SOFC电解质薄膜制备技术研究进展

针对固体氧化物燃料电池(SOFC)电解质薄膜制备技术与电池性能研究进展进行了综述。SOFC是高效率的电源装置,但其效率严重依赖于电解质层的薄膜化。对比分析了目前电解质薄膜制备中使用的干压法、流延法、丝网印刷、浸涂法、溶胶凝胶法、电泳沉积、物理气相沉积、化学气相沉积、等离子喷涂等技术的优劣之处,并探讨了不同制备技术对电池综合性能的影响。     

用于燃料电池的氧化锆薄膜制备方法进展

固体氧化物燃料电池(SOFC)具有高效率、低污染等优点,氧化钇稳定氧化锆(YSZ)是目前用于SOFC的最成功的电解质材料,为了减小高温运行带来的困难,应用中需将YSZ制成薄膜。综述了制备YSZ 薄膜的各种方法,其中包括化学气相沉积(CVD)、电化学气相沉积(EVD)、溶胶-凝胶法(Sol-gel)和喷雾热解法等化学方法;物理气相沉积技术(PVD)和喷涂技术等物理方法;以及电泳沉积法(EPD)、注浆成型法和离心浇铸法等陶瓷成型方法,介绍了近年来采用上述方法制备的YSZ膜的性能及其用于SOFC电池研究取得的实验结果,最后评述了这些方法各自的特点。     

轧膜成型YSZ电解质薄片性能

探索了以YSZ纳米粉体为原料 ,采用轧膜成型的方法制备YSZ电解质薄片的工艺过程。结果表明 :轧膜坯体在14 5 0℃烧结最为适宜 ,保温时间应控制在 2h左右 ;同时 ,在 10 0 0℃附近的烧结初期 ,保温时间也应控制在 2h左右为宜。YSZ电导率在 95 0℃已达到 0 10S/cm以上 ,满足SOFC对电解质材料导电性的要求     

阳极支撑YSZ电解质薄膜的浆料旋涂法制备

用于压-预烧结法制备阳极支撑体,在阳极支撑体上用浆料旋涂-共烧结法制备了氧化钇稳定氧化锆(YSZ)电解质薄膜.实验考察了不同淀粉含量和不同预烧结温度对阳极支撑体预烧结效果的影响以及旋涂层数和浆料配比对YSZ电解质膜致密性的影响.结果表明:当阳极支撑体的预烧结温度为1 200℃,阳极支撑体中淀粉含量为15％,电解质的旋涂层数控制在5层或5层以下,旋涂浆料中YSZ的含量为45％时,制备的电解质薄膜致密性较好.对制备样品出现的缺陷进行了原因分析,提出了相应的解决办法.     

双层干压制备阳极支撑的氧化锆薄膜燃料电池

采用一种既简单又经济的双层干压法,NiO-YSZ阳极基底上制备致密的氧化钇稳定的氧化锆(YSZ)固体电解质薄膜,经1400!共烧结后,得到厚度约60"130mm的YSZ薄膜。薄膜的厚度可以通过调整YSZ粉体质量来控制。测试了NiO-YSZ支撑体材料和YSZ的干压坯体烧结曲线,以确定烧结收缩率。对薄膜进行的X-射线衍射(XRD)测量结果表明,薄膜为YSZ的立方萤石结构,NiO与YSZ在烧结条件下未发生反应。以此方法制备的不同厚度的YSZ薄膜为电解质,NiO-YSZ金属陶瓷为阳极,La0.7Sr0.3MnO(LSM)阴极制成固体氧化物燃料电池(SOFC)单电池,对单电池的放电性能及其在工作条件下的阻抗谱进行了测试。电池的开路电压始终在1V左右,900!最大电流密度达1.3A·cm#2。分别在800!和900!时得到了175mW·cm#2和300mW·cm#2的最大比功率。     

