LSGM电解质薄膜制备与电化学性能研究

【作者】 孙红燕；

【导师】 马文会；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2011， 硕士

【摘要】 固体氧化物燃料电池(SOFC)是一种将燃料的化学能直接转化为电能的能源转换装置,在环境友好和高效能源方面显示出很大的优势,越来越受到人们的重视。目前国际上固体氧化物燃料电池的发展趋势是将其操作温度中低温化(工作温度在800℃以下)。为保证电池具有良好的输出性能,La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM)电解质的薄膜化制备将传统的电解质支撑型SOFC转变为阳极支撑型是一种非常有前景的技术路线。本论文采用甘氨酸-硝酸盐法(Glycine-Nitrate Process, GNP)合成了LSGM电解质粉体和La0.7Sr0.3Cr0.5Mn0.5O3-δ(LSCM)阳极粉体,X射线衍射(XRD)和能谱分析(EDS)测试结果表明样品为纯相的钙钛矿型结构且各金属元素摩尔比满足实验设计的比例。为优化阳极支撑体的微观结构,研究了造孔剂种类和添加量对阳极支撑体表观性能的影响。研究结果表明采用8 wt.%淀粉作为造孔剂得到的阳极支撑体的孔隙率最大、微观结构最佳。采用浆料旋涂法制备了LSGM薄膜。旋涂法是通过高速旋转产生的离心力将悬浮液中的电解质颗粒沉积到阳极支撑体上。这种制膜方法简单,快捷,成品率高,而且成本低廉。研究了粘结剂和调和剂的种类和添加量,烘制温度,旋涂次数对LSGM薄膜性能的影响。研究结果表明,制备电解质浆料以5 wt.%乙基纤维素作为粘结剂、5 wt.%松油醇作为调和剂,薄膜重复旋涂9次在1400℃条件下烧结4h时,可以成功制备致密的表面略显粗糙的LSGM电解质薄膜。同时采用射频磁控溅射法制备LSGM电解质薄膜,研究了溅射过程中关键的工艺参数对薄膜性能的影响。实验过程中主要通过对薄膜微观结构、阳极/电解质界面的粘附状态、沉积速率的表征来优化工艺。确定最佳工艺参数：溅射压强为5 Pa,射频功率为210 W,基底温度为300℃。采用优化后的工艺参数获得的LSGM薄膜在空气中1000℃条件下退火处理2 h,所得到的薄膜致密度高,结晶性好,与阳极基底结合紧密。另外采用两电极半电池构造法测试分别采用射频磁控溅射法(1#半电池)和浆料旋涂法(2“半电池)在最佳条件下制备LSGM薄膜所组装半电池的电化学性能。由极化性能测试结果可得,线性扫描伏安曲线(Linear Scanning Voltammetry, LSV)和Tafel曲线所得的交换电流密度,1#半电池的交换电流密度均大于2#半电池。同时交流阻抗谱(AC Impedance Spetroscopy)测试结果表明：射频磁控溅射法制备的电解质薄膜的欧姆电阻小于旋涂法所制备的薄膜。电化学性能测试结果表明射频磁控溅射法较浆料旋涂法更适合用于制备中温固体氧化物燃料LSGM电解质薄膜。更多还原

【Abstract】 Solid oxide fuel cell (SOFC), which is an energy conversion device can convert the chemical energy of the fuel into electrical energy directly, has attracted more and more attention attributing to high efficiency and environmental protection. The key current research is the fabrication of SOFC operating at a lower temperature (the operation temperature below 800℃). In order to achieve predominant output of cell, reducing the thickness of LSGM electrolyte and transforming the traditional electrolyte-supported SOFC into anode-supported type is a promising technology route.LSGM and LSCM powders were synthesized via glycine-nitrate process. X-ray diffraction (XRD) and energy spectrum analysis (EDS) results showed that the as-prepared powders possessed a pure phase of perovskite type structure and the molar ratio of the metal elements met the ratio of experimental design. At the same time, for the purpose of optimizing the microstructure of the anode support, the effects of type and additive amount of pore-formers on the anode apparent performance were carefully investigated. The results show that the maximum porosity and best microstructure were obtained when 8 wt.% starch was selected as the pore-former.LSGM electrolyte film was fabricated by slurry spin coating process. The particles of LSGM in a suspension were deposited onto anode substrates through a centrifugal force by high-speed rotation. The method has an advantage of simple, fast, and cost-effective. The parameters related to the performance of the LSGM films including the type and additive amount of binder and modifier, heating temperature and spin-coating number were investigated finely. The electrolyte films with the best compactness and somewhat roughness were obtained when the operating parameters fixed as follows:the content of ethyl cellulose which acted as binder is 5 wt.%, the content of terpineol which acted as modifier is 5 wt.%, the optimum coating number is 9 times and the best post-deposition sintering temperature is 1400℃for 4 h. Furthermore, RF magnetron sputtering technique was also used to fabricate LSGM films. The influence of key sputtering parameters on the quality of LSGM film was systematically studied. The technical parameters were optimized by the film morphology observation, the deposition rate and the adhesion state of the anode/electrolyte bilayer in the course of experiments. Sputtering pressure of 5 Pa, RF power of 210 W and substrate temperature of 300℃were identified as the best technical parameters. Under these conditions, LSGM electrolyte film obtained by magnetron sputtering technology has a high density, good crystallinity, and well adhesive with anode substrates after being annealed at 1000℃for 2 h in air.In addition, a two-electrode half cell configuration was selected to investigate the electrochemical performance of the thin films which were fabricated under the optimum condtions with RF magnetron sputtering technique and slurry spin coating process labeled 1# half cell and 2# half cell, respectively. The exchange current density of 1# half cell was larger than that of 2# determined by LSV and Tafel curves. Furthermore, the AC impedance spectrum test results show that the resistance of the electrolyte film prepared by RF magnetron sputtering is less than that of slurry spin coating. The electrochemical performance test results showed that RF magnetron sputtering technology is more appropriate to prepare LSGM electrolyte film for SOFC than slurry spin coating method.更多还原