Search Results (36)

Solid polymer electrolytes (SPEs) are gaining attention as viable alternatives to traditional aqueous electrolytes in zinc–air batteries (ZABs), owing to their enhanced performance and stability. In this study, anion-exchange solid polymer electrolytes (A-SPEs) were synthesized via electrophilic aromatic substitution and substitution reactions. Thin films were prepared using the solvent casting method and characterized using proton nuclear magnetic resonance (¹H-NMR), Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The ion-exchange capacity (IEC), KOH uptake, ionic conductivity, and battery performance were also obtained by varying the degree of functionalization of the A-SPEs (30 and 120%, denoted as PSf30/PSf120, respectively). The IEC analysis revealed that PSf120 exhibited a higher quantity of functional groups, enhancing its hydroxide conductivity, which reached a value of 22.19 mS cm⁻¹. In addition, PSf120 demonstrated a higher power density (70 vs. 50 mW cm⁻²) and rechargeability than benchmarked Fumapem FAA-3-50 A-SPE. Postmortem analysis further confirmed the lower formation of ZnO for PSf120, indicating the improved stability and reduced passivation of the zinc electrode. Therefore, this type of A-SPE could improve the performance and rechargeability of all-solid-state ZABs. Full article

Developing low-cost, efficient alternatives to catalysts for bifunctional oxygen electrode catalysis in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical for advancing the practical applications of alkaline fuel cells. In this study, Co particles and single atoms co-loaded on nitrogen-doped carbon (CoNC) were synthesized via pyrolysis of a C₃N₄ and cobalt nitrate mixture at varying temperatures (900, 950, and 1000 °C). The pyrolysis temperature and precursor ratios were found to significantly influence the ORR/OER performance of the resulting catalysts. The optimized CoNC-950 catalyst demonstrated exceptional ORR (E_1/2 = 0.85 V) and OER (E_j10 = 320 mV) activities, surpassing commercial Pt/C + RuO₂-based devices when used in a rechargeable zinc–air battery. This work presents an effective strategy for designing high-performance non-precious metal bifunctional electrocatalysts for alkaline environments. Full article

Rechargeable Zn-air batteries are considered to be an effective energy storage device due to their high energy density, environmental friendliness, and long operating life. Further progress on rechargeable Zn-air batteries with high energy density/power density is greatly needed to satisfy the increasing energy conversion and storage demands. This review summarizes the strategies proposed so far to pursue high-efficiency Zn-air batteries, including the aspects of the electrocatalysts (from noble metals to non-noble metals), the electrode chemistry (from the oxygen evolution reaction to the organic oxidation reaction), electrode engineering (from powdery to free-standing), aqueous electrolytes (from alkaline to non-alkaline) and the battery configuration (from liquid to flexible). An essential evaluation of electrochemistry is highlighted to solve the challenges in boosting the efficiency of rechargeable metal-air batteries. In the end, the perspective on current challenges and future research directions to promote the industrial application of rechargeable Zn-air batteries is provided. Full article

The advancement of cost-effective, high-performance catalysts for both electrochemical oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) is crucial for the widespread implementation of metal–air batteries. In this research, we fabricated leaf-like N-doped carbon frames embedded with Co nanoparticles by pyrolyzing a ZIF-L/carbon nanofiber (ZIF-L/CNF) composite. Consequently, the optimized ZIF-L/CNF-700 catalyst exhibit exceptional catalytic activities in both ORRs and OERs, comparable to the benchmark 20 wt% Pt/C and RuO₂. Addressing the issue of diminished cycle performance in the Zn–air battery cycle process, further detailed investigations into the post-electrolytic composition reveal that both the carbon framework and Co nanoparticles undergo partial oxidation during both OERs and ORRs. Owing to the varying local pH on the catalyst surface due to the consumption and generation of OH⁻ by OERs and ORRs, after OERs, the product is reduced-size Co particles, while after ORRs, the product is outer-layer Co(OH)₂-enveloping Co particles. Full article

