Electrolyte for lithium-sulfur battery and lithium-sulfur battery including the same

Abstract

The present invention relates to an electrolyte for a lithium-sulfur battery and a lithium-sulfur battery including the same, the electrolyte for the lithium-sulfur battery comprising a lithium salt and a non-aqueous solvent, the non-aqueous solvent comprising a glycol ether, a cyclic ether, and an acyclic ether represented by the following Chemical Formula 1, the acyclic ether being included in an amount of 15% by volume or less based on a total volume of the non-aqueous solvent, and a ratio of a total volume of the glycol ether to a total volume of the acyclic ether being 5 or more: [Chemical formula 1] R 1 -OR 2 (In the above chemical formula 1, R 1 is an unsubstituted or substituted C1-C3 alkyl group, R 2 is unsubstituted or substituted C3-C 20 is an alkyl group of the formula:

Description

[Technical Field]

[0001] The present invention relates to an electrolyte for a lithium-sulfur battery and a lithium-sulfur battery including the same.

[0002] This application claims priority based on Korean Patent Application No. 2022-0110382, filed on August 31, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings thereof. [Background technology]

[0003] A lithium-sulfur battery is a battery system that uses a sulfur-based material with a sulfur-sulfur bond (SS bond) as the positive electrode active material and lithium metal as the negative electrode active material. Sulfur, the main material of the positive electrode active material, is abundant worldwide and has the advantages of being non-toxic and having a low atomic weight.

[0004] As the application areas of secondary batteries expand to electric vehicles (EVs) and energy storage systems (ESSs), lithium-sulfur battery technology is gaining attention as it can theoretically achieve a higher weight energy density (up to 2,600Wh / kg) compared to lithium-ion secondary batteries, which have a relatively low weight energy density (up to 250Wh / kg).

[0005] During discharge, lithium-sulfur batteries release electrons, oxidizing the negative electrode active material (lithium) and ionizing it into lithium cations. The positive electrode active material (sulfur-based material) then accepts electrons and is reduced. The sulfur-based material then accepts two electrons through a reduction reaction, converting the S-S bond into sulfur anions. The lithium cations generated by the oxidation of lithium are transported to the positive electrode via the electrolyte, where they combine with sulfur anions generated by the reduction of sulfur-based compounds to form salts. Specifically, sulfur, which has a cyclic S structure before discharge, is converted to lithium polysulfide (LiSx) through a reduction reaction, and is then completely converted to lithium sulfide (LiS).

[0006] In this case, in the case of sulfur-based compounds, which are cathode active materials, it is difficult to ensure reactivity with electrons and lithium ions in the solid phase due to the low electrical conductivity of sulfur. Therefore, in order to improve the reactivity of sulfur in lithium-sulfur batteries, Li2S x A technology has been developed to improve reactivity by generating intermediate polysulfides in the form of sulfur to induce a liquid reaction. This technology uses ether solvents such as dixoxlane and dimethoxyethane (DME), which have high solubility in lithium polysulfides, as the electrolyte solvent. This affects the reactivity of sulfur and the battery life depending on the content of sulfur in the electrolyte.

[0007] Meanwhile, in recent years, much research and development has been done on lithium-sulfur secondary batteries capable of low-temperature operation, which is required for aircraft and next-generation electric vehicles, etc. However, in lithium-sulfur secondary batteries, polysulfide (PS) elutes from the positive electrode, which increases the material resistance of the electrolyte, making it difficult to operate at low temperatures.

[0008] In essence, lithium-sulfur (Li-S) batteries operate through a solid-to-liquid reaction during the first discharge (up to 2.3 V), in which the active material dissolves from the cathode in the form of PS. Then, during the second discharge (up to 2.1 V), a liquid-to-solid reaction occurs in which the dissolved PS is re-distributed to the cathode. Under this operating principle, the most PS is dissolved into the electrolyte at the end of the first discharge (State of Charge (SOC) = 70) when the solid-to-liquid reaction is complete. This is when the greatest overvoltage occurs in lithium-sulfur batteries. When operated at low temperatures, the overvoltage is particularly large at SOC 70, when the most PS is dissolved into the electrolyte due to poor physical properties, such as viscosity, caused by low temperature operation, making low-temperature operation of lithium-sulfur batteries difficult.

[0009] Furthermore, when using ether-based solvents, which have been developed in the past, as electrolytes for lithium-sulfur batteries, the use of ether-based solvents with low boiling points (bp) can generate gas inside the battery when the lithium-sulfur battery is operated at low temperatures, which can pose a risk of explosion.

[0010] For this reason, there is currently a strong demand for the development of a lithium-sulfur battery that not only controls the elution characteristics of polysulfides from the positive electrode and thereby controls the material resistance of the electrolyte, but also ensures stability during low-temperature operation. Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, an object of the present invention is to provide an electrolyte for a lithium-sulfur battery that solves the above-mentioned problems and has improved resistance characteristics by controlling the elution characteristics of polysulfide (PS) from the positive electrode.

[0012] In particular, the object is to provide a lithium-sulfur battery in which the elution of polysulfides is suppressed from the initial discharge stage of the battery, thereby improving the overvoltage phenomenon, and the electrolyte resistance characteristics are improved, thereby solving the problem of reduced reactivity and improving the output characteristics.

[0013] The object of the present invention is to provide a lithium-sulfur battery that can be stably operated at low temperatures. [Means for solving the problem]

[0014] In order to solve the above problems, according to one aspect of the present invention, there is provided an electrolyte for a lithium-sulfur battery having the following features.

[0015] An electrolyte for a lithium-sulfur battery according to a first aspect includes a lithium salt and a non-aqueous solvent, the non-aqueous solvent including a glycol ether, a cyclic ether, and an acyclic ether represented by the following Chemical Formula 1, the acyclic ether being contained in an amount of 15% by volume or less based on the total volume of the non-aqueous solvent, and the ratio of the total volume of the glycol ethers to the total volume of the acyclic ethers being 5% or more.

