| Composite graphite materials used to prepare proton exchange membrane fuel cell bipolar plates can improve the performance of proton exchange membrane fuel cells effectively in complex working environments by enhancing the operational reliability of proton exchange membrane fuel cells and reducing their manufacturing and maintenance costs.This makes them better suitable for power grid application scenarios.In this paper,natural flake graphite,phenolic resin and conductive carbon black were chosen as the conductive aggregate of composite graphite bipolar plates,the binder of bipolar plates,and the auxiliary conductive filler of bipolar plates,respectively.These raw materials were pressed into bipolar plates using the hot pressing method after being mixed via ball milling effectivley.In order to obtain the best fabricationg process parameters,such as the raw material ratio,molding time,temperature,pressure and others,the as-prepared bipolar plates were tested with the help of body resistance,mechanical strength,corrosion resistance,SEM scanning and other testing techniques.Then the bipolar plate with the optimized parameters was assembled into the fuel cell single cell and subjected to further measurements for determining its optimal working temperature,pressure,reaction gas flow and other conditions.After all these measurements were finnished,the performance of the finally obatined cell with the surface coating(Pt)of the composite graphite bipolar plate carried out using magnetron sputtering was tested.The obtained results suggested that the flexural strength of the bipolar plates increase with the increase of phenolic resin content and forming pressure,but the conductivity of the bipolar plates will be reduced with the increase or decrease of phenolic resin content,conductive carbon black content,forming temperature,time and pressure.The experiment shows that the mass fraction of natural flake graphite,phenolic resin and conductive carbon black in the raw materials is 79wt.%,16wt.%,and 5wt.%.The comprehensive performance of the composite graphite bipolar plate can reache the best with the molding temperature,the molding time,the molding pressure as 170℃,15min,and 40t,respectively.In this case,the maximum conductivity and flexural strength can reach 345 S/cm and 31.8 Mpa,respectively,which meet the requirements of the US DOE for fuel cell bipolar plates.Further measurements on the fuel cell test system shows that best work efficiency of the bipolar plate works can be obtained with all the remperatures of the battery temperature,the cathode and anode gas humidification temperature as 70℃.Moreover,the greater the reaction gas flow and internal back pressure,the better working performance. |
