A Study On Plateless Proton Exchange Membrane Fuel Cells Design And Manufacturing Process

Proton exchange membrane fuel cell (PEMFC), which can transfer chemical energystored in hydrogen into electrical energy directly without burning, is considered to bean ideal power source for transportation, electronic products, defense and military byvirtue of its clean, efficient and renewable characteristics. PEMFC has been receivinggrowing interest from academia and industry. Previous researches are mainly focusedon conventional plate-and-frame architecture of PEMFC, and significant progress hasbeen achieved in key components development, stack assembly and system controletc. Nevertheless, graphite bipolar plates of plate-and-frame architecture have highmanufacturing cost, as well as low power density due to low utilization ratio ofmembrane electrode assembly (MEA) and large thickness of bipolar plates. Althoughmetallic bipolar plates adopt ultra-thin material, the increase of power density is stilllimited due to the plate-and-frame architecture. Therefore, it is very necessary toinnovate the PEMFC architecture to improve the volumetric power density and masspower density fundamentally.In this study, a novel plateless PEMFC architecture is proposed firstly based onwave-like metallic gas diffusion layer (GDL) and compound membrane electrodeassembly (CMEA). An elastoplastic constitutive model considering the microscopicfeatures and a finite element method (FEM) model to simulate the forming process areestablished to investigate the manufacturing of sintered metal fiber GDL. Thereafter,the forming processes for wave-like metallic GDL and CMEA and the stack assemblyprocess are developed, respectively. Finally, experimental prototypes of platelessPEMFC single cell and100W-class stack are assembled and the performance issystematically evaluated. Experimental results demonstrate that the plateless PEMFCarchitecture can improve volumetric power density and mass power densitysignificantly. To fulfill the above research objectives, the following four aspects ofefforts are performed:1) Design of plateless PEMFC architectureA novel plateless PEMFC architecture is proposed and the operating principle is analyzed. The MEA is fabricated into wave-like shape to increase reaction area andimprove utilization ratio of MEA. Besides, metal porous material is adopted to giveconsideration to the function of bipolar plate and GDL. And the conventional bipolarplates are eliminated so that ohmic losses can be greatly reduced. Therefore, thepower density could be improved remarkably by the novel architecture. The flow fieldof plateless PEMFC is designed and key parameters of CMEA cross-section areoptimized. Meanwhile, the relevant physical and chemical properties are studied byexperiments and the possibility of metallic GDL is demonstrated.2) Modeling and analyzing of elastoplastic constitutive equation for sinteredmetal fiber GDL materialAn elastoplastic constitutive model of sintered metal fiber GDL material isdeveloped based on micromechanics and statistic theory. Considering the complexmicroscopic features, a geometrical method is established to describe the fiber spatialdistribution in sintered metal fiber GDL material. Afterwards, elastoplastic equationsand yield criterion of metallic GDL are introduced based on micromechanics. Anelastoplastic constitutive model considering statistical characteristics of fiber length,planar angle and elevation angle is well developed based on statistic theory. Accuratematerial model can be provided to FEM model of forming process and failurecriterion of metallic GDL material.3) Numerical modeling and process design for forming process of sinteredmetal fiber GDLBased on the elastoplastic constitutive model, FEM model to simulate the formingprocess of sintered metal fiber GDL is developed and the formability is analyzed. Thefailure mode of sintered metal fiber GDL is deeply analyzed according to tensile andcompression experiments and the failure criterion is built considering fiber breakageand porosity decrease. A2D FEM model of metallic GDL forming process is furtherestablished and the formability is systematically studied. Afterwards, a3D FEMmodel is developed for wave-like metallic GDL with complex features in flow fieldand the formability of whole metallic GDL is investigated.4) Manufacturing of plateless PEMFC prototypes and experimental studyBased on the above models and methodologies, experimental prototypes ofplateless PEMFC are developed and performance experiments are conducted.Stamping mould system is designed and machined, and wave-like CMEA with complex features in flow field is then fabricated. The influence of assemblyparameters on the contact performance of CMEA is analyzed by experiments andoptimum parameters are obtained. Experimental prototypes of plateless PEMFC areassembled using optimum assembly parameters and the performance is systematicallyevaluated. Compared to plate-and-frame architecture with graphite and metallicbipolar plates, the novel plateless PEMFC architecture achieves higher volumetric andmass power density.In conclusion, this thesis focuses on developing a novel plateless PEMFC stack,including design for the plateless PEMFC architecture, elastoplastic constitutiveequation derivation for sintered metal fiber GDL material, FEM modeling and processdesign for forming process, manufacturing of plateless PEMFC prototypes andperformance evaluation. The methodology and conclusion of this study are beneficialto guide the design and manufacturing of plateless PEMFC.