A Review of Rechargeable Zinc-Air Batteries:Recent Progress and Future Perspectives

Zinc-air batteries(ZABs)are gaining attention as an ideal option for various applications requiring high-capacity batteries,such as portable electronics,electric vehicles,and renewable energy storage.ZABs offer advantages such as low environmental impact,enhanced safety compared to Li-ion batteries,and cost-effectiveness due to the abundance of zinc.However,early research faced challenges due to parasitic reactions at the zinc anode and slow oxygen redox kinetics.Recent advancements in restructuring the anode,utilizing alternative electrolytes,and developing bifunctional oxygen catalysts have significantly improved ZABs.Scientists have achieved battery reversibility over thousands of cycles,introduced new electrolytes,and achieved energy efficiency records surpassing 70%.Despite these achievements,there are challenges related to lower power density,shorter lifespan,and air electrode corrosion leading to performance degradation.This review paper discusses different battery configurations,and reaction mechanisms for electrically and mechanically rechargeable ZABs,and proposes remedies to enhance overall battery performance.The paper also explores recent advancements,applications,and the future prospects of electrically/mechanically rechargeable ZABs.

Electronic structure and spin state regulation of vanadium nitride via a sulfur doping strategy toward flexible zinc-air batteries

Owing to the distinctive structural characteristics,vanadium nitride(VN)is highly regarded as a catalyst for oxygen reduction reaction(ORR)in zinc-air batteries(ZABs).However,VN exhibits limited intrinsic ORR activity due to the weak adsorption ability to O-containing species.Here,the S-doped VN anchored on N,S-doped multi-dimensional carbon(S-VN/Co/NS-MC)was constructed using the solvothermal and in-situ doping methods.Incorporating sulfur atoms into VN species alters the electron spin state of vanadium in the S-VN/Co/NS-MC for regulating the adsorption energy of vanadium sites to oxygen molecules.The introduced sulfur atoms polarize the V 3d_(z)^(2) electrons,shifting spin-down electrons closer to the Fermi level in the S-VN/Co/NS-MC.Consequently,the introduction of sulfur atoms into VN species enhances the adsorption energy of vanadium sites for oxygen molecules.The*OOH dissociation transitions from being unspontaneous on the VN surface to a spontaneous state on the S-doped VN surface.Then,the ORR barrier on the S-VN/Co/NS-MC surface is reduced.The S-VN/Co/NS-MC demonstrates a higher half-wave potential and limiting current density compared to the VN/Co/N-MC.The S-VN/Co/NS-MC-based liquid ZABs display a power density of 195.7 m W cm^(-2),a specific capacity of 815.7 m A h g^(-1),and a cycling stability exceeding 250 h.The S-VN/Co/NS-MC-based flexible ZABs are successfully employed to charge both a smart watch and a mobile phone.This approach holds promise for advancing the commercial utilization of VN-based catalysts in ZABs.

Insights into the hydrogen evolution reaction in vanadium redox flow batteries:A synchrotron radiation based X-ray imaging study

The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble formation is crucial.This benchmarking study locally analyzes the bubble distribution in thick,porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms.Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs.The study systematically varies the electrode potential and material,concluding that more negative electrode potentials of-200 m V vs.reversible hydrogen electrode(RHE)and lower cause more substantial bubble formation,resulting in bubble fractions of around 15%–20%in carbon felt electrodes.Contrarily,the bubble fractions stay only around 2%in an electrode combining carbon felt and carbon paper.The detected areas with high HER activity,such as the border subregion with more than 30%bubble fraction in carbon felt electrodes,the cutting edges,and preferential spots in the electrode bulk,are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses.The described combination of electrochemical measurements,local X-ray microtomography,AI-based segmentation,and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes,providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.