Zn–air batteries (ZABs) are a promising technology; however, their commercialization is limited by challenges, including those occurring in the electrolyte, and thus, gel polymer electrolytes (GPEs) and hydrogels have emerged as substitutes for traditional aqueous electrolytes. In this work, PVA/PAA membranes were synthesized by the solvent casting method and soaked in 6 M KOH to act as GPEs. The thickness of the membrane was modified (50, 100, and 150 μm), and after determining the best thickness, the membrane was modified with synthesized SiO₂ nanospheres and multi-walled carbon nanotubes (CNTs). SEM micrographs revealed that the CNTs displayed lengths of tens of micrometers, having a narrow diameter (95 ± 7 nm). In addition, SEM revealed that the SiO₂ nanospheres had homogeneous shapes with sizes of 110 ± 10 nm. Physicochemical experiments revealed that SiO₂ incorporation at 5 wt.% increased the water uptake of the PVA/PAA membrane from 465% to 525% and the ionic conductivity to 170 mS cm⁻¹. The further addition of 0.5 wt.% CNTs did not impact the water uptake but it promoted a porous structure, increasing the power density and the stability, showing three-times-higher rechargeability than the ZAB operated with the PVA/PAA GPE. Full article

The Co-based perovskite La_0.6Sr_0.4CoO₃ has received significant attention as a potential electrocatalyst for its oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to its abundance, facile synthesis, and high oxygen kinetics. However, research on the catalytic performance of Ni-doped La_0.6Sr_0.4Co_1−xNi_xO₃ as a bifunctional cathode catalyst for Zn-air batteries (ZABs) is still scarce. In this work, lanthanum strontium cobalt-based perovskite catalysts with various Ni contents (La_0.6Sr_0.4Co_1−xNi_xO₃, x = 0, 0.2, 0.5, and 0.8) were synthesized using a simple combustion method. The effects of Ni doping on the morphology, structure, surface oxygen-related species, and valence states of the transition metals of the perovskite were characterized. The electrochemical behaviors of the perovskite catalysts in both ORR and OER were also assessed. The characterization results revealed that proper Ni doping can decrease particle size, increase surface oxygen vacancies, and create mixed valence states of the transition metal and, thus, lead to improvement of the electrocatalytic activity of perovskite catalysts. Among the different perovskite compositions, La_0.6Sr_0.4Co_0.8Ni_0.2O₃ exhibited the best ORR/OER activity, with a higher limiting current density, smaller Tafel slope, higher half-wave potential, lower overpotential, and lower potential difference than the other compositions. When La_0.6Sr_0.4Co_0.8Ni_0.2O₃ was applied as the cathodic catalyst in a primary ZAB, it delivered a peak power density of 81 mW cm⁻². Additionally, in rechargeable ZABs, the La_0.6Sr_0.4Co_0.8Ni_0.2O₃ catalyst exhibited a lower voltage gap (0.94 V) and higher stability during charge–discharge cycling than the commonly used catalyst Pt/C. These results indicate that Ni-doped La_0.6Sr_0.4Co_0.8Ni_0.2O₃ is a promising bifunctional electrocatalyst for ZAB. Full article

Rechargeable Zn–air batteries (ZABs) can play a significant role in the transition to a cleaner and more sustainable energy system due to their high theoretical energy density, high cell voltage, and environmental friendliness. ZAB’s air cathode is the principal determinant in predicting the battery’s overall performance, as it is responsible for catalyzing the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during the discharging and charging process, respectively. In this work, a detailed optimization study of the architecture of the air cathode was carried out using the benchmark bifunctional oxygen electrocatalyst (Pt/C-RuO₂). The air cathode composition and architecture were optimized regarding the choice of the commercial gas diffusion layer (GDL), the effect of hot pressing the catalyst layer (CL), and the optimum pore size of the current collector. The best cathode from this study shows a maximum power density (PD_max) of 167 mW/cm², with a round trip efficiency and a voltage gap (E_gap) of 59.8% and 0.78 V, respectively, indicating the air cathodes preparation approach proposed in this work as a promising strategy for the improvement of the overall performance of ZABs. Full article

Rechargeable zinc–air batteries (RZABs) are basically dependent on both affordable and long-lasting bifunctional electrocatalysts. A non-precious metal catalyst, a FeNi nanoalloy catalyst (FeNi@NC) with an extremely low metal consumption (0.06 mmol), has been successfully synthesized. It shows a high half-wave potential of 0.845 V vs. RHE for ORR and a low overpotential of 318 mV for OER at 10 mA cm⁻², favoring a maximum power density of 116 mW cm⁻² for the constructed RZABs. The voltage plateau is reserved even after 167 h of cell operation. The synergistic effect between the nano-sized FeNi alloy and nitrogen-doped carbon with abundant N sites mainly contributes to the electrocatalytic activity. This research can provide some useful guidelines for the development of economic and efficient bifunctional catalysts for RZABs. Full article

