燃烧法制备中温SOFC电解质及其电极材料

采用一种新的燃烧合成陶瓷粉体的方法——硝酸盐-柠檬酸盐燃烧法低温合成中温SOFC所有元件的初始粉体并组装成单电池，电池的电解质材料为Ce0.8Gd0.2O1.9，阴极材料为掺杂一定量固体电解质的La0.6Sr0．4Fe0.8Co0.2O3，阳极材料为固体电解质与NiO的复合材料。单电池的性能测试结果表明：单电池的输出电压和输出电流皆随其运行温度升高而增大，同时单电池的开路电压随温度升高而下降。以Ce0.8Gd0.2O1.9电解质材料为电解质的单电池在750℃的最大输出功率密度约为85mW／cm^2。     

La0．7Sr0．3Cu1-xFexO3-δ系阴极材料的制备与性能研究

采用固相法和EDTA-柠檬酸联合络合法制备了中温固体氧化物燃料电池La0．7Sr0．3Cu1-xFexO3-δ阴极材料，利用直流四探针和交流阻抗技术测试了材料的导电性能和电化学性能，结果表明加入Fe后材料的电导率有所降低，但在高温下仍然具有较高的电导率（〉100 S·cm^-1）。EDTA-柠檬酸联合络合法制备的试样比固相法合成的具有更高的电导率（在800℃时，EDTA-柠檬酸联合络合法制备的试样电导率为255 S·cm^-1，而固相法的为156S·cm^-1。）700℃时的复阻抗测试结果表明Fe的加入降低了La0．7Sr0．3CuO3-δ的极化电阻，其中La0．7Sr0．3Cu0.4Fe0.6O3-δ的极化电阻最小，为2．51Ω·cm^2。     

中温SOFC复合阴极材料的制备及性能

在La0.7Sr0.3Co0.95Cu0.05O3-δ中掺入不同比例的Ce0.8Sm0.2O1.9制成中温固体氧化物燃料电池(IT-SOFC)复合阴极材料,对其进行晶体结构表征和高温电导率、热膨胀系数和阴极过电位测试.结果表明,Ce0.8Sm0.2O1.9的掺入不但有效地降低了La0.7Sr0.3Co0.95Cu0.05O3-δ阴极材料的热膨胀系数,而且Ce0.8Sm0.2O1.9掺入量为10%(质量分数,下同)的样品,其电导率高于La0.7Sr0.3Co0.95Cu0.05O3-δ,并且它在相同过电位下其阴极电流密度也大于其他样品.以其为阴极的SOFC单电池,在850 ℃最大短路电流密度达511 mA/cm2,最大输出功率密度为106 mW/cm2.     

La0.7Sr0.3Cu1-xFexO3-δ系阴极材料的制备与性能研究

采用固相法和EDTA-柠檬酸联合络合法制备了中温固体氧化物燃料电池La0.7Sr0.3Cu1-xFexO3-δ阴极材料,利用直流四探针和交流阻抗技术测试了材料的导电性能和电化学性能,结果表明加入Fe后材料的电导率有所降低,但在高温下仍然具有较高的电导率(＞100 S·cm-1).EDTA-柠檬酸联合络合法制备的试样比固相法合成的具有更高的电导率(在800℃时,EDTA-柠檬酸联合络合法制备的试样电导率为255 S·cm-1,而固相法的为156 S·cm-1).700℃时的复阻抗测试结果表明Fe的加入降低了La0.7Sr0.3CuO3-δ的极化电阻,其中La0.7Sr0.3Cu0.4Fe0.6O3-δ的极化电阻最小,为2.51 Ω·cm2.     

GDC电解质粉体合成及其性能

采用甘氨酸-硝酸盐法合成了均一、单相、烧结活性高的GDC(Ce0.8Gd0.2O1.9)电解质粉体.利用交流阻抗谱法测定了350℃～700℃范围内GDC烧结体离子电导率.通过多层流延制备了GDC/YSZ/NiO-YSZ(8 mol%yttria-stabilized zirconia)3层复合生坯,共烧后在GDC面丝网印刷LSCF(La0.8Sr0 2Fe0.8Co0.2O3)阴极浆料,烧结得到了表面平整、无开裂的LSCF/GDC/YSZ/NiO-YSZ 4层PEN(Positive-Electrolyte-Negative)结构.     

