Electrolyte composition for lithium metal batteries

Abstract

The present invention provides a) R 1 -OR 2 -OR 3 Formula I, wherein each R 1 and R 3 are independently fluorinated alkyl groups, and R 2 is optionally a fluorinated alkyl group, and C a F b H c Formula II (wherein a is an integer from 1 to 6, b+c is an integer from 2 to 10, and when b is 0, R 1 and R 3 a) at least one fluorinated diether having 4 to 10 carbon atoms represented by the formula (wherein R is independently an alkyl group that is optionally fluorinated and R is an alkyl group that is independently an alkyl group that is free of H); b) at least one non-fluorinated ether; and c) at least one lithium salt, wherein a) the fluorinated diether is in an amount of at least 50 volume percent (vol%) based on the total volume of a) the fluorinated diether and b) the non-fluorinated ether. The present invention also relates to a lithium metal battery comprising a negative electrode containing lithium metal, a positive electrode, a separator, and the electrolyte composition of the present invention.

Description

Technical Field

[0001] Cross - reference to related applications This application claims priority to European Patent Application No. 20214399.6, filed on December 16, 2020, the entire content of which is incorporated herein by reference for all purposes.

[0002] The present invention relates to a) at least one fluorinated diether containing 4 to 10 carbon atoms, represented by formula I: R - O - R - O - R (where each R and R is independently a fluorinated alkyl group, R is optionally a fluorinated alkyl group), and formula II: C F H (where a is an integer from 1 to 6, b + c is an integer from 2 to 10, and when b is 0, R and R do not independently contain H); b) at least one non - fluorinated ether; c) at least one lithium salt, wherein the fluorinated diether in a) is present in an amount of at least 50% by volume (volume %) based on the total volume of a) the fluorinated diether and b) the non - fluorinated ether, related to an electrolyte composition for a lithium - metal battery. The present invention also relates to a lithium - metal battery comprising a negative electrode containing lithium metal, a positive electrode, a separator, and the electrolyte composition of the present invention. b , 2 , 1 , 2 , 1 , c , a , 3 , 3 , 1 , 3 -O-R 2 -O-R 3 In formula I, each R and R is independently a fluorinated alkyl group, R is optionally a fluorinated alkyl group, and formula II: C F H (where a is an integer from 1 to 6, b + c is an integer from 2 to 10, and when b is 0, R and R do not independently contain H). 1 and R 3 is independently a fluorinated alkyl group, R 2 is optionally a fluorinated alkyl group, C a F b H c In formula II, a is an integer from 1 to 6, b + c is an integer from 2 to 10, and when b is 0, R 1 [[ID= and R 3 do not independently contain H.

Background Art

[0003] Lithium-ion batteries have maintained a dominant position in the rechargeable energy storage device market due to their many advantages, including being lightweight, having a moderate energy density, and having a good cycle life. Nevertheless, current lithium-ion batteries still have a relatively low energy density compared to the continuously increasing energy density required to meet the needs of high-power applications such as electric vehicles, hybrid electric vehicles, and grid energy storage (also known as large-scale energy storage).

[0004] The use of lithium metal as a negative electrode has been known since 1970 due to its favorable properties, stemming from its low oxidation-reduction potential and high specific capacity. Such lithium metal batteries typically use conventional liquid electrolytes, such as carbonate-based electrolytes and / or ether-based electrolytes with low viscosity and high ionic conductivity. These liquid electrolytes decompose at the start of the cycle to form a passivation layer, which leads to dendrite growth and also triggers further side reactions between the electrolyte and deposited reactive lithium ions. These have been significant problems that have hindered the commercialization of lithium metal batteries.

[0005] The basic requirements for electrolytes suitable for lithium metal batteries are the same as those for conventional liquid electrolytes for lithium-ion batteries: high ionic conductivity, low melting point and high boiling point, (electro)chemical stability, and safety. In addition to the above basic requirements, electrolytes suitable for lithium metal batteries should offer solutions to the aforementioned drawbacks.

[0006] As part of various studies aimed at reducing or suppressing lithium dendrite formation and improving the cycle performance of lithium metal batteries, the use of solid electrolytes instead of liquid electrolytes is being investigated. For example, R. Sudo et al., in Solid State Ionics, 262, 151 (2014), used Al-doped Li7La3Zr2O as a solid electrolyte for an electrochemical cell containing Li metal as a delocalized component. 12The document describes the use of [the substance]. However, lithium dendrites were still observed.

