Effect of fiber structure on mechanical support and electrical-thermal conductivity of gas diffusion layer

Proton exchange membrane fuel cells (PEMFC) are efficient clean energy devices that convert chemical energy into electrical energy through electrochemical reactions. The gas diffusion layer (GDL) is a critical component for energy transfer, mass transport, and mechanical support to the membrane electrode assembly. The anisotropic properties of GDL show obvious structural differences, and the compression effect also significantly affects the pore structure. However, the influence of the coupling effect of the native structure and the compression on the electrical and thermal conductivity of the GDL has not been systematically studied. This study employs the finite element method to examine the effects of various porosity, thickness, carbon fiber diameter, and fiber inclination angles. The maximum fiber inclination angle phi max is defined to reflect the manufacturing process. The heat exchange coefficient between carbon fibers and air is proposed. All structures exhibit nonlinear mechanical behavior, with porosity exerting significant influence on mechanical and conductive properties. The stiffness of GDL increases proportionally with phi max. The GDL with a fiber diameter of 10 mu m exhibits the lowest stiffness under 20 % compression. The electrical and thermal conductivity in the through-plane (TP) direction before and after compression is also proportional to phi max. A phi max of 7.5 degrees benefits in-plane (IP) electrical conductivity under compression but does not enhance thermal conductivity. Compared to an approximate 30 % increase in the effective thermal and electrical conductivity in the IP direction, the effective conductivity in the TP direction is significantly enhanced by several multiples. The findings presented in this work contribute to a deeper understanding of the structural, mechanical, and conductive properties of GDL. And the pore-scale simulation methodology employed can serve as a valuable reference for analogous investigations.