Flexible Rechargeable Zn-air Batteries Research Articles

High-Performance Bifunctional Electrocatalysts for Flexible and Rechargeable Zn-Air Batteries: Recent Advances.

Flexible rechargeable Zn-air batteries (FZABs) exhibit high energy density, ultra-thin, lightweight, green, and safe features, and are considered as one of the ideal power sources for flexible wearable electronics. However, the slow and high overpotential oxygen reaction at the air cathode has become one of the key factors restricting the development of FZABs. The improvement of activity and stability of bifunctional catalysts has become a top priority. At the same time, FZABs should maintain the battery performance under different bending and twisting conditions, and the design of the overall structure of FZABs is also important. Based on the understanding of the three typical configurations and working principles of FZABs, this work highlights two common strategies for applying bifunctional catalysts to FZABs: 1) powder-based flexible air cathode and 2) flexible self-supported air cathode. It summarizes the recent advances in bifunctional oxygen electrocatalysts and explores the various types of catalyst structures as well as the related mechanistic understanding. Based on the latest catalyst research advances, this paper introduces and discusses various structure modulation strategies and expects to guide the synthesis and preparation of efficient bifunctional catalysts. Finally, the current status and challenges of bifunctional catalyst research in FZABs are summarized.

FeNx/ZnSe/Fe Heterojunctions Embedded in Leafy N-Doped Carbon as Efficient Bifunctional Oxygen Electrocatalysts for Flexible Rechargeable Zn–Air Batteries

FeN_<i>x</i>/ZnSe/Fe Heterojunctions Embedded in Leafy N-Doped Carbon as Efficient Bifunctional Oxygen Electrocatalysts for Flexible Rechargeable Zn–Air Batteries

Boosting the electrocatalytic activity of single atom iron catalysts through sulfur-doping engineering for liquid and flexible rechargeable Zn–air batteries

A practical strategy is reported to design single-Fe atom decorated S/N-doped C (Fe SAs@S/N–C) catalysts with a high Fe loading of 5.45 wt%. The prepared catalysts exhibit excellent performances for liquid and all-solid-state Zn–air batteries.

Chemical fabrication and synergistic mechanism of N-doped carbon modified with FeP as catalysts for flexible rechargeable Zn–air batteries

A 3D porous N-doping Paulownia-derived carbon modified with FeP nanoparticles (FeP@NPW) was used as an air cathode for flexible rechargeable Zn–air batteries. The flexible rechargeable ZAB based on FeP@NPW exhibits outstanding cycle stability and durability.

Coupling MnS and CoS Nanocrystals on Self-Supported Porous N-doped Carbon Nanofibers to Enhance Oxygen Electrocatalytic Performance for Flexible Zn-Air Batteries.

Seeking highly efficient, stable, and cost-effective bifunctional electrocatalysts of rechargeable Zn-air batteries (ZABs) is the top-priority for developing new generation portable electronic devices. For this, the rational and effective structural design, interface engineering, and electron recombination on electrocatalysts should be taken into account to reduce the reaction overpotential and expedite the kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we construct a MnCo-based metal organic framework-derived heterogeneous MnS-CoS nanocrystals, which are anchored on free-standing porous N-doped carbon fibers (PNCFs) by the in situ growth method and vulcanization process. Benefiting from the abundant vacancies and active sites, strong interfacial coupling as well as favorable conductivity, the MnS-CoS/PNCFs composite electrode delivers a mentionable oxygen electrocatalytic activity and stability with a half-wave potential of 0.81 V for ORR and an overpotential of 350 mV for OER in the alkaline medium. Of note, the flexible rechargeable ZAB using MnS-CoS/PNCFs as binder-free air cathode offers high power density of 86.7 mW cm-2, large specific capacity of 563 mA h g-1, and adapts to different bending degree of operation. In addition, the density functional theory calculation clarifies that the heterogeneous MnS-CoS nanocrystals reduces the reaction barrier and enhances the conductivity of the catalyst and the adsorption capacity of the intermediates during the ORR and OER process. This study opens up a new insight to the design of the self-supported air cathode for flexible electronic devices.

