Electrolyte for lithium-sulfur battery and lithium-sulfur battery comprising same

Abstract

The present disclosure relates to an electrolyte for a lithium-sulfur battery and a lithium-sulfur battery comprising the same. The electrolyte for a lithium-sulfur battery may include a non-aqueous solvent, a lithium salt, a nitrate, and an aryl derivative, in which the non-aqueous solvent includes: a heterocyclic compound containing one oxygen (O) atom or one sulfur (S) atom in a ring structure; and a glycol ether, and the aryl derivative contains at least one of the compounds represented by the following Chemical Formula 1 to Chemical Formula 4: [Chemical Formula 1] R1-M1-Li [Chemical Formula 2] R2-M2-M3-R3 [Chemical Formula 3] R4-M4-Sx-Li [Chemical Formula 4] R5-M5-Sx-M6-R6.

Description

Technical Field

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

[0002] This application claims priority to Korean Patent Application No. 10-2022-0092802 filed in Korea on July 26, 2022, the disclosure of which is incorporated herein by reference. Background Art

[0003] Lithium-sulfur batteries are battery systems that use a sulfur-sulfur (SS) bonded sulfur-based material as a positive electrode active material and lithium metal as a negative electrode active material. Sulfur, as a main component of the positive electrode active material, has advantages in that it is abundant in resources worldwide, non-toxic, and has a low atomic weight.

[0004] As the application range of secondary batteries expands to electric vehicles (EVs), energy storage systems (ESS), etc., lithium-sulfur battery technology, which can achieve a theoretically higher energy storage density per unit weight (about 2,600Wh / kg) compared with lithium-ion secondary batteries with a relatively low energy storage density per unit weight (about 250Wh / kg), has attracted attention.

[0005] In lithium-sulfur batteries, during discharge, while lithium as the negative electrode active material donates electrons and is ionized and oxidized to lithium cations, the sulfur-based material as the positive electrode active material accepts electrons and is reduced. In this paper, the SS bond accepts two electrons and is converted into the sulfur anion form by the reduction of the sulfur-based material. The lithium cations generated by the oxidation of lithium are transferred to the positive electrode through the electrolyte and combined with the sulfur anions generated by the reduction of the sulfur-based compound to form a salt. In particular, the sulfur before discharge has a cyclic S 8 structure, which is converted into lithium polysulfide (Li 2 S x ) and is completely reduced to produce lithium sulfide (Li 2 S).

[0006] In this paper, sulfur compounds used as positive electrode active materials have difficulty in ensuring reactivity with electrons and lithium ions in their solid state due to the low electrical conductivity of sulfur. Therefore, in order to improve the reactivity of sulfur in lithium-sulfur batteries, a method of generating Li 2 S x The technology of initiating liquid phase reaction and improving reactivity by using intermediate polysulfide in the form of lithium polysulfide. Such technology uses ether solvents such as dioxolane or dimethoxyethane (DME) that have high solubility for lithium polysulfide as electrolyte solvents. As a result, the reactivity of sulfur and battery life are affected by the electrolyte content.

[0007] In addition, during the discharge of lithium-sulfur batteries, polysulfides (PS) generated from the positive electrode are dissolved into the electrolyte and react, but such polysulfides cause side reactions in the battery, leading to battery degradation. In order to achieve a high energy density battery, it is important to reduce the amount of electrolyte. However, when the amount of electrolyte is reduced, the concentration of polysulfides increases, thereby accelerating the side reactions and causing a decrease in battery life. Therefore, it is necessary to achieve high energy density while ensuring a certain amount of electrolyte. Summary of the invention

[0008] Technical issues

[0009] The present disclosure aims to solve the problems of the related art, and thus the present disclosure aims to provide a lithium-sulfur battery with improved discharge capacity.

[0010] To this end, the present disclosure aims to provide an electrolyte for a lithium-sulfur battery that controls the dissolution characteristics of polysulfides by changing the reaction path of sulfur (S), thereby improving problems caused by the dissolution of polysulfides such as resistance characteristics.

[0011] The present disclosure also aims to provide a lithium-sulfur battery that uses an appropriate amount of electrolyte and has high energy density and lifespan characteristics.

[0012] Technical Solution

[0013] In one aspect of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery according to any one of the following embodiments.

[0014] According to a first embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery, comprising a non-aqueous solvent, a lithium salt, a nitrate, and an aryl derivative.

[0015] wherein the non-aqueous solvent comprises: a heterocyclic compound containing an oxygen (O) atom or a sulfur (S) atom in a ring structure; and a glycol ether, and

[0016] The aryl derivative includes at least one of the compounds represented by the following Chemical Formulae 1 to 4:

[0017] [Chemical formula 1]

[0018] R 1 -M 1 -Li

[0019] [Chemical formula 2]

[0020] R 2 -M 2 -M 3 -R 3

[0021] [Chemical formula 3]

[0022] R 4 -M 4 -Sx-Li

[0023] [Chemical formula 4]

[0024] R 5 -M 5 -Sx-M 6 -R 6 ,

[0025] Among them, M 1 、M 2 、M 3 、M 4 、M 5 and M 6 are each independently selected from selenium (Se) and tellurium (Te), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each independently represents a C6-C20 aryl group, and

[0026] X represents a number from 1 to 8.

[0027] According to a second embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in the first embodiment, wherein M in Chemical Formula 1 to Chemical Formula 4 1 、M 2 、M 3 、M 4 、M 5 and M 6 Each represents selenium (Se).

[0028] According to a third embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in the first embodiment or the second embodiment, wherein the nitrate contains an alkali metal as a cation.

[0029] According to a fourth embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in any one of the first to third embodiments, wherein the nitrate comprises lithium nitrate (LiNO 3 ).

