PEMFC电堆动态工况响应性能试验

质子交换膜燃料电池（PEMFC）电堆动态响应特性对PEMFC电堆的耐久性和可靠性具有很大影响。本文试验考察了PEMFC电堆在动态工况下的输出性能、单电池电压均衡性变化和动态响应特性。结果表明,在整个动态运行工况下,电堆运行良好,进出口冷却液温差小于5℃。电流阶跃变化时电堆电压均衡性出现突增变化,同时随着电流的增大,稳态时电堆均衡性变差。在超负荷（200A）运行工况下,电堆各单电池之间输出差异变大,均衡性持续变差,电堆中间和前端单电池电压明显降低。此外,在整个动态响应过程中电流阶跃上升时的电压最大下冲值比电流阶跃下降时的电压最大上调量大,但输出电压能在10s内达到相对稳定的状态（电压波动率＜0.02）。通过该研究,以期为实际车载电堆运行和控制优化提供参考。     

高温质子交换膜燃料电池电堆稳定性分析与优化

高温质子交换膜燃料电池（HT-PEMFC）应用前景广阔,但是目前HT-PEMFC电堆寿命较短。为此,本文对一个百瓦级空冷HT-PEMFC电堆的稳定性进行了研究。恒电流测试结果发现电堆中间位置单电池电压的衰减速率是两端的5～10倍。XRD、TEM测试结果表明电堆不同位置单电池催化剂Pt粒径变化较小,而极板吸酸量滴定与欧姆极化损失分析结果表明中间位置单电池磷酸流失速率是两端的2～3倍,导致其内阻是两端的5～8倍,膜中磷酸的流失迁移至电极导致氧增益电压比两端增加41～102mV。综上,电堆中间位置单电池磷酸流失过快是导致电堆寿命缩短的主要原因,而电堆温度分布不均则是磷酸流失过快的主要原因。因此,若要提高电堆的寿命,关键要从电堆磷酸与热的管理方面进行优化。     

1.5 kW质子交换膜燃料电池堆动态工况响应特性

考察了自制1.5 kW质子交换膜燃料电池(PEMFC)电堆在动态工况下的性能。研究了PEMFC电堆电压、功率、反应参数随车载工况运行出现的响应情况。发现在大电流密度下,由于各单电池的差异,电堆电压和功率出现比较明显的波动现象。在选定两个工况周期中,电堆各单电池电压的差异系数C_V最大达到4.23%,最高单电池电压和最低单电池电压相差0.106 V。数据分析表明在该动态工况下,PEMFC电堆的动态响应特性受到反应物和电堆温度变化、空气局部流量过大或不足以及电堆内部阳极和阴极出现明显压降等因素的影响。该研究不仅为后续耐久性测试提供分析依据,还对PEMFC电堆实际车载运行参数与控制策略的优化具有指导意义。     

低氢气计量比下车载工况燃料电池电堆耐久性研究

考察了1.9 k W质子交换膜燃料电池电堆在低氢气化学计量比,电流快速连续变载条件下的耐久性。在244 h工况运行后,在电流密度为800 m A×cm-2的条件下,电堆单电池平均电压从0.616 V下降到0.464 V,衰退率为0.623m V×h~(-1),由此可见电堆出现快速性能衰退。在实验过程中,车载工况使得电堆阴阳极进气压力以及进气温度出现明显波动,从而导致膜电极组件(MEA)遭受周期性的机械应力与热应力冲击。此外,在氢气化学计量比为1.05条件下,电流快速连续加载会导致供气系统响应迟缓,气体供应不及时,甚至导致燃料局部供应不足,这可加剧载体碳腐蚀。极化曲线、循环伏安法(CV)测试、电化学交流阻抗谱(EIS)表征发现,电化学活性面积的下降引起了电堆的快速、不可逆的衰退。扫描电子显微镜(SEM)、透射电子显微镜(TEM)表征显示阳极催化层厚度变薄,阴阳极催化剂颗粒出现不同程度的长大。可见,在车载工况下,由于低氢气计量比引起的局部缺氢,加速了碳载体腐蚀,并使Pt颗粒的团聚以及流失,影响燃料电池性能。     

