燃料电池不锈钢双极板表面改性研究进展

不锈钢具有良好的导电性和耐蚀性、优异的机械性能和加工性能及较低的成本,是燃料电池双极板传统材料石墨的合适替代材料。然而,不锈钢双极板在燃料电池环境中容易形成钝化膜导致电池性能的减低;此外,在长时间电池运行过程中,不锈钢双极板容易发生腐蚀,其腐蚀产物容易造成催化剂中毒,从而导致电池性能的大幅降低。因此,不锈钢双极板必须经过表面处理或改性,以满足使用性能。本文详细描述了目前不锈钢双极板表面处理的研究现状,并对不锈钢双极板表面处理技术的发展方向做了展望。     

不锈钢金属双极板TiW和TiTa膜的制备及性能

针对质子交换膜燃料电池金属双极板耐蚀性和导电性有待提高的问题,本文用磁控溅射双靶共溅的方法,在316L不锈钢基体表面沉积TiW和TiTa两种非贵金属膜层。通过X射线衍射、扫描电子显微镜-能谱仪、X射线光电子能谱仪、电化学和接触电阻测试等方法,表征了涂覆膜层后不锈钢的微观结构、表面形貌、化学组成、耐腐蚀性和导电性。实验结果表明,磁控溅射制备得到的TiTa膜表面较为均匀,且TiTa膜沉积的不锈钢具有较好的耐腐蚀性,其恒电位极化电流密度能够维持在0.3μA/cm²;从导电性来看,TiW膜与碳纸之间的接触电阻小于TiTa膜。综合考虑材料的各项性能,认为沉积TiTa膜的316L不锈钢有用作金属双极板材料的潜力。     

金属双极板TiCr膜层氯离子腐蚀的研究与模拟

为了研究金属双极板TiCr膜层的氯离子腐蚀规律和机理,采用磁控溅射方法制备以316L不锈钢为基体,TiCr为导电膜层的双极板材料。针对燃料电池和固体聚合物电解水电解池的内部溶液容易被氯离子污染的实际情况,借助电化学极化曲线和交流阻抗谱(EIS),考察了电解质溶液中氯离子浓度对TiCr膜层耐蚀性的影响。并且,通过分子模拟软件对氯离子影响合金膜腐蚀速率的机理进行了动力学模拟。测试和分子模拟结果表明,合金膜的腐蚀速率随氯离子含量的增加而增加,氯离子通过与合金钝化膜表面处金属原子之间的吸附-溶解过程,实现对膜层的加速腐蚀。     

氮气流量对质子交换膜燃料电池316L不锈钢双极板TiN涂层性能的影响

为了提高316L双极板的耐蚀性和导电性，采用多弧离子镀方法在不同氮气流量下制备TiN涂层。使用X射线衍射(XRD)、场发射电子扫描电镜(SEM)、膜电极电阻检测设备、电化学工作站等对所制备的TiN涂层的结构及其性能进行表征。研究结果表明：(1)具有TiN涂层的316L金属双极板比没有涂层的316L不锈钢金属双极板具有能更好的耐蚀性以及导电性。(2)在模拟的质子交换膜燃料电池(PEMFC)阴极环境中随着氮气流量的增加具有TiN涂层的金属双极板的耐蚀性先增强后减小，接触电阻先变大后减小。当氮气流量为200 mL/min时候测的最低的接触电阻为9.62 mΩ/cm²和最低的电流密度5.19×10^-7 A/cm²,极化电阻最大为4.990×10⁴Ω,此时为最佳工艺。     

聚苯胺基涂层在质子交换膜燃料电池金属双极板上的应用进展

聚苯胺具有独特的导电性和电化学性能,近年来随着燃料电池的发展成为双极板防护的重要材料。然而,聚苯胺涂层在质子交换膜燃料电池高温强酸的工作环境中长期耐蚀性仍无法满足要求,限制了该材料的规模应用。本文综述了聚苯胺基涂层在质子交换膜燃料电池双极板上应用的最新研究进展,包括通过掺杂和共聚改性的聚苯胺涂层、引入高分子材料和纳米材料制备的聚苯胺基复合涂层;分析了各类典型涂层的电化学测试性能结果,总结了聚苯胺基复合涂层的耐蚀机理。最后总结了聚苯胺基涂层研究中目前存在的问题,并对研究方向进行了展望,指出统一测试标准对材料性能评价和商业应用具有重要意义,且今后应重点加强纳米材料复合涂层的研究,并基于原位观测和表征技术对涂层机理进行深入解析。     

表面改性金属双极板在直接甲醇燃料电池中的应用

石墨双极板由于制作成本高、易碎等不利因素严重制约直接甲醇燃料电池（DMFC）的发展。表面改性后的金属材料由于具备接触电阻低，加工强度高等优点而受到广泛关注。但是，迄今为止，国内少见改性金属双极板在DMFC中的研究报道。本文分别对金属及其氧化物、导电高分子、碳膜及金属碳化物、金属氮化物作为金属材料表面改性膜层进行了详述。基于改性金属双极板在模拟DMFC运行环境中的腐蚀原理，重点分析了表面改性前后金属双极板的抗腐蚀性能、接触电阻、表面涂层的成分及形态等关键参数，分析比较了改性涂层金属双极板对燃料电池运行中的电化学行为和寿命的影响。展望了表面改性金属双极板在DMFC中应用的研究趋势，为实现DMFC便携式发展奠定了良好的基础。     