[0016] [Chemical formula 1] R 1 -OR 2 (In the above chemical formula 1, R 1 is an unsubstituted or substituted C1-C3 alkyl group, and R 2 is unsubstituted or substituted C3-C 20 is an alkyl group of the formula: According to a second aspect, the electrolyte for a lithium-sulfur battery according to the first aspect may be one in which the acyclic ether is contained in an amount of 10% by volume or less based on the total volume of the non-aqueous solvent.

[0017] According to a third aspect, the electrolyte for a lithium-sulfur battery may be the electrolyte for a lithium-sulfur battery according to the first or second aspect, in which the ratio of the total volume of the glycol ether to the total volume of the acyclic ether is 6.5 or more.

[0018] According to a fourth aspect, the electrolyte for a lithium-sulfur battery may be the one described in any one of the first to third aspects, in which the acyclic ether is contained in an amount of 10% by volume or less based on the total volume of the non-aqueous solvent, and the ratio of the total volume of the glycol ether to the total volume of the acyclic ether is 6.5 or more.

[0019] According to a fifth aspect, the electrolyte for a lithium-sulfur battery may be the electrolyte for a lithium-sulfur battery according to any one of the first to fourth aspects, in which the content of the glycol ether is 65% by volume or more and the sum of the contents of the cyclic ether and the acyclic ether is 35% by volume or less in the total volume of the non-aqueous solvent.

[0020] According to a sixth aspect, the acyclic ether may be methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl t-butyl ether, methyl hexyl ether, ethyl t-butyl ether, ethyl hexyl ether, or the electrolyte for a lithium-sulfur battery according to any one of the first to fifth aspects, which includes two or more of these.

[0021] According to a seventh aspect, the R 1 is an unsubstituted or substituted C1-C2 alkyl group, and the R 2 is unsubstituted or substituted C4-C 10 The electrolyte for a lithium-sulfur battery according to any one of the first to sixth aspects may be an electrolyte for a lithium-sulfur battery according to any one of the first to sixth aspects, wherein the alkyl group is

[0022] According to an eighth aspect, the electrolyte for a lithium-sulfur battery according to any one of the first to seventh aspects may include the acyclic ether, ethyl propyl ether, methyl t-butyl ether, methyl hexyl ether, or a mixture of two or more thereof.

[0023] According to a ninth aspect, the glycol ether may be dimethoxyethane, diethoxyethane, ethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol methyl ethyl ether, or the electrolyte for a lithium-sulfur battery according to any one of the first to eighth aspects, which includes two or more of these.

[0024] According to a tenth aspect, the cyclic ether may be furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzofuran, 2-(2-nitrovinyl)furan, thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, 2,5-dimethylthiophene, or an electrolyte for a lithium-sulfur battery according to any one of the first to ninth aspects, including two or more thereof.

[0025] According to an eleventh embodiment, the lithium salt is LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10, LiPF6, LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, (C2F5SO2)2NLi, (SO2F)2NLi, (CF3SO2)3CLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide, or an electrolyte for a lithium-sulfur battery according to any one of the first to tenth aspects, comprising two or more of these. According to another aspect of the present invention, there is provided a lithium-sulfur battery having the following configuration.

[0026] According to a twelfth aspect, a lithium-sulfur battery includes the electrolyte for a lithium-sulfur battery according to any one of the first to eleventh aspects, a positive electrode including a positive electrode active material, and a negative electrode including a negative electrode active material.

[0027] According to a thirteenth aspect, the lithium-sulfur battery may be the lithium-sulfur battery according to the twelfth aspect, wherein the positive electrode active material includes elemental sulfur, a sulfur compound, or a mixture thereof.

[0028] According to a fourteenth aspect, the positive electrode active material is selected from the group consisting of inorganic sulfur (S), LiSn (n≧1), disulfide compounds, organic sulfur compounds, and carbon-sulfur polymers (C2S x ) n , x is an integer of 2.5 to 50, and n≧2), or a mixture of two or more thereof.

[0029] According to a fifteenth aspect, the lithium-sulfur battery may be the lithium-sulfur battery according to any one of the twelfth to fourteenth aspects, wherein the negative electrode active material includes lithium metal, a lithium alloy, or a mixture thereof. [Effects of the Invention]

[0030] The electrolyte for a lithium-sulfur battery according to one embodiment of the present invention has the effect of suppressing the elution of polysulfide (PS) from the positive electrode.

[0031] As a result, the lithium-sulfur battery according to one embodiment of the present invention has the effect of preventing overvoltage at the initial discharge end (SOC70) during operation, improving reactivity, and improving output characteristics.

[0032] Furthermore, a lithium-sulfur battery using the electrolyte for a lithium-sulfur battery according to one embodiment of the present invention has the effect of being stably operated even at low temperatures and having improved cycle characteristics.

[0033] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further understand the technical concepts of the present invention as well as the content of the invention, and therefore the present invention should not be interpreted as being limited to only the matters described in the drawings. [Brief explanation of the drawings]

[0034] [Figure 1a] 1 is a graph showing the results of evaluating the room temperature driving characteristics of a battery according to an experimental example in this specification. [Figure 1b] 1 is a graph showing the results of evaluating the low-temperature driving characteristics of a battery according to an experimental example in this specification. [Figure 2] 1 is a graph showing the results of evaluating the room temperature and low temperature driving characteristics of a battery according to an experimental example in this specification. [Figure 3] 1 is a graph showing the results of evaluating the life characteristics of a battery after repeated charge / discharge cycles according to an experimental example in this specification. [Figure 4] 1 is a graph showing the results of evaluating the room temperature driving characteristics of a battery according to an experimental example in this specification. [Figure 5] 1 is a graph showing the results of evaluating the room temperature and low temperature driving characteristics of a battery according to an experimental example in this specification. [Figure 6a] 1 is a graph showing the results of evaluating the life characteristics of a battery after repeated charge / discharge cycles according to an experimental example in this specification. [Figure 6b] 1 is a graph showing the results of evaluating the life characteristics of a battery after repeated charge / discharge cycles according to an experimental example in this specification. [Figure 7] 1 is a graph showing the results of evaluating the room temperature and low temperature driving characteristics of a battery according to an experimental example in this specification. [Figure 8] 1 is a graph showing the results of evaluating the life characteristics of a battery according to an experimental example in this specification after repeated cycles at low temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will be described in detail below. However, the present invention is not limited to the following content, and each component may be variously modified or selectively combined as needed. Therefore, it should be understood that the present invention includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention.

