Saturated phlodioxin derivative compound and its use as an additive for secondary batteries

Abstract

The present invention relates to a saturated phlodioxine derivative compound and its use as an additive for secondary batteries. More specifically, the present invention relates to a novel compound having a structure in which a substituent is bonded to a saturated phlodioxine skeleton, which, when contained as an additive in a nonaqueous electrolyte composition for secondary batteries (particularly, a nonaqueous electrolyte composition for lithium-sulfur secondary batteries), can solve the problem of lithium polysulfide elution that exists in conventional electrolyte compositions and at the same time realize high capacity retention characteristics for various lithium salts, as well as a method for producing the compound, an electrolyte additive and nonaqueous electrolyte composition containing the compound, and a secondary battery (particularly, a lithium-sulfur secondary battery) containing the electrolyte composition.

Description

[Technical Field]

[0001] The present invention relates to a saturated phlodioxin derivative compound and its use as an additive for secondary batteries. More specifically, the present invention relates to a novel compound having a structure in which a substituent is bonded to a saturated phlodioxin skeleton, which, when contained as an additive in a nonaqueous electrolyte composition for secondary batteries (particularly a nonaqueous electrolyte composition for lithium-sulfur secondary batteries), can solve the problem of lithium polysulfide elution that is present in conventional electrolyte compositions and can also achieve high capacity retention characteristics for various lithium salts. The present invention also relates to a method for producing the compound, an electrolyte additive and nonaqueous electrolyte composition containing the compound, and a secondary battery (particularly a lithium-sulfur secondary battery) containing the electrolyte composition. [Background technology]

[0002] In recent years, the need for large-capacity batteries has increased with the development of portable electronic devices, electric vehicles, and large-capacity power storage systems. Lithium-sulfur secondary batteries are secondary batteries that use a sulfur-based material with S-S bonds (sulfur-sulfur bonds) as the positive electrode active material and lithium metal as the negative electrode active material. Sulfur, the main material for the positive electrode active material, has the advantages of being highly resource-efficient, non-toxic, and light in weight per atom.

[0003] Furthermore, the theoretical discharge capacity of the lithium-sulfur secondary battery is 1,672 mAh / g-sulfur, and the theoretical energy density is 2,600 Wh / kg, which are extremely higher than the theoretical energy densities of other battery systems currently being researched (Ni-MH battery: 450 Wh / kg, Li-FeS battery: 480 Wh / kg, Li-MnO2 battery: 1,000 Wh / kg, Na-S battery: 800 Wh / kg), and it is attracting attention as a battery with high energy density characteristics.

[0004] The most important problem to be solved for the practical use of lithium-sulfur secondary batteries is the reduction in battery life due to the elution of lithium polysulfide. xLithium polysulfides (x = 8, 6, 4, or 2) are intermediates generated during the electrochemical reaction in lithium-sulfur secondary batteries and are highly soluble in organic electrolytes. Lithium polysulfides dissolved in the electrolyte gradually diffuse toward the negative electrode and leak out of the electrochemical reaction zone of the positive electrode, preventing them from participating in the electrochemical reaction at the positive electrode and ultimately resulting in capacity loss. Furthermore, the dissolution of lithium polysulfides increases the viscosity of the electrolyte, reducing ionic conductivity. During continuous charge-discharge reactions, lithium polysulfides react with the negative electrode, which is made of lithium metal, causing lithium sulfide (Li2S) to adhere to the surface of the lithium metal, reducing reaction activity and potential characteristics.

[0005] Most of the research aimed at solving these problems has focused on improving the positive electrode. Specifically, as a method for increasing the conductivity of the electrode, attempts have been made to minimize the decrease in conductivity of the electrode where lithium sulfide accumulates by adding a conductive material made of a carbon material, or to control the generation and accumulation of intermediate products and lithium sulfide by using a sulfur support with a nanostructure (e.g., Patent Documents 1 and 2).

[0006] However, these conventional technologies are difficult to put into practical use, and only a maximum of 70% of the theoretical capacity can be used. Therefore, there is a need to develop a lithium-sulfur secondary battery that can delay the passivation of the electrodes by lithium sulfide and ensure high discharge capacity and lifespan characteristics. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent No. 10-1481234 [Patent Document 2] Korean Patent No. 10-2244915 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to provide a novel compound that, when incorporated as an additive into a nonaqueous electrolyte composition for a secondary battery (particularly a nonaqueous electrolyte composition for a lithium-sulfur secondary battery), can solve the problem of lithium polysulfide elution in conventional nonaqueous electrolytes used in secondary batteries (particularly lithium-sulfur secondary batteries), while improving the stability of lithium electrodes and achieving high capacity retention characteristics; a method for producing the compound; an electrolyte additive and nonaqueous electrolyte composition containing the compound; and a secondary battery (particularly a lithium-sulfur secondary battery) containing the electrolyte composition. [Means for solving the problem]

[0009] The present invention provides a compound represented by the following formula (1):

[0010] [ka] (In the formula, R1 and R2 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C1-C30 alkylene-O-C1-C30 alkyl group, a substituted or unsubstituted C3-C30 heterocycloalkyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted C7-C60 aralkyl group, a substituted or unsubstituted C6-C60 aryloxy group, and a substituted or unsubstituted C6-C60 arylthio group, with the proviso that at least one of R1 and R2 is not a hydrogen atom.)

[0011] In one embodiment of the present invention, the compound represented by the formula (1) may be selected from the group consisting of compounds represented by the following formulas (2) to (4).

[0012] [ka] [ka] [ka] (wherein R3 and R4 are each independently a substituted or unsubstituted C1-C30 alkyl group.)

[0013] More specifically, the compound represented by formula (2) may be selected from the group consisting of compounds represented by the following formulas (2-1) to (2-3): The compound represented by formula (3) is represented by the following formula (3-1) or (3-2): The compound represented by the formula (4) may be represented by the following formula (4-1) or (4-2).

[0014] [ka] [ka] [ka]

[0015] [ka] [ka]

[0016] [ka] [ka]

[0017] Another aspect of the present invention provides a method for producing the compound represented by formula (2), which includes a step of heating dianhydrosugar hexitol-ethylene glycol, a compound in which ethylene glycol is added to both terminal hydroxy groups of a dianhydrosugar hexitol, in the presence of an acid catalyst.

