Lithium electrolytes

The metallic salts of trifluoromethanesulfonic acid can be prepared by reaction of the acid with the corresponding hydroxide or carbonate or by reaction of sulfonyl fluoride with the corresponding hydroxide. The salts are hydroscopic but can be dehydrated at 100°C under vacuum. The sodium salt has a melting point of 248°C and decomposes at 425°C. The lithium salt of trifluoromethanesulfonic acid [33454-82-9] CF SO Li, commonly called lithium triflate, is used as a battery electrolyte in primary lithium batteries because solutions of it exhibit high electrical conductivity, and because of the compound s low toxicity and excellent chemical stabiUty. It melts at 423°C and decomposes at 430°C. It is quite soluble in polar organic solvents and water. Table 2 shows the electrical conductivities of lithium triflate in comparison with other lithium electrolytes which are much more toxic (24). 

Table 5. Association constants, triple ion formation constants and limiting conductivities of some lithium electrolytes.

Most compositions of lithium electrolytes are based on solutions of one or more lithium salts in mixtures of two or more solvents, and single-solvent formulations are very rare, if there are any. The rationale behind this mixed solvent formulation is that the diverse and often contradicting requirements of bat-... 

For lithium electrolytes, the only variable in salt structure is the anion. In a given nonaqueous solvent system, the dissociation of a lithium salt would be... 

So far, very few attempts at improving ion conductivity have been realized via the salt approach, because the choice of anions suitable for lithium electrolyte solute is limited. Instead, solvent composition tailoring has been the main tool for manipulating electrolyte ion conductivity due to the availability of a vast number of candidate solvents. Considerable knowledge has been accumulated on the correlation between solvent properties and ion conductivity, and the most important are the two bulk properties of the solvents, dielectric constant e and viscosity rj, which determine the charge carrier number n and ion mobility (w ), respectively. 

Although the above findings came from studies on mixtures of the cyclic carbonate PC with ethers, they remain qualitatively true for mixtures of cyclic and linear carbonates, that is, compositions of the state-of-the-art lithium electrolytes. Most likely, it was the work by Matsuda et al. that delineated the basic guidelines for electrolyte formulation, which eventually led to the formulations by Tarascon and Guyo-mard using cyclic (high e) and linear (low rj) carbonate mixtures. ... 

While Wright and co-workers were the first group of researchers to discover that the ether-based polymer poly (ethylene oxide) (PEG) was able to dissolve inorganic salts and exhibit ion conduction at room temperature, " it was the suggestion from Armand et al. that placed these novel materials at the center stage of lithium electrolyte research for more than a decade.The number of comprehensive reviews on this subject could serve as an indicator of the general enthusiasm for these materials during the period. ... 

Polymer electrolytes have been shown to stabilize the lithium/electrolyte interface, yielding stable and low interface resistance, especially when ceramic additives such as y-LiA102 are used. Furthermore, the 7-LiA102 ceramic additive has been shown to stabilize the polymer amorphous phase and to slow down the recrystallization process [99-103]. Thus, the unique electrochemical performance of lithium metal can be applied in practical devices by substitution of the liquid electrolyte with a solid one whose conductivity and stability can be enhanced with ceramic additives. 

The electrolyte is probably the layer in which the maximum number of difficulties can occur. The use of a solid electrolyte, either a protonic conductor, or a lithium electrolyte is compulsory for practical applications. It can be an oxide [3], such as tantalum pentoxide, or a polymer [4]. The research field about the solid electrolytes is in fast expansion, with probable repercussions on the future of electrochromic devices. 

An aluminum wire was used in a molten potassium chloride/lithium electrolyte and lithium was deposited into the aluminum by potential or current pulses. The electrode with the radius r is shown in Figure 5.16. The diffusion is no longer semi-infinite but is limited by the radius of the wire, where the radial diffusion fronts meet each other. The same conditions hold for a thin sheet of metal. 

Appetecchi, G.B., Croce, R, Romagnoh, R, Scrosati, B., Heider, U. and Oesten, R. 1999. High-performance gel-type lithium electrolyte membranes. 

H. V. Venkatasetty, J. Power Sources 2001, 97-98, 671-673. Novel superadd-based lithium electrolytes for lithium ion and Ethium polymer rechargeable batteries. 

D. Moosbauer, S. Zugmann, M. AmereUer, H. J. Gores, J. Chem. Eng. Data 2010, 55, 1794-1798. Effect of ionic liquids as additives on lithium electrolytes Conductivity, electrochemical stability, and aluminum corrosion. 

Sodium carbonate solution is the preferred electrolyte to give long lasting protection against further CO2 ingress. However, introducing sodium ions can accelerate ASR so in some cases plain tap water is used. A lithium electrolyte has been proposed but re.search is still undetway on whether it is necessary for realkalization as the concrete starts with a low pH, and whether it is effective. 

Sodium, Sliver, Copper Powder, Electrolytic Manganese Dioxide, Tantolum, Cadmium,Lead,Selenium, Lithium, Electrolytic Tin, Electrolytic Manganese. 

Saito Y, Yamamoto H, Nakamura O, Kageyama H, Ishikawa H, Miyoshi T, Matsuoka M (1999) Determination of ionic self-diffusion coefficients of lithium electrolytes using the pulsed field gradient NMR. J Power Sources 81-82 772-776... 

Also these inorganic electrolytes or their mixtures with organic solvents have to be polar, i.e. be constituted from molecular dipoles, and to show a high dielectric constant, again for a high ability to solve and dissociate the lithium electrolyte salt and the products of the discharge reaction. 

J.B. Bates, N.J. Dudney, G.R. Gmzalsld, R.A. Zuhr,A. Choudhury, C.F. Luck,J.D. Robertson, Electrical properties of amorphous lithium electrolyte thin films. Solid State Ionics 53-56, 647-654 (1992)... 

Lithium can be inserted into the material up to at least 0.08 Li" " per formula unit. This level of intercalation is insufficient for the number of lithium and lanthanum cations to exceed unity and so the A sites of the perovskite structure still contain some vacancies at this stoichiometry. Whilst this intercalation process is reversible, experiments using this electrolyte in conjunction with a graphite electrode show that an irreversible oxidation process occurs. The reduction of Ti" " narrows the band gap and leads to electronic conductivity of 0.01 S cm at room temperature. This reactivity and electronic conduction would lead to a rapid discharge via short circuit of a stored battery and so makes these materials unsuitable for use as an lithium electrolyte in these applications. 

Fig. 1 Number of papers on solid-state lithium electrolytes (from ISl Web of Science, September 10, 2014)...

This method is very popular for measuring transference numbers of lithium electrolytes (see references in Table 17.18) because of the very easy procedure and low time costs. But it must be taken into account that the measurement was developed for binary and ideal solid electrolytes, which is often not the case, especially for solid polymer electrolytes, where a large amount of ion-pairs is probable. 

Table 17.18 Transference numbers of various lithium electrolytes measured by several methods.

Bohrike O, Frand G, Rezrazi M, Rousselot C, Ttuche C (1993) Fast ion transport in new lithium electrolytes gelled with PMMA. 1. Influence of polymer concentration. Solid State Ion 66(l-2) 97-104, http //dx.doi.org/10.1016/0167-2738(93)90032-X... 

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