[0007] D. Aurbach et al. in Solid State Ionics, 148, 405 (2002), and H. Ota et al. in Electrochimica Acta, 49, 565 (2004), reported that additives such as CO2, SO2, and vinylene carbonate help improve the stability of the passivation layer. However, these additives are consumed during cell operation. Therefore, they cannot be a long-term solution to dendrite formation.

[0008] Furthermore, various approaches exist with the same objective, involving changes to the composition of the liquid electrolyte.

[0009] For example, the use of a liquid electrolyte with a high lithium salt concentration of LiTFSI in dimethoxyethane (DME)-1,3-dioxolane (DOL) (1:1 v:v) has been described by L. Suo et al. in Nature Communications, DOI:10.1038 / ncomms2513 (2013) as a way to suppress lithium dendrite formation.

[0010] H. Wang et al. reported in ChemElectroChem, 2, 1144 (2015) that a cell containing lithium metal as the anode and tetraglyme (G4) and LiFSI solvated ionic liquids as electrolytes exhibits excellent cycling performance.

[0011] U.S. Patent Application Publication No. 2007 / 054186A1 (3M Innovative Properties Company) discloses an electrolyte composition for electrochemical devices comprising a solvent composition containing a cyclic carbonate ester such as ethylene carbonate, at least one fluorine-containing solvent having a boiling point of at least 80°C, such as a hydrofluoroether of a specific formula, and at least one electrolyte salt such as LiPF6.

[0012] International Publication No. 2015 / 078791B1 (Solvay Specialty Polymers Italy SPA) also discloses electrolyte formulations containing hydrofluoroethers and polar organic solvents, particularly organic carbonates, as essential components of electrolyte mixtures.

[0013] In particular, European Patent No. 3118917 (Samsung Electronics Co., Ltd.) discloses an electrolyte specific to lithium metal batteries, comprising a non-fluorine-substituted ether capable of solvating lithium ions, a fluorine-substituted ether which is a glycylem-based solvent having a specific formula, and a lithium salt, wherein the amount of fluorine-substituted ether is greater than the amount of non-fluorine-substituted ether. [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] However, there is still a need to provide electrolytes for lithium metal batteries that improve cell performance, including safety, while minimizing dendrite growth and side reactions between the liquid electrolyte and the negative electrode. [Means for solving the problem]

[0015] The present invention relates to an electrolyte composition for lithium metal batteries. a) A fluorinated diether containing 4 to 10 carbon atoms, represented by formula I. R 1 -OR 2 -OR 3 (Equation I) (In the formula, each R 1 and R 3 R is independently a fluorinated alkyl group. 2 is optionally a fluorinated alkyl group, and formula II C a F b H c (Formula II) (In the formula, a is an integer from 1 to 6, b+c is an integer from 2 to 10, and if b is 0, R1 and R 3 (It is represented as such, but does not independently possess H); b) at least one non-fluorinated ether; and c) at least one lithium salt; It contains, The present invention relates to a composition in which a) fluorinated diether is present in an amount of at least 50% by volume (vol%) based on the total volume of a) fluorinated diether and b) non-fluorinated ether.

[0016] Furthermore, the present invention relates to a lithium metal battery comprising a negative electrode containing lithium metal, a positive electrode, a separator, and the electrolyte composition of the present invention.

[0017] Surprisingly, the inventors have found that the above technical problems can be solved by using the electrolyte composition for lithium metal batteries of the present invention, as evidenced by its excellent capacity retention rate and Coulomb efficiency. [Brief explanation of the drawing]

[0018] [Figure 1] This shows the cycle retention rate (%) of LiCoO2 / Li cells containing electrolyte compositions E1-E2 and CE1-CE4 at 3.0-4.4V (0.5C / 0.5C). [Figure 2] This shows the cycle retention rate (%) of LiCoO2 / Li cells containing electrolyte compositions E1-E2 and CE5-CE9 at 3.0-4.4V (0.5C / 0.5C). [Modes for carrying out the invention]

[0019] Throughout this specification, unless the context requires otherwise, the words “comprise,” “include,” or variations such as “comprises,” “includes,” and “includes” are understood to mean the inclusion of the element or process or group of elements or processes described, but not the exclusion of any other element or process or group of elements or processes. In a preferred embodiment, the words “comprise” and “include,” and variations thereof, mean “consisting of only.”

[0020] As used herein, the singular forms "a," "an," and "the" encompass the plural unless the context explicitly indicates otherwise. The term "and / or" encompasses the meanings "and," "or," and all other possible combinations of elements related to this term.

[0021] The term "~" should be understood to include the limit point. The term "(C)" used herein with respect to organic groups. n ~C m The expression ) (where n and m are integers) indicates that this group may contain n to m carbon atoms per group.

