RU2431908C2 - Chemical source of electric energy - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: rechargeable chemical source of electric energy comprises a positive electrode (cathode), containing sulfur or sulfur-based organic compounds, sulfur-based polymer compounds or sulfur-based inorganic compounds as a depolarisator, a negative electrode (anode) made of metal lithium and from lithium-containing alloys, and electrolyte containing solution of at least one salt in at least one aprotonic dissolvent. The chemical source of electric energy generates soluble polysulfides in electrolyte at the first stage of a double-stage discharging process. Besides, amount of sulfur in the depolarisator and volume of electrolyte are selected so that after the first stage of cathode discharge (down to potential of 2.1-1.9 V), concentration of soluble lithium polysulfides in electrolyte makes at least 70% of lithium polysulfides saturation concentration in electrolyte.

EFFECT: increased specific energy.

4 cl, 10 tbl, 1 dwg, 8 ex

Description

Technical field

The present invention generally relates to electrochemical energy, and in particular relates to chemical sources of electrical energy (to galvanic cells or batteries), which have negative electrodes made of alkali metals, and positive electrodes containing sulfur and / or inorganic compounds on sulfur-based or organic (including polymer) sulfur-based compounds as an electrode depolarizer material.

BACKGROUND OF THE INVENTION

The lithium sulfur electrochemical system has a high theoretical specific energy of 2600 Wh / kg (watt hours per kg) (D.Linden, TBReddy, Handbook of batteries, third ed., McGraw-Hill, New York, 2001), and therefore, it is currently of great interest. Specific energy is defined as the ratio of the energy produced by a galvanic cell or battery to weight and is expressed in watts per kg (Wh / kg). The term specific energy is equivalent to the term gravimetric energy density.

It has already been proposed to use various materials as the positive electrode depolarizer material in lithium-sulfur batteries, including elemental sulfur (US 5,789,108; US 5,814,420), organosulfur compounds (US 6,090,504) containing sulfur polymers (US 6,201,100; US 6,174,621 ; US 6.117,590) and solutions of sulfur or lithium polysulfides in aprotic electrolyte systems (Rauh RD, Abraham KM, Pearson GF, Surprenant JK, Brummer SB: "A lithium / dissolved sulfur battery with organic electrolyte", J. Electrochem. Soc. 1979, vol. 126, no.4, pp. 523-527; Yamin H., Peled E .: "Electrochemistry of nonaqueous lithium / sulfur cell", J. of Power Sources, 1983, vol. 9, pp. 281- 287).

Solutions of lithium salts in aprotic bipolar solvents (and typically in linear or cyclic ethers) or mixtures thereof are already used as electrolytes in lithium-sulfur batteries (Yamin H., Penciner J., Gorenshtain., Elam M., Peled E .: " The electrochemical behavior of polysulphides in tetrahydrofuran ", J. of Power Sources, 1985, vol. 14, pp. 129-134; Yamin H., Gorenshtein., Penciner J., Stemberg Y., Peled E .:" Lithium sulfur battery . Oxidation / reduction mechanisms of polysulphides in THF solution, "J Electrochem Soc., 1988, vol. 135, no.5, pp. 1045-1048; Duck-Rye Chang, Suck-Hyun Lee, Sun-Wook Kim, Hee- Tak Kim: "Binary electrolyte based on tetra (ethylene glycol) dimethyl etner and 1,3-dioxolane for lithium-sulfur battery", J. of Power Sources, 2002, vol. 112, pp. 452-460).

The practical specific energy of a typical chemical source of electrical energy usually reaches 20-30% of the theoretical maximum value of the specific energy of the used electrochemical system. This is because various auxiliary elements (separator, electrode current collectors, electrolyte and other components) of the battery increase its weight in addition to electrode depolarizers. The auxiliary battery cells themselves do not take part in the electrochemical reaction, however, they are necessary to facilitate the reaction and to facilitate the normal functioning of the battery.

The value of the practical specific energy for laboratory lithium-sulfur galvanic cells usually reaches only 10-15% of the theoretical value of the specific energy and typically is about 250-350 Wh / kg (J.Broadhead, T.Skotheim: "A safe, fast-charge, two -volt lithium / polymer cathode 'AA'-size cell with greater than 250 Wh kg-1 energy density ". Journal of Power Sources, 65 (1997), 1-2, 213-218; Peled E., Gorenshtein., Segal M., Stemberg Y .: "Rechargeable lithium-sulfur battery (extended abstract)", J. of Power Sources, 1989, vol. 26, pp. 269-271).