[0018] Yet another aspect of the present invention provides a method for producing a compound represented by formula (3) or (4), which comprises a step of heating a compound represented by the following formula (A) or (B), respectively, with an alkylating agent in the presence of a base catalyst:

[0019] [ka] [ka]

[0020] Yet another aspect of the present invention provides an electrolyte additive containing a compound represented by the formula (1).

[0021] Yet another aspect of the present invention provides a non-aqueous electrolyte composition comprising: a non-aqueous electrolyte solvent; a lithium salt; and an electrolyte additive of the present invention, wherein the content of the electrolyte additive is 0.1 to 10 parts by weight, relative to 100 parts by weight of the total amount of the electrolyte composition.

[0022] Yet another aspect of the present invention provides a secondary battery comprising: a positive electrode; a negative electrode; a separator; and the nonaqueous electrolyte composition of the present invention. [Effects of the Invention]

[0023] When the compound of formula (1) according to the present invention is used as an electrolyte additive in a non-aqueous electrolyte composition for a secondary battery (particularly, a non-aqueous electrolyte composition for a lithium-sulfur secondary battery), the problem of lithium polysulfide elution can be solved, compared with conventional non-aqueous electrolyte compositions, while improving the stability of the lithium electrode, improving the capacity retention rate over cycles, and improving battery life characteristics. This makes it possible to provide a non-aqueous electrolyte composition and a secondary battery (particularly, a lithium-sulfur secondary battery) containing the same.

[0024] Furthermore, according to one embodiment of the present invention, the compound of formula (1) can be produced from a dianhydrosugar hexitol derived from a natural resource. Therefore, by using this compound as an additive for a secondary battery, environmental friendliness in the field of secondary batteries can be improved. BEST MODE FOR CARRYING OUT THE INVENTION

[0025] The present invention will now be described in more detail.

[0026] [Compound of formula (1) and its production method] One aspect of the present invention relates to a compound represented by the following formula (1):

[0027] [ka] (In the formula, R1 and R2 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C1-C30 alkylene-O-C1-C30 alkyl group, a substituted or unsubstituted C3-C30 heterocycloalkyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted C7-C60 aralkyl group, a substituted or unsubstituted C6-C60 aryloxy group, and a substituted or unsubstituted C6-C60 arylthio group, with the proviso that at least one of R1 and R2 is not a hydrogen atom.)

[0028] More specifically, in the formula (1), R1 and R2 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted C3-C12 cycloalkyl group, a substituted or unsubstituted C1-C12 alkylene-O-C1-C12 alkyl group, a substituted or unsubstituted C3-C12 heterocycloalkyl group, a substituted or unsubstituted C6-C20 aryl group, a substituted or unsubstituted C1-C20 heteroaryl group, a substituted or unsubstituted C7-C20 aralkyl group, a substituted or unsubstituted C6-C20 aryloxy group, and a substituted or unsubstituted C6-C20 arylthio group, provided that at least one of R1 and R2 is not a hydrogen atom. More specifically, in the formula (1), R1 and R2 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C2-C6 alkenyl group, a substituted or unsubstituted C2-C6 alkynyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C1-C6 alkylene-O-C1-C6 alkyl group, a substituted or unsubstituted C3-C6 heterocycloalkyl group, a substituted or unsubstituted C6-C10 aryl group, a substituted or unsubstituted C1-C10 heteroaryl group, a substituted or unsubstituted C7-C10 aralkyl group, a substituted or unsubstituted C6-C10 aryloxy group, and a substituted or unsubstituted C6-C10 arylthio group, provided that at least one of R1 and R2 is not a hydrogen atom.

[0029] As used herein, the term "substituted or unsubstituted" for any group means that the group is unsubstituted or substituted with one or more substituents selected from a halogen atom, a C1-C6 alkyl group, or a C1-C6 halogenated alkyl group.

[0030] In one embodiment, the compound represented by formula (1) may be selected from the group consisting of compounds represented by the following formulas (2) to (4).

[0031] [ka] [ka] [ka] (In the formula, R3 and R4 are each independently a substituted or unsubstituted C1-C30 alkyl group, more specifically a substituted or unsubstituted C1-C12 alkyl group, and more specifically a substituted or unsubstituted C1-C6 alkyl group.)

[0032] More specifically, the compound represented by formula (2) may be selected from the group consisting of compounds represented by the following formulas (2-1) to (2-3): The compound represented by formula (3) may be a compound represented by formula (3-1) or (3-2) below: The compound represented by the formula (4) may be a compound represented by the following formula (4-1) or (4-2).

[0033] [ka] [ka] [ka]

[0034] [ka] [ka]

[0035] [ka] [ka] Another aspect of the present invention provides a method for producing a compound represented by formula (2), which includes a step of heating a dianhydrosugar hexitol-ethylene glycol compound in which ethylene glycol is added to both terminal hydroxy groups of a dianhydrosugar hexitol, in the presence of an acid catalyst.

[0036] Anhydrosugar alcohols are generally substances obtained by removing one or more water molecules from compounds obtained by adding hydrogen to the reducing end groups of sugars, commonly known as hydrogenated sugars or sugar alcohols. Dianhydrosugar hexitols are anhydrosugar alcohols formed by removing two water molecules from the inside of a hexitol. They have a diol form with two hydroxy groups in the molecule and can be produced using hexitols derived from starch.

[0037] In one embodiment, the dianhydrosugar hexitol may be a 1,4:3,6-dianhydrohexitol, and more specifically may be isosorbide, isomannide, isoidide, or a mixture of two or more thereof.

[0038] In one embodiment, the dianhydrosugar hexitol-ethylene glycol may be prepared by an addition reaction of a dianhydrosugar hexitol with ethylene oxide having the following structure:

[0039] [Ethylene oxide] [ka]

[0040] In one embodiment, the addition reaction of the dianhydrosugar hexitol with ethylene oxide can be carried out, for example, at a temperature of 100°C or higher, more specifically, 100°C to 140°C, for 1 hour or longer, more specifically, 1 hour to 5 hours, but is not limited thereto.

[0041] In one embodiment, the addition reaction of the dianhydrosugar hexitol with ethylene oxide can be carried out using 2 or more moles of ethylene oxide per mole of the dianhydrosugar hexitol.

