Zwei neue Silicat-Chloride mit zweiwertigem Europium: LiEu3[SiO4]Cl3 und Li7Eu8[SiO4]4Cl7

Two New Silicate-Chlorides with Divalent Europium: LiEu₃[SiO₄]Cl₃ and Li₇Eu₈[SiO₄]₄Cl₇ LiEu₃[SiO₄]Cl₃ was prepared by reaction of LiCl with Eu₂SiO₄ and Li₇Eu₈[SiO₄]₄Cl₇ from Li with Eu₂O₃, SiO₂ and LiCl. The crystal structures of LiEu₃[SiO₄]Cl₃ (Pmna, a = 946.95(13); b = 699.52(8); c = 1 368.0(2) pm; Z = 4; R1 = 0.0325, R2_w = 0.0642) and Li₇Eu₈[SiO₄]₄Cl₇ (P2₁/c; a = 851.85(5); b = 948.62(7); c = 1 679.0(2) pm; β = 96.221(8)°; Z = 2; R1 = 0.0352, R2_w = 0.0744) were determined from four-circle diffractometer data. LiEu₃[SiO₄]Cl₃ contains [Li(SiO₄)₂] units and LiCl₆ octahedra while in Li₇Eu₈[SiO₄]₄Cl₇ larger ?lithosilicate”? groups are found. In both structures, the Eu²⁺ ions are coordinated mostly eightfold by O^2? and Cl^? ligands.     

Alkylidinphosphane und -arsane. I [P ≡ C?S]−[Li(dme)3]+ – Synthese und Struktur

Alkylidynephosphanes and -arsanes. I [P ≡ C? S]^?[Li(dme)₃]⁺ – Synthesis and Structure O,O′-Diethyl thiocarbonate and bis(tetrahydrofuran)-lithium bis(trimethylsilyl)phosphanide dissolved in 1,2-dimethoxyethane, react below 0°C to give ethoxy trimethylsilane and tris(1,2-dimethoxyethane-O,O′)lithium 2λ³-phosphaethynylsulfanide – [P≡C? S]^? [Li(dme)₃]⁺ – ( 1a ). Apart from bis(trimethylsilyl)sulfane or carbon oxide sulfide, dark red concentrated solutions of λ³-phosphaalkyne 1 are also obtained from reactions of carbon disulfide with bis(tetrahydrofuran)-lithium bis(trimethylsilyl)phosphanide or with the homologous lithoxy-methylidynephosphane ( 2 ) [1]. The ir spectrum shows two absorptions at 1762 and 747 cm^?1 characteristic for the P≡C and C? S stretching vibrations. The nmr parameters {δ(³¹P) ? 121.3; δ(¹³C) 190.8 ppm; ¹J_CP 18.2 Hz} resemble much more values of diorganylamino-2λ³-phosphaalkynes than those of bis(1,2-dimethoxyethane-O,O′)lithoxy-methylidyne-phosphane ( 2a ). As found by an X-ray structure analysis (P2₁/c; a = 1192.6(16); b = 1239.1(19); c = 1414.8(26) pm; β = 105.91(13)° at ?100 ± 3°C; Z = 4 formula units; wR = 0.064) of pale yellow crystals (mp. + 16°C) isolated from the reaction with O,O′-diethyl thiocarbonate, the solid is built up of separate [P≡C? S]^? and [Li(dme)₃]⁺ ions. Typical bond lengths and angles are: P≡C 155.5(11); C? S 162.0(11); Li? O 206.4(17) to 220.3(20) pm; P≡C? S 178.9(7)°.     

Phosphoryl‐Rich Flame‐Retardant Ions (FRIONs): Towards Safer Lithium‐Ion Batteries

The functionalized catecholate, tetraethyl (2,3‐dihydroxy‐1,4‐phenylene)bis(phosphonate) (H₂‐DPC), has been used to prepare a series of lithium salts Li[B(DPC)(oxalato)], Li[B(DPC)₂], Li[B(DPC)F₂], and Li[P(DPC)₃]. The phosphoryl‐rich character of these anions was designed to impart flame‐retardant properties for their use as potential flame‐retardant ions (FRIONs), additives, or replacements for other lithium salts for safer lithium‐ion batteries. The new materials were fully characterized, and the single‐crystal structures of Li[B(DPC)(oxalato)] and Li[P(DPC)₃] have been determined. Thermogravimetric analysis of the four lithium salts show that they are thermally stable up to around 200 °C. Pyrolysis combustion flow calorimetry reveals that these salts produce high char yields upon combustion.     

