Carbonate ester

Abstract: The intramolecular dinuclear zinc complexes generated in situ from the reaction of multidentate semi-azacrown ether ligands with Et2Zn, followed by treatment with an alcohol additive, were found to promote the copolymerization of CO2 and cyclohexene oxide (CHO) with completely alternating polycarbonate selectivity and high efficiency. With this type of novel initiator, the copolymerization could be accomplished under mild conditions at 1 atm pressure of CO2, which represents a significant advantage over most catalytic systems developed for this reaction so tar. The copolymerization reaction was demonstrated to be a living process as a result of the narrow polydispersities and the linear increase in the molecular weight with conversion of CHO. In addition, the solid-state structure of the dinuclear zinc complex was characterized by X-ray crystal structural analysis and can be considered as a model of the active catalyst. On the basis of the various efforts made to understand the mechanisms of the catalytic reaction, including MALDI-TOF mass analysis of the copolymers' end-groups. the effect of alcohol additives on the catalysis and CO2 pressure on the conversion of CHO, as well as the kinetic data gained from in situ IR spectroscopy. a plausible catalytic cycle for the present reaction system is outlined. The copolymerization is initiated by the insertion of CO2 into the Zn OEt bond to afford a carbonate ester-bridged complex. The dinuclear zinc structure of the catalyst remains intact throughout the copolymerization. The bridged zinc centers may have a synergistic effect on the copolymerization reaction: one zinc center could activate the epoxide through its coordination and the second zinc atom may be responsible for carbonate propagation by nucleophilic attack by the carbonate ester on the back side of the cis-epoxide ring to afford the carbonate. The mechanistic implication of this is particularly important for future research into the design of efficient and practical catalysts for the copolymerization of epoxides with CO2.

Abstract: Electrochemical oxidation of carbonate esters at the LixNi0.5Mn1.5O4−δ/electrolyte interface results in Ni/Mn dissolution and surface film formation, which negatively affect the electrochemical performance of Li-ion batteries. Ex situ X-ray absorption (XRF/XANES), Raman, and fluorescence spectroscopy, along with imaging of LixNi0.5Mn1.5O4−δ positive and graphite negative electrodes from tested Li-ion batteries, reveal the formation of a variety of MnII/III and NiII complexes with β-diketonate ligands. These metal complexes, which are generated upon anodic oxidation of ethyl and diethyl carbonates at LixNi0.5Mn1.5O4−δ, form a surface film that partially dissolves in the electrolyte. The dissolved MnIII complexes are reduced to their MnII analogues, which are incorporated into the solid electrolyte interphase surface layer at the graphite negative electrode. This work elucidates possible reaction pathways and evaluates their implications for Li+ transport kinetics in Li-ion batteries.

Abstract: PURPOSE:To hold high voltage at pulse discharge time over a wide temperature range by using a mixed solvent, in which 1, 2-dimethoxypropane is mixed in carbonic ester, as the solvent of an organic electrolyte CONSTITUTION:A negative electrode 5 with lithium or a lithium alloy serving as an active material, positive electrode 6 with manganese dioxide serving as an active material and an organic electrolyte are provided, and a mixed solvent, in which 1, 2-dimethoxypropane is mixed in carbonate ester, for instance, of propylene carbonate, ethylene carbonate, etc, is used as the solvent of the organic electrolyte By using 1, 2-dimethoxypropane as the mixed solvent of the electrolyte, a solvent system stably existing without freezing and boiling over -50 degC to +85 degC is formed In this way, high voltage can be held at pulse discharge time over a wide temperature range