6 Classification of materials for BPs used in PEM fuel cell : Non-metal: Non-porous graphite plates Metals: Metal plates Composites: - Metal based - Carbon based : - Thermoplastics - Thermosets
7 Requirements for Bipolar Plates : Electrical conductivity : - DOE (the U.S.Department of Energy) > 100 S/cm - F.N.Büchi ≥ 10 S/cm (Development of a Bipolar Element for PE- fuel cell, demonstration in a 6 kW stack) - B.W.Choi ≥ 2.5 S/cm (higher than gas diffusion electrode) (J.Hydrogen energy 21 (1996))
8 The BPs have the following functions to perform : - To distribute the fuel and oxidant within the cell. - To facilitate water management within the cell. - To separate individual cells in the stack. - To carry current away from the cell. - To facilitate heat management.
9 Properties of BP : Electrical conductivity : plate resistance 0.01 cm 2 Thermal conductivity : as high as possible Hydrogen/gas permeability : 10 -4 cm 3 /scm 2 Corrosion resistance : corrosion rate 0.016 mA/cm 2 Compressive strength : 22 lb/in 2 Density : 5 gm/cm 2
15 Table 4 : ABS: CF : G Composites Conductivity, S/cm ABS : CF 1 : G 40 : 20 : 40 0.10 ABS : CF 2 : G 40 : 20 : 40 0.30 - CF1 length = 3 mm - CF2 length = 5 mm - The effect of CF length : longer CF higher conductivity
16 Discussion and Conclusion : - Add carbon fiber to improve the conductivity of ABS composites. - The effect of content and composition of fillers and the incorporation of fillers including the length of carbon fiber on the electrical properties of polymer composite were studied.
17 References: (1) A. Hermann, T. Chaudhuri and P. Spagnol (2005), “Bipolar plates for PEM fuel cells : A review”, International Journal of Hydrogen Energy, 30, 1297-1302. (2) H-C. Kuan, C-C. M. Ma, K. H. Chen and S-M. Chen (2004), “Preparation, electrical, mechanical and thermal properties of composite bipolar plate for a fuel cell”, Journal of Power Sources, 134, 7-14. (3) W. Thongruang, R. J. Spontak and C. M. Balik (2002), “Bridged double percolation in conductive polymer composites: an electrical conductivity, morphology and mechanical property study”, Polymer, 43, 3717-3725.