SUMMARY OF THE INVENTION

If you do not take into account the weight of the auxiliary elements of the battery, then we can say that the difference between the theoretical and practical values of the specific energy of laboratory lithium-sulfur galvanic cells is caused by the insufficient use of the depolarizer of the positive electrode (sulfur or sulfur-based compounds) and the excessive amount of the usually introduced electrolyte.

Embodiments of the present invention are directed, at least in large part, to optimizing the amount of electrolyte in lithium-sulfur electrochemical cells in order to thereby increase their practical specific energy.

DETAILED DESCRIPTION OF THE INVENTION

The specific energy of a chemical source of electrical energy is determined by both the theoretical specific energy of the selected electrochemical system and the weight of auxiliary components that are required to ensure the proper operation of the chemical source of electrical energy (for example, such as a separator, electrode current collectors, binder material, conductive additives, electrolyte and other components), as well as the degree (effectiveness) of using a depolarizer. The weight of auxiliary components is usually up to 70-80% of the total weight of the galvanic cell. To increase the specific energy values, it is necessary to reduce the weight of auxiliary components.

The weight of the electrolyte forms a significant part of the total weight of the chemical source of electrical energy. The electrolyte performs additional functions in chemical sources of electric energy with solid depolarizers, for example, it supports the process of electrochemical reaction and ensures the transfer of ions between the electrodes. Therefore, in such systems, it is desirable to minimize the amount of electrolyte.

However, in chemical sources of electrical energy containing liquid cathodes, the electrolyte may contain a salt solution in a liquid depolarizer (for example, a solution of lithium tetrachloroaluminate in thionyl chloride), or a salt solution in a mixture of a liquid depolarizer and an aprotic solvent (for example, a solution of lithium bromide in a mixture of sulfuric anhydride and acetonitrile), or a salt solution in a solution of a liquid depolarizer in an aprotic solvent (for example, a solution of lithium perchlorate in a solution of lithium polysulfide in tetrahydrofuran) (D.Linden, TBReddy: "Handbook of b atteries ", third ed., McGraw-Hill, New York, 2001).

The electrolyte in chemical sources of electrical energy containing liquid cathodes performs a wider range of functions than the electrolyte used in systems having solid cathodes. The electrolyte not only supports the electrochemical reaction and ensures the transfer of ions between the electrodes, but also serves as a solvent for the depolarizer of the positive electrode. Thus, when aprotic solvents are used as a component of a liquid cathode, the characteristics of the specific power of chemical sources of electrical energy with liquid cathodes depend on the content of aprotic solvents and, therefore, on the content of the liquid cathode.

Despite the fact that sulfur and lithium sulfide are poorly soluble in aprotic solvents, lithium-sulfur batteries are classified as batteries with liquid cathodes. This is due to the fact that during the charging and discharging of such batteries, soluble products are formed.

A liquid cathode is formed in lithium-sulfur batteries during the discharge of a sulfur electrode. Electrochemical oxidation of sulfur proceeds in two stages. In the first stage, long-chain lithium polysulfides (which are readily soluble in aprotic electrolytes) are formed during the electrochemical oxidation of elemental sulfur, which is insoluble or poorly soluble in most electrolyte systems (Equation 1).

The solution of lithium polysulfides in the electrolyte, which is formed in the initial phase of the discharge, is a liquid cathode.

In the second stage, the electrochemical reaction of soluble lithium polysulfides proceeds (Equation 2). During this phase, anions of sulfides or disulfides are formed, which, due to reaction with lithium cations, form insoluble products: lithium sulfide and lithium disulfide.

The reduction of soluble lithium polysulfides is accompanied by disproportionation reactions (Equation 3).

The two-stage sulfur recovery mechanism is clearly visible on the discharge curves of lithium-sulfur batteries shown in the drawing. These curves have two discharge regions: the first region at a voltage in the range from 2.5-2.4 V to 2.1-1.9 V, which corresponds to the first phase of the discharge (Equation 1); and the second region at a voltage in the range from 2.1-1.9 V to 1.8-1.5 V, which corresponds to the second phase of the discharge (Equation 2).