Zn-air batteries (ZABs) with neutral electrolytes offer a significantly longer lifespan and better recyclability than alkaline ones. However, low-performance bifunctional catalytic activities for oxygen reduction or evolution reaction (i.e., ORR/OER) in neutral electrolytes still hamper their development. Here, we report iron nanoparticle-decorated nitrogen/boron co-doped reduced graphene oxide aerogel (Fe-NBrGO) with distinguished ORR/OER activity, enabling its application in neutral rechargeable ZABs. Taking advantage of the formation of 3D porous structure of graphene aerogel, N/B-moieties active sites, and Fe-containing active sites, Fe-NBrGO exhibits high ORR onset potential (1.074 and 0.817 V) and adequate OER overpotential (476 and 615 mV) in alkaline and neutral electrolytes, respectively. Fe-NBrGO enables the production of a neutral-ZAB with 34 mW cm⁻² in peak power density and remains stable for a 284 h (~852 cycles) cycling test. This research highlights the rational design of highly active oxygen catalysts for the widespread implementation of new energy storage technologies. Full article

The high activity and reliability of bifunctional oxygen catalysts are imperative for rechargeable metal–air batteries. However, the preparation of bifunctional non–noble metal electrocatalysts with multiple active sites remains a great challenge. Herein, an MOF–derived N–doped C–loaded uniformly dispersed CoO/MoC heterojunction catalyst for high–performance dual function was prepared by a simple “codeposition–pyrolysis” method. Experimental investigations revealed that the formation of the heterojunction can tailor the valence of Co and Mo sites, which impressively modulates the electronic properties of the active sites and promotes the electrocatalytic processes. The optimal catalyst reveals a high–wave half potential (E_1/2 = 0.841 V) for ORR and a low overpotential (E₁₀ = 348 mV) for OER. The NCCM–600–based Zn–air battery displays a high peak power density of 133.36 mW cm⁻² and a prolonged cycling life of more than 650 h. This work provides avenues for the development of functional materials with enhanced properties in a variety of practical energy applications. Full article

Exploring high-efficiency, low-cost, and long-life bifunctional self-supporting electrocatalysts is of great significance for the practical application of advanced rechargeable Zn-air batteries (ZABs), especially flexible solid-state ZABs. Herein, ultrathin CoFe-layered double hydroxide (CoFe-LDH) nanosheets are strongly coupled on the surface of leaf-like bimetallic metal-organic frameworks (MOFs)-derived hybrid carbon (Co@NC) nanoflake nanoarrays supported by carbon cloth (CC) via a facile and scalable method for rechargeable and flexible ZABs. This interfacial engineering for CoFe-LDHs on Co@NC improves the electronic conductivity of CoFe-LDH nanosheets as well as achieves the balance of oxygen evolution reduction (OER) and oxygen reduction reaction (ORR) activity. The unique three-dimensional (3D) open interconnected hierarchical structure facilitates the transport of substances during the electrochemical process while ensuring adequate exposure of OER/ORR active centers. When applied as an additive-free air cathode in rechargeable liquid ZABs, CC/Co@NC/CoFe-LDH-700 demonstrates high open-circuit potential of 1.47 V, maximum power density of 129.3 mW cm⁻², and satisfactory specific capacity of 710.7 mAh g⁻¹_Zn. Further, the flexible all-solid-state ZAB assembled by CC/Co@NC/CoFe-LDH-700 displays gratifying mechanical flexibility and stable cycling performance over 40 h. More significantly, the series-connected flexible ZAB is further verified as a chain power supply for LED strips and performs well throughout the bending process, showing great application prospects in portable and wearable electronics. This work sheds new light on the design of high-performance self-supporting non-precious metal bifunctional electrocatalysts for OER/ORR and air cathodes for rechargeable ZABs. Full article

