Flexible Zn-air Battery Research Articles

From wood to flexible Zn-air Battery: Fe3O4 nanoparticles synergistic single iron atoms on N-doped carbon nanosheets electrocatalyst and Lignosulfonate-Functionalized gel electrolyte

High-efficiency and low-cost electrocatalysts for oxygen reduction reaction (ORR), as well as gel electrolytes with high water retention, mechanical adaptability and zinc dendrites inhibition are required for flexible Zn-air batteries. Herein, abundant cellulose extracted from wood was employed to prepare ORR catalysts consisting of single iron atoms and Fe3O4 nanoparticles embedded within nitrogen-doped carbon nanosheets (SA-FeCNS). The optimized SA-FeCNS-800 demonstrated remarkable ORR catalytic activity, showcasing a half-wave potential of 0.85 V vs. RHE and a diffusion-limiting current of 5.54 mA cm−2 at 0.3 V vs. RHE. Its efficacy was further demonstrated in Zn-air battery technology, where it exhibited superior discharging and charging capabilities, allowing for 618 h of continuous operation at 5 mA cm−2, along with enduring performance at high current densities (10 mA cm−2 and 20 % depth of discharge). Furthermore, a solid-state electrolyte named SLS@PVA-SSE was fabricated utilizing wood’s sodium lignosulfonate-functionalized polyvinyl alcohol hydrogel. This innovation effectively curbed the formation of zinc dendrites and enhanced alkaline resistance, owing to the incorporation of positively charged sulfonate groups. The flexible Zn-air batteries assembled with SA-FeCNS-800 and SLS@PVA-SSE exhibit long cycling life of for 85 h at 2 mA cm−2 and 37 h at 5 mA cm−2. This study offers a sustainable and effective way to make high-performance catalysts and solid electrolytes for advanced flexible energy materials using renewable biomass.

Unsaturated cobalt-nitrogen atomic sites in necklace-like hairy fibers towards highly efficient oxygen electrocatalysis for flexible Zn-Air battery

Exploration of single-atom catalysts (SACs) with high activity and efficient utilization efficiency holds great promise in the field of electrocatalysis. However, it is still a challenge to rationally design the SACs due to their properties are greatly influenced by the local electron environment and the effective substrate. Herein, we synchronously realized the modulation of unsaturated cobalt-nitrogen atomic sites (CoN3) and uniformly archoring them on the carbon-nanotube assembled necklace-like fiber (NLF). The unsaturated cobalt-nitrogen atomic sites with asymmetric structure favor the adsorption/desorption features and promote the electrocatalytic reactions of oxygen. Meanwhile, the hairy NLF fiber with the highly conductive and porous matrix guarantees the active sites accessibility and fast kinetics. In addition, the unique necklace-like configuration endows good mechanical strength and high reliability for the CoN3 NLF fiber. Both density functional theoretical (DFT) calculation and the experimental results reveal its superior catalytic properties and good reliability in the oxygen electrocatalytic reactions. Moreover, the finite element analysis (FEA) and the corresponding tests further certify its high pliability and good robustness. Based on the CoN3 NLF fiber air cathode, the aqueous Zn-air battery (ZAB) delivers a high power density (306 mW cm−2) and outstanding cycling stability over 300 h. Furthermore, all-solid-state ZAB based on the freestanding CoN3 NLF air cathode shows considerable flexibility and superior reliability over a wide range of temperatures (-20∼25 °C). Therefore, this work provides an effective catalyst design for the development of metal-air batteries for diverse applications.

Anchoring Fe Species on the Highly Curved Surface of S and N Co-Doped Carbonaceous Nanosprings for Oxygen Electrocatalysis and a Flexible Zinc-Air Battery.

