Effect of Stannum on Properties of Graphite/Stannum Composite for Bipolar Plate

Abstract

Over the past decade, rapid progress has been made in the understanding and development of Hybrid Conductive Composite (HCC) to be used as bipolar plate, one of the most important components in Polymer Exchange Membrane Fuel Cell (PEMFC). The formation processes of HCC and loading ratios of composite have significant effects on their properties especially electrical and mechanical properties. Thus, the research focuses on Graphite (Gr) as a filler and Stannum (Sn) as a binder in fabrication of HCC as a bipolar plate. The fabrication process began with Gr and Sn needed to dry mixed used ball mill with several ratios of loading, which are 60/40, 70/30 and 80/20 respectively. The shape of this composite was molded with a diameter of 25 mm through hot compression machine to form discs. The effect of different loadings on the properties such as electrical conductivity, bulk density and microstructure were observed and confirmed to be able to meet the DOE target properties as PEMFC bipolar plates. The result showed that Gr/Sn composite with 20 wt% Sn had the highest electrical conductivity which was 720 S/cm. In the other side, the bulk density showed decrement as Sn contents increased from 1.71 to 1.48 g/cm3. The findings promise an enhanced performance of HCC as a bipolar plate to be used in PEMFC which is beneficial for mobile and portable application industry. A further study on agglomeration and the mechanical properties such as the flexure strength and hardness should be pursued.