[0042] More specifically, in the addition reaction between the dianhydrosugar hexitol and ethylene oxide, the amount of ethylene oxide per mole of the dianhydrosugar hexitol may be 2 moles or more, 3 moles or more, 4 moles or more, or 5 moles or more, and may be 25 moles or less, 20 moles or less, 15 moles or less, or 10 moles or less. If the amount of ethylene oxide used per mole of the dianhydrosugar hexitol in the addition reaction between the dianhydrosugar hexitol and ethylene oxide is less than 2 moles, it may not be possible to produce the compound of formula (1), whereas if it exceeds 25 moles, the production cost may increase, resulting in reduced economic efficiency.

[0043] In one embodiment, the compound represented by formula (2-1) can be produced by heating an addition reaction product of 1 mole of isosorbide with 2 moles or more of ethylene oxide in the presence of an acid catalyst.

[0044] In one embodiment, the compound represented by formula (2-2) can be produced by heating an addition reaction product of 1 mole of isomannide with 2 moles or more of ethylene oxide in the presence of an acid catalyst.

[0045] In one embodiment, the compound represented by formula (2-3) can be produced by heating an addition reaction product of 1 mole of isoidide with 2 moles or more of ethylene oxide in the presence of an acid catalyst.

[0046] In one embodiment, the acid catalyst may be an inorganic acid or an organic acid catalyst, and more specifically may be selected from, but not limited to, sulfuric acid, hydrochloric acid, hydrobromic acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, or a combination thereof.

[0047] In one embodiment, the amount of the acid catalyst used in the addition reaction of the dianhydrosugar hexitol with ethylene oxide may be, for example, 0.01 part by weight or more, 0.02 part by weight or more, or 0.05 part by weight or more, and may be 5 parts by weight or less, 2 parts by weight or less, or 1 part by weight or less, relative to 100 parts by weight of the dianhydrosugar hexitol, but is not limited to these.

[0048] Yet another aspect of the present invention provides a method for producing a compound represented by formula (3) or (4), which comprises a step of heating a compound represented by the following formula (A) or (B), respectively, with an alkylating agent in the presence of a base catalyst:

[0049] [ka] [ka] In one embodiment, the alkylating agent can be selected from, but is not limited to, an alkyl halide having the formula RX, where R is a substituted or unsubstituted C1-C30 alkyl group (more specifically, a substituted or unsubstituted C1-C12 alkyl group, even more specifically, a substituted or unsubstituted C1-C6 alkyl group), and X is a halogen atom (e.g., F, Cl, Br, or I), an aromatic sulfonate having a substituted or unsubstituted C1-C30 alkyl group, or a combination thereof.

[0050] More specifically, the alkyl halide may be methyl iodide, and the aromatic sulfonate having a substituted or unsubstituted C1-C30 alkyl group may be, but is not limited to, a toluenesulfonate having a C1-C30 alkyl group substituted with a halogen atom (e.g., F).

[0051] In one embodiment, the base catalyst may be selected from an inorganic base catalyst, an organic base catalyst, or a combination thereof, and more specifically, may be selected from, but is not limited to, sodium hydride, hydrogen iodide, hydrogen sulfide, aluminum hydride, or a combination thereof.

[0052] In one embodiment, the amount of the base catalyst used in the reaction of the compound represented by Formula (A) or (B) with the alkylating agent may be, for example, 1 part by weight or more, 2 parts by weight or more, or 5 parts by weight or more, and may be 80 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, relative to 100 parts by weight of the compound of Formula (A) or (B), but is not limited to these.

[0053] In one embodiment, the reaction of the compound represented by Formula (A) or (B) with the alkylating agent can be carried out, for example, but not limited to, at a temperature of 40°C or higher, more specifically, 40°C to 80°C, for 5 hours or longer, more specifically, 5 hours to 15 hours.

[0054] According to one embodiment of the present invention, the compound represented by formula (1) can be effectively used as an electrolyte additive in a nonaqueous electrolyte composition for a secondary battery, particularly a nonaqueous electrolyte composition for a lithium-sulfur secondary battery. This will be described later as another aspect of the present invention. However, the use of the compound of the present invention is by no means limited thereto, and the compound represented by formula (1) can be used for various applications other than such electrolyte additives for secondary batteries (e.g., surfactants, penetration enhancers for cosmetic active ingredients, antibacterial agents, etc.).

[0055] [Electrolyte additive and non-aqueous electrolyte composition] Yet another aspect of the present invention relates to an electrolyte additive containing the compound represented by the formula (1).

[0056] In one embodiment, the electrolyte additive may consist solely of the compound represented by formula (1).

[0057] In one embodiment, the electrolyte additive may further include one or more components other than the compound represented by formula (1). As such additional components, components that can be used as additives for secondary batteries can be used without particular limitation.

[0058] More specifically, the electrolyte additive may further contain a nitric acid (or nitrite)-based compound as a component other than the compound represented by formula (1). Such a nitric acid (or nitrite)-based compound can form a stable coating on the negative electrode (lithium-containing electrode) of a lithium-sulfur secondary battery, thereby improving charge / discharge efficiency.

[0059] In one embodiment, the nitric acid (or nitrite) based compound may be selected from the group consisting of, but not limited to, inorganic nitrate compounds (e.g., lithium nitrate (LiNO) and lithium nitrite (LiNO)), organic nitrate compounds (e.g., nitromethane (CHNO), methyl nitrate (CHNO)), or mixtures thereof.

[0060] In one embodiment, when the electrolyte additive contains the compound represented by formula (1) and other components (e.g., the nitric acid (or nitrite)-based compound), the content of the other components may be 0.1 to 2 parts by weight, more specifically, 0.1 parts by weight or more, 0.2 parts by weight or more, or 0.3 parts by weight or more, or may be 2 parts by weight or less, 1.8 parts by weight or less, or 1.5 parts by weight or less, relative to 1 part by weight of the compound represented by formula (1) contained in the electrolyte additive, but is not limited thereto.

[0061] Yet another aspect of the present invention relates to a non-aqueous electrolyte composition comprising: a non-aqueous electrolyte solvent; a lithium salt; and the electrolyte additive of the present invention; wherein the content of the electrolyte additive is 0.1 to 10 parts by weight relative to 100 parts by weight of the total amount of the electrolyte composition.