Oxygen reduction reaction (ORR) is of critical significance in the advancement of fuel cells and zinc-air batteries. The iron-nitrogen (Fe-Nx ) sites exhibited exceptional reactivity towards ORR. However, the task of designing and controlling the local structure of Fe species for high ORR activity and stability remains a challenge. Herein, we have achieved successful immobilization of Fe species onto the highly curved surface of S, N co-doped carbonaceous nanosprings (denoted as FeNS/Fe3 C@CNS). The induction of this twisted configuration within FeNS/Fe3 C@CNS arose from the assembly of chiral templates. For electrocatalytic ORR tests, FeNS/Fe3 C@CNS exhibits a half-wave potential (E1/2 ) of 0.91 V in alkaline medium and a E1/2 of 0.78 V in acidic medium. The Fe single atoms and Fe3 C nanoparticles are coexistent and play as active centers within FeNS/Fe3 C@CNS. The highly curved surface, coupled with S substitution in the coordination layer, served to reduce the energy barrier for ORR, thereby enhancing the intrinsic catalytic activity of the Fe single-atom sites. We also assembled a wearable flexible Zn-air battery using FeNS/Fe3 C@CNS as electrocatalysts. This work provides new insights into the construction of highly curved surfaces within carbon materials, offering high electrocatalytic efficacy and remarkable performance for flexible energy conversion devices.

A twisted carbonaceous nanotube as the air-electrode for flexible Zn-Air batteries.

Exploring electrocatalysts with high-efficiency oxygen reduction reaction (ORR) is significant for practical applications of fuel cells and metal-air batteries. In this work, a twisted core@shell material has been prepared with helical polypyrrole nanotubes (HPPys) as the core and coordination polymers (CPs) as the shell. After the pyrolysis process, a dense twisted carbon layer was formed by the reaction of CP and HPPy at its interface under Ar. The derived twisted carbonaceous nanotube exhibits good performance in both electrocatalytic ORR and OER. When used as the air-electrode in a flexible Zn-air battery, the battery shows good performance and stability.

Pyridinic-N exclusively enriched CNT-encapsulated NiFe interfacial alloy nanoparticles on knitted carbon fiber cloth as bifunctional oxygen catalysts for biaxially flexible zinc–air batteries

A highly reversible bifunctional electrocatalyst for flexible Zn air batteries was fabricated featuring pyridinic-N exclusively enriched CNT encased NiFe interfacial alloy nanoparticles derived from an LDH template on knitted carbon fiber cloth.

The Mott–Schottky Co2P/Co heterocatalyst encapsulated by N,P-doped graphene/carbon nanotubes as high-efficiency trifunctional electrocatalysts for cable-type flexible Zn–air batteries and water splitting

The novel Mott–Schottky Co2P/Co encapsulated by N,P co-doped graphene and carbon nanotubes is prepared and employed it as superior catalyst for zinc–air batteries and water splitting application, making it a noteworthy advancement in the field.

Wood-derived Fe cluster-reinforced asymmetric single-atom catalysts and weather-resistant organohydrogel for wide-temperature flexible Zn–air batteries

All wood-based wide-temperature flexible Zn–air battery.

In-situ spatial-embedding construction of FeCo nucleus-bound carbon skeletons for durable rechargeable liquid and flexible Zn-air batteries

In-situ spatial-embedding construction of FeCo nucleus-bound carbon skeletons for durable rechargeable liquid and flexible Zn-air batteries

Design and synthesis of self-supporting FeCoNi- and N-doped carbon fibers/nanotubes as oxygen bifunctional catalysts for solid-state flexible Zn-air batteries

Developing effective bifunctional electrocatalysts with efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) capabilities is critical to advancing rechargeable zinc-air batteries. This study harnessed the properties of organic salts in polymer solutions via electrospinning to synthesize self-supporting flexible bifunctional electrocatalysts, termed FeCoNi flexible carbon nanofibers (FeCoNi FCNFs). These catalysts benefitted from the secondary growth of FeCoNi- and N-doped carbon nanotubes on fiber surfaces, generating numerous metal-nitrogen-carbon (M−N−C) ORR active sites and FeCoNi alloy-based OER active sites. At 10 mA/cm2, FeCoNi FCNFs exhibited a half-wave potential of 0.92 V for ORR and 1.64 V for OER. Density functional theory calculations based on first principles demonstrated that FeCoNi FCNFs possessed superior bifunctional activity. Moreover, rechargeable liquid Zn-air batteries constructed with this catalyst achieved a high peak power density and exceptional cycling stability lasting over 630 h. Additionally, a solid-state wearable battery using this catalyst displayed outstanding cycle stability, continuously cycling for over 27 h. This research offers both insight and a fresh approach for designing efficient, cost-effective bifunctional solid-state or liquid zinc-air batteries.

