高温锂电池氧化物正极材料研究现状与展望

高温锂电池是热电池向中低温度范围的拓展和延伸,在石油、天然气及地热探测等领域有很好的应用前景。相对于具有大比容量和接近纯锂电极电位的锂合金负极材料,正极材料还有不小的发展潜力。因此,正极材料是提升高温锂电池性能的关键材料。而在正极材料中,氧化物材料表现出高电压特性以及高热稳定性,可以推动高温锂电池小型化发展,满足特定条件下的电流电压供给。目前,并没有针对高温锂电池氧化物正极材料的系统性综述。为了促进本领域的快速发展,优化能源结构,本文系统总结了高温锂电池过渡族金属氧化物正极材料的研究进展,包括其物理特性、电化学特性及合成与制备方法,对材料的可利用特性以及不足之处加以说明;进而对氧化物正极材料在高温锂电池领域的应用做出展望。     

GINZBURG-LANDAU THEORY AND VORTEX LATTICE OF HIGH-TEMPERATURE SUPERCONDUCTORS

The thermodynamics of the vortex lattice of high-temperature superconductors has been studied by solving the generalized Ginzburg-Landau equations derived microscopically. Our numerical simulation indicates that the structure of the vortex lattice is oblique at the temperature far away from the transition temperature T_c, where the mixed s-d_x²-y² state is expected to have the lowest energy. Whereas, very close to T_c, the d_x²-y² wave is slightly lower energetically, and a triangular vortex lattice recovers. The coexistence and the coupling between the s and d waves would account for the unusual dynamic behaviours such as the upward curvature of the upper critical field curve H_C2(T), as observed in dc magnetization measurements on single-crystal YBa₂Cu₃O₇ samples.     

High-temperature combustion synthesis and electrochemical characterization of LiNiO2, LiCoO2 and LiMn2O4 for lithium-ion secondary batteries

Lithium nickelate (Li_0.88Ni_1.12O₂), lithium cobaltate (LiCoO₂) and lithium manganate (LiMn₂O₄) were synthesized by fast self-propagating high-temperature combustion and their phase purity and composition were characterized by X-ray diffraction and inductively coupled plasma spectroscopy. The electrochemical behaviour of these oxides was investigated with regard to potential use as cathode materials in lithium-ion secondary batteries. The cyclic voltammograms of these cathode materials recorded in 1 M LiClO₄ in propylene carbonate at scan rates of 0.1 and 0.01 mV s^–1 showed a single set of redox peaks. Charge-discharge capacities of these materials were calculated from the cyclic voltammograms at different scan rates. The highest discharge capacity was observed in the case of Li_0.88Ni_1.12O₂. In all the cases, at a very slow scan rate (0.01 mV s^–1) the capacity of the charging (oxidation) process was higher than the discharging (reduction) process. A strong influence of current density on the charge-discharge capacity was observed during galvanostatic cycling of Li_0.88Ni_1.12O₂ and LiMn₂O₄ cathode materials. LiMn₂O₄ can be used as cathode material even at higher current densities (1.0 mA cm^–2), whereas in the case of Li_0.88Ni_1.12O₂ a useful capacity was found only at lower current density (0.2 mA cm^–2). For the fast estimation of the cycling behaviour of LiMn₂O₄, a screening method was used employing a simple technique for immobilizing microparticles on an electrode surface. Electronic Publication     

Effect of substrate materials on the superconducting properties of electrophoretically deposited YBa2Cu3O7−x coatings

Coatings of the high-temperature superconductor YBa₂Cu₃O_7–x (x = 0.1–0.2) (YBCO), were deposited on commercial Ni,Ti and stainless steel substrates, by an electrophoretic deposition technique. Sintering and annealing procedures were followed in order to get strongly adherent superconducting films. The suitability of the used substrates was tested by measuring the stoichiometry and the superconducting properties of the deposited coatings by X-ray diffraction analysis (XRD), Raman spectroscopy and magnetization measurements with a superconducting quantum interference device (SQUID).     

Regularities of self-propagating high-temperature synthesis in the solid 8-hydroxyquinoline—chloramine B system

The regularities of chemical reactions in solid 8-hydroxyquinoline—chloramine B mixtures were studied under conditions of organic self-propagating high-temperature synthesis (SHS), isothermal reaction, and thermal explosion in the 20–220 °C temperature range. Comprehensive physicochemical analysis and microstructural study of the reaction products were carried out. The temperature of SHS initiation (58 °C), the heat of the reaction (129±9 kJ mol⁻¹), the stoichiometric coefficient (1), the maximum temperature (T _max=98–140 °C), and the velocity of SHS wave propagation (u=0.15–0.55 mm s⁻¹) were determined. Depending on the ratio of the reactants (n), a low-temperature non-degeerate stable gasless mode (n≤1,T _max=115 °C,E _a=42 kcal mol⁻¹) and a high-temperature mode (n>1,T _max=140 °C,E _a=0.4 kcal mol⁻¹) are possible for SHS. The SHS affords monohydroxy and monochloro derivatives of 8-hydroxyquinoline, benzenesulfonamide, NaCl, NaOH, and H₂O. The mechanism of the solid-phase reaction at temperatures below 58 °C includes surface, solid-phase, and gas-phase diffusion; that for SHS is capillary spreading of the hydroxyquinoline melt. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2271–2284, December, 1999.     