[0030] According to a fifth embodiment of the present disclosure, there is provided a lithium-sulfur battery electrolyte as defined in any one of the first to fourth embodiments, wherein the sum of the weight of the nitrate and the weight of the aryl derivative relative to the total weight of the lithium-sulfur battery electrolyte is 4 weight % or more.

[0031] According to a sixth embodiment of the present disclosure, there is provided the electrolyte for a lithium-sulfur battery as defined in any one of the first to fifth embodiments, wherein the weight of the aryl derivative is equal to or less than the weight of the nitrate.

[0032] According to a seventh embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in any one of the first to sixth embodiments, wherein the aryl derivative comprises a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 3, or a mixture thereof, and

[0033] The molar ratio of the compound represented by Chemical Formula 1, the compound represented by Chemical Formula 3, or a mixture thereof to the nitrate is 0.5:1 or less.

[0034] According to an eighth embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in any one of the first to seventh embodiments, wherein the aryl derivative comprises a compound represented by Chemical Formula 2, a compound represented by Chemical Formula 4, or a mixture thereof, and

[0035] The molar ratio of the compound represented by Chemical Formula 2, the compound represented by Chemical Formula 4, or a mixture thereof to the nitrate is 0.2:1 or less.

[0036] According to a ninth embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in any one of the first to eighth embodiments, wherein the lithium salt comprises LiCl, LiBr, LiI, 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 , CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) 2 NLi,(SO2 F) 2 NLi, (CF 3 SO 2 ) 3 CLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide, or two or more thereof.

[0037] According to a tenth embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in any one of the first to ninth embodiments, wherein a ratio of the total volume of the glycol ether to the total volume of the heterocyclic compound is 3:1 or more.

[0038] According to an eleventh embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in any one of the first to tenth embodiments, wherein the heterocyclic compound 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, thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, 2,5-dimethylthiophene, or two or more thereof.

[0039] According to a twelfth embodiment of the present disclosure, there is provided the electrolyte for a lithium-sulfur battery as defined in any one of the first to eleventh embodiments, wherein the nonaqueous solvent further contains an acyclic ether containing one oxygen atom.

[0040] According to a thirteenth embodiment of the present disclosure, there is provided the lithium-sulfur battery electrolyte as defined in any one of the first to twelfth embodiments, wherein the acyclic ether is present in an amount of 10 volume % or less relative to the total volume of the nonaqueous solvent.

[0041] According to a fourteenth embodiment of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery as defined in any one of the first to thirteenth embodiments, wherein the acyclic ether comprises bis(2,2,2-trifluoroethyl)ether, methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl tert-butyl ether, methyl hexyl ether, ethyl tert-butyl ether, ethyl hexyl ether, or two or more thereof.

[0042] In another aspect of the present disclosure, a lithium-sulfur battery according to any one of the following embodiments is provided.

[0043] According to a fifteenth embodiment of the present disclosure, there is provided a lithium-sulfur battery, comprising the electrolyte for a lithium-sulfur battery as defined in any one of the first to fourteenth embodiments; a positive electrode comprising a positive electrode active material; and a negative electrode comprising a negative electrode active material.

[0044] According to a sixteenth embodiment of the present disclosure, there is provided a lithium-sulfur battery as defined in the fifteenth embodiment, wherein the positive electrode active material comprises inorganic sulfur (S 8 )、Li 2 S n (n≥1), disulfide compounds, organic sulfur compounds, carbon-sulfur polymers ((C 2 S x ) n , x represents an integer of 2.5-50, n≥2), or a mixture of two or more thereof.

[0045] According to a seventeenth embodiment of the present disclosure, there is provided a lithium-sulfur battery as defined in the fifteenth or sixteenth embodiment, wherein a ratio of the weight of the lithium-sulfur battery electrolyte to the weight of the positive electrode active material (E / S ratio) is 2 g / g or more.

[0046] According to an eighteenth embodiment of the present disclosure, there is provided a lithium-sulfur battery as defined in any one of the fifteenth to seventeenth embodiments, wherein the E / S ratio is 2.3 g / g or more.

[0047] Beneficial Effects

[0048] The electrolyte for a lithium-sulfur battery according to one embodiment of the present disclosure causes a change in the reduction path of lithium sulfide, causing a change in the discharge mechanism of the lithium-sulfur battery.

[0049] In this way, the lithium-sulfur battery using the lithium-sulfur battery electrolyte according to one embodiment of the present disclosure achieves additional capacity, thereby providing the effects of increasing the discharge capacity of the battery and achieving high energy density. DETAILED DESCRIPTION

[0050] Hereinafter, the preferred embodiments of the present disclosure will be described in detail. However, the description proposed herein is only a preferred example for the purpose of illustration only, is not intended to limit the scope of the present disclosure, and each constituent element can be modified differently or can be optionally combined. Therefore, it should be understood that other equivalents and variants can be made thereto without departing from the scope of the present disclosure.

[0051] Throughout the present specification, the expression "a part comprises a certain element" does not exclude the existence of any additional element but means that the part may further comprise other elements.

[0052] As used herein, the term "polysulfide (PS)" has the meaning of "polysulfide ions (PS)". x 2- , wherein x is an integer from 2 to 8)" and "lithium polysulfide (Li 2 S x or Li 2 S x - , where x is an integer from 2 to 8)".

[0053] As used herein, the term "lithium sulfide" refers to Li 2 S.

[0054] In one aspect of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery, comprising a non-aqueous solvent, a lithium salt, a nitrate and an aryl derivative.

