KR20210120858A - Electrolyte for lithium-sulfur battery and lithium-sulfur battery comprising thereof - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium-sulfur battery and a lithium-sulfur battery including the same, and more specifically, to an electrolyte for a lithium-sulfur battery that includes lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive includes an alkyl vinyl ether compound. The electrolyte for a lithium-sulfur battery of the present invention improves the efficiency and stability of a negative electrode, thereby improving the capacity and lifespan characteristics of a lithium-sulfur battery.

Description

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

The present invention relates to an electrolyte for a lithium-sulfur battery and a lithium-sulfur battery comprising the same.

As the application range of lithium secondary batteries is expanded to not only portable electronic devices but also electric vehicles (EVs) and electric storage systems (ESSs), the demand for lithium secondary batteries with high capacity, high energy density and long life is increasing. have.

Among various lithium secondary batteries, lithium-sulfur batteries use a sulfur-based material containing a sulfur-sulfur bond as a positive electrode active material, and lithium metal, a carbon-based material in which lithium ion insertion/deintercalation occurs, or lithium It is a battery system that uses silicon or tin, which forms an alloy with the anode, as an anode active material.

In lithium-sulfur batteries, sulfur, which is the main material of the cathode active material, has a low weight per atom, is easy to supply due to abundant resources, is inexpensive, has no toxicity, and is an environmentally friendly material.

In addition, the lithium-sulfur battery has a theoretical specific capacity of 1,675 mAh/g resulting from the _{conversion reaction of lithium ions and sulfur (S 8} +16Li ⁺ +16e ^- → 8Li _{2 S) at the positive electrode, and the negative electrode} It shows a theoretical energy density of 2,600 Wh/kg when lithium metal is used. This is another cell system currently being studied (Ni-MH cell: 450 Wh/kg, Li-FeS cell: 480 Wh/kg, Li-MnO ₂ cell: 1,000 Wh/kg, Na-S cell: 800 Wh/kg). And since it has a very high value compared to the theoretical energy density of a lithium ion battery (250 Wh/kg), it is attracting attention as a high-capacity, eco-friendly and low-cost lithium secondary battery among secondary batteries being developed so far.

Specifically, when lithium metal is used as an anode active material in a lithium-sulfur battery, not only the theoretical specific capacity is very high as 3,860 mAh/g, but also the Standard Hydrogen Electrode (SHE) is very low at -3.045 V, so high capacity, high energy Since it is possible to realize a high-density battery, various studies are being conducted as a next-generation battery system.

However, as lithium metal, which is an anode active material, easily reacts with an electrolyte due to its high chemical/electrochemical reactivity, a passivation layer is formed on the surface of the anode. Such a passivation film causes a local current density difference to form a dendritic lithium dendrite on the lithium metal surface. In addition, the lithium dendrite formed in this way causes an internal short circuit of the battery and inert lithium (dead lithium), which not only increases the physical and chemical instability of the lithium secondary battery, but also reduces the capacity of the battery and shortens the cycle life.

Due to the high instability of lithium metal as described above, a lithium-sulfur battery using lithium metal as an anode has not been commercialized.

Accordingly, various methods such as introducing a protective layer on the lithium metal surface or changing the composition of the electrolyte have been studied.

For example, Korean Patent Laid-Open No. 2016-0034183 discloses that a protective layer is formed with a polymer matrix capable of accumulating an electrolyte while protecting the anode on an anode active layer containing lithium metal or lithium alloy, thereby preventing loss of electrolyte and generation of dendrites. It is disclosed that it can be prevented.

In addition, Korean Patent Laid-Open No. 2016-0052351 discloses that the growth of lithium dendrites can be inhibited by including a lithium dendrite absorbent material in a polymer protective film formed on the surface of lithium metal, thereby improving the stability and lifespan characteristics of a lithium secondary battery. are doing

In addition, Jiangfeng Qian et al. and Korean Patent Application Laid-Open No. 2013-0079126 discloses lithium metal by increasing the lithium salt concentration or including a non-aqueous organic solvent including 1,3,5-trioxane, 1,3-dioxolane and a fluorine-based cyclic carbonate, respectively. It is disclosed that the characteristics of the battery can be improved.

These prior documents suppressed the reaction between the electrolyte and lithium metal or the generation of lithium dendrites to some extent, but the effect is not sufficient. In addition, as the battery is charged and discharged, there is a problem that the protective layer is hardened or swelled. In addition, when an electrolyte having a specific composition is used, there is a limitation in applicable batteries and may cause deterioration of battery performance. Therefore, there is still a need for development of a lithium-sulfur battery having excellent capacity and lifespan characteristics by improving the efficiency and stability of the lithium metal negative electrode.

Republic of Korea Patent Publication No. 2016-0034183 (2016.03.29), anode for lithium secondary battery and lithium secondary battery including the same Republic of Korea Patent Publication No. 2016-0052351 (2016.05.12), Lithium metal electrode having a stable protective layer and lithium secondary battery including the same Republic of Korea Patent Publication No. 2013-0079126 (2013.07.10), an electrolyte for a lithium metal battery and a lithium metal battery comprising the same

Jiangfeng Qian et al., High rate and stable cycling of lithium metal anode, Nature Communications 2015, 6, 6362

Accordingly, the present inventors have conducted various studies to solve the above problem, and as a result, when an alkyl vinyl ether compound is included as an additive in an electrolyte for a lithium-sulfur battery, the efficiency and stability of the anode containing lithium metal are improved, and lithium-sulfur The present invention was completed by confirming that the capacity and lifespan of the battery could be improved.

Accordingly, an object of the present invention is to provide an electrolyte for a lithium-sulfur battery capable of realizing a lithium-sulfur battery having excellent capacity and lifespan characteristics.