[0062] If the content of the electrolyte additive is less than 0.1 parts by weight relative to 100 parts by weight of the total amount of the nonaqueous electrolyte composition of the present invention, the effect of improving the life retention rate (or capacity retention rate) of a lithium-sulfur secondary battery may be insufficient when such an electrolyte composition is used. Conversely, if the content of the electrolyte additive exceeds 10 parts by weight, the coating may become thick, resulting in increased resistance and a decrease in the life retention rate (or capacity retention rate) of a lithium-sulfur secondary battery.

[0063] More specifically, the content of the electrolyte additive relative to 100 parts by weight of the total amount of the nonaqueous electrolyte composition of the present invention may be 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, or 1.2 parts by weight or more, and may be 10 parts by weight or less, 9.5 parts by weight or less, 9 parts by weight or less, or 8.9 parts by weight or less.

[0064] The non-aqueous electrolyte solvent contained in the non-aqueous electrolyte composition of the present invention functions as a medium in which ions involved in the electrochemical reaction of the lithium-sulfur secondary battery can move.

[0065] In one embodiment, the non-aqueous electrolyte solvent may be a linear ether, a cyclic ether, or a combination thereof.

[0066] In one embodiment, the non-aqueous electrolyte solvent may be, for example, dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, diisobutyl ether, ethyl methyl ether, ethyl propyl ether, ethyl tert-butyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, dimethoxypropane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethyl glycol dimethyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol dimethyl ether, butylene glycol ether, or diethylene glycol dimethyl ether. The alkyl ether is selected from the group consisting of, but not limited to, glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, diethylene glycol tert-butyl ethyl ether, ethylene glycol ethyl methyl ether, dioxolane, methyl dioxolane, dimethyl dioxolane, vinyl dioxolane, methoxy dioxolane, ethyl methyl dioxolane, oxane, dioxane, trioxane, tetrahydrofuran, methyl tetrahydrofuran, dimethyl tetrahydrofuran, dimethoxy tetrahydrofuran, ethoxy tetrahydrofuran, dihydropyran, tetrahydropyran, furan, methyl furan, isosorbide dimethyl ether or mixtures thereof.

[0067] In one embodiment, the lithium salt contained in the nonaqueous electrolyte composition of the present invention is selected from the group consisting of, but not limited to, LiSCN, LiBr, LiI, LiPF6, LiBF4, LiSbF6, LiAsF6, LiCH3SO3, LiCF3SO3, LiClO4, LiBPh4, LiC(CF3SO2)3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(SFO2)2, LiN(CF3CF2SO2)2, Li2S, LiSn (where n = an integer of 1 to 8), or a mixture thereof, where Ph means phenyl.

[0068] In one embodiment, the molar concentration of the lithium salt in the nonaqueous electrolyte composition of the present invention may be 0.5 M to 5 M. If the molar concentration of the lithium salt in the electrolyte composition is less than 0.5 M, the capacity retention rate may decrease, and conversely, if it exceeds 5 M, the lithium salt may leach out, reducing the economic efficiency, which is not preferable.

[0069] More specifically, the molar concentration of the lithium salt in the nonaqueous electrolyte composition of the present invention may be 0.5 M or more, 0.6 M or more, 0.7 M or more, 0.8 M or more, 0.9 M or more, or 1 M or more, and may be 5 M or less, 4.8 M or less, 4.6 M or less, 4.4 M or less, or 4.2 M or less.

[0070] [Secondary battery] Yet another aspect of the present invention relates to a secondary battery (particularly a lithium-sulfur secondary battery) comprising a positive electrode, a negative electrode, a separator, and the nonaqueous electrolyte composition of the present invention.

[0071] In one embodiment, the secondary battery of the present invention includes a positive electrode and a negative electrode arranged opposite each other; a separator provided between the positive electrode and the negative electrode; and a non-aqueous electrolyte composition according to the present invention impregnated in the positive electrode, the negative electrode, and the separator and having ion conductivity.

[0072] The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0073] The positive electrode current collector may be any material that can be used as a current collector in this technical field, and specifically, it is preferable to use foamed aluminum, foamed nickel, or the like, which have good electrical conductivity.

[0074] The positive electrode active material layer may contain, as a positive electrode active material, elemental sulfur (S), a sulfur-based compound, or a mixture thereof. Specific examples of the sulfur-based compound include Li2Sn (n=1), an organic sulfur compound, or a carbon-sulfur polymer (C2S x ) n :x=2.5~50, n=2).

[0075] Since such sulfur-based materials are not electrically conductive by themselves, the positive electrode active material layer is made of a conductive material.

[0076] The conductive material may be porous. Thus, any conductive material may be used without limitation as long as it is porous and conductive. For example, a porous carbon-based material may be used. Examples of such carbon-based materials include carbon black, graphite, graphene, activated carbon, and carbon fiber. Other examples include metallic fibers such as metal mesh, metallic powders of copper, silver, nickel, and aluminum, and organic conductive materials such as polyphenylene derivatives. The conductive materials may be used alone or in combination.

[0077] In an embodiment, the positive electrode active material layer may further include a binder to improve bonding between the positive electrode active material and the conductive material and between the positive electrode active material layer and the positive electrode current collector.

[0078] The binder may include a thermoplastic resin or a thermosetting resin, such as polyethylene, polyethylene oxide, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, or ethylene-acrylic acid copolymer, which may be used alone or in combination, but is not limited thereto, and any binder usable in the art may be used.

[0079] The positive electrode can be manufactured by a conventional method. Specifically, the positive electrode active material layer-forming composition is prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent. The resulting mixture is then applied to a positive electrode current collector, dried, and optionally, compression-molded onto the positive electrode current collector to improve electrode density. In this case, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and that is easily evaporated. Specifically, the organic solvent can be selected from acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, or a combination thereof.

[0080] The negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, or may be a lithium metal plate alone.

[0081] The negative electrode current collector is for supporting the negative electrode active material and is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of a lithium metal battery. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, or the like, an aluminum-cadmium alloy, or the like can be used.