[0055] wherein the non-aqueous solvent comprises: a heterocyclic compound containing an oxygen (O) atom or a sulfur (S) atom in a ring structure; and a glycol ether, and

[0056] The aryl derivative includes at least one of the compounds represented by the following Chemical Formulae 1 to 4:

[0057] [Chemical formula 1]

[0058] R 1 -M 1 -Li

[0059] [Chemical formula 2]

[0060] R 2 -M 2 -M 3 -R 3

[0061] [Chemical formula 3]

[0062] R 4 -M 4 -Sx-Li

[0063] [Chemical formula 4]

[0064] R 5 -M 5 -Sx-M 6 -R 6 ,

[0065] Among them, M 1 、M 2、M 3 、M 4 、M 5 and M 6 are each independently selected from selenium (Se) and tellurium (Te), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each independently represents a C6-C20 aryl group, and

[0066] X represents a number from 1 to 8.

[0067] According to one embodiment of the present disclosure, the nonaqueous solvent is contained in the electrolyte for lithium-sulfur batteries as a medium. The lithium salt is contained in the electrolyte for lithium-sulfur batteries as an electrolyte salt. The nitrate is contained as an additive for forming a stable coating film on a negative electrode containing lithium metal or the like and for improving charge and discharge efficiency. In addition, the aryl derivative is contained as an additive for causing a change in the reduction path of lithium sulfide and for providing additional discharge capacity.

[0068] According to the present disclosure, when the aryl derivative is included in the lithium-sulfur battery electrolyte, it can play a role in causing lithium sulfide (Li 2 S) chain extension, causing changes in the reduction path of lithium sulfide.

[0069] In particular, when the aryl derivative includes the compound represented by Chemical Formula 1, it can play a role in causing lithium sulfide to react with -M in the lithium-sulfur battery electrolyte including the compound. 1 -R 1 The morphology plays a role in chain extension.

[0070] In addition, when the aryl derivative comprises a compound represented by Chemical Formula 2, M 2 -M 3 The bond is broken, causing lithium sulfide to form -M in the lithium-sulfur battery electrolyte containing the compound. 2 -R 2 or -M 3 -R 3 Chain extension is performed on the morphology.

[0071] In addition, when the aryl derivative includes the compound represented by Chemical Formula 3, it can play a role in causing lithium sulfide to be converted into -S in the electrolyte for lithium-sulfur batteries including the compound. x -M 4 -R 4 The morphology plays a role in chain extension.

[0072] In addition, when the aryl derivative includes the compound represented by Chemical Formula 4, it can play a role in causing lithium sulfide to be converted into -S in the electrolyte for lithium-sulfur batteries including the compound. x -M 5 -R 5 and / or -S x -M 6 -R 6 The morphology plays a role in chain extension.

[0073] According to one embodiment of the present disclosure, M in Chemical Formula 1 to Chemical Formula 4 1 、M 2 、M 3 、M 4 、M 5 and M 6 Each may be selenium (Se).

[0074] According to one embodiment of the present disclosure, R in Chemical Formula 1 to Chemical Formula 4 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each may be a phenyl group.

[0075] According to another embodiment of the present disclosure, the electrolyte for a lithium-sulfur battery may include diphenyl diselenide (PDSe) as an aryl derivative.

[0076] According to the present disclosure, the lithium-sulfur battery electrolyte contains nitrate. In particular, the nitrate generally refers to a nitric acid compound or a nitrous acid compound that can be used as an additive in the lithium-sulfur battery electrolyte. For example, the nitric acid compound or the nitrous acid compound can provide an effect of forming a stable coating film on a negative electrode containing lithium metal or the like and improving charge and discharge efficiency, but the mechanism of the present disclosure is not limited thereto.

[0077] According to one embodiment of the present disclosure, specific examples of the nitrate may include, but are not limited to, inorganic nitric acid or nitrous acid compounds such as lithium nitrate (LiNO 3 ), potassium nitrate (KNO 3 ), cesium nitrate (CsNO 3 ), barium nitrate (Ba(NO 3 ) 2 ), ammonium nitrate (NH 4 NO 3 ), lithium nitrite (LiNO 2 ), potassium nitrite (KNO 2 ), cesium nitrite (CsNO 2 ), ammonium nitrite (NH4 NO 2 ) etc.; organic nitric acid or nitrous acid compounds such as methyl nitrate, dialkyl imidazolium nitrate, guanidine nitrate, imidazolium nitrate, pyridinium nitrate, ethyl nitrite, propyl nitrite, butyl nitrite, amyl nitrite, octyl nitrite, etc.; organic nitro compounds such as nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitropyridine, dinitropyridine, nitrotoluene, dinitrotoluene, etc.; or a mixture of two or more thereof.

[0078] According to one embodiment of the present disclosure, the cation of the nitrate may be selected from alkali metals such as lithium, sodium, potassium, rubidium, and cesium, but is not limited thereto.

[0079] According to another embodiment of the present disclosure, the nitrate may include lithium nitrate (LiNO 3 ).

[0080] According to one embodiment of the present disclosure, the sum of the weight of the nitrate and the weight of the aryl derivative may be 4 wt% or more relative to the total weight of the electrolyte for a lithium-sulfur battery. In particular, the sum of the weight of the nitrate and the weight of the aryl derivative may be 5-10 wt%, 5-9 wt%, or 5-7 wt% relative to the total weight of the electrolyte for a lithium-sulfur battery. When the sum of the weight of the nitrate and the weight of the aryl derivative falls within the above-defined range, favorable effects may be achieved in terms of increased discharge capacity and improved life characteristics during operation of a lithium-sulfur battery using the electrolyte, but the scope of the present disclosure is not limited thereto.

