A review on system and materials for aqueous flexible metal-air batteries

The exploration of aqueous flexible metal-air batteries with high energy density and durability has attracted many research efforts with the demand for portable and wearable electronic devices.Aqueous flexible metal-air batteries feature Earth-abundant materials,environmental friendliness,and operational safety.Each part of one metal-air battery can significantly affect the overall performance.This review starts with the fundamental working principles and the basic battery configurations and then highlights on the common issues and the recent advances in designing high-performance metal electrodes,solid-state electrolytes,and air electrodes.Bifunctional oxygen electrocatalysts with high activity and long-term stability for constructing efficient air electrodes in flexible metal-air batteries are summarized including metal-free carbon-based materials and nonprecious Co/Fe-based materials(alloys,metal oxides,metal sulfites,metal phosphates,metal nitrates,single-site metal-nitrogen-carbon materials,and composites).Finally,a perspective is provided on the existing challenges and possible future research directions in optimizing the performance and lifetime of the flexible aqueous solid-state metal-air batteries.

Recent advances in solid-state metal-air batteries

Solid-state metal-air batteries have emerged as a research hotspot due to their high energy density and high safety.Moreover,side reactions caused by infiltrated gases(O_(2),H_(2)O,or CO_(2))and safety issues caused by liquid electrolyte leakage will be eliminated radically.However,the solid-state metal–air battery is still in its infancy,and many thorny problems still need to be solved,such as the large resistance of the metal/electrolyte interface and catalyst design.This review will summarize some important progress and key issues for solid-state metal-air batteries,especially the lithium-,sodium-,and zinc-based metal-air batteries,clarify some core issues,and forecast the future direction of the solid-state metal-air batteries.

Recent progress in rechargeable alkali metal-air batteries

Rechargeable alkali metal-air batteries are considered as the most promising candidate for the power source of electric vehicles(EVs) due to their high energy density. However, the practical application of metal-air batteries is still challenging. In the past decade, many strategies have been purposed and explored, which promoted the development of metal-air batteries. The reaction mechanisms have been gradually clarified and catalysts have been rationally designed for air cathodes. In this review, we summarize the recent development of alkali metal-air batteries from four parts: metal anodes, electrolytes, air cathodes and reactant gases, wherein we highlight the important achievement in this filed. Finally problems and prospective are discussed towards the future development of alkali metal-air batteries.

Micro-nanostructural designs of bifunctional electrocatalysts for metal-air batteries

Water-based rechargeable metal-air batteries play an important role in the storage and conversion of renewable electric energy.However,the sluggish kinetics of the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)have limited the practical application of rechargeable metal-air batteries.Most of reviews were focused on single functional electrocatalysts while few on bifunctional electrocatalysts.It is indispensable but challenging to design a bifunctional electrocatalyst that is active and stable to the two reactions.Recently,attempts to develop high active bifunctional electrocatalysts for both ORR and OER increase rapidly.Much work is focused on the micro-nano design of advanced structures to improve the performance of bifunctional electrocatalyst.Transition-metal materials,carbon materials and composite materials,and the methods developed to prepare micro-nano structures,such as electrochemical methods,chemical vapor deposition,hydrothermal methods and template methods are reported in literatures.Additionally,many strategies,such as adjustments of electronic structures,oxygen defects,metal-oxygen bonds,interfacial strain,nano composites,heteroatom doping etc.,have been used extensively to design bifunctional electrocatalysts.To well understand the achievements in the recent literatures,this review focuses on the micro-nano structural design of materials,and the related methods and strategies are classed into two groups for the improvement of intrinsic and apparent activities.The fine adjustment of nano structures and an in-depth understanding of the reaction mechanism are also discussed briefly.