[0022] The term "aliphatic group" includes organic moieties that typically have 1 to 18 carbon atoms and are characterized by a straight or branched chain. In complex structures, the chain may be branched, cross-linked, or bridging. Aliphatic groups include alkyl groups, alkenyl groups, and alkynyl groups.

[0023] Ratios, concentrations, quantities, and other numerical data may be expressed in range form as herein. It should be understood that such range forms are used merely for convenience and brevity, and should be interpreted flexibly to include not only the numerical values ​​explicitly listed as limits of the range, but also all individual numerical values ​​or subranges contained within that range, as if each numerical value and subrange were explicitly listed. For example, a temperature range of approximately 120°C to approximately 150°C should be interpreted to include not only the explicitly listed limit of approximately 120°C to approximately 150°C, but also subranges such as 125°C to 145°C, 130°C to 150°C, etc., as well as individual quantities such as small quantities within the specified range, such as 122.2°C, 140.6°C, and 141.3°C.

[0024] As used herein, molar concentration or molar concentration is a measure of the concentration of a chemical species, particularly a solute, in a solution with respect to the amount of substance per unit volume of the solution. The most commonly used unit of molar concentration is the number of moles per liter, with the unit mol / L. A solution with a concentration of 1 mol / L is indicated as 1 molar concentration and is denoted as 1 M.

[0025] Unless otherwise specified, in relation to the present invention, the amount of a component in a composition is expressed as the ratio of the volume of the component to the total volume of the composition multiplied by 100, i.e., as volume % (vol%), or as the ratio of the weight of the component to the total weight of the composition multiplied by 100, i.e., as weight % (wt%).

[0026] In this invention, the term "Coulomb efficiency," also known as Faraday efficiency, is intended to represent the charging efficiency of electron movement in a system that facilitates an electrochemical reaction, i.e., a battery, and corresponds to the ratio of the total charge extracted from the battery to the total charge introduced into the battery over the entire cycle. Furthermore, the Coulomb efficiency (%) is calculated by dividing the discharge capacity of each cycle by the charge capacity of each cycle and multiplying by 100.

[0027] As used herein, the term “lithium metal battery” is intended to refer to a secondary (rechargeable) battery having metallic lithium as the anode.

[0028] It should be understood that both the above summary and the following detailed description are illustrative and intended to provide a further explanation of the claimed invention. Therefore, various modifications and alterations described herein will be apparent to those skilled in the art. Furthermore, for clarity and brevity, well-known descriptions of functions and structures may be omitted.

[0029] The present invention relates to an electrolyte composition for lithium metal batteries: a) A fluorinated diether containing 4 to 10 carbon atoms, represented by formula I. R 1 -OR 2 -OR 3 (Equation I) (In the formula, each R 1 and R 3 R is independently a fluorinated alkyl group. 2 is optionally a fluorinated alkyl group, and formula II C a F b H c (Formula II) (In the formula, a is an integer from 1 to 6, b+c is an integer from 2 to 10, and if b is 0, R 1 and R 3 (It is represented as such, but does not independently possess H); b) at least one non-fluorinated ether; and c) at least one lithium salt; It contains, The present invention relates to a composition in which a) fluorinated diether is present in an amount of at least 50% by volume (vol%) based on the total volume of a) fluorinated diether and b) non-fluorinated ether.

[0030] In one embodiment, the fluorinated alkyl group is a fluorinated saturated and linear hydrocarbon.

[0031] In other embodiments, the fluorinated alkyl group is a fluorinated saturated and linear hydrocarbon.

[0032] In one embodiment, a) the fluorinated diether contains 5 to 8 carbon atoms, preferably 6 carbon atoms.

[0033] In one embodiment, the electrolyte composition for lithium metal batteries according to the present invention is: a) At least one fluorinated diether containing 5 to 8 carbon atoms, represented by formula I. R 1’ -O-R' 2 -OR 3’ (Formula I') (In the formula, each R 1’ and R 3’ R is independently a fluorinated alkyl group. 2’ is optionally a fluorinated alkyl group, and formula II' C a’ F b’ H c’ (Formula II') (In the formula, a' is an integer from 1 to 4, b'+c' is an integer from 2 to 8, and if b' is 0, R 1’ and R 3’ (is represented by (which does not independently possess H)); b) at least one non-fluorinated ether; and c) at least one lithium salt; It contains, The present invention relates to a composition in which a) fluorinated diether is present in an amount of at least 50% by volume, based on the total volume of a) fluorinated diether and b) non-fluorinated ether.