Heteroatom anchors Fe-Mn dual-atom catalysts with bi-functional oxygen catalytic activity for low-temperature rechargeable flexible Zn-air batteries

M−N−C (M = Fe, Co, Ni, etc.) catalyst owns high catalytic activity in the oxygen catalytic reaction which is the most likely to replace the Pt-based catalysts. But it is still a challenge to further increase the active site density. This article constructs the high-efficiency FeMn-N/S-C-1000 catalyst to realize ORR/OER bifunctional catalysis by hetero-atom, bimetal (Fe, Mn) doped simultaneously strategy. When evaluated it as bi-functional electro-catalysts, FeMn-N/S-C-1000 exhibits excellent catalytic activity (E1/2 = 0.924 V, Ej=10 = 1.617 V) in alkaline media, outperforms conventional Pt/C, RuO2 and most non-precious-metal catalysts reported recently. Such outstanding performance is owing to N, S co-coordinated with metal to form multi-types of single atom, dual atom active sites to carry out bi-catalysis. Importantly, nitrite poison test provides the proof that the active sites of FeMn-N/S-C are more than that of single-atom catalysts to promote catalytic reactions directly. To better understand the local structure of Fe and Mn active sites, XAS and DFT were employed to reveal that FeMn-N5/S-C site plays the key role during catalysis. Notably, the FeMn-N/S-C-1000 based low-temperature rechargeable flexible Zn-air also exhibits superior discharge performance and extraordinary durability at −40 °C. This work will provide a new idea to design diatomic catalysts applied in low-temperature rechargeable batteries.

Engineering of heterointerface of ultrathin carbon nanosheet-supported CoN/MnO enhances oxygen electrocatalysis for rechargeable Zn–air batteries

Designing bifunctional electrocatalysts with outstanding reactivity and durability towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has remained a long-term aim for metal-air batteries. Achieving the high level of fusion between two distinct metal components to form bifunctional catalysts with optimized heterointerfaces and well-defined morphology holds noteworthy implications in the enhancement of electrocatalytic activity yet challenging. Herein, the fabrication of numerous heterointerfaces of CoN/MnO is successfully realized within ultrathin carbon nanosheets via a feasible self-templating synthesis strategy. Experimental results and theoretic calculations verify that the interfacial electron transfer from CoN to MnO at the heterointerface engenders an ameliorated charge transfer velocity, finely tuned energy barriers concerning reaction intermediates and ultimately accelerated reaction kinetics. The as-prepared CoN/MnO@NC demonstrates exceptional bifunctional catalytic performance, excelling in both OER and ORR showcasing a low reversible overpotential of 0.69 V. Furthermore, rechargeable liquid and quasi-solid-state flexible Zn-air batteries employing CoN/MnO@NC as the air-cathode deliver remarkable endurance and elevated power density, registering values of 153 and 116 mW cm−2 respectively and exceeding Pt/C + RuO2 counterparts and those reported in literature. Deeply exploring the effect of electron-accumulated heterointerfaces on catalytic activity would contribute wisdom to the development of bifunctional electrocatalysts for rechargeable metal-air batteries.

