Toward High‐Performance Hybrid Zn‐Based Batteries via Deeply Understanding Their Mechanism and Using Electrolyte Additive

Aqueous hybrid Zn‐based batteries (ZIBs), as a highly promising alternative to lithium‐ion batteries for grid application, have made considerable progress recently. However, few studies have been reported that investigate their working mechanism in detail. Here, the operando synchrotron X‐ray diffraction is employed to thoroughly investigate the operational mechanism of a hybrid LiFePO₄(LFP)/Zn battery, which indicates only Li⁺ extraction/insertion from/into cathode during cycling. Based on this system, a cheap electrolyte additive, sodium dodecyl benzene sulfonate, is proposed to effectively enhance its electrochemical properties. The influence of the additive on the Zn anode and LFP cathode is comprehensively studied, respectively. The results show that the additive modifies the intrinsic deposit pattern of Zn²⁺ ions, rendering Zn plating/stripping highly reversible in an aqueous medium. On the other hand, the wettability of the LFP electrode is visibly a meliorated by introducing the surfactant additive, accelerating the Li‐ion diffusion at the LFP electrode/electrolyte interface, as indicated by the overpotential measurements. Benefiting from these effects, the Zn/LFP batteries deliver high rate capability and cycling stability in both coin cells and pouch cells.     

Simultaneous Cationic and Anionic Redox Reactions Mechanism Enabling High‐Rate Long‐Life Aqueous Zinc‐Ion Battery

Rechargeable aqueous zinc‐ion batteries hold great promise for potential applications in large‐scale energy storage, but the reversible insertion of bivalent Zn²⁺ and fast reaction kinetics remain elusive goals. Hence, a highly reversible Zn/VN_x O_y battery is developed, which combines the insertion/extraction reaction and pseudo‐capacitance‐liked surface redox reaction mechanism. The energy storage is induced by a simultaneous reversible cationic (V³⁺ ? V²⁺) and anionic (N^3? ? N^2?) redox reaction, which are mainly responsible for the high reversibility and no structural degradation of VN_xO_y. As expected, a superior rate capability of 200 mA h g^?1 at 30 A g^?1 and high cycling stability up to 2000 cycles are achieved. This finding opens new opportunities for the design of high‐performance cathodes with fast Zn²⁺ reaction kinetics for advanced aqueous zinc‐ion batteries.     

Highly Reversible Zn Anode Enabled by Controllable Formation of Nucleation Sites for Zn‐Based Batteries

Aqueous Zn batteries have drawn tremendous attention for their several advantages. However, the challenges of Zn anodes such as the corrosion and ZnO densification have compromised their application in rechargeable Zn‐based batteries. In this paper, a straightforward strategy is employed to facilitate the uniform Zn stripping/plating of the Zn anode through using a ZrO₂ coating layer, which contributes to the controllable nucleation sites for Zn²⁺ and fast Zn²⁺ transportation through the favorable Maxwell–Wagner polarization. As a result, the low polarization (24 mV at 0.25 mA cm^?2), high Coulombic efficiency (99.36% at 20 mA cm^?2), and long cycle life (over 3800 h at 0.25 mA cm^?2) can be obtained for the ZrO₂‐coated Zn anode. It is believed that the ZrO₂ coating layer can also act as an inert physical barrier to decrease the contact of the anode and electrolyte, thus reducing both the Zn corrosion and formation of ZnO densification, and then improve the reversibility of Zn anode. The results demonstrated in this work provide an appealing strategy for the future development of rechargeable Zn‐based batteries.     

Ionic‐Association‐Assisted Viscoelastic Nylon Electrolytes Enable Synchronously Coupled Interface for Solid Batteries