The efficiency of using sulfur in lithium-sulfur batteries is determined by the quantitative ratio of sulfur to electrolyte.

When the amount of electrolyte is relatively low, not all sulfur and long chain lithium polysulfides undergo subsequent electrochemical reduction due to the formation of high viscosity saturated polysulfide solutions. This leads to a decrease in the practical specific energy of lithium-sulfur batteries.

When there is an excess of electrolyte, the specific energy of lithium-sulfur batteries will be even lower compared to the maximum possible due to a quantitative excess of electrolyte, which increases the total weight of the galvanic cell. A special ratio of sulfur to electrolyte should be maintained for each type of electrolyte in order to achieve, or at least approach, the maximum practical specific energy.

This ratio depends on the properties of the electrolyte system. In particular, this ratio depends on the solubility of the starting, intermediate and final components.

To achieve the best practical characteristics of the specific energy of lithium-sulfur batteries, the electrolyte content in the batteries should be chosen so as to ensure complete dissolution of lithium polysulfides (formed in the first stage) with the formation of liquid cathodes with moderate viscosity. The applicant of the present invention has found that this condition is satisfied when, during the discharge of the sulfur electrode, the concentration of soluble lithium polysulfides in the electrolyte is at least 70%, and preferably from 70 to 90%, of the saturation concentration.

The present invention provides a chemical source of electrical energy that contains a positive electrode (cathode) containing sulfur or sulfur-based organic compounds, sulfur-based polymeric compounds or sulfur-based inorganic compounds as a depolarizer, a negative electrode (anode) made from lithium metal or from lithium-containing alloys, and an electrolyte containing a solution of at least one salt in at least one aprotic solvent, the chemical The electric energy meter is configured to produce soluble polysulfides in the electrolyte during the first stage of the two-stage discharge process, characterized in that the amount of sulfur in the depolarizer and the volume of the electrolyte are selected so that after the first stage of cathode discharge the concentration of soluble lithium polysulfides in the electrolyte is at least 70% saturation concentration of lithium polysulfides in the electrolyte.

Mostly the amount of sulfur in the positive electrode and the volume of the electrolyte are selected such that after the first stage of cathode discharge, the concentration of soluble lithium polysulfides in the electrolyte is from 70% to 90% of the saturation concentration of lithium polysulfides in the electrolyte.

In a specific embodiment, the depolarizer contains sulfur, carbon black and polyethylene oxide.

The electrolyte may contain a solution of one or more lithium salts selected from the group consisting of lithium trifluoromethanesulfonate, lithium perchlorate, lithium trifluoromethanesulfonimide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrachloroaluminate, lithium tetraalkylammonium, lithium chloride and iodine; in one or more solvents selected from the group consisting of dioxolane, tetrahydrofuran, dimethoxyethane, diglyme, triglyme, tetrahlim, dialkyl carbonates, sulfolane and butyrolactone.

In the text of the description of the present invention and in the claims, the words “comprises” and “includes” and their derivatives, such as, for example, “comprising”, mean “includes, but not limited to” and are not intended to exclude (and do not exclude) the use of other proportions, additives, components, integers or method operations.

In the text of the description of the present invention and in the claims, the use of the singular does not exclude the use of the plural, unless the contrary follows from the context.

The characteristics, features, integers, compounds, chemical fractions or groups described in combination with a particular aspect, variant or example of the invention are applicable to any other aspect, variant or example thereof, unless there is incompatibility with them.

The foregoing and other features of the invention will be more apparent from the following detailed description, given by way of example, not of a restrictive nature and given with reference to the accompanying drawing.

Brief Description of the Drawings

The drawing shows a graph of a two-stage process for discharging a lithium-sulfur battery in accordance with a variant of the present invention.

EXAMPLES

Example 1

Positive electrode containing 70% elemental freeze-dried sulfur (purchased from Fisher Scientific, Loughborough, UK), 10% electrically conductive carbon black (Ketjenblack® EC-600JD, purchased from Akzo Nobel Polymer Chemicals BV, Netherlands) and 20% polyethylene oxide (PEO, molecular weight 4,000,000, purchased from Sigma-Aldrich Company Ltd., Gillingham, UK) was obtained using the following process.