Schiff-base polymer derived FeCo-N-doped porous carbon flowers as bifunctional oxygen electrocatalyst for long-life rechargeable zinc-air batteries

Rational design and exploration of low-cost and robust bifunctional oxygen electrocatalysts are vitally important for developing high-performance zinc-air batteries(ZABs).Herein,we reported a facile yet cost-efficient approach to construct a bifunctional oxygen reduction reaction(ORR)/oxygen evolution reaction(OER)electrocatalyst composed of N-doped porous carbon nanosheet flowers decorated with Fe Co nanoparticles(Fe Co/N-CF).Rational design of this catalyst is achieved by designing Schiff-base polymer with unique molecular structure via hydrogen bonding of cyanuramide and terephthalaldehyde polycondensate in the presence of metal cations.It exhibits excellent activity and stability for electrocatalysis of ORR/OER,enabling ZAB with a high peak power density of 172 m W cm^(-2)and a large specific capacity of 811 m A h g^(-1)Znat large current.The rechargeable ZAB demonstrates excellent durability for 1000 h with slight voltage decay,far outperforming a couple of precious Pt/Ir-based catalysts.Density functional theory(DFT)calculations reveal that high activity of bimetallic Fe Co stems from enhanced O_(2)and OH-adsorption and accelerated O_(2)dissociation by OAO bond activation.

Recent progress of self-supported air electrodes for flexible Zn-air batteries

Smart wearable devices are regarded to be the next prevailing technology product after smartphones and smart homes,and thus there has recently been rapid development in flexible electronic energy storage devices.Among them,flexible solid-state zinc-air batteries have received widespread attention because of their high energy density,good safety,and stability.Efficient bifunctional oxygen electrocatalysts are the primary consideration in the development of flexible solid-state zinc-air batteries,and self-supported air cathodes are strong candidates because of their advantages including simplified fabrication process,reduced interfacial resistance,accelerated electron transfer,and good flexibility.This review outlines the research progress in the design and construction of nanoarray bifunctional oxygen electrocatalysts.Starting from the configuration and basic principles of zinc-air batteries and the strategies for the design of bifunctional oxygen electrocatalysts,a detailed discussion of self-supported air cathodes on carbon and metal substrates and their uses in flexible zinc-air batteries will follow.Finally,the challenges and opportunities in the development of flexible zinc-air batteries will be discussed.

Organized macro-scale membrane size reduction in vanadium redox flow batteries:Part 1.General concept

The high costs of the currently used membranes in vanadium redox flow batteries(VRFBs)contribute to the price of the vanadium redox flow battery systems and therefore limit the market share of the VRFBs.Here we report a detailed simulation and experimental studies on the effect of membrane reduction of single-cell VRFB.Different simulated designs demonstrate that a proposed centred and double-strip membrane coverage showed a promising performance.Experimental charge-discharge profile of different membrane size reduction,which showed good agreement with simulated data,suggests that the membrane size can comfortably be reduced by up to 20%without severe efficiency or discharge capacity loss.Long-term cycling of 80%centred membrane coverage showed improved capacity retention during the latter cycles with almost 1%difference in capacity and only 2%in energy efficiency when compared to the fully covered-membrane cell.The results hold great promise for the development of cheap RFB stacks and facilitate the way to develop new cell designs with non-overlapping electrodes geometry.Therefore,giving more flexibility to improve the overall performance of the system.

Edge atomic Fe sites decorated porous graphitic carbon as an efficient bifunctional oxygen catalyst for Zinc-air batteries