Another object of the present invention is to provide a lithium-sulfur battery including the electrolyte.

In order to achieve the above object, the present invention provides an electrolyte for a lithium-sulfur battery comprising a lithium salt, a non-aqueous organic solvent and an additive, wherein the additive includes an alkyl vinyl ether compound.

The alkyl vinyl ether compound may be represented by the following formula (1):

[Formula 1]

(In Formula 1, R is as described in the specification).

The alkyl vinyl ether compound may include at least one selected from the group consisting of methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, pentyl vinyl ether and hexyl vinyl ether.

The non-aqueous organic solvent may include an ether-based compound and a heterocyclic compound including one or more double bonds.

The ether-based compound may include a linear ether compound.

The heterocyclic compound may include one or more heteroatoms selected from the group consisting of an oxygen atom and a sulfur atom.

The non-aqueous organic solvent may include an ether-based compound and a heterocyclic compound in a volume ratio of 95:5 to 5:95.

The lithium salt is 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, (SO ₂ F) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, chloroborane lithium , and may include at least one selected from the group consisting of lower aliphatic lithium carboxylates having 4 or less carbon atoms, lithium 4-phenyl borate, and lithium imide.

The alkyl vinyl ether compound may be included in an amount of 0.1 to 10% by weight based on 100% by weight of the total electrolyte for a lithium-sulfur battery.

In addition, the present invention provides a lithium-sulfur battery including the electrolyte for the lithium-sulfur battery.

The electrolyte for a lithium-sulfur battery according to the present invention includes an alkyl vinyl ether compound as an additive, thereby improving the efficiency and stability of the negative electrode including lithium metal, and maximizing the capacity expression of the positive electrode to increase the capacity of the lithium-sulfur battery and long lifespan.

1 is a graph showing the results of evaluation of capacity and lifespan characteristics of lithium-sulfur batteries according to Example 1 and Comparative Example 1. FIG.
FIG. 2 is a graph showing the evaluation results of charging and discharging efficiency of lithium-sulfur batteries according to Example 1 and Comparative Example 1. FIG.
3 is a graph showing the voltage-capacity of the first cycle of the lithium-sulfur battery according to Example 1 and Comparative Example 1. FIG.
4 is a graph showing the results of evaluation of capacity and lifespan characteristics of lithium-sulfur batteries according to Example 2 and Comparative Example 1. FIG.
5 is a graph showing the results of evaluation of charge and discharge efficiency of lithium-sulfur batteries according to Example 2 and Comparative Example 1. FIG.
6 is a graph showing the voltage-capacity of the first cycle of lithium-sulfur batteries according to Example 2 and Comparative Example 1. FIG.

Hereinafter, the present invention will be described in more detail.

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as 'comprise' or 'have' are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

As used herein, the term “composite” refers to a material in which two or more materials are combined to form different phases physically and chemically while exhibiting more effective functions.

As used herein, the term “polysulfide” refers to “polysulfide ion (S _x ^2- , x = 8, 6, 4, 2))” and “lithium polysulfide (Li ₂ S _x or LiS _x ^- , x = 8, 6, 4, 2)”.

Lithium secondary batteries, which were used in portable electronic devices and stayed in a limited market, are rapidly expanding to electric vehicle (EV) and energy storage system markets. is being requested

Lithium-sulfur batteries exhibit high theoretical discharge capacity and theoretical energy density among various secondary batteries, and lithium metal, which is mainly used as an anode active material, has a very small atomic weight (6.94 g/au) and density (0.534 g/cm 3 ). And it is easy to reduce the weight, so it is spotlighted as a next-generation battery.

However, as described above, lithium metal has high reactivity, so when the electrolyte and lithium metal come into contact, a passivation film is formed on the surface of the lithium metal due to spontaneous decomposition of the electrolyte, which forms inert lithium and lithium dendrites to improve the efficiency and stability of the anode lowers the In addition, in a lithium-sulfur battery using a sulfur-based material as a positive electrode active material, the _{oxidation number of sulfur in lithium polysulfide (Li 2} S _x , x = 8, 6, 4, 2) formed in the positive electrode when the battery is driven High lithium polysulfide (Li ₂ S _x , usually x > 4) has high solubility in the electrolyte, so it continuously dissolves, elutes out of the positive electrode reaction region and moves to the negative electrode. At this time, lithium polysulfide eluted from the positive electrode causes a side reaction with lithium metal, which causes lithium sulfide to adhere to the surface of the lithium metal and causes passivation of the electrode. %, and as the cycle progresses, the capacity and charge/discharge efficiency decrease rapidly, resulting in a low battery lifespan.

To this end, in the prior art, methods such as introducing a protective layer on the surface of the lithium metal anode, changing the composition of the electrolyte solvent, and using additives in the electrolyte were used. It is not preferable for practical application because it causes serious problems.

Accordingly, the present invention provides an electrolyte for a lithium-sulfur battery capable of implementing a lithium-sulfur battery with improved capacity and lifespan characteristics by improving the efficiency and stability of the negative electrode and maximizing the capacity of the positive active material.

Specifically, the electrolyte for a lithium-sulfur battery according to the present invention includes a lithium salt, a non-aqueous organic solvent and an additive, and an alkyl vinyl ether compound as the additive.

In the present invention, the additive is a compound in which a vinyl group and an alkyl group are bonded through an oxygen atom, and since it exhibits a leveling effect due to affinity with lithium ions, improved stripping from the surface of lithium metal as an anode /Plating (stripping/plating) process can be performed. Accordingly, the efficiency and stability of the negative electrode are improved, so that the capacity and lifespan characteristics of a lithium-sulfur battery including the same can be increased. In the present invention, the term “efficiency of the negative electrode” refers to lithium (or other negative of active material). Any deviation from 100% indicates inactive lithium that has lost its utility in charging and discharging the battery.