Electrolyte/electrode heterointerfaces activated by unhindered charge transfer play an important role in solid‐state and flexible batteries. However, continuous electrochemical cycling and mechanical deformations cause structural dislocation and unwanted reactions. An important challenge is to ensure enduring accurate contact between the battery components. The customization of a highly viscoelastic polyamide (PA, nylon)‐based solid electrolyte to address this key issue is presented. The approach involves the use of concentrated aqueous solutions of bis(trifluoromethane)sulfonimide lithium (LiTFSI) to structurally “unzip” and relink pristine hydrogen‐bonded PA chains by bridged cation–anion association. This elaborately tailored crosslinking technique confers upon the resultant electrolyte a combination of the preferred mechanical characteristics including high viscoelasticity and reversible stretchability, together with outstanding electrochemical performance represented by high ion conductivity (2.7 × 10^?4 S cm^?1) and high anodic stability (>3 V vs Zn/Zn²⁺). Flexible batteries with a well‐integrated configuration in which synchronous electrolyte/electrode movement guarantees intimate and compatible interfaces even during extreme deformations and electrochemical stimulations, are further demonstrated. These results reveal a promising opportunity to overcome the bottleneck caused by interfacial defects for next‐generation solid batteries by reconstituting the structure of classical polymers and developing functional electrolytes.     

A High‐Energy Aqueous Aluminum‐Manganese Battery

Rechargeable aluminum‐ion batteries have drawn considerable attention as a new energy storage system, but their applications are still significantly impeded by critical issues such as low energy density and the lack of excellent electrolytes. Herein, a high‐energy aluminum‐manganese battery is fabricated by using a Birnessite MnO₂ cathode, which can be greatly optimized by a divalence manganese ions (Mn²⁺) electrolyte pre‐addition strategy. The battery exhibits a remarkable energy density of 620 Wh kg^?1 (based on the Birnessite MnO₂ material) and a capacity retention above 320 mAh g^?1 for over 65 cycles, much superior to that with no Mn²⁺ pre‐addition. The electrochemical reactions of the battery are scrutinized by a series of analysis techniques, indicating that the Birnessite MnO₂ pristine cathode is first reduced as Mn²⁺ to dissolve in the electrolyte upon discharge, and Al_xMn_(1?x)O₂ is then generated upon charge, serving as a reversible cathode active material in following cycles. This work provides new opportunities for the development of high‐performance and low‐cost aqueous aluminum‐ion batteries for prospective applications.     

A Sieve‐Functional and Uniform‐Porous Kaolin Layer toward Stable Zinc Metal Anode

Zinc metal is considered as one of the best anode choices for rechargeable aqueous Zn‐based batteries due to its high specific capacity, abundance, and safety. However, dendrite and corrosion issues remain a challenge for this system. Herein, sieve‐element function (selective channel of Zn²⁺) and uniform‐pore distribution (≈3.0 nm) of a kaolin‐coated Zn anode (KL‐Zn) is proposed to alleviate these problems. Based on the artificial Zn metal/electrolyte interface, the KL‐Zn anode not only ensures dendrite‐free deposition and long‐time stability (800 h at 1.1 mA h cm^?2), but also retards side reactions. As a consequence, KL‐Zn/MnO₂ batteries can deliver high specific capacity and good capacity retention as well as a reasonably well‐preserved morphology (KL‐Zn) after 600 cycles at 0.5 A g^?1. This work provides a deep step toward high‐performance rechargeable Zn‐based battery system.     

A Safe Polyzwitterionic Hydrogel Electrolyte for Long‐Life Quasi‐Solid State Zinc Metal Batteries

Aqueous zinc metal batteries are safe, economic, and environmentally friendly. However, the dendrite growth and inevitable corrosion issues under aqueous condition greatly restrict the development of long cycling life zinc metal batteries. To achieve the long‐term reversible zinc deposition/dissolution, a polyzwitterionic hydrogel electrolyte (PZHE) is constructed with record high room temperature ionic conductivity of 32.0 mS cm^?1 and Zn²⁺ transference number of 0.656. The abundant hydrophilic and charged groups in the zwitterionic polymer can well immobilize water molecules in the polymer skeleton and reduce side reactions. The charged groups of the zwitterionic polymer can also homogenize the ion distribution and achieve uniform zinc deposition. Long cycling life of over 3500 h is achieved for the symmetric batteries with PZHE. Full cells with VS₂ and MnO₂ cathodes are also demonstrated to exhibit excellent cycling stability. With combined advantages of physical and chemical crosslinking gels, the PZHE enabled flexible quasi‐solid state zinc metal batteries with excellent processability, self‐healing property and safety, can operate even under various extreme conditions such as cutting, soaking, hammering, washing, burning, and freezing. It is believed that the PZHE can provide a promising opportunity and pave the way for other long‐life aqueous batteries.     

