Abstract:

The gas diffusion layer (GDL) porous media is composed of two components with significantly different structures: the porous transport layer (PTL) and the microporous layer (MPL). The PTL/MPL interface has a non-negligible impact on the performance of the battery. To deeply investigate the effect of mechanical stress on the transport properties at the PTL/MPL interface. This study first reconstructs the three-dimensional microscale structure of the interface by using X-ray tomography to characterize the commercial GDL. Subsequently, the finite element method is utilized to simulate the distribution of stress, strain, and microstructure parameters at the interface under different mechanical compression ratios. Finally, the relationship between the mechanical compression ratio and the anisotropic effective transport properties is obtained by using a pore scale model. It is found that a 40% mechanical compression ratio leads to a 41% reduction in porosity and nearly 62% decrease in average pore size at the interface. In addition, the tortuosity increases by 61%, the gas diffusivity decreases by 57%, and the conductivity doubles in the in-plane direction. The tortuosity increases by a factor of two, the gas diffusivity decreases by 67%, and the effective conductivity increases by a factor of three in the through-plane direction.

Key words: gas diffusion layer, porous media, interfaces, microscale, mechanical stress, pore scale model, transport properties

摘要：

气体扩散层（GDL）多孔介质由多孔传输层（PTL）和微孔层（MPL）两个结构差异显著的组件构成，PTL/MPL界面对电池的性能有不可忽视的影响。为了深入研究机械应力对PTL/MPL界面传输特性的影响，首先利用X射线断层扫描表征商用GDL，重构出界面三维微尺度结构。随后使用有限元方法模拟界面在不同机械压缩比下的应力、应变和微结构参数分布。最后利用孔尺度模型获得机械压缩比与各向异性有效传输特性的关系。研究表明，40%的机械压缩比导致界面上的孔隙率减小了41%，平均孔径下降了近62%。此外，平面内方向的曲度增加了61%，气体扩散率降低了57%，传导率增加了1倍；厚度方向上曲度增加了1倍，气体扩散率降低了67%，有效传导率增加了3倍。

关键词: 气体扩散层, 多孔介质, 界面, 微尺度, 机械应力, 孔尺度模型, 传输特性