P-Type Electronic Transport in Ce0.8Gd0.2O2 − δ: The Effect of Transition Metal Oxide Sintering Aids

Small (2 mol%) additions of cobalt, iron and copper oxides into Ce_0.8Gd_0.2O_{2 –} considerably improve sinterability of ceria-gadolinia (CGO) solid electrolyte, making it possible to obtain ceramics with 95–99% density and sub-micron grain sizes at 1170–1370 K. The minor dopant additions have no essential effect on the total and ionic conductivity, whilst the p-type conduction in the transition metal-containing materials at 900–1200 K is 8–30 times higher than that in pure CGO. The oxygen ion transference numbers of the Co-, Fe- and Cu-doped ceramics, determined by the modified e.m.f. technique under oxygen/air gradient, are in the range 0.89–0.99. The electron-hole contribution to the total conductivity increases with temperature, as the activation energy for ionic conduction, 78 to 82 kJ/mol, is significantly lower than that for the p-type electronic transport (139–146 kJ/mol). The results show that CGO sintered with such additions can still be used as solid electrolytes for intermediate-temperature electrochemical applications, including solid oxide fuel cells (SOFCs) operating at 770–970 K, but that increasing operation temperature is undesirable due to performance loss.     

EIS测定Ce0.8Gd0.2O1.9电导率的等效电路分析

测量了采用柠檬酸-硝酸盐燃烧合成制备的固体氧化物燃料电池电解质Ce0.8Gd0.2O1.9(CGO)的电化学阻抗谱(EIS),结果表明,阻抗谱与测试温度有关。提出了阻抗谱的等效电路,并对不同测试温度下CGO的阻抗谱进行了分析。CGO的电导率ln(бT)与1/T近似呈线性关系。800℃时CGO电解质的氧离子电导率为0.044S·m-1。     

电解Co0.2Ni0.8合金制备LiCo0.2Ni0.8O2的研究

利用电解钻镍合金制得Co0 2Ni0.8(OH)2中间产物,然后根据钻镍含量与LiOH·H2O固相反应制得了LiCo0.2Ni0.8O2.通过X光衍射和扫描电镜测试表明,所得的锂离子正极材料LiCo0.2Ni0.8O2结构纯正,粒度分布集中;对其进行充放电实验表明,放电容量比较高,首次放电容量达到156mAh/g,循环20次后容量仍保持在146mAh/g.该法可大大降低制备锂离子正极材料的生产成本,具有十分广阔的应用前景.     

固体氧化物燃料电池Ce0.8Mo0.2O2+δ阴极阻挡层研究

采用Pechini方法分别合成Ce0.8Mo0.2O2+δ(CMO)和Ce0.8Gd0.2O2-δ(CGO)两种阴极阻挡层粉体,并通过X射线衍射光谱法(XRD)等手段对粉体进行表征,结果表明CMO粉体主晶相呈萤石型结构,粉体中还含有Ce8Mo12O49杂质.将CMO和CGO分别应用于3％(摩尔分数)Y2O3稳定氧化锆(3YSZ)电解质支撑单电池的阴极阻挡层,进行了单电池的电化学性能测试,基于CMO阻挡层单电池的性能远低于基于CGO阻挡层单电池的性能,电化学阻抗谱表明电池呈现高的欧姆阻抗.显微结构分析发现,3YSZ/CGO之间的元素扩散仅在界面发生,而3YSZ/CMO之间的元素扩散主要是Mo扩散至3YSZ层形成固溶体,CMO和CGO未能有效阻挡Sr的扩散.     

Measurement of electrical conductivity of La0.2Sr0.8Cr0.2Fe0.8O3-�� using gas-tight electrochemical cells

The oxygen partial pressure (pO₂) dependence of the electrical conductivity of La_0.2Sr_0.8Cr_0.2Fe_0.8O_3-?? (LSCrF) was obtained at T?=?750?C1060°C and pO₂?=?10^?18?0.5 atm. The slope of the plot of log ?? vs. log pO₂ is ??1/5 in the p?Ctype region, pO₂?=?10^?5?10^?1 atm. The p-n transition pO₂ increases with increasing temperature. The activation energy for ionic conduction was estimated to be 0.86 eV from an Arrhenius plot of the minimum conductivity vs. reciprocal temperature. At temperatures below 942°C, a plateau in the conductivity isotherm suggests the presence of a two-phase region. Most likely, phase separation occurs to form a mixture of a perovskite phase and an oxygen vacancy ordered phase related to brownmillerite.     