氢气进气压力对空冷PEMFC性能的影响

空冷型质子交换膜燃料电池(PEMFC)具有自增湿、质量轻、系统操作简单等特点,适合应用于无人机等领域。氢气进气压力是影响空冷型PEMFC电堆性能的一个重要因素。以1 kW阴极开放式空冷型PEMFC电堆为研究对象,对比了不同氢气进气压力对单片电池电压及其一致性、电堆输出电压、输出功率以及氢气利用率的影响。研究结果表明,氢气进气压力越高,单片电池电压、电堆输出电压和功率越高,大电流下单片电池电压的一致性越好;此外,本实验利用排水法收集阳极尾气并计算氢气利用率,氢气进气压力越高,系统氢气利用率越低。     

空气流量对空冷燃料电池电堆性能的影响研究

空冷型氢燃料电池采用开放型阴极,具有自增湿、系统简单轻便等特点。为了揭示空气流量对输出性能的影响机制,对自组装的800 W空冷型燃料电池电堆进行了实验测试和数值分析,对比了不同空气风扇转速下电堆输出电压、净功率以及传质传热特性。结果表明：小电流条件下小空气流量可以保持电堆内较高的温度,减少活化损失,实现高净输出功率。然而,大电流条件下,小空气流量将导致电堆温度过高且分布不均匀。利用数值方法对组分和温度分布进行了可视化分析,结果表明低含水量引起的欧姆损失增加是限制输出功率的关键因素,通过提高风扇转速增加空气流量可以保证较好的冷却效果,从而提高含水量,减少欧姆损失。     

空气流量对空冷燃料电池电堆性能的影响研究

空冷型氢燃料电池采用开放型阴极,具有自增湿、系统简单轻便等特点。为了揭示空气流量对输出性能的影响机制,对自组装的800 W空冷型燃料电池电堆进行了实验测试和数值分析,对比了不同空气风扇转速下电堆输出电压、净功率以及传质传热特性。结果表明：小电流条件下小空气流量可以保持电堆内较高的温度,减少活化损失,实现高净输出功率。然而,大电流条件下,小空气流量将导致电堆温度过高且分布不均匀。利用数值方法对组分和温度分布进行了可视化分析,结果表明低含水量引起的欧姆损失增加是限制输出功率的关键因素,通过提高风扇转速增加空气流量可以保证较好的冷却效果,从而提高含水量,减少欧姆损失。     

混合电动汽车用镍氢动力电池的寿命试验

研制了一种圆柱D型6Ah高功率型镍氢动力电池,分析该电池应用于混合电动汽车时,在典型城市工况下电池的充放电电流、电压、荷电态、温度特性,拟合出一种大电流脉冲充放电的模拟工况循环寿命方法,获得了电池容量、内阻、效率、功率的变化特征。结果表明:电池在SOC 60%下,以60A电流充放电10 s进行脉冲充放电试验,循环寿命可达到10万次以上。     

应用于大尺寸平板型固体燃料电池电堆的Al2O3-SiO2-CaO基密封材料软化特性及其验证

设计研制了Al₂O₃-SiO₂-CaO基密封材料,对其高温晶化与软化、热性能、界面黏结特性开展了原位观察,并进行了电堆实际应用验证。结果表明:在不高于1 100℃时该密封材料均为非晶态,850℃开始软化,900~1 000℃出现球化。热重分析表明密封材料在0~960℃的质量损失较小,约为0.06%;密封材料与连接板、电池界面黏结紧密,利于固体氧化物燃料电池(SOFC)电堆密封应用。采用研制的密封材料组装了2个5单元SOFC短堆,分别进行了热循环与稳定性研究。结果表明:2个5单元电堆的开路电压达到6.0 V,平均开路电压1.2 V,电堆1热循环前后在35 A(0.56 A/cm²)条件下输出功率为运行无衰减,电堆2在27 A(电流密度0.43 A/cm²)进行恒流放电,运行300 h较为稳定。     

氮化硅陶瓷的热疲劳特性

在急冷法热疲劳下,热压氮化硅青瓷的机械性能发生了较大幅宣的衰减,材料的抗折强度衰减大于断裂韧性衰减。由于温度对裂纹生长的促进作用,经过多次急冷热循环,材料高温性能,无论强度还是断裂韧性衰减都大于常温性能衰减。热疲劳使材料内部的显微结构发生了显著变化。     