In-situ polymerization of the electrolyte on the electrode surface: A novel process to eliminate interfacial impedance in flexible Zn-air batteries

Flexible rechargeable quasi-solid-state metal air/O2 batteries are advanced energy sources for wearable and flexible electronic devices. This study proposes an in-situ polymerization of gel electrolyte on the electrode surface (IPEES) technique for the Zn-air battery. The utilization of the IPEES technique for batteries results in superior battery performance as compared to conventional layer-by-layer batteries. The enhanced performance can be credited to several factors, including a reduction in charge transfer resistance and bulk resistance, an increase in ion conductivity, improved water retention, and the establishment of a robust and stable interface between the electrolyte and cathode. The battery with the poly(acrylic acid) gel using the IPEES technique results in a charge-discharge process of 171 h at 1 mA cm−2, while the specific capacity (SC) and power density (PD) of the battery are 72.86 mAh cm−2 and 88.88 mW cm−2, respectively. The novel IPEES method yields an increase of up to 78.6 % in specific capacity compared to the conventional method. At a current density of 10 mA cm−2, the highest values of SC and PD are attained, reaching 83.85 mAh cm−2 and 90.6 mW cm−2, respectively. The novel method exhibits exceptional electrochemical performances and offers additional benefits such as affordability and high mechanical stability.

Dual-Ligand Strategy to Construct Metal Organic Gel Catalyst with the Optimized Electronic Structure for High-Efficiency Overall Water Splitting and Flexible Metal-Air Battery.

Non-noble metal catalysts are known for their efficient catalytic performance for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Metal organic gels (MOGs) can be considered as a promising electrocatalyst owing to the diverse physicochemical properties but usually suffer from its poor electrical conductivity and catalytic stability. Here, a FeCo-MOG is constructed with considerable trifunctional activity. The optimal P-CoFe-H3 prepared by using phytic acid (PA) and 2,4,6-Tris[(p-carboxyphenyl)amino]-1,3,5-triazine benzoic acid (H3TATAB) as dual ligands), exhibits outstanding ORR, OER, and HER activities as well as stability, exceeding most of state-of-the-art catalysts. As expected, the flexible Zn-air battery applied with P-CoFe-H3 as air cathode displays considerable power density, discharge voltage plateau, and cycling stability. Impressively, it is also capable of driving the overall water-splitting device by applying the P-CoFe-H3 as anode and cathode. Furthermore, theoretical calculations reveal that dual ligands can optimize the coordination environment and charge density of active sites, thereby reducing the absorption energy of intermediate species and boosting the catalytic performance. This work endows the dual-ligands coordination strategy with great potentiality for MOGs-based electrocatalysts in energy conversion devices.

Collaborative integration of Fe-Nx active center into defective sulfur/selenium-doped carbon for efficient oxygen electrocatalysts in liquid and flexible Zn-air batteries

Strategic active site organization is imperative for the advancement of effective and long-lasting catalysts of oxygen reduction reactions. However, the controllable multi-active site design is a highly intricate topic for catalyst synthesis. Employing pre-trapping and post-activation strategy, Fe-N bonding structure and S, Se functionalized heteroatom are integrated into a conductive porous carbon. In this process, the nitrogen-abundant polymer 1,3,5-triformylbenzene-tris(4-aminophenyl)benzene (Tf-TAPA) adsorbs Fe3+ under the intrinsically metal anchoring ability of N atoms and simultaneously in-situ assembles long-chain thiophene-S. Subsequently, the Fe3+ is transformed into Fe-Nx moieties with the conversion of the organic chain to incompletely graphitized carbon. Furthermore, the alteration of the electronic configuration achieved through the introduction of dual-atom S and Se leads to a pronounced enhancement in catalytic efficiency. Benefitting from the Fe-Nx bonding structure, dense structural defects, and conductive carbon networks, the resultant Fe-S,Se/NCNs possesses a positive half-wave potential of 0.86 V and a 90% current retention rate, outstripping the Pt/C benchmark. Moreover, the liquid and flexible ZAB driven by Fe-S,Se/NCNs achieves large power densities of 259.7 and 164.7 mW/cm2, respectively. This study provides a new comprehension in developing an efficient and stable M-N-C oxygen electrocatalyst.

Constructing FeS and ZnS Heterojunction on N,S-Codoped Carbon as Robust Electrocatalyst toward Oxygen Reduction Reaction.

