质子交换膜燃料电池电化学阻抗谱敏感性研究

电化学阻抗谱能被用来表征燃料电池内部状态和电化学行为信息,通过构建合适的等效电路模型拟合电化学阻抗谱,可辨识和量化燃料电池内部不同的极化过程及状态.针对质子交换膜燃料电池,系统研究电流密度、工作温度、压力、阴/阳极进气过量系数和阴/阳极进气湿度7种外部工作条件对燃料电池电化学阻抗谱的影响.基于等效电路法,对阻抗谱各频段阻抗的变化及其对工作条件的敏感性进行分析和讨论.研究表明,燃料电池损耗在低、中、高电流密度下分别由活化损耗、欧姆损耗和传质损耗主导;在固定电流密度下,电池温度、压力、阴极进气过量系数和阴极进气湿度对阻抗谱影响较大;欧姆阻抗是对阴阳极进气湿度变化最敏感;阳极活化阻抗仅对阳极进气过量系数和阳极进气湿度较为敏感;阴极活化阻抗是对阴极过量系数最敏感,其次是温度和压力;传质阻抗对阴极过量系数敏感程度最大,压力和温度次之;为燃料电池工作条件优化和内部状态的监测与诊断研究提供指导.     

基于电化学阻抗谱的锂离子电池等效电路模型参数辨识方法

针对常用的等效电路模型参数辨识软件在使用时需用户多次手动调整初始参数,不利于阻抗谱车载应用的问题,提出了一种无干预的等效电路模型参数辨识方法。根据电化学阻抗谱各特征成分与等效电路模型不同电路环节相对应的规律,通过分段拟合的方法自适应地获取阻抗谱拟合的初值,进而实现了等效电路模型参数辨识。通过解析不同老化状态、荷电状态、温度下的阻抗谱,发现该方法与常用参数辨识软件的结果保持一致,从而为阻抗谱在线应用提供了基础。     

数据通讯在电化学阻抗谱图示和解析中的应用

本文实现了ＡＰＰＬＥＩＩｅ微机向ＩＢＭ ＰＣ／ＸＴ兼容机的数据通讯，使Ｓｏｌａｒｔｒｏｎ１０９６电化学阻抗谱数据管理系统的数据在图形处理和数据拟合方面，能享受ＥＧ＆Ｇ ＰＡＲＣ Ｍ３７８电化学阻抗谱测量软件包和ＥＱＵＩＶＣＲＴ电化学阻抗谱解析软件包的各种优点，是对进口设备及软件开发的有益尝试。     

基于储能电池电化学阻抗谱宽频测量方法的研究

电化学阻抗谱(EIS)可以较为准确地反应储能电池内部的电化学参数。 为解决传统测量方法耗时长问题,采用了宽频 激励信号测量储能化学电池阻抗信息的方法,并基于 MATLAB-Simulink 仿真平台和 EIS 测量试验平台进行验证,该测量方法将 宽频交流扰动信号注入储能电池,并通过快速傅里叶变换方法分解处理宽频激励和响应信号来获取各频点的电池阻抗信息,以 此大幅节省电池 EIS 的测量时间。 采用两种宽频激励方法测量了电池等效电路模型和储能电池,相较电化学工作站扫频测量 方法,可分别节省 60% 和 78% 的测量时间,且测量结果误差较小。 用宽频激励方法实现电池 EIS 快速测量,可为电池管理系统 的实时诊断和线上检测等更为广阔的应用场景提供技术支撑。     

基于锂电池等效电路模型的阻抗曲线拟合算法

近些年利用电池阻抗谱(EIS)估算锂电池状态的研究取得了较大进展。本文提出了一种EIS等效电路模型参数提取算法,用于分析提取不同状态下的电池等效电路参数,具有简单、不易发散的优点。首先通过结合模型的物理意义计算获得等效电路模型参数初值,然后利用等效电路与EIS之间的映射关系进行迭代,从而实现了参数的提取。对比理论参考值,提取的关键参数的误差低于4.4%。为了获得锂电池在不同荷电状态下的EIS数据,利用电化学工作站在恒温状态下测量选用的磷酸铁锂电池,利用算法编写的软件实现等效电路参数的提取。通过对比不同荷电状态下的等效模型参数,在一定程度上验证了利用EIS快速估计锂电池状态的可行性。     