In addition, the additive of the present invention prevents the lithium polysulfide generated from the positive electrode from reacting with lithium metal and suppresses the loss of sulfur, which is the positive electrode active material, thereby maximizing the capacity expression of the positive electrode active material. A lithium-sulfur battery can be implemented.

In addition, since the additive of the present invention does not participate in the electrochemical reaction of the battery and only serves to improve the efficiency and stability of the negative electrode including lithium metal, the problem of deterioration of battery performance occurring in the prior art does not occur. There is this.

As mentioned above, the additive according to the present invention may comprise an alkyl vinyl ether compound. The alkyl vinyl ether compound may be represented by the following formula (1):

[Formula 1]

(In Formula 1, R is an alkyl group having 1 to 10 carbon atoms).

The alkyl group may be linear or branched, and the number of carbon atoms is not particularly limited, but is preferably 1 to 4. Specific examples include, but are not limited to, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an n-butyl group, a t-butyl group, an isobutyl group, a pentyl group, a hexyl group, a heptyl group, and the like. One or more hydrogen atoms contained in the alkyl group are optionally one or more substituents (eg, alkyl, alkenyl, alkynyl, heterocyclic, aryl, heteroaryl, acyl, oxo, imino, thiooxo, cyano , isocyano, amino, azido, nitro, hydroxyl, thiol, halo, etc.).

The alkyl vinyl ether compound is methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether. ), pentyl vinyl ether (pentyl vinyl ether), and hexyl vinyl ether (hexyl vinyl ether) may include at least one selected from the group consisting of. Preferably, the alkyl vinyl ether compound may be at least one selected from the group consisting of propyl vinyl ether, butyl vinyl ether and pentyl vinyl ether. More preferably, the alkyl vinyl ether compound may be butyl vinyl ether. .

The alkyl vinyl ether compound may be included in an amount of 0.1 to 10% by weight based on 100% by weight of the total electrolyte for a lithium-sulfur battery. The content of the additive may be 0.1% by weight or more, 0.3% by weight or more, or 0.5% by weight, and the upper limit is 10% by weight or less, 2% by weight or less, or 1 wt% or less. The content of the additive may be set by a combination of the lower limit and the upper limit. If the content of the additive is less than the above range, the overall effect on lithium ions moving during charging and discharging cannot be performed, and the uniformity of the stripping/plating process is lowered, so that the desired effect cannot be obtained. Conversely, when the content of the additive exceeds the above range, an overvoltage may occur, which may cause a problem in normal battery operation, resulting in loss of capacity or shortening of battery life.

The electrolyte for a lithium-sulfur battery according to the present invention includes a lithium salt as an electrolyte salt. The type of the lithium salt is not particularly limited in the present invention, and may be used without limitation as long as it can be used in an electrolyte for a lithium-sulfur battery.

For example, the lithium salt is 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, (SO ₂ F) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, It may include at least one selected from the group consisting of chloroborane lithium, lower aliphatic lithium carboxylate having 4 or less carbon atoms, 4-phenyl lithium borate, and lithium imide. Preferably, the lithium salt may be (SO ₂ F) ₂ NLi (lithium bis(fluorosulfonyl)imide; LiFSI).

The concentration of the lithium salt may be appropriately determined in consideration of ionic conductivity, solubility, and the like, and may be, for example, 0.1 to 4.0 M, preferably 0.5 to 2.0 M. When the concentration of the lithium salt is less than the above range, it is difficult to secure ionic conductivity suitable for battery driving. Since the performance of the battery may be deteriorated, it is appropriately adjusted within the above range.

The electrolyte for a lithium-sulfur battery according to the present invention includes a non-aqueous organic solvent as a medium in which ions involved in the electrochemical reaction of the lithium-sulfur battery can move, and this is to dissolve the lithium salt.

In the present invention, the non-aqueous organic solvent includes an ether-based compound and a heterocyclic compound including one or more double bonds.

The ether-based compound maintains solubility in sulfur or a sulfur-based compound while ensuring electrochemical stability within the driving voltage range of the battery, and relatively less occurrence of side reactions with intermediate products according to the driving of the battery.

The ether-based compound may include at least one selected from the group consisting of a linear ether compound and a cyclic ether compound, and may preferably be a linear ether compound.

For example, the linear ether compound may be dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl ether, dimethoxyethane, diethoxyethane, ethylene glycol ethylmethyl ether, diethylene glycol dimethyl Ether, diethylene glycol diethyl ether, diethylene glycol methylethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methylethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol It may include at least one selected from the group consisting of ethylene glycol methylethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, and polyethylene glycol methylethyl ether. Preferably, it may include at least one selected from the group consisting of dimethoxyethane, ethylene glycol ethylmethyl ether and diethylene glycol dimethyl ether, and more preferably dimethoxyethane.

For example, the cyclic ether compound is 1,3-dioxolane, 4,5-dimethyl-dioxolane, 4,5-diethyl-dioxolane, 4-methyl-1,3-dioxolane, 4-ethyl-1 , 3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, 2-ethoxytetrahydrofuran, 2-methyl-1, 3-dioxolane, 2-vinyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-methoxy-1,3-dioxolane, 2-ethyl-2-methyl-1 ,3-dioxolane, tetrahydropyran, 1,4-dioxane, 1,2-dimethoxy benzene, 1,3-dimethoxy benzene, 1,4-dimethoxy benzene and isosorbide dimethyl ether ) may include one or more selected from the group consisting of.

