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.

Rational Design of Ruddlesden-Popper Perovskite Ferrites as Air Electrode for Highly Active and Durable Reversible Protonic Ceramic Cells

Reversible protonic ceramic cells(RePCCs)hold promise for efficient energy storage,but their practicality is hindered by a lack of high-performance air electrode materials.Ruddlesden-Popper perovskite Sr_(3)Fe_(2)O_(7−δ)(SF)exhibits superior proton uptake and rapid ionic conduction,boosting activity.However,excessive proton uptake during RePCC operation degrades SF’s crystal structure,impacting durability.This study introduces a novel A/B-sites co-substitution strategy for modifying air electrodes,incorporating Sr-deficiency and Nb-substitution to create Sr_(2.8)Fe_(1.8)Nb_(0.2)O_(7−δ)(D-SFN).Nb stabilizes SF’s crystal,curbing excessive phase formation,and Sr-deficiency boosts oxygen vacancy concentration,optimizing oxygen transport.The D-SFN electrode demonstrates outstanding activity and durability,achieving a peak power density of 596 mW cm^(−2)in fuel cell mode and a current density of−1.19 A cm^(−2)in electrolysis mode at 1.3 V,650℃,with excellent cycling durability.This approach holds the potential for advancing robust and efficient air electrodes in RePCCs for renewable energy storage.

Self-supported metal(Fe, Co, Ni)-embedded nitrogen-doping carbon nanorod framework as trifunctional electrode for flexible Zn-air batteries and switchable water electrolysis

To meet the practical demand of wearable/portable electronics, developing high-efficiency and durable multifunctional catalyst and in-situ assembling catalysts into electrodes with flexible features are urgently needed but challenging. Herein, we report a simple route to fabricate bendable multifunctional electrodes by in-situ carbonization of metal ion absorbed polyaniline precursor. Alloy nanoparticles encapsulated in graphite layer are uniformly distributed in the N-doping carbon nanorod skeleton. Profiting from the favorable free-standing structure and the cooperative effect of metallic nanoparticles, graphitic layer and N doped-carbon architecture, the trifunctional electrodes exhibit prominent activities and stability toward HER, OER and ORR. Notably, due to the protection of carbon layer, the electrocatalysts show the reversible catalytic HER/OER properties. The overall water splitting device can continuously work for 12 h under frequent exchanges of cathode and anode. Importantly, the bendable metal air batteries fabricated by self-supported electrode not only displays the outstanding battery performance,achieving a decent peak power density(125 mW cm^(-2)) and exhibiting favorable charge-discharge durability of 22 h, but also holds superb flexible stability. Specially, a lightweight self-driven water splitting unit is demonstrated with stable hydrogen production.

Deciphering the lithium storage chemistry in flexible carbon fiber-based self-supportive electrodes

Flexible carbon fiber cloth(CFC)is an important scaffold and/or current collector for active materials in the development of flexible self-supportive electrode materials(SSEMs),especially in lithium-ion batteries.However,during the intercalation of Li ions into the matrix of CFC(below 0.5 V vs.Li/Li+),the incompatibility in the capacity of the CFC,when used directly as an anode material or as a current collector for active materials,leads to difficulty in the estimation of its actual contribution.To address this issue,we prepared Ni_(5)P_(4)nanosheets on CFC(denoted CFC@Ni_(5)P_(4))and investigated the contribution of CFC in the CFC@Ni_(5)P_(4)by comparing to the powder Ni_(5)P_(4)nanosheets traditionally coated on a copper foil(CuF)(denoted P-Ni_(5)P_(4)).At a current density of 0.4 mA cm^(−2),the as-prepared CFC@Ni_(5)P_(4)showed an areal capacity of 7.38 mAh cm^(−2),which is significantly higher than that of the PNi_(5)P_(4)electrode.More importantly,theoretical studies revealed that the CFC has a high Li adsorption energy that contributes to the low Li-ion diffusion energy barrier of the Ni_(5)P_(4)due to the strong interaction between the CFC and Ni_(5)P_(4),leading to the superior Li-ion storage performance of the CFC@Ni_(5)P_(4)over the pristine Ni_(5)P_(4)sample.This present work unveils the underlying mechanism leading to the achievement of high performance in SSEMs.