[0082] The negative electrode current collector may have fine irregularities on its surface to strengthen the bonding force with the negative electrode active material layer, and may be used in various forms such as a film, a sheet, a wheel, a mesh, a net, a porous body, a foam, or a nonwoven fabric.

[0083] The negative electrode active material layer contains lithium ions (Li + The lithium ion-containing compound may include a material capable of reversibly intercalating or deintercalating lithium ions; a material capable of reacting with lithium ions to reversibly form a lithium-containing compound; lithium metal; or a lithium alloy.

[0084] The lithium ion (Li + The material capable of reversibly absorbing and releasing lithium ions (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The material capable of reacting with lithium (Li) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of 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 tin (Sn).

[0085] In a preferred embodiment, the negative electrode active material may be lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0086] The method for forming the negative electrode active material layer is not particularly limited, and any layer or film forming method conventionally used in this technical field can be used. For example, methods such as compression, coating, and vapor deposition can be used. The negative electrode of the present invention also includes a case where a battery is assembled without forming a thin lithium film on the negative electrode current collector, and a thin lithium metal film is formed on the metal plate by initial charging.

[0087] The nonaqueous electrolyte composition of the present invention is the same as described above, contains lithium ions, and is intended to cause an electrochemical oxidation reaction or reduction reaction between the positive electrode and the negative electrode via the lithium ions.

[0088] The nonaqueous electrolyte composition may be injected at an appropriate step during the manufacturing process of the electrochemical device depending on the manufacturing process and required properties of the final product, i.e., it may be applied before assembling the electrochemical device or in the final step of assembling the electrochemical device.

[0089] A separator may be further included between the positive electrode and the negative electrode. The separator serves to physically separate the two electrodes in the secondary battery (particularly, the lithium-sulfur secondary battery) of the present invention, and any separator conventionally used in secondary batteries (particularly, the lithium-sulfur secondary battery) may be used without any particular limitation. In particular, it is preferable to use a separator that has low ion transfer resistance in the electrolyte composition and good impregnation (humidification) with the electrolyte composition.

[0090] The separation membrane may be made of any porous material, and any porous material that has been conventionally used in electrochemical elements may be used. For example, a porous membrane or a nonwoven fabric may be used, but is not particularly limited thereto.

[0091] Specific examples of the porous film include polyolefin-based porous film.The polyolefin-based porous film can be a film formed by using polyolefin-based polymers such as polyethylene (for example, high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, etc.), polypropylene, polybutylene and polypentene alone, or can be a film formed by mixing these polymers.

[0092] The nonwoven fabric may be a polyolefin-based nonwoven fabric, or may be a nonwoven fabric formed using, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, etc. alone or a polymer mixture thereof. The structure of the nonwoven fabric may be a spunbonded nonwoven fabric or a meltblown nonwoven fabric made of long fibers.

[0093] The thickness of the porous material is not particularly limited, but may be 1 to 100 μm, preferably 5 to 50 μm.

[0094] The size and porosity of the pores present in the porous material are not particularly limited, but may be 0.001 to 50 μm and 10 to 95%, respectively.

[0095] The secondary battery (especially the lithium-sulfur secondary battery) according to the present invention can be manufactured by a process of laminating a separator and an electrode, stacking them, and folding them, in addition to a general winding process.

[0096] The shape of the secondary battery is not particularly limited, and the secondary battery can be manufactured in various shapes such as a cylindrical shape, a laminated shape, and a coin shape.

[0097] The present invention will be described in more detail below with reference to examples and comparative examples, but the scope of the present invention is not limited thereto. Example

[0098] <Production of dianhydrosugar hexitol-ethylene glycol> In the following example of the preparation of dianhydrosugar hexitol-ethylene glycol, the stoichiometric addition reaction scheme of dianhydrosugar hexitol (isosorbide) and ethylene oxide is as follows:

[0099] [ka] (In the formula, m=1, n=1)

[0100] Preparation Example A1: Addition reaction using 5 moles of ethylene oxide to 1 mole of isosorbide A pressurizable reactor was charged with 146 g of isosorbide and 0.15 g of phosphoric acid (85%) as an acid component. The reactor was then purged with nitrogen and heated to 100°C. The pressure was reduced under vacuum to remove moisture from the reactor. Next, 88 g of ethylene oxide was slowly added, and the reaction was carried out at a temperature of 100°C to 140°C for 2 to 3 hours. The reaction temperature was controlled so that it did not exceed 140°C. The reactor was then cooled to 50°C, 0.3 g of potassium hydroxide was added, the reactor was purged with nitrogen, the temperature was increased to 100°C, and the pressure was reduced under vacuum to remove moisture from the reactor. Next, 132 g of ethylene oxide was slowly added, and the reaction was carried out at 100°C to 140°C for 2 to 3 hours. After the reaction was complete, the reactor was cooled to 50°C, 4.0 g of Ambosol MP20 was added as an adsorbent, and the mixture was reheated and stirred at 100-120°C for 1-5 hours to remove the metal ions. The atmosphere in the reactor was replaced with nitrogen or reduced in pressure under vacuum. After confirming that no metal ions were detected, the reactor was cooled to 60-90°C, and residual by-products were removed, yielding 362 g of a transparent liquid addition reaction product.

[0101] Preparation Example A2: Addition reaction using 10 moles of ethylene oxide to 1 mole of isosorbide The same method as in Production Example A1 was carried out, except that the amount of ethylene oxide added in the second run was changed from 132 g to 352 g, to obtain 551 g of a transparent liquid addition reaction product.

[0102] Preparation Example A3: Addition reaction using 2 moles of ethylene oxide to 1 mole of isosorbide The same method as in Production Example A1 was carried out, except that the amount of ethylene oxide added in the first run was changed from 88 g to 44 g and the amount added in the second run was changed from 132 g to 44 g, and 227 g of a transparent liquid addition reaction product was obtained.

