Characterization of Na-substituted LiNi1/3Co1/3Mn1/3O2 cathode materials for lithium-ion battery

Highly crystalline layered Li_1?xNa_xNi_1/3Co_1/3Mn_1/3O₂ (x?=?0, 0.001, 0.01, 0.03, 0.05) materials are synthesized by molten salts method and characterized by scanning electron microscopy, inductively coupled plasma (ICP), X-ray diffraction, Rietveld refinement, and electrochemical measurement, respectively. ICP, SEM, and EDS results show that Na ions are incorporated in LiNi_1/3Co_1/3Mn_1/3O₂. Rietveld refinement results show that suitable Na substitution leads to stable layered structure by full Na occupying in Li layer and further attributes to low cation mixing. Electrochemical studies demonstrate that the Na-substituted LiNi_1/3Co_1/3Mn_1/3O₂ shows improved rate capability and cycling performance compared to that of pure LiNi_1/3Co_1/3Mn_1/3O₂.     

A Dual Component Catalytic System Composed of Non‐Noble Metal Oxides for Li–O2 Batteries with Enhanced Cyclability

One of the great challenges in the development of lithium–oxygen batteries (Li–O₂ batteries) is to synthesize cost‐effective and efficient electrocatalysts to overcome several issues such as high charge overpotential and poor cycle life. Here, an efficient method is reported to fabricate a dual component electrocatalyst made of MnO₂ nanoparticles supported on 1D Co₃O₄ nanorods (MnO₂–Co₃O₄), and its electrochemical behavior as a non‐noble metal cathode catalyst is demonstrated in Li–O₂ batteries. It is found that the as‐made MnO₂–Co₃O₄ catalyst exhibits an enhanced electrochemical performance, such as increased specific capacity (increase to 4023 mA h g^?1 from 2993 mA h g^?1), low charge overpotential (reduce 350 mV), high rate performance, and superior cyclability up to 150 cycles. The excellent electrochemical performance is attributed to the synergistic effects of the dual component catalytic system.     

Piezoelectric properties of PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary ceramics

(1 – x)Pb(Hf_1–yTi_y)O₃–x Pb(Mg_1/3Nb_2/3)O₃ (x = 0.1 ～ 0.25, y = 0.555) ternary piezoelectric ceramics were prepared using the two‐step precursor method. Morphotropic phase boundary (MPB) compositions, located at x = 0.18 ～ 0.22, were confirmed using X‐ray diffraction and by their dielectric, piezoelectric and ferroelectric properties. The optimum dielectric and piezoelectric properties were achieved for the MPB composition 0.8Pb(Hf_0.445Ti_0.555)O₃–0.2Pb(Mg_1/3Nb_2/3)O₃, with dielectric permittivity ε_r, piezoelectric coefficient d₃₃, planar electromechanical coupling k_p and Curie temperature T_C being on the order of 2800, 680 pC/N, 70% and 276 °C, respectively. Of particular significance is that the new ternary ceramics exhibit comparable piezoelectric and electromechanical properties to commercial PZT5H ceramics, but with much improved T_C, showing a potential for applications at elevated temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of spherical LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries

Spherical LiNi_1/3Co_1/3Mn_1/3O₂ was successfully prepared by controlled crystallization. The preparation started with the spherical coprecipitate of Ni_1/3Co_1/3Mn_1/3CO₃ from NiSO₄, CoSO₄, MnSO₄, NH₄HCO₃, and NH₃·H₂O, followed by pyrolysis of Ni_1/3Co_1/3Mn_1/3CO₃ at 600°C for 3 h. The X-ray diffraction analysis showed that the homogeneous cubic (Ni_1/3Co_1/3Mn_1/3)₃O₄ was obtained after the pyrolysis. Spherical LiNi_1/3Co_1/3Mn_1/3O₂ was obtained by sintering of the mixture of as-obtained (Ni_1/3Co_1/3Mn_1/3)₃O₄ and LiOH·H₂O at 900°C for 6 h in air. As-prepared spherical LiNi_1/3Co_1/3Mn_1/3O₂ presented initial discharge capacity of 162.9 mA h g⁻¹ and capacity retention of 98% at 50th cycle.     

Novel 1122 thallium cuprates showing high Tc superconductivity: TlCa1-xY,Ba2Cu2O y,T,1-xPb x CaSr2Cu2O y and TlCa0.5Ln0.5Sr2Cu2O y

Substitution of Ca by Y in TlCaBa₂Cu₂O _y does not favour superconductivity, but substitution of Tl by Pb or of Ca by Ln (Ln = Y or rare earth) in TlCaSr₂Cu₂O _y results in high T_c superconductivity (T_c π 60–90 K). TlCa_1-xLn _x Sr₂Cu₂O _y is a new series of high T_c superconductors, but the x = 0.0 composition does not exhibit bulk superconductivity.     

