The ultra-thin flexible graphite/epoxy bipolar plates adjusted by different surface tension modifiers and application in the fuel cell stack.

The graphite-resin composite bipolar plates prepared by the traditional hybrid pressing process exhibit poor conductivity, processability, and wettability due to the graphite flake layer being covered by resin, hindering the formation of a continuous conductive network, which significantly constrains their promotion and application in the field of proton exchange membrane fuel cells (PEMFC). In this paper, an ultra-thin flexible graphite/epoxy composite bipolar plates (BPs) with a thickness of only 0.775 mm is prepared followed by a process of flexible graphite preforming and impregnation curing. The hydrophilicity-modified BPs surface has a contact angle of 59.01° as well as flexural and compressive strengths of 11 MPa and 4 MPa and possesses a high in-plane conductivity of 380 S/cm and a low in-plane specific resistance of 6 mΩ cm2. The electrostack test results show that the hydrophilic runner channel is more conducive to the diffusion and spreading of H 2 O generated from the cathode-side reduction reaction in the flow channel, so that O 2 smoothly passes through the gas diffusion layer to participate in the reduction reaction of O 2 , and exhibits higher electric power at high current density, while the hydrophobically modified BPs has relatively poor overall performance due to ohmic losses. [Display omitted] • A hydrophilic flexible graphite bipolar plate with a contact angle of 59.01° is prepared. • The bipolar plates with excellent flexural strength of 11 MPa and a high in-plane conductivity of 380 S/cm. • The Electricstack has the best overall monolithic voltage and total power when the current density over 1800 mA/cm2. [ABSTRACT FROM AUTHOR]