Formation of lithium,sodium and potassium complexes with 1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol (taci)

Single crystals of (1,3‐diamino‐5‐azaniumyl‐1,3,5‐trideoxy‐cis‐inositol‐κ³O²,O⁴,O⁶)(1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol‐κ³O²,O⁴,O⁶)lithium(I) diiodide dihydrate, [Li(C₆H₁₆N₃O₃)(C₆H₁₅N₃O₃)]I₂·2H₂O or [Li(Htaci)(taci)]I₂·2H₂O (taci is 1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol), (I), bis(1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol‐κ³O²,O⁴,O⁶)sodium(I) iodide, [Na(C₆H₁₅N₃O₃)₂]I or [Na(taci)₂]I, (II), and bis(1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol‐κ³O²,O⁴,O⁶)potassium(I) iodide, [K(C₆H₁₅N₃O₃)₂]I or [K(taci)₂]I, (III), were grown by diffusion of MeOH into aqueous solutions of the complexes. The structures of the Na and K complexes are isotypic. In all three complexes, the taci ligands adopt a chair conformation with axial hydroxy groups, and the metal cations exhibit exclusive O‐atom coordination. The six O atoms of the resulting MO₆ unit define a centrosymmetric trigonal antiprism with approximate D_3d symmetry. The interligand O...O distances increase significantly in the order Li < Na < K. The structure of (I) exhibits a complex three‐dimensional network of R—NH₂—H...NH₂—R, R—O—H...NH₂—R and R—O—H...O(H)—H...NH₂—R hydrogen bonds. The structures of the Na and K complexes consist of a stack of layers, in which each taci ligand is bonded to three neighbours via pairwise O—H...NH₂ interactions between vicinal HO—CH—CH—NH₂ groups.     

Hydrothermal exfoliated molybdenum disulfide nanosheets as anode material for lithium ion batteries

Ultrathin MoS2nanosheets were prepared in high yield using a facile and effective hydrothermal intercalation and exfoliation route. The products were characterized in detail using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that the high yield of MoS2nanosheets with good quality was successfully achieved and the dimensions of the immense nanosheets reached 1 μm–2 μm. As anode material for Li-ion batteries, the as-prepared MoS2nanosheets electrodes exhibited a good initial capacity of 1190 mAh g-1and excellent cyclic stability at constant current density of 50 mA g-1. After 50 cycles, it still delivered reversibly sustained high capacities of 750 mAh g-1.     

基于废旧锂电池回收制备LixMO (x=0.79, 0.30, 0.08; M=Ni/Co/Mn)材料作为锂-氧气电池正极催化剂的电化学性能研究

锂-氧气电池因其超高的理论比容量而受到科研界的广泛关注, 但其存在较为严重的充放电极化和较差的循环稳定性等问题, 从而极大地限制其商业化进程. 因此设计出有效的正极催化剂是解决锂-氧气电池面临的这些棘手问题的必要手段. 通过对不同充电状态的废旧锂电池正极进行回收制得三种不同锂含量的多元金属氧化物Li_xMO (x=0.79, 0.30, 0.08; M=Ni/Co/Mn), 并分别用作锂-氧气电池正极催化剂. 系统研究了Li_xMO材料中锂含量及晶体结构对其电化学性能的影响. 电化学测试结果表明, 与Li_0.79MO和Li_0.08MO催化剂相比, 基于Li_0.30MO为正极催化剂的锂-氧气电池在电流密度100 mA•g^–1和限定容量800 mAh•g^–1的条件下具有较高的放电比容量(14655.9 mAh•g^–1)、较低的充电电压(3.83 V)和较高的能量转换效率(72.2%). 而且该电池体系在充放电循环140圈后充电终止电压仍低于4.3 V. 最终认为制得的Li_0.30MO材料具有优异的催化性能归因于其稳定的层状-岩盐相复合结构以及结构中富含的氧化镍相和氧空位之间的协同作用. 这些优点能够促进放电产物的可逆形成与分解, 从而提高锂-氧气电池循环性能.     