A High‐Potential Anion‐Insertion Carbon Cathode for Aqueous Zinc Dual‐Ion Battery

Aqueous dual‐ion batteries (DIBs) are promising for large‐scale energy storage due to low cost and inherent safety. However, DIBs are limited by low capacity and poor cycling of cathode materials and the challenge of electrolyte decomposition. In this study, a new cathode material of nitrogen‐doped microcrystalline graphene‐like carbon is investigated in a water‐in‐salt electrolyte of 30 m ZnCl₂, where this carbon cathode stores anions reversibly via both electrical double layer adsorption and ion insertion. The (de)insertion of anions in carbon lattice delivers a high‐potential plateau at 1.85 V versus Zn²⁺/Zn, contributing nearly 1/3 of the capacity of 134 mAh g^?1 and half of the stored energy. This study shows that both the unique carbon structure and concentrated ZnCl₂ electrolyte play critical roles in allowing anion storage in carbon cathode for this aqueous DIB.     

Electrochemically Derived Graphene‐Like Carbon Film as a Superb Substrate for High‐Performance Aqueous Zn‐Ion Batteries

3D graphene, as a light substrate for active loadings, is essential to achieve high energy density for aqueous Zn‐ion batteries, yet traditional synthesis routes are inefficient with high energy consumption. Reported here is a simplified procedure to transform the raw graphite paper directly into the graphene‐like carbon film (GCF). The electrochemically derived GCF contains a 2D–3D hybrid network with interconnected graphene sheets, and offers a highly porous structure. To realize high energy density, the Na:MnO₂/GCF cathode and Zn/GCF anode are fabricated by electrochemical deposition. The GCF‐based Zn‐ion batteries deliver a high initial discharge capacity of 381.8 mA h g^?1 at 100 mA g^?1 and a reversible capacity of 188.0 mA h g^?1 after 1000 cycles at 1000 mA g^?1. Moreover, a recorded energy density of 511.9 Wh kg^?1 is obtained at a power density of 137 W kg^?1. The electrochemical kinetics measurement reveals the high capacitive contribution of the GCF and a co‐insertion/desertion mechanism of H⁺ and Zn²⁺ ions. First‐principles calculations are also carried out to investigate the effect of Na⁺ doping on the electrochemical performance of layered δ‐MnO₂ cathodes. The results demonstrate the attractive potential of the GCF substrate in the application of the rechargeable batteries.     

“Water-in-Deep Eutectic Solvent” Electrolytes for High-Performance Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries have been considered as promising alternatives to Li-ion batteries due to their abundant reserves, low price, and high safety. However, Zn anode shows poor reversibility and cycling stability in most conventional aqueous electrolytes. Here, a new type of aqueous Zn-ion electrolyte based on ZnCl₂–acetamide deep eutectic solvent with both environmental and economic friendliness has been prepared. The water molecule introduced in the “water-in-deep eutectic solvent” electrolyte could reduce the Zn²⁺ desolvation energy barrier by regulating Zn²⁺ solvation structure to promote uniform Zn nucleation. Zn anode shows improved electrochemical performance (≈98% Coulombic efficiency over 1000 cycles) in the electrolyte whose molar ratio of ZnCl₂:acetamide:H₂O is 1:3:1. The assembled full battery composed of phenazine cathode and Zn anode could stably cycle over 10 000 cycles with a high capacity retention of 85.7%. Overall, this work offers new insights into exploring new green electrolyte systems for Zn-ion batteries.     

Cations Coordination-Regulated Reversibility Enhancement for Aqueous Zn-Ion Battery

Aqueous Zn-ion batteries are emerging as a promising candidate for large-scale energy storage, while the short lifetime and poor reversibility of Zn anodes limit their further development. When attempting to enhance reversibility, most reported methods involve toxic and pollutive substances and decreased water content, which inevitably sacrificed safety level, rate performance, and environmentally benign characteristics. Herein, a series of low-cost and “green” molecules are introduced into the aqueous (ZnCl₂, ZnSO₄) electrolytes, featured with cations coordination capability, which can significantly inhibit the hydration step of Zn²⁺ and delay the formation of the key by-products (Zn₅(OH)₈Cl₂·H₂O, 3Zn(OH)₃·ZnSO₄·5H₂O) in aqueous electrolytes via regulating the coordination status of Zn²⁺. In the optimized electrolyte system, a highly reversible Zn metal anode presents excellent electrochemical performance, featured with a long lifespan over 1185 h at 1 mA cm⁻² and smooth deposition morphology. Furthermore, Zn–MnO₂ batteries based on the electrolyte deliver high capacity retention of 82.9% after 200 cycles. These breakthroughs suggest that this method offers a versatile toolbox toward developing future advanced multivalent metal batteries for large-scale energy storage.     