Effect of surface free energy of acetylene black powder on air electrode performance

The effects of acetylene black powder surface free energy on air electrode electrochemical performance and lifetime were studied. The acetylene black was immersed in 30% H2O2 at room temperature and the changes of functional groups and surface free energy were investigated by X-ray Photoelectron Spectroscopy (XPS) and powder contact angle (CA). The air electrode performance was characterized by the potential polarization curves and the lifetime was measured by constant-current discharge. It shows that, its surface free energy is the lowest when the acetylene black is immersed in H2O2 for 240 h. The polarization potential of the air electrode prepared by the pretreated acetylene black is 0.25 V(vs. Hg/HgO), 0.21 V lower than the air electrode with untreated acetylene black when the working current density is 100 mA·cm-1. And its lifetime is over 800 h at 80 mA·cm-1. The pretreatment of acetylene black for proper time by H2O2 is favorable for the stability of the tri-phase reaction interface of air electrode and improvement of its performance.

Elementary Investigation of Increasing Polarization Performance of Air Electrode for CO_2 Transfer

Air electrodes are the key components of Electrochemical carbon dioxide concentrating(EDC) cells. Therefore, the improvement of the polarization performance is beneficial to the increasing of CO 2 transfer and cell stability .The preparing process of air electrode is improved by means of the pretreatment of active carbon(AC) and the selection of preparing method of platinum/carbon(Pt/C) powders. Besides, based on the analysis of orthogonal test results, the optimum preparing conditions of Pt/C powders in air electrode are achieved, that is, hydrazine hydrate concentration is 5%～10%, platinum capacity is 8mg/cm 2, chloroplatinic acid concentration is 10.0mg/ml and water both temperature is 40℃.

High-Entropy Perovskite Oxide: A New Opportunity for Developing Highly Active and Durable Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

Reversible proton ceramic electrochemical cell(R-PCEC)is regarded as the most promising energy conversion device,which can realize efficient mutual conversion of electrical and chemical energy and to solve the problem of large-scale energy storage.However,the development of robust electrodes with high catalytic activity is the main bottleneck for the commercialization of R-PCECs.Here,a novel type of high-entropy perovskite oxide consisting of six equimolar metals in the A-site,Pr_(1/6)La_(1/6)Nd_(1/6)Ba_(1/6)Sr_(1/6)Ca_(1/6)CoO_(3−δ)(PLN-BSCC),is reported as a high-performance bifunctional air electrode for R-PCEC.By harnessing the unique functionalities of multiple ele-ments,high-entropy perovskite oxide can be anticipated to accelerate reaction rates in both fuel cell and electrolysis modes.Especially,an R-PCEC utilizing the PLNBSCC air electrode achieves exceptional electrochemical performances,demonstrating a peak power density of 1.21 W cm^(−2)for the fuel cell,while simultaneously obtaining an astonishing current density of−1.95 A cm^(−2)at an electrolysis voltage of 1.3 V and a temperature of 600℃.The significantly enhanced electrochemical performance and durability of the PLNBSCC air electrode is attributed mainly to the high electrons/ions conductivity,fast hydration reactivity and high configurational entropy.This research explores to a new avenue to develop optimally active and stable air electrodes for R-PCECs.

Air Electrode Supported Manganese Electrocatalysts for Neutral Electrolyte Magnesium Air Cell

X The catalysts of air electrode were prepared by sintering the active carbon loaded with manganese nitrate and potassium permanganate at 360 ℃ . The air electrode was made up of a catalyst layer, a waterproof and gas-permeable layer, a current collecting substrate and a second wa-terproof and gas-permeable layer. The cell was assembled by the air electrode, pure magnesium anode and 10% NaCl solution used as electrolyte. The microstructures of air electrodes before and after discharging were characterized by SEM. The electrochemical behaviors of the air electrodes were determined by means of polarization curves, volt-ampere curves and constant current discharge curves. The polarization voltage of air electrode is-173 mV （vs SCE） at the current density of 50 mA/cm2. The air electrodes exhibits good activity and stability in neutral electrolyte. The magnesium-air cell could work at 5 W for more than 7 h.