The development of advanced bifunctional oxygen electrocatalysts for oxygen reduction and evolution reactions(ORR and OER) is critical to the practical application of zinc-air batteries(ZABs). Herein, a silica-assisted method is reported to integrate numerous accessible edge Fe-Nx sites into porous graphitic carbon(named Fe-N-G) for achieving highly active and robust oxygen electrocatalysis. Silica facilitates the formation of edge Fe-Nx sites and dense graphitic domains in carbon by inhibiting iron aggregation.The purification process creates a well-developed mass transfer channel for Fe-N-G. Consequently,Fe-N-G delivers a half-wave potential of 0.859 V in ORR and an overpotential of 344 m V at10 m A cm^(-2)in OER. During long-term operation, the graphitic layers protect edge Fe-Nx sites from demetallation in ORR and synergize with Fe OOH species endowing Fe-N-G with enhanced OER activity.Density functional theory calculations reveal that the edge Fe-Nx site is superior to the in-plane Fe-Nx site in terms of OH* dissociation in ORR and OOH* formation in OER. The constructed ZAB based on Fe-N-G cathode shows a higher peak power density of 133 m W cm^(-2)and more stable cycling performance than Pt/C + RuO2counterparts. This work provides a novel strategy to obtain high-efficiency bifunctional oxygen electrocatalysts through space mediation.

Regulated electronic structure and improved electrocatalytic performances of S-doped FeWO4 for rechargeable zinc-air batteries

The exploration of active and long-lived oxygen reduction reaction(ORR)catalysts for the commercialization of zinc-air batteries are of immense significance but challenging.Herein,the sulfur doped FeWO_(4)embedded in the multi-dimensional nitrogen-doped carbon structure(S-FeWO_(4)/NC)was successfully synthesized.The doped S atoms optimized the charge distribution in FeWO_(4)and enhanced the intrinsic activity.At the same time,S doping accelerated the formation of reaction intermediates during the adsorption reduction of O_(2)on the surface of S-FeWO_(4)/NC.Accordingly,the S-FeWO_(4)/NC catalyst showed more positive half-wave potential(0.85 V)and better stability than that of the FeWO_(4)/NC catalyst.Furthermore,the S-FeWO_(4)/NC-based zinc-air battery exhibited considerable power density of 150.3m W cm^(-2),high specific capacity of 912.7 m A h g^(-1),and prominent cycle stability up to 220 h.This work provides an assistance to the development of cheap and efficient tungsten-based oxygen reduction catalysts and the promotion of its application in the zinc-air battery.

Manipulating the ion-transference and deposition kinetics by regulating the surface chemistry of zinc metal anodes for rechargeable zinc-air batteries

Aqueous zinc-air battery(ZAB)has attractive features as the potential energy storage system such as high safety,low cost and good environmental compatibility.However,the issue of dendrite growth on zinc metal anodes has seriously hindered the development of ZAB.Herein,the N-doped carbon cloth(NC)prepared via magnetron sputtering is explored as the substrate to induce the uniform nucleation of zinc metal and suppress dendrite growth.Results show that the introduction of heteroatoms accelerates the migration and deposition kinetics of Zn^(2+)by boosting the desolvation process of Zn^(2+),eventually reducing the nucleation overpotential.Besides,theoretical calculation results confirm the zincophilicity of N-containing functional group(such as pyridine N and pyrrole N),which can guide the nucleation and growth of zinc uniformly on the electrode surface by both promoting the redistribution of Zn^(2+) in the vicinity of the surface and enhancing its interaction with zinc atoms.As a result,the half-cell assembled with magnetron sputtered carbon cloth achieves a high zinc stripping/plating coulombic efficiency of 98.8%and long-term stability of over 500 cycles at 0.2 mA cm^(-2).And the Coulombic efficiency reached about 99.5%at the 10th cycle and maintained for more than 210 cycles at a high current density of 5.0 mA cm^(-2).The assembled symmetrical battery can deliver 220 plating/stripping cycles with ultra-low voltage hysteresis of only 11 mV.In addition,the assembled zinc-air full battery with NC-Zn anode delivers a high special capacity of about 429 mAh g_(Zn)^(-1) and a long life of over 430 cycles.The effectiveness of surface functionalization in promoting the transfer and deposition kinetics of Zn^(2+) presented in this work shows enlightening significance in the development of metal anodes in aqueous electrolytes.