Aqueous rechargeable zinc (Zn)–air batteries have recently attracted extensive research interest due to their low cost, environmental benignity, safety, and high energy density. However, the sluggish kinetics of oxygen (O₂) evolution reaction (OER) and the oxygen reduction reaction (ORR) of cathode catalysts in the batteries result in the high over-potential that impedes the practical application of Zn–air batteries. Here, we report a stable rechargeable aqueous Zn–air battery by use of a heterogeneous two-dimensional molybdenum sulfide (2D MoS₂) cathode catalyst that consists of a heterogeneous interface and defects-embedded active edge sites. Compared to commercial Pt/C-RuO₂, the low cost MoS₂ cathode catalyst shows decent oxygen evolution and acceptable oxygen reduction catalytic activity. The assembled aqueous Zn–air battery using hybrid MoS₂ catalysts demonstrates a specific capacity of 330 mAh g⁻¹ and a durability of 500 cycles (~180 h) at 0.5 mA cm⁻². In particular, the hybrid MoS₂ catalysts outperform commercial Pt/C in the practically meaningful high-current region (>5 mA cm⁻²). This work paves the way for research on improving the performance of aqueous Zn–air batteries by constructing their own heterogeneous surfaces or interfaces instead of constructing bifunctional catalysts by compounding other materials. Full article

In this article, the performance of brass electrode was investigated in a Zn-air (charcoal-based cathode) rechargeable battery. The construction of the battery was carried out with biodegradable materials, namely a cotton cloth diaphragm and carboxymethyl cellulose sodium salt (CMC-Na) viscosity modifier, while the battery skeleton was printed by 3D printing technology. The brass acted as a collector and a preferable surface for the metallic Zn deposition on the brass anode surface. The electrochemical behavior of the brass anode was investigated by cyclic voltammetry (CV). Cyclic performance tests were carried out, which showed stable cell operation even in the presence or absence of additives up to more than 100 cycles. Furthermore, high energy (E_eff) and Coulomb (C_eff) efficiencies, 80% (E_eff), 95% (C_eff), 75% (E_eff), and 95% (C_eff) were obtained, respectively. The Shepherd model was applied to describe the discharging processes of the Zn-air battery containing brass as anode in the presence of additive-free electrolyte or electrolyte with CMC-Na salt additive. It was found that the Shepherd equation described only approximately the resulting discharge curves. In order to attain a more precise mathematical description, stretched exponential function was implemented into the last term of the Shepherd equation. The need for such a correction shows the complexity of the electrochemical processes occurring in these systems. In addition, the surface of the brass anode was also investigated by scanning electron microscopy (SEM) and the composition of the brass alloys was determined by X-ray fluorescence spectroscopy (XRF). Importantly, the formation of dendritic deposition was successfully suppressed and a smooth and uniform surface was obtained after the cycling tests. Full article

Aqueous rechargeable zinc-ion batteries (ARZIBs) are potential candidates for grid-scale energy storage applications. In addition to its reversible chemistry in aqueous electrolytes, Zn metal is stable in water and air. However, there are critical challenges, such as non-uniform plating, hydrogen evolution, corrosion, and the formation of a passivation layer, which must be addressed before practical applications. In this study, the surface of Zn metal was coated with room-temperature bulk liquid-metal and liquid-metal nanoparticles to facilitate the uniform plating of Zn–ions during cycling. A simple probe ultrasonication method was used to prepare the liquid-metal nanoparticles, and a nanoparticle suspension film was formed through spin coating. At an areal capacity and current density of 0.5 mAh cm⁻² and 0.5 mA cm⁻², respectively, symmetric cells composed of bare Zn metal electrodes were prone to short-circuiting after ~45 h of deposition/striping cycles. However, under the same operating conditions, symmetric cells employing the room-temperature liquid-metal-coated electrodes operated stably for more than 500 h. Compared to the symmetric cell with bare Zn, the symmetric cell with the bulk liquid-metal coated electrode exhibited a significant reduction in the initial nucleation barrier, with respective values of 113.2 and 10.1 mV. Electrochemical characterization of practical full cells also showed significant improvements in the capacity and cycling performance derived from the room-temperature liquid-metal coating. Full article

Integrating a photoelectrode into a zinc-air battery is a promising approach to reducing the overpotential required for charging a metal-air battery by using solar energy. In this work, a photo-fuel cell employing a Nb₂O₅/CdS photoanode and a Zn foil as a counter-electrode worked as a photoelectrochemical battery that saves up to 1.4 V for battery charging. This is the first time a Nb₂O₅-based photoelectrode is reported as a photoanode in a metal-air battery, and the achieved gain is one of the top results reported so far. Furthermore, the cell consumed an organic fuel, supporting the idea of using biomass wastes as a power source for sunlight-assisted charging of metal-air batteries. Thus, this device provides additional environmental benefits and contributes to technologies integrating solar energy conversion and storage. Full article