Advances in Porous Perovskites:Synthesis and Electrocatalytic Performance in Fuel Cells and Metal-Air Batteries

With a rising energy demand and anabatic environmental crisis arising from the fast growth in human population and society economics,numerous efforts have been devoted to explore and design plentiful multifunctional materials for meeting highefficiency energy transfer processes,which happen in various developed energy conversion and storage systems.As a special kind of multi-metal oxides,perovskite with attractive physical and chemical properties,is becoming a rapidly rising star on the horizon of high-performance catalytic materials with substantial research behaviors worldwide.The porous nanostructure in targeted catalysts is favorable to the catalytic activity and thus improves the overall efficiency of these energy-related installations.In this review paper,recent advances made in the porous perovskite nanostructures for catalyzing several anodic or cathodic reactions in fuel cells and metal-air batteries are comprehensively summarized.Plenty of general preparation methods employed to attain porous perovskite-type oxides are provided,followed by a further discussion about the influence of various strategies on structures and catalytic properties of the porous perovskites.Furthermore,deep insights gathered in the future development of porous perovskite-based materials for energy conversion and storage technologies are also provided.

Defective/Doped Graphene-Based Materials as Cathodes for Metal-Air Batteries

Graphene,as a proof-of-concept two-dimensional material,has proven to have excellent physical and chemical properties.Its derivatives,such as defective or doped graphene,are also applied as catalytic materials for metal-air batteries(MABs).MABs have been recognized as possible candidates for new-generation energy storage systems due to their ultra-high theoretical energy density.So far,graphene and its derivatives with optimized structures have been widely explored to improve the electrochemical performance in MABs.Generally speaking,perfect graphene crystalline is inert for many catalytic processes,while defects and heteroatoms can endow graphene with high activity for many electrocatalytic reactions.Under this circumstance,recent progress is summarized for defective/doped graphene as air cathodes in aqueous or organic MABs,which are actually different electrochemical systems with distinct requirements for air cathodes.Also,the relationship is clarified between graphene defects/doping and electrocatalytic mechanisms that can be the guidance for catalyst design.Future directions are also prospected for the development of graphene-based MAB cathodes.

Self-assembled three-dimensional carbon networks with accessorial Lewis base sites and variational electron characteristics as efficient oxygen reduction reaction catalysts for alkaline metal-air batteries

Heteroatom-doped carbon has been demonstrated to be one of the most promising non-noble metal catalysts with high catalytic activity and stability through the modification of the electronic and geometric structures.In this study,we develop a novel solvent method to prepare interconnected N,S co-doped three-dimensional（3D）carbon networks with tunable nanopores derived from an asso-ciated complex based on melamine and sodium dodecylbenzene sulfonate（SDBS）.After the intro-duction of silica templates and calcination,the catalyst exhibits 3D networks with interconnected 50-nm pores and partial graphitization.With the increase of the number of Lewis base sites caused by the N doping and change of the carbon charge and spin densities caused by the S doping,the designed N,S co-doped catalyst exhibits a similar electrochemical activity to that of the commercial 20-wt%Pt/C as an oxygen reduction reaction catalyst.In addition,in an aluminum-air battery,the proposed catalyst even outperforms the commercial 5-wt%Pt/C catalyst.Both interconnected porous structures and synergistic effects of N and S contribute to the superior catalytic perfor-mance.This study paves the way for the synthesis of various other N-doped and co-doped carbon materials as efficient catalysts in electrochemical energy applications.

One-step,in situ formation of WN-W_(2)C heterojunctions implanted on N doped carbon nanorods as efficient oxygen reduction catalyst for metal-air battery

Transition metal nitrides and carbides have attracted intensive attentions in metal-air battery application due to their metallic electron transport behavior and high chemical stability toward the oxygen reduction reaction(ORR).Herein,the polyoxometalate@polyaniline composite derived WN-W_(2)C heterostructured composite(WN-W_(2)C@pDC)has been fabricated through an in situ nitriding-carbonization strategy,with WN-W_(2)C nanoparticles implanted on N doped carbon nanorods.Asfabricated WN-W_(2)C@pDC demonstrates prominent electrocatalytic performance towards ORR and excellent cycling stability in metal-air battery,which possesses positive half-wave potential and large diffusion limiting current density(0.81 V and 5.8 mA·cm^(-2)).Moreover,it demonstrates high peak power density of 157.4 mW·cm^(-2)as Al-air primary cathode and excellent stability at the discharge-charge test(>500 h)of Zn-air secondary battery.The excellent activity and durability of WNW_(2)C@pDC catalyst should be attributed to the combined effect of intimate WN-W_(2)C heterointerfaces,unique embedded nanoparticles structure,and excellent electrical media of N doped carbon,confirmed by a series of contrast experiments.