Mesoscopic numerical computation model of air-diffusion electrode of metal/air batteries

This work creates a droplet battery model based on the electrolyte performance in the porous electrode, studies the current density on the mesoscopic scale, and explains how the mesoscopic structure of the porous electrode influences the current density on the air-diffusion electrode. Near the three-phase line, there is a strong band containing nearly 80% current. For porous electrodes, the total current is proportional to the length of the strong band. Thus, it can be inferred that on the macroscopic scale, the longer the total length of the strong band on unit area is, the larger the current density is.

Studies of Several Systems with Air Electrode Electro-Synthesizing H_2O_2 on the Spot for Degr ading Aniline in Aqueous

A gas diffusion electrode (air electrode) with a high current efficiency of electro\|synthesizing H 2 O 2 using O 2 in air was prepared. The several systems with air electrode as cathode of ele ctro\|synthesizing H 2 O 2 on the reaction spot for degrading aniline in aqueous--electro\|Fenton system, photo\|excitation electro\|H 2 O 2 system and photo\|electro\|Fenton system, were developed. Th e rates of decomposition of H 2 O 2 and mineralization of anil ine were experimentally measured respectively under different conditions, and th e results indicated there has an excellent parallel relation between decompositi on rate of H 2 O 2 and mineralization rate of aniline. Especia lly, photo\|electro\|Fenton system, where H 2 O 2 is decompose d the fastest, is the best system of oxidizing and degrading organic toxicants. Compared photo\|electro\|Fenton system with photo\|Fenton system, important role is revealed in the interface of air electrode. In this paper, the mineralizatio n mechanism of aniline in the photo\|electro\|Fenton system was also discussed.

A Method of Using a Carbon Fiber Spiral-Contact Electrode to Achieve Atmospheric Pressure Glow Discharge in Air

During discharge, appropriately changing the development paths of electron avalanches and increasing the number of initial electrons can effectively inhibit the formation of filamentary discharge. Based on the aforementioned phenomenon, we propose a method of using microdischarge electrodes to produce a macroscopic discharge phenomenon. In the form of an asymmetric structure composed of a carbon fiber electrode, an electrode structure of carbon fiber spiral-contact type is designed to achieve an atmospheric pressure glow discharge in air, which is characterized by low discharge voltage, low energy consumption, good diffusion and less ozone generation.

Metal Free Polymer/Graphite Electrode-Ferricyanides Catholyte System for MFC with High Performance

A Microbial fuel cell(MFC)with metal free polymer/graphite electrodes(150 mm×150 mm)was constructed.The electrodes with flowing channels,which were different in roughness,were designed.No additional catalyst was coated on the electrode,therefore the MFC was cheaper and possessed good durability with high performance.The effect of roughness,K3Fe(CN)6 concentration and sprayed air on the performance of the constructed MFC was investigated.Results showed that the roughness of electrode can significantly affect the performance of MFC.The power density of MFC increased by 1.56 times owing to the arithmetic mean roughness which has increased by 1.41 times.With an increasing K3Fe(CN)6 concentration,the performance of MFC also improves.The MFC with K3Fe(CN)6 only(30 mM)showed the highest power density of 1260 mW/m2,which is by 21.4 times and 1.3 times higher than those of MFCs with spraying air only(59 mW/m2)and with K3Fe(CN)6+air(1005 mW/m2),respectively.This showed that the appropriate concentration of K3Fe(CN)6 can significantly improve the power density,while the air has a negative effect when it is sprayed onto K3Fe(CN)6 catholyte.A coulombic efficiency of 34.2%and an energy efficiency of 13.3%with a COD degradation rate of 73.5%were achieved with MFC using K3Fe(CN)6 only.The overpotentials of MFC were also calculated.It can be seen that both theηohmic andηconcentration were very low as compared to theηactivation,and theηconcentration can be ignored because its effect was less than 3 mV.The theoretical calculation suggested that with an increasing conversion rate of K3Fe(CN)6,the cathode potential decreased and reached 0.31 V at a conversion rate of 0.99.While the anode behaves differently for constant pH and changeable pH as the reaction progresses,which reveals that the buffer solution and removal of protons play an important role in maintaining the anode potential.

