具有Fe过渡层的新型燃料电池阳极的制备和性能研究

发布时间：2019-02-18 11:48

【摘要】：固体氧化物燃料电池(SOFC)是一种直接将化学能转化成电能的全固态结构发电装置,因其具有环境友好、燃料利用效率高、燃料使用范围广等诸多优势而备受关注。传统的SOFC工作温度常在800°C甚至更高,高温运行带来许多棘手问题,影响电池的普及和推广。为了避免高温运行带来的不利影响,降低电池的运行温度成为近年来研究的热门方向。La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM)是一种优异的中温电解质材料,在600~800°C表现出优异的氧离子导电特性,其离子迁移数在很宽的氧分压范围内(10-22-1 atm)为1,而且机械强度高、化学稳定性好,是一种很有希望的中温SOFC电解质材料。然而,已有研究表明LSGM电解质材料容易与电池的Ni基阳极发生高温化学反应,形成高电阻相如La Ni O3、La Sr Ga3O7以及La Sr Ga O4,显著降低电池的输出性能。目前,解决此问题的主流方案是将La2O3掺杂的Ce O2(LDC)引入Ni基阳极与LSGM之间形成过渡层,避免Ni与LSGM直接接触而发生高温化学反应。LDC过渡层虽可有效抑制Ni/LSGM间的化学反应,但其离子电导率远远低于LSGM,势必会大幅度增加电池的欧姆内阻。本论文尝试开辟一条新思路,制备Ni含量呈梯度分布的阳极支撑体,并在Ni基梯度阳极与LSGM电解质薄膜之间引入一层Fe过渡层。此方案具有以下两个优势:其一,Fe过渡层可阻隔LSGM和Ni基阳极共烧结时的高温固态化学反应;其二,高温共烧结时Ni/Fe层之间的元素相互扩散可实现电化学性能优于纯Ni阳极的Ni-Fe合金阳极的原位形成。在成功制备新型阳极的基础上,对电池的输出性能、交流阻抗谱、Ni/Fe元素的相互扩散和微观结构进行测试和分析。La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM9182)粉末采用固相反应法制备,经1400°C烧结后的XRD测试结果表明,粉体主相为LSGM9182,同时伴有少量的杂相。将LSGM9182粉体压片烧结后进行高温电导率测试,在700°C、750°C和800°C下的电导率分别为0.016 S?cm-1、0.026 S?cm-1和0.037 S?cm-1。作为对照,本论文首先利用固相法合成的LSGM粉体制备不含有Fe过渡层的SOFC单电池,分别制备Ni基阳极支撑型单电池和电解质支撑型单电池。阳极支撑型SOFC在800oC时开路电压为0.623 V,最大输出功率约为9.05 m W?cm-2,电解质支撑型SOFC在800oC时开路电压为1.05 V,最大功率密度为38.9 m W?cm-2。分析电池微观结构可以发现电池输出功率低、阻抗大均源于Ni与LSMG电解质之间的高温反应。能谱测试和EDX线扫描测试结果显示Ni元素在LSGM电解质膜内的扩散深度达到17μm。采用干压法制备(Ni O+GDC)/(Fe2O3+GDC)和(Ni O+YSZ)/(Fe2O3+YSZ)界面,用来模拟阳极制备阶段的界面,研究SOFC工况下整齐界面上的元素扩散情况,在不同的烧结温度下,研究界面模型中Ni向富Fe层扩散的深度。根据Ni元素的扩散深度对富Fe层的厚度及Fe含量进行优化。结果表明,而当Fe2O3与GDC的质量比为6:4时,GDC可以连接成为骨架,保证电极的机械性能同时增大三相反应区面积。根据1000°C和1400°C烧结样品测试Ni/Fe元素的相互扩散情况,为了实现富Fe层对Ni元素的吸纳阻隔作用,同时避免增大电池的极化阻抗,将富Fe层的厚度确定为15μm。实际制作单体电池时,为增加材料间的收缩匹配性及电池组件的机械强度,采用YSZ作为复合阳极中的离子导电相。在传统的阳极支撑体电池的基础上,增加新型阳极层,制备新型单电池。分别制备阳极支撑型SOFC和电解质支撑型SOFC,电池最佳还原温度为700°C。阳极支撑型SOFC在800°C时开路电压为0.718 V,最大功率密度约为740 m W?cm-2。即使开路电压偏离理论值,但电池仍能有较高的功率密度,与不含Fe层的阳极支撑型SOFC相比,最大功率密度存在两个数量级的差异,证明Fe层的引入对于改善电池输出性能有着极大的作用。电解质支撑型电池在800°C时开路电压为1.08 V,最大功率密度为148 m W?cm-2,较无Fe层的电解质支撑型SOFC,输出性能也有明显提高。电池测试前后EDX线扫描显示无La元素扩散进入Ni层阳极中,电解质中Ni元素扩散深度及含量有明显减小。富Fe层阳极的引入,对于阻挡Ni元素的扩散、改善电池的输出性能有着至关重要的作用。
[Abstract]:The solid oxide fuel cell (SOFC) is an all-solid-state power generation device which directly converts chemical energy into electric energy, and has the advantages of being environment-friendly, high in fuel utilization efficiency, wide in fuel application range and the like. The traditional SOFC operating temperature is often at 800 掳 C or even higher, and the high-temperature operation brings many difficult problems, affecting the popularization and promotion of the battery. In order to avoid the adverse effect brought by high-temperature operation, the running temperature of the battery is reduced to become the hot trend of the research in recent years. La0. 9Sr0. 1Ga0. 8Mg0. 2O3-1 (LSGM) is an excellent medium-temperature electrolyte material, exhibits excellent oxygen ion conductivity at 600-800 掳 C, and its ion migration number is 1 in a wide oxygen partial pressure range (10-22-1 atm), and has high mechanical strength and good chemical stability. is a very promising medium temperature SOFC electrolyte material. However, it has been found that the LSGM electrolyte material is easy to react with the Ni-based anode of the cell to form a high-resistance phase such as La Ni O3, La Sr Ga3O7 and La Sr Ga O4, which significantly reduces the output performance of the battery. At present, the main scheme to solve this problem is to introduce the La2O3-doped CeO _ 2 (LDC) into the transition layer between the Ni-based anode and the LSGM, so as to avoid the direct contact of Ni with the LSGM to generate a high-temperature chemical reaction. The LDC transition layer can effectively inhibit the chemical reaction between Ni/ LSGM, but its ionic conductivity is much lower than that of LSGM, which will greatly increase the ohmic resistance of the cell. A new idea was made to prepare the anode support with a gradient distribution of Ni content, and a layer of Fe transition layer was introduced between the Ni-based gradient anode and the LSGM electrolyte membrane. The scheme has the following advantages: firstly, the Fe transition layer can block the high-temperature solid-state chemical reaction in the co-sintering of the LSGM and the Ni-based anode; secondly, the mutual diffusion of the elements between the Ni/ Fe layers during the high-temperature co-sintering can realize the in-situ formation of the Ni-Fe alloy anode which is superior to the pure Ni anode. On the basis of successfully preparing a new type of anode, the output performance, the AC impedance spectrum and the Ni/ Fe element diffusion and microstructure of the battery were tested and analyzed. La0. 