贴壁细胞电阻抗谱等效电路模型的建立与分析

为了在生物电特性与生化特性之间建立明确的映射关系,采用微加工技术于硅玻璃基底上研制出了叉指结构金电极阵列,组装出了能实时、连续获得细胞电阻抗谱的测量装置。将子宫颈癌细胞接种于测量装置中,细胞在电极上进行正常贴附生长,使用Parstat4000连接测量装置获得了不同时刻频率范围为1 Hz~1 MHz的细胞电阻抗谱数据;在已有细胞阻抗谱等效电路模型基础上,根据实际测量阻抗谱数据,结合细胞生理过程电特性,提出了修正细胞阻抗模型。研究结果表明,该修正模型用于拟合阻抗数据的方差比原模型小,同时修正模型包含参数按变化趋势分作两组,分别反映细胞贴附生长过程中溶液特性的变化和细胞本身的变化,最终建立了细胞阻抗数据与细胞生理变化之间的定性关系。     

质子交换膜燃料电池-四温位吸收式制冷机混合系统性能分析

建立质子交换膜燃料电池-四温位吸收式制冷机混合系统模型,该模型考虑包括燃料电池热力学和电化学不可逆性、吸收式制冷循环不可逆性在内的主要损失,导出系统总的输出功率和效率表达式,以及吸收式制冷循环的制冷量及制冷系数关系式。通过数值计算探讨混合电池系统的整体性能,分析不同运行工况参数对混合系统性能的影响规律,得出电流密度、输出功率、效率等重要参数的优化工作区间。系统对质子膜燃料电池的余热进行合理利用,使质子膜燃料电池混合系统总的输出功率以及效率都有了较大的提高。     

导电聚吡咯的电化学性能研究

针对聚吡咯(PPy)材料的电化学性能问题,对PPy的制备工艺过程、氧化还原反应、交流阻抗及阶跃响应进行了研究。采用电化学工作站中的计时电位法在镀铜的聚偏二氟乙烯(PVDF)膜表面制备PPy膜,结合循环伏安法(CV曲线)分析了其氧化还原反应,探究了驱动器内部离子迁移过程,分析了引起PPy膜膨胀收缩的机理,并计算了不同扫速下的比电容;利用交流阻抗谱(EIS)测试PPy的阻抗,采用ZSimpwin软件建立了等效电路模型,并根据拟合后的数据计算了电导率;之后对PPy进行了恒电位阶跃测试,探究了充放电时间常数。研究结果表明:循环伏安测试能有效地描述PPy膜的氧化还原状态及内部离子的迁移,交流阻抗测试可将PPy的阻抗电路等效为R(C(RW))电路,恒电位阶跃曲线能准确描述PPy膜的充放电时间常数。     

质子交换膜燃料电池膜电极组件的制备

采用直接涂膜技术,利用40%的Pt/C催化剂制备质子交换膜燃料电池的核心部分膜电极组件.通过优化催化层中催化剂与Nafion的最佳质量比以及扩散层的微孔层的聚四氟乙烯与碳粉的质量比以改进燃料电池的性能,并利用循环伏安、电化学阻抗谱等技术对电池的电化学性能进行了表征.研究表明催化层中催化剂与Nafion的最佳质量比为3∶1时,对应的电池的活性面积最大,欧姆阻抗和电荷传递阻抗最小.另外,研究还发现在恒电流条件下,当扩散层的微孔层中碳粉质量分数为2 mg/cm2,碳粉与PTFE的质量比为7∶3时,放电性能最佳.     