A dry mixture of these components was ground in a high speed mill of the Microtron® MB550 type for 10-15 minutes. Then acetonitrile as a solvent was added to the dry mixture, and the suspension was stirred for 15-20 hours in a DLH type laboratory stirrer. The solids content in the suspension is 10-15%. The suspension thus obtained was applied using an Elcometer® SPRL type automatic film applicator on one side of a 12 μm thick aluminum foil having an electrically conductive carbon coating (Product No. 60303, purchased from Rexam Graphics, South Hadley, Mass., USA) as a collector current.

The coating was dried at ambient conditions for 20 hours and then under vacuum at 50 ° C for 5 hours. The resulting dry active cathode layer has a thickness of 19 μm and contains 2.01 mg / cm ^{2 of the} cathode mixture. The specific surface capacitance of the electrode is 2.35 mA * h / cm ² .

Example 2

The positive electrode from Example 1 was used in a small assembly of galvanic cells made of stainless steel. The surface area of the cathode was 5.1 cm ² . A pressure of 400 kg / cm ² was applied to the electrode before it was used in a galvanic cell. The thickness of the cathode after compression was 16 μm. A 1.0 M solution of lithium trifluoromethanesulfonate (purchased from 3M Corporation, St. Paul, Minn., USA) in sulfolane was used as an electrolyte. Celgard® 2500 (a trademark of material from Tonen Chemical Corporation, Tokyo, Japan, which can also be purchased from Mobil Chemical Company, Films Division, Pittsford, NY, USA) was used as a separator. These components were assembled to create a layered structure containing a positive electrode / separator / anode, together with a liquid electrolyte filling the free volume of the separator and positive electrode. Assembly of galvanic cells was carried out as follows. First, a positive electrode was introduced. Then 4 microliters of electrolyte were deposited onto the electrode using a constant-flow syringe such as CR-700 (Hamilton Co). The separator was placed on top of the wetted electrode and 3 microliters of electrolyte were deposited on the separator. Then, a lithium electrode made of 38 μm thick lithium foil was placed on top of the separator. After assembly of the electrode package, the cell was sealed using a cap having a Teflon seal. The ratio of sulfur to electrolyte is 1 ml of electrolyte per 1 g of sulfur. After the complete dissolution of sulfur in the form of lithium polysulfide during the discharge of the galvanic cell, the measured maximum sulfur concentration in the electrolyte is 31.25 mol per liter.

The charge-discharge cycles of the galvanic cell were carried out at a current of 1.5 mA, which was equivalent to a current density of 0.3 mA / cm ² , with a discharge cut-off voltage of 1.5 V and the end of charging at 2.8 V. The total weight of the galvanic cell and the weight distribution between the components of the galvanic cell are shown in the Table 1, and the characteristics of the cell are shown in Table 2.

The specific energy of the galvanic cell was calculated from the capacitance in the second cycle by dividing the capacitance by the weight of the electrode stack, including the electrolyte.

Table 1. Mass distribution between the components of the lithium-sulfur cell in accordance with Example 2 Cell Component: Weight g Share% Lithium 0.00551 13.1 Sulfur 0.00715 17 Binder material 0.00204 4.8 Carbon 0.00102 2.4 Substrate (+) 0.01021 243 Separator 0.00613 14.6 Electrolyte 0.01001 23.8 Total cell weight 0.04207 100.0

Table 2. The parameters of the lithium-sulfur cell in accordance with Example 2 The total amount of electrolyte, ml 0.007 The amount of electrolyte per 1 g of sulfur, ml one The amount of electrolyte per 1 mAh capacity of the positive electrode, ml / mAh 0.00058 The estimated concentration of lithium polysulfide in the electrolyte after the 1st stage, mol / liter 31.25 Specific Energy, Wh / kg 119 Energy density, Wh / l 130

Example 3

A lithium-sulfur cell was assembled similarly to that described in Example 2, except that 11 microliters of electrolyte were deposited on a positive electrode and 3 microliters of electrolyte were deposited on a separator. The total electrolyte content in the galvanic cell is 14 microliters, which gives 2 ml of electrolyte per 1 g of sulfur. The cyclic tests of the galvanic cell were carried out as described in Example 2. The parameters of the galvanic cell are shown in Tables 3 and 4.