[0036] In this specification, when a certain component is said to "comprise" another component, this does not mean that it may further include other components, unless otherwise specified.

[0037] The terminology "polysulfide (PS)" used in this specification means "polysulfide ion (S x 2- , x=8, 6, 4, 2)) and Lithium Polysulfide (Li2S x or LiS x - , x=8, 6, 4, 2).

[0038] In this specification, the term "low temperature" used in connection with low temperature operation of a lithium-sulfur battery may refer to a temperature range of, for example, -15°C to 15°C, specifically, -10°C to 10°C. It will be obvious to those skilled in the art that the term "low temperature operation" is used merely to explain that the electrolyte for a lithium-sulfur battery according to the present invention and a lithium-sulfur battery including the same can exhibit excellent properties even when operated at low temperatures, and is not intended to limit the operating temperature of the electrolyte for a lithium-sulfur battery and the lithium-sulfur battery according to the present invention.

[0039] An electrolyte for a lithium-sulfur battery according to one aspect of the present invention includes a lithium salt and a non-aqueous solvent, the non-aqueous solvent including a glycol ether, a cyclic ether, and an acyclic ether represented by the following Chemical Formula 1. The acyclic ether is included in an amount of 15% by volume or less based on the total volume of the non-aqueous solvent, and the ratio of the total volume of the glycol ether to the total volume of the acyclic ether is 5% or more.

[0040] [Chemical formula 1] R 1 -OR 2 (In the above chemical formula 1, R 1 is an unsubstituted or substituted C1-C3 alkyl group, and R 2 is unsubstituted or substituted C3-C 20 is an alkyl group of the formula: The lithium salt is contained as an electrolyte salt in an electrolyte for a lithium-sulfur battery, and the non-aqueous solvent is contained as a medium in the electrolyte for a lithium-sulfur battery.

[0041] According to the present invention, by using a combination of three types of ethers as the non-aqueous solvent, namely, a glycol ether containing two oxygen atoms, a cyclic ether containing at least one oxygen atom (O) or sulfur atom (S) in the ring structure, and the acyclic ether represented by the above Chemical Formula 1, it is possible to provide an electrolyte that enables a lithium-sulfur battery to operate stably at low temperatures, but the mechanism of the present invention is not limited thereto.

[0042] If an electrolyte for a lithium-sulfur battery does not contain the acyclic ether as a non-aqueous solvent and contains only the glycol ether and the cyclic ether, there is a problem that an overvoltage occurs at SOC70 when the battery using the electrolyte is operated at low temperatures. Therefore, according to one aspect of the present invention, an acyclic ether is contained as a non-aqueous solvent.

[0043] Specifically, when the acyclic ether is contained in a content higher than the total volume of the non-aqueous solvent, the rate of decrease in the lifespan of a battery using the non-aqueous solvent increases rapidly during low-temperature operation due to repeated charge-discharge cycles. Therefore, the acyclic ether is contained in an amount of 15% by volume or less based on the total volume of the non-aqueous solvent.

[0044] In this specification, the content of each component in the non-aqueous solvent may be measured according to a known component analysis method such as nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), ultraviolet / visible spectroscopy (UV-VIS), mass spectroscopy (MS), gas chromatography, etc., and is not particularly limited to the measurement method.

[0045] In one embodiment of the present invention, the acyclic ether may be contained in an amount of 10% by volume or less based on the total volume of the non-aqueous solvent. Specifically, the amount of the acyclic ether may be 1% by volume or more and 15% by volume or less, or 5% by volume or more and 10% by volume or less based on the total volume of the non-aqueous solvent.

[0046] More specifically, when the non-cyclic ether is contained in the non-aqueous solvent in a content higher than the volume of the glycol ether, there is a problem that an overvoltage occurs at SOC70 when a battery using the non-aqueous solvent is operated at low temperature. Therefore, the ratio of the total volume of the glycol ether to the total volume of the non-cyclic ether is set to 5 or more.

[0047] In one embodiment of the present invention, the ratio of the total volume of the glycol ethers to the total volume of the acyclic ethers may be 5.5 or more. Specifically, the ratio of the total volume of the glycol ethers to the total volume of the acyclic ethers may be 6 or more, 6.5 or more, 7 or more, 7.5 or more, or 8 or more. More specifically, the ratio of the total volume of the glycol ethers to the total volume of the acyclic ethers may be, for example, 5 to 15, 5 to 13, 5 to 10, 6 to 10, 6.5 to 10, 7 to 10, or 8 to 10.

[0048] In another embodiment of the present invention, the acyclic ether may be contained in an amount of 10% by volume or less based on the total volume of the non-aqueous solvent, and the ratio of the total volume of the glycol ether to the total volume of the acyclic ether may be 6.5 or more.

[0049] In one embodiment of the present invention, the glycol ether may be 65% by volume or more of the total volume of the non-aqueous solvent, and the sum of the contents of the cyclic ether and the acyclic ether may be 35% by volume or less.

[0050] Specifically, the content of the acyclic ether in the total volume of the non-aqueous solvent may be 25% by volume or less.

[0051] More specifically, the content of the glycol ether may be 65% by volume or more, and the sum of the contents of the cyclic ether and the acyclic ether may be 35% by volume or less, based on the total volume of the non-aqueous solvent.

