Bipolar plates made from conductive polymer compounds, FHNW School of Engineering and Environment

• Fuel cells
• Conductive polymers
• Bipolar plates
• Variothermal injection compression molding

Soon, most engines will be powered electrically by batteries or fuel cells. One of the major factors limiting fuel cell commercialization is the development of bipolar plates. Their characteristic requirements are a challenge for any class of material, and none yet fully meets these requirements. Bipolar plates significantly influence the gravimetric and volumetric power density of a fuel cell, typically accounting for more than 80% of the weight of a stack and nearly two thirds of the volume.

The main goal of the project has been to produce polymer composite bipolar plates for polymer electrolyte membrane fuel cells. The plates had to fulfil the following characteristics: through thickness electrical conductivity > 50 S/cm, lightweight (maximum density of 1.7 g/cm3), temperature application up to 180°C, flexural strength >25 MPa and thickness of 0.5 mm.

The plates were produced in two sizes: 80cm² and 150cm² both with the characteristic micro-structured channels.

In the project we have successfully developed innovative polymer-based composites for fuel cell bipolar plates. The compounds developed and used showed good processability using a multi-filler approach with carbon-based fillers. This results in an electrical conductivity and flexural strength above DOE. Two different methods have been validated for the manufacturing and the up-scaling. Within these two approaches we could prove a good reproducibility of the micro channels of the bipolar plates.