【作者】 柳勇；

【导师】 唐致远；

【作者基本信息】 天津大学 ， 应用化学， 2012， 博士

【摘要】 固体氧化物燃料电池（Solid Oxide Fuel Cell,SOFC）是一种将化学能直接转化成电能的能量转换系统,具有高能量转换效率、全固态结构、无污染和多种燃料气体适应性强等优点。作为SOFC的核心部件,电解质材料一直研究的热点。本论文在第一章介绍了SOFC的基本原理,目前国内外的研发现状和发展趋势,着重综述了SOFC电解质材料的研究动态。第三章对BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ（BZCYYb）这一新材料进行了优化,得到了迄今为止BZCYYb最高的电导率;并且首次测试并计算了其理论密度,首次研究了其烧结性能,增加了对这一新型材料的认识,为其在其他领域的应用提供了实验依据,填补了实验和理论空白（第四章）。本文在第五章又对新型电解质材料NASICON（Na+ Super Ionic Conductor）材料及其在燃料电池领域的应用进行了研究,另外还对橄榄石型和石榴石型锂离子导体材料进行了探讨。所取得的主要成果和创新点可归纳如下:（1）采用固相反应法成功合成了不同Y/Yb比的BZCYYb,X射线谱图显示,所有的粉末都具有与BaCeO₃相类似的钙钛矿结构;当Yb的量为10%,其电导率最高。以微米级CeO₂和纳米级ZrO₂为前驱体、焙烧两次、焙烧温度为1100oC时固相反应法制备的BZCYYb粉体晶体结构中无明显杂相,烧结出来的片体致密,且电导率为最高。（2）首次对BZCYYb材料的的理论密度进行了测试和计算,约为6.211g·cm^-3。（3）烧结性能方面,在高温固相合成法制备的BZCYYb粉体中加入少量（质量百分比1%,1wt%）NiO有助于其烧结过程中的晶粒长大和致密度增加,即提高烧结性能,优于LiF和Al₂O₃等其他烧结助剂。1wt%NiO的加入,可以有效降低BZCYYb的烧结温度约200oC,并且不会影响其电导率,另外,以其为电解质做成的电池在燃料电池测试条件下的开路电压高且能够满足燃料电池使用的需要。首次创新性的以1wt%NiO为烧结助剂,成功采用固相反应烧结法合成了BZCYYb片体,电导率与用普通固相反应法合成片体的电导率相接近。（4）采用高温固相法成功合成了Na₅GdSi₄O₁₂（NGS）粉体,其在1060oC下空气中烧结3小时烧结的片体致密,电导率与文献报道的相当。并首次将其用做燃料电池的电解质,实验表明,其开路电压较高,1.2mm厚的电解质片做成电池后,其功率密度在500oC下的达到0.5mW/cm²。另外,将其进行锂离子交换后,其结构有所变化,并且有向非晶态转化的趋势。其电导率大幅降低,且活化能大幅增加。（5）采用高温固相法成功合成了橄榄石型结构LiInGeO₄和LiIn_1-xM_xGeO₄(M=Ti⁴⁺, Zr⁴⁺和Nb⁵⁺,x=0.1⁰.2)粉体,X射线衍射谱图表明,当不掺杂和掺杂元素为Zr⁺,x=0.1时,可以得到纯相,而当掺杂元素为Ti⁴⁺和Nb⁵⁺时,均不能得到纯相。LiInGeO₄和Li_0.9In_0.9Zr_0.1GeO₄粉体烧结后的片体的电导率均较低。采用高温固相法合成了石榴石型结构Li₇La₃Zr₂O₁₂粉体,X射线衍射谱图表明,经过900oC和1125oC焙烧之后的Li₇La₃Zr₂O₁₂粉体具有四方晶型结构,而经过1230oC长时间烧结过后的片体,其结构主要为La₂Zr₂O₇,另外本文还就热重-差热分析数据,对可能的实验构造和反应机理进行了分析。更多还原

【Abstract】 Solid oxide fuel cell （SOFC） is an efficient, green energy conversion device, which can directly convert the fossil energy into electrical power, which has many advantages, such as high energy conversion efficiency, solid-state structure, and a wide range of adaptability of fuel gases, etc. As the core component of SOFC, the electrolyte is always the hot-pot. The basic theory, the state-of-art of SOFC and the electrolyte were reviewed in the Chapter 1. The fabrication of BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ（BZCYYb）, a new electrolyte for SOFC, were optimized and the BZCYYb with highest conductivity was got in the Chapter 3; In the Chapter 4, the theoretical density of BZCYYb was measured and calculated for the first time and we systematically studied the sinterability of BZCYYb, which is favorable for its application in other field. In the Chapter 5, we discussed the new electrolyte systems, NASICON materials and its application as an electrolyte in the SOFC, and Olivine and Garnet type lithium ion conductors were also discussed.The main results and the creative points could be concluded as below:（1） The different Y/Yb ratio BZCYYb materials were successfully fabricated by solid state reaction （SSR） method, and the X-ray diffraction shows all the powder has perovskite structure. And the conductivity is the highest when the amount of Yb is 10% in BZCYYb. The powder, which was fabricated by the precursor made ofμm CeO₂ and nm ZrO₂ and two times calcinations and the calcinations temperature is 1100oC, has no obvious impurities in the X-ray diffraction test and the corresponding pellets have the highest conductivity,.（2） The theorectical density of BZCYYb materials was calculated for the first time, and its value is about 6.211g·cm^-3.（3） The addition of a small amount （¹wt%） of NiO to BZCYYb, which was fabricated by SSR method, greatly promoted densification and grain growth, which is better than other sintering aids （LiF and Al₂O₃）, achieving ⁹6% of the theoretical density （reducing the sintering temperature by ²00oC）. Further, the sample showed high open circuit voltages （OCV） when used as the electrolyte membrane to separate the two electrodes under typical SOFC operating conditions, indicating that the electrical conductivity of the BZCYYb was not adversely affected by the addition of ¹ wt % NiO. The solid state reactive sintering method was conducted for the first time with NiO as sintering aid for the BZCYYb material, and the result showed that the conductivity is close to the BZCYYb pellets which are fabricated by the traditional solid state reaction method.（4） The Na₅GdSi₄O₁₂ （NGS） powder was successfully fabricated through the SSR method, and the pellets made from the powder after sintering at 1060oC were dense, and its conductivity was close to the literature. The NGS pellets were used as the electrolyte for SOFC for the first time, and it has high open circuit voltage, and its powder density could reach 0.5mW/cm2 at 500oC with the electrolyte thickness of 1.2mm. Further more, the NGS structure changed a lot after lithium ion exchange. And after lithium ion exchange, the conductivity of the pellet became lower and the activation energy became higher. The LiInGeO4 and LiIn1-xMxGeO4(M=Ti⁴⁺, Zr⁴⁺ and Nb5+,x=0.1-0.2) material were successfully fabricated via SSR method. The X-ray diffraction showed that when no dopant and the dopant is Zr+, x=0.1, the pure phase could be got. But, when the dopant is Ti⁴⁺ or Nb⁵⁺, there is always some impurity in the powder. The conductivity of LiInGeO4 and Li0.9In0.9Zr0.1GeO4 were low. The Li₇La₃Zr₂O₁₂ powder was successfully fabricated through SSR method. The X-ray diffraction shows that the Li₇La₃Zr₂O₁₂ had tetragonal structure after calcinations at 900oC and 1125oC. But after 1230oC sintering for a long time, the main phase changed to La₂Zr₂O₇. Furthermore, the structure of the experiment and the mechanism of the reaction were also discussed.更多还原