large‐scale stationary energy storage systems due to their high electrochemical performance, reasonable cost, and high efficiency.     

Rechargeable Soft‐Matter EGaIn‐MnO2 Battery for Stretchable Electronics

A rechargeable, stretchable battery composed of a liquid metal alloy (eutectic gallium‐indium; EGaIn) anode, a carbon paste, and MnO₂ slurry cathode, an alkaline electrolytic hydrogel, and a soft elastomeric package is presented. The battery can stably cycle within a voltage range of 1.40–1.86 V at 1 mA cm^?2 while being subject to 100% tensile strain. This is accomplished through a mechanism that involves reversible stripping and plating of gallium along with MnO₂ chemical conversion. Moreover, a technique to increase the contact area between the EGaIn anode and hydrogel interface using CaCl₂ additives, which reduces polarization and therefore reduces the effective current density, leading to higher discharge plateaus and lower charge plateaus. Relative to previous attempts at energy storage with liquid metal, the EGaIn‐MnO₂ battery presented here shows an exceptional areal specific capacity (≈3.8 mAh cm^?2) and robust, stable rechargeability over >100 charging cycles. The battery is also stable under bending, with negligible change in electrochemical properties when bent to a 2 mm radius of curvature. Batteries embedded within a wearable elastomeric sleeve can power a blue light‐emitting diode and strain‐sensing circuit. These demonstrations suggest that stretchable EGaIn‐MnO₂ batteries are feasible for applications in wearable energy‐storage electronics.