[0103] <Production of the compound of formula (2)> In the following compound preparation examples, the reaction scheme for producing the target compound ((4aR,5R,7aR)-5-[(2S)-1,4-dioxan-2-yl]-2,3,4a,5,7,7a-hexahydrofuro[3,4-b][1,4]dioxine) from dianhydrosugar hexitol-ethylene glycol is as follows:

[0104] [ka] (In the formula, m=1, n=1)

[0105] Example A1: Preparation of target compound using addition reaction product of Preparation Example A1 200 g of the addition reaction product obtained in Preparation Example A1 and 5 g of sulfuric acid were added to a three-neck glass reactor in which a vacuum pump and a micro-sublimator were connected in series, and the reaction was carried out while heating to 130°C. After heating and stirring for 1 hour, the pressure was slowly reduced to 50 mbar with a vacuum pump, decomposition gases and 1,4-dioxane were removed, and 35 g of the target compound was obtained as needle-like crystals using a micro-sublimator. The analytical results of the target compound obtained are as follows: 1 H NMR (400 MHz, CDCl3): d 4.39 (td, J = 8.6, 4.0 Hz, 1H), 4.18 (t, J = 8.6 Hz, 1H), 3.96 (m, 1H), 3.96-3.83 (m, 5H), 3.81-3.74 (m, 3H), 3.71 (m, 1H), 3.66-3.58 (m, 2H), 3.50 (m, 1H), 3.33 (m, 1H). 13 C NMR (100 MHz, CDCl3): d 80.1, 74.7, 73.9, 72.4, 67.3, 66.6, 66.3, 64.6, 64.4, 59.6. Mass (ESI): 217.10 (M+1).

[0106] Example A2: Preparation of target compound using addition reaction product of Preparation Example A2 The same procedure as in Example A1 was carried out, except that 200 g of the addition reaction product obtained in Preparation Example A2 was used instead of the addition reaction product obtained in Preparation Example A1, to obtain 19 g of the target compound as needle crystals. The analytical results of the target compound obtained were the same as in Example A1.

[0107] Example A3: Preparation of target compound using addition reaction product of Preparation Example A3 The same procedure as in Example A1 was carried out, except that 200 g of the addition reaction product obtained in Preparation A3 was used instead of the addition reaction product obtained in Preparation A1, to obtain 12 g of the target compound as needle-like crystals. The analytical results of the target compound obtained were the same as in Example A1.

[0108] <Production of Compound of Formula (3-1)> Example A4: Preparation of target compound using monohydroxyflodioxin In the following compound preparation examples, the reaction scheme for producing the target compound of formula (3-1) (5-(methoxymethyl)hexahydrofuro[3,4-b][1,4]dioxine) from monohydroxyfurodioxine is as follows:

[0109] [ka] A 1,000 mL flask was charged with 400 mL of tetrahydrofuran, 80 g of the starting material ([hexahydrofuro[3,4-b][1,4]dioxin-5-yl]methanol) and 36 g of sodium hydride, and the flask was maintained at 0°C for 10 minutes. After stirring at 0°C for 30 minutes, 90 g of methyl iodide was added, the mixture was heated to 60°C, and the reaction was carried out with stirring for 12 hours. After completion of the reaction, the resulting mixture was filtered and dried under vacuum to obtain 56 g of the target compound of formula (3-1) (5-(methoxymethyl)hexahydrofuro[3,4-b][1,4]dioxin). 1H NMR (400 MHz, DMSO-d6): d 4.80 (td, 1H), 4.51 (t, 1H), 4.00-3.75 (m, 2H), 3.76-3.66 (m, 4H), 3.75 (m, 1H), 3.60-3.35 (m, 2H), 3.23 (s, 3H). 13 C NMR (100 MHz, DMSO-d6): d 91.1, 89.6, 86.1, 72.0, 62.7, 61.4, 61.1, 59.6. Mass (ESI): 174.2 (M+1).

[0110] <Production of Compound of Formula (3-2)> Example A5: Preparation of target compound using monohydroxyflodioxin The same method as in Example A4 was carried out except that 120 g of 2,2,2-trifluoroethyl p-toluenesulfonate was used instead of 90 g of methyl iodide, thereby obtaining 82 g of the target compound of the formula (3-2) (5-((2,2,2-trifluoroethoxy)methyl)hexahydrofuro[3,4-b][1,4]dioxine). 1 H NMR (400 MHz, DMSO-d6): d 4.80 (td, 1H), 4.51 (td, 1H), 4.00-3.75 (m, 2H), 3.76-3.66 (m, 4H), 3.75 (m, 1H), 3.60-3.35 (m, 2H), 3.23 (s, 2H). 13 C NMR (100 MHz, DMSO-d6): d 128.5, 123.5, 91.1, 89.6, 86.1, 62.7, 61.4, 61.1, 51.6. Mass (ESI): 242.2 (M+1).

[0111] <Production of Compound of Formula (4-1)> Example A6: Preparation of target compound using dihydroxyflodioxin The same method as in Example A4 was carried out, except that 90 g of 2,5-anhydro-3,4-O-(1,2-ethanediyl)mannitol was used instead of 80 g of [hexahydrofuro[3,4-b][1,4]dioxin-5-yl]methanol as the starting material, to obtain 66 g of the target compound of formula (4-1) (5,7-bis(methoxymethyl)hexahydrofuro[3,4-b][1,4]dioxin). 1 H NMR (400 MHz, DMSO-d6): d 4.80 (td, 2H), 3.75 (m, 2H), 3.76-3.66 (m, 4H), 3.60-3.35 (m, 4H), 3.23 (s, 6H). 13 C NMR (100 MHz, DMSO-d6): d 88.9, 82.1, 72.3, 61.4, 59.6. Mass (ESI): 218.26 (M+1).

[0112] <Production of Compound of Formula (4-2)> Example A7: Preparation of target compound using dihydroxyflodioxin The same method as in Example A4 was carried out, except that 90 g of 2,5-anhydro-3,4-O-(1,2-ethanediyl)mannitol was used instead of 80 g of [hexahydrofuro[3,4-b][1,4]dioxin-5-yl]methanol and 120 g of 2,2,2-trifluoroethyl p-toluenesulfonate were used instead of 90 g of methyl iodide as starting materials, to obtain 83 g of the target compound of formula (4-2) (5,7-bis((2,2,2-trifluoroethoxy)methyl)hexahydrofuro[3,4-b][1,4]dioxin). 1 H NMR (400 MHz, DMSO-d6): d 4.92 (dd, 4H), 4.80 (td, 2H), 3.75 (m, 2H), 3.76-3.66 (m, 4H), 3.60-3.35 (m, 4H), 3.23 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 128.5, 121.6, 88.9, 82.1, 72.3, 61.4, 51.9. Mass (ESI): 354.25 (M+1).

