中低温SOFC电极材料及电解质材料研究

发布时间：2018-06-02 16:51

  本文选题：固体氧化物燃料电池 + 双钙钛矿　； 参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：固体氧化物燃料电池(SOFC)正朝着中低温化的趋势发展,而开发性能优异的中低温电极材料和电解质材料是其关键。Sr_2CoRO_6(R=Mo,Nb)双钙钛矿材料是一种潜在的中低温电极材料,本文对其电导率和导电机理进行了研究。另外,La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(2.85)(LSGM)是非常有潜力的中温区电解质材料,但其性能在更低温度下仍无法让人满意,因此本文采用两相复合的手段对LSGM进行了改性研究。采用固相法合成Sr_2CoRO_6双钙钛矿材料,主要对其元素价态、晶体结构和电导率进行了分析,并建立了电子导电通道模型。XPS分析结果表明Sr_2CoMoO_6和Sr_2CoNbO_6中Co元素的主要价态分别为+2和+3。利用XRD研究Sr_2CoRO_6的晶体结构,并用Rietveld法计算其点阵参数用于构建导电通道模型。采用四段子法测试Sr_2CoRO_6不同氧分压下的电导率,结果表明,空气中Sr_2CoMoO_6的电导率(0.36 S·cm~(-1),973 K)远低于Sr_2CoNbO_6(7.81 S·cm~(-1),973 K)。Sr_2CoMoO_6的电导率随氧分压降低而增大,在温度为973 K,氧分压为10~(-2)1 atm时,达到2.05S·cm~(-1);Sr_2CoNbO_6则随氧分压降低而大幅减小。利用电子导电通道模型对Sr_2CoRO_6的导电特性进行了阐释。制备了(100-x)wt.%La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(2.85)-x wt.%Ce_(0.8)Gd_(0.2)O_(1.9)(x=0、5、10、20)电解质材料,利用XRD对其物相进行了研究,并采用Rietveld法计算其点阵参数。采用交流阻抗法对其阻抗进行测试,结果表明:当温度在300~500℃时,其晶内电阻和晶界电阻均随x的增大而增大;在650℃以后,总电阻随x增大先减小后增大,x=5时取最小值。电池性能测试结果表明以95 wt.%La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(2.85)-5 wt.%Ce_(0.8)Gd_(0.2)O_(1.9)为电解质的电池在800℃时具有最优异的性能,最大电流密度为720 mA·cm~(-2),最高功率密度为192 mW·cm~(-2)。采用浸润法制备了La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(2.85)-(Li_(0.48)Na_(0.52))_2CO_3复合电解质,探讨了不同含量PMMA造孔剂对其形貌及电导率的影响。结果表明:基体孔隙率随PMMA含量增加而提高;复合电解质的电导率随PMMA含量的增加而增大,当PMMA含量为40 wt.%时,其电导率在600℃达到0.09 S·cm~(-1)。
[Abstract]:Solid oxide fuel cells (SOFCCs) are developing towards moderate and low temperature, and the development of excellent performance electrode materials and electrolyte materials is the key. Sr2CoRO6C / Nb) double perovskite is a potential medium and low temperature electrode material. In this paper, the conductivity and conduction mechanism are studied. In addition, LSGM is a potential electrolyte material in the medium temperature region, but its properties are still not satisfactory at lower temperature. Therefore, the modification of LSGM by two-phase composite method has been carried out in this paper. Sr_2CoRO_6 double perovskite materials were synthesized by solid state method. The elemental valence states, crystal structure and conductivity were analyzed. The electron conduction channel model was established. The results showed that the main valence states of Co in Sr_2CoMoO_6 and Sr_2CoNbO_6 were 2 and 3 respectively. The crystal structure of Sr_2CoRO_6 is studied by XRD, and the lattice parameters of Sr_2CoRO_6 are calculated by Rietveld method. The electrical conductivity of Sr_2CoRO_6 at different oxygen partial pressures was measured by four-stage method. The results showed that the conductivity of Sr_2CoMoO_6 in air was 0.36s / cm ~ (-1) ~ (-1) K), which was much lower than that of Sr_2CoNbO_6(7.81 S / C ~ (-1) K).Sr_2CoMoO_6 with the decrease of oxygen partial pressure. When the temperature was 973K and the oxygen partial pressure was 10-21 atm, the electrical conductivity of Sr_2CoMoO_6 in air increased with the decrease of oxygen partial pressure. Up to 2.05s cm-1, Sr2CoNbOS6 decreases significantly with the decrease of oxygen partial pressure. The conductive properties of Sr_2CoRO_6 are explained by using the electronic conduction channel model. The electrolytes of 100-xuwt.tig0.Ga0.Ga0.mg-0.2O / T ~ (2.85) -x ~ (WTT) have been prepared and their phase has been studied by means of XRD, and the lattice parameters have been calculated by means of Rietveld method. The electrolytes of this material have been studied by using the XRD method, and the structure of the electrolytes has been studied by means of the method of "XRD" and the method of "Rietveld" has been used to calculate the lattice parameters of the electrolytes. The impedance is measured by AC impedance method. The results show that both the intragranular resistance and grain boundary resistance increase with the increase of x when the temperature is 300 ~ 500 鈩，

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