流延-共烧法制备掺杂氧化铈基阳极／电解质双层结构

采用甘氨酸／硝酸盐（GNP）法合成了具有较高烧结活性的Ce0.8Gd0.05Y0.15O1.9（GYDC）粉体，通过流延-共烧法制备了NiO—GYDC阳极／GYDC电解质双层结构。结果表明：GYDC电解质薄膜经过1400℃保温4h后可烧结致密，说明GNP法制备的GYDC粉体的烧结活性较高；通过流延．共烧法可以成功制备外观完好、平整的NiO-GYDC／GYDC双层结构，满足SOFC的组装要求。     

燃烧法制备中温SOFC电解质及其电极材料

采用一种新的燃烧合成陶瓷粉体的方法--硝酸盐-柠檬酸盐燃烧法低温合成中温SOFC所有元件的初始粉体并组装成单电池,电池的电解质材料为Ce0.8Gd0.2O1.9,阴极材料为掺杂一定量固体电解质的La0.6Sr0.4Fe0.8Co0.2O3,阳极材料为固体电解质与NiO的复合材料.单电池的性能测试结果表明:单电池的输出电压和输出电流皆随其运行温度升高而增大,同时单电池的开路电压随温度升高而下降.以Ce0.8Gd0.2O1.9电解质材料为电解质的单电池在750℃的最大输出功率密度约为85 mW/cm2.     

NiO-YSZ/YSZ复合梯度材料制备工艺与性能

探索了以NiO和YSZ微粉为原料,采用干压成型的方法制备NiO-YSZ/YSZ复合材料的工艺过程.实验结果表明随着NiO含量的减少,实验样品收缩率和相对密度均逐渐增加;当NiO含量从46%(体积分数,下同)降为30%时,1400℃,1 h下得到的样品收缩率由17.6%逐渐增至21.8%,相对密度由64.04%增至75.93%;1450℃,2 h下得到的样品收缩率则由21.2%逐渐增至23.3%,相对密度也由66.9%增至74.2%.选用1400℃,1 h的烧结工艺能得到晶粒大小均匀,晶粒尺寸较小的复合材料.各复合层的收缩率差值在1%以上,即可造成不同程度的翘曲.要以干压成型制备NiO-YSZ/YSZ复合梯度材料,3层复合是远远不够的.复合梯度材料较好地改善电极与电解质间的界面接触状态,为其在燃料电池上的应用奠定了基础.     

流延-共烧法制备掺杂氧化铈基阳极/电解质双层结构

采用甘氨酸/硝酸盐(GNP)法合成了具有较高烧结活性的Ce0.8Gd0.05Y0.15O1.9(GYDC)粉体,通过流延-共烧法制备了NiO-GYDC阳极/GYDC电解质双层结构.结果表明:GYDC电解质薄膜经过1400 ℃保温4 h后可烧结致密,说明GNP法制备的GYDC粉体的烧结活性较高;通过流延-共烧法可以成功制备外观完好、平整的NiO-GYDC/GYDC双层结构,满足SOFC的组装要求.     

Ni-GDC阳极的制备及其孔隙率研究

采用缓冲溶液法制备出NiO—GDC复合粉末，该粉末压制、烧结后再经氰气气氛还原得到Ni—GDC金属陶瓷阳极。使用XRD，TEM，SEM对NiO—GDC和Ni—GDC的物相、形貌进行了观察分析，测定了阳极还原前后的相对密度、总孔隙率及开孔隙率。实验结果表明，由于NiO转变为Ni，有O的火上，使得还原后试样的相对密度明显下降，而孔隙率由15．4％提高到29．6％，且开孔隙率达到23．1％，可满足阳极作为燃料扩散通道的作用。多孔结构的Ni—GDC金属陶瓷阳檄有望成为中混固体氧化物燃料电池的阳极材料。     

Fabrication and electrochemical performance of solid oxide fuel cell components by atmospheric and suspension plasma spray

The theory of functionally graded material (FGM) was applied in the fabrication process of PEN (Positive-Electrolyte-Negative), the core component of solid oxide fuel cell (SOFC). To enhance its electrochemical performance, the functionally graded PEN of planar SOFC was prepared by atmospheric plasma spray (APS). The cross-sectional SEM micrograph and element energy spectrum of the resultant PEN were analyzed. Its interface resistance was also compared with that without the graded layers to investigate the electrochemical performance enhanced by the functionally graded layers. Moreover, a new process, suspension plasma spray (SPS) was applied to preparing the SOFC electrolyte. Higher densification of the coating by SPS, 1.61%, is observed, which is helpful to effectively improve its electrical conductivity. The grain size of the electrolyte coating fabricated by SPS is also smaller than that by APS, which is more favourable to obtain the dense electrolyte coatings. To sum up, all mentioned above can prove that the hybrid process of APS and SPS could be a better approach to fabricate the PEN of SOFC stacks, in which APS is for porous electrodes and SPS for dense electrolyte.     