[0081] According to another embodiment of the present disclosure, the weight of the aryl derivative may be equal to or less than the weight of the nitrate. In particular, the weight of the aryl derivative may be less than the weight of the nitrate. When the weight ratio of the aryl derivative relative to the nitrate satisfies the above-defined range, favorable effects may be achieved in terms of increased discharge capacity and improved life characteristics during operation of a lithium-sulfur battery using the electrolyte, but the scope of the present disclosure is not limited thereto.

[0082] According to one embodiment of the present disclosure, when the aryl derivative comprises a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 3, or a mixture thereof, the molar ratio of the compound represented by Chemical Formula 1, the compound represented by Chemical Formula 3, or the mixture thereof to the nitrate may be 0.5:1 or less. In particular, the molar ratio of the compound represented by Chemical Formula 1, the compound represented by Chemical Formula 3, or the mixture thereof to the nitrate may be 0.1:1-0.4:1 or 0.1:1-0.3:1. When the aryl derivative comprises a mixture of the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 3, the molar ratio refers to the molar ratio of the mixture.

[0083] According to another embodiment of the present disclosure, when the aryl derivative comprises a compound represented by Chemical Formula 2, a compound represented by Chemical Formula 4, or a mixture thereof, the molar ratio of the compound represented by Chemical Formula 2, the compound represented by Chemical Formula 4, or the mixture thereof relative to the nitrate may be 0.2:1 or less. In particular, the molar ratio of the compound represented by Chemical Formula 2, the compound represented by Chemical Formula 4, or the mixture thereof relative to the nitrate may be 0.1:1 or less. For example, the molar ratio of the compound represented by Chemical Formula 2, the compound represented by Chemical Formula 4, or the mixture thereof relative to the nitrate may be 0.05:1-0.2:1 or 0.05:1-0.1:1. When the aryl derivative comprises a mixture of the compound represented by Chemical Formula 2 and the compound represented by Chemical Formula 4, the molar ratio refers to the molar ratio of the mixture.

[0084] When the molar ratio of the aryl derivative relative to the nitrate satisfies the above-defined range, advantageous effects may be achieved in terms of increased discharge capacity and improved life characteristics during operation of a lithium-sulfur battery using the electrolyte, but the scope of the present disclosure is not limited thereto.

[0085] According to yet another embodiment of the present disclosure, relative to the total weight of the lithium-sulfur battery electrolyte, the ratio of the combined weight of the nitrate and the aryl derivative may be 4 wt % or more, the weight of the aryl derivative may be equal to or less than the weight of the nitrate, and the molar ratio of the aryl derivative to the nitrate may be 0.5:1 or less.

[0086] According to the present disclosure, the nonaqueous solvent includes a combination of a heterocyclic compound and a glycol ether.

[0087] Herein, the glycol ether is an acyclic ether containing two oxygen atoms, and any glycol ether may be used without particular limitation as long as it can be used as an electrolyte for a lithium-sulfur battery.

[0088] According to one embodiment of the present disclosure, the glycol ether may be represented by the following Chemical Formula 5:

[0089] [Chemical formula 5]

[0090] R 7 -O-(CH 2 CH 2 O) x -R 8

[0091] Where R 7 and R 8 are the same or different, and each independently represents a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C6-C12 aryl group, or a substituted or unsubstituted C7-C13 arylalkyl group; and x represents an integer of 0-4.

[0092] Specific examples of glycol ethers may include, but are not limited to, 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 ether, or two or more thereof.

[0093] According to one embodiment of the present disclosure, the nonaqueous solvent may include dimethoxyethane as the glycol ether.

[0094] The heterocyclic compound is an ether containing an oxygen (O) atom or a sulfur (S) atom in the ring structure and thus containing a -COC structure or a -CSC- structure in the ring structure, and any heterocyclic compound can be used without particular limitation as long as it can be used as an electrolyte for a lithium-sulfur battery.

[0095] According to one embodiment of the present disclosure, the heterocyclic compound simultaneously contains two or more double bonds and any one of an oxygen atom and a sulfur atom, so that a solid electrolyte interface (SEI) layer is formed on the surface of the negative electrode (lithium-based metal) through the ring-opening reaction of the heterocyclic compound in the initial discharge stage, thereby inhibiting the formation of lithium dendrites. In addition, the heterocyclic compound reduces the decomposition of the electrolyte on the surface of the lithium-based metal and the side reactions caused thereby, thereby improving the life characteristics of the lithium-sulfur battery. In addition, since the heterocyclic compound is difficult to dissolve salts due to the delocalization of the lone pair of electrons of the heteroatom (oxygen atom or sulfur atom), it can play a role in reducing the dissolution of polysulfide into the electrolyte. However, the scope of the present disclosure is not limited to this.

[0096] According to one embodiment of the present disclosure, the heterocyclic compound substantially contains two or more double bonds to form a SEI layer on the surface of the negative electrode (lithium-based metal), and substantially contains heteroatoms (oxygen atoms or sulfur atoms) to achieve the effect of imparting polarity to increase affinity with other solvents in the electrolyte, etc.

[0097] According to one embodiment of the present disclosure, the heterocyclic compound may be a 4- to 15-membered, particularly a 4- to 7-membered, and more particularly a 5- to 6-membered heterocyclic compound. In addition, the heterocyclic compound may be an unsubstituted or substituted heterocyclic compound selected from the group consisting of a C1-C4 alkyl group, a C3-C8 cycloalkyl group, a C6-C10 aryl group, a halogen group, a nitro group (-NO 2 ), amine (-NH 2 ) and sulfonyl (-SO 2 ). According to one embodiment of the present disclosure, when the heterocyclic compound is substituted as described above, the free radical is stabilized, thereby achieving a favorable effect in terms of suppressing the side reaction between the electrolyte components. However, the scope of the present disclosure is not limited thereto.