双掺杂BaxAgyCa3-x-yCo4O9氧化物的织构与电输运性能

采用柠檬酸溶胶凝胶和放电等离子烧结制备了Ca位双掺杂型的Ba_xAg_yCa_3-x-yCo₄O₉烧结体,利用X射线衍射仪、扫描电子显微镜、电阻率测试仪等研究了烧结体相组成、取向度、织构及电性能.结果表明：含Ag的掺杂试样中出现了偏离化学计量比分布的Ag单质,掺杂试样取向度随Ba与Ag掺杂量之比x/y的增大而提高,含Ag的掺杂试样取向度低于未掺杂试样,不含Ag的掺杂试样取向度高于未掺杂试样.x=y=01的试样导电机理发生变化.Ba,Ag掺杂量相等的试样保持较低取向度的同时具有较低的电阻率,在973 K时达到最低值（73 mΩcm）,而取向度最低的Ag单掺杂试样电阻率在所有试样中最低,在973 K时为63 mΩcm. 关键词： 3Co₄O₉')" href="#">Ca₃Co₄O₉ 双掺杂 织构 电输运性能     

ZrO2 coating of LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries

ZrO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ materials were prepared by hydroxide precipitation. The structure and electrochemical properties of the ZrO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ were investigated using X-ray diffraction, scanning electron microscope, and charge–discharge tests, indicating that the lattice structure of LiNi_1/3Co_1/3Mn_1/3O₂ were unchanged after the coating but the cycling stability was improved. As the coating amount increased from 0.0 to 0.5 mol.%, the initial capacity of the coated LiNi_1/3Co_1/3Mn_1/3O₂ decreased slightly; however, the cycling stability increased remarkably over the cut-off voltages of 2.5~4.3 V and the capacity retention reached 99.5% after 30 cycles at the coating amount of 0.5 mol.%. ZrO₂ coating also improved the cycling stability of LiNi_1/3Co_1/3Mn_1/3O₂ over wider cut-off voltage of 2.5~4.6 V.     

Characteristics of X‐ray attenuation in electrospun bismuth oxide/polylactic acid nanofibre mats

The characteristics of the X‐ray attenuation in electrospun nano(n)‐ and micro(m)‐Bi₂O₃/polylactic acid (PLA) nanofibre mats with different Bi₂O₃ loadings were compared as a function of energy using mammography (i.e. tube voltages of 22–49 kV) and X‐ray absorption spectroscopy (XAS) (7–20 keV). Results indicate that X‐ray attenuation by electrospun n‐Bi₂O₃/PLA nanofibre mats is distinctly higher than that of m‐Bi₂O₃/PLA nanofibre mats at all energies investigated. In addition, with increasing filler loading (n‐Bi₂O₃ or m‐Bi₂O₃), the porosity of the nanofibre mats decreased, thus increasing the X‐ray attenuation, except for the sample containing 38 wt% Bi₂O₃ (the highest loading in the present study). The latter showed higher porosity, with some beads formed, thus resulting in a sudden decrease in the X‐ray attenuation.     

X-ray, Mössbauer, and dielectric studies of the Co1 − x Ni x Cr2O4 ceramic system

The temperature dependences of the dielectric constant, ?(T), dielectric loss tangent, tanδ(T), and thermostimulated depolarization currents of (Co_{1 ? x} Ni _x )Cr₂O₄:y ⁵⁷Fe₂O₃ samples with 0.2 ≤ x ≤ 0.6 and 0.01 ≤ y ≤ 0.04 exhibit anomalies at temperatures of T ₁ ≈ 220 K and T ₂ ≈ 240 K that indicate a transition to an ordered ferroelectric state at temperatures below T ₂. Also observed at the same temperatures are abrupt changes in the isomer shift and quadrupole splitting for two Mössbauer spectral doublets of a sample with x = 0.2.     

Synthesis and characterization of layered Li1−x(Ni0.5Co0.5)1−yFeyO2(0 ≤ (1 − x) ≤ 1 and 0 ≤ y ≤ 0.2) cathodes

Layered Li(Ni_0.5Co_0.5)_1−yFe_yO₂ cathodes with 0 ≤ y ≤ 0.2 have been synthesized by firing the coprecipitated hydroxides of the transition metals and lithium hydroxide at 700 °C and characterized as cathode materials for lithium ion batteries to various cutoff charge voltages (up to 4.5 V). While the y = 0.05 sample shows an improvement in capacity, cyclability, and rate capability, those with y = 0.1 and 0.2 exhibit a decline in electrochemical performance compared to the y = 0 sample. Structural characterization of the chemically delithiated Li_1−x(Ni_0.5Co_0.5)_1−yFe_yO₂ samples indicates that the initial O3 structure is maintained down to a lithium content (1 − x) ≈ 0.3. For (1 − x) < 0.3, while a P3 type phase is formed for the y = 0 sample, an O1 type phase is formed for the y = 0.05, 0.1 and 0.2 samples. Monitoring the average oxidation state of the transition metal ions with lithium contents (1 − x) reveals that the system is chemically more stable down to a lower lithium content (1 − x) ≈ 0.3 compared to the Li_1−xCoO₂ system. The improved structural and chemical stabilities appear to lead to better cyclability to higher cutoff charge voltages compared to that found before with the LiCoO₂ system.     