Table 3. Mass distribution between the components of the lithium-sulfur cell in accordance with Example 3 Cell Component: Weight g Share% Lithium 0.00551 10.6 Sulfur 0.00715 13.7 Binder material 0.00204 3.9 Carbon 0.00102 2 Substrate (+) 0.01021 19.6 Separator 0,00613 11.8 Electrolyte 0.02002 38.4 Total cell weight 0.05208 one hundred

Table 4. The parameters of the lithium-sulfur cell in accordance with Example 3 The total amount of electrolyte, ml 0.014 The amount of electrolyte per 1 g of sulfur, ml 1.96 The amount of electrolyte per 1 mAh capacity of the positive electrode, ml / mAh 0.00117 The estimated concentration of lithium polysulfide in the electrolyte after the 1st stage, mol / liter 15.62 Specific Energy, Wh / kg 265 Energy density, Wh / l 301

Example 4

A lithium-sulfur cell was assembled similarly to that described in Example 2, except that 22 microliters of electrolyte were deposited on the positive electrode and 3 microliters of electrolyte were deposited on the separator. The total electrolyte content in the galvanic cell is 25 microliters, which gives 3.5 ml of electrolyte per 1 g of sulfur. Cyclic tests of a galvanic cell were performed as described in Example 2. The parameters of a galvanic cell are shown in Tables 5 and 6.

Table 5. Mass distribution between components of a lithium-sulfur cell according to Example 4 Cell Component: Weight g Share% Lithium 0.00551 8.2 Sulfur 0.00715 10.8 Binder material 0.00204 3 Carbon 0.00102 1.5 Substrate (+) 0.01021 15.2 Separator 0.00613 9.1 Electrolyte 0.03504 52.2 Total cell weight 0.0671 100.0

Table 6. The parameters of the lithium-sulfur cell in accordance with Example 4 The total amount of electrolyte, ml 0,025 The amount of electrolyte per 1 g of sulfur, ml 3.5 The amount of electrolyte per 1 mAh capacity of the positive electrode, ml / mAh 0.0021 The estimated concentration of lithium polysulfide in the electrolyte after the 1st stage, mol / liter 8.928 Specific Energy, Wh / kg 300 Energy Density, Wh / 1 355

Example 5

A lithium-sulfur cell was assembled similarly to that described in Example 2, except that 49 microliters of electrolyte were deposited on a positive electrode and 3 microliters of electrolyte were deposited on a separator. The total electrolyte content in the galvanic cell is 52 microliters, which gives 5.2 ml of electrolyte per 1 g of sulfur. The cyclic tests of the galvanic cell were carried out as described in Example 2. The parameters of the galvanic cell are shown in Tables 7 and 8.

Table 7. Mass distribution between the components of the lithium-sulfur cell in accordance with Example 5 Cell Component: Weight g Share% Lithium 0.00551 5.3 Sulfur 0.00715 69 Binder material 0.00204 2 Carbon 0.00102 one Substrate (+) 0.01021 9.8 Separator 0.00613 5.8 Electrolyte 0.07207 69.2 Total cell weight 0.10413 100.0

Table 8. The parameters of the lithium-sulfur cell in accordance with Example 6 The total amount of electrolyte, ml 0.052 The amount of electrolyte per 1 g of sulfur, ml 7.2 The amount of electrolyte per 1 mAh capacity of the positive electrode, ml / mAh 0.0043 The estimated concentration of lithium polysulfide in the electrolyte after the 1st stage, mol / liter 4.344 Specific Energy, Wh / kg 193 Energy density, Wh / l 242

Example 6

A lithium-sulfur cell was assembled similarly to that described in Example 2, except that 69 microliters of electrolyte were deposited on the positive electrode and 3 microliters of electrolyte were deposited on the separator. The total electrolyte content in the galvanic cell is 72 microliters, which gives 7.2 ml of electrolyte per 1 g of sulfur. The cyclic tests of the galvanic cell were carried out as described in Example 2. The parameters of the galvanic cell are shown in Tables 9 and 10.