[0098] Specific examples of the heterocyclic compound may include, but are not limited to, 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.

[0099] According to one embodiment of the present disclosure, the nonaqueous solvent may include 2-methylfuran as the heterocyclic compound.

[0100] According to one embodiment of the present disclosure, the glycol ether may be present in an amount of 60 wt % or more, such as 65 wt % or more, 70 wt % or more, 75 wt % or more, or 80 wt % or more, relative to the total volume of the non-aqueous solvent, and may be 85 wt % or less, but is not limited thereto. When the amount of the glycol ether falls within the above-defined range, it may provide an effect of providing suitable solubility for lithium salts, nitrates, aryl derivatives, and lithium polysulfide dissolved from the positive electrode during battery operation, but the scope of the present disclosure is not limited thereto.

[0101] According to one embodiment of the present disclosure, the heterocyclic compound may occupy a volume other than the glycol ether relative to the total volume of the non-aqueous solvent. For example, the heterocyclic compound may be present in an amount of 15% by weight or more, such as 20% by weight or more, and may be 40% by weight or less, 35% by weight or less, 30% by weight or less, or 25% by weight or less, but is not limited thereto. When the amount of the heterocyclic compound falls within the above-defined range, it may provide an effect of providing suitable solubility for lithium salts, nitrates, aryl derivatives, and lithium polysulfide dissolved from the positive electrode during battery operation, but the scope of the present disclosure is not limited thereto.

[0102] According to another embodiment of the present disclosure, the ratio of the total volume of the glycol ether to the total volume of the heterocyclic compound may be 3:1 or more. In particular, the ratio of the total volume of the glycol ether to the total volume of the heterocyclic compound may be 3:1-5:1, 3:1-4:1, or 3.5:1-4:1. When the ratio of the glycol ether to the heterocyclic compound falls within the above-defined range, there is a favorable effect in terms of improvement in battery operation stability, but the scope of the present disclosure is not limited thereto.

[0103] According to one embodiment of the present disclosure, the non-aqueous solvent may further contain an acyclic ether containing one oxygen atom on the basis of containing the above-mentioned heterocyclic compound and glycol ether. When the non-aqueous solvent further contains an acyclic ether, it can provide a favorable effect in terms of improving the overvoltage at SOC70 during battery operation, but the scope of the present disclosure is not limited thereto.

[0104] According to one embodiment of the present disclosure, the acyclic ether containing one oxygen atom may be represented by the following Chemical Formula 6:

[0105] [Chemical formula 6]

[0106] R 9 -OR 10

[0107] Where R 9 and R 10 Each independently represents a substituted or unsubstituted C1-C20 alkyl group.

[0108] According to one embodiment of the present disclosure, the "substitution" in the substituted C1-C20 alkyl group may be carried out by a substituent, such as a halogen atom, a hydroxyl group, a nitro group, a cyano group, an amino group, an amidino group, an acetamido group, a hydrazine, a hydrazone, a carboxyl group, a sulfonyl group, a sulfamoyl group, a sulfonate group, a phosphate ester, a C1-C5 alkyl group, a C1-C5 alkoxy group, a C2-C5 alkenyl group, a C2-C5 alkynyl group, a C4-C10 cycloalkyl group, a C6-C10 aryl group, a C6-C10 heteroaryl group, a C6-C20 arylalkyl group, a C6-C20 heteroarylalkyl group, or a combination thereof.

[0109] According to another embodiment of the present disclosure, in terms of suppressing side reactions with polysulfide or lithium during battery operation, R 9 and R 10 Each may independently represent a substituted or unsubstituted C1-C20 alkyl group.

[0110] According to another embodiment of the present invention, R 9 and R 10 Each of them independently represents methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, isopropyl, sec-butyl, isobutyl, tert-butyl, 1-methylbutyl, 1-ethylpropyl, 2-methylbutyl, isopentyl, neopentyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, tert-pentyl, 1,3-dimethylbutyl, 3,3-dimethylbutyl, 2-ethylbutyl, 2- ethyl-2-methylpropyl, straight-chain or branched heptyl, 1-methylheptyl, 2-ethylhexyl, 1,5-dimethylhexyl, tert-octyl, branched nonyl, branched decyl, branched undecyl, branched dodecyl, branched tridecyl, branched tetradecyl, branched pentadecyl, branched hexadecyl, branched heptadecyl, branched octadecyl, straight-chain or branched nonadecyl, straight-chain or branched eicosyl, cyclopropyl, cyclopropylmethyl, cyclobutyl, cyclobutylmethyl, cyclopentyl, cyclohexyl, cyclohexylmethyl, cycloheptyl, cyclooctyl, cyclohexylpropyl, cyclododecyl, norbornyl, bornyl, cyclopentylethyl or bicyclooctyl.

[0111] According to yet another embodiment of the present disclosure, in terms of suppressing side reactions with polysulfide or lithium during battery operation, R 9 It may preferably represent an unsubstituted alkyl group, but the scope of the present disclosure is not limited thereto.

[0112] According to one embodiment of the present disclosure, for example, the acyclic ether may include bis(2,2,2-trifluoroethyl)ether, methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl tert-butyl ether, methyl hexyl ether, ethyl tert-butyl ether, ethyl hexyl ether, or two or more thereof.

[0113] According to one embodiment of the present disclosure, the above-mentioned type of acyclic ether may function as a non-solvent for polysulfides eluted from the cathode, thereby achieving a favorable effect in terms of suppressing the elution of polysulfides from the cathode.