Realizing a Rechargeable High‐Performance Cu–Zn Battery by Adjusting the Solubility of Cu2+

Rechargeable aqueous Zn‐based batteries show great potential for energy storage systems due to their good reliability, low cost, environmental friendliness, etc. However, the capacity of the most studied Mn‐, V‐, and Prussian blue analog‐based Zn‐ion batteries (the type with Zn²⁺ insertion) and the other type Zn‐based batteries without Zn²⁺ insertion (such as metal Ag and Ni or Co oxides/hydroxides) does not exceed 400 mAh g^?1. Cu is a promising cathode with a high theoretical capacity of 844 mAh g^?1 based on its unique two‐electron transfer process (Cu⁰ ? Cu²⁺), but Cu–Zn batteries have been impractical to recharge since they was invented by Daniell in 1836. By adjusting the solubility of Cu²⁺ in an alkaline solution, a rechargeable high‐performance Cu–Zn battery is achieved. A high specific capacity of 718 mAh g^?1 is obtained for the prepared Cu clusters. Moreover, commercial Cu foil is explored for direct use as the cathode material and shows high capacity and stability through a simple self‐activation process. This rechargeable Cu–Zn battery is attractive for application due to its high capacity, simple synthesis method, environmental friendliness, and low cost.     

2D Nitrogen‐Doped Carbon Nanotubes/Graphene Hybrid as Bifunctional Oxygen Electrocatalyst for Long‐Life Rechargeable Zn–Air Batteries

The rational construction of efficient bifunctional oxygen electrocatalysts is of immense significance yet challenging for rechargeable metal–air batteries. Herein, this work reports a metal–organic framework derived 2D nitrogen‐doped carbon nanotubes/graphene hybrid as the efficient bifunctional oxygen electrocatalyst for rechargeable zinc–air batteries. The as‐obtained hybrid exhibits excellent catalytic activity and durability for the oxygen electrochemical reactions due to the synergistic effect by the hierarchical structure and heteroatom doping. The assembled rechargeable zinc–air battery achieves a high power density of 253 mW cm^?2 and specific capacity of 801 mAh g_Zn^?1 with excellent cycle stability of over 3000 h at 5 mA cm^?2. Moreover, the flexible solid‐state rechargeable zinc–air batteries assembled by this hybrid oxygen electrocatalyst exhibits a high discharge power density of 223 mW cm^?2, which can power 45 light‐emitting diodes and charge a cellphone. This work provides valuable insights in designing efficient bifunctional oxygen electrocatalysts for long‐life metal–air batteries and related energy conversion technologies.     

Electronic Structure Regulation of Layered Vanadium Oxide via Interlayer Doping Strategy toward Superior High‐Rate and Low‐Temperature Zinc‐Ion Batteries

Currently, development of suitable cathode materials for zinc‐ion batteries (ZIBs) is plagued by the sluggish kinetics of Zn²⁺ with multivalent charge in the host structure. Herein, it is demonstrated that interlayer Mn²⁺‐doped layered vanadium oxide (Mn_0.15V₂O₅·nH₂O) composites with narrowed direct bandgap manifest greatly boosted electrochemical performance as zinc‐ion battery cathodes. Specifically, the Mn_0.15V₂O₅·nH₂O electrode shows a high specific capacity of 367 mAh g^?1 at a current density of 0.1 A g^?1 as well as excellent retentive capacities of 153 and 122 mAh g^?1 after 8000 cycles at high current densities up to 10 and 20 A g^?1, respectively. Even at a low temperature of ?20 °C, a reversible specific capacity of 100 mAh g^?1 can be achieved at a current density of 2.0 A g^?1 after 3000 cycles. The superior electrochemical performance originates from the synergistic effects between the layered nanostructures and interlayer doping of Mn²⁺ ions and water molecules, which can enhance the electrons/ions transport kinetics and structural stability during cycling. With the aid of various ex situ characterization technologies and density functional theory calculations, the zinc‐ion storage mechanism can be revealed, which provides fundamental guidelines for developing high‐performance cathodes for ZIBs.     