车用燃料电池欧姆内阻辨识算法

针对车用燃料电池欧姆内阻辨识问题,以质子交换膜燃料电池工作原理为基础,建立电池的等效电路模型。利用电路相关知识建立等效电路的数学关系模型,在此基础上推导出模型的差分方程。介绍目前参数辨识使用比较广泛的递推最小二乘法,并结合实车NEDC工况估计出电池的欧姆内阻。在Simulink仿真平台上验证了该算法的收敛性、有效性以及良好的鲁棒性。与现有方法相比,该方法具有在线实时估计、无需额外激励源以及硬件电路支持、算法较简单等优点。     

Novel electrochemical impedance simulation design via stochastic algorithms for fitting equivalent circuits

Electrochemical impedance spectroscopy (EIS) is of great value to corrosion studies because it is sensitive to transient changes that occur in the metal-electrolyte interface. A useful way to link the results of electrochemical impedance spectroscopy to corrosion phenomena is by simulating equivalent circuits. Equivalent circuit models are very attractive because of their relative simplicity, enabling the monitoring of electrochemical systems that have a complex physical mechanism. In this paper, the stochastic algorithm Differential Evolution is proposed to fit an equivalent circuit to the EIS results for a wide potential range. EIS is often limited to the corrosion potential despite being widely used. This greatly hinders the analysis regarding the effect of the applied potential, which strongly affects the interface, as shown, for example, in polarization curves. Moreover, the data from both the EIS and the DC values were used in the proposed scheme, allowing the best fit of the model parameters. The approach was compared to the standard Simplex square residual minimization of EIS data. In order to manage the large amount of generated data, the EIS-Mapper software package, which also plots the 2D/3D diagrams with potential, was used to fit the equivalent circuit of multiple diagrams. Furthermore, EIS-Mapper also computed all simulations. The results of 67 impedance diagrams of stainless steel in a 3.5% NaCl medium at 25 °C obtained in steps of 10 mV, and the respective values of the fitted parameters of the equivalent circuit are reported. The present approach conveys new insight to the use of electrochemical impedance and bridges the gap between polarization curves and equivalent electrical circuits.     

基于短时脉冲放电与电化学阻抗谱的退役动力 电池快速分选与重组方法

针对现阶段退役动力电池筛选效率低、能耗大和成组率低等问题,提出了一种基于短时脉冲放电与电化学阻抗谱(EIS)相结合的退役动力电池快速分选与重组方法。通过对200节同类型不同批次的退役磷酸铁锂动力电池进行短时脉冲放电与阻抗谱测试和分析后,将获取的脉冲电压差、直流内阻、EIS曲线形状特征以及EIS等效电路模型参数作为筛选指标并建立数学模型,实现了对退役动力电池快速有效的分选与重组。验证实验结果表明：该方法能有效地降低能耗,且单节电芯的平均测试时间短至20 min以内,同时成组后的模组一致性指标较好,在工程上具有较大的实用价值。     

不同参数对质子交换膜燃料电池输出特性的影响

针对质子交换膜燃料电池(Proton Exchange Membrane Fuel Cell,PEMFC)的性能主要受到物理参数影响的问题,通过FLUENT软件建立燃料电池动力学模型,以对物理参数进行研究,得到了直行多流道单体质子交换膜燃料电池的极化曲线并对输出性能进行对比。结果表明:升高工作温度、升高运行压力以及降低质子交换膜厚度均有助于提高燃料电池输出电压,改善燃料电池的性能。研究结论将为PEMFC的设计和实际应用操作提供参考。     

Influence of PTFE on electrode structure for performance of PEMFC and 10-cells stack

Water plays a critical role on the performance, stability and lifetime of proton exchange membrane fuel cells(PEMFCs). The addition of poly tetrafluoroethylene(PTFE) to the gas diffusion layer, especially, the cathode side, would optimize the transportation of water, electron and gas and thus improve the performance of the fuel cell. But until now, the studies about directly applying the PTFE to the catalyst layer are rarely reported. In this paper, the membrane electrode is fabricated by using directly coating catalyst to the membrane method(CCM) and applying PTFE directly to the cathode electrode catalyst layer. The performance of the single cell is determined by polarization curves and durability tests. Electrochemical impedance spectroscopy(EIS) and scanning electron microscopy(SEM) techniques are used to characterize the electrochemical properties of PEMFC. Also the performance of a 10-cells stack is detected. Combining the performance and the physical-chemistry characterization of PEMFC shows that addition of appropriate content of PTFE to the electrode enhances the performance of the fuel cell, which may be due to the improved water management. Addition of appropriate content of PTFE enhances the interaction between the membrane and the catalyst layer, and bigger pores and highly textured structure form in the MEA, which favors the oxygen mass transfer and protons transfer in the fuel cell. While superfluous addition of PTFE covers the surface of catalysts and hindered the contact of catalyst with Nafion, which leads to the reduction of electrochemical active area and the decay of the fuel cell performance. The proposed research would optimize the water management of the fuel cell and thus improve the performance of the fuel cell.     