The heterocyclic compound is a heterocyclic compound including one or more double bonds, and the heterocyclic ring includes one or more heteroatoms selected from the group consisting of an oxygen atom and a sulfur atom. The heterocyclic compound includes an oxygen atom or a sulfur atom to exhibit polarity, thereby increasing affinity with other compositions in the electrolyte as well as inhibiting side reactions and decomposition of the electrolyte.

The heterocyclic compound may be a 3 to 15 membered, preferably 3 to 7 membered, more preferably 5 to 6 membered heterocyclic compound.

In addition, the heterocyclic compound is an alkyl group having 1 to 4 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, a halogen group, a nitro group (-NO ₂ ), an amine group (-NH ₂ ) and a sulfonyl group (—SO ₂ ), a heterocyclic compound substituted or unsubstituted with one or more selected from the group consisting of; Or it may be a multi-cyclic compound of at least one selected from the group consisting of a cyclic alkyl group having 3 to 8 carbon atoms and an aryl group having 6 to 10 carbon atoms and a heterocyclic compound.

For example, the heterocyclic compound is 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-ethylthi may contain at least one selected from the group consisting of opene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, and 2,5-dimethylthiophene. have. Preferably, it may include at least one selected from the group consisting of 2-methylfuran, 3-methylfuran and 2,5-dimethylfuran, and more preferably 2-methylfuran.

In the present invention, the non-aqueous organic solvent is 95:5 to 5:95, preferably 95:5 to 50:50, more preferably 90:10 to 50:50 of the ether-based compound and the heterocyclic compound. , most preferably in a volume ratio of 90:10 to 70:30. In the present invention, the volume ratio corresponds to the ratio of “volume% of linear ether”: “volume% of heterocyclic compound” in the ether-based solvent. When the ether-based compound and the heterocyclic compound are included as the non-aqueous organic solvent in the aforementioned volume ratio, it may be effective in preventing loss of a cathode active material and a decrease in ionic conductivity of a lithium-sulfur battery. In particular, the heterocyclic compound is preferably included in an amount of 5 volume or more with respect to the total volume of the non-aqueous organic solvent. When the heterocyclic compound is included in an amount of less than 5 volume ratio with respect to the total volume of the non-aqueous organic solvent, there may be a problem in that life deterioration is accelerated due to elution of the cathode active material.

The lithium-sulfur battery electrolyte of the present invention may further include nitric acid or a nitrite-based compound in addition to the above-described composition. The nitric acid or nitrite-based compound has the effect of forming a stable film on the lithium metal electrode, which is the negative electrode, and improving the charging and discharging efficiency.

The nitric acid or nitrite-based compound is not particularly limited in the present invention, but lithium nitrate (LiNO ₃ ), potassium nitrate (KNO ₃ ), cesium nitrate (CsNO ₃ ), barium nitrate (Ba(NO ₃ ) ₂ ), ammonium nitrate inorganic nitric acid or nitrite compounds such as (NH ₄ NO ₃ ), lithium nitrite (LiNO ₂ ), potassium nitrite (KNO ₂ ), cesium nitrite (CsNO ₂ ), and ammonium nitrite (NH ₄ NO _{2 );} Organic nitric acids such as methyl nitrate, dialkyl imidazolium nitrate, guanidine nitrate, imidazolium nitrate, pyridinium nitrate, ethyl nitrite, propyl nitrite, butyl nitrite, pentyl nitrite, and octyl nitrite or a nitrite compound; One selected from the group consisting of organic nitro compounds such as nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitropyridine, dinitropyridine, nitrotoluene, dinitrotoluene, and combinations thereof is possible, preferably uses lithium nitrate.

In addition, the electrolyte of the present invention may further include other additives for the purpose of improving charge/discharge characteristics, flame retardancy, and the like. Examples of the additive include pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazoli Dinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, fluoroethylene carbonate (FEC), propene sultone (PRS), vinylene carbonate ( VC) and the like.

The electrolyte for a lithium-sulfur battery according to the present invention can improve the efficiency and stability of a negative electrode including lithium metal by including the alkyl vinyl ether compound as an additive. In addition, it is possible to effectively suppress a side reaction between lithium polysulfide and lithium metal generated during driving of an electrolyte or a lithium-sulfur battery. Accordingly, the capacity and lifespan of the lithium-sulfur battery including the electrolyte of the present invention can be improved.

In addition, the present invention provides a lithium-sulfur battery including the electrolyte for the lithium-sulfur battery.

The lithium-sulfur battery includes a positive electrode; cathode; and an electrolyte interposed therebetween, and the lithium-sulfur battery electrolyte according to the present invention as the electrolyte.

The positive electrode may include a positive electrode current collector and a positive electrode active material layer coated on one or both surfaces of the positive electrode current collector.

The positive electrode current collector is not particularly limited as long as it supports the positive electrode active material and has high conductivity without causing a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, a copper or stainless steel surface treated with carbon, nickel, silver, etc., an aluminum-cadmium alloy, etc. may be used.

The positive electrode current collector can form fine irregularities on its surface to enhance bonding strength with the positive electrode active material, and various forms such as a film, a sheet, a foil, a mesh, a net, a porous body, a foam, and a nonwoven body can be used.

The positive electrode active material layer includes a positive electrode active material, and may further include a conductive material, a binder, and an additive.

The positive active material includes sulfur, and specifically, may include at least one selected from the group consisting of _{elemental sulfur (S 8 ) and sulfur compounds.} The positive active material is a group _{consisting of inorganic sulfur, Li 2} S _n (n≥1), a disulfide compound, an organic sulfur compound, and a carbon-sulfur polymer ((C ₂ S _x ) _n , x=2.5 to 50, n≥2) It may include one or more selected from. Preferably, the positive active material may be inorganic sulfur.