LiNi0.8Co0.2O2的制备及性能研究

用共沉淀法合成了球形Ni0.8Co0.2(OH)2,然后将其与LiOH·H2O混合后在不同高温合成条件下制得LiNi0.8Co0.2O2。系统地研究了保温时间、Li/(Ni Co)配比、焙烧温度对合成的Li-Ni0.8Co0.2O2材料的电化学性能的影响。电化学充放电循环测试结果表明:在优化条件下制得的LiNi0.8Co0.2O2材料表现出优良的电化学性能,其首次充电容量达到219.3mAh/g,首次放电容量达到195.4mAh/g,首次充放电效率89.1%,循环20次后放电容量仍能保持在185mAh/g。     

LiNi0.8Co0.2O2表面包覆MgO及其性能

锂离子蓄电池正极材料和电解液之间的恶性相互作用是引起正极材料和电池性能劣化的重要原因。用沉淀法在Ni0,8Co0.2(OH)2前驱体表面包覆一层Mg(OH)2,再与LiOH共混热处理,制备出表面包覆MgO的LiNi0.8Co0.2O2。用X光电子能谱、扫描电镜和X射线衍射分析对包覆前后的Ni0.8Co0.2O2与LiNi0.8Co0.2O2的结构进行了表征。充放电测试结果表明,经表面修饰处理后,LiNi0.8Co0.2O2正极材料的初始放电比容量略有降低,但循环稳定性显著改善。研究结果表明,表面修饰处理可以有效地抑制正极材料与电解液之间的恶性相互作用,是改善锂离子蓄电池正极材料循环性能的有效途径。     

LiNi0.8Co0.2O2的合成和电化学性能研究

在氧气气氛下,以乙酸盐为原料,以柠檬酸为螯合剂,用溶胶凝胶法制备出了锂离子电池正极材料LiNi0.8Co0.2O2。研究了不同合成温度和Li/(Ni Co)配比对材料的结构和电化学性能的影响。XRD检测结果表明:合成温度为750℃、合成时间为18h、Li/(Ni Co)=1.10的正极材料LiNi0.8Co0.2O2具有完整的晶型结构;充放电性能测试结果表明,该材料在0.5C下,首次充放电容量分别为230.0m Ah/g和192.6m Ah/g,首次充放电效率为83.73%,经过50次循环仍有170.5m Ah g/,容量保持率为90.87%。     

锂离子电池正极材料LiNi0.8 Co0.2 O2的研究进展

综述了LiNi0.8co0.2O2的研究进展.对固相法、共沉淀法、溶胶.凝胶法、络合法、电解法和共熔直接混合法等制备方法进行了介绍;对高温稳定性、循环稳定性和首次充放电容量等电化学性能的改善进行了总结.     

锂离子蓄电池用正极LiNi0.8Co0.2O2的研究

总结了聚合物锂离子蓄电池正极材料的研究现状,通过研究提出了一种新型正极改性材料LiNi0.8Co0.2O2的制备工艺,该材料在聚合物锂离子蓄电池中的应用研究表明,LiNi0.8Co0.2O2改善了材料的放电性能并降低了电池成本。本研究将凝胶-溶胶法和喷雾干燥法相结合,采用高分子化合物RB-1(由多元有机酸和高分子聚合物例如明胶和淀粉等组成)来调整溶胶体,结合煅烧过程中对温度和时间的控制,研究出溶胶-喷雾干燥-煅烧的制备工艺。实验以差热分析-热重分析(DTA-TGA)法来分析喷雾干燥的过程和作用,以X射线衍射(XRD)分析材料的结构,以容量测试来分析材料的放电性能。所得LiNi0.8Co0.2O2具有优良的层状结构,应用于聚合物锂离子蓄电池中,可使电池的可逆比容量达到180mAh/g,并保持良好的稳定性和循环寿命。     

水热电化学法制备LiCo0.2Ni0.8O2薄膜电极

采用水热电化学法在金属Ni基体上一步合成LiCo0.2Ni0.8O2薄膜电极.ICP-AES、IR、XRD、SEM、CV等测试表明:薄膜电极LiCo0.2Ni0.8O2晶体为R3m型结构;薄膜由大小均匀、直径约为1 μm的晶粒组成.通过水热电化学法制备的Li-Co0.2Ni0.8O2薄膜电极具有良好的电性能.     