Effect of Contact Method between Interconnects and Electrodes on Area Specific Resistance in Planar Solid Oxide Fuel Cells

In this work, interconnect/electrode sheet/interconnect sandwiches are assembled by designing interfacial contact between interconnects and electrodes for planar solid oxide fuel cells (SOFCs). Their area specific resistance (ASR) values of different contact methods under isothermal oxidation and thermal cycling are recorded by four‐point method. The ASR of SUS430/Ni–YSZ/SUS430 anode sandwich with NiO current collecting layer is close to that of anode sandwich without NiO current collecting layer during isothermal operation, but smaller and more stable during thermal cycling. Meanwhile, the lowest ASR is obtained in SUS430/LSM–YSZ/SUS430 cathode sandwich with LSM coated interconnect and LSM current collecting layer among various contact methods between interconnects and cathodes, and remains constant under isothermal oxidation and thermal cycling. Contact resistance between cathodes and interconnects is the main source of the SOFC stack resistance. A real stack with three anode‐supported cells is assembled and tested under thermal cycling to verify the effect of different contact methods between interconnects and electrodes on performance of stack repeating unit. The degradation rate and ASR values of repeating unit inside the stack indicate that the contact between LSM coated interconnect and LSM current collecting layer on cathode side is the optimized contact.     

质子交换膜燃料电池冷启动堆栈温度预测模型

为了快速准确地预测出质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)在冷启动过程中的启动时长及启动方法的应用效果,提出了以堆栈温度和温度增量分别作为BP(back propagation)神经网络预测目标的堆栈温度实时预测模型,分别为模型T和模型K,并采用四个不同的预测精度评估标准来评估预测结果的准确性。基于文献中三种冷启动工况实验数据对预测模型进行验证,结果表明,模型K的平均相对误差在三种工况下均低于模型T,分别为0.4553、0.9537和1.0844。模型T在早期预测阶段缺乏训练样本,预测结果的堆栈温度变化趋势为零,因而模型K在早期预测阶段具有更大优势。堆栈温度变化趋势预测方法能够为用户当前的PEMFC冷启动实现效果提供参考。     

Progress in Microtubular Solid Oxide Fuel Cells

The benefits of microtubular solid oxide fuel cells (SOFCs) are addressed, including increased power density, rapid start-up, and cycling performance. Several international developments are discussed, especially small portable applications, which demand fast start and multiple cycles. Extrusion is the main method for making microtubular SOFCs because improved structure and properties can result from better mixing of the component particles and coextrusion can integrate several cell components in one process step. When the tubes are <3 mm in diameter, it is shown that the power density and thermal shock resistance are much increased, with start-up in a few seconds rather than hours for planar designs, as demonstrated in a single-cell hand-held system running on butane. The problems of cycling, both thermal and redox, are then considered in detail. Thermal cycling degradation follows a fatigue curve whereas redox damage is linear with the number of cycles. New results are presented on thermal and redox cycling performance.     

Anode-Supported Tubular Micro-Solid Oxide Fuel Cell

A tubular anode-supported "micro-solid oxide fuel cell" (μSOFC) has been developed for producing high volumetric power density (VPD) SOFC systems featuring rapid turn on/off capability. An electrophoretic deposition (EPD)-based, facile manufacturing process is being refined to produce the anode support, anode functional and electrolyte layers of a single cell. μSOFCs (diameter <5 mm) have two main potential advantages, a substantial increase in the electrolyte surface area per unit volume of a stack and also rapid start-up. As fuel cell power is directly proportional to the active electrolyte surface area, a μSOFC stack can substantially increase the VPD of an SOFC device. A decrease in tube diameter allows for a reduction in wall thickness without any degradation of a cell's mechanical properties. Owing to its thin wall, a μSOFC has an extremely high thermal shock resistance and low thermal mass. These two characteristics are fundamental in reducing start-up and turn-off time for the SOFC stack. Traditionally, SOFC has not been considered for portable applications due to its high thermal mass and low thermal shock resistance (start-up time in hours), but with μSOFCs' potential for rapid start-up, new possibilities for portable and transportable applications open up.     

