Mechanism of Lowering the Resistivity of Composites used for PEFC and Endurance Test of Them

聚合物/炭黑复合材料在质子交换膜燃料电池中具有良好的隔膜性能。它对电流产生方向的电阻率要求低，弯曲强度和弯曲应变的力学性能及其耐热性能都很强。[第一物理年]选择热弹性聚合物(TPE)作为粘结树脂。(1)研究了旧炭黑(CB)形状对电阻率的影响。选择了球形和片状CB。球形炭黑(SG)与热塑性弹性体(TPE)制备的复合材料比片状CB制备的复合材料具有更低的电阻率和更高的高温力学性能。(2)负载CB降低电阻率的机理是霍尔迁移率的变化，而不是载流子浓度的变化。[上个物理年度]为了获得更高的耐热复合材料，本年度采用了其他聚合物，如聚丙烯(PP)和聚苯硫醚(PPS)。有机-无机杂化MAD…用聚二甲基硅氧烷(PDMS)和硅酸乙酯(ES)作为粘结剂，以溶胶状态与SG混合。(3)最低电阻率为几十mLi-CRA，高于NEDO设定的小于10mq·cm的目标电阻率。用PPS和SG制得的复合材料的弯曲强度在50 Mpa以上，弯曲应变在1%以上，达到了NEDO的目标。(4)有机-无机杂化和SG制备的复合材料比其他复合材料的电阻率提高了10倍以上，机械强度降低了1/10。这需要通过改变PDMS的相对分子质量和改善凝胶条件来进一步研究。(5)用PPS和SG制成的复合材料在密闭容器水中140℃×600小时的耐久试验中，电阻率和力学性能没有变化。(6)尽管TPE的耐热性能并不比PP和PPS好，但用TPE和SG制成了隔膜。采用装有隔膜的单电池进行了电流-电压、交流阻抗和恒流运行试验。研究表明，为提高质子交换膜燃料电池的性能，隔膜的电阻率应进一步降低。较少

Composites made with polymer and carbon black have a potential to separator used in PEFC. It requires a low resistivity to the direction of generated current flow, strong mechanical properties of bending strength and bending strain and their heat-resistive property.[First Physical Year] A thermo-elastic polymer (TPE) was selected as a binder resin.(1) Dependence of resistivity on the shape of used carbon blacks (CB's) has been studied. Spherical and flake shaped CB's have been chosen. The composite made with spherical CB (SG) and TPE showed lower resistivity and stronger mechanical properties in high temperatures than that made with flake CB.(2) The mechanism of lowering resistivity with loading CB is explained by the change in Hall mobility rather than the change in carrier density.[ Last Physical Year ] In order to get more heat resistive composites, other polymers such as pllypropylene (pp) and polyphenylene sulfide (PPS) have been employed in this year. Organic-inorganic hybrid mad … More e with polydimethylsiloxane (PDMS) and ethyl silicate (ES) is also used as a binder and it is mixed with SG in a sol state.(3) The lowest resistivity is several tens mLI-cra which is higher than the goal resistivity less than 10 mQ-cm which was set by NEDO. The NEDO goals for bending strength of above 50 MPa and bending strain of above 1 % are obtained by making the composite with PPS and SG.(4) The composites made with organic-inorganic hybrid and SG have shown higher resistivity by ten times and lower mechanical strength by one-tenth than other composites. That requires further studies by changing the molecular weight of PDMS and by improving gel conditions.(5) The composites made with PPS and SG showed no change of resistivity and mechanical property under the endurance test of 140oCX600hrs in a well-closed container water.(6) Although TPE did not have a better heat resistive property than PP and PPS, a separator was made with TPE and SG. A single cell equipped with the separator was employed for the tests of current-voltage, ac impedance and constant current running. It has been shown that the resistivity of the separator should be more reduced for higher performance of PEFC. Less