热电池用FeS_2/电解质复合薄膜正极的制备及性能

采用超声喷涂技术及丝网印刷薄膜化工艺制备了FeS_2/电解质隔膜复合薄膜正极,研究了薄膜正极中电解质添加量、三种碳材料导电剂及导电剂的不同添加量对单体电池放电性能的影响,通过扫描电子显微镜(SEM)对FeS_2正极在电解质隔膜上的表面形态进行了表征。实验结果表明,一体化薄膜正极中电解质添加量对正极材料的影响较小,含量为15%时较为适宜。一体化薄膜正极中乙炔黑、活性炭和CNTs的适宜添加量分别为3%,3%和1%。     

LiSi/FeS_2热电池薄膜正极性能影响因素的研究

采用丝网印刷薄膜化工艺制备了FeS2薄膜正极,研究了薄膜正极中电解质添加量、导电剂添加量和测试温度对单体电池放电性能的影响。实验结果表明,薄膜正极中电解质和导电剂的最佳添加量分别为20%(质量分数)和3%(质量分数)。在最优工艺下,其单体电池以100和200 mA/cm2恒流放电的平台电压分别约为1.80和1.74 V,截止电压为1.5 V时的放电比容量分别为316.2和326.7 mAh/g。此外,测试温度是一个较为敏感的因素,热电池的放电平台电压随测试温度的升高而增大。     

浸渍涂覆法制备YSZ电解质薄膜及其致密性表征

采用浸渍-涂覆的方法,以水热氧化钇稳定的氧化锆(YSZ)为原料,通过低温预烧,使8YSZ的收缩率小于阳极支撑体的收缩率,使得薄膜在烧结过程中始终受到阳极施加的压应力作用,从而避免了薄膜的开裂,经一次浸渍涂覆-干燥-烧结就制得了8YSZ电解质薄膜。所制备的薄膜具有良好的致密性,场发射扫描电镜(FE-SEM)观察发现薄膜表面和断面没有任何裂纹、针孔等瑕疵,薄膜不能被水透过,由薄膜构成的浓差电池两侧的开路电压接近理论电动势。     

阳极支撑固体氧化物燃料电池制备研究

制备了Ni/YS│YSZ│LSM[YSZ——Y2O3掺杂(稳定)的ZrO2;LSM——锰酸镧即La0.85Sr0.15MnO3]阳极支撑单体固体氧化物燃料电池(SOFC)。其中阳极基底、YSZ电解质薄膜和LSM阴极分别采用干压成型方法、浆料喷覆工艺和浆料涂覆法制备。考察了电池制备过程中影响电池品质的主要因素,指出基底不均匀性和焙烧升温速率过快是导致成型压力在25～250MPa范围内阳极基底翘曲和开裂的主要原因;影响阳极基底与YSZ电解质薄膜共焙烧匹配性的主要因素是成型压力、预焙烧温度和焙烧升温速率。应用扫描电子显微镜(SEM)表征了电池微观结构,YSZ电解质薄膜的厚度约为15～20mm。考察了电池电性能,800℃下,阳极H2进气流量为250mL·min-1时,电池开路电压1.0973V,最大比功率0.13W·cm-2。进一步优化电极结构,可制备高性能的阳极支撑SOFC。     

恒流电泳沉积YSZ电解质薄膜的燃料电池研究

采用恒流电泳沉积(EPD)的方法,在NiO-YSZ阳极基底上制备出较为致密的氧化钇稳定的氧化锆(YSZ)固体电解质薄膜,1300℃共烧结5h后得到具有一定厚度的YSZ薄膜。利用SEM对YSZ薄膜的形貌与膜厚进行了表征。在此基础上,以La0.6Sr0.4Co0.2Fe0.8O3(LSCF)为阴极制成单电池,并对单电池的性能及阻抗谱进行了测试,在650℃时得到单电池的最大开路电压为0.84V,单电池在750℃时的最大电流密度为0.64A/cm2,最大功率密度达145mW/cm2;800℃时的短路电流密度接近0.9A/cm2,最大功率密度达200mW/cm2。阻抗谱测试结果表明,电解质部分的电阻占电池内阻的1/4~1/3;电极在-电解质界面处存在的孔洞对电池的性能产生了不利的影响。     