Electronically modulated d-band centers of MOF-derived carbon-supported Ru/HfO_(2) for oxygen reduction and aqueous/flexible zinc-air batteries

The construction of oxide/metal composite catalysts is a competent means of exploiting the electronic interactions between oxide/metal to enhance catalytic activity.In this work,we construct a novel heterogeneous composite(Ru/HfO_(2)-NC)with Ru/HfO2nanoparticles nested in nitrogen-doped porous carbon via a zeolitic imidazole frameworks-assisted(ZIF)co-precipitation and calcination approach.In particular,ZIF guides an in-situ construction of nested configuration and confines the scattered nanoparticles.Strikingly,Ru/HfO_(2)-NC exhibits unusual ORR activity,superb durability,and methanol tolerance in0.1 M KOH solution with high half-wave potential(E1/2)of 0.83 V and follows a near-4e-reaction pathway.Additionally,the ZAB assembled with cathodic Ru/HfO_(2)-NC outputs a power density of 157.3 m W cm^(-2),a specific capacity of 775 mA h g-1Zn,and a prolonged lifespan of 258 h at 5 mA cm^(-2).Meanwhile,the catalyst has demonstrated potential applicability in flexible ZAB.As suggested by experimental results and density functional theory(DFT)analysis,the remarkable property possibly originated from the optimization of the adsorption and desorption of reactive intermediates caused by the reconfiguration of the electronic structure between Ru and HfO_(2).

Bulk preparation of free-standing single-iron-atom catalysts directly as the air electrodes for high-performance zinc-air batteries

The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction(ORR)at the cathode.Herein,we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube(FeSAC/PCMT)sponge.Benefiting from its unique structure that greatly facilitates the catalytic kinetics,mass transport,and electron transfer,our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at^(-3) mA cm^(-2).When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries,high peak power densities of 183.1 and 58.0 mW cm^(-2) were respectively achieved,better than its powdery counterpart and commercial Pt/C catalyst.Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N_(5) species in FeSAC/PCMT.This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes,provides a significant new insight into the catalytic mechanisms,and helps to realize significant advances in energy devices.

Soft Template-Induced Porous Polyvinylidene Fluoride Membrane for Vanadium Flow Batteries

Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.

Mutual Self‑Regulation of d‑Electrons of Single Atoms and Adjacent Nanoparticles for Bifunctional Oxygen Electrocatalysis and Rechargeable Zinc‑Air Batteries

Rechargeable zinc-air batteries(ZABs)are a promising energy conversion device,which rely critically on electrocatalysts to accelerate their rate-determining reactions such as oxygen reduction(ORR)and oxygen evolution reactions(OER).Herein,we fabricate a range of bifunctional M-N-C(metal-nitrogen-carbon)catalysts containing M-Nx coordination sites and M/MxC nanoparticles(M=Co,Fe,and Cu)using a new class ofγ-cyclodextrin(CD)based metal-organic framework as the precursor.With the two types of active sites interacting with each other in the catalysts,the obtained Fe@C-FeNC and Co@C-CoNC display superior alkaline ORR activity in terms of low half-wave(E1/2)potential(~0.917 and 0.906 V,respectively),which are higher than Cu@C-CuNC(~0.829 V)and the commercial Pt/C(~0.861 V).As a bifunctional electrocatalyst,the Co@C-CoNC exhibits the best performance,showing a bifunctional ORR/OER overpotential(ΔE)of~0.732 V,which is much lower than that of Fe@C-FeNC(~0.831 V)and Cu@C-CuNC(~1.411 V),as well as most of the robust bifunctional electrocatalysts reported to date.Synchrotron X-ray absorption spectroscopy and density functional theory simulations reveal that the strong electronic correlation between metallic Co nanoparticles and the atomic Co-N4 sites in the Co@C-CoNC catalyst can increase the d-electron density near the Fermi level and thus effectively optimize the adsorption/desorption of intermediates in ORR/OER,resulting in an enhanced bifunctional electrocatalytic performance.The Co@C-CoNC-based rechargeable ZAB exhibited a maximum power density of 162.80 mW cm^(−2) at 270.30 mA cm^(−2),higher than the combination of commercial Pt/C+RuO2(~158.90 mW cm^(−2) at 265.80 mA cm^(−2))catalysts.During the galvanostatic discharge at 10 mA cm^(−2),the ZAB delivered an almost stable discharge voltage of 1.2 V for~140 h,signifying the virtue of excellent bifunctional ORR/OER electrocatalytic activity.

