Low pressure carbon dioxide solubility in pure electrolyte solvents for lithium-ion batteries as a function of temperature. Measurement and prediction

Experimental values for the carbon dioxide solubility in eight pure electrolyte solvents for lithium ion batteries – such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ?-butyrolactone (?BL), ethyl acetate (EA) and methyl propionate (MP) – are reported as a function of temperature from (283 to 353) K and atmospheric pressure. Based on experimental solubility data, the Henry’s law constant of the carbon dioxide in these solvents was then deduced and compared with reported values from the literature, as well as with those predicted by using COSMO-RS methodology within COSMOthermX software and those calculated by the Peng–Robinson equation of state implemented into Aspen plus. From this work, it appears that the CO2 solubility is higher in linear carbonates (such as DMC, EMC, DEC) than in cyclic ones (EC, PC, ?BL). Furthermore, the highest CO2 solubility was obtained in MP and EA solvents, which are comparable to the solubility values reported in classical ionicliquids. The precision and accuracy of the experimental values, considered as the per cent of the relative average absolute deviations of the Henry’s law constants from appropriate smoothing equations and from literature values, are close to (1% and 15%), respectively. From the variation of the Henry’s law constants with temperature, the partial molar thermodynamic functions of dissolution such as the standard Gibbs free energy, the enthalpy, and the entropy are calculated, as well as the mixing enthalpy of the solvent with CO2 in its hypothetical liquid state

A Vanadium Redox Flow Battery based on a highly concentrated Protic Ionic Liquid Electrolyte

This is the final version of the following article : A Vanadium Redox Flow Battery based on a highly concentrated Protic Ionic Liquid Electrolyte, which has been published in final form at https://www.lestudium-ias.com/content/vanadium-redox-flow-battery-based-highly-concentrated-protic-ionic-liquid-electrolyteInternational audienc

Effect of cation (Li+, Na+, K+, Rb+, Cs+) in aqueous electrolyte on the electrochemical redox of Prussian blue analogue (PBA) cathodes

International audiencePrussian blue analogue (PBA) material is a promising cathode for applications in Na-ion and K-ion batteries which can support high c-rates for charge and discharge. In this study, the material of composition [K2CuIIFeII(CN)6] was synthesized and its structural and electrochemical redox behavior was investigated with 5 different alkali insertion cations (Li+, Na+, K+, Rb+, Cs+). Galvanostatic measurements indicate that the redox potential strongly depends on the ionic radius of the inserted cation. The redox potential varies by ∼400 mV between using Li+ (0.79 Å) or Cs+ (1.73 Å) in the electrolyte. The underlying modification of the Fe2+/Fe3+ redox potential in PBA is proposed to be due to the weakening of the Fe–C bond in the material. This hypothesis is supported by XRD measurements which reveal that the lattice parameter of the de-intercalated host structure follows the same trend of monotonic increase with the cation size. The relatively minor volume changes accompanying the redox (1.2%–2.4%) allow the PBA to accommodate differently sized cations, although the structural hindrances are quite pronounced at high c-rates for the larger ones (Rb+ and Cs+). Cycle aging studies indicate that the minimum capacity fade rate is observed in case of K+ and Rb+ containing electrolyte. The peak intensity corresponding to the [220] crystallographic plane varies depending on the state of charge of PBA, since this plane contains the insertion cations. Owing to the sensitivity of the redox potential to the insertion cation coupled with the observed fast ion-exchange ability, the PBA material may find additional analytical applications such as ion sensing or filtration devices

Deep eutectic solvents based on <em>N</em>-methylacetamide and a lithium salt as suitable electrolytes for lithium-ion batteries

International audienceIn this work, we present a study on the physical and electrochemical properties of three new Deep Eutectic Solvents (DESs) based on N-methylacetamide (MAc) and a lithium salt (LiX, with X = bis[(trifluoromethyl)sulfonyl]imide, TFSI; hexafluorophosphate, PF6; or nitrate, NO3). Based on DSC measurements, it appears that these systems are liquid at room temperature for a lithium salt mole fraction ranging from 0.10 to 0.35. The temperature dependences of the ionic conductivity and the viscosity of these DESs are correctly described by using the Vogel–Tammann–Fulcher (VTF) type fitting equation, due to the strong interactions between Li+, X− and MAc in solution. Furthermore, these electrolytes possess quite large electrochemical stability windows up to 4.7–5 V on Pt, and demonstrate also a passivating behavior toward the aluminum collector at room temperature. Based on these interesting electrochemical properties, these selected DESs can be classified as potential and promising electrolytes for lithium-ion batteries (LIBs). For this purpose, a test cell was then constructed and tested at 25 °C, 60 °C and 80 °C by using each selected DES as an electrolyte and LiFePO4 (LFP) material as a cathode. The results show a good compatibility between each DES and LFP electrode material. A capacity of up to 160 mA h g−1 with a good efficiency (99%) is observed in the DES based on the LiNO3 salt at 60 °C despite the presence of residual water in the electrolyte. Finally preliminary tests using a LFP/DES/LTO (lithium titanate) full cell at room temperature clearly show that LiTFSI-based DES can be successfully introduced into LIBs. Considering the beneficial properties, especially, the cost of these electrolytes, such introduction could represent an important contribution for the realization of safer and environmentally friendly LIBs