Highly active and cost-efficient electrocatalysts for oxygen reduction reaction (ORR) are significant for developing renewable energy conversion devices. Herein, a nanocomposite Fe/ZnS-SNC electrocatalyst with an FeS and ZnS heterojunction on N,S-codoped carbon has been fabricated via a facile one-step sulfonating of the pre-designed Zn- and Fe-organic frameworks. Benefitting from the electron transfer from FeS to adjacent ZnS at the heterointerfaces, the optimized Fe/ZnS-SNC900 catalyst exhibits excellent ORR performances, featuring the half-wave potentials of 0.94 V and 0.81 V in alkaline and acidic media, respectively, which is competitive with the commercial 20 wt.% Pt/C (0.87 and 0.76 V). The flexible Zn-air battery equipping Fe/ZnS-SNC900 affords a higher open-circuit voltage (1.45 V) and power density of 30.2 mW cm-2. Fuel cells assembled with Fe/ZnS-SNC900 as cathodic catalysts deliver a higher power output of 388.3 and 242.8 mW cm-2 in H2-O2 and -air conditions. This work proposes advanced heterostructured ORR electrocatalysts that effectively promote renewable energy conversions.

Constructing Fe-N4 Sites through Anion Exchange-mediated Transformation of Fe Coordination Environments in Hierarchical Carbon Support for Efficient Oxygen Reduction.

Metal single atoms (SAs) anchored in carbon support via coordinating with N atoms are efficient active sites to oxygen reduction reaction (ORR). However, rational design of single atom catalysts with highly exposed active sites is challenging and urgently desirable. Herein, an anion exchange strategy is presented to fabricate Fe-N4 moieties anchored in hierarchical carbon nanoplates composed of hollow carbon spheres (Fe-SA/N-HCS). With the coordinating O atoms are substituted by N atoms, Fe SAs with Fe-O4 configuration are transformed into the ones with Fe-N4 configuration during the thermal activation process. Insights into the evolution of central atoms demonstrate that the SAs with specific coordination environment can be obtained by modulating in situ anion exchange process. The strategy produces a large quantity of electrochemical accessible site and high utilization rate of Fe-N4 . Fe-SA/N-HCS shows excellent ORR electrocatalytic performance with half-wave potential of 0.91 V (vs. RHE) in 0.1 M KOH, and outstanding performance when used in rechargeable aqueous and flexible Zn-air batteries. The evolution pathway for SAs demonstrated in this work offers a novel strategy to design SACs with various coordination environment and enhanced electrocatalytic activity.

Ice-Template-Induced Highly Interconnected Porous Polymer Gel Electrolytes for Dendrite-Free Flexible Zinc-Air Batteries.

Improving the performance of quasi-solid-state gel polymer electrolytes is critical for addressing issues at the Zn anode-electrolyte interface of high-performance flexible Zn-air batteries (FZABs). In this study, a highly interconnected porous poly(vinyl alcohol)/poly(ethylene glycol) (PVA/PEG) hydrogel electrolyte was fabricated via an ice-crystal template for FZABs. The mechanical toughness and stability of the gel electrolytes can be reinforced by the formation of a PEG-PVA cross-linking network. The three-dimensional PVA/PEG porous skeleton greatly increased electrolyte uptake and accelerated ion transport, leading to high ionic conductivity (42.5 mS cm-1). In-situ synchrotron radiation X-ray imaging revealed that the PVA/PEG network can effectively inhibit dendrite growth and the hydrogen evolution reaction. The assembled FZABs exhibited superior cycle stability, high power density (109 mW cm-3), and excellent flexibility and structural stability under bending conditions, thus showing great potential for future applications in flexible and wearable electronic device technologies.