Application of metal-organic frameworks,covalent organic frameworks and their derivates for the metal-air batteries

Metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)as the novel porous materials have the merits of diverse,adjustable functionality,high porosity and surface area,which have great application prospects in the gas storage,separation and catalysis.In addition,their derivates make up for the insufficient of electronic conductivity and chemical stability of MOFs and COFs,and provide a new ideal for accurate control of material structure.Up to now,many efficient electrocatalysts have been designed based on MOFs,COFs and their derivates for O_(2)reduction/evolution reactions(ORR/OER)and CO_(2)reduction/evolution reactions(CO_(2)RR/CO_(2)ER)in the metal-air batteries.In this review,the latest development of MOFs,COFs and their derivates in the metal-air batteries is summarized,and we discuss the structural characteristics of these materials and their corresponding mechanisms of action.By comprehensively reviewing the advantages,challenges and prospects of MOFs and COFs,we hope that the organic framework materials will shed more profound insights into the development of electrocatalysis and energy storage in the future.

球形敏感单元微瞄准形成金属/空气/金属微观界面中的电子输运机理研究

针对惯性陀螺和航空、航天发动机等高端/尖端仪器装备中,深孔、沟槽等内腔体结构的高精度测量对非接触传感方法提出的挑战性需求,展开球形敏感单元瞄准被测件形成金属/空气/金属微观界面中的敏感机理研究。从绝缘介质薄层电子输运机理和绝缘介质性质改变而产生电子输运两个角度,对包括电子隧穿在内的电子输运机理进行形成条件和电流密度特性的分析,揭示球形敏感单元微瞄准形成的金属/空气/金属微观界面中,产生传感电流的电子输运主要机理为福勒-诺德海姆隧穿效应,为探索新原理的三维非接触式纳米传感方法奠定了基础。

聚乙烯亚胺/聚丙烯腈复合纤维薄膜的制备及其功能化应用

针对金属-空气电池阴极易腐蚀的问题,将聚乙烯亚胺(PEI)和聚丙烯腈(PAN)共混,基于静电纺丝方法制备PEI/PAN复合纤维薄膜,抑制CO_(2)对空气阴极的侵蚀。借助计算机模拟方法计算PEI/PAN复合纤维薄膜的最佳成分配比,采用扫描电子显微镜、傅里叶变换红外吸收光谱仪、同步热分析仪等对PEI/PAN复合纤维薄膜的物理特性、CO_(2)吸附性能进行表征和分析。以铝-空气电池为例,通过电池测试系统分析了PEI/PAN复合纤维薄膜对电池电化学性能的影响情况。结果表明:基于静电纺丝技术可成功将PEI嵌入PAN纤维中,所制备的PEI/PAN复合纤维薄膜纤维直径均一且表面光滑;当PEI/PAN复合纤维薄膜中的PEI质量分数为50%时,在100 kPa条件下其CO_(2)吸附量可达1.86 mmol/g;在金属-空气电池阴极添加PEI/PAN复合纤维薄膜,相较于传统铝-空气电池,其比容量提升19.5%,放电时间延长20.4%。

煅烧对空气电极的多孔结构和电化学性能的影响

优化空气电极的孔道结构对提升电极的电化学性能至关重要。通过电极多孔结构的重组,可以提高氧气的传输速率,从而实现金属空气电池的高能量密度和长放电寿命。采用扫描电镜、差热分析仪、比表面积测试仪、润湿角测试仪和电化学测试仪等检测技术,研究了不同煅烧温度(200、250、300、350、400℃)对空气电极的表观形貌、微孔结构和电化学性能的影响,并进一步测试了镁基空气电池的放电性能。结果表明,随着煅烧温度升高,电极中黏结剂聚四氟乙烯(PTFE)的纤维熔融状态改变了其微孔结构分布(包括气孔和液孔),从而影响了电极的氧还原电化学性能和放电寿命。尤其在接近PTFE相变点(343℃)的煅烧温度350℃下制备的空气电极,具有均匀的孔径分布和最佳疏水特性(包含疏水点和气体扩散孔道)。因此,空气电极表现出最小电极极化(-0.45 V极化电位下,电极电流密度为159.1 mA/cm^(2))、最长放电寿命(15 mA/cm^(2)电流密度下,放电时长为39.0 h),较大的容量及功率密度(分别为37.4 A·h和13.05 mW/cm^(2))。