An amide based polyvinyl alcohol / protic ionic liquid (PVA / PIL) gel electrolyte for supercapacitor applications

International audienceAn aqueous gel based on polyvinyl alcohol (PVA) and a mixture of two nitrate salts, namely lithium nitrate (LiNO3) and pyrrolidinium nitrate, PIL (PyrrNO3) was prepared and used as an electrolyte. The gel electrolyte shows a high conductivity in the presence of formamide (FMD), which was studied as an organic additive in the gel at 5 to 400 % with respect to the salt content. Their electrochemical behaviors were examined by cyclic voltammetry, galvanostatic charge-discharge and an impedance technique at room temperature (17°C). The 100 % of amide in the gel has shown a maximum ionic conductivity of 33 x 10-3 and 11.2 x 10-3 Scm-1 at 17°C and-20°C respectively. A two electrode supercapacitor (SC) was assembled and analyzed. The cycle life is improved by the additive over the bare gel, as evidenced by the galvanostatic cycling. The specific discharge capacitance of SC based on the 100% of amide can be used for delivering 34.2, 27.3 and 21 Fg-1 at 1.5 V under a constant current density of 50, 100 and 500 mAg-1 respectively. Moreover, the SC efficiency was maintained at 95%, and above as well as the capacity loss was minimized in the presence of the additive. This quasi solid-state supercapacitor will be capable of delivering an energy density of 12-13 Whkg-1 and maximum power density of 0.60 kWkg-1 at 2 V. The results confirm that the capacitive enhancement is at the lower limit of the FMD

Effect of low water content in protic ionic liquid on ions electrosorption in porous carbon: application to electrochemical capacitors

International audienceThe effect of low water content (<20, 150, 1000, 10[thin space (1/6-em)]000 ppm) in triethylammonium bis[(trifluoromethyl)sulfonyl]imide – [(C2H5)3N+H][TFSI−] – protic ionic liquid (PIL) on the performance of activated carbon (AC) electrodes as well as AC/AC electrochemical capacitors (ECs) is reported. Under negative polarization, hydrogen electrosorption onto carbon is enhanced along with the increase of water content in PIL, whereas the resulting desorption peaks are shifted to lower potential values, evidencing lower sorption energy when hydrogen is stored from moisture containing PIL. Cyclic voltammetry (CV) investigations on PIL-based ECs demonstrated that the evolution of the Stern layer nanostructure at positive and negative potentials is asymmetrical. The results revealed comparable electrochemical performance for PIL containing 150 and 1000 ppm of H2O, due to similar operation of the positive electrode, where [TFSI−] anions are adsorbed in the outer Helmholtz plane, and the negative one, where hydrogen is stored through the reduction of the intermediate hydronium cation. By contrast, a cell with “dry” PIL (<20 ppm of water) displayed a distinctive operation due to hydrogen electrosorption directly through reduction of the protonated cation, and selective adsorption of [TFSI−] anions, which occurs thanks to the high polarizability and image force (IF) created by their induced charge. Galvanostatic cycling with potential limitation (GCPL) showed comparable capacitance values whatever the water content in PILs up to 1000 ppm, yet electrochemical impedance spectroscopy (EIS) revealed higher capacitance as well as better retention at higher frequencies with the PIL containing 150 ppm of water. Hence, 150 ppm is reasoned to be an optimal value for diffusion and adsorption of ions. The nature of current collectors (aluminum or stainless steel) has a determining role in their polarization behavior, and consequently the potential range of electrodes as well as ion diffusion into the activated carbon porosity, influencing the observed capacitance values (CEIS/2.0V: 170 vs. 128 F g−1, for Al and SSt, respectively)

Pyrrolidinium octanoate carboxylate as PIL agent in the growth mechanism of lysozyme spherulites

International audienceIn this research the impact of pyrrolidinium octanoate carboxylate (PyO) on Lysozyme (Ly) spherulite forms using the method of vapour diffusion with hanging drops (HDVD) was investigated. Two different stock solutions at low alkaline pH were tested: 0.1 M NaAc (the first one) and 0.1 M TRIS hydrochloride contained 0.2 M ammonium sulfate and 25 % wt. PEG 3450 as crystallant agents (the second one). The experiments were performed at 18°C using two PyO concentrations (0.4 M and 1.6 M) in each stock solution. PyO of booth concentrations lead to the formation of Ly - SNLC (Ly single needle-like crystals), observed by optical microscopy one day after the droplets deposition, excepted the stock solution of 0.1 NaAc based on 0.4 M PyO where Ly microspheres were identified by electron scanning microscopy. The growth mechanism of the Ly spherulites of type I obtained using 0.4 M PyO in 0.1 M TRIS/crystallant agent could be summarised as follows: Ly-SNLC → Ly-like axialites → Ly spherulites of type I. The growth mechanism of the Ly spherulites of type II using 1.6 M PyO in 0.1 M TRIS/crystallant agent can be summarised as follows: Ly-SNLC → Ly-like axialites → Ly spherulites of type II