Synthesis of layered cathode materials Li[CoxNiyMn1-x-y]O2 from layered double hydroxide precursors

Cathode materials Li[CoxNiyMn1-x-y]O2 for lithium secondary batteries have been prepared by a new route using layered double hydroxides (LDHs) as a precursor. The resulting layered phase with the α-NaFeO2 structure crystallizes in the rhombohedral system, with space group R-3m having an interlayer spacing close to 0.47 nm. X-ray photoelectron spectroscopy (XPS) was used to measure the oxidation states of Co, Ni and Mn. The effects of varying the Co/Ni/Mn ratio on both the structure and electrochemical properties of Li[CoxNiyMn1-x-y]O2 have been investigated by X-ray diffraction and electrochemical tests.The products demonstrated a rather stable cycling behavior, with a reversible capacity of 118 mAh/g for the layered material with Co/Ni/Mn = 1/1/1.     

Optimization of the wash process and wash water recycling in the preparation of MgZnAl-CO3 layered double hydroxides

An MgZnAl-CO3 layered double hydroxide (LDH) slurry with Na2 SO4 as the by-product has been prepared by a co-precipitation method.The filtrates in the LDH washing process were collected according to their different levels of salinity.Filtrates with lower salinity can be used to wash a LDH slurry with higher salinity in the next cycle.Only in the final stages is pure water used.Recycling of the wash water in this way has been employed in a commercial production process,resulting in a water-saving of over 80%.The resulting MgZnAl-CO3-LDH product has a well-formed crystalline layered structure with a low content of impurities.     

Unique coordination of pyrazine in T[Ni(CN)4]·2pyz with T=Mn, Zn, Cd

The materials under study, T[Ni(CN)₄]·2pyz with T=Mn, Zn, Cd, were prepared by separation of T[Ni(CN)₄] layers in citrate aqueous solution to allow the intercalation of the pyrazine molecules. The obtained solids were characterized from chemical analyses, X-ray diffraction, infrared, Raman, thermogravimetry, UV-Vis, magnetic and adsorption data. Their crystal structure was solved from ab initio using direct methods and then refined by the Rietveld method. A unique coordination for pyrazine to metal centers at neighboring layers was observed. The pyrazine molecule is found forming a bridge between Ni and T atoms, quite different from the proposed structures for T=Fe, Ni where it remains coordinated to two T atoms to form a vertical pillar between neighboring layers. The coordination of pyrazine to both Ni and T atoms minimizes the material free volume and leads to form a hydrophobic framework. On heating the solids remain stable up to 140 °C. No CO₂ and H₂ adsorption was observed in the small free spaces of their frameworks.     

Synthesis and intracrystalline oxidation of nitrite-intercalated layered double hydroxides

Nitrite-intercalated LDHs could be prepared by a two-stage process that involves coprecipitation in the presence of nitrite ions followed by stirring the product with excess of nitrite ions. The nitrite ion lies flat in these LDHs with its c₂-axis lying approximately perpendicular to the crystallographic c-axis. The interlayer nitrite ions in these LDHs could be quantitatively oxidized to nitrate ions using H₂O₂ solution. In the LDHs thus obtained the nitrate ion lies flat with its c₃-axis parallel to the crystallographic c-axis (D_3h symmetry) in the interlayer region resulting in lower basal spacing.     

The henomeric types of 2-sided patterns in the plane

We extend the classification of pattern types by Grünbaum and Shephard to the 2-sided plane to include patterns having layered or interlaced motifs. Such patterns may have symmetries that turn the plane over. There are 17 infinite families of pattern types for 2-sided rosettes (twelve 1-parameter families and five 2-parameter families), 68 types of 2-sided frieze pattern, and 264 types of 2-sided periodic pattern. The definition of ‘henomeric’ is clarified to ensure that two of the periodic patterns are distinguished.      

Influence of accelerated aging on clay-reinforced polyamide 6

Organically modified clay-reinforced polyamide 6 was subjected to accelerated heat aging to estimate its long-term thermo-oxidative stability and useful lifetime compared to the virgin material. Changes in molecular weight, and thermal and mechanical properties were monitored and connected to the polymer modification encountered during aging. The incorporation of the clay filler was found to result in moderate polymer degradation during processing, which became more pronounced with aging time at elevated temperature, imparting discoloration. Post-crystallization was favoured by short periods of heat exposure, leading to an increase of crystalline content. Conversely, extended chain scission occurring after prolonged residence time negatively affected crystallites' size, lowering the degree of crystallinity. The aging-induced transformations of crystal structures correlated well with materials' mechanical performance, yielding initially hard and brittle specimens which gradually adopted a softening behavior. Relative to the unfilled polymer, the loss of ductility during aging was milder in the case of nanocomposite, indicating that the clay filler restricted degradation, prolonging durability.     