In the case of the sulfur, since it does not have electrical conductivity alone, it is used in combination with a conductive material such as carbon material. Accordingly, the sulfur is included in the form of a sulfur-carbon composite, and preferably, the cathode active material may be a sulfur-carbon composite.

The carbon included in the sulfur-carbon composite is a porous carbon material that provides a skeleton in which the sulfur can be uniformly and stably fixed, and compensates for the low electrical conductivity of sulfur so that the electrochemical reaction can proceed smoothly.

The porous carbon material may be generally prepared by carbonizing precursors of various carbon materials. The porous carbon material includes non-uniform pores therein, and the average diameter of the pores is in the range of 1 to 200 nm, and the porosity or porosity may be in the range of 10 to 90% of the total volume of the porous carbon material. If the average diameter of the pores is less than the above range, impregnation of sulfur is impossible because the pore size is only at the molecular level. Not desirable.

The shape of the porous carbon material is spherical, rod-shaped, needle-shaped, plate-shaped, tube-shaped or bulk-shaped, as long as it is conventionally used in lithium-sulfur batteries, and may be used without limitation.

The porous carbon material may have a porous structure or a high specific surface area, as long as it is commonly used in the art. For example, the porous carbon material may include graphite; graphene; carbon black such as denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); carbon fibers such as graphite nanofibers (GNF), carbon nanofibers (CNF), and activated carbon fibers (ACF); It may be at least one selected from the group consisting of graphite and activated carbon such as natural graphite, artificial graphite, and expanded graphite, but is not limited thereto. Preferably, the porous carbon material may be a carbon nanotube.

The sulfur-carbon composite may include sulfur in an amount of 60 to 90 parts by weight, preferably 65 to 85 parts by weight, and more preferably 70 to 80 parts by weight, based on 100 parts by weight of the sulfur-carbon composite. When the sulfur content is less than the above-mentioned range, the specific surface area increases as the content of the porous carbon material in the sulfur-carbon composite is relatively increased, so that the binder content increases when the positive electrode is manufactured. An increase in the amount of the binder used may eventually increase the sheet resistance of the positive electrode and act as an insulator to prevent electron pass, thereby degrading the performance of the battery. Conversely, when the sulfur content exceeds the above-mentioned range, the sulfur, which cannot be combined with the porous carbon material, aggregates with each other or re-elutes to the surface of the porous carbon material, making it difficult to receive electrons and not participating in the electrochemical reaction of the battery. Capacity loss may occur.

In addition, in the sulfur-carbon composite, the sulfur is located on at least one of the inner and outer surfaces of the aforementioned porous carbon material, wherein less than 100%, preferably 1 to 95% of the total inner and outer surfaces of the porous carbon material , more preferably 60 to 90%. When the sulfur is present on the inner and outer surfaces of the porous carbon material within the above range, the maximum effect may be exhibited in terms of electron transport area and wettability with the electrolyte. Specifically, since sulfur is thinly and evenly impregnated on the inner and outer surfaces of the porous carbon material in the above range, it is possible to increase the electron transport contact area in the charge/discharge process. If the sulfur is located in 100% of the entire inner and outer surface of the porous carbon material, the carbon material is completely covered with sulfur, so that the wettability to the electrolyte is reduced and the contact with the conductive material included in the electrode is lowered to prevent electron transfer. They cannot participate in the electrochemical reaction.

The method for preparing the sulfur-carbon composite is not particularly limited in the present invention, and a method commonly used in the art may be used. As an example, a method of simply mixing the sulfur and the porous carbon material and then heat-treating the compound may be used.

The positive active material may further include one or more additives selected from a transition metal element, a group IIIA element, a group IVA element, a sulfur compound of these elements, and an alloy of these elements and sulfur in addition to the composition described above.

Examples of the transition metal element include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Ir, Pt, Au or Hg and the like are included, and the group IIIA elements include Al, Ga, In, Ti, and the like, and the group IVA elements include Ge, Sn, Pb, and the like.

The positive active material may be included in an amount of 40 to 95% by weight, preferably 45 to 90% by weight, more preferably 60 to 90% by weight based on 100% by weight of the total weight of the positive active material layer constituting the positive electrode. When the content of the positive electrode active material is less than the above range, it is difficult to sufficiently exhibit the electrochemical reaction of the positive electrode, and on the contrary, when it exceeds the above range, the content of the conductive material and the binder to be described later is relatively insufficient, and the resistance of the positive electrode increases, There is a problem in that the physical properties of the anode are deteriorated.

The positive electrode active material layer may optionally further include a conductive material for allowing electrons to smoothly move within the positive electrode (specifically, the positive electrode active material) and a binder for well adhering the positive electrode active material to the current collector.

The conductive material electrically connects the electrolyte and the positive electrode active material to serve as a path for electrons to move from the current collector to the positive electrode active material, and may be used without limitation as long as it has conductivity.

For example, the conductive material may include graphite such as natural graphite and artificial graphite; carbon blacks such as Super-P (Super-P), Denka Black, Acetylene Black, Ketjen Black, Channel Black, Furnace Black, Lamp Black, and Summer Black; carbon derivatives such as carbon nanotubes and fullerenes; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; Metal powders, such as aluminum and nickel powder, or conductive polymers, such as polyaniline, polythiophene, polyacetylene, polypyrrole, can be used individually or in mixture.

The conductive material may be included in an amount of 1 to 10% by weight, preferably 4 to 7% by weight, based on 100% by weight of the total positive electrode active material layer constituting the positive electrode. When the content of the conductive material is less than the above range, electron transfer between the positive active material and the current collector is not easy, so that the voltage and capacity decrease. Conversely, if the amount exceeds the above range, the ratio of the positive electrode active material is relatively decreased, and thus the total energy (charge amount) of the battery may decrease. Therefore, it is preferable to determine an appropriate content within the above range.