[0114] According to another embodiment of the present disclosure, the acyclic ether may be present in an amount of 10% by volume or less relative to the total volume of the non-aqueous solvent, but is not limited thereto. In particular, the acyclic ether may be present in an amount of 1-10% by volume or 5-10% by volume relative to the total volume of the non-aqueous solvent. When the content of the acyclic ether falls within the above-defined range, a favorable effect may be provided in terms of improvement in battery operation stability, but the scope of the present disclosure is not limited thereto.

[0115] According to another embodiment of the present disclosure, the acyclic ether may be present in an amount of 10 volume % or less relative to 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 6:1 or more, such as 6:1-7.5:1 or 6.5:1-7:1, but the scope of the present disclosure is not limited thereto.

[0116] According to one embodiment of the present disclosure, when the content of the above-mentioned solvent falls within the above-defined range relative to the total volume of the non-aqueous solvent, it can provide favorable effects in terms of suppressing the dissolution of polysulfides and the operation stability of the battery, but the scope of the present disclosure is not limited thereto.

[0117] The lithium salt is not particularly limited as long as it can be conventionally used in lithium-sulfur battery electrolytes. Specific examples of the lithium salt may include, but are not limited to: LiCl, LiBr, LiI, 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 , CH 3 SO 3Li, 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 CLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide, or two or more thereof.

[0118] According to one embodiment of the present disclosure, the lithium salt may not include lithium nitrate. Lithium nitrate may be used as an example of nitrate.

[0119] According to one embodiment of the present disclosure, the lithium salt may include lithium bis(fluorosulfonyl)imide (LiFSI).

[0120] According to one embodiment of the present disclosure, the lithium salt concentration may be appropriately determined in consideration of ion conductivity, solubility, etc. For example, the lithium salt concentration may be 0.1-4.0 M, 0.5-2.0 M, 0.5-1.0 M, or 0.75 M. When the lithium salt concentration falls within the above-defined range, favorable effects may be achieved in terms of ion conductivity and electrolyte viscosity, but the scope of the present disclosure is not limited thereto.

[0121] According to another embodiment of the present disclosure, in addition to the above components, the lithium-sulfur battery electrolyte may further include other additives to improve charge and discharge characteristics, flame retardancy, etc. Such additives are not particularly limited, but specific examples thereof may include pyridine, triethyl phosphite, triethanolamine, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted Oxazolidinone, N,N-substituted imidazolidine, ammonium salt, pyrrole, 2-methoxyethanol, aluminum chloride, fluoroethylene carbonate (FEC), propylene sultone (PRS), vinylene carbonate (VC), etc.

[0122] The electrolyte for a lithium-sulfur battery according to one embodiment of the present disclosure may be obtained by a conventional method known to those skilled in the art without particular limitation.

[0123] In another aspect of the present disclosure, a lithium-sulfur battery is provided, comprising the above-mentioned electrolyte for lithium-sulfur battery; a positive electrode, the positive electrode comprising a positive electrode active material; and a negative electrode, the negative electrode comprising a negative electrode active material. In particular, the positive electrode active material comprises elemental sulfur, a sulfur compound or a mixture thereof.

[0124] Any positive electrode, positive electrode active material, negative electrode, and negative electrode active material may be used without particular limitation as long as they can be used in a lithium-sulfur battery while not impairing the purpose of the present disclosure.

[0125] For example, the positive electrode may include a positive electrode collector and a positive electrode active material layer coated on one surface or both surfaces of the positive electrode collector, and the negative electrode may include a negative electrode collector and a negative electrode active material layer coated on one surface or both surfaces of the negative electrode collector, wherein the positive electrode collector is not particularly limited as long as it supports the positive electrode active material layer and has high conductivity and does not cause any chemical changes in the corresponding battery, and the negative electrode collector is not particularly limited as long as it supports the negative electrode active material layer and has high conductivity and does not cause any chemical changes in the corresponding battery.

[0126] According to one embodiment of the present disclosure, the positive electrode active material comprises elemental sulfur, a sulfur compound or a mixture thereof. In particular, the positive electrode active material may comprise inorganic sulfur (S 8 )、Li 2 S n (n≥1), disulfide compounds, organic sulfur compounds, carbon-sulfur polymers ((C 2 S x ) n , x represents an integer of 2.5-50, n≥2), or a mixture of two or more thereof.

[0127] According to one embodiment of the present disclosure, the negative electrode active material is not particularly limited, and may include a material capable of reversibly inserting / deinserting lithium (Li + ) or a material that can reversibly react with lithium ions to form a lithium-containing compound. For example, the negative electrode active material may include lithium metal, a lithium alloy, or a mixture thereof. Specific examples of lithium alloys include alloys of lithium (Li) and the following metals: 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 two or more thereof.

[0128] In addition, on the basis of containing active materials, the positive electrode active material layer and the negative electrode active material layer may each further include conductive materials, binders, additives, etc. Since such components may be any conventional type of materials, detailed description thereof will be omitted herein.

[0129] According to one embodiment of the present disclosure, the external shape of the lithium-sulfur battery can be selected from a coin shape, a cylinder shape, a bag shape or a prism shape, without particular limitation. In addition, the lithium-sulfur battery can be used not only as a battery cell used as a power source for a compact device, but also as a unit cell in a medium or large battery module including a plurality of battery cells, and its application is not particularly limited.

[0130] According to one embodiment of the present disclosure, a lithium-sulfur battery using a positive electrode including a sulfur-carbon composite can achieve excellent effects in terms of energy density of the battery as well as initial capacity and cycle stability, but the effects of the present disclosure are not limited thereto.

[0131] According to one embodiment of the present disclosure, the lithium-sulfur battery can provide an effect of ensuring an amount of electrolyte to improve a side reaction caused by polysulfides in the electrolyte while increasing energy density.