[0052] In another embodiment of the present invention, the content of the glycol ether may be 70% by volume or more, and the sum of the contents of the cyclic ether and the acyclic ether may be 30% by volume or less, based on the total volume of the non-aqueous solvent.

[0053] In another embodiment of the present invention, the content of the glycol ether in the total volume of the non-aqueous solvent may be 65% by volume to 84% by volume, and the sum of the contents of the cyclic ether and the acyclic ether may be 16% by volume to 25% by volume or less.

[0054] In yet another embodiment of the present invention, the content of the glycol ether in the total volume of the non-aqueous solvent may be 70% by volume to 80% by volume, and the sum of the contents of the cyclic ether and the acyclic ether may be 20% by volume to 30% by volume.

[0055] In another embodiment of the present invention, the content of the glycol ether in the total volume of the non-aqueous solvent may be 75% by volume to 80% by volume, and the sum of the contents of the cyclic ether and the acyclic ether may be 20% by volume to 25% by volume.

[0056] In one aspect of the present invention, when the content of the above-mentioned solvent in the total volume of the non-aqueous solvent is within the above-mentioned range, advantageous effects can be exhibited in terms of suppressing elution of polysulfide and the overall boiling point of the non-aqueous solvent, but the present invention is not limited thereto.

[0057] In one embodiment of the present invention, the R 1 Specifically, may be an unsubstituted or substituted methyl group, an unsubstituted or substituted ethyl group, or an unsubstituted or substituted propyl group. In this case, the substituent contained in the substituted methyl group, substituted ethyl group, or substituted propyl group is not limited to these, but may be, for example, a halogen atom, a hydroxy group, a nitro group, a cyano group, an amino group, an amidino group, an acetamino group, hydrazine, hydrazizone, a carboxyl group, a sulfonyl group, a sulfamoyl group, a sulfonic acid group, a phosphoric acid group, or a combination thereof.

[0058] In another embodiment of the present invention, the R 1 Specifically, R may be an unsubstituted methyl group, an unsubstituted ethyl group, or an unsubstituted propyl group. The present invention is not limited to these, but for example, from the viewpoint of suppressing side reactions with polysulfide or lithium during battery operation, R 1 is preferably an unsubstituted alkyl group.

[0059] In one embodiment of the present invention, the R 2 Specifically, substituted or unsubstituted C3 to C 20 In this case, the alkyl group may be substituted with C3 to C 20 The substituents contained in the alkyl group are not limited to these, but examples thereof include a halogen atom, a hydroxy group, a nitro group, a cyano group, an amino group, an amidino group, an acetamino group, hydrazine, hydrazizone, a carboxyl group, a sulfonyl group, a sulfamoyl group, a sulfonic acid group, phosphoric acid, a C1 to C5 alkyl group, a C1 to C5 alkoxy group, a C2 to C5 alkenyl group, a C2 to C5 alkynyl group, a C4 to C 10 Cycloalkyl groups of C6-C 10 Aryl groups, C6-C 10 Heteroaryl groups of C6-C 20 Aryl alkyl groups, C6-C 20 heteroarylalkyl groups, or combinations thereof.

[0060] In another embodiment of the present invention, the R 2is not limited to these, and examples thereof include an n-propyl group, an n-butyl group, an n-amyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-eicosanyl group, an is o-propyl group, sec-butyl group, iso-butyl group, tert-butyl group, 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, iso-amyl group, neopentyl group, 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, tert-amyl group, 1,3-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, 2-ethyl-2-methylpropyl group, linear or branched The alkyl group may be a branched heptyl group, 1-methylheptyl group, 2-ethylhexyl group, 1,5-dimethylhexyl group, tert-octyl group, branched nonyl group, branched decyl group, branched undecyl group, branched dodecyl group, branched tridecyl group, branched tetradecyl group, branched pentadecyl group, branched hexadecyl group, branched heptadecyl group, branched octadecyl group, linear or branched nonadecyl group, linear or branched eicosanyl group, cyclopropyl group, cyclopropylmethyl group, cyclobutyl group, cyclobutylmethyl group, cyclopentyl group, cyclohexyl group, cyclohexylmethyl group, cycloheptyl group, cyclooctyl group, cyclohexylpropyl group, cyclododecyl group, norbornyl group, bornyl group, cyclopentylethyl group, bicyclooctyl group, or a combination thereof.

[0061] In another aspect of the present invention, the present invention is not limited thereto, but for example, from the viewpoint of suppressing side reactions with polysulfide or lithium during battery operation, R 2 is preferably an unsubstituted alkyl group.

[0062] In one embodiment of the present invention, the acyclic ether may include, for example, methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl t-butyl ether, methyl hexyl ether, ethyl t-butyl ether, ethyl hexyl ether, or two or more thereof.

[0063] In another embodiment of the present invention, the R 1 Specifically, R is an unsubstituted or substituted C1-C2 alkyl group, 2 Specifically, unsubstituted or substituted C4-C 10 More specifically, the R 1 is an unsubstituted C1-C2 alkyl group, and the R 2 is unsubstituted C4-C 10 The alkyl group may be:

[0064] In one embodiment of the present invention, the acyclic ether may include ethyl propyl ether, methyl t-butyl ether, methyl hexyl ether, or two or more thereof.

[0065] In still another embodiment of the present invention, the acyclic ether may be methylhexyl ether alone.

[0066] In one aspect of the present invention, the above-mentioned acyclic ethers act as non-solvents for polysulfides eluted from the positive electrode, thereby exhibiting an advantageous effect in terms of suppressing elution of polysulfides from the positive electrode. Furthermore, the acyclic ethers exhibit an advantageous effect in terms of boiling point characteristics for low-temperature operation of lithium-sulfur batteries, but the mechanism of the present invention is not limited thereto.