Low-Cost Multi-Function Electrolyte Additive Enabling Highly Stable Interfacial Chemical Environment for Highly Reversible Aqueous Zinc Ion Batteries

The practicality of aqueous zinc ion batteries (AZIBs) for large-scale energy storage is hindered by challenges associated with zinc anodes. In this study, a low-cost and multi-function electrolyte additive, cetyltrimethyl ammonium bromide (CTAB), is presented to address these issues. CTAB adsorbs onto the zinc anode surface, regulating Zn²⁺ deposition orientation and inhibiting dendrite formation. It also modifies the solvation structure of Zn²⁺ to reduce water reactivity and minimize side reactions. Additionally, CTAB optimizes key physicochemical parameters of the electrolyte, enhancing the stability of the electrode/electrolyte interface and promoting reversibility in AZIBs. Theoretical simulations combined with operando synchrotron radiation-based in situ Fourier transform infrared spectra and in situ electrochemical impedance spectra further confirm the modified Zn²⁺ coordination environment and the adsorption effect of CTAB cations at the anode/electrolyte interface. As a result, the assembled Zn-MnO₂ battery demonstrates a remarkable specific capacity of 126.56 mAh g⁻¹ at a high current density of 4 A g⁻¹ after 1000 cycles. This work highlights the potential of CTAB as a promising solution for improving the performance and practicality of AZIBs for large-scale energy storage applications.     

Designing Dendrite‐Free Zinc Anodes for Advanced Aqueous Zinc Batteries

Zn metal has been regarded as the most promising anode for aqueous batteries due to its high capacity, low cost, and environmental benignity. Zn anode still suffers, however, from low Coulombic efficiency due to the side reactions and dendrite growth in slightly acidic electrolytes. Here, the Zn plating/stripping mechanism is thoroughly investigated in 1 m ZnSO₄ electrolyte, demonstrating that the poor performance of Zn metal in mild electrolyte should be ascribed to the formation of a porous by‐product (Zn₄SO₄(OH)₆·xH₂O) layer and serious dendrite growth. To suppress the side reactions and dendrite growth, a highly viscoelastic polyvinyl butyral film, functioning as an artificial solid/electrolyte interphase (SEI), is homogeneously deposited on the Zn surface via a simple spin‐coating strategy. This dense artificial SEI film not only effectively blocks water from the Zn surface but also guides the uniform stripping/plating of Zn ions underneath the film due to its good adhesion, hydrophilicity, ionic conductivity, and mechanical strength. Consequently, this side‐reaction‐free and dendrite‐free Zn electrode exhibits high cycling stability and enhanced Coulombic efficiency, which also contributes to enhancement of the full‐cell performance when it is coupled with MnO₂ and LiFePO₄ cathodes.     

CuCo Bimetallic Oxide Quantum Dot Decorated Nitrogen‐Doped Carbon Nanotubes: A High‐Efficiency Bifunctional Oxygen Electrode for Zn–Air Batteries

The large‐scale production of metal–air batteries, an appealing solution for next‐generation energy storage, requires low‐cost, earth‐abundant, and efficient oxygen electrode materials, yet insights into active catalyst structures and synergistic reactivity remain largely unknown. Here, a new bifunctional oxygen electrode based on nitrogen‐doped carbon nanotubes decorated by spinel CuCo₂O₄ quantum dots (CuCo₂O₄/N‐CNTs) is reported, outperforming the benchmark of state‐of‐the‐art noble metal catalysts. Combining spectroscopic characterization and electrochemical studies, a prominent synergetic effect between CuCo₂O₄ and N‐doped carbon nanotubes is uncovered: the high conductivity, large active surface area, and increase in the number of catalytic sites induced by Cu doping (i.e., Cu²⁺ and Cu?N) can be beneficial to the overall electrocatalytic activities. Remarkably, the native flexibility of CuCo₂O₄/N‐CNTs allows its direct use as reversible oxygen electrodes in Zn–air batteries either with liquid alkaline electrolyte or in the all‐solid‐state configuration. The prepared devices demonstrate excellent discharging/charging performance, large energy density (83.83 mW cm^?2 in liquid state, 1.86 W g^?1 in all‐solid‐state), and long lifetime (48 h in liquid state, 9 h in all‐solid‐state), holding great promise in the practical application of rechargeable metal–air batteries and other fuel cells.     