TiO2 coating of LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries

TiO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ materials were prepared by the hydrolyzation of Ti(OBu)₄. The impact of TiO₂ coating on the structure and electrochemical properties of LiNi_1/3Co_1/3Mn_1/3O₂ was investigated using X-ray diffraction, scanning electron microscope, and charge–discharge tests. The results indicated that TiO₂ coating did not affect the lattice of LiNi_1/3Co_1/3Mn_1/3O₂, but exhibited obvious effects on its discharge capacity and cycling stability. As coated TiO₂ increased from 0.0 to 2.0 mol%, the initial capacity of samples decreased slightly, but the cycling stability over 2.5∼4.3 V increased remarkably. The capacity retention reached 99.5% at the 50th cycle at a coating amount of 2.0 mol%.     

Magnetic properties of xCoO.(1-x)[2B2O3.K2O] glasses

The results of magnetic investigations onxCoO.(1-x)[2B₂O₃.K₂O] glasses are reported. The magnetic properties of these glasses are dependent on the CoO content. For glasses withx > > 10 mol% CoO, the Co²⁺ ions are coupled antiferromagnetically.     

Effects of strontium on the characteristics of Pb(Zr1/2Ti1/2)O3--Pb(Zn1/3Nb2/3)O3 ceramics

The dielectric and piezoelectric properties of pyrochlore-free lead zirconate titanate-lead zinc niobate ceramics were investigated systematically as a function of Sr doping. The powders of Pb_{(1? x )}Sr _x [0.7(Zr_{1 / 2}Ti_{1 / 2})–0.3(Zn_{1 / 3}Nb_{2 / 3})]O₃, where x?=?0–0.06 were prepared using the columbite-(wolframite) precursor method. The ceramic materials were characterized using X-ray diffraction, dielectric spectra, hysteresis and electromechanical measurements. The phase-pure perovskite phase of Sr-doped PZN--PZT ceramics was obtained over a wide compositional range. The results showed that the optimized electrical properties were also achieved at composition x?=?0.0, which were K _P?=?0.69, d ₃₃?=?670?pC?N^?1, P _r?=?31.9?µC?cm^?2 and ε_rmax?=?18600. Maximum dielectric constant values of the systems decreased rapidly with increasing Sr concentration. Moreover, with increasing Sr concentration dielectric constant versus temperature curves become gradually broader. The diffuseness parameter increased significantly with Sr doping. Furthermore, Sr doping has been shown to produce a linear reduction in the transition temperature (T _m)?=?294.1–12.7x°C with concentration (x). Sr shifts the transition temperature of this system at a rate of 12.7°C?mol^?1%.     

Temperature dependence of anisotropic displacement parameters in O3‐type NaM O2 (M = Cr and Fe): Comparison with isostructural LiCoO2

O3‐type NaM O₂ (M = Cr and Fe) is a promising cathode material for sodium ion secondary batteries (SIBs). Here, we investigate the temperature dependence of anisotropic displacement parameters, U₃₃ and U₁₁, in NaM O₂ by synchrotron radiation X‐ray powder diffraction measurements. In both compounds, the displacement ratios $(r \equiv \sqrt {U_{33} /U_{11} } - 1)$ for M and O are positive, reflecting the out‐of‐plane thermal displacement of the M O₂ layer. On the other hand, the r value for Na is negative, reflecting the two‐dimensional (2D) host structure. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comparative analysis of the effect of La and Co on the superconductivity and energyband spectrum of YBa2Cu3Oy for different oxygen contents