锂电池隔膜测试方法评述

隔膜是电池的重要组成部分,其具有电子绝缘性,因此可以隔离正负极,避免出现短路现象;同时具有离子导电性,可以保证电池的电化学性能。正确评价进而科学使用隔膜可以提高电池的综合性能。本文介绍了电池膈膜的主要测试项目及其对锂电池的参考意义,详细叙述了隔膜各个测试项目的现有测试标准及其测试方法,并对现有方法进行了评述,对锂电池隔膜的测试评价方法提供了参考意见。     

石墨复合双极板气密性和导电性的研究进展

针对现今双极板存在的气密性和导电性等性能缺陷,通过文献的分析,总结了近年来强化双极板气密性、导电性的方法。浸渍可以增强石墨双极板的气密性,封堵石墨双极板气孔,减小氢气渗透率。增强复合双极板导电性通过去除双极板表面富集树脂、表面改性构建导电通道和添加导电填料实现。在满足双极板的性能要求情况下,未来需要简化和优化工艺,以低廉的成本实现双极板的大规模生产。     

人造石墨粉制备锂离子电池负极材料的工艺技术研究

为了比较全面地了解以各种人造石墨制品的加工切屑碎为原料制备的锂离子电池负极材料的性能特征,探讨改进其电化学性能的技术方法。本文取5种人造石墨粉制备负极材料,并测试分析其电化学性能。分析认为石墨制品切屑碎均有电化学活性,但因其自身石墨化度、杂质含量以及制粉过程中高强机械研磨导致表面结构缺陷,影响电化学性能。试验结果表明,对接头电极经过清铣表面附着的杂质后的切屑碎整形、球化以及适当的表面改性处理,能够得到与针状焦负极材料性能相近的中高端锂离子电池用负极材料。     

石墨毡原位生长TiN纳米棒及其作为钒电池电极的电化学性能研究

利用水热合成和高温退火方法,将氮化钛纳米棒原位生长在石墨毡表面,成功构建了兼具高催化活性和高导电性的碳纤维复合电极材料。用扫描电子显微镜对复合电极的表面形貌和结构进行了表征。利用接触角测试仪对电极表面的浸润性进行了考察。采用三电极体系并通过小幅电位阶跃法和循环伏安法对电极的电化学表面积和电化学性能进行了分析。最后,通过充放电测试对相应电池性能进行了考察。结果表明,以该复合材料为电极的电池在电流密度为200 mA/cm~2下,能量效率达到了80.23%,比常规电池提升了约7.2%,且电池表现出更优的倍率性能和能量密度。     

A Promising Alternative to PEMFC Graphite Bipolar Plates: Surface Modified Type 304 Stainless Steel with TiN Nanoparticles and Elastic Styrene Butadiene Rubber Particles

In order to utilise inexpensive bipolar plates for proton exchange membrane fuel cells (PEMFC), a surface modification with TiN nanoparticles and elastic styrene butadiene rubber (SBR) particles has been applied to the most widely commercialised stainless steel of type 304 which did not satisfy the required properties in the bare form. The electro‐conducting agglomerates were electrophoretically deposited on the stainless steel bipolar plates. The surface modification greatly improved the corrosion resistance of the stainless steel as well as the interfacial contact resistance (ICR). As a result, the cell performance was significantly enhanced and become comparable to that with graphite bipolar plate during operation for 1,000 h. Ac‐impedance results indicated that the TiN–SBR coating was effective not only in reducing the ICR but also in retaining the resistance low throughout the operation. The hydrophobic character of the TiN–SBR coating on the stainless steel bipolar plates, which facilitated the removal of the formed water in the cathode side during the single cell operation, is also responsible for the enhanced cell performance. Therefore, the type 304 stainless steel bipolar plate modified with the electro‐conducting nanosized TiN – elastic SBR particles is suggested to be a promising substituent for the PEMFC graphite bipolar plate.     

The electrical resistance of flexible graphite as flowfield plate in proton exchange membrane fuel cells

Flexible graphite can be stamped into gas channels for proton exchange membrane fuel cells attributing to its good conductivity, corrosion resistance and flexibility. However, the electrical resistance of the bipolar plate consisting of a coated metal foil and the stamped flexible graphite flowfield plate should be investigated, for the internal resistance would affect the output power of the fuel cell greatly. The influences of various parameters, such as compacting pressure, temperature, effective area of the coating and the water content of the flexible graphite on the electrical resistance were studied. The electrical resistance decreases with the increment of compacting pressure exponentially. The temperature and the effective area of metal foil coating both have linear relations with the electrical resistance. And the water content of the flexible graphite has a very complex relation with the electrical resistance; it is the most important influencing factor. At last, an empirical equation for the electrical resistance, giving a good fit to the test data, was determined.     

