Mixed solvent electrolytes

Propylsydnone (3-PSD) was proposed as a new solvent by Sasaki et al. [51]. The cycling efficiency of lithium on a Ni electrode of the ternary mixed-solvent electrolyte of 3-PSD, 2MeTHF and 2, 5-dimethyltetrahydrofuran with LiPF6 was about 60 percent, and it was stable with cycling. 

Figure 7 shows the FOM of an AA cell and the PC content in EC/PC binary mixed-solvent electrolytes. With an increase in PC content, the lithium cycling efficiency (Eff) obtained with Li cycling on a stainless steel substrate increases. However, the FOM of the AA cell reaches its maximum value at EC/PC=1 9 [82], This result arises from the interaction between EC and the a-V205-P205 cathode. 

Currently, graphite-based lithium ion batteries use mixed solvent electrolytes containing highly viscous ethylene carbonate (EC) and low viscosity dilutants such as dimethyl carbonate (DMC) or diethyl carbonate (DEC) as main solvents. EC is indispensable because of its excellent filming characteristics. DMC and/or DEC are required to get the low temperature... 

Another type of ternary electrolyte system consists of two solvents and one salt, such as methanol-water-NaBr. Vapor-liquid equilibrium of such mixed solvent electrolyte systems has never been studied with a thermodynamic model that takes into account the presence of salts explicitly. However, it should be recognized that the interaction parameters of solvent-salt binary systems are functions of the mixed solvent dielectric constant since the ion-molecular electrostatic interaction energies, gma and gmc, depend on the reciprocal of the dielectric constant of the solvent (Robinson and Stokes, (13)). Pure component parameters, such as gmm and gca, are not functions of dielectric constant. Results of data correlation on vapor-liquid equilibrium of methanol-water-NaBr and methanol-water-LiCl at 298.15°K are shown in Tables 9 and 10. 

For the industrially important class of mixed solvent, electrolyte systems, the Pitzer equation is not useful because its parameters are unknown functions of solvent composition. A local composition model is developed for these systems which assumes that the excess Gibbs free energy is the sum of two contributions, one resulting from long-range forces between ions and the other from short-range forces between all species. 

Mock B, Evans LB, Chen CC. Thermodynamic representation of phase equilibria of mixed-solvent electrolyte systems. AIChE J 1986 32 1655-1664. 

Reactive absorption processes occur mostly in aqueous systems, with both molecular and electrolyte species. These systems demonstrate substantially non-ideal behavior. The electrolyte components represent reaction products of absorbed gases or dissociation products of dissolved salts. There are two basic models applied for the description of electrolyte-containing mixtures, namely the Electrolyte NRTL model and the Pitzer model. The Electrolyte NRTL model [37-39] is able to estimate the activity coefficients for both ionic and molecular species in aqueous and mixed solvent electrolyte systems based on the binary pair parameters. The model reduces to the well-known NRTL model when electrolyte concentrations in the liquid phase approach zero [40]. 

Therefore, three subjects have been treated the free energy of transfer of individual ions between two solvent media, solvation numbers and the composition of the solvation shell, and the transport of a solvent component in a mixed solvent electrolyte solution. 

During a Hittorf transference experiment in a mixed solvent electrolyte solution, the concentration of the electrolyte as well as the composition of the solvent changes in the electrode compartments. The determination of the solvent transport requires detailed analysis of the electrode compartment. This has been done using refractive index or density measurements electrolysis is limited, the... 

S.-I. Tobishima, K. Hayashi, K.-I. Saito, J.-l. Yamaki, Electrochim. Acta 1995, 40, 537-544. Ethylene carbonate-based ternary mixed solvent electrolytes for rechargeable lithium batteries. 

Sato, K. Yamazaki, I. Okada, S. Yamaki, J., Mixed solvent electrolytes containing fluorinated carboxylic acid esters to improve the thermal stability of lithium metal anode cells. Solid State Ionics 2002,148,463 66. 

Aral, J. Katayama, H. Akahoshi, H., Binary mixed solvent electrolytes containing trifluoro-propylene carbonate for lithium secondary batteries, J. Electrochem. Soc. 2002, 149, A217-A226. 

LiPFe/Alkyl Carbonate Mixed-Solvent Electrolytes.468... 

The thermal stability of some mixed-solvent electrolytes used in Li-ion cells was also measured by DSC [10]. The electrolytes used were EC + diethyl carbonate (DEC), EC -I- DMC, propylene carbonate (PC) + DEC, and PC + DMC in which was dissolved 1 M LiPFe- As shown in Figure 20.6, the exothermic peak of liPFe electrolytes containing DEC was found at 255 °C, and the peak temperature of the electrolytes containing DEC was... 

Thermal stability of graphite and silicon/Li alloy ne tives, LiPFe/Alkyl carbonate mixed-solvent electrolytes, LiPFe/methyl difluoroacetate electrolyte, IiCo02 and FeFs positives with 1 M LiPFe/EC -I- DMC were investigated using DSC. Chained graphite and silicon/Li alloy showed almost the same heat output based on the amoimt of Li in each anode. LiPFe/methyl difluoroacetate electrolyte and FeFs showed a very small heat output. 

Li JD, Lin YZ, Gmehling J (2005) g(E) model for single- and mixed-solvent electrolyte systems. 3. Prediction of salt solubilities in aqueous electrolyte systems. Ind Eng Chem Res 44 1602-1609... 

Wang P, Anderko A, Young RD (2004) Modeling viscosity of concentrated and mixed-solvent electrolyte systems. Fluid Phase Equil 226 71-82. doi 10.1016/j.fluid.2004.09.008... 

In this area a key challenge remains the study of mixed-solvent systems. The preliminary works of Wu and Prausnitz and Patel et on salting out in aqueous solutions are promising, but are also simple cases in which the extreme phase separation and difference in dielectric constant allows the electrolyte to be considered only in one of the two phases this greatly simplifies the treatment of mixture dielectrics. The SAFT-VR-t-DE approach provides another promising route for mixed solvent electrolyte systems, since the dielectric constant is a product of, and not a required input to, the calculations (see for example Figure 8.5). Non-aqueous solvents will also mean that ion pairing will need to... 

Wang P, Springer RD, Anderko A et al (2004) Modeling phase equilibria and speciation in mixed-solvent electrolyte systems. Fluid Phase Equilib 222-223 11-17... 

R. McMillan et al. [43] studied 4-chloro-l,3-dioxolan-2-one (chloro-EC) and 4-fluoro-l,3-dioxolan-2-one (fluoro-EC) to improve the cycling performance of a graphite anode. Chloro-EC mixed solvent electrolyte showed a low current efficiency of ca. 90%. However, fluoro-EC mixed solvent electrolyte showed a high current efficiency of ca. 99.5%. 

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