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.

棒电极直径和端部形状对短空气间隙交流击穿电压的影响研究

空气间隙交流击穿特性试验常采用棒棒、棒板电极作为试验电极,目前棒电极直径、棒端部形状对空气间隙交流击穿电压的影响尚不清晰。为此,用直径2 cm、1 cm的圆棒和直径1 cm的尖棒搭建棒棒、棒板电极,开展5~40 cm短空气间隙下的交流击穿试验,研究棒电极直径和端部形状对空气间隙交流击穿电压的影响。结果表明:在试验棒电极直径和端部形状范围内,空气间隙距离5~20 cm时,各棒棒或棒板电极空气间隙击穿电压相对偏差在5.93%~33%之间,随着空气间隙距离增大,棒电极直径和端部形状对棒棒、棒板空气间隙击穿电压的影响逐渐减弱;空气间隙距离大于20 cm时,各棒棒或棒板电极空气间隙击穿电压相对偏差均小于5%。研究认为,空气间隙距离超过20 cm时,棒电极直径和端部形状对棒棒、棒板空气间隙击穿电压无影响。

由乙烯焦油调制石墨电极用浸渍剂沥青

以乙烯焦油为原料,采用空气氧化法调制石墨电极用浸渍剂沥青。考察了氧化温度、氧化时间和空气流速对所制浸渍剂沥青物化性质的影响,并与煤系浸渍剂沥青进行比较。实验还采用激光解析质谱、傅里叶变换红外光谱、核磁共振、元素分析和旋转流变仪等表征手段对浸渍剂沥青的理化性质进行分析。结果表明,在乙烯焦油改性过程中,影响浸渍剂沥青物化性质的主要因素依次为:氧化温度>空气流速>氧化时间,较高的氧化温度有利于提高所制浸渍剂沥青的结焦值;较短的氧化时间和较低的空气流速能降低所制浸渍剂沥青的软化点,其相对较低的软化点有助于浸渍过程中的流动性。在氧化温度、氧化时间和空气流速分别为310℃、4 h和0.2 L/min的最佳制备条件下,所制浸渍剂沥青软化点、结焦值分别为93.44℃、46.73%(以质量分数表示),喹啉不溶物(QI)质量分数低于0.1%,并且S、N和O等杂原子的含量很低,具有更好的流动性,有望达到良好的浸渍效果。

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))。

固体氧化物电池空气电极铬中毒机理及抗铬性能研究进展

固体氧化物电池(SOC)具有能源利用率高、污染排放量低、燃料灵活性高等优势,将在未来的能源供应和储存中发挥关键作用。当前,其长期稳定性尚不能满足大规模商业化的需求,电池堆中用于串联电池的金属连接体所导致的空气电极“铬中毒”是电堆性能衰减的重要因素之一。传统空气电极在发电模式(SOFC)下的铬中毒机理已较为明晰。然而,随着电解模式(SOEC)下应用的不断攀升,基于传统电极材料的毒化机理不适用于该运行模式下的电极体系。对典型空气电极材料在SOFC模式和SOEC模式下铬中毒机理进行对比分析,并且对提高SOC空气电极抗铬性能的研究进行总结和展望。

Large-Area Gravure-Printed AgNWs Electrode on Water/Oxygen Barrier Substrate for Long-Term Stable Large-Area Flexible Organic Solar Cells