[0034] In one embodiment, the electrolyte composition according to the present invention is: -60-90% by volume of fluorinated diether based on the total volume of a) fluorinated diether and b) non-fluorinated ether; and - Contains 10 to 40 volume percent of (b) non-fluorinated ether.

[0035] In another embodiment, the electrolyte according to the present invention is: -80-90% by volume of a) fluorinated ether compounds based on the total volume of a) fluorinated diethers and b) non-fluorinated ethers; and - Contains 10-20% by volume of (b) non-fluorinated ether.

[0036] In a particular embodiment, the electrolyte composition for lithium metal batteries according to the present invention is: - Based on the total volume of a) fluorinated diether and b) non-fluorinated ether, 80 volume% of a) fluorinated diether containing 6 carbon atoms; -20% by volume of b) non-fluorinated ether and - Contains 1 M LiFSI dissolved in a mixture of a) fluorinated diether and b) non-fluorinated ether.

[0037] In the present invention, the term "alkyl" is intended to mean saturated hydrocarbons having one or more carbon atoms, including linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclopropyl, cyclopentyl, and cyclohexyl (or "cycloalkyl" or "alicyclic").

[0038] In the present invention, the term "fluorinated ether compound" is intended to mean an ether compound in which at least one hydrogen atom is replaced by fluorine. One, two, three, or more hydrogen atoms may be replaced by fluorine.

[0039] In this invention, the term "boiling point" is intended to indicate the temperature at which the vapor pressure of a liquid substance is equal to the pressure surrounding the liquid, causing the liquid to change its physical state into vapor. The boiling point of a liquid substance varies depending on the ambient pressure, and the boiling point according to this invention corresponds to the boiling point when the liquid is at atmospheric pressure, and is also known as the atmospheric pressure boiling point.

[0040] In one embodiment, a) the boiling point of the fluorinated diether is at least 80°C, preferably 80°C to 160°C.

[0041] In one embodiment, a) the molar ratio F / H in the fluorinated diether is 2.0 to 11.0, preferably 2.5 to 8.0, and more preferably 2.5 to 6.0.

[0042] In one embodiment, a) the fluorinated diether contains five carbon atoms.

[0043] In a preferred embodiment, a) the fluorinated diether is a mixture containing C5F9H3O2 in an amount of at least 50% by weight, based on the total weight of a) the fluorinated diether.

[0044] In another preferred embodiment, a) the fluorinated diether is C5F in an amount of at least 50% by weight, based on the total weight of the fluorinated diether. 10 It is a mixture containing H2O2.

[0045] In another preferred embodiment, a) the fluorinated diether is C5F in an amount of at least 50% by weight, based on the total weight of the fluorinated diether. 11 It is a mixture containing H1O2.

[0046] In another embodiment, a) the fluorinated diether contains six carbon atoms.

[0047] In a preferred embodiment, a) the fluorinated diether is C6F in an amount of at least 50% by weight, preferably at least 70% by weight, based on the total weight of a) the fluorinated diether. 10 It is a mixture containing H4O2.

[0048] In a preferred embodiment, a) the fluorinated diether is C6F in an amount of at least 50% by weight, based on the total weight of a) the fluorinated diether. 11 It is a mixture containing H3O2.

[0049] In a preferred embodiment, a) the fluorinated diether is C6F in an amount of at least 50% by weight, based on the total weight of a) the fluorinated diether. 12 It is a mixture containing H2O2.

[0050] In another embodiment, a) the fluorinated diether contains seven carbon atoms.

[0051] In a preferred embodiment, a) the fluorinated diether is C7F in an amount of at least 50% by weight, preferably at least 70% by weight, based on the total weight of a) the fluorinated diether. 12 It is a mixture containing H4O2.

[0052] In a preferred embodiment, a) the fluorinated diether is C7F in an amount of at least 50% by weight, based on the total weight of a) the fluorinated diether. 14 It is a mixture containing H2O2.

[0053] In another embodiment, a) the fluorinated diether contains eight carbon atoms.

[0054] In a preferred embodiment, a) the fluorinated diether is C8F in an amount of at least 50% by weight, preferably at least 70% by weight, and more preferably at least 80% by weight, based on the total weight of a) the fluorinated diether. 12 It is a mixture containing H6O2.

[0055] In a preferred embodiment, a) the fluorinated diether is C8F in an amount of at least 50% by weight, based on the total weight of a) the fluorinated diether. 14 It is a mixture containing H4O2.

[0056] In a preferred embodiment, a) the fluorinated diether is C8F in an amount of at least 50% (by weight) based on the total weight of a) the fluorinated diether. 16 It is a mixture containing H2O2.