控制结晶法制备高容量LiNi0.8Co0.2O2正极材料

采用控制结晶法制备高活性和高堆积密度锂离子蓄电池正极材料LiNi0.8Co0.2O2,并研究了控制结晶工艺对前驱体Ni0.8Co0.2(OH)2物理性能和LiNi0.8Co0.2O2电化学性能的影响。实验表明,当pH值为10.5,搅拌速度为600r/min,采用浆上进料时合成LiNi0.8Co0.2O2的首次放电容量达到187mAh/g,循环50次后能保持初始容量的94.1%。     

改进埋烧法制备La0.8Sr0.2Ga0.8Mg0.2O3电解质及其性能

采用改进埋烧法制备出高致密度和优异中温离子导电性能的La0.8Sr0.2Ga0.8Mg0.2O3(LSGM)固体电解质。用X射线衍射、扫描电镜分析样品的物相和表面形貌,采用阿基米德排水法进行试样的密度测试,用交流阻抗技术研究样品的电性能。研究结果表明:在1 400 ℃以上烧结形成单一稳定的钙钛矿结构。随着烧结温度的提高和保温时间的延长,样品致密度增大,导电性能提高,在1 470 ℃烧结18 h的样品均达到最佳值,其相对密度为98%,在800 ℃时电导率达到0.11 S·cm-1。该体系电导率与温度的关系分区符合Arrhenius定律。     

用溶胶凝胶法在LiNi0.8Co0.2O2表面包覆SiO2

锂离子蓄电池正极材料和电解液之间的恶性相互作用是引起正极材料和电池性能劣化的重要原因。以正硅酸乙酯为原料 ,采用溶胶凝胶法在LiNi0 .8Co0 .2 O2 表面包覆上一层稳定的SiO2 层。用X光电子能谱、扫描电镜和X光衍射分析等手段对包覆前后LiNi0 .8Co0 .2 O2 的结构进行了表征。研究表明 ,SiO2 包覆层的存在减少了LiNi0 .8Co0 .2 O2 和电解液的直接接触 ,有效地抑制了高温下LiNi0 .8Co0 .2 O2 与电解液的恶性相互作用。经表面修饰处理后 ,LiNi0 .8Co0 .2 O2 正极材料在高温下 ( 6 0℃ )的实际比容量显著提高 ,充放电循环稳定性显著改善 ,制成的电池自放电速率显著减小。本文的研究结果表明 ,表面修饰处理是改善锂离子蓄电池正极材料高温性能的有效途径。     

Electrical Conduction and Disorder in the Pyrochlore System (Gd1−xCax)2Sn2O7

Electrical conductivity measurements were made on the pyrochlore compounds (Gd₁–_xCa_x)₂Sn₂O₇ (x =0, 0.0036, 0.0057, 0.03) as a function of temperature, oxygen partial pressure and Ca doping concentration. An effective Frenkel constant and oxygen vacancy mobility were derived. Intrinsic anion disorder was found to be lower than the expected value based on the relative radii of the cations in the A and B sites (A₂B₂O₇). Low oxygen vacancy mobilities as well as low anion disorder resulted in considerably lower ionic conductivities in Gd_sSn₂O₇ relative to the previously studied Gd₂(Ti₁–_xZr_x)₂O₇ system. The temperature and composition dependence of the p-type electronic conductivity were evaluated and the oxidation enthalpy was derived.     

Synthesis and electrochemical properties of LiNi1−y Zn y O2

Zn doped LiNi_1?y Zn _y O₂ (0.00?≤?y?≤?0.100) composition was synthesized by an emulsion method. The emulsion-derived powder was calcined at the temperature range of 650?～?800 °C for 12?～?48 h. A single phase of LiNi_1?y Zn _y O₂ was obtained at 700 °C. The optimum condition for the synthesis of LiNi_1?y Zn _y O₂ was to be calcined at 750 °C for 36 h in oxygen stream. The composition of LiNi_0.995Zn_0.005O₂ showed the largest discharge capacity and improved cycle life. The initial and final discharge capacities were 163 and 154.5 mAh/g, respectively. The fading rate in discharge capacity after 20 cycles was only 5.2%.     