Lattice Boltzmann modeling of transport phenomena in fuel cells and flow batteries

Fuel cells and flow batteries are promising technologies to address climate change and air pollution problems. An understanding of the complex multiscale and multiphysics transport phenomena occurring in these electrochemical systems requires powerful numerical tools. Over the past decades, the lattice Boltzmann (LB) method has attracted broad interest in the computational fluid dynamics and the numerical heat transfer communities, primarily due to its kinetic nature making it appropriate for modeling complex multiphase transport phenomena. More importantly, the LB method fits well with parallel computing due to its locality feature, which is required for large-scale engineering applications. In this article, we review the LB method for gas-liquid two-phase flows, coupled fluid flow and mass transport in porous media, and particulate flows. Examples of applications are provided in fuel cells and flow batteries. Further developments of the LB method are also outlined.

A review of electrolyte additives and impurities in vanadium redox flow batteries

As one of the most important components of the vanadium redox flow battery （VRFB）, the electrolyte can impose a significant impact on cell properties, performance and capital cost. In particular, the electrolyte composition will influence energy density, operating temperature range and the practical applications of the VRFB. Various approaches to increase the energy density and operating temperature range have been proposed. The presence of electrolyte impurities, or the addition of a small amount of other chemical species into the vanadium solution can alter the stability of the electrolyte and influence cell perfor- mance, operating temperature range, energy density, electrochemical kinetics and cost effectiveness. This review provides a detailed overview of research on electrolyte additives including stabilizing agents, im- mobilizing agents, kinetic enhancers, as well as electrolyte impurities and chemical reductants that can be used for different purposes in the VRFBs.

Modified carbon cloth as positive electrode with high electrochemical performance for vanadium redox flow batteries

Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries. The SEM shows that the treatment has no obvious influence on the morphology of carbon cloth. XPS measurements indicate that the nitrogenous functional groups can be introduced on the surface of carbon cloth successfully. The electrochemical performance of V(IV)/V(V) redox couple on the prepared electrode is evaluated with cyclic voltammetry and linear sweep voltammetry measurements. The N-doped carbon cloth exhibits outstanding electrochemical activity and reversibility toward V(IV)/V(V) redox couple. The rate constant of V(IV)/V(V) redox reaction on carbon cloth can increase to 2.27 x 10(-4) cm/s from 1.47 x 10(-4) cm/s after nitrogen doping. The cell using N-doped carbon cloth as positive electrode has larger discharge capacity and higher energy efficiency compared with the cell using pristine carbon cloth. The average energy efficiency of the cell using N-doped carbon cloth for 50 cycles at 30 mA/cm(2) is 87.8%, 4.3% larger than that of the cell using pristine carbon cloth. It indicates that the N-doped carbon cloth has a promise application prospect in vanadium redox flow batteries. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Recent Advances on MOF Derivatives for Non-Noble Metal Oxygen Electrocatalysts in Zinc-Air Batteries

Oxygen electrocatalysts are of great importance for the air electrode in zinc-air batteries(ZABs).Owing to the high specific surface area,controllable pore size and unsaturated metal active sites,metal-organic frameworks(MOFs)derivatives have been widely studied as oxygen electrocatalysts in ZABs.To date,many strategies have been developed to generate efficient oxygen electrocatalysts from MOFs for improving the performance of ZABs.In this review,the latest progress of the MOF-derived non-noble metal-oxygen electrocatalysts in ZABs is reviewed.The performance of these MOF-derived catalysts toward oxygen reduction,and oxygen evolution reactions is discussed based on the categories of metal-free carbon materials,single-atom catalysts,metal cluster/carbon composites and metal compound/carbon composites.Moreover,we provide a comprehensive overview on the design strategies of various MOF-derived non-noble metal-oxygen electrocatalysts and their structure-performance relationship.Finally,the challenges and perspectives are provided for further advancing the MOF-derived oxygen electrocatalysts in ZABs.