[0132] According to one embodiment of the present disclosure, the lithium-sulfur battery may have a ratio (E / S ratio) of 2 g / g or more, which is the ratio of the weight of the electrolyte for the lithium-sulfur battery to the weight of sulfur as the positive electrode active material, i.e., the electrolyte / sulfur (E / S) ratio. In particular, the electrolyte / sulfur (E / S) ratio may be 2.3 g / g or more. For example, the electrolyte / sulfur (E / S) ratio may be 2-3 g / g, 2.1-2.7 g / g, or 2.3-2.5 g / g. In order to solve the problem of the related art, that is, the side reaction caused by the high concentration of polysulfides (generated) in the electrolyte when the E / S ratio is reduced to provide an increased energy density, the present disclosure is intended to provide the effect of stabilizing the E / S ratio while increasing the energy density of the battery. Therefore, the lithium-sulfur battery may have an E / S ratio greater than the range defined above, and it is obvious to those skilled in the art that the upper limit of the range is not particularly limited. Moreover, the scope of the present disclosure is not limited thereto.

[0133] According to another embodiment of the present disclosure, the lithium-sulfur battery may have an energy density of 400-500Wh / kg. In particular, the lithium-sulfur battery may have an energy density of 430Wh / kg or more, 450Wh / kg or more, or 460Wh / kg or more, but the scope of the present disclosure is not limited thereto.

[0134] Modes for use in this disclosure

[0135] Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the following Examples are for illustrative purposes only, and the scope of the present disclosure is not limited thereto.

[0136] First, a pouch cell type lithium-sulfur battery was obtained as follows, and the performance of the obtained battery was evaluated.

[0137] Test Example 1: Evaluation of battery performance based on the addition of PDSe

[0138] [Battery Manufacturing]

[0139] Example 1

[0140] Preparation of electrolyte for lithium-sulfur batteries

[0141] First, 0.5 M lithium bis(fluorosulfonyl)imide (LiFSI) and 4.0 wt % lithium nitrate (LiNO 3 , molar mass 69 g / mol) and 1 wt % of diphenyl diselenide (PDSe, molar mass 312 g / mol) were introduced into a mixture of dimethoxyethane (DME), 2-methylfuran (2MeF) and bis(2,2,2-trifluoroethyl) ether (BTFE) (v / v / v=7:2:1), and the resulting mixture was stirred for 12 h to prepare an electrolyte.

[0142] Preparation of electrodes

[0143] A sulfur-carbon composite (S:C=70:30 (weight ratio)) as a cathode active material and polyacrylic acid (PAA) as a binder were mixed in distilled water as a solvent at a weight ratio of 97:3 to prepare a cathode slurry.

[0144] The obtained positive electrode slurry composition was applied to both surfaces of an aluminum current collector having a thickness of 12 μm, dried at 80° C., and rolled by using a roller press to obtain a positive electrode. Herein, the positive electrode active material loading was 3.45 mAh / cm 2 .

[0145] A lithium metal having a thickness of 30 μm was prepared as a negative electrode.

[0146] Manufacturing of lithium-sulfur batteries

[0147] The positive electrode and the negative electrode prepared as described above were positioned in such a manner that they faced each other and stacked with a polyethylene separator (thickness 16 μm, porosity 68%) interposed between the two electrodes to assemble a pouch-type battery, 1 g of the electrolyte prepared as described above was injected thereinto to an E / S (electrolyte / S loading) ratio of 2.15 g / g, followed by sealing to obtain a pouch-type lithium-sulfur battery.

[0148] Example 2

[0149] A lithium-sulfur battery was obtained in the same manner as in Example 1, except that 3 wt % of PDSe was added.

[0150] Example 3

[0151] A lithium-sulfur battery was obtained in the same manner as in Example 1, except that 5 wt % of PDSe was added.

[0152] Comparative Example 1

[0153] A lithium-sulfur battery was obtained in the same manner as in Example 1, except that PDSe was not added.

[0154] [Table 1]

[0155]

[0156] [Evaluation and results of battery performance]

[0157] The performance of each battery was evaluated as follows. The results are shown in Table 2 below.

[0158] Evaluation of initial discharge capacity

[0159] Each battery was operated three times under the conditions of 0.1C charge / 0.1C discharge (cut-off voltage 2.5 V / 1.8 V) at a temperature of 25°C to determine the initial discharge capacity.

[0160] Determination of energy density

[0161] The energy density of each battery was calculated by multiplying the initial discharge capacity (Ah) of each battery by the average operating voltage (V), and then dividing by the battery weight (kg).

[0162] Evaluation of life span

[0163] After evaluating the initial discharge capacity, each battery was repeatedly operated under the conditions of 0.2C charge / 0.1C discharge (cutoff voltage 2.5V / 1.8V) at 25° C. Then, the number of cycles when the energy density of the battery reached 400Wh / kg was examined to determine the life characteristics of the battery.

[0164] [Table 2]

[0165] Capacity (mAh / g) Energy density (Wh / kg) Lifespan (cycle) Comparative Example 1 1138 445 31 Example 1 1157 457 32 Example 2 1238 487 30 Example 3 1245 489 22

[0166] As can be seen from Tables 1 and 2, when the E / S ratio is 2.15, the energy density is improved by adding PDSe.

[0167] Test Example 2: Evaluation of battery performance based on the molar ratio of additives and E / S ratio (1)

[0168] By using the composition shown in the following Table 3, each battery was obtained in the same manner as in Example 1, and the battery performance was evaluated in the same manner as above. The results are shown in the following Table 4. For the purpose of comparison in terms of composition and performance, the test results of Example 1 are also shown.