Lifetime Evaluating and the Effects of Operation Conditions on Automotive Fuel Cells

Lifetime is one of the important indicators of automotive proton exchange membrane fuel cells. People used to evaluate the lifetime of vehicular fuel cells by laboratory tests or road tests that usually take thousands hours even years. In order to achieve a rapid evaluation technique and to seek lifetime extension methods, a lifetime calculation formation was drawn out in consideration of the vehicle driving cycle and the working condition factors. Bench experiments were individually carried out on two fuel-cell stacks same as ones applied on vehicle, and the performance decay rates of the two stacks were obtained under four operation conditions of changing load cycle, start-stop cycle, idling and heavy load. As a result, the predicted lifetimes rather conform to the actual running status in road test. And the research on the fuel cell performance decay rates under different load conditions was also done. Consequently, an unexpected finding was discovered that operating under micro-current has an effect on recovering fuel cell performance. The vehicle fuel cell rapid assessment method only requires four laboratory tests of driving cycle, load cycle, idle operating conditions and heavy load conditions, and the whole process merely lasts less than 250 h. These experimental results can be used to predict the vehicular fuel cell lifetimes on various utility models or driving cycles, therefore to optimize the application model to prolong the fuel cell lifetime. Actually in the experiment, it has already been proved successfully that the fuel cell lifetime could be extended from 1 100 h to 2 600 h by optimizing operating mode. The quick evaluation method is helpful to develop extended life fuel cell and to deplete fuel cell for a longer time.     

Computation of pressure fluctuation frequency in electronic unit pump for diesel engine

Pressure variations inside a fuel injection system can lead to fluctuations in injected fuel quantity during injections and therefore can directly impact the stability and performance coherence of the fuel injection system and the engine it matched. Concepts of hydraulic capacitance and hydraulic inductance are introduced into fuel injection system by referencing LC oscillator electric circuit. A LC undamped hydraulic mathematical model is developed based on the structural parameters of the electronic unit pump (EUP). Pressure fluctuation frequency during injection process at different operating conditions of the EUP is computed by the LC undamped model. It is observed that the frequencies of pressure fluctuations tend to increase with the fuel injection process. Pressure curves and pressure fluctuation frequencies obtained by experiments at different operating conditions validated the results predicted by the LC undamped mathematical model.     

油纸绝缘混合极化的频域谱模型及参数辨识

采用等效模型分析是间接评估油纸绝缘老化状态的一种有效方法,而构建油纸绝缘系统的等效模型及参数计算是研究的基础和难点。针对目前广泛采用扩展德拜模型存在的不足,引入界面极化支路的油纸绝缘混合极化等效模型更为贴合实际极化过程,同时研究油纸绝缘混合极化过程的频域介电谱模型参数辨识方法。首先,在新型极化等效电路基础上导出频域谱与电路参数之间的关系;其次,建立求解多元方程组的目标函数,然后应用自适应收缩因子粒子群算法(ACPSO)进行参数求解;最后,通过实测数据验证该方法辨识模型参数的可行性与准确性。计算结果表明,考虑有界面极化的混合等效模型更能真实反映油纸绝缘的弛豫过程,它更符合变压器绝缘极化的实际情况;基于频域介电谱的油纸绝缘等效模型参数辨识法,相比于此前基于时域介电谱的辨识方法,具有求解过程简单、参数计算结果准确可靠等优点。