Additives electrolytes

Knoevenagel condensation of malonic acid with heptaldehyde [111-71-7] followed by ring closure, gives the fragrance y-nonanoic lactone [104-61-0] (6) (14). Beside organic synthesis, malonic acid can also be used as electrolyte additive for anodization of aluminum [7429-90-5] (15), or as additive in adhesive compositions (16). 

Secondary lithium-metal batteries which have a lithium-metal anode are attractive because their energy density is theoretically higher than that of lithium-ion batteries. Lithium-molybdenum disulfide batteries were the world s first secondary cylindrical lithium—metal batteries. However, the batteries were recalled in 1989 because of an overheating defect. Lithium-manganese dioxide batteries are the only secondary cylindrical lithium—metal batteries which are manufactured at present. Lithium-vanadium oxide batteries are being researched and developed. Furthermore, electrolytes, electrolyte additives and lithium surface treatments are being studied to improve safety and recharge-ability. 

Films on lithium play an important part in secondary lithium metal batteries. Electrolytes, electrolyte additives, and lithium surface treatments modify the lithium surface and change the morphology of the lithium and its current efficiency [93],... 

There have been many attempts to improve the cycling efficiency of lithium anodes. We describe some of them below, by discussing electrolytes, electrolyte additives, the stack pressure on the electrode, composite anodes, and alternatives to the lithium-metal anode anode. 

There have been many studies with the goal of improving lithium cycling efficiency by the use of electrolyte additives. These additives can be classified into three types ... 

Furthermore, the molecular size of the Li+ -solvating solvents may affect the tendency for solvent co-intercalation. Crown ethers [19, 152-154, 196, 197] and other bulky electrolyte additives [196] are assumed to coordinate Li+ ions in solution in such a way that solvent co-intercalation is suppressed. The electrochemical formation of binary lithiated graphites Li tC6 was also reported for the reduction... 

Effects on the micellar shape are also induced by electrolyte addition. It has been observed that, in decane, the water-containing AOT-reversed micelles become more spherical upon addition of salt (NaCl, CaCli) [6]. 

The trends of behavior described above are found in solutions containing an excess of foreign electrolyte, which by definition is not involved in the electrode reaction. Without this excess of foreign electrolyte, additional effects arise that are most distinct in binary solutions. An appreciable diffusion potential q) arises in the diffusion layer because of the gradient of overall electrolyte concentration that is present there. Moreover, the conductivity of the solution will decrease and an additional ohmic potential drop will arise when an electrolyte ion is the reactant and the overall concentration decreases. Both of these potential differences are associated with the diffusion layer in the solution, and strictly speaking, are not a part of electrode polarization. But in polarization measurements, the potential of the electrode usually is defined relative to a point in the solution which, although not far from the electrode, is outside the diffusion layer. Hence, in addition to the true polarization AE, the overall potential drop across the diffusion layer, 9 = 9 + 9ohm is included in the measured value of polarization, AE. ... 

A final observation consistent with rate-determining cycli-zation is that the reaction rate is relatively insensitive to added electrolyte. Addition of 0.5 equivalents of tetra-n-butylammonium chloride or tetra-n-butylammonium azide to chloroform solutions of... 

The future remains bright for the use of carbon materials in batteries. In the past several years, several new carbon materials have appeared mesophase pitch fibers, expanded graphite and carbon nanotubes. New electrolyte additives for Li-Ion permit the use of low cost PC based electrolytes with natural graphite anodes. Carbon nanotubes are attractive new materials and it appears that they will be available in quantity in the near future. They have a high ratio of the base plane to edge plain found in HOPG. The ultracapacitor application to deposit an electronically conductive polymer on the surface of a carbon nanotube may be the wave of the future. 

An overview about more than 10 years of R D activities on solid electrolyte interphase (SEI) film forming electrolyte additives and solvents at Graz University of Technology is presented. The different requirements on the electrolyte and on the SEI formation process in the presence of various anode materials (metallic lithium, graphitic carbons, and lithium storage metals/alloys are particularly highlighted. 

Solid electrolyte interphase (SEI), electrolyte additive, lithium ion battery, Li metal, graphite, lithium alloy. 

Figure 4. Charge recoveries vs. wet stand time of LiCn in PC electrolytes without and with electrolyte additives (CO2, N2O, S2 ). Electrolyte 0.5MLiClC>4 inPC,...

Figure 8. Constant current charge/discharge cycling (1.-3. cycles) of graphite (Lonza KS44 synthetic graphite) in 1 MLiCl04 in y-hutyrolactone as electrolyte without and with C02 (saturated in electrolyte) as electrolyte additive, i lOpA mg 1, cut-off 0-1.5V vs. Li/Li+...

Figure 10. Integrated irreversible capacities of LiC in y-butyrolactone based electrolytes without (full symbols) and with (open symbols) C02 as electrolyte additive using various electrolyte salts LiCl04 (top, left), LiBF4 (top, right), LiPF6 (bottom, left), LiN(S02CF3)2 (bottom, right). Carbon Lonza KS44 synthetic graphite, i = 10 pA mg 1, cut-off 0-1.5 V vs. Li/Li+ [12],...

Due to easier handling, liquid electrolyte additives and solvents have found more interest than gaseous additives. Among these components, organic sulfites [14-19] (Fig. 11), partially fluorinated aprotic solvents [12, 20-25], and vinylene additives [24, 26-32] have found particular attention. 

Partially fluorinated components can be used either as electrolyte solvents (Fig. 12) or as electrolyte additives (Fig. 13). In many cases they show much superior SEI forming capabilities compared to their non-fluorinated counterparts. Moreover, fluorinated solvents are in general much less flammable as less hydrogen is available, which might contribute to cell safety [12, 23, 25]. 

In fact, crystalline graphites usually cannot be operated in PC electrolytes, unless effective film forming electrolyte additives are used (see above) as propane gas evolution [35], creation of solvated graphite intercalation compounds (sGICs) [36], and graphite exfoliation take place. Recently [37, 38], it was found that propylene evolution is observed at graphite, while absent at lithium active metallic anodes, e.g., Sn and SnSb. 

Wrodnigg G. H., Besenhard J. O., Winter M., Ethylene sulfite as electrolyte additive for lithium-ion cells with graphitic anodes, J. Electrochem. Soc. (1999), 146 (2), 470-472. 

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