Ti6Al4V合金表面激光熔覆复合涂层的高温摩擦学性能研究

为了改善Ti6Al4V合金的摩擦学性能,采用预置NiCrBSiFe复合粉末激光熔覆制备高温耐磨复合涂层,分析了涂层的显微组织,测试了其显微硬度、室温(25℃)及高温(600℃)磨损性能,并分析了其机理.结果表明:复合涂层与钛合金基体为冶金结合,以γ-(Ni,Cr,Fe)固溶体为基体,原位生成的TiC、TiB_2和CrB增强相均匀分布于涂层中,涂层的平均硬度为HV0.5950,约为钛合金基体(HV0.5360)的3倍.室温下,由于涂层具有很高硬度,改善了钛合金表面严重的黏着磨损,涂层表现出优异的耐磨性;高温下,钛合金表面生成氧化膜表现出固体润滑效果,摩擦系数和磨损量均下降,而涂层中基体相硬度下降,磨损表面出现犁沟和破碎磨粒,摩擦系数和磨损率相比室温略有上升,但相比钛合金仍表现出较好的高温耐磨性.     

稀释剂对耐高温环氧树脂性能的影响

采用3,4-环氧环己基甲基-3,4-环氧环己基甲酸酯(2010P)作为N,N,N',N'-四环氧丙基-4,4'-二氨基二苯甲烷环氧树脂(AG-80)/六氢苯酐(HHPA)固化体系的稀释剂。 通过粘度、拉伸、高温剪切、示差扫描量热法(DSC)以及高倍显微镜等技术手段及方法,考察稀释剂含量对环氧树脂的粘度、力学性能和热性能的影响,研究了稀释剂与环氧树脂之间的相互作用。 结果表明,2010P可以显著提高树脂的流动性。 随着2010P含量的增加,体系的拉伸强度会呈现先上升后下降的趋势,在质量分数25%时达到最大值。 DSC结果显示,2010P的加入会降低AG-80的玻璃化转变温度,但适量的加入可以进一步提高AG-80环氧树脂在高温条件下的粘接性能。 当2010P的质量分数为30%时,树脂在200 ℃的剪切强度可达到13.78 MPa。     

Structural characterization of Al_(0.55)Ga_(0.45)N epitaxial layer determined by high resolution x-ray diffraction and transmission electron microscopy

Structural characteristics of Alo.55 Gao.45N epilayer were investigated by high resolution x-ray diffraction(HRXRD)and transmission electron microscopy(TEM);the epilayer was grown on GaN/sapphire substrates using a high-temperature A1 N interlayer by metal organic chemical vapor deposition technique.The mosaic characteristics including tilt,twist,heterogeneous strain,and correlation lengths were extracted by symmetric and asymmetric XRD rocking curves as well as reciprocal space map(RSM).According to Williamson-Hall plots,the vertical coherence length of AlGaN epilayer was calculated,which is consistent with the thickness of AlGaN layer measured by cross section TEM.Besides,the lateral coherence length was determined from RSM as well.Deducing from the tilt and twist results,the screw-type and edge-type dislocation densities are 1.0×10~8 cm~(-2) and 1.8×10~(10) cm~(-2),which agree with the results observed from TEM.     

High-temperature superconducting filter using self-embedding asymmetric stepped impedance resonator with wide stopband performance and miniaturized size

In this study, a novel self-embedding asymmetric stepped impedance resonator(SE-ASIR) topology is proposed. By embedding asymmetric stepped impedance resonators in themselves, circuit sizes of ASIRs can be reduced effectively,while the ability to control spurious modes of ASIRs remains. Therefore, SE-ASIRs are suitable for being used to design filters with wide stopbands and miniaturized sizes. Furthermore, the construction process of the SE-ASIR is described in detail, and an equivalent model of the SE-ASIR is proposed. For demonstration, a high-temperature superconducting bandpass filter centered at 1112 MHz is designed and fabricated. The measured result agrees well with the simulation result and shows that the out-of-band rejection is better than 60 dB up to 4088 MHz, which is about 3.7 times the center frequency.The filter circuit size is 31 mm ×13 mm or 0.28λ_g× 0.12λ_g, where λ_g is the guided wavelength at 1112 MHz.     

Bi-2223高温超导带材焊接接头电阻和过电流冲击性能实验研究

特变电工股份有限公司,昌吉831100采用自行研制的装置,对不锈钢加强Bi2223/Ag高温超导带材的焊接工艺进行了系统研究,得出最佳的焊接方案.实验测量高温超导带材焊接头的直流电阻,并对带材进行了交流过电流冲击实验,冲击时间为0.5秒,每次冲击的电流依次递增,并在每次冲击后测量焊接头的电阻,直到被测带材烧毁.根据实验数据对样品在过流冲击下的动态电阻进行实验研究,得到了具有实际意义的结果.