[0067] In one embodiment of the present invention, the boiling point (bp) of the acyclic ether is preferably higher than the operating temperature of a battery using the lithium-sulfur battery electrolyte. For example, the boiling point of the acyclic ether may be 55°C or higher. Specifically, the boiling point of the acyclic ether may be 55°C or higher and 130°C or lower, 55°C or higher and 110°C or lower, 55°C or higher and 100°C or lower, 55°C or higher and 85°C or lower, 55°C or higher and 80°C or lower, 60°C or higher and 75°C or lower, or 60°C or higher and 70°C or lower, but is not limited thereto. The boiling point is measured at 25°C and 1 atmosphere.

[0068] The glycol ether is an acyclic ether containing two oxygen atoms and can be used without any particular limitation as long as it can be used as an electrolyte for lithium-sulfur batteries.

[0069] In one embodiment of the present invention, the glycol ether may be represented by the following formula 2: [Chemical formula 2] R 3 -O-(CH2CH2O) y -R 4 (In the above chemical formula 2 R 3 and R 4 are the same or different and each independently represent a C1 to C6 unsubstituted or substituted alkyl group, or a C6 to C 12 or an unsubstituted or substituted aryl group of C7 to C 13 wherein x is an integer of 1 to 4, and y is an integer of 0 to 4.

[0070] The glycol ether may include, for example, dimethoxyethane, diethoxyethane, ethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol methyl ethyl ether, or two or more thereof, but is not limited thereto.

[0071] The cyclic ether is an ether containing at least one oxygen atom (O) or sulfur atom (S) in the ring structure and at least one -C-O-C- or -C-S- structure in the ring structure, and can be used without particular limitation as long as it is usable as an electrolyte for lithium-sulfur batteries. The cyclic ether may include, for example, furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzofuran, 2-(2-nitrovinyl)furan, thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, 2,5-dimethylthiophene, or two or more thereof, but is not limited thereto.

[0072] The lithium salt can be used without any particular limitation as long as it can be used as an electrolyte for a lithium-sulfur battery. Examples of the lithium salt include LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10, LiPF6, LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, (C2F5SO2)2NLi, (SO2F)2NLi, (CF3SO2)3CLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide, or two or more thereof, but are not limited thereto.

[0073] In one embodiment of the present invention, the lithium salt may not include lithium nitrate salts, which may be included as examples of nitric acid or nitrite compounds described below.

[0074] In one embodiment of the present invention, the lithium salt may include lithium bis(fluorosulfonyl)imide (LiFSI).

[0075] In one embodiment of the present invention, the concentration of the lithium salt can be appropriately determined in consideration of ionic conductivity, solubility, etc., and may be, for example, 0.1 to 4.0 M, 0.5 to 2.0 M, 0.5 to 1.0 M, or 0.75 M. When the concentration of the lithium salt is within the above-mentioned ranges, advantageous effects can be exhibited in terms of ionic conductivity and electrolyte viscosity, but the concentration is not limited thereto.

[0076] In one embodiment of the present invention, the non-aqueous solvent may contain dimethoxyethane as a glycol ether, 2-methylfuran as a cyclic ether, and ethyl propyl ether as an acyclic ether, specifically, the non-aqueous solvent may contain dimethoxyethane, 2-methylfuran, and ethyl propyl ether in a volume ratio of 65-85:1-20:1-15.

[0077] In another embodiment of the present invention, the non-aqueous solvent may contain dimethoxyethane, 2-methyl-tetrahydrofuran, and methyl t-butyl ether in a volume ratio of 65-85:1-20:1-15.

[0078] In another embodiment of the present invention, the non-aqueous solvent may contain dimethoxyethane, 2-methylfuran, and hexyl methyl ether in a volume ratio of 65-85:1-20:1-15.

[0079] In one aspect of the present invention, the electrolyte for the lithium-sulfur battery may further include a nitric acid or nitrite-based compound in addition to the above-mentioned composition. The nitric acid or nitrite-based compound may form a stable film on a negative electrode made of, for example, lithium metal, and thereby improve charge / discharge efficiency, but the mechanism of the present invention is not limited thereto.

[0080] The nitric acid or nitrite compound is not particularly limited in the present invention, and may be, for example, an inorganic nitric acid or nitrite compound such as lithium nitrate (LiNO3), potassium nitrate (KNO3), cesium nitrate (CsNO3), barium nitrate (Ba(NO3)2), ammonium nitrate (NH4NO3), lithium nitrite (LiNO2), potassium nitrite (KNO2), cesium nitrite (CsNO2), or ammonium nitrite (NH4NO2); an organic nitric acid or nitrite compound such as methyl nitrate, dialkylimidazolium nitrate, guanidine nitrate, imidazolium nitrate, pyridinium nitrate, ethyl nitrite, propyl nitrite, butyl nitrite, pentyl nitrite, or octyl nitrite; or an organic nitro compound such as nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitropyridine, dinitropyridine, nitrotoluene, or dinitrotoluene, or a mixture of two or more thereof.

[0081] In one embodiment of the present invention, the electrolyte for the lithium-sulfur battery may further include lithium nitrate (LiNO3).

[0082] In another embodiment of the present invention, the electrolyte for the lithium-sulfur battery may further contain, in addition to the above-described composition, other additives for improving charge / discharge characteristics, flame retardancy, etc. The additives are not particularly limited in the present invention, but examples thereof include pyridine, triethyl phosphite, triethanolamine, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, fluoroethylene carbonate (FEC), propene sultone (PRS), and vinylene carbonate (VC).

[0083] The electrolyte for a lithium-sulfur battery according to one aspect of the present invention can be prepared by a conventional method known in the art, and the present invention is not particularly limited thereto.

[0084] According to another aspect of the present invention, there is provided a lithium-sulfur battery including the above-described electrolyte for lithium-sulfur batteries, a positive electrode including a positive electrode active material, and a negative electrode including a negative electrode active material.

[0085] The positive electrode, positive electrode active material, negative electrode, and negative electrode active material can be any material that can be used in a lithium-sulfur battery without any particular limitation, as long as the object of the present invention is not impaired.