[0113] <Production of non-aqueous electrolyte composition> Example B1: Preparation of an electrolyte composition containing 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A1 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A1 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0114] Example B2: Preparation of an electrolyte composition containing 4.5 parts by weight of LiNO3 and 4.4 parts by weight of the target compound obtained in Example A2 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 4.2 M LiN(CF3SO2)2 was mixed with 4.5 parts by weight of LiNO3 as an additive and 4.4 parts by weight of the target compound obtained in Example A2 relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0115] Example B3: Preparation of an electrolyte composition containing 1 part by weight of CH3NO3 and 4.3 parts by weight of the target compound obtained in Example A3 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 1.0 parts by weight of CH3NO3 as an additive and 4.3 parts by weight of the target compound obtained in Example A3 relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0116] Example B4: Preparation of an electrolyte composition containing, as additives, 0.5 parts by weight of LiNO2 and 0.7 parts by weight of the target obtained in Example A1 An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 0.4 M LiPF6 was mixed with 0.5 parts by weight of LiNO2 and 0.7 parts by weight of the target compound obtained in Example A1 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of electrolyte composition.

[0117] Example B5: Preparation of an electrolyte composition containing 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A1 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting solely of 1,2-dimethoxyethane and 1.0 M LiN(CFSO) was mixed with 1 part by weight of LiNO and 2 parts by weight of the target compound obtained in Example A1 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0118] Example B6: Preparation of an electrolyte composition containing 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A1 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of tetraethyl glycol dimethyl ether and 1,3-dioxolane (volume ratio = 25:75) and 1.0 M LiN(CF3SO2)2 was mixed with 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A1 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0119] Example B7: Preparation of an electrolyte composition containing 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A4 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A4 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0120] Example B8: Preparation of an electrolyte composition containing 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A5 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A5 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0121] Example B9: Preparation of an electrolyte composition containing 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A6 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A6 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0122] Example B10: Preparation of an electrolyte composition containing 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A7 as additives An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 1 part by weight of LiNO3 and 2 parts by weight of the target compound obtained in Example A7 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of electrolyte composition.

[0123] Comparative Example B1: Preparation of an electrolyte composition containing only 1 part by weight of LiNO3 as an additive An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 1 part by weight of LiNO3 as an additive relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0124] Comparative Example B2: Preparation of an electrolyte composition containing 0.09 parts by weight of additive (0.04 parts by weight of LiNO3 + 0.05 parts by weight of the target compound obtained in Example A1) An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 0.04 parts by weight of LiNO3 as an additive and 0.05 parts by weight of the target compound obtained in Example A1 relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0125] Comparative Example B3: Preparation of an electrolyte composition containing 10.1 parts by weight of additive (35.5 parts by weight of LiNO + 4.6 parts by weight of the target compound obtained in Example A1) An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 5.5 parts by weight of LiNO3 and 4.6 parts by weight of the target compound obtained in Example A1 as additives relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0126] Comparative Example B4: Preparation of an electrolyte composition containing 0.09 parts by weight of additive (0.04 parts by weight of LiNO3 + 0.05 parts by weight of the target compound obtained in Example A4) An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 0.04 parts by weight of LiNO3 as an additive and 0.05 parts by weight of the target compound obtained in Example A4 relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0127] Comparative Example B5: Preparation of an electrolyte composition containing 10.1 parts by weight of additive (35.5 parts by weight of LiNO + 4.6 parts by weight of the target compound obtained in Example A5) An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 5.5 parts by weight of LiNO3 as an additive and 4.6 parts by weight of the target compound obtained in Example A5 relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0128] Comparative Example B6: Preparation of an electrolyte composition containing 0.09 parts by weight of additive (0.04 parts by weight of LiNO3 + 0.05 parts by weight of the target compound obtained in Example A6) An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 0.04 parts by weight of LiNO3 as an additive and 0.05 parts by weight of the target compound obtained in Example A6 relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0129] Comparative Example B7: Preparation of an electrolyte composition containing 10.1 parts by weight of additive (35.5 parts by weight of LiNO + 4.6 parts by weight of the target compound obtained in Example A7) An electrolyte solution containing a non-aqueous electrolyte solvent consisting of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio = 50:50) and 1.0 M LiN(CF3SO2)2 was mixed with 5.5 parts by weight of LiNO3 as an additive and 4.6 parts by weight of the target compound obtained in Example A7 relative to 100 parts by weight of the total amount of the electrolyte composition to produce 10 mL of the electrolyte composition.

[0130] <Manufacturing lithium-sulfur secondary batteries> Examples C1 to C10 and Comparative Examples C1 to C7 A composition for forming a positive electrode active material layer was prepared by mixing 65 parts by weight of sulfur, 25 parts by weight of carbon black, and 10 parts by weight of polyethylene tellurene oxide with acetonitrile. The total content of sulfur, carbon black, and polyethylene oxide was 100 parts by weight. The composition for forming a positive electrode active material layer was coated on an aluminum current collector and dried to prepare a positive electrode. A 450 μm-thick lithium metal was used for the negative electrode. The prepared positive electrode and negative electrode were placed opposite each other, and a polypropylene separator was placed between them. The obtained electrolyte compositions of Examples B1 to B10 and Comparative Examples B1 to B7 were filled therein to prepare lithium-sulfur secondary batteries of Examples C1 to C10 and Comparative Examples C1 to C7.

[0131] <Charge-discharge characteristics analysis of lithium-sulfur secondary batteries> The charge-discharge characteristics of the lithium-sulfur secondary batteries of Examples C1 to C10 and Comparative Examples C1 to C7 were measured by the following method, and the results are shown in Table 1 below.

[0132] Life evaluation at room temperature (discharge capacity) The lithium-sulfur secondary batteries fabricated in the examples and comparative examples were evaluated for their lifespan at room temperature. Specifically, the fabricated lithium-sulfur secondary batteries were discharged to 1.8 V at room temperature (25°C) at a constant current of 0.36 mA, and then charged at a constant current of 0.36 mA for 10 minutes after discharge completion until the operating voltage reached 2.7 V. One charge and one discharge constitute one cycle, and the capacity retention rate (lifespan retention rate) relative to the initial charge capacity at room temperature was measured over 100 charge / discharge cycles.