Reviewing Metallic PEMFC Bipolar Plates

A bipolar plate is one of the most important components in a polymer exchange membrane fuel cell (PEMFC) stack and has multiple functions. Metallic bipolar plate candidates have advantages over composite rivals in excellent electrical and thermal conductivity, good mechanical strength, high chemical stability, very wide alloy choices, low cost and, most importantly, existing pathways for high‐volume, high‐speed mass production. The challenges with metallic bipolar plates are the higher contact resistance and possible corrosion products, which may contaminate the membrane electrode assembly. This review evaluates the candidate metallic and coating materials for bipolar plates and gives the perspective of the research trends.     

Evaluation of Ni‐Mo and Ni‐Mo‐P Electroplated Coatings on Stainless Steel for PEM Fuel Cells Bipolar Plates

Stainless steel bipolar plates (BPPs) are the preferred choice for proton exchange membrane fuel cells (PEMFCs); however, a surface coating is needed to minimize contact resistance and corrosion. In this paper, Ni–Mo and Ni–Mo–P coatings were electroplated on stainless steel BPPs and investigated by XRD, SEM/EDX, AFM and contact angle measurements. The performance of the BPPs was studied by corrosion and conduction tests and by measuring their interfacial contact resistances (ICRs) ex situ in a PEMFC set‐up at varying clamping pressure, applied current and temperature. The results revealed that the applied coatings significantly reduce the ICR and corrosion rate of stainless steel BPP. All the coatings presented stable performance and the coatings electroplated at 100 mA cm⁻² showed even lower ICR than graphite. The excellent properties of the coatings compared to native oxide film of the bare stainless steel are due to their higher contact angle, crystallinity and roughness, improving hydrophobicity and electrical conductivity. Hence, the electroplated coatings investigated in this study have promising properties for stainless steel BPPs and are potentially good alternatives for the graphite BPP in PEMFC.     

Development of Low‐Cost Advanced Composite Bipolar Plate for Proton Exchange Membrane Fuel Cell�

The bipolar plate is one of the most imperative components of proton exchange membrane fuel cells (PEMFC) which consumes up to 80% of weight and near about 50% of the total cost of the cell. Development of cost‐effective composite bipolar plate with high electrical conductivity and high mechanical strength is both technically and economically demanding. In this paper, a low‐cost advanced composite bipolar plate is developed by bulk moulding compression (BMC) technique. It is clear from the experiments that by increasing the matrix volume fraction, bulk density and electrical conductivity of a composite bipolar plate decrease but shore hardness increases. Test results clearly show that best overall properties are achieved when a constant volume fraction of polymer matrix and natural graphite is reinforced with synthetic graphite, carbon black and carbon fibre. This bipolar plate was found to have high conductivity, less porosity and high mechanical strength. The I–V characteristics in single cell test exhibited more uniform power density at both higher and lower current densities     

Electrochemical corrosion characteristics of type 316 stainless steel in simulated anode environment for PEMFC

The corrosion behavior of type 316 stainless steel in simulated anode environment for proton exchange membrane fuel cell (PEMFC), i.e., dilute hydrochloric acid solutions bubbled with pure hydrogen gas at 80 °C, was investigated by using electrochemical measurement techniques. The main purpose is to offer some fundamental information for the use of stainless steels as bipolar plate material for PEMFC. Both polarization curve and electrochemical impedance spectroscopy (EIS) measurements illustrate that 316 stainless steel cannot passivate spontaneously in the simulated environments. The absorbed (and/or adsorbed) hydrogen atoms from cathodic corrosion reactions on the steel surface may deteriorate the passivity and corrosion resistance. The oxidation of these hydrogen atoms gives rise to a second current peak in the anodic polarization curve, and the current increases with immersion time. EIS spectra also reveal that a porous corrosion product layer formed on the steel surface during the active dissolution in the test solutions. 316 stainless steel exhibits the similar corrosion behavior in sulfate ions containing dilute hydrochloric acid solution.     

Corrosion-resistant lightweight metallic bipolar plates for PEM fuel cells

Corrosion resistant treated metal bipolar plates with higher rigidity and electrical conductivity than graphite were developed and tested for PEM fuel cell applications. Six replicas of single cells were used three of which were made of graphite composites bipolar plates and the other three of the treated metallic plates. A Membrane Electrode Assembly (MEA) with 5.55 cm² active electrode areas, 0.3 mg cm^–2 Pt loading and Nafion membrane 115 was fitted to each cell and operated under identical conditions. The experimental testing was conducted at room temperature (20 °C). The average value of the data obtained for the three graphite cells was plotted. Similarly, the average value of the data obtained for the three treated metal cells was plotted on the same graph for comparison. Generally, the treated metal bipolar plate provided at least 12% saving in hydrogen consumption in comparison to graphite. This is attributed to the lower bulk and surface contact resistance of the metal used in this study in relation to graphite. The results of lifetime testing, conducted at room temperature under variable loading showed no indication of power degradation due to metal corrosion for at least 1500 hours.