Table 9. Mass distribution between the components of the lithium-sulfur cell in accordance with Example 6 Cell Component: Weight g Share% Lithium 0.00551 4.2 Sulfur 0.00715 5.5 Binder material 0.00204 1.5 Carbon 0.00102 0.8 Substrate (+) 0.01021 7.7 Separator 0.00613 4.6 Electrolyte 0.1001 75.7 Total cell weight 0.13216 100.0

Table 10. The parameters of the lithium-sulfur cell in accordance with Example 6 The total amount of electrolyte, ml 0.072 The amount of electrolyte per 1 g of sulfur, ml 10 The amount of electrolyte per 1 mAh capacity of the positive electrode, ml / mAh 0.006 The estimated concentration of lithium polysulfide in the electrolyte after the 1st stage, mol / liter 3.128 Specific Energy, Wh / kg 162 Energy density, Wh / l 207

Example 7

The final solubility or saturation solubility of sulfur in the form of lithium octasulfate in a 1.0 M solution of lithium trifluoromethanesulfonate in sulfolane was evaluated. The solubility was evaluated as follows: 1.0 g of a mixture of lithium sulfide and sulfur (with a sulfur content of 0.86 g in a mixture) with a molar ratio of 1: 7 was placed in a sealed glass reactor in an air thermostat, and the specified reactor was equipped with a mechanical mixer and a measuring device. The temperature of the thermostat was raised to 30 ° C. A 1.0 M solution of lithium trifluoromethanesulfonate in sulfolane was added in small portions to the reactor with constant stirring. After adding each new portion, the reaction mixture was thoroughly mixed for 5-6 hours, so as to establish thermodynamic equilibrium. The solubility of the solid phase was evaluated visually. If the reaction mixture contained some solid phase residues, then an additional portion of the electrolyte was added. The experiment was carried out until the solid phase was completely dissolved. The results show that 1.0 g of a mixture of lithium sulfide and sulfur at a molar ratio of 1: 7 is completely dissolved in 3.3 ml of an electrolyte solution; in other words, it was found that the solubility of sulfur in the form of lithium octosulfide is about 0.96 M / liter of electrolyte.

Example 8

The results of Examples 2-7 are summarized in the drawing, which shows the dependence of the specific energy of the bare lithium-sulfur cell on the ratio of electrolyte to sulfur. You can see that this dependence has a maximum that is achieved with an electrolyte to sulfur ratio of about 3. In other words, the maximum capacity of a lithium-sulfur cell is achieved with a volume-weight ratio of electrolyte to sulfur, which is close to the final solubility or saturation solubility of lithium octosulfide in electrolyte.

The presence of a maximum is explained by the fact that at low ratios of the electrolyte to sulfur, the sulfur utilization efficiency is low, while at higher ratios the excess electrolyte creates an additional mass of the galvanic cell, resulting in a decrease in specific energy.

Claims (4)

1. A rechargeable chemical source of electrical energy that contains a positive electrode (cathode) containing sulfur or sulfur-based organic compounds, sulfur-based polymeric compounds or sulfur-based inorganic compounds as a depolarizer, a negative electrode (anode) made of lithium metal or from lithium-containing alloys, and an electrolyte containing a solution of at least one salt in at least one aprotic solvent, wherein a chemical source of electrical energy produces soluble polysulfides in the electrolyte during the first stage of the two-stage discharge process, characterized in that the amount of sulfur in the depolarizer and the volume of the electrolyte are selected so that after the first stage of cathode discharge the concentration of soluble lithium polysulfides in the electrolyte is at least 70% of the saturation concentration of lithium polysulfides in electrolyte. 2. The electric energy source according to claim 1, wherein the amount of sulfur in the depolarizer and the volume of the electrolyte are selected so that after the cathode is completely discharged, the concentration of soluble lithium polysulfides in the electrolyte is from 70 to 90% of the saturation concentration of lithium polysulfides in the electrolyte. 3. The electric energy source according to claim 1, wherein the depolarizer contains sulfur, carbon black and polyethylene oxide. 4. The electric energy source according to one of claims 1 to 3, in which the electrolyte contains a solution of one or more lithium salts selected from the group consisting of lithium trifluoromethanesulfonate, lithium perchlorate, lithium trifluoromethanesulfonimide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrachloroaluminate, lithium tetraalkylammonium, lithium chloride, lithium bromide and lithium iodide; in one or more solvents selected from the group consisting of dioxolane, tetrahydrofuran, dimethoxyethane, diglyme, triglyme, tetrahlim, dialkyl carbonates, sulfolane and butyrolactone.