[0086] For example, the positive electrode may include a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, and the negative electrode may include a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, In this case, the positive electrode current collector is not particularly limited as long as it supports the positive electrode active material, does not cause chemical changes in the battery, and has high conductivity, and the negative electrode current collector is not particularly limited as long as it supports the negative electrode active material, does not cause chemical changes in the battery, and has high conductivity.

[0087] In one embodiment of the present invention, the positive electrode active material may include, for example, elemental sulfur, a sulfur compound, or a mixture thereof. Specifically, the positive electrode active material may include inorganic sulfur (S), LiS, n (n≧1), disulfide compounds, organic sulfur compounds, carbon-sulfur polymers (C2S x ) n , x=2.5 to 50, n≧2), or two or more of these may be included.

[0088] In one embodiment of the present invention, the negative electrode active material is lithium (Li + Any material capable of reversibly intercalating or deintercalating lithium ions or capable of reacting with lithium ions to reversibly form a lithium-containing compound may be used without particular limitation. For example, the negative electrode active material may include lithium metal, a lithium alloy, or a mixture thereof. The lithium alloy may be, for example, lithium (Li) and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), tin (Sn), or an alloy of two or more of these metals.

[0089] In addition, each of the positive electrode active material layer and the negative electrode active material layer may further include a conductive material, a binder, an additive, and the like in addition to the active material. Specific types of the conductive material, binder, and additives may be conventionally used, and therefore, the description thereof will be omitted.

[0090] The present invention will be described in more detail below with reference to examples. However, the following examples are merely for the purpose of illustrating the present invention, and the scope of the present invention is not limited to these examples in any way.

[0091] First, a lithium-sulfur battery in the form of a pouch cell was manufactured by the following method.

[0092] Example 1 Fabrication of electrolytes for lithium-sulfur batteries 0.75M lithium bis(fluorosulfonyl)imide (LiFSI) and 5.0 wt% lithium nitrate (LiNO3) were added to dimethoxyethane (DME) and stirred for 12 hours to dissolve, after which 2-methylfuran and ethyl propyl ether were added and stirred to prepare an electrolyte.

[0093] The volume ratio of dimethoxyethane:2-methylfuran:ethyl propyl ether used here was 70:20:10.

[0094] Cathode manufacturing A positive electrode slurry was prepared by mixing a sulfur-carbon complex (S:C=75:25 (weight ratio)) as a positive electrode active material and lithium polyacrylate (LiPAA) as a binder in a weight ratio of 95:5 with distilled water as a solvent.

[0095] The prepared positive electrode slurry composition was applied to both sides of a 12 μm thick aluminum current collector, dried at 80° C., and rolled using a roll press to prepare a positive electrode. At this time, the loading of the positive electrode active material was 4.1 mAh / cm. 2 It was.

[0096] Anode manufacturing Two 30 μm-thick lithium metal sheets were stacked as the negative electrode (total thickness: 60 μm).

[0097] Lithium-sulfur battery manufacturing The fabricated positive and negative electrodes were positioned facing each other, and a 16 μm-thick polyethylene separator with a porosity of 68% was sandwiched between them and stacked to assemble a pouch cell. 1.5 g of the electrolyte fabricated above was then injected into the pouch so that the El / S (Electrolyte / S loading amount) ratio was 2.9 ml / g, and the pouch was sealed to fabricate a pouch-type lithium-sulfur battery. The fabricated battery had a capacity of 0.6 Ah, an energy of 1.29 Wh, and an energy of 401 Wh / kg.

[0098] Example 2 A lithium-sulfur battery was produced in the same manner as in Example 1, except that the volume ratio of dimethoxyethane:2-methylfuran:ethyl propyl ether used in producing the electrolyte was 80:10:10.

[0099] Example 3 A lithium-sulfur battery was produced in the same manner as in Example 1, except that the volume ratio of dimethoxyethane:2-methylfuran:ethyl propyl ether used in producing the electrolyte was 60:30:10.

[0100] Example 4 A lithium-sulfur battery was produced in the same manner as in Example 1, except that ethyl propyl ether was replaced with methyl t-butyl ether during the production of the electrolyte so that the composition of the non-aqueous solvent in the electrolyte was dimethoxyethane:2-methylfuran:methyl t-butyl ether in a volume ratio of 70:20:10.

[0101] Example 5 A lithium-sulfur battery was produced in the same manner as in Example 1, except that ethyl propyl ether was replaced with methyl hexyl ether during the production of the electrolyte so that the composition of the non-aqueous solvent in the electrolyte was dimethoxyethane:2-methylfuran:methyl hexyl ether in a volume ratio of 70:20:10.

[0102] Example 6 A lithium-sulfur battery was produced in the same manner as in Example 1, except that ethyl propyl ether was replaced with dipropyl ether in the production of the electrolyte so that the composition of the non-aqueous solvent in the electrolyte was dimethoxyethane:2-methylfuran:dipropyl ether in a volume ratio of 70:20:10.

[0103] Example 7 A lithium-sulfur battery was produced in the same manner as in Example 1, except that ethyl propyl ether was replaced with ethyl t-butyl ether during the production of the electrolyte so that the composition of the non-aqueous solvent in the electrolyte was dimethoxyethane:2-methylfuran:ethyl t-butyl ether in a volume ratio of 70:20:10.

[0104] Comparative Example 1 A lithium-sulfur battery was produced in the same manner as in Example 1, except that ethyl propyl ether was not used in producing the electrolyte.

[0105] The volume ratio of dimethoxyethane to 2-methylfuran used here was 80:20.

[0106] Comparative Example 2 A lithium-sulfur battery was produced in the same manner as in Comparative Example 1, except that the volume ratio of dimethoxyethane:2-methylfuran in producing the electrolyte was 70:30.

[0107] Comparative Example 3 A lithium-sulfur battery was produced in the same manner as in Example 1, except that 2-methylfuran, which was used in producing the electrolyte, was not used and the volume ratio of dimethoxyethane:ethyl propyl ether was 80:20.