基于Li-N2电池体系的“连续式”氮气还原合成氨

电化学合成氨近年来受到较多关注, 直接的电化学固氮法(NRR)存在产氨来源不明的问题, 而间接的锂式合成氨(LiNR)被认为是一种可行的固氮方案. LiNR的研究多为电沉积锂, 本工作以Li-N₂电池体系为基础, 利用电池的放电反应固定N₂, 质子源H₂O同时参与反应, 理论上提高了Li-N₂电池的放电电压. 结合充电反应锂盐分解, 构成了清晰的锂循环方案. 研究发现, 当N₂和H₂O共同通入电池, 可以实现连续式的NH₃生产, 且放电电位与理论值接近. 充放电循环显示, 每个循环均可以产生NH₃, 产氨量随循环次数而增加. 该方案可循环利用锂, 对于开发新型的固氮方式有较大的研究与利用价值.     

Mesoionic Dithiolates (MIDts) Derived from 1,3-Imidazole-Based Anionic Dicarbenes (ADCs)

Mesoionic dithiolates [(MIDt^Ar)Li(LiBr)₂(THF)₃] (MIDt^Ar={SC(NDipp)}₂CAr; Dipp=2,6-iPr₂C₆H₃; Ar=Ph 3 a , 3-MeC₆H₄ (3-Tol) 3 b , 4-Me₂NC₆H₄ (DMP) 3 c ) and [(MIDt^Ph)Li(THF)₂] ( 4 ) are readily accessible (in≥90 % yields) as crystalline solids on treatments of anionic dicarbenes Li(ADC^Ar) ( 2 a - c ) (ADC^Ar={C(NDipp)₂}₂CAr) with elemental sulfur. 3 a - c and 4 are monoanionic ditopic ligands with both the sulfur atoms formally negatively charged, while the 1,3-imidazole unit bears a formal positive charge. Treatment of 4 with (L)GeCl₂ (L=1,4-dioxane) affords the germylene (MIDt^Ph)GeCl ( 5 ) featuring a three-coordinated Ge atom. 5 reacts with (L)GeCl₂ to give the Ge−Ge catenation product (MIDt^Ph)GeGeCl₃ ( 6 ). KC₈ reduction of 5 yields the homoleptic germylene (MIDt^Ph)₂Ge ( 7 ). Compounds 3 a - c and 4 – 7 have been characterized by spectroscopic studies and single-crystal X-ray diffraction. The electronic structures of 4 – 7 have been analyzed by DFT calculations.     

Revealing the Reaction and Fading Mechanism of FeSe2 Cathodes for Rechargeable Magnesium Batteries

Rechargeable Mg batteries (RMBs) are advantageous large-scale energy-storage devices because of the high abundance and high safety, but exploring high-performance cathodes remains the largest difficulty for their development. Compared with oxides and sulfides, selenides show better Mg-storage performance because the weaker interaction with the Mg²⁺ cation favors fast kinetics. Herein, nanorod-like FeSe₂ was synthesized and investigated as a cathode for RMBs. Compared with microspheres and microparticles, nanorods exhibit higher capacity and better rate capability with a smaller particle size. The FeSe₂ nanorods show a high capacity of 191 mAh g⁻¹ at 50 mA g⁻¹ and a good rate performance of 39 mAh g⁻¹ at 1000 mA g⁻¹. Ex situ characterizations demonstrate the Mg²⁺ intercalation mechanism for FeSe₂, and a slight conversion reaction occurs on the surface of the particles. The capacity fading is mainly because of the dissolution of Fe²⁺, which is caused by the reaction between Fe²⁺ and Cl⁻ of the electrolyte during the charge process on the surface of the particles. The surface of FeSe₂ is mainly selenium after long cycling, which may also dissolve in the electrolyte during cycling. The present work develops a new type of Mg²⁺ intercalation cathode for RMBs. More importantly, the fading mechanism revealed herein has considered the specificity of Mg battery electrolyte and would assist a better understanding of selenide cathodes for RMBs.     