Microstructure and polarization resistance of thermally sprayed composite cathodes for solid oxide fuel cell use

Porous composite cathode coatings containing (La_0.8 Sr_0.2)_0.98MnO₃ (LSM) and ZrO₂-12% Y₂O₃ (YSZ) were prepared by vacuum plasma spraying (VPS) and flame spraying (FS) on prefabricated substrate-based planar solid oxide fuel cells (SOFC) with 60 mm in diameter. Microstructural observations reveal the open porosity of the cathode coatings and prove qualitatively the compositional gradient from YSZ-LSM composite to pure LSM. The electrochemical behavior was investigated by impedance spectroscopy. The results of graded cathodes compared with nongradient and bilayered ones are discussed with respect to the cathodic polarization resistance between 750 and 950°C. Bilayered cathodes indicate the lowest cathodic losses followed by the graded ones and the conventional composite. Flame spraying as a rarely used processing tool for SOFC components can provide cathodes of high electrochemical performance.     

Fabrication and performance of La0.8Sr0.2MnO3/YSZ graded composite cathodes for SOFC

The performance of multi-layer (1-x)La0.8Sr0.2MnO3/xYSZ graded composite cathodes was studied as electrode materials for intermediate solid oxide fuel cells (SOFC). The thermal expansion coefficient, electrical conductivity, and electrochemical performance of multi-layer composite cathodes were investigated. The thermal expansion coefficient and electrical conductivity decreased with the increase in YSZ content. The (1-x)La0.8Sr0.2MnO3/xYSZ composite cathode greatly increased the length of the active triple phase boundary line (TPBL) among electrode, electrolyte, and gas phase, leading to a decrease in polarization resistance and an increase in polarization current density. The polarization current density of the triple-layer graded composite cathode (0.77 A/cm2) was the highest and that of the monolayer cathode (0.13 A/cm2) was the lowest. The polarization resistance (Rp) of the triple-layer graded composite cathode was only 0.182Ω·cm2 and that of the monolayer composite cathode was 0.323Ω·cm2. The power density of the triple-layer graded composite cathode was the highest and that of the monolayer composite cathode was the lowest. The triple-layer graded composite cathode had superior performance.     

Compressive mica seals for solid oxide fuel cells

Sealing technology is currently considered a top-priority task for planar solid oxide fuel-cell stack development. Compressive mica seals are among the major candidates for sealing materials due to their thermal, chemical, and electrical properties. In this paper, a comprehensive study of mica seals is presented. Two natural micas, muscovite and phlogopite, were investigated in either a monolithic single-crystal sheet form or a paper form composed of discrete mica flakes. A “hybrid” mica seal, developed after identification of the major leak paths in compressive mica seals, demonstrated leak rates that were hundreds to thousands times lower than leak rates for conventional mica seals. The hybrid mica seals were further modified by infiltration with wetting materials; these “infiltrated” micas showed excellent thermal cycle stability with very low leak rates (10⁻³ sccm/cm). The micas were also subjected to studies to evaluate thermal stability in a reducing environment as well as the effect of compressive stresses on leak rates. In addition, long-term open circuit voltage measurements versus thermal cycling showed constant voltages over 1,000 cycles. The comprehensive study clearly demonstrated the potential of compressive mica seals as sealing candidates for solid oxide fuel cells. This paper was presented at the ASM Materials Solutions Conference & Show held October 18–21, 2004 in Columbus, OH.     

Designing sealing glasses for solid oxide fuel cells

Thermal and chemical properties of “invert” glasses and glass-ceramics developed for hermetic seals for solid oxide fuel cells are described. The glasses crystallize to form thermally stable pyro- and orthosilicate phases with the requisite thermal expansion match to the Y-stabilized ZrO₂ (YSZ) electrolyte. In addition, the glasses bond to Cr-steel substrates at 800–850 °C without forming extensive interfacial reaction products. The thermal expansion characteristics of the glass-ceramics remain essentially unchanged after 28 days at 750 °C. Compositions with lower (≤2 mol%) B₂O₃ contents exhibit the lowest volatilization rates when exposed to wet forming gas at 750 °C. This paper was presented at the ASM Materials Solutions Conference & Show held October 18–21, 2004 in Columbus, OH.     