CoSe2 nanoparticles anchored on CoNC carbon nanoplates as bifunctional electrocatalyst for flexible rechargeable Zn-air batteries

A flexible solid rechargeable Zn-air battery for advanced energy conversion and storage has extensive applications in portable electric sources, wildlife rescue and flexible wearable systems. Herein, the CoSe2 nanoparticles anchored on cobalt-embedded N-doping carbon nanoplates (CoSe2/CoNC) is developed as a highly active bifunctional catalyst via pyrolysis and selenization of bimetallic zeolitic imidazolate frameworks containing Zn and Co. The introduction of inactive Zn generates strong electrochemically active surface areas due to the synergistic effect between CoSe2 nanoparticles and CoNC matrix. Further, CoSe2/CoNC exhibits prominent Zn–air battery performance and even outperforms the commercially available noble-metal catalysts. Notably, a high-rate flexible Zn-air battery enabled by an alkaline composite polyacrylic acid-carboxymethyl cellulose electrolyte delivers the open-circuit potential of 1.51 V. The battery offers high wearability and performs very well under various conditions, such as soaking, drilling and sewing.

Aerophilic Triphase Interface Tuned by Carbon Dots Driving Durable and Flexible Rechargeable Zn-Air Batteries

HighlightsOxygen-respirable sponge was constructed by carbon dots-assisted synthesis strategy.The hydrophilicity and aerophilicity of Co@C–O–Cs active sites boost oxygen diffusion and the bifunctional oxygen reduction reaction and oxygen evolution reaction activities.Co@C–O–Cs-based Zn-air battery (ZAB) displays excellent specific capacity and stability, and the all-solid-state Co@C–O–Cs-based ZAB exhibits excellent flexibility.

3D Co3O4‐RuO2 Hollow Spheres with Abundant Interfaces as Advanced Trifunctional Electrocatalyst for Water‐Splitting and Flexible Zn–Air Battery

AbstractExploiting efficient and stable electrocatalysts with trifunctional catalytic activity toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) act has a crucial role with sustainable energy development. Therefore, this study fabricates Co3O4‐RuO2 hollow spheres using a facile and eco‐friendly solvothermal and low temperature oxidation procedure followed by ice water treatment (IW‐Co3O4‐RuO2‐HS). The specific hollow nanostructure could provide sufficient active sites and channels in the electrocatalytic procedure. Then, the IW‐Co3O4‐RuO2‐HS presents small overpotentials toward HER (40 mV@ 10 mA cm−2) and OER (250 mV@ 10 mA cm−2), and high half‐wave potential for ORR (E1/2@ 0.79 V). Remarkably, the IW‐Co3O4‐RuO2‐HS also presents superior catalytic performances toward water‐splitting and flexible rechargeable Zn–air batteries. Furthermore, the water electrolysis can be driven by sustainable energy, including solar, wind, thermal energy, and the assembled flexible rechargeable Zn–air battery. This study provides a valid path to synthesize multifunctional electrocatalysts on energy‐related devices.

CoNi nanoalloy-Co-N4 composite active sites embedded in hierarchical porous carbon as bi-functional catalysts for flexible Zn-air battery

Exploiting bifunctional electrocatalysts with excellent activity and stability towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of great importance for the practical application of rechargeable metal–air batteries. Herein, we report a novel bimetallic-ion co-exchange combined pyrolysis strategy using bio-MOF-1 as the self-template to synthesize NiCo nanoalloy-Co-N4 embedded hierarchical porous carbon (CoNi-CoN4-HPC-900), which endows good electrical conductivity, large surface area and rich highly-dispersed CoNi-CoN4 active sites identified from X-ray absorption spectroscopy, resulting in outstanding electrocatalytic activity for both ORR and OER in alkaline solution. In situ Raman spectroscopy testifys that the electrocatalytic processes occur via the redox of Co(Ni)(II and Ⅲ) species. Density functional theory calculations are performed to study the ORR and OER activity on the CoNi-CoN4 and CoN4 active sites. The CoNi-CoN4-HPC-900 endows a flexible rechargeable Zn-air battery with an open circuit voltage of 1.50 V and a peak power density of 116 mW cm−2, and excellent flexibility and cycling stability as a cathode. This bimetallic-ion-coexchange strategy of MOFs gives an effective methodology involving bimetallic-ion-coexchange strategy to design and prepare bifunctional electroctalysts in metal-air batteries but also brings an intensive insight into ORR and OER fundamentals.

