Reducing contact resistance in wire-mesh-integrated flow fields via welding to improve PEMFC performance

Abstract

Metal wire mesh flow fields enhance reactant transport in polymer electrolyte membrane fuel cells (PEMFCs), but insufficient mesh-bipolar plate contact can increase ohmic loss. This study investigated spot welding to reduce this interfacial resistance. Four configurations were evaluated using 30, 40, and 50 mesh samples: untreated, center-point mesh-only welded, center-point mesh-to-plate welded, and nine-point mesh-to-plate welded. Raman spectra showed no significant peak shifts or detectable new bands after welding in the examined mesh and bipolar-plate regions. Contact resistance measurements showed that direct mesh-to-plate welding reduced interfacial resistance more effectively than mesh-only welding. Single-cell polarization, electrochemical impedance spectroscopy, and nonlinear regression-based loss analysis indicated that the performance improvement was primarily associated with reduced ohmic loss, while activation and concentration losses showed only minor differences. The welding effect was greatest for 30 mesh and diminished with increasing mesh number, likely because denser meshes inherently provided more contact points. These results demonstrate that spot welding can reduce the ohmic penalty of mesh-integrated bipolar plates, with its effectiveness depending on mesh geometry and contact density.