金属气囊膨胀性能影响因素研究

金属气囊具有较强的承压能力和良好的气密性、形状稳定性及环境适应性,在各类航天器做动变形及减振抗冲击结构设计中成为行业研究热点。主要研究了气囊膨胀过程中导致断裂或褶皱失稳等现象的关键参数,同时分析了进气口位置和气囊边缘厚度对膨胀效果的影响。采用有限元方法,选用5组常用金属材料参数为基础数据,对材料的密度、弹性模量、泊松比和屈服极限进行正交试验。仿真结果表明,金属气囊最大膨胀高度受材料密度影响最大,极差为8.26 mm;最大褶皱深度受屈服极限影响最大,极差为5.48 mm;褶皱数受屈服极限影响最小,极差仅为0.8个;虽然进气口位置将影响气囊膨胀的均匀性,但会在特定区域达到更大的膨胀高度;虽然提高边缘厚度会增加气囊的强度,但会降低气囊最大膨胀高度。结果可为金属气囊的工程设计提供理论参考。

碳材料/钙钛矿型复合氧化物双功能催化剂在金属-空气电池中应用研究进展

金属-空气电池具有能量密度高、安全性能好、成本低、无污染等优点,是一种很有前途的化学能源存储与转化器件,但其氧还原反应(ORR)和氧析出反应(OER)的动力学缓慢,且依赖于昂贵的贵金属催化剂(例如:Pt或Ir),这都阻碍了其可持续商业化的发展进程。钙钛矿型氧化物因其高的固有催化活性、丰富的种类、低成本和丰富的资源,近年来受到越来越多的关注,并有望成为替代贵金属催化剂的高效ORR和OER催化剂。由于钙钛矿氧化物的固有导电性较低,一般认为需要导电碳来增强钙钛矿电极内部的电子导电性,使钙钛矿的利用率最大化。综述了溶胶凝胶法、化学气相沉淀、水热法、静电纺丝法等碳材料负载钙钛矿型双功能催化剂的制备方法,总结了各制备方法的优缺点。阐述了钙钛矿/碳复合材料双功能催化剂在常见的三种金属-空气电池中的应用研究进展,提出了基于钙钛矿/碳复合材料的高效氧催化剂的合成和发展面临的挑战和未来的方向。

Facile Route to Constructing Ternary Nanoalloy Bifunctional Oxyegn Cathode for Metal-Air Batteries

Highly stable and efficient bifunctional air cathode catalyst is crucial to rechargeable metal-air batteries.Herein,a ternary nanoalloy layer composed of noble and base metal coated on a three-dimensional porous Ni sponge as the bifunctional cathode is synthesized through in-situ anchoring strategy,which can effectively keep the multimetal nanoparticles from agglomeration and improve the density of active sites and catalytic activity.The prepared catalyst displays an excellent catalytic performance with lower overpotential and long-term stability.The Zn-air batteries with the as-prepared cathodes possess a large power density of 170 mW/cm2,long cycling stability up to 230 cycles,and a high specific capacity of 771 mA h/g.Furthermore,the corresponding Li-air batteries deliver a discharge capacity of 22429 mA h/g.These superior properties of the metal-air batteries can be attributed to the combined influence of design and composition of electrode,which is of great significance to improve the electrochemical catalytic activity,providing great potential of wide application in expanded rechargeable energy systems.

Advanced noble-metal-free bifunctional electrocatalysts for metal-air batteries

The sluggish reaction kinetics at the oxygen cathode is one of the important issues hindering the commercialization of the metal-air batteries.Although the noble metal can be used as the high-efficiency electrocatalyst to solve the problems to some extent,the high cost and scarcity of these noble-metal catalysts have limited their application in electrocatalysis.In this review,we discussed the mecha-nisms of the ORR and OER,and proposed the principles for the bifunctional electrocatalysts firstly,and then the state-of-the-art bifunctional catalysts,including carbon-based materials and transition-metal-based materials.On the basis of that,the self-supporting 3D noble-metal-free bifunctional ORR/OER catalysts were also discussed.Finally,the perspectives for the bifunctional electrocatalysts were discussed.