9Sr0. 1Ga0. 8Mg0. 2O3-1 (LSGM9182) powder was prepared by solid-phase reaction. The results of XRD test at 1400 掳 C show that the main phase of the powder is LSGM9182, accompanied by a small amount of heterophase. The electrical conductivity at 700 掳 C, 750 掳 C and 800 掳 C was 0.016 S? cm-1, 0. 026 S? cm-1 and 0.037 S? cm-1 at 700 掳 C, 750 掳 C and 800 掳 C, respectively, after the LSGM9182 powder was pressed and sintered. In this paper, a single cell of SOFC with no Fe transition layer was prepared by using the LSGM powder synthesized by the solid-phase method, and the Ni-based anode-supported single cell and the electrolyte-supported single cell were respectively prepared. The open-circuit voltage of the anode-supported SOFC at 800oC is 0.236V, the maximum output power is about 9.05m W? cm-2, the open-circuit voltage of the electrolyte-supported SOFC at 800oC is 1. 05V and the maximum power density is 38. 9 m W? cm-2. The analysis of the microstructure of the cell can find that the output power of the battery is low and the impedance is large, which results from the high temperature reaction between the Ni and the LSMG electrolyte. The results show that the diffusion depth of the Ni element in the LSGM electrolyte membrane reaches 17. m u.m. The interface of the (Ni O + GDC)/ (Fe2O3 + GDC) and (Ni O + YSZ)/ (Fe2O3 + YSZ) interface is prepared by the dry-pressure method, which is used to simulate the interface of the preparation phase of the anode. The diffusion of Ni to the Fe-rich layer in the interface model was studied under different sintering temperatures. and the thickness and the Fe content of the Fe-rich layer are optimized according to the diffusion depth of the Ni element. The results show that, when the mass ratio of Fe2O3 and GDC is 6: 4, the GDC can be connected to the framework to ensure the mechanical properties of the electrode and increase the area of the three-phase reaction zone. in ord to realize that absorption and blocking effect of the Fe-rich layer on the Ni element, the thickness of the Fe-rich layer is determined to be 15. m YSZ is used as the ion-conducting phase in the composite anode in order to increase the shrinkage-matching property between the materials and the mechanical strength of the battery pack. on the basis of the traditional anode support cell, the novel anode layer is added, and a novel single cell is prepared. An anode-supported SOFC and an electrolyte-supported SOFC were prepared. The best reduction temperature of the cell was 700 掳 C. The open-circuit voltage of the anode-supported SOFC at 800 掳 C was 0.718 V and the maximum power density was about 740 m W? cm-2. Even if the open-circuit voltage deviates from the theoretical value, the battery can still have higher power density, compared with the anode-supported SOFC with no Fe-layer, there are two orders of magnitude difference in the maximum power density, and it is proved that the introduction of the Fe layer has a great effect on improving the output performance of the battery. The open-circuit voltage of the electrolyte-supported cell at 800 掳 C is 1.08 V, the maximum power density is 148 m W? cm-2, and the output performance of the electrolyte-supported SOFC with no Fe layer is obviously improved. The EDX line scan showed no La element diffusion into the anode of Ni layer before and after battery test, and the diffusion depth and content of Ni element in the electrolyte were significantly reduced. The introduction of the Fe-rich layer anode plays an important role in the diffusion of the barrier Ni element and the improvement of the output performance of the battery.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O611.4;TM911.4

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