Effect of Dy3+‐doping on Electrochemical Properties of LiFePO4/C Cathode for Lithium‐Ion Batteries

Dy doping and carbon coating are adopted to synthesize a LiFePO₄ cathode material in a simple solution environment. The samples were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Their electrochemical properties were investigated by cyclic voltammetry (CV) and galvanostatic charge‐discharge tests. An initial discharge capacity of 153 mAh/g was achieved for the LiDy_0.02Fe_0.98PO₄/C composite cathode with a rate of 0.1 C. In addition the electronic conductivity of Dy doped LiFePO₄/C was enhanced to 1.9 × 10^?2 Scm^?1. The results suggest that the improvement of the electrochemical properties are attributed to the dysprosium doping and carbon coating which facilitates the phase transformation between triphylite and heterosite during cycling. XRD data indicate that doping did not destroy the lattice structure of LiFePO₄. To evaluate the effect of Dy substitution, cyclic voltammetry was used at room temperature. prepared. From Cv measurement a more symmetric curve with smaller interval between the cathodic and anodic peak current was obtained by Dy substitution. This denoted a decreasing of polarization with Dy substitution, which illustrated an enhancement of electrochemical performances.     

Reaction de Knoevenagel et de Wittig-Horner En Presence D'oxydes Metalliques. Modification de la Selectivite Du Catalyseur Par Addition De Solvants Ou De Sels Metalliques

MgO et ZnO, modified by addition of a solvent or a metal salt, give very selective reactions by an interfacial solid-liquid process.     

Tunable and Specific Formation of C@NiCoP Peapods with Enhanced HER Activity and Lithium Storage Performance

The superior properties of nanomaterials with a special structure can provide prospects for highly efficient water splitting and lithium storage. Herein, we fabricated a series of peapodlike C@Ni_2?xCo_xP (x≤1) nanocomposites by an anion‐exchange pathway. The experimental results indicated that the HER activity of C@Ni_2?xCo_xP catalyst is strongly related to the Co/Ni ratio, and the C@NiCoP got the highest HER activity with low onset potential of ～45 mV, small Tafel slope of ～43 mV dec^?1, large exchange current density of 0.21 mA cm^?2, and high long‐term durability (60 h) in 0.5 m H₂SO₄ solutions. Equally importantly, as an anode electrode for lithium batteries, this peapodlike C@NiCoP nanocomposite gives excellent charge–discharge properties (e.g., specific capacity of 670 mAh g^?1 at 0.2 A g^?1 after 350 cycles, and a reversible capacity of 405 mAh g^?1 at a high current rate of 10 A g^?1). The outstanding performance of C@NiCoP in HER and LIBs could be attributed to the synergistic effect of the rational design of peapodlike nanostructures and the introduction of Co element.     

高比能高功率全石墨烯锂离子电容器

石墨烯由于拥有超高比表面积和超高电导率而被作为电化学电容器材料广泛研究.本文采用树脂为碳源，通过一种方便快捷的树脂交换法制备一种具有高比表面积的多级孔三维石墨烯（3DG）.经过此种方法的催化、造孔、热处理等主要工艺步骤后，可显著增加石墨烯材料的小、介孔数量，从而提高材料的电化学性能.通过BET测试表明，3DG的比表面积可达2400 m²/g，孔体积达到2.0 cm³/g.以3DG作为正负极材料制备高比能量高功率型锂离子电容器（3DG-LIC），可使3DG-LIC的工作电压从传统超级电容器的2.5 V扩展到4.0 V，能量密度也从20 Wh/kg提高到105 Wh/kg.另外，相同的化学和微观结构能很好地平衡正负极的容量及速率，使高比能量高功率的3DG-LIC具有更宽阔的应用领域.