Progress on the electrode materials towards vanadium flow batteries (VFBs) with improved power density

The vanadium flow battery （VFB） has been considered as one of the most promising large-scale energy storage technologies in terms of its design flexibility, long cycle life, high efficiency and high safety. How- ever, the high cost prevents the VFB technology from broader market penetration. Improving the power density of the VFB is an effective solution to reduce its cost due to the reduced material consumption and stack size. Electrode, as one of the main components in the VFB, providing the reactions sites for redox couples, has an important effect on the voltage loss of the VFB associated with electrochemical polariza- tion, ohmic polarization and concentration polarization. Extensive research has been carried out on the electrode modification to reduce polarizations and hence improve the power density of the VFB. In this review, state-of-the-art of various modification methods on the VFB electrode materials is overviewed and summarized, and the future research directions helpful to reduce polarization loss are presented.

The catalytic effect of bismuth for VO2+/VO2+and V3+/V2+redox couples in vanadium flow batteries

The effect of bismuth (Bi) for both VO2+/VO2+ and V3+/V2+ redox couples in vanadium flow batteries (VFBs) has been investigated by directly introducing Bi on the surface of carbon felt (CF). The results show that Bi has no catalytic effect for VO2+/VO2(+) redox couple. During the first charge process, Bi is oxidized to Bi3+ (never return back to Bi metal in the subsequent cycles) due to the low standard redox potential of 0.308 V (vs. SHE) for Bi3+/Bi redox couple compared with VO2+/VO2+ redox couple and Bi3+ exhibit no (or neglectable) electro-catalytic activity. Additionally, the relationship between Bi loading and electrochemical activity for V3+/V2+ redox couple was studied in detail. 2 wt% Bi-modified carbon felt (2%-BiCF) exhibits the highest electrochemical activity. Using it as negative electrode, a high energy efficiency (EE) of 79.0% can be achieved at a high current density of 160 mA/cm(2), which is 5.5% higher than the pristine one. Moreover, the electrolyte utilization ratio is also increased by more than 30%. Even the cell operated at 140 mA/cm(2) for over 300 cycles, the EE can reach 80.9% without obvious fluctuation and attenuation, suggesting excellent catalytic activity and electrochemical stability in VFBs. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Carbon-based cathode materials for rechargeable zinc-air batteries: From current collectors to bifunctional integrated air electrodes

Rechargeable zinc-air batteries(ZABs)have attracted much attention as the next-generation energy conversion and storage devices due to the abundance and environmental friendliness of zinc(Zn)for anode materials,as well as the safety and low cost of aqueous electrolytes.However,rational design of nonprecious and low-cost integrated air cathode materials with a desirable bifunctional oxygen electrocatalytic performance remains a great challenge for the commercialization of rechargeable ZABs.In previous research studies,various cost-effective carbon-supported electrocatalysts and light-weight carbon-based current collectors for air cathodes have been developed,showing vast potential in the application of carbon-based materials.To improve the bifunctional performance and integration of air cathodes,efforts with respect to the design of morphology,defects,and synergistic effects of carbon-based materials have been made.In this perspective,the general understanding of the air cathode construction and the battery working mechanism is discussed.The recent progress in the design of carbon-based materials for air cathodes in rechargeable ZABs is summarized.Several possible future research directions and the expected development trends are also discussed,aiming to facilitate the commercialization of advanced rechargeable ZABs in our life.