水冷PEMFC热管理系统流量跟随控制策略

针对传统温度控制策略在水冷型质子交换膜燃料电池（proton exchange membrane fuel cell,PEMFC）工作中水泵和散热器风扇存在的强耦合性,并为了提高电堆的工作性能和寿命,提出一种流量跟随电流的温度控制策略,根据电堆电流变化调节冷却水流量来控制电堆冷却水进出口温差,通过PID控制器调节散热风扇控制电堆入口温度。在水冷PEMFC热管理平台上对传统控制策略、流量跟随控制策略做了实验对比。结果表明,流量跟随电流控制策略使冷却水出口温度最大超调量减少64.3%,冷却水出入口温差最大偏差减少46.7%,调整时间平均缩短73 s,达到了较高的控制精度和响应速度,削弱了水泵和散热风扇的强耦合作用,流量跟随电流控制策略能够满足PEMFC系统对温度控制的要求。     

Operation characteristics of portable direct methanol fuel cell stack at sub-zero temperatures using hydrocarbon membrane and high concentration methanol

Cold start and operation of a direct methanol fuel cell (DMFC) are investigated at sub-zero temperatures by using a 10-cell stack. The stack is manufactured with a hydrocarbon membrane to minimize the methanol crossover problem, which can be caused by use of high concentration methanol solutions. The stack is heated up for the cold start and operation only by heat of the exothermic reactions without any heating device and additional insulation means, to examine operation characteristics of the DMFC stack at low temperatures. The concentration of methanol solutions is selected in the range of 3-8 M, considering the freezing points of the solution for corresponding operation temperatures (−5 to −15 °C). Although the DMFC stack undergoes a sharp voltage drop and a significant performance decrease at the initial stage of the frozen condition, the self-heating DMFC are successfully operated at −5 and −10 °C in both constant current or constant voltage modes. The cold start-up time also is nearly independent of the operating modes. In contrast, the stack at −15 °C is barely started up only by a constant voltage mode with some voltage fluctuation. The DMFC stack after the cold operation exhibits the performance loss of about 45%. Such performance loss is mainly caused by degradation of the electrocatalysts.     

固体氧化物燃料电池堆的稳定工况特性

以大面积电池和千瓦级电堆为对象,研究了温度、燃料成分、流量等对阳极支撑型电堆性能的影响。结果表明:温度的影响最大,复数阻抗谱中高频弧对应的活化能最高;欧姆阻抗的活化能较低,表明其不全是离子电导的电阻,还包括双极板的表面电阻和可能的接触电阻。利用干氢气燃料测试时,在开路电压附近表现出较大的活化极化,且其活化能很小,表明该活化极化的速率控制步骤并非是电荷转移过程,而是对应某种表面扩散过程。模拟重整气燃料测试过程中活化极化不明显,但开路电压较低,性能比氢气燃料差。随着电堆工作电流的增加,燃料尾气的温度增加,表现出明显的热效应。     

原位浸渍法制备NiO-BZCYYb阳极支撑SOFCs及电化学性能

采用原位浸渍法一步烧结成型制备了NiO-BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ（BZCYYb）/SDC/LSCF管状结构阳极支撑型SDC电解质膜固体氧化物燃料电池（SOFCs）。以加湿H₂（约含有体积分数为3%的水）为燃料,空气为氧化剂,研究了电池的电化学性能、热循环性能和工作电压下运行的稳定性。结果表明：电池在600、650、700、750、800℃的开路电压分别为1.084、1.074、1.067、1.058、1.046 V;最大输出功率密度分别为0.12、0.25、0.38、0.54和0.70 W·cm^-2。单电池在700℃和0.7 V连续放电测试过程中稳定运行,没有明显的下降和衰退。单电池经历了11次热循环,输出功率稳定,能够经受住重复启动考验。     

Investigation of Impactors on Cell Degradation Inside Planar SOFC Stacks

The impactors on cell degradation inside planar SOFC stacks were investigated using both coated and uncoated Fe–16Cr alloys as the interconnects under stable operating conditions at 750 °C and thermal cycling conditions from 750 to 200 °C. It was found that cell degradation inside the stack is primarily dependent on the interfacial contact between the cathode current‐collecting layer and the interconnect. Additionally, cell degradation is found to be independent of the high‐temperature oxidation and Cr vaporization of the interconnects during stack operation, as the stacks are well sealed. The coating on the interconnect can further improve the contact between the cell cathode and the interconnect when the latter is properly embedded into the current‐collecting layer.