Traffic dynamics on layered complex networks

To minimize traffic congestion, understanding how traffic dynamics depend on network structure is necessary. Many real-world complex systems can be described as multilayer structures. In this paper, we introduce the idea of layers to establish a traffic model of two-layer complex networks. By comparing different two-layer complex networks based on random and scale-free networks, we find that the physical layer is much more important to the network capacity of two-layer complex networks than the logical layer. Two-layer complex networks with a homogeneous physical topology are found to be more tolerant to congestion. Moreover, simulation results show that the heterogeneity of logical and physical topologies makes the packet-delivery process of two-layer networks more efficient in the free-flow state, without the occurrence of traffic congestion.     

Semi-Metallic Superionic Layers Suppressing Voltage Fading of Li-Rich Layered Oxide Towards Superior-Stable Li-Ion Batteries

Li-rich layered oxides (LRLOs) with greater specific capacity density are constrained by voltage attenuation and inferior rate performance because of irreversible oxygen release, metal dissolving and poor lithium-ion transport capacity. Herein, a simple surface modification is designed to solve the performance degradation and structural collapse of LRLOs. Combining experiments with density functional theory (DFT) calculations, a semi-metallic LiMn₂O₄-like structure (LMO) with spin-polarized conducting electrons, is introduced to the surface of the cathode restrains the activated surficial lattice oxygen ions by its stable oxygen vacancies. Additionally, Ni doping results in a fast-ion conductor Li_0.8Nb_0.96Ni_0.2O₃ structure (LNO) with lowered lithium ions diffusion barrier, which is tightly conjugating to substrate and synergistically reinforces the Li diffusion path through the cathode-electrolyte interphase. Moreover, Mn dissolution is successfully relieved due to the decrease in Mn concentration in the coating layers. As a result, the modified material (LRLO@LMO@LNO) exhibits an ultra-high discharge capacity of 120.4 mAh g⁻¹ even at 10 C with a very small discharge voltage attenuation of 313 mV after 600 cycles (0.52 mV per cycle) at 1 C. Undoubtedly, this method discloses a simple and effective approach to promote the practical utilization of high-energy-density.     

用计算模拟方法研究Al_3P_4O_(16)~(3-)计量比的二维层状磷酸铝中的有机胺模板能力

将快速 Monte Carlo方法与分子动力学方法相结合 ,研究了不同种类有机分子在 Al3P4 O3- 1 6 计量比的二维层状磷酸铝形成中的模板能力 .依据主 -客体之间非键相互作用能 (包括范德华能、氢键能和库仑能 ) ,可合理地解释已知实验现象 ,并能有效地预测出适于形成某一特定无机层结构的有机胺模板剂 .通过选择理论预测的有机胺分子作为模板剂 ,成功地合成了二维层状磷酸铝化合物 Al3P4 O1 6 · 1 .5 H3NC6 H1 0 NH3.     

Structure and Thermal Stability of a Novel 2‐D Layered Copper(II) Coordination Polymer with the Bidentate Ligand 1, 2, 4‐Triazol‐5‐one

Single crystals of {[Cu(TO)₂(H₂O)₂](NO₃)₂}_n (TO: 1, 2, 4‐triazol‐5‐one) were grown by slow evaporation from aqueous solution. It crystallizes in the orthorhombic space group Pbca, with a = 7.082(1), b = 10.285(1), c = 17.911(3)Å, V = 1304.6(3)ų, Z = 4. The Cu^II distorted octahedra are bridged by bidentate TO ligands into infinite 2‐D interlaced rhombic grid‐like network planes, {[Cu(TO)₂(H₂O)₂]²⁺}_n. Hydrogen bonds, electrostatic interactions, and weak van der Waals' forces assemble these planes and the NO₃^— anions to a layered structure. The title compound decomposes at 153.4 °C to the final products, Cu(CN)₂ and CuO.