Optimizing the Spin States of Mesoporous Co3O4 Nanorods through Vanadium Doping for Long-Lasting and Flexible Rechargeable Zn–Air Batteries

Optimizing the Spin States of Mesoporous Co₃O₄ Nanorods through Vanadium Doping for Long-Lasting and Flexible Rechargeable Zn–Air Batteries

Pd nanocluster-decorated CoFe composite supported on nitrogen carbon nanotubes as a high-performance trifunctional electrocatalyst

Rational design and synthesis of low-cost trifunctional electrocatalysts with improved stability and superior electrocatalytic activity for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are highly desirable but remain as the bottlenecks at the current state of technology. In this paper, the cobalt-iron (Co–Fe) composite supported on nitrogen-doped carbon nanotubes (CoFe composite/NCNTs) is synthesized. The intrinsic OER and HER catalytic activities of this CoFe composite/NCNTs composite are significantly improved with palladium (Pd) nanocluster decoration [Pd-coated (CoFe composite/NCNTs)]. The as-prepared Pd-coated (CoFe composite/NCNTs) catalyst exhibits excellent trifunctional electrocatalytic activity and stability due to the interfacial coupling between Pd and (CoFe composite/NCNTs). This catalyst is successfully employed in the water electrolysis cell as both OER and HER electrode catalysts, flexible rechargeable Zn-air battery as the bifunctional ORR and OER electrode catalyst. The cell voltage of this catalyst-coated electrodes requires only 1.60 V to achieve 10 mA cm−2 current density for water electrolysis cell, which is comparable to and even better than that of Pt/C and Ir/C based cell. The primary Zn-air battery using this catalyst shows a constant high open-circuit voltage (OCV) of 1.47 V and a maximum power density of 261 mW cm−2 in the flooded mode configuration. Most importantly, a flexible Zn-air battery with this catalyst runs very smoothly without a change in voltage gap during flat, bending, and twisting positions.

Single‐Atom Catalysts: Atomically Dispersed Cobalt Trifunctional Electrocatalysts with Tailored Coordination Environment for Flexible Rechargeable Zn–Air Battery and Self‐Driven Water Splitting (Adv. Energy Mater. 48/2020)

Single‐Atom Catalysts: Atomically Dispersed Cobalt Trifunctional Electrocatalysts with Tailored Coordination Environment for Flexible Rechargeable Zn–Air Battery and Self‐Driven Water Splitting (Adv. Energy Mater. 48/2020)

A facile controlled synthesis of 3D cobalt nanoparticle-embedded nitrogen-doped carbon materials towards efficient bifunctional electrocatalysts for rechargeable Zn-air batteries

Rational morphology engineering of bifunctional catalysts for air electrode is desperately urgent for Zn-air batteries (ZABs). This work reports a type of three-dimensional (3D) carbon materials, comprising cobalt nanoparticle-embedded nitrogen-doped carbon nanotubes grown on carbon nanosheets (termed as Co@NC-0.1),. The resulting Co@NC-0.1 can synchronously accelerate the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), representing a preponderant universal catalytic activity and outstanding stability in alkaline electrolyte. Such a remarkable performance is mainly credited to considerable specific surface area, high pore volume, well-dispersed copious active sites (especially efficient Co-Nx moieties) and the synergy of a close contact between cobalt nanoparticles and carbon frameworks. Accordingly, a Co@NC-0.1 driven liquid rechargeable ZAB can achieve well-qualified assembly, including a confined discharge–charge voltage gap of 0.85 V at 20 mA cm−2 and well-maintained cycling stability beyond 200 h. More attractively, Co@NC-0.1 is also utilized as a cathode catalyst for button-type and flexible rechargeable ZABs, which performs respectable performances. Undoubtedly, this finding provides a simple tactic for allowing one to construct advanced 3D bifunctional catalyst toward affordable catalysis and future energy conversion technologies.