Fabrication of anode supported PEN for solid oxide fuel cell

ConventionalSOFCsareusuallyoperatedat 10 0 0℃ Duetoitshighoperationaltemperature ,thematerialsdemandinguponSOFCcomponentsarequitestringent Manyresearchersaregradu allyinterestedinintermediatetemperaturesolidoxidefuelcell(IT SOFC) [1-2 ] TherearetwopossibleapproachesforloweringtheoperatingtemperatureofSOFCs Thefirstistoreducethethicknessofelec trolyte ,forexampletheelectrolyteinanode supportedplanar typesinglecellisonly 2 0 μm Thesecondistodevelophigherconducti vityelectrolyte .Inth…     

Direct-Write Fabrication of Integrated, Multilayer Ceramic Components

The need for advanced electronic ceramic components with smaller size, greater functionality and enhanced reliability requires the ability to integrate electronic ceramics in complex 3-D architectures. However, traditional tape casting and screen printing approaches are poorly suited to the requirements of rapid prototyping and small-lot manufacturing. To address this need, a direct-write approach for fabricating highly integrated, multilayer components using a Micropen to deposit slurries in precise patterns is being developed at Sandia. This approach provides the ability to fabricate multifunctional, multimaterial integrated ceramic components (MMICCs) in an agile and rapid way. Commercial ceramic thick-film pastes can be used directly in the system, as can polymer thick-film pastes (PTF). The quality of printed components depends on both the rheology and drying behavior of the pastes. Pastes with highly volatile solvents are inappropriate for the Micropen. This system has been used to make integrated passive devices such as RC filters, inductors, and voltage transformers.     

Fabrication and electrical properties of barium strontium titanate thick films by modified sol–gel method

A modified sol–gel method has been developed to prepare for the barium strontium titanate (Ba_0.6Sr_0.4TiO₃, BST) thick films. The films were deposited on either Pd–Ag electroded alumina substrates (Pd–Ag/Al₂O₃) or silver electroded alumina (Ag/Al₂O₃) substrates by spin coating technique or screen printing technique. The thickness of the film was in the range of 2–10 μm. The key point of the process is to disperse fine-grained BST ceramic powders prepared by high energy ball mill into BST sol solution to form a slurry for spin coating and screen printing. In order to enhance the stability of the slurry and to avoid crack formation of the thick film, organic macromolecular poly-vinylpyrrolidone (PVP) was added to the sol solution. The structure and surface morphology of the films were studied by X-ray diffraction and Scanning Electron Microscope (SEM) techniques. It is revealed that the thick films exhibit pure perovskite phase and are crack-free, dense and homogeneous. The dielectric constant and loss tangent of the thick films are about 1200 and 0.01, at 10 °C and 1 KHz, respectively.     

Screen-printed piezoceramic thick films for miniaturised devices

The development towards smaller devices with more functions integrated calls for new and improved manufacturing processes. The screen-printing process is quite well suited for miniaturised and integrated devices, since thick films can be produced in this manner without the need for further machining. On the other hand, the process of screen printing thick films involves potential problems of thermal matching and chemical compatibility at the processing temperatures between the functional film, the substrate and the electrodes. As an example of such a miniaturised device, a MEMS accelerometer based on PZT thick film will be presented. The design and process flow of this accelerometer has been optimised by means of finite element modelling (FEMLAB©). Consequently it has proved possible to eliminate post-processing steps after the screen printing of the PZT thick film.     

Screen Printed PZT Thick Films Using Composite Film Technology

A spin coating composite sol gel technique for producing lead zirconate titanate (PZT) thick films has been modified for use with screen printing techniques. The resulting screen printing technique can be used to produce 10 μm thick films in a single print. The resultant films are porous but the density can be increased through the use of repeated sol infiltration/pyrolysis treatments to yield a high density film. When fired at 710°C the composite screen printed films have dielectric and piezoelectric properties comparable to, or exceeding, those of films produced using a ‘conventional’ powder/glass frit/oil ink and fired at 890°C.     