[0108] Comparative Example 4 A lithium-sulfur battery was produced in the same manner as in Example 1, except that the volume ratio of dimethoxyethane:2-methylfuran:ethyl propyl ether used in producing the electrolyte was 70:10:20.

[0109] Comparative Example 5 A lithium-sulfur battery was produced in the same manner as in Comparative Example 4, except that ethyl propyl ether was replaced with methyl t-butyl ether during the production of the electrolyte so that the composition of the non-aqueous solvent of the electrolyte was dimethoxyethane:2-methylfuran:methyl t-butyl ether in a volume ratio of 70:10:20.

[0110] Comparative Example 6 A lithium-sulfur battery was produced in the same manner as in Comparative Example 4, except that ethyl propyl ether was replaced with methyl hexyl ether during the production of the electrolyte so that the composition of the non-aqueous solvent of the electrolyte was dimethoxyethane:2-methylfuran:methyl hexyl ether in a volume ratio of 70:10:20.

[0111] Comparative Example 7 A lithium-sulfur battery was produced in the same manner as in Example 1, except that ethyl propyl ether was replaced with dibutyl ether during the production of the electrolyte so that the composition of the non-aqueous solvent in the electrolyte was dimethoxyethane:2-methylfuran:dibutyl ether in a volume ratio of 70:20:10.

[0112] The compositions of the electrolytes used in the batteries of Examples 1 to 6 and Comparative Examples 1 to 7 are summarized in Table 1 below.

[0113] [Table 1]

[0114] Experimental Example 1: Evaluation of room temperature and low temperature driving characteristics depending on the composition of non-aqueous solvent The batteries of Examples 1 to 3 and Comparative Examples 1, 3, and 4 manufactured above were evaluated by performing a single drive cycle of 0.1 C charge / 0.1 C discharge (upper limit 2.5 V / lower limit 1.8 V, respectively) at temperatures of 25°C and 10°C, respectively. The results are shown in Figures 1a and 1b, respectively.

[0115] Furthermore, the batteries of Examples 1 to 3 and Comparative Examples 1, 3, and 4 manufactured above were driven once at 0.1 C at 25°C, then driven three times each at 0.1 C, 0.2 C, 0.3 C, and 0.5 C at 10°C, and then driven again three times each at 0.2 C, 0.3 C, and 0.5 C at 25°C, and the discharge capacity was evaluated according to the number of cycles. The results are shown in FIG. 2.

[0116] In addition, using the battery for which the high-rate characteristics evaluation shown in Figure 2 was completed, the charge capacity of the battery was evaluated by repeating a 0.3C charge / 0.3C discharge (upper limit 2.5V / lower limit 1.8V) cycle at a temperature of 25°C. The results are shown in Figure 3.

[0117] As is clear from FIG. 1, when an acyclic ether is used as the non-aqueous solvent in the electrolyte during low-temperature operation, the dip region at SOC70 disappears, that is, the overvoltage disappears.

[0118] However, referring to Figures 2 and 3, it was confirmed that Comparative Example 3, in which an acyclic ether was used but no cyclic ether was used, and Comparative Example 4, in which an acyclic ether was used but the amount of glycol ether was in excess so that the amount was less than 5 times the volume of the acyclic ether (glycol ether:acyclic ether = 3.5:1), had poor life characteristics with repeated charge / discharge cycles of the battery.

[0119] Experimental Example 2: Evaluation of room temperature and low temperature driving characteristics according to the composition ratio of non-aqueous solvent and the type of acyclic ether Referring to the results of Experimental Example 1, the volume ratio of glycol ether in the non-aqueous solvent was fixed at 70% by volume, and then the content of acyclic ether or the type of acyclic ether was varied to compare and evaluate the characteristics of operation at room temperature and low temperature.

[0120] Specifically, the batteries of Example 4, Example 5, and Comparative Example 2, Comparative Example 5, and Comparative Example 6 manufactured above were subjected to two cycles of 0.1 C charge / 0.1 C discharge (upper limit 2.5 V / lower limit 1.8 V, respectively) at a temperature of 25°C, and then the charge / discharge characteristics during the third cycle were evaluated. The results are shown in FIG. 4.

[0121] Furthermore, the batteries of Example 4, Example 5, and Comparative Example 2, Comparative Example 5, and Comparative Example 6 were driven once at 0.1 C at 25°C, then driven three times each at 0.1 C, 0.2 C, 0.3 C, and 0.5 C at 10°C, and then driven again three times each at 0.2 C, 0.3 C, and 0.5 C at 25°C, and the discharge capacity was evaluated according to the number of cycles. The results are shown in FIG. 5.

[0122] In addition, using the batteries for which the high-rate performance evaluation shown in Figure 5 was completed, the charge capacity of the batteries was evaluated after repeated cycles of 0.3 C charge / 0.3 C discharge (upper limit 2.5 V / lower limit 1.8 V) at a temperature of 25°C. The results are shown in Figures 6a and 6b. According to the results in Figure 5, Comparative Example 6 was unable to demonstrate its battery performance after 5 cycles, and therefore the results for Comparative Example 6 are not shown in Figures 6a and 6b, which show the evaluation results of battery capacity after 25 cycles.

[0123] 4 to 6a and 6b, Comparative Example 6, in which glycol ether as the acyclic ether was used in a volume ratio of 3.5:1 (glycol ether:methyl hexyl ether) to methyl hexyl ether, showed a 1 st It was confirmed that a large plateau overvoltage occurred and the battery was overcharged. Furthermore, as is clear from the results of Figures 4 to 6 except for Comparative Example 6, although the overvoltage characteristics of the battery can be improved by including an acyclic ether, when an excessive amount of the acyclic ether is included such that the ratio of the volume of the glycol ether to the volume of the acyclic ether is less than 5, the battery life at room temperature was confirmed to be deteriorated.