Atomically Dispersed Cobalt Trifunctional Electrocatalysts with Tailored Coordination Environment for Flexible Rechargeable Zn–Air Battery and Self‐Driven Water Splitting

AbstractDesigning multifunctional catalysts with high activity, stability, and low‐cost for energy storage and conversion is a significant challenge. Herein, a trifunctional electrocatalyst is synthesized by anchoring individually dispersed Co atoms on N and S codoped hollow carbon spheres (CoSA/N,S‐HCS), which exhibits outstanding catalytic activity and stability for the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction. When equipped in liquid or flexible solid‐state rechargeable Zn–air batteries, CoSA/N,S‐HCS endows them with high power and energy density as well as excellent long‐term cycling stability, outperforming benchmark batteries based on a commercial Pt/C + RuO2 dual catalyst system. Furthermore, a self‐driven water splitting system powered by flexible Zn–air batteries is demonstrated using CoSA/N,S‐HCS as the sole catalyst, giving a high H2 evolution rate of 184 mmol h−1. The state‐of‐art experimental characterizations and theoretical calculations reveal synergistic cooperation between atomically dispersed CoN4 active sites, nearby electron‐donating S dopants, and the unique carbon support to single‐atom catalysts (SACs). This work demonstrates a general strategy to design various multifunctional SAC systems with a tailored coordination environment.

Bifunctional air electrodes for flexible rechargeable Zn-air batteries

Flexible rechargeable Zn-air batteries are considered as one of the most promising battery systems to drive flexible and wearable electronic devices owing to their high safety, high gravimetric energy density, low self-discharge and low cost. One of the key challenges is to develop air electrodes with high performance and high mechanical flexibility. This minireview discusses the recent progress in the design and fabrication of flexible air electrodes. It focuses on the latest innovations in bifunctional oxygen reduction reaction and oxygen evolution reaction electrocatalysts, mainly including carbon-based materials (e.g., heteroatom-doped carbon, metal-nitrogen moieties doped carbon), metal oxides (e.g., spinel oxides, perovskite oxides) and their composites. It aims to provide an insight into the structure-property relationship of bifunctional catalysts. We also discuss the challenges and future perspectives.

N-Doped-carbon/cobalt-nanoparticle/N-doped-carbon multi-layer sandwich nanohybrids derived from cobalt MOFs having 3D molecular structures as bifunctional electrocatalysts for on-chip solid-state Zn-air batteries.

The unsatisfactory energy efficiency and leakable liquid electrolytes in conventional Zn-air batteries with intrinsic semi-open structures greatly limit their opportunity to be a safe micropower source for flexible/wearable electronics. Herein, N-doped-carbon/cobalt-nanoparticle/N-doped-carbon (NdC-CoNP-NdC) multi-layer sandwich nanohybrids were first synthesized via the pyrolysis of a well-designed Co-MOF precursor with a 3D molecular framework. Profiting from the synergistic effect enabled by the interlayer-confined growth of monodispersed cobalt nanoparticles having high activity/stability and a thousand-layer-cake porous N-self-doped carbon skeleton of high conductivity and additional active sites as well as the reasonable design of a multi-layer sandwich interface structure between them that acts as an interconnected nanoreactor, the as-obtained NdC-CoNP-NdC multi-layer sandwich nanohybrids exhibit excellent bifunctional catalytic activity of a small ORR/OER gap (0.83 V). We followed a planar electrode configuration design with an interdigital carbon cloth coated with NdC-CoNP-NdC as the air cathode and an interdigital Zn foil as the metal anode as well as the introduction of a polyacrylamide-co-polyacrylic/6 M KOH alkaline gel as an incombustible solid-state electrolyte. Thus, on-chip all-solid-state rechargeable Zn-air batteries (OAR-ZABs) are further developed, achieving a cycle life up to 150 cycles per 50 h, high power density/specific capacity as much as 57.0 mW cm-2/771 mA h g-1, respectively, and excellent coplanar integration capability and mechanical flexibility for working steadily under bending deformation. Eventually, as an additional advancement, an autonomous smartwatch powered by the coplanar integrated OAR-ZABs is demonstrated, which possesses excellent integrity and flexibility and is comfortably wearable for timing and step counting dynamically; this demonstrates the successful application of assembling OAR-ZABs into highly integrated wearable electronics as a compatible micropower source.

A new strategy for engineering a hierarchical porous carbon-anchored Fe single-atom electrocatalyst and the insights into its bifunctional catalysis for flexible rechargeable Zn–air batteries

A promising “confined recrystallization” method is developed for the fabrication of an Fe single-atom bifunctional catalyst for flexible rechargeable Zn–air batteries.