Large-area AgNWs electrodes(25 cm×10 cm)were fabricated through roll-to-roll printing on the polyvinyl alcohol(PVA)modified water and oxygen barrier substrate.The modification of the barrier film with PVA improved the wettability of silver nanowires on the barrier films and led to the formation of homogenous large-area AgNWs networks.The mechanical flexibility,especially the adhesion force between the silver electrode and the barrier film substrate was dramatically improved through PVA modification.The efficiency of 13.51%for the flexible OSCs with an area of 0.64 cm2 was achieved based on the PET/barrier film/PVA/AgNWs electrode.The long-term stability showed the flexible OSCs based on the PET/barrier film/PVA/AgNWs electrode have a significantly improved stability relative to the device on PET/AgNWs electrode,and comparable air stability as the rigid device with glass/ITO device.The unencapsulated devices maintained nearly 50%of the original efficiency after storage for 600 h in air.After a simple top encapsulation,the flexible devices remained at 60%of the initial efficiency after 2000 h in the air.Therefore,the flexible AgNWs electrode based on the barrier film would have the potential to improve the air storage stability of organic flexible solar cells.

40 t超级电弧炉应用实践

电弧炉炼钢具有流程短、绿色、节能等特点,是今后钢铁工业可循环、绿色化发展的重要路径。某公司通过多年的自主创新和技术沉淀,攻克了多电极分控调节、直流电源输出功率实时交互协同调控的瓶颈,开发了新型超高功率柔性IGBT直流电源和柔性直流高效供电技术,并结合电炉本体、针式底阳极等新技术,形成了新一代高效、低耗、绿色环保的超级电弧炉技术和装备。本文介绍了超级电弧炉本体装备、柔性直流电源和风冷底电极的技术特点,以及在某厂40 t电弧炉的改造应用情况。工业生产实践表明,超级电弧炉可有效缩短冶炼周期7 min,减少通电时间5 min,降低冶炼电耗13 kW·h/t钢锭,减少电极消耗1.8 kg/t钢锭,提高金属收得率2.34%,生产成本明显降低,产品质量也得到提高。

活性炭强化泡沫钛基空气扩散电极电过臭氧氧化及降解布洛芬效能

为了提高传统污水处理技术对布洛芬这一新型污染物的去除效率,本研究构建了一种基于活性炭强化的泡沫钛空气扩散电极(AC@Ti-F GDE)的电过臭氧处理体系。该体系通过增强传统电过臭氧体系的氧化效能,用于布洛芬的去除。结果表明,相对于传统的电极(Ti-F),微孔泡沫钛空气扩散电极(Ti-F GDE)体系中的HO•相对含量提升了155.7%。在投加活性炭后,AC@Ti-F GDE体系中的HO•相对含量在Ti-F GDE体系的基础上进一步提升了35.4%。这种显著提升的HO•产量得益于AC@Ti-F GDE体系中H2O2的增加,从而进一步强化了电过臭氧的氧化效能。通过精确调控活性炭的投加密度和颗粒粒径,确定了AC@Ti-F GDE电过臭氧体系中最佳的活性炭投加密度为0.8 mg/cm^(3),最佳颗粒粒径为850μm。在此基础上,将AC@Ti-F GDE电过臭氧体系应用于布洛芬污染物的处理,通过对比不同因素下该体系降解布洛芬的程度,得到最佳运行条件:pH值为7.00,电流为150 mA,O3,gas浓度为52.2 mg/L,并采用液相质谱检测布洛芬降解过程中中间产物,得出了该体系的降解矿化机理:布洛芬首先通过羟基化、去甲基化和脱羧等反应逐步氧化支链,随后攻击苯环并开环生成脂肪酸,最终被进一步矿化生成CO_(2)和H_(2)O。AC@Ti-F GDE电过臭氧新体系,强化了传统电过臭氧体系氧化效能,为后续电过臭氧处理布洛芬提供新思路。