[0124] Experimental Example 3: Evaluation of room temperature and low temperature driving characteristics according to the type of acyclic ether The electrolytes prepared above had the same volume ratio of glycol ether:cyclic ether:acyclic ether of 7:2:1, but the type of acyclic ether was different for Example 1 (ethyl propyl ether), Example 4 (methyl t-butyl ether), and Example 5 (methyl hexyl ether), and Comparative Example 2 had the same total volume of glycol ether. The batteries were driven once at 0.1 C at 25°C, then three times at 0.1 C, 0.2 C, 0.3 C, and 0.5 C at 10°C, and then three times at 0.2 C, 0.3 C, and 0.5 C at 25°C. The discharge capacity was evaluated as a function of the number of battery cycles. The results are shown in FIG. 7.

[0125] Referring to FIG. 7, it was confirmed that the batteries containing glycol ether:cyclic ether:acyclic ether in a volume ratio of 7:2:1 as a non-aqueous solvent in the electrolyte exhibited excellent low-temperature driving characteristics, and in particular, methyl hexyl ether exhibited the best low-temperature driving characteristics in the order of Example 5 > Example 1 > Example 4.

[0126] Experimental Example 4: Evaluation of room temperature and low temperature driving characteristics according to the type of acyclic ether For the electrolytes prepared above, which contained the same volume ratio of glycol ether:cyclic ether:acyclic ether of 7:2:1, but which contained different types of acyclic ether, Examples 5 (methylhexyl ether), 6 (dipropyl ether), 7 (ethyl t-butyl ether), and Comparative Example 7 (dibutyl ether), the batteries were driven three times at 0.1 C at 25°C, then driven three times at each discharge rate under conditions of 0.1 C-0.2 C-0.3 C-0.5 C at 10°C, and then driven again at 10°C at 0.1 C. The discharge capacity was evaluated as a function of the number of cycles. The results are shown in FIG. 8.

[0127] Referring to FIG. 8, it was confirmed that the acyclic ethers dipropyl ether, ethyl t-butyl ether, and methyl hexyl ether used as non-aqueous solvents in the electrolyte all exhibit excellent low-temperature driving characteristics, whereas dibutyl ether is not suitable for low-temperature driving.

Claims

1. comprising a lithium salt and a non-aqueous solvent, The non-aqueous solvent is The present invention relates to a glycol ether, a cyclic ether, and an acyclic ether represented by the following chemical formula 1: the acyclic ether is contained in an amount of 15% by volume or less based on the total volume of the non-aqueous solvent; An electrolyte for a lithium-sulfur battery, wherein the ratio of the total volume of the glycol ether to the total volume of the acyclic ether is 5 or more: [Chemical formula 1] R １ -O-R ２ (In the above chemical formula 1, R １ is unsubstituted C １ ~C ３ is an alkyl group of the formula R ２ is unsubstituted C ３ ~C ２０ is an alkyl group represented by the formula:

2. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the acyclic ether is contained in an amount of 5% by volume or more and 15% by volume or less based on the total volume of the non-aqueous solvent.

3. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the ratio of the total volume of the glycol ether to the total volume of the acyclic ether is 6.5 or more.

4. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the acyclic ether is contained in an amount of 10% by volume or less based on the total volume of the non-aqueous solvent, and a ratio of the total volume of the glycol ether to the total volume of the acyclic ether is 6.5 or more.

5. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein a content of the glycol ether is 65% by volume or more and a sum of a content of the cyclic ether and acyclic ether is 35% by volume or less in the total volume of the non-aqueous solvent.

6. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the acyclic ether comprises methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl t-butyl ether, methyl hexyl ether, ethyl t-butyl ether, ethyl hexyl ether, or two or more thereof.

7. The R １ is unsubstituted C １ ~C ２ is an alkyl group of the formula The R ２ is unsubstituted C ４ ~C １０ 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the alkyl group is

8. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the acyclic ether comprises ethyl propyl ether, methyl t-butyl ether, methyl hexyl ether, or a mixture of two or more thereof.

9. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the glycol ether comprises dimethoxyethane, diethoxyethane, ethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol methyl ethyl ether, or two or more thereof.

10. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the cyclic ether comprises furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzofuran, 2-(2-nitrovinyl)furan, or two or more thereof.

11. The lithium salts include LiCl, LiBr, LiI, and LiClO. ４ , LiBF ４ , LiB １０ Cl １０ , LiPF ６ , LiCF ３ SO ３ , LiCF ３ CO ２ , LiC ４ BO ８ , LiAsF ６ , LiSbF ６ , LiAlCl ４ , C.H. ３ SO ３ Li, CF ３ SO ３ Li, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ ) ２ NLi, (SO ２ F) ２ NLi, (CF ３ SO ２ ) ３ 2. The electrolyte for a lithium-sulfur battery of claim 1, comprising CLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylborate, lithium imide, or two or more thereof.

12. An electrolyte for a lithium-sulfur battery according to any one of claims 1 to 11; a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; Lithium-sulfur batteries, including:

13. 13. The lithium-sulfur battery of claim 12, wherein the positive electrode active material comprises elemental sulfur, a sulfur compound, or a mixture thereof.

14. The positive electrode active material is inorganic sulfur (S ８ ), Li ２ Sn (n≧1), disulfide compounds, organic sulfur compounds, carbon-sulfur polymers ((C ２ S ｘ ) ｎ , x is an integer from 2.5 to 50, and n≧2), or a mixture of two or more thereof.

15. 13. The lithium-sulfur battery of claim 12, wherein the negative electrode active material comprises lithium metal, a lithium alloy, or a mixture thereof.

16. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the acyclic ether consists solely of methyl propyl ether, ethyl propyl ether, methyl t-butyl ether, methyl hexyl ether, ethyl t-butyl ether, ethyl hexyl ether, or two or more thereof.

17. 2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the acyclic ether compound is methyl hexyl ether or ethyl propyl ether.

Images