In-situ enriching active sites on co-doped Fe-Co4N@N-C nanosheet array as air cathode for flexible rechargeable Zn-air batteries

The sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics in air cathode severely refrain the development of the reversible Zn-air battery. Herein, we report the design and synthesis of co-doped Fe-Co4N@N-C nanosheet array derived from MOF precursor on carbon cloth as the dual-functional electrocatalyst to boost the reaction kinetics. The Fe, N co-doping significantly promotes the generation of abundant Pyridinic-N-M active sites for ORR due to the strong coordination effect between metal center and pyridinic nitrogen. The enriched Co3+ sites concurrently motivate the formation of targeted *OOH intermediates during OER with decreased charge transfer resistance. Such electrocatalyst therefore delivers high catalytic activity for both ORR and OER. When applied as air cathode for liquid Zn-air battery, the device exhibits a high specific energy density of 934 Wh kg−1 with excellent cycling stability, which is superior to the referenced Pt and Ru-based Zn-air batteries. Flexible solid-state Zn-air battery can also achieve a high volumetric power density of 72 mW cm-3 and good cycling durability under different bending states. This work gives a facile and cost-efficient strategy to construct bifunctional flexible electrode with enriched active sites for Zn-air batteries.

Co Nanoislands Rooted on Co-N-C Nanosheets as Efficient Oxygen Electrocatalyst for Zn-Air Batteries.

Developing non-precious-metal bifunctional oxygen reduction and evolution reaction (ORR/OER) catalysts is a major task for promoting the reaction efficiency of Zn-air batteries. Co-based catalysts have been regarded as promising ORR and OER catalysts owing to the multivalence characteristic of cobalt element. Herein, the synthesis of Co nanoislands rooted on Co-N-C nanosheets supported by carbon felts (Co/Co-N-C) is reported. Co nanosheets rooted on the carbon felt derived from electrodeposition are applied as the self-template and cobalt source. The synergistic effect of metal Co islands with OER activity and Co-N-C nanosheets with superior ORR performance leads to good bifuctional catalytic performances. Wavelet transform extended X-ray absorption fine spectroscopy and X-ray photoelectron spectroscopy certify the formation of Co (mainly Co0 ) and the Co-N-C (mainly Co2+ and Co3+ ) structure. As the air-cathode, the assembled aqueous Zn-air battery exhibits a small charge-discharge voltage gap (0.82 V@10 mA cm-2 ) and high power density of 132 mW cm-2 , outperforming the commercial Pt/C catalyst. Additionally, the cable flexible rechargeable Zn-air battery exhibits excellent bendable and durability. Density functional theory calculation is combined with operando X-ray absorption spectroscopy to further elucidate the active sites of oxygen reactions at the Co/Co-N-C cathode in Zn-air battery.

Two‐Step Activated Carbon Cloth with Oxygen‐Rich Functional Groups as a High‐Performance Additive‐Free Air Electrode for Flexible Zinc–Air Batteries

AbstractA flexible air electrode (FAE) with both high oxygen electrocatalytic activity and excellent flexibility is the key to the performance of various flexible devices, such as Zn–air batteries. A facile two‐step method, mild acid oxidation followed by air calcination that directly activates commercial carbon cloth (CC) to generate uniform nanoporous and super hydrophilic surface structures with optimized oxygen‐rich functional groups and an enhanced surface area, is presented here. Impressively, this two‐step activated CC (CC‐AC) exhibits superior oxygen electrocatalytic activity and durability, outperforming the oxygen‐doped carbon materials reported to date. Especially, CC‐AC delivers an oxygen evolution reaction (OER) overpotential of 360 mV at 10 mA cm−2 in 1 m KOH, which is among the best performances of metal‐free OER electrocatalysts. The practical application of CC‐AC is presented via its use as an FAE in a flexible rechargeable Zn–air battery. The bendable battery achieves a high open circuit voltage of 1.37 V, a remarkable peak power density of 52.3 mW cm−3 at 77.5 mA cm−3, good cycling performance with a small charge–discharge voltage gap of 0.98 V and high flexibility. This study provides a new approach to the design and construction of high‐performance self‐supported metal‐free electrodes.