SmBaCoCuO5+x as cathode material based on GDC electrolyte for intermediate-temperature solid oxide fuel cells

The performance of SmBaCoCuO_5+x (SBCCO) cathode has been investigated for their potential utilization in intermediate-temperature solid oxide fuel cells (IT-SOFCs). The powder X-ray diffraction (XRD), thermal expansion and electrochemical performance on Ce_0.9Gd_0.1O_1.95 (GDC) electrolyte are evaluated. XRD results show that there is no chemical reaction between SBCCO cathode and GDC electrolyte when the temperature is below 950 °C. The thermal expansion coefficient (TEC) value of SBCCO is 15.53 × 10⁻⁶ K⁻¹, which is ∼23% lower than the TEC of the SmBaCo₂O_5+x (SBCO) sample. The electrochemical impedance spectra reveals that SBCCO symmetrical half-cells by sintering at 950 °C has the best electrochemical performance and the area specific resistance (ASR) of SBCCO cathode is as low as 0.086 Ω cm² at 800 °C. An electrolyte-supported fuel cell generates good performance with the maximum power density of 517 mW cm⁻² at 800 °C in H₂. Preliminary results indicate that SBCCO is promising as a cathode for IT-SOFCs.     

New sealing concept for planar solid oxide fuel cells

A key element in developing high-performance planar solid oxide fuel-cell stacks is the hermetic seal between the metal and ceramic components. Two methods of sealing are commonly used: (a) rigid joining and (b) compressive sealing. Each method has its own set of advantages and design constraints. An alternative approach is currently under development that appears to combine some of the advantages of the other two techniques, including hermeticity, mechanical integrity, and minimization of interfacial stresses in the joint substrate materials, particularly the ceramic cell. The new sealing concept relies on a plastically deformable metal seal; one that offers a quasi-dynamic mechanical response in that it is adherent to both sealing surfaces, i.e., non-sliding, but readily yields or deforms under thermally generated stresses. In this way, it mitigates the development of stresses in the adjacent ceramic and metal components even when a significant difference in thermal expansion exists between the two materials. The pre-experimental design of the seal, initial proof-of-principle results on small test specimens, and finite-element analyses aimed at scaling the seal to prototypical sizes and geometries are described herein. This paper was presented at the ASM Materials Solutions Conference & Show held October 18–21, 2004 in Columbus, OH.     

一步双修饰策略提高富镍层状氧化物正极材料的电化学性能（英文）

提出一种从表面到体相的一步整体改性策略,同步合成Nb掺杂和LiNbO₃包覆的LiNi_0.83Co_0.12Mn_0.05O₂(NCM)正极材料。LiNbO₃包覆层可以调控界面并促进锂离子扩散;更强的Nb—O键能有效抑制Li⁺/Ni²⁺阳离子混排,提高晶体结构稳定性,从而有助于缓解Li⁺脱出/嵌入过程中晶格参数的各向异性变化。结果表明:双修饰材料表现出较好的结构稳定性和优异的电化学性能。最佳样品NCM-Nb2在2.7～4.3 V之间以1C循环100次后,容量保持率为90.78%,而原始样品容量保持率仅为67.90%;同时,在10C下具有149.1 mA·h/g的更高倍率性能,这些结果突显了一步双修饰策略协同提高富镍层状氧化物正极材料电化学性能的可行性。     

Development of thermal spraying-sintering technology for solid oxide fuel cells

A thermal spraying-sintering process has been developed for an electrolyte and interconnect layer, which results in improved gas tightness, a thinner layer, and higher electric conductivity as required for solid oxide fuel cells (SOFCs). The process is characterized by the heat treatment of composition-controlled plasma-sprayed layers. For the electrolyte, the addition of MnO₂ to zirconia powder is effective for reducing the sintering temperature to obtain gas tightness and for suppressing the reaction between zirconia and air electrode material. An electrolyte layer of 60 μm thickness with sufficient gas tightness and high ionic conductivity was obtained by this process. For the interconnect, chromium-rich lanthanum chromite powder, La_0.8Ca_0.2Cr_1.10O₃, is optimum for both gas tightness and high electric conductivity of the layer. In addition, a single cell with a 60 μm electrolyte was successfully fabricated using the thermal spraying-sintering process. As a result of an operating test using O₂ and humidified H₂ at 1000°C, a power density of 0.73 W/cm² was obtained. It was demonstrated that the thermal spraying-sintering technology is effective for the fabrication of a thin gas tight layer for SOFCs.