The binder maintains the positive electrode active material on the positive electrode current collector and organically connects the positive electrode active materials to increase the binding force therebetween, and any binder known in the art may be used.

For example, the binder may include a fluororesin-based binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); a rubber-based binder including styrene-butadiene rubber (SBR), acrylonitrile-butydiene rubber, and styrene-isoprene rubber; Cellulose binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol-based binders; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester-based binders; and a silane-based binder; one selected from the group consisting of, a mixture or copolymer of two or more may be used.

The content of the binder may be 1 to 10% by weight based on 100% by weight of the total of the positive active material layer constituting the positive electrode. If the content of the binder is less than the above range, the physical properties of the positive electrode may be deteriorated, and the positive electrode active material and the conductive material may fall off. It is preferable to determine the appropriate content within the above-mentioned range.

In the present invention, the method for manufacturing the positive electrode is not particularly limited, and a method known by those skilled in the art or various methods for modifying it may be used.

For example, the positive electrode may be prepared by preparing a positive electrode slurry composition including the composition as described above and then applying it to at least one surface of the positive electrode current collector.

The positive electrode slurry composition includes the positive electrode active material, the conductive material, and the binder as described above, and may further include a solvent.

As the solvent, a solvent capable of uniformly dispersing the positive electrode active material, the conductive material, and the binder is used. As the solvent, water is most preferable as an aqueous solvent, and in this case, the water may be distilled water or deionzied water. However, the present invention is not necessarily limited thereto, and if necessary, a lower alcohol that can be easily mixed with water may be used. Examples of the lower alcohol include methanol, ethanol, propanol, isopropanol and butanol, and preferably, these may be used by mixing with water.

The content of the solvent may be contained at a level having a concentration capable of facilitating coating, and the specific content varies depending on the application method and apparatus.

The positive electrode slurry composition may additionally include a material commonly used for the purpose of improving its function in the relevant technical field, if necessary. For example, a viscosity modifier, a fluidizing agent, a filler, etc. are mentioned.

The method for applying the positive electrode slurry composition is not particularly limited in the present invention, and for example, methods such as doctor blade, die casting, comma coating, screen printing, etc. can In addition, after forming on a separate substrate, the positive electrode slurry may be applied on the positive electrode current collector by pressing or lamination.

After the application, a drying process for removing the solvent may be performed. The drying process is performed at a temperature and time at a level sufficient to remove the solvent, and the conditions may vary depending on the type of the solvent, so the present invention is not particularly limited. As an example, drying by hot air, hot air, low humidity air, vacuum drying, (far) infrared rays and a drying method by irradiation with an electron beam, etc. are mentioned. The drying rate is usually adjusted to remove the solvent as quickly as possible within a speed range such that the positive electrode active material layer is not cracked or the positive electrode active material layer is not peeled off from the positive electrode current collector due to stress concentration.

Additionally, the density of the positive electrode active material in the positive electrode may be increased by pressing the current collector after drying. Methods, such as a die press and roll press, are mentioned as a press method.

The porosity of the positive electrode, specifically, the positive electrode active material layer, prepared by the composition and manufacturing method as described above may be 40 to 80%, preferably 60 to 75%. When the porosity of the positive electrode is less than 40%, the filling degree of the positive electrode slurry composition including the positive electrode active material, the conductive material, and the binder is too high, so that sufficient electrolyte to exhibit ionic and/or electrical conduction between the positive electrode active materials is provided. Since it cannot be maintained, the output characteristics or cycle characteristics of the battery may be deteriorated, and there is a problem in that the overvoltage and the discharge capacity of the battery are severely reduced. On the other hand, when the porosity of the positive electrode exceeds 80% and has an excessively high porosity, the physical and electrical connection with the current collector is lowered, so there is a problem that adhesion is lowered and the reaction is difficult. Since there is a problem that the energy density of the lowering can be adjusted appropriately in the above range.

In addition, the sulfur loading in the positive electrode according to the present invention, that is, the mass of sulfur per unit area of the positive electrode active material layer in the positive electrode may be 2 to 15 mg/cm 2 , preferably 2.5 to 5 mg/cm 2 .

The negative electrode may include a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. Alternatively, the negative electrode may be a lithium metal plate.

The negative electrode current collector is for supporting the negative electrode active material layer, as described in the positive electrode current collector.

The anode active material layer may include a conductive material, a binder, etc. in addition to the anode active material. At this time, the conductive material and the binder are as described above.

The negative active material is ^{a material capable of reversibly intercalating or deintercalating lithium (Li +} ), a material capable of reversibly forming a lithium-containing compound by reacting with lithium ions, lithium metal or a lithium alloy. may include

The material capable of reversibly intercalating or deintercalating lithium ions (Li ⁺ ) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material capable of reversibly forming a lithium-containing compound by reacting with the lithium ions (Li ⁺ ) may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy is, 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), and may be an alloy of a metal selected from the group consisting of tin (Sn).

Preferably, the negative active material may be lithium metal, and specifically, may be in the form of a lithium metal thin film or lithium metal powder.

A method of forming the negative active material is not particularly limited, and a method of forming a layer or a film commonly used in the art may be used. For example, a method such as pressing, coating, or vapor deposition may be used. In addition, a case in which a metallic lithium thin film is formed on a metal plate by initial charging after assembling a battery in a state in which there is no lithium thin film in the current collector is included in the negative electrode of the present invention.

The electrolyte is for causing an electrochemical oxidation or reduction reaction in the positive electrode and the negative electrode through this, as described above.