Low-Cost,Safe, and Ultra-Long Cycle Life Zn–K Hybrid Ion Batteries

Zinc-ion batteries (ZIBs) are viewed as a promising energy storage system for large-scale applications thanks to the low cost and wide accessibility of Zn-based materials, the high theoretical capacity of Zn anode, and their high level of safety. However, the practical application of ZIBs is hindered by the rapid performance degradation. Herein, a Zn–K hybrid ion battery design is proposed using a high-quality Prussian blue cathode and a nonflammable Zn–K hybrid ion electrolyte. The electrochemical process is divided into two parts, with K⁺ insertion/extraction occurring at the cathode side and Zn²⁺ plating/stripping occurring at the anode side, which avoids structure destruction caused by Zn²⁺ insertion in the cathode. The non-flammable electrolyte not only ensures high safety but also effectively suppresses dendrite growth on the Zn anode. The hybrid cells demonstrate a high capacity of 151.0 mAh g⁻¹, a high voltage of 1.74 V (vs Zn²⁺/Zn), and an ultra-long cycle life of 15 000 cycles. Combining the nonflammable nature of the electrolyte, the abundance of raw materials, and good electrochemical performance, the Zn–K hybrid ion battery system promises a promising future for renewable energy storage applications.     

Suppressing Manganese Dissolution in Potassium Manganate with Rich Oxygen Defects Engaged High‐Energy‐Density and Durable Aqueous Zinc‐Ion Battery

The manganese dissolution leading to sharp capacity decline as well as the sluggish reaction kinetic are still major issues for manganese‐based materials as aqueous zinc‐ion batteries (ZIBs) cathodes. Here, a potassium‐ion‐stabilized and oxygen‐defect K_0.8Mn₈O₁₆ is reported as a high‐energy‐density and durable cathode for neutral aqueous ZIBs. A new insight into suppressing manganese dissolution via incorporation of K⁺ ions to intrinsically stabilize the Mn‐based cathodes is provided. A comprehensive study suggests that oxygen defects improve electrical conductivity and open the MnO₆ polyhedron walls for ion diffusion, which plays a critical role in the fast reaction kinetics and capacity improvement of K_0.8Mn₈O₁₆. In addition, direct evidence for the mechanistic details of simultaneous insertion and conversion reaction based on H⁺‐storage mechanism is demonstrated. As expected, a significant energy output of 398 W h kg^?1 (based on the mass of cathode) and an impressive durability over 1000 cycles with no obvious capacity fading are obtained. Such a high‐energy Zn‐K_0.8Mn₈O₁₆ battery, as well as the basic understanding of manganese dissolution and oxygen defects may open new opportunities toward high‐performance aqueous ZIBs.     

Single‐Atom Fe‐Nx‐C as an Efficient Electrocatalyst for Zinc–Air Batteries

Highly efficient non‐noble metal electrocatalysts are vital for metal–air batteries and fuel cells. Herein, a noble‐metal–free single‐atom Fe‐N _x‐C electrocatalyst is synthesized by incorporating Fe‐Phen complexes into the nanocages in situ during the growth of ZIF‐8, followed by pyrolysis at 900 °C under inert atmosphere. Fe‐Phen species provide both Fe²⁺ and the organic ligand (Phen) simultaneously, which play significant roles in preparing single‐atom catalysts. The obtained Fe‐N_x‐C exhibits a half‐wave potential of 0.91 V for the oxygen reduction reaction, higher than that of commercial Pt/C (0.82 V). As a cathode catalyst for primary zinc–air batteries (ZABs), the battery shows excellent electrochemical performances in terms of the high open‐circuit voltage (OCV) of 1.51 V and a high power density of 96.4 mW cm^?2. The rechargeable ZAB with Fe‐N_x‐C catalyst and the alkaline electrolyte shows a remarkable cycling performance for 300 h with an initial round‐trip efficiency of 59.6%. Furthermore, the rechargeable all‐solid‐state ZABs with the Fe‐N_x‐C catalyst show high OCV of 1.49 V, long cycle life for 120 h, and foldability. The single‐atom Fe‐N_x‐C electrocatalyst may function as a promising catalyst for various metal–air batteries and fuel cells.