Conductive materials for polymeric bipolar plates: electrical, thermal and mechanical properties of polyethylene-carbon black/graphite/magnetite blends

The elimination of corrosion, reduction of mass and the improvement of mechanical, electrical and thermal conductivity properties are the main aims to progress bipolar plate technology for polymer electrolyte membrane fuel cells. In addition, the large numbers of bipolar plates required in automotive fuel cell stacks (on the order of 400 plates per vehicle) will demand mass production to meet future demands as well as reduce costs through cheap production processes. Highly conductive, low density, low cost and corrosion-resistant materials that can be utilised in production processes such as injection and compression moulding are ideal candidates for bipolar plates. Carbon black, graphite, magnetite with polyethylene composites were made and tested for their electrical and thermal conductivities and mechanical properties and compared to the US Department of Energy targets for 2015. The carbon black composites exhibited better electrical conductivity than the other fillers where at 65 wt% the conductivity was ∼24 S/cm for through-plane conductivity and had a flexural strength of ∼32 MPa. Injection moulding produced composites with more material stability and greater mechanical strength than compression mouldings although compression mouldings produced composites with higher thermal conductivities where graphite displayed the highest thermal conductivity of ∼2 W/mK. Although well short of the US Department of Energy targets these materials show promise