The injection of the electrolyte may be performed at an appropriate stage during the manufacturing process of the lithium-sulfur battery according to the manufacturing process of the final product and required physical properties. That is, it may be applied before assembling the lithium-sulfur battery or in the final stage of assembly.

A separator may be additionally included between the anode and the cathode.

The separator separates or insulates the positive electrode and the negative electrode from each other, and enables lithium ions to be transported between the positive electrode and the negative electrode, and may be made of a porous non-conductive or insulating material. The separator may be used without any particular limitation as long as it is used as a separator in a lithium-sulfur battery. The separator may be an independent member such as a film, or may be a coating layer added to the positive electrode and/or the negative electrode.

As the separator, it is preferable that the electrolyte has low resistance to ion movement and has excellent moisture content to the electrolyte.

The separator may be made of a porous substrate. The porous substrate can be used as long as it is a porous substrate typically used in lithium-sulfur batteries, and a porous polymer film can be used alone or by stacking them, for example, A nonwoven fabric or a polyolefin-based porous membrane made of a melting point glass fiber, polyethylene terephthalate fiber, or the like may be used, but is not limited thereto.

The material of the porous substrate is not particularly limited in the present invention, and any porous substrate commonly used in lithium-sulfur batteries may be used. For example, the porous substrate may include a polyolefin such as polyethylene and polypropylene, a polyester such as polyethyleneterephthalate, and a polybutyleneterephthalate, and a polyamide. (polyamide), polyacetal, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide ( polyphenylenesulfide, polyethylenenaphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, cellulose, nylon (nylon), polyparaphenylene benzobisoxazole (poly(p-phenylene benzobisoxazole) and polyarylate (polyarylate) may include at least one material selected from the group consisting of.

The thickness of the porous substrate is not particularly limited, but may be 1 to 100 μm, preferably 5 to 50 μm. Although the thickness range of the porous substrate is not limited to the above range, when the thickness is excessively thinner than the above-described lower limit, mechanical properties are lowered and the separator may be easily damaged during use of the battery.

The average diameter and pore size of the pores present in the porous substrate are also not particularly limited, but may be 0.001 to 50 μm and 10 to 95%, respectively.

In the lithium-sulfur battery according to the present invention, in addition to winding, which is a general process, lamination, stack, and folding processes of a separator and an electrode are possible.

The shape of the lithium-sulfur battery is not particularly limited and may have various shapes such as a cylindrical shape, a stacked type, and a coin type.

In addition, the present invention provides a battery module including the lithium-sulfur battery as a unit battery.

The battery module may be used as a power source for medium to large devices requiring high temperature stability, long cycle characteristics, and high capacity characteristics.

Examples of the medium-to-large device include a power tool that is powered by an omniscient motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooter); electric golf carts; and a power storage system, but is not limited thereto.

Hereinafter, preferred examples are presented to aid the understanding of the present invention, but the following examples are merely illustrative of the present invention and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that such variations and modifications fall within the scope of the appended claims.

Examples and Comparative Examples

[Example 1]

Sulfur-carbon composite (S:C=75:25 (weight ratio)) 87.5% by weight as a cathode active material, 5.0% by weight of Denka Black as a conductive material, styrene butadiene rubber/carboxymethyl cellulose as a binder (SBR:CMC=70:30 (SBR:CMC=70:30) Weight ratio)) 7.5 wt% was mixed to prepare a positive electrode slurry composition.

A positive electrode was prepared by coating the prepared positive electrode slurry composition on an aluminum current collector having a thickness of 20 μm, drying it at 100° C. for 12 hours, and pressing it with a roll press device. At this time, the loading amount of the positive electrode active material was 3.7 mAh/cm 2 or less, and the porosity of the positive electrode was 70%.

A lithium metal thin film with a thickness of 20 μm was used as the negative electrode.

A solution was prepared by dissolving 0.75 M LiFSI and 1.0 wt% of lithium nitrate in an organic solvent composed of 2-methylfuran and dimethoxyethane (2-methylfuran:DME=1:2 (volume ratio)). Then, an electrolyte was prepared by adding propyl vinyl ether to the solution so as to have a content of 1.0% by weight based on 100% by weight of the total electrolyte.

A lithium-sulfur battery was prepared by placing the prepared positive electrode and the negative electrode to face each other and interposing a polyethylene separator having a thickness of 16 μm and a porosity of 45% therebetween, and then injecting 70 μl of the previously prepared electrolyte.

[Example 2]

A lithium-sulfur battery was prepared in the same manner as in Example 1, except that butyl vinyl ether was used in the same amount instead of propyl vinyl ether.

[Example 3]

A lithium-sulfur battery was prepared in the same manner as in Example 1, except that the content of propyl vinyl ether was changed to 5.0 wt% during the preparation of the electrolyte.

[Example 4]

A lithium-sulfur battery was prepared in the same manner as in Example 1, except that 1.0 wt% of propyl vinyl ether was changed to 5.0 wt% of butyl vinyl ether during electrolyte preparation.

[Example 5]

A lithium-sulfur battery was prepared in the same manner as in Example 1, except that an organic solvent consisting of 2-methylfuran and dimethoxyethane (2-methylfuran:DME=1:1 (volume ratio)) was used in preparing the electrolyte. .

[Comparative Example 1]

A lithium-sulfur battery was prepared in the same manner as in Example 1, except that propyl vinyl ether was not used in preparing the electrolyte.

[Comparative Example 2]

The same as in Example 1, except that an organic solvent composed of 2-methylfuran and dimethoxyethane (2-methylfuran:DME=1:1 (volume ratio)) was used in preparing the electrolyte, and propyl vinyl ether was not used. A lithium-sulfur battery was prepared by the method.

Experimental Example 1. Battery performance evaluation

For the batteries manufactured in Examples and Comparative Examples, performance was evaluated using a charge/discharge measuring device (LAND CT-2001A, manufactured by Wuhan).