[0169] [Table 3]

[0170]

[0171] [Table 4]

[0172] Capacity (mAh / g) Energy density (Wh / kg) Lifespan (cycle) Example 1 1157 457 32 Example 4 1165 451 38 Example 5 1174 440 49 Example 6 1193 462 35 Example 7 1213 452 42

[0173] As can be seen from Tables 3 and 4, when the E / S ratio is 2.3 or more, the life characteristics of the battery as well as its initial capacity and energy density are improved by adding PDSe. In addition, it can be seen that when the E / S ratio is 2.3 or more, the molar ratio of the aryl derivative to the nitrate is 0.1 or less, which provides further improvement in battery performance.

[0174] Test Example 3: Evaluation of battery performance based on additive molar ratio and E / S ratio (2)

[0175] By using the composition shown in Table 5 below, each battery was obtained in the same manner as in Example 1, except that BTFE was not used as a non-aqueous solvent, and 2MeF and DME were used at a volume ratio of 20:80 (2MeF:DME), and the battery performance was evaluated in the same manner as above. The results are shown in Table 6 below.

[0176] [Table 5]

[0177]

[0178] [Table 6]

[0179] Capacity (mAh / g) Energy density (Wh / kg) Comparative Example 2 1221 454 Example 8 1252 464 Example 9 1266 454 Example 10 1298 440 Embodiment 11 1249 461 Example 12 1273 472

[0180] As can be seen from Tables 5 and 6, when the E / S ratio is 2.5 or more, the capacity and energy density of the battery are still improved by adding PDSe.

Claims

1. An electrolyte for a lithium-sulfur battery, comprising a non-aqueous solvent, a lithium salt, a nitrate and an aromatic derivative, wherein the non-aqueous solvent comprises: a heterocyclic compound containing an oxygen (O) atom or a sulfur (S) atom in a ring structure; and a glycol ether, and The aryl derivative includes at least one of the compounds represented by the following Chemical Formulae 1 to 4: [Chemical formula 1] R 1 -M1-Li [Chemical formula 2] R 2 -M2-M3-R 3 [Chemical formula 3] R 4 -M4-Sx-Li [Chemical formula 4] R 5 -M5-Sx-M6-R 6 , wherein M1, M2, M3, M4, M5 and M6 are each independently selected from selenium (Se) and tellurium (Te), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each independently represents a C6-C20 aryl group, and X represents a number from 1 to 8.

2. The lithium-sulfur battery electrolyte according to claim 1, wherein M1, M2, M3, M4, M5 and M6 in Chemical Formula 1 to Chemical Formula 4 each represent selenium (Se). 3 . The electrolyte for a lithium-sulfur battery according to claim 1 , wherein the nitrate contains an alkali metal as a cation.

4. The electrolyte for a lithium-sulfur battery according to claim 3, wherein the nitrate comprises lithium nitrate (LiNO3). 5 . The lithium-sulfur battery electrolyte according to claim 1 , wherein the sum of the weight of the nitrate and the weight of the aryl derivative is 4% by weight or more relative to the total weight of the lithium-sulfur battery electrolyte. 6 . The electrolyte for a lithium-sulfur battery according to claim 1 , wherein the weight of the aryl derivative is equal to or less than the weight of the nitrate.

7. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the aryl derivative comprises a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 3, or a mixture thereof, and The molar ratio of the compound represented by Chemical Formula 1, the compound represented by Chemical Formula 3, or a mixture thereof to the nitrate is 0.5:1 or less.

8. The electrolyte for a lithium-sulfur battery according to claim 1, wherein the aryl derivative comprises a compound represented by Chemical Formula 2, a compound represented by Chemical Formula 4, or a mixture thereof, and The molar ratio of the compound represented by Chemical Formula 2, the compound represented by Chemical Formula 4, or a mixture thereof to the nitrate is 0.2:1 or less.

9. The electrolyte for lithium-sulfur battery according to claim 1, wherein the lithium salt comprises 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 two or more thereof.

10. The lithium-sulfur battery electrolyte according to claim 1, wherein The ratio of the total volume of the glycol ether to the total volume of the heterocyclic compound is 3:1 or more.

11. The lithium-sulfur battery electrolyte according to claim 1, wherein the heterocyclic compound 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, thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, 2,5-dimethylthiophene, or two or more thereof. 12 . The electrolyte for lithium-sulfur batteries according to claim 1 , wherein the nonaqueous solvent further comprises an acyclic ether containing one oxygen atom. 13 . The lithium-sulfur battery electrolyte according to claim 12 , wherein the acyclic ether is present in an amount of 10% by volume or less relative to the total volume of the nonaqueous solvent.

14. The lithium-sulfur battery electrolyte according to claim 12, wherein the acyclic ether comprises bis(2,2,2-trifluoroethyl)ether, methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl tert-butyl ether, methyl hexyl ether, ethyl tert-butyl ether, ethyl hexyl ether, or two or more thereof.

15. A lithium-sulfur battery comprising: The electrolyte for a lithium-sulfur battery according to any one of claims 1 to 13; a positive electrode comprising a positive electrode active material; and a negative electrode, the negative electrode comprising a negative electrode active material, The positive electrode active material comprises elemental sulfur, a sulfur compound or a mixture thereof.

16. The lithium-sulfur battery according to claim 15, wherein the positive electrode active material comprises inorganic sulfur (S8), Li2S n (n≥1), disulfide compounds, organic sulfur compounds, carbon-sulfur polymers (C2S x ) n , x represents an integer of 2.5-50, n≥2), or a mixture of two or more thereof.

17. The lithium-sulfur battery according to claim 15, wherein: The ratio of the weight of the electrolyte for the lithium-sulfur battery to the weight of the positive electrode active material (E / S ratio) is 2 g / g or more.

18. The lithium-sulfur battery according to claim 17, wherein the E / S ratio is 2.3 g / g or more.

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