A promising approach to prepare gel electrolyte and electrocatalyst derived from natural long-staple cotton for high-performance flexible Zn-air battery

Due to the high energy density and risk-free operation, flexible zinc–air batteries (ZABs) have the potential to be energy sources for wearable electronic devices. Nonetheless, the performance of quasi-solid-state gel electrolytes diminishes progressively throughout the ion-exchange process, primarily due to water evaporation on the exposed cathode side, which shortens the useful lifetime of ZABs. Herein, we propose a distinctive gel polymer electrolyte membrane comprising cotton fiber (CF) from natural long-staple cotton and polyvinyl acetate (PVA) to effectively extend the battery lifespan, which is due to that the addition of CF improves surface wettability, liquid absorption and retention, and ionic conductivity (1.53 × 10−2 S cm−1) compared with single PVA electrolyte membrane. We also prepare a composite electrocatalyst (Co-N-C@GCF-950) by pyrolyzing the precursor of ZIF-67 in situ grown on the cotton fiber at 950 ℃. The flexible ZAB assembled with Co-N-C@GCF-950 as the cathode electrocatalyst and the CF-PVA membrane as the gel electrolyte shows a high open-circuit voltage of 1.5 V, and a stable charge-discharge voltage gap of 0.8 V for 11-h lifespan at a current density of 2 mA cm−2 under various bending conditions, which guides the future way of the application potential of environmental cotton fibers in the multiaspects for flexible metal-air batteries.

N, S co-doped hollow carbon nanocages confined Fe, Co bimetallic sites for bifunctional oxygen electrocatalysis

Regulating pore architecture and electronic structure is of significance for improving oxygen electrocatalytic activity of M−N−C catalysts. Herein, N, S co-doped hollow carbon nanocages confined Fe, Co bimetallic sites (FeCo-NS-HNCs) are constructed through an efficient surface bridging strategy. The surface modifier of trithiocyanuric acid trisodium salt bridges Co doped ZIF-8 surface with Fe ions to promote the formation of Fe/Co-Nx sites. The synergistic coupling of metal sites and N, S co-doping manipulates the adsorption/desorption characteristics of M−Nx sites to optimize intrinsic activity. The Kirkendall effect constructs the hollow carbon nanocages, improving the accessibility of M−Nx sites. Benefiting from the ameliorated electronic structure and hollow porous architecture, FeCo-NS-HNCs displays excellent bifunctional oxygen electrocatalytic activity (ΔE = 0.655 V). The liquid and flexible Zn-air batteries of FeCo-NS-HNCs offer prominent power density and cycling stability. This work provides estimable insights into the structure design and activity regulation of M−N−C catalysts for Zn-air battery.

Job-synergistic engineering from Fe3N/Fe sites and sharp-edge effect of hollow star-shaped nitrogen-doped carbon structure for high-performance zinc-air batteries

Due to the limited sources, high cost, and poor long-term stability of noble metal catalysts, the large-scale commercial application of zinc-air batteries has been restricted. Therefore, designing non-noble metal catalysts with excellent activity and stability for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) blossoms in the ascendant. Herein, we report a hollow star-shaped dual-functional electrocatalyst with uniform and dispersed Fe3N/Fe nanoparticles derived from zeolitic imidazolate framework (ZIFs) by a simple sacrificial template strategy. This hollow structure has the characteristics of low density, thin shell, and high permeability, and its internal cavity not only provides additional three-phase interfaces to accelerate O2 reduction and evolution but also promotes the diffusion of reactants onto the catalyst. By controlling the input amount of iron metal salt, the dispersion degree of FeNP can be effectively adjusted, and the generated Fe3N introduces abundant Fe-NX active sites. Density functional theory calculations show that the strong affinity between Fe3N and FeNP is favorable for promoting the oxygen intermediate reaction, achieving a job-synergistic catalytic effect and high reaction kinetics. The synthesized Fe3N/FeNP-N-C-3.3% exhibits excellent dual-functional activity for OER and ORR, with a high half-wave potential of 0.867 V for ORR (better than the commercial Pt/C of 0.82 V) and an overpotential of only 294 mV for OER at 10 mA cm−2. The rechargeable Zn-air battery prepared with Fe3N/FeNP-N-C-3.3% as an air cathode shows a long-term cycling performance of over 750 h and a maximum power density of 205 mW cm−2. The flexible Zn-air battery has a high open-circuit voltage of 1.48 V and a maximum power density of 52.6 mW cm−2, showing glamorous commercial prospects.