Temperature dependences of the resistivity and Seebeck coefficient of Y(Ba_1−x La_x)₂Cu₃O_y and YBa₂Cu_3−x Co_xO_y samples (x=0–0.25) have been measured under maximum sample saturation with oxygen, as well as following their anneal in an oxygen-deficient atmosphere. The T _c (x) dependences for as-prepared samples were found to pass through a maximum at x=0.05, which persists after annealing for Y(Ba_1−xLa_x)₂Cu₃O_y and disappears for YBa₂Cu_3−x Co_xO_y. A phenomenological model of the band spectrum in normal phase has been used to determine the parameters of the conduction band and of the carrier system, and to analyze their variation with the dopant type and content, as well as with annealing. Despite the differences observed in the T _c (x) dependence, the critical temperatures for all the sample series studied were found to correlate with the conduction-band effective width. The mechanism of the effect of impurities on the band-structure parameters and the reasons for the different influence of annealing on the properties of Y(Ba_1−x La_x)₂Cu₃O_y and YBa₂Cu_3−x Co_xO_y are discussed. Fiz. Tverd. Tela (St. Petersburg) 41, 389–394 (March 1997)     

On the synthesis and properties of ternary copper oxide sulfides (Cu2O1–xSx)

We report on the sputter deposition of copper oxide sulfides Cu₂O_1–xS_x up to a composition of Cu₂O_0.61S_0.39. For higher sulfur contents the films first become amorphous and then change to Cu₂S. Within the range 0 < x < 0.39 the cubic crystal structure is maintained and the lattice constant changes linearly with the sulfur content. The composition of the films is measured by energy dispersive X‐ray fluorescence and suggests the formation of a random alloy. The transmission spectra show a clear red shift of the order of 450 meV (from Cu₂O to Cu₂O_0.61S_0.39) with an average transmission of 70%. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Silicon surface passivation by atomic‐layer‐deposited Al2O3 facilitated in situ by the combination of H2O and O3 as reactants

We investigate the effect of O₃ and H₂O oxidant pre‐pulse prior to Al₂O₃ atomic layer deposition for Si surface passivation. Interfacial oxide SiO_x formed by the O₃ pre‐pulse is more beneficial than that by H₂O to a high level of surface passivation. The passivation of thinner H₂O–Al₂O₃ films is more improved by this O₃ pre‐pulse. O₃ pre‐pulse for 10 nm H₂O–Al₂O₃ reduces saturation current density in boron emitter to 18 fA cm^–2 by a factor of 1.7. Capacitance–voltage measurements reveal this interfacial oxide plays a role of decreasing interface trap density without detrimental effect to negative charge density of Al₂O₃. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

脉冲激光沉积法制备的Ni1-xFexO稀磁半导体的结构和磁性研究

利用脉冲激光沉积方法制备出了具有室温铁磁性的Ni_1-xFe_xO(x=0.02,0.05)稀磁半导体.X射线衍射(XRD)结果表明Ni_1-xFe_xO的晶体结构为NaCl结构,并且在Fe含量较高的Ni_0.95Fe_0.05O中出现了少量的α-Fe₂O₃物相.X射线吸收近 关键词： 1-xFe_xO')" href="#">Ni_1-xFe_xO XANES 脉冲激光沉积方法     

Dielectric and impedance measurements on (1−x)Ba(Fe1/2Ta1/2)O3-xBa(Zn1/3Ta2/3)O3 ceramics

In this work, ((1−x)Ba(Fe_1/2Ta_1/2)O₃-xBa(Zn_1/3Ta_2/3)O₃), ((1−x)BFT-xBZT) ceramics with x = 0.00–0.12 were synthesized by the solid–state reaction method. X-ray diffraction data revealed that both the powders and ceramics were of a pure-phase cubic perovskite structure. All ceramics showed large dielectric constants. For the x = 0.12 sample, a very high dielectric constant (>20,600) was observed. A lowering in the dielectric loss compared to pure BFT ceramics was observed with the BZT addition. The impedance measurements indicated that BZT has a strong effect on the bulk grain and grain boundary resistance of BFT ceramics. These results are in agreement with the measured dielectric properties. Based on dielectric and impedance results, (1−x)BFT-xBZT ceramics could be of great interest for high performance dielectric materials applications due their giant dielectric constant behavior.     

Morphology and magnetic properties of Fe x Co1−x /Co y Fe3−y O4 nanocomposites prepared by surfactants-assisted-hydrothermal process

Recently, we have demonstrated the successful synthesis of Fe _x Co_1−x /Co _y Fe_3−y O₄ nanocomposites with various alkaline solutions by using surfactants-assisted-hydrothermal (SAH) process. In this article, the synthesis of Fe _x Co_1−x /Co_yFe_3−y O₄ nanocomposites with their sizes varying between 20 nm and 2 μm was reported. X-ray powder diffraction (XRD) analyses showed that the surfactants, pH, precipitator, and temperature of the system play important roles in the nucleation and growth processes. The magnetic properties tested by vibrating sample magnetometer (VSM) at room temperature exhibit ferromagnetic behavior of the nanocomposites. These Fe _x Co_1−x /Co _y Fe_3−y O₄ nanocomposites may have a potential application as magnetic carriers for drug targeting because of their excellent soft-magnetic properties.