[0133] [Table 1-1] [Table 1-2]

[0134] As shown in Table 1, in the case of secondary batteries using the electrolyte compositions of Examples B1 to B10 according to the present invention, the additive containing the compound of formula (1) of the present invention was contained in the amount specified in the present invention, and therefore the life retention rate (capacity retention rate) was extremely high, at 90.0% or more, regardless of the type of lithium salt.

[0135] However, in the case of a secondary battery using the electrolyte composition of Comparative Example B1, which does not contain the compound of formula (1) of the present invention, the life retention rate was poor at 64.2%; in the case of secondary batteries using the electrolyte compositions of Comparative Examples B2, B4, and B6, in which an additive containing the compound of formula (1) of the present invention (specifically, the compounds of formulas (2) to (4)) was used in an amount less than the amount specified in the present invention, the life retention rate was poor at less than 70%; and in the case of secondary batteries using the electrolyte compositions of Comparative Examples B3, B5, and B7, in which an additive containing the compound of formula (1) of the present invention (specifically, the compounds of formulas (2) to (4)) was used in an amount greater than the amount specified in the present invention, the life retention rate was very poor at less than 60%.

Claims

1. A compound selected from the group consisting of compounds represented by the following formulas (2) to (4): 【Chemistry 1】 【Chemistry 2】 (In formula (3), R 3 is a substituted or unsubstituted C1-C30 alkyl group. 【Transformation 3】 (In formula (4), R 3 and R 4 are each independently an unsubstituted C1-C30 alkyl group or a C1-C30 alkyl group substituted with a halogen atom.

2. The compound represented by formula (2) is selected from the group consisting of compounds represented by the following formulas (2-1) to (2-3): The compound represented by formula (3) is represented by the following formula (3-1) or (3-2): The compound according to claim 1, wherein the compound represented by formula (4) is represented by the following formula (4-1) or (4-2): 【Chemistry 4】 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 【Chemistry 9】 【Chemistry 10】

3. A method for producing a compound represented by formula (2), The method comprises the step of heating a dianhydrosugar hexitol-ethylene glycol compound in the presence of an acid catalyst, the dianhydrosugar hexitol being a compound in which ethylene glycol is added to both terminal hydroxy groups of the dianhydrosugar hexitol. 【Chemistry 11】

4. 4. The method according to claim 3, wherein the dianhydrosugar hexitol-ethylene glycol is produced by an addition reaction between a dianhydrosugar hexitol and ethylene oxide.

5. 5. The method according to claim 4, wherein the addition reaction of the dianhydrosugar hexitol with ethylene oxide is carried out using 2 or more moles of ethylene oxide per mole of the dianhydrosugar hexitol.

6. 4. The method of claim 3, wherein the acid catalyst is selected from sulfuric acid, hydrochloric acid, hydrobromic acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, or combinations thereof.

7. A method for producing a compound represented by formula (3), A method comprising the step of heating a compound represented by the following formula (A) with an alkylating agent in the presence of a base catalyst: 【Chemistry 12】 (In formula (3), R 3 is a substituted or unsubstituted C1-C30 alkyl group. 【Chemistry 13】

8. A method for producing a compound represented by formula (4), A method comprising the step of heating a compound represented by the following formula (B) with an alkylating agent in the presence of a base catalyst: 【Chemistry 14】 (In formula (4), R 3 and R 4 are each independently an unsubstituted C1-C30 alkyl group or a C1-C30 alkyl group substituted with a halogen atom. 【Chemistry 15】

9. 8. The method of claim 7, wherein the alkylating agent is selected from an alkyl halide having the formula R-X, where R is a substituted or unsubstituted C1-C30 alkyl group and X is a halogen atom, an aromatic sulfonate having a substituted or unsubstituted C1-C30 alkyl group, or a combination thereof.

10. 9. The method of claim 8, wherein the alkylating agent is selected from an alkyl halide having the formula R-X, where R is an unsubstituted C1-C30 alkyl group or a C1-C30 alkyl group substituted with a halogen atom, and X is a halogen atom, an aromatic sulfonate having an unsubstituted C1-C30 alkyl group or a C1-C30 alkyl group substituted with a halogen atom, or a combination thereof.

11. 9. The method according to claim 7 or 8, wherein the base catalyst is selected from an inorganic base catalyst, an organic base catalyst, or a combination thereof.

12. An electrolyte additive comprising a compound selected from the group consisting of compounds represented by the following formulas (2) to (4): 【Chemistry 16】 【Chemistry 17】 (In formula (3), R 3 is a substituted or unsubstituted C1-C30 alkyl group. [Chemistry 18] (In formula (4), R 3 and R 4 are each independently an unsubstituted C1-C30 alkyl group or a C1-C30 alkyl group substituted with a halogen atom.

13. Lithium nitrate (LiNO 3 ) and lithium nitrite (LiNO 2 ), nitromethane (CH 3 NO 2 ), methyl nitrate (CH 3 NO 3 13. The electrolyte additive of claim 12, further comprising a nitric acid (or nitrite) based compound selected from the group consisting of: nitrite, nitrite-based nitrates ...

14. a non-aqueous electrolyte solvent; a lithium salt; and the electrolyte additive according to claim 12 or 13; the content of the compound selected from the group consisting of compounds represented by the formulas (2) to (4) is 0.7 to 4.4 parts by weight relative to 100 parts by weight of the total amount of the electrolyte composition; The non-aqueous electrolyte composition, wherein the lithium salt is selected from the group consisting of LiSCN, LiBr, LiI, LiPF6, LiBF4, LiSbF6, LiAsF6, LiCH3SO3, LiCF3SO3, LiClO4, LiBPh4, LiC(CF3SO2)3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(SFO2)2, LiN(CF3CF2SO2)2, Li2S, LiSn (wherein n is an integer from 1 to 8), or a mixture thereof, and Ph means phenyl.

15. A secondary battery comprising: a positive electrode; a negative electrode; a separator; and the nonaqueous electrolyte composition of claim 14.

16. 16. The secondary battery according to claim 15, which is a lithium-sulfur secondary battery.

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