热熔灌输法制备三维骨架支撑金属锂复合负极

金属锂因具有极高的理论比容量(3860 mAh/g)和最低的电化学势(相对于标准氢电极为-3.04 V),被认为是下一代高比能锂离子电池的首选负极材料。然而,金属锂负极在电池循环过程中发生的刺状枝晶生长和体积变化等问题严重阻碍了其产业化应用进程。近年来研究表明,通过在金属锂中引入具有三维(3D)结构的宿主骨架,不但能有效抑制锂枝晶的生长,而且可以缓解金属锂负极的体积变化,从而提高金属锂电池的循环性能与安全性。因此,设计3D骨架/金属锂复合负极被认为是一种能有效解决金属锂问题的新兴策略。本文综述了热熔灌输法制备3D骨架/金属锂复合负极的研究进展。首先讨论了当前基于3D骨架的预存金属锂技术,然后着重分析了热熔灌输策略中3D骨架锂润湿性的影响因素,以及不同3D骨架修饰特征和改性方法。最后对3D骨架/金属锂复合负极和热熔灌输策略现存问题进行了总结并提出未来的发展方向。     

定量的复合金属锂作为三维泡沫锂电极用于锂电池的研究

金属锂作为电池的负极材料具有极高的比容量和极低的氧化还原电位,能够显著提升电池的能量密度。然而,金属锂负极在实际应用中所面临的主要问题是锂枝晶、界面副反应和电极体积变化大的难题。在本文中,我们提出了一种通过将定量的金属锂与三维骨架进行复合形成三维泡沫锂负极的策略,并利用三维泡沫锂来抑制锂枝晶的生长和缓解电极的体积变化。因此,三维泡沫锂电极有利于金属锂负极的高效利用,并能借助其与平面锂箔相比更高的比表面积和更多的反应位点来提升电池的倍率性能。因此,通过采用三维泡沫锂,对称电池的循环寿命和倍率性能都得到了有效的提升。EIS数据结果表明,三维泡沫锂能够减小对称电池的电荷转移阻抗。而且,将三维泡沫锂作为负极组装的LTO全电池,与锂箔作为负极相比,循环1000周平均放电比容量从65 mAh·g^-1提升至121 mAh·g^-1。     

MIL-101(Cr) Microporous Nanocrystals Intercalating Graphene Oxide Membrane for Efficient Hydrogen Purification

Graphene oxide (GO) is a promising two-dimensional building block for fabricating high-performance gas separation membranes. Whereas the tortuous transport pathway may increase the transport distance and lead to a low gas permeation rate, introducing spacers into GO laminates is an effective strategy to enlarge the interlayer channel for enhanced gas permeance. Herein, we propose to intercalate CO₂-philic MIL-101(Cr) metal-organic framework nanocrystals into the GO laminates to construct a 2D/3D hybrid structure for gas separation. The interlayer channels were partially opened up to accelerate gas permeation. Meanwhile, the intrinsic pores of MIL-101 provided additional transport pathways, and the affinity of MIL-101 to CO₂ molecules resulted in higher H₂/CO₂ diffusion selectivity, leading to a simultaneous enhancement in gas permeance and separation selectivity. The MIL-101(Cr)/GO membrane with optimal structures exhibited outstanding and stable mixed-gas separation performance with H₂ permeance of 67.5 GPU and H₂/CO₂ selectivity of 30.3 during the 120-h continuous test, demonstrating its potential in H₂ purification application.     

Zn(ferulate)-LSH Systems as Multifunctional Filters

Excessive UV solar radiation exposure causes human health risks; therefore, the study of multifunctional filters is important to skin UV protective ability and also to other beneficial activities to the human organism, such as reduction of reactive oxygen species (ROS) responsible for cellular damages. Potential multifunctional filters were obtained by intercalating of ferulate anions into layered simple metal hydroxides (LSH) through anion exchange and precipitation at constant pH methods. Ultrasound treatment was used in order to investigate the structural changes in LSH-ferulate materials. Structural and spectroscopic analyses show the formation of layered materials composed by a mixture of LSH intercalated with ferulate anions, where carboxylate groups of ferulate species interact with LSH layers. UV-VIS absorption spectra and in vitro SPF measurements indicate that LSH-ferulate systems have UV shielding capacity, mainly UVB protection. The results of reactive species assays show the ability of layered compounds in capture DPPH^•, ABTS^•+, ROO^•, and HOCl/OCl⁻ reactive species. LSH-ferulate materials exhibit antioxidant activity and singular optical properties that enable their use as multifunctional filters.