【作者】 王萌；

【导师】 王新东；

【作者基本信息】 北京科技大学 ， 冶金工程， 2019， 博士

【摘要】 质子交换膜燃料电池中两个主要类别,直接甲醇燃料电池与氢氧燃料电池在各自的领域都是新兴型能源装置中的强力竞争者。直接甲醇燃料电池燃料储存便利,对于燃料的补充没有任何技术或安全性门槛,适用于各种便携电子器件。而氢氧燃料电池是目前汽车动力领域唯一的锂电竞争者。本论文针对直接甲醇燃料电池堆结构常见多发的密封体系不安定问题进行了多方面的改进设计,并从结构机制上缓解甚至避免了这些问题。对所设计的电堆进行了加工制造和测试,验证了设计思路的有效性。在解决了电堆问题后,通过对大量极化曲线实验数据进行电极动力学控制方程的参数拟合,建立了试算结果与实验数据高度相符的三维数值模型。通过三维数值模型进行了5因素4水平的操作参数优化正交实验,采用正交实验的优选参数组合使电池测试性能提高了 10%。通过包含166次运行,累计有效寿命达3135.7小时的燃料电池长期运行测试,及运行过程中的多种性能损失行为监测研究发现,燃料电池有效寿命控制因素在不同运行阶段差别较大,发生阶段性失效现象的原因也各不相同。在单次运行过程中,合理加大阴极侧氧气压强可以实现催化剂活性的提高和传质通道的改善,从而提高燃料电池的有效寿命。Rohm在55℃运行温度阶段增加较快,这说明较低的温度下的性能损失主要来自于膜的质子传导率损失。实施质子恢复方案和提高运行温度可以有效缓解Rohm的暂时性增加,恢复燃料电池的性能。随着燃料电池的运行时间增加,阴极水淹现象会逐渐严重,在较高温度对传质能力的影响尤为突出,导致严重的浓差极化。采用阴极通入氮气作为应对传质能力暂时性下降的恢复方案可以有效恢复燃料电池因阴极水淹造成的性能损失。而催化剂的活性损失属于永久型性能损失,最终导致燃料电池的失效。总的来说,造成燃料电池性能衰减的控制因素随运行阶段不同而有较大差别,明确运行条件与不同性能损失行为之间的关系,合理实施恢复方案,能够有效提高DM-PEMFC的有效寿命。为解决膜电极制备稳定性不足,不合格品危害大又难以在装配测试前检出的问题,设计了膜电极无损检测设备,并进行了检测方案论证,达到了 16片同批次膜电极中3片不合格品提前100%检出且不对正常膜电极性能产生任何不利影响的目的。在膜电极无损检测技术的保障下,进行了多因素寿命预测方案研究。通过对极化曲线数据进行电化学活化过电位、欧姆过电位和浓差过电位的拆分,提取了三个独立变化的寿命影响因素,并研究和分析了基于这三个因素的寿命预测方案。相对于传统的平均衰减率外推法,此方案更能反映实验数据中隐藏的电极动力学变化趋势,对于50%性能损失寿命的预测结果与实验数据相比误差小于4%。更多还原

【Abstract】 Two main categories of proton exchange membrane fuel cells,direct methanol fuel cells and oxyhydrogen fuel cells are fierce competitors in emerging energy devices in their respective fields.Fuel storage of direct methanol fuel cell is convenient,there is no technical or safety threshold for fuel replenishment,and it is suitable for various portable electronic devices.The oxyhydrogen fuel cell is the single lithium battery competitor in the field of automotive power.This paper has improved the design of many common sealing system instability problems in direct methanol fuel cell stack structure.And alleviate or even avoid these problems from the structural mechanism.The fuel cell was fabricated and tested to verify the effectiveness of the design.After solving the fuel cell structure problem,by fitting the parameters of the electrode dynamics control equation to a large number of polarization curve experimental data,a three-dimensional numerical model that was highly consistent with the experimental data was established.The 5-parameter 4-level operation parameter optimization orthogonal experiment was carried out by the 3D numerical model,and the cell performance was enhanced by 10%by using the preferred parameter combination of the orthogonal experiment.A 3135.7 hours long-term degradation test of fuel cells with 166 time of operation was carried out,and various performance loss behavior was monitored by in situ electrochemical method.Fuel cell durability varied a lot of discharge time and stage-failure phenomenon of single cell occurred in the lifetime test.During the sole operation process,continuous lifting pressure operation can realize the improvement of catalyst activity and optimization of mass transfer channel to increase fuel cell durability.The most rapid increase rate of Rohm appears at 55 oC,and lower temperature mainly caused the increase in membrane resistance.Proton recovery method and increasing operational temperature realize the effective reduction of Rohm and recovery fuel cell discharge ability.Along with the continuous discharge of a single cell,cathode "water flooding" phenomenon mainly comes out at a higher temperature,and acts as the main degradation reason,which directly results in a serious concentration polarization and sharp loss of durability.N2 purging worked as an operational method to realize the recovery of performance of fuel cell.The final catalyst deactivation caused the ultimate failure of fuel cell.Therefore,main degradation of fuel cell varies with operation time,and the relationship between operational conditions and durability is helpful to improve the real lifetime of the fuel cell.In order to solve the problem that the stability of the membrane electrode preparation is insufficient,the non-conforming product is harmful and difficult to be detected before the assembly test.The membrane electrode assembly non-destructive testing equipment was designed,and the detection scheme is demonstrated.Three of the 16 batches of the same batch of membrane electrodes were detected 100%in advance and did not have any adverse effect on the performance of the normal membrane electrode.Under the guarantee of membrane electrode nondestructive testing technology,the multi-factor life prediction scheme was studied.Through the resolution of electrochemical activation overpotential,ohmic overpotential and concentration overpotential of polarization curve data,three autonomous changes of life influencing factors were extracted,and life prediction schemes based on these three factors were studied and analyzed.Compared with the traditional average attenuation rate extrapolation method,this scheme can better reflect the hidden electrode dynamics trend in the experimental data.The prediction result for 50%performance loss lifetime is less than 4%compared with the experimental data.更多还原