ZnO-based varistor thick films with high non-linear electrical behavior

Thick films of ZnO-based ceramic varistors prepared by tape casting technique typically show a poor electrical response that still limits their application as protective devices. The excessive volatilization of Bi₂O₃ during sintering at high temperatures, especially dramatic in the film geometry due to its high area–volume ratio, is found to be the origin of this poor electrical behavior. The problem is overcome by sintering the films in a controlled Bi-rich sealed atmosphere, leading to a high reliability and reproducibility in their non-linear response.     

Preparation of Y-Ba-Cu-O tapes by pyrolysis of organic acid salts

High-T_C superconducting Y-Ba-Cu-O films were prepared on certain ceramic and metal substrates by pyrolysis of 2-ethylhexanoates. Only the films on MgO, yttria-stabilized zirconia (YSZ), and Ag substrates exhibited the superconducting transition above liquid nitrogen temperature. Transition temperatures (T_C) of 82, 85, and 82 K were observed in films of MgO, YSZ, and Ag substrates. The important factors in preparing superconducting films on substrates are the reactivity of the films and the substrates and the difference in their thermal expansions. The Y-Ba-Cu-O films were well suited for use with MgO, YSZ, and Ag substrates. Long superconducting tapes were produced on Ag substrate; flexible tape with a critical current density J_C of 3 · 10³ A/cm² at 77 K has now been prepared.     

Preparation and characterization of copper based cermet anodes for use in solid oxide fuel cells at intermediate temperatures

Two Cu-based anode cermets suitable for direct hydrocarbon oxidation in Solid Oxide Fuel Cells (SOFC) based on yttria stabilized zirconia (YSZ) electrolyte were tested in the temperature range (500–800°C). The ceramic components were CeO₂ and the perovskite La_0.75Sr_0.25Cr_0.5Mn_0.5O_3−d (LSCM). The cermets were made in both the form of pellets and films applied onto the YSZ electrolytes. Pellets exhibited good mechanical strength and resistance to fracture in both oxidized and reduced state. Cu–LSCM cermets exhibited good redox cycling behavior between 700–800°C. Reduction temperature plays a significant role on final morphology with Cu segregation occurring at 800°C. Cu–LSCM films were found to exhibit lower polarization resistances than Cu–CeO₂ under 5% H₂. Examination of the data revealed a poorer contact of the Cu–CeO₂ electrode with the YSZ surface than the Cu–LSCM electrode. Reduction temperature should be less than 750°C to ensure suitable microstructure and adhesion of both film electrodes with the electrolyte.     

Tailoring the pore structure of cathode supports for improving the electrochemical performance of solid oxide fuel cells

Two types of lanthanum doped strontium manganite (LSM)-yttria-stabilized zirconia (YSZ) composite cathodes were prepared, one with the finger-like straight open pores by the phase inversion tape casting, and the other with the randomly distributed tortuous pores by the conventional tape casting. A gas permeation flux of 42.5?×?10⁵ Lm^?2 h^?1 was measured under a trans-membrane pressure of 0.6 bar for the former while only 10.6?×?10⁵ Lm^?2 h^?1 for the latter. Fuel cells supported on the as-prepared LSM-YSZ composite cathodes were fabricated, comprising a 15 μm thick YSZ electrolyte layer and a 20 μm thick NiO-YSZ anode. The electrochemical performance of the fuel cells was measured using H₂ as fuels and air as oxidants. The cell supported on the phase-inversion derived cathode showed a maximum power density of 362 mWcm^?2 at 850 °C, while only 149 mWcm^?2 for the cell supported on the cathode formed by the conventional method. The difference in the electrochemical performance between the two cells can be attributed to the pore structure of the cathode supports. It is concluded that the phase inversion tape casting provides a simple and effective approach for tailoring the pore structure of the cathode support and thus enhancing the electrochemical performance.