Trifluoromethanesulfonyl azide: an efficient reagent for the preparation of α-cyano-α-diazo carbonyls and an α-sulfonyl-α-diazo carbonyl

The reaction scope of trifluoromethanesulfonyl azide in diazo transfer reactions was extended to include the preparation of α-cyano-α-diazo-carbonyls, phenyl sulfonyl diazoacetophenone and diethyl diazomalonate in high yields. The effect of the bases used in the diazo transfer reactions were found to have a dramatic influence on the success of the reaction with pyridine being the base of choice.     

亲锂电解液在LiNi0.6Mn0.2Co0.2O2／Li二次锂金属电池中的电化学性能

金属锂电池被认为是具有良好前景的下一代高能量密度电池。然而,传统的碳酸酯类电解液与锂的亲和性差,在循环过程中由于锂枝晶的生长和固体电解质膜（SEI）的不稳定导致金属锂电池性能快速衰减。采用1.2 mol／L六氟磷酸锂（LiPF₆）／二氟草酸硼酸锂（LiDFOB）／氟代碳酸乙烯酯（FEC）／碳酸二乙酯（DEC）,并添加了双三氟甲磺酰亚胺锂（LiTFSI）作为电解液,对其在LiNi_0.6Mn_0.2Co_0.2O₂／40 μm-Li（单位面积上负／正极材料的实际容量的比N／P＝2.85）电池中的电化学性能进行了研究。LiNi_0.6Mn_0.2Co_0.2O₂／40 μm-Li电池表现出优异的循环稳定性（循环120圈后,容量保持率>93%）和倍率性能（3C倍率下放电比容量为110 mA·h／g）。良好的电化学性能主要归因于该电解液可以在金属锂表面形成致密且稳定的SEI,并抑制锂枝晶的产生。     

Reference Electrode for Ionic Liquids

Reference electrodes for room temperature ionic liquid (RTIL) applications were constructed that have a known and reproducible potential versus the ferrocene/ferrocenium couple. They are based on reference electrodes of the first kind, Ag/Ag⁺ couple type, or of the second kind, based on Ag/AgCl in M⁺Cl^?. The former uses AgNO₃ salt and the latter tetrabutylammonium chloride, Bu₄NCl, dissolved in acetonitrile which are then introduced to the ionic liquid of choice for a final concentration of 0.1 M. The reference electrodes can be easily and reproducibly constructed. An ionic contact of these reference systems with the test electrolyte was made using an asbestos fiber liquid junction. The internal compartment of the reference system was filled with the same ionic liquid as used for the electrochemical experiment. The performance of these reference electrodes was tested in selected ionic liquids using the ferrocene/ferrocenium redox couple. The stability, reproducibility, and temperature behavior of the two reference systems have been characterized in the following ionic liquids: 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIBF₄), 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI(CF₃SO₂)₂N), and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIPF₆). It has been found that the formal potentials of the examined reference systems are stable over several days. There is a linear relationship for the temperature studied in the range from 25 to 60 °C.     

Lithium solvation in a PMMA membrane plasticized by a lithium‐conducting ionic liquid based on 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide

The Raman and Infrared (IR) spectra of poly(methyl methacrylate) (PMMA) membranes plasticized by ionic liquids of the (1 − x)[1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI)],xLiTFSI type, where BMI⁺ is the 1‐butyl‐3‐methylimidazolium cation and TFSI⁻ the bis(trifluoromethanesulfonyl)imide anion, are analyzed for a lithium bis(trifluoromethane sulfone)imide (LiTFSI) mole fraction x = 0.23 and PMMA contents from 0 to 50 wt%. The lithium is found to have an average coordination of about three CO groups and less than one TFSI⁻ anion. It plays the role of a cross‐linker between the ester groups of PMMA and the nonvolatile ionic liquid. Addition of PMMA to the (1 − x)(BMITFSI),xLiTFSI ionic liquid lowers the conductivity but might improve the lithium transference number by transforming the [Li(TFSI)₂]⁻ anionic clusters present in the pure ionic liquid into a mixed coordination by ester groups and TFSI⁻ anions. Copyright © 2008 John Wiley & Sons, Ltd.     

Mechanically tough dry-free ionic hydrogel microfibers swollen in aqueous electrolyte prepared by microfluidic devices

Soft conducting materials in the shape of microfibers with various functional geometries are crucial for soft electronics. To develop highly stretchable conducting microfibers, a microfluidic method is used to prepare hydrogels in a double-network structure. Based on the coagulation of chitosan in cold water and simultaneous photopolymerization and photocrosslinking of N-isopropylacrylamide and N-diethylacrylamide, long microfibers with controlled uniform diameters can be obtained at the junction of a coaxially aligned microchannel device. After further reinforcement of the chitosan chain and exchange of the medium of the hydrogel microfiber with an aqueous electrolyte of lithium bis(trifluoromethanesulfonyl)imide, the prepared ionic hydrogel exhibits high conductivity and stretchability and dry-free properties. Owing to its mechanical robustness and ionic conductivity, we envision a highly stretchable soft electrode with the prepared ionic hydrogel microfiber that can be stretched up to 900%. This fiber has potential for applications in soft electronics and wearable devices.