锰掺杂LiNi0.8Co0.2O2的合成及电极性能研究

为了获得高性能锂离子电池的正极材料,采用共沉淀法,对LiNi0.8Co0.2O2进行Mn元素的掺杂改性,考察了不同Mn掺杂量对LiNi0.8Co0.2O2材料的结构和其电化学性能的影响,并对材料进行X射线衍射、扫描电镜、循环伏安分析和恒流充放电测试。实验表明,锰掺杂改善了LiNi0。8Co0.2O2材料循环性能,LiNi0.78Nn0.02Co0.2O2的首次放电比容量达到180.8mA·h/g,50循环后放电比容量还能保持在169.8mA·h/g,50循环比容量保持率达到94%。     

Electrical Conduction and Magnetoelectric Effect in CuFe1.8Cr0.2O4–Ba0.8Pb0.2TiO3 Composites

Magnetoelectric composites of CuFe_1.8Cr_0.2O₄– Ba_0.8Pb_0.2TiO₃ were prepared using high temperature solid-state reaction technique. X-ray structural analysis of these composites confirms the presence of both the phases in the composite. Detailed studies of dielectric properties (, tan and _ac ) as a function of frequency (100 Hz to 1 MHz) and temperature (30°C to 250°C) show that these compounds exhibit diffuse ferroelectric phase transitions. Results of ac conductivity, dc resistivity and thermoelectric power measurements show that conduction occurs by hopping of charge carriers. The magnetoelectric effect has been studied as a function of intensity of magnetic field. The electrical polarisation was induced in piezoelectric (Ba_0.8Pb_0.2TiO₃) phase as result of strain induced in the ferrite (CuFe_1.8Cr_0.2O₄) phase by the applied magnetic field. The Jahn-Teller distortion caused in the ferrite lattice by Jahn-Teller ions like Cu²⁺ and Cr³⁺ is also responsible for the elastic coupling of strain to the Ba_0.8Pb_0.2TiO₃ phase.     

新型低温SOFC阴极材料LaNi0.8Cu0.2O3

采用碳酸共沉淀法得到了一种新型阴极材料LaNi0.8Cu0.2O3(LNC-82),对其进行了X射线衍射和扫描电镜的表征,并采用复合材料[Ce0.8Sm0.2O2-δ(SDC)和碳酸盐(Na2CO3 Li2CO3)]为电解质,分别以NiO和LNC-82为阳极和阴极材料,考察了在低温(400～550℃)下这种钙钛矿型阴极材料的电化学性能。实验结果表明,运用碳酸共沉淀法得到了LNC-82前驱体粉末,经过860℃煅烧2h,得到了粒度均匀的粉末,其粒径约为400～500nm。单体电池在550℃下的最大比功率和短路电流分别为390.6mW/cm2和1140.6mA/cm2。     

Effects of doping Y2O3 on the microstructure and electrical properties of ZnO-Bi2O3−based varistor ceramics

ZnO-based varistor ceramics doped with different amount of Y₂O₃ have been made by two-step solid-state reaction route including the pre-calcination and subsequent sintering procedures, using nanosized ZnO powder and corresponding additives as the raw material. The phase composition, microstructure and electrical properties were studied by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) and direct current electrical measurement. It was found that the electrical properties of the varistor ceramics sintered at 950 °C from the powder pre-calcined at 800 °C were enhanced by doped appropriate amount of Y₂O_3. Particularly, ZnO varistors doped with 1.2 mol% Y₂O₃ possessed the best comprehensive electrical properties with the breakdown field of 2113 V/mm, the nonlinear coefficient of 184.6 and the leakage current of 0.4 μA. Y₂O₃ phase, Y-rich phase and the other secondary phase particles were confirmed to distribute along the grain boundaries of predominant ZnO grains from XRD and SEM analyses. The results illustrated that doping Y₂O₃ should be a promising route to obtain varistor ceramics with excellent electrical properties.