可控构建分级多孔炭载CoP纳米颗粒催化剂用于高效氧还原反应

为金属空气电池等热点能源器件中的阴极氧还原反应(ORR)设计低成本和高效率的无贵金属催化剂仍然是一项巨大的挑战。过渡金属磷化物(TMPs)因其可调的电子结构及优异的催化性能,有望替代贵金属催化剂。本文采用磷化策略(350℃下二次热解),构建了一种在分层多孔炭框架上负载由掺氮炭壳包裹的CoP纳米颗粒催化剂(CoP@NC)。在二次热解过程中,Co纳米颗粒在NaH_(2)PO_(2)生成的PH_(3)气体下原位转化为CoP纳米颗粒,而载体的十二面体结构没有发生改变。在碱性条件下,CoP@NC电催化剂表现出优异的ORR活性,半波电位高达0.92 V,这归因于分散良好的CoP纳米颗粒与炭壳之间的协同耦合以及载体多孔结构实现的高效质量传输。此外,使用CoP@NC组装的锌-空气电池展现出1.51 V的高开路电压和210.1 mW cm^(-2)的功率密度。这项研究将有助于开发低成本和高效率的ORR电催化剂。

金属有机骨架及其衍生材料在电解水和锌-空气电池中的应用

电解水和锌-空气电池(ZABs)技术为解决能源危机、实现碳中和目标开辟了一条新的途径。然而,这些技术的实际应用在很大程度上受到析氢反应(HER)、析氧反应(OER)以及氧还原反应(ORR)缓慢动力学的限制。因此,迫切需要开发高效、稳定的电催化剂有效降低反应过电位,加快电催化反应进程。金属有机骨架(MOFs)由于其灵活可调的组成和精确可控的结构,已成为催化领域研究最广泛的材料之一。本文聚焦于MOFs基电催化剂的制备策略和结构特性,主要介绍它们在电解水和ZABs方面近期的研究进展,并对该领域存在的问题和发展趋势进行了总结和展望。

金属空气预过滤器在某核电站AC厂房的应用

根据某核电站AC厂房送风系统要求和框架文件设计了一种可复用的金属空气预过滤器,与核电站原空气预过滤器的安装方案和运行压差进行了对比。结果表明,运行相同时间后,金属空气预过滤器上游、下游压力和压差上升比例均低于原空气预过滤器,表明金属空气预过滤器运行更稳定。达到终阻力时,金属空气预过滤器可清洗后复用,有良好的应用前景。

不同空气质量下河南主要城市冬季PM_(2.5)中重金属污染特征、来源解析及健康风险评价

为研究不同大气污染水平条件下河南区域PM_(2.5)及其载带金属的浓度特征、来源和健康风险,于2020年12月在河南7个主要城市(郑州市、洛阳市、信阳市、安阳市、新乡市、商丘市、许昌市)采集PM_(2.5)样品,测定并分析了元素Cu、Zn、Pb、Se、Mn、Fe、As、Mo、Ni、Cd、Al.结果表明,PM_(2.5)中的重金属浓度峰值集中在轻度和中度污染空气质量条件,平均浓度顺序Zn>Fe>Al>Mn>Pb>Cu>As>Se>Mo>Cd>Ni.Zn和Fe平均质量浓度分别为118.92 ng·m^(-3)和52.88 ng·m^(-3),两者之和占重金属总浓度的65.88%.重金属富集因子变化趋势与浓度变化趋势相同,Cd元素的富集因子最高(>10),表明主要受人为活动影响.重金属元素的主要污染源为燃烧源和交通源.健康风险评估显示,所有空气质量条件下均为成年男性的致癌风险最大,儿童的非致癌风险最大.空气质量条件为优时,Mo对暴露于环境中1 h的成年男性和成年女性具有潜在致癌风险.