Specifically, the initial 2.5 cycles of discharging until it becomes 1.8 V at 25 °C and 0.1 C at 2.5 V are repeated, and then 0.2C/0.2C charge/discharge for 3 cycles, and the Thereafter, charging/discharging at 0.3C/0.5C was repeated up to 100 cycles. The results obtained at this time are shown in Table 1 and FIGS. 1 to 6 .

Discharge capacity per unit weight of positive active material
(mAh/g _sulfur @7 ^th ) Discharge capacity per unit weight of positive active material
(mAh/g _sulfur @50 ^th ) Coulomb Efficiency
(%@50 ^th ) Example 1 819 836 101.9148 Example 2 846 907 101.1765 Example 3 765 646 103.5621 Example 4 771 671 102.3510 Example 5 783 695 104.1258 Comparative Example 1 763 577 104.4849 Comparative Example 2 717 543 104.4624

As shown in FIGS. 1 to 6 and Table 1, in the case of the battery according to the embodiment, it can be confirmed that the capacity and lifespan characteristics are superior to those of the comparative example.

Specifically, referring to Table 1, in the case of the batteries of Examples 1 and 2 using the electrolyte containing the alkyl vinyl ether compound as an additive, the capacity characteristics were 7% and 11% higher, respectively, compared to Comparative Example 1 in the 7th cycle. It can be seen that the difference increases further in the 50th cycle. In addition, when the charging current is normal when the battery is driven, the coulombic efficiency shows a value close to 100%, and when the active material is lost due to lithium polysulfide, the charging capacity becomes larger than the discharge capacity, and thus shows a value far from 100%, Example 1 And it can be seen that the battery according to Comparative Example 1 shows a value of around 100% compared to Comparative Example 1, so that the charge/discharge cycle characteristics are also excellent.

In addition, in the case of the batteries of Examples 1 and 2, compared to Comparative Example 1, the overvoltage is improved during discharging through FIGS. 3 and 6, the battery life is improved through FIGS. 1 and 4, and the cycle through FIGS. 2 and 5 is As it can be seen that the charging and discharging efficiency is improved as the process progresses, it can be seen that the battery according to the present invention exhibits improved capacity, lifespan, and charging/discharging efficiency.

From these results, it can be seen that the lithium-sulfur battery of the present invention can improve the capacity and lifespan characteristics of the lithium-sulfur battery by including an electrolyte including an alkyl vinyl ether compound as an additive.

Claims (16)

Lithium salts, non-aqueous organic solvents and additives,
The additive is an electrolyte for a lithium-sulfur battery comprising an alkyl vinyl ether compound. According to claim 1,
The alkyl vinyl ether compound is represented by the following formula (1), lithium-sulfur battery electrolyte:
[Formula 1]

(In Formula 1, R is an alkyl group having 1 to 10 carbon atoms). According to claim 1,
The alkyl vinyl ether compound comprises at least one selected from the group consisting of methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, pentyl vinyl ether and hexyl vinyl ether, lithium-sulfur electrolyte for batteries. According to claim 1,
The alkyl vinyl ether compound has the effect of improving the efficiency and stability of the negative electrode included in the lithium-sulfur battery, the lithium-sulfur battery electrolyte. According to claim 1,
The non-aqueous organic solvent comprises an ether-based compound and a heterocyclic compound including at least one double bond, a lithium-sulfur battery electrolyte. 6. The method of claim 5,
The ether-based compound comprises a linear ether compound, lithium-sulfur battery electrolyte. 7. The method of claim 6,
The linear ether compound is dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl ether, dimethoxyethane, diethoxyethane, ethylene glycol ethylmethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methylethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methylethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methylethyl An electrolyte for a lithium-sulfur battery comprising at least one selected from the group consisting of ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, and polyethylene glycol methylethyl ether. 6. The method of claim 5,
The heterocyclic compound comprises at least one hetero atom selected from the group consisting of an oxygen atom and a sulfur atom, lithium-sulfur battery electrolyte. 6. The method of claim 5,
The heterocyclic compound is 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- A lithium-sulfur battery comprising at least one selected from the group consisting of propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene and 2,5-dimethylthiophene electrolyte. 6. The method of claim 5,
The non-aqueous organic solvent comprises an ether-based compound and a heterocyclic compound in a volume ratio of 95:5 to 5:95, a lithium-sulfur battery electrolyte. According to claim 1,
The lithium salt is 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, (SO ₂ F) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, chloroborane lithium , Lithium-sulfur battery electrolyte comprising at least one selected from the group consisting of lower aliphatic lithium carboxylates having 4 or less carbon atoms, 4-phenyl lithium borate, and lithium imide. According to claim 1,
The alkyl vinyl ether compound is included in an amount of 0.1 to 10% by weight based on 100% by weight of the total electrolyte for a lithium-sulfur battery, an electrolyte for a lithium-sulfur battery. a positive electrode including a positive active material;
a negative electrode including an anode active material; and
A lithium-sulfur battery comprising the electrolyte according to claim 1 . 14. The method of claim 13,
The cathode active material comprises at least one selected from the group consisting of elemental sulfur and sulfur compounds, a lithium-sulfur battery. 14. The method of claim 13,
The positive active material is a group _{consisting of inorganic sulfur, Li 2} S _n (n≥1), a disulfide compound, an organic sulfur compound, and a carbon-sulfur polymer ((C ₂ S _x ) _n , x=2.5 to 50, n≥2) A lithium-sulfur battery comprising at least one selected from 14. The method of claim 13,
The negative active material includes at least one selected from the group consisting of lithium metal and lithium alloy, a lithium-sulfur battery.

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