Study On Preparation And Performance Of Bipolar Plate Composite Using Carbon Microspheres As Matrix

With the rapid development of industrialization,the problems of environment pollution and energy crisis become more and more prominent.Proton exchange membrane fuel cell(PEMFC),as a new form of energy,has drawn people's attention because of the advantages of high efficiency,energy saving and environmental protection,which is made up of three main parts,including membrane electrode,the sealing ring and the bipolar plate.Bipolar plates,as the core component of fuel cell,account for approximately 80% of the total stack weight and over 38% of the total stack cost.Therefore it's important to find bipolar plates which are easy to prepare,low-weight,cost-efficiency and high performance in the fields of fuel cells.In this paper,the preparation and performance of bipolar plates composite using carbon microspheres as matrix were studied.First of all,carbon microspheres was synthesized with glucose by hydrothermal method.The properties of carbon microsphere were characterized by FT-IR,XRD,SEM,Raman and TG-DTA,it's formation mechanism was disscussed.And then the carbon fillers(acetylene black,pitch based carbon microspheres,natural flake graphite and carbon nanotubes)was added to carbon microspheres respectively to develop the bipolar plate compositess through the process of ball milling,cold press molding and sintering.During this process,the ratio of additives,milling time,molding pressure and dwell time were changed to choose the best parameters by measuring electrical conductivity and flexural sterngth and observing its cross-section morphology.Eventually,bipolar plate compositess developed at the best parametres need to be measured such properties: corrosion resistance,bulk density,hydrophilicity and thermal stability.The research results indicated that the content of carbon filler,milling time and the molding pressure have a great influence on the overall performance of the composite,and they aren't indentical.In general,four kinds of carbon materials can be used to improve the conductivity of bipolar plates composite based on carbon microspheres,but superfluous acetylene black would reduce the conductivity,deteriorate the structure of bipolar plates and decrease the flexural strength due to agglomeration.Moreover,the conductivity of acetylene black itself is low,it has little effect on improving theperformance of bipolar plate composites.While 24 wt% carbon nanotubes(8 h,25 Mpa,5 min)are moderate for improving the performance of bipolar plates composite.Mesocarbon microbeads based on pitch and natural flake graphite has obviously improved on conductivity of bipolar plates,but taking into the effect of flexural strength account,32 wt%MCMB(2 h,25 MPa,5 min)based pitch and 32 wt%NG(6 h,25 MPa,5 min)was for the final selection,and the conductivity of bipolar plate composites obtained at this moment can reach up to 168.1 S/cm and 244.9 S/cm,respectively;though the flexural strength has a decrease compared with before,it still can meet the requirements of the US Department of energy(DOE).And these bipolar plate composites exhibit excellent perfoamance on hydrophobicity,thermal stability and corrosion resistance.