Polar Propylene Carbonate Research Articles

Strong Ion‐Dipole Interactions for Stable Zinc‐Ion Batteries with Wide Temperature Range

AbstractAqueous zinc‐ion batteries are widely recognized as promising alternatives to lithium batteries due to their excellent safety, environmental compatibility, and cost‐effectiveness. Nonetheless, the formation of dendrites, corrosion, and undesirable side reactions on the zinc surface pose significant challenges to the cycling stability of zinc‐ion batteries. In this study, polar propylene carbonate (PC) is paired with tetrafluoroborate anions to establish a strong ion‐dipole interaction. Strong ion‐dipole interaction can not only alter the solvation structure of zinc ions but also facilitate the formation of a dynamic double electric layer on the surface of the zinc electrode, suppressing the formation of ZnF2 interface and carbonate, thereby facilitating uniform zinc ion deposition, and consequently improving battery cycling stability over a broad temperature range. Concretely, the formulated electrolyte enhances the cycling stability of the battery over a wide temperature range of −30 to 40 °C, accompanied by a capacity retention of ≈100% even after 10 000 cycles at −30 °C. The symmetrical battery utilizing this electrolyte exhibits stable cycling performance for over 1200 h at 25 °C and 1900 h at −30 °C, respectively. The findings provide a promising direction for the development of long‐cycle batteries capable of operating over a wide temperature range.

Nonlinear dielectric features of highly polar glass formers: Derivatives of propylene carbonate.

We have measured the nonlinear dielectric behavior of several highly polar propylene carbonate (PC) derivatives in the vicinity of their glass transition temperatures. Focus is on the effects of a large static electric field on the frequency dependent permittivity and on the cubic susceptibility measured using sinusoidal fields of high amplitude. The case of vinyl-PC shows dielectric saturation as well as an electro-rheological effect, i.e., a field induced increase of dielectric relaxation times, whose magnitude changes linearly with the apparent activation energy. The extent of this shift of the loss profile caused by the field correlates strongly with the peak magnitude of the cubic susceptibility, |χ3|, underlining the notion of a link between the |χ3| "hump" and this electro-rheological behavior. Further support for this picture emerges from the observation that the most polar of these liquids, (S)-(-)-methoxy-PC with εs ≈ 250, lacks both the electro-rheological effect in ε″(ω) and the "hump" typically observed in |χ3(ω)|. The absence of any sensitivity of the dynamics to an electric field is contrary to the expectation that the electro-rheological effect correlates with the field induced entropy change, which is extraordinarily high for this liquid. The results suggest that the dependence of the relaxation time on the electric field is not directly linked to the entropy change.

Lithium-Containing Zwitterionic Poly(Ionic Liquid)s as Polymer Electrolytes for Lithium-Ion Batteries

Polymer electrolytes are considered as the good candidates for the new-generation-safe lithium-ion battery. Herein, a free-standing and flexible polymer electrolyte film based on a lithium-containing zwitterionic poly(ionic liquid) (PIL) was constructed with and without propylene carbonate (PC) by in-situ photopolymerization. In this system, the lithium-containing IL synthesized by equimolecular neutralization of imidazolium-type zwitterion 3-(1-vinyl-3-imidazolio)propanesulfonate (VIPS) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) can both serve as the polymeric matrix of the polymer electrolytes to maintain sufficient mechanical strength and form Li+-rich channels for lithium-ion transportation. The ion–dipole interaction between the lithium ion and the polar solvent PC can further improve the lithium-ion conduction, resulting in a comparable ionic conductivity of ∼10–3 S/cm at 30 °C. Charge–discharge cycling performance of Li/LiFePO4 half-cell equipped with the PIL-based polymer electrolyte i...

Li+ Solvation in Pure, Binary, and Ternary Mixtures of Organic Carbonate Electrolytes

Classical molecular dynamics (MD) simulations and quantum chemical density functional theory (DFT) calculations have been employed in the present study to investigate the solvation of lithium cations in pure organic carbonate solvents (ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC)) and their binary (EC-DMC, 1:1 molar composition) and ternary (EC-DMC-PC, 1:1:3 molar composition) mixtures. The results obtained by both methods indicate that the formation of complexes with four solvent molecules around Li+, exhibiting a strong local tetrahedral order, is the most favorable. However, the molecular dynamics simulations have revealed the existence of significant structural heterogeneities, extending up to a length scale which is more than five times the size of the first coordination shell radius. Due to these significant structural fluctuations in the bulk liquid phases, the use of larger size clusters in DFT calculations has been suggested. Contrary to the findings of the DFT calculations on small isolated clusters, the MD simulations have predicted a preference of Li+ to interact with DMC molecules within its first solvation shell and not with the highly polar EC and PC ones, in the binary and ternary mixtures. This behavior has been attributed to the local tetrahedral packing of the solvent molecules in the first solvation shell of Li+, which causes a cancellation of the individual molecular dipole vectors, and this effect seems to be more important in the cases where molecules of the same type are present. Due to these cancellation effects, the total dipole in the first solvation shell of Li+ increases when the local mole fraction of DMC is high.

Continuous synthesis of d, l-α-tocopherol catalyzed by sulfonic acid-functionalized ionic liquid in supercritical carbon dioxide

Continuous synthesis of d, l-α-tocopherol catalyzed by a sulfonic acid-functionalized ionic liquid was conducted in supercritical carbon dioxide (SC-CO 2). The product was continuously separated from the reaction mixture by SC-CO 2 extraction during the course of reaction. Decompression of the supercritical fluid mixture downstream gave the product free of ionic liquid. The yield of d, l-α-tocopherol was improved with non-polar SC-CO 2 and polar propylene carbonate as solvents. The selectivity of d, l-α-tocopherol to trimethylhydroquinone (TMHQ) between CO 2-rich and ionic liquid-rich phase increased with the increase of pressure, and decreased with the increase of temperature at temperatures from 70 to 115 °C and pressures from 15 to 25 MPa. Effect of temperature, pressure and flow rate on the continuous synthesis of d, l-α-tocopherol was studied. The conversion of isophytol (IP) and the yield of d, l-α-tocopherol increased with decreasing pressure. The extraction rate of d, l-α-tocopherol increased with increasing pressure and decreased with increasing temperature. d, l-α-Tocopherol yield of 90.4% was obtained at 100 °C, 20 MPa and a CO 2 residence time of 12.6 min.

Room-Temperature Ionic Liquid-Organic Solvent Mixtures: Conductivity and Ionic Association

Ion-transport properties of room-temperature ionic liquids (RTILs), N, N-diethyl-N-methoxyethyl-N-methyl ammonium (DEME) with different anions, BF4 and (CF3SO2)2N, as well as their mixed systems with two different organic solvents, propylene carbonate (PC) and 1,2-dichloroethane (DCE), have been explored by means of conductometry and pulsed-field-gradient spin-echo (PGSE) NMR diffusivity measurements. In a highly concentrated range from the neat ionic liquids to 1 mol dm−3 solution, an increase in the organic solvent content contributes to an increase in the ionic diffusion coefficients, which is reflected in enhancement of the ionic conductivity. Such increase in the solvent content, on the other hand, promotes the ionic association, even if highly polar PC is introduced as the solvent.