[0057] Non-limiting examples of suitable a) fluorinated diether compounds according to the present invention include, in particular, the following: CF3CH2-O-CF2CHF-O-CF 3, CHF2CH2-O-CF2CF2-O-CF 3, CF3CF2-O-CHFCHF-O-CHF 2, CHF2CF2-O-CHFCHF-O-CF 3, CF3CHF-O-CHFCF2-O-CHF 2, CF3CHF-O-CF2CHF-O-CHF 2, CH3CF2-O-CF2-O-CF2CF 3, CFH2CHF-O-CF2-O-CF2CF 3, CF3CF2-O-CHF-O-CHFCHF 2, CF3CF2-O-CHF-O-CHFCHF 2, CF3CH2-O-CF2CF2-O-CF 3, CHF2CHF-O-CF2CF2-O-CF 3, CH2FCF2-O-CF2CF2-O-CF 3, CF3CF2-O-CHFCHF-O-CF 3, CF3CF2-O-CF2CH2-O-CF 3, CF3CF2-O-CH2CF2-O-CF 3, CF3CF2-O-CF2CFH-O-CHF 2, CF3CHF-O-CHFCF2-O-CF 3, CF3CHF-O-CF2CHF-O-CF 3, CHF2CF2-O-CF2CHF-O-CF 3, CHF2CF2-O-CHFCF2-O-CF 3, CHF2CF2-O-CF2CF2-O-CHF 2, CF3CHF-O-CF2CF2-O-CHF 2, CF3CF2-O-CF2-O-CHFCF3,CF2HCF2-O-CF2-O-CF2CF 3, CF3CHF-O-CF2-O-CF2CF 3, CF3CF2-O-CHF-O-CF2CF 3, CF3CF2-O-CF2-O-CF2CHF 2,CF2HCF2-O-CF2CH2-O-CF2CF2H,CF3CF2-O-CH2CH2-O-CF2CF 3, CF2HCF2-O-CHFCHF-O-CF2CF2H,CF3CF2-O-CHFCH2-O-CF2CF2H,CF2HCF2-O-CHFCHF-O-CF2CF2H,CF3CF2-O-CH2CHF-O-CF2CF2H,CF3-O-CHFCF2CH2-O-CF2CF2H,CF2HCF2-O-CF2C F2-O-CF2CF2H, CF3CF2-O-CF2CHF-O-CF2CF2H, CF3CF2-O-CHFCF2-O-CF2CF2H, CF3CF2-O-CF2CH2-O-CF2CF3, CF3CF2-O-CHFCHF-O-CF2CF3, CF3CF2-O-CHFCHF-O-CF2CF3 and mixtures thereof.

[0058] In this invention, the term "non-fluorinated ether" is intended to mean an ether compound that does not contain a fluorine atom.

[0059] Suitable b) nonfluorinated ether compounds according to the present invention include, in particular, the following: -Aliphatic, alicyclic, or aromatic ethers, more specifically dibutyl ether, dipentyl ether, diisopentyl ether, dimethoxyethane (DME), 1,3-dioxolane (DOL), tetrahydrofuran (THF), 2-methyltetrahydrofuran, and diphenyl ether; Glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether (DEGDME), ethylene glycol diethyl ether, diethylene glycol diethyl ether (DEGDEE), tetraethylene glycol dimethyl ether (TEGME), polyethylene glycol dimethyl ether (PEGDME); - Glycol ether esters such as ethylene glycol methyl ether acetate, ethylene glycol monoethyl ether acetate, and ethylene glycol monobutyl ether acetate - Trialkyl phosphates, such as trimethyl phosphate and triethyl phosphate (TEP).

[0060] In preferred embodiments, the non-fluorinated ether compounds b) according to the present invention include dimethoxyethane (DME), 1,3-dioxolane (DOL), dibutyl ether, tetraethylene glycol dimethyl ether (TEGME), diethylene glycol dimethyl ether (DEGDME), diethylene glycol diethyl ether (DEGDEE), polyethylene glycol dimethyl ether (PEGDME), 2-methyltetrahydrofuran, tetrahydrofuran (THF), triethyl phosphate (TEP), and mixtures thereof.

[0061] In a more preferred embodiment, b) the non-fluorinated ether is a mixture of DME and DOL.

[0062] In another, more preferred embodiment, b) the non-fluorinated ether is DME.

[0063] The lithium salts include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluoroantimonate (LiSbF6), lithium hexafluorotantalate (LiTaF6), lithium tetrachloroaluminate (LiAlCl4), lithium tetrafluoroborate (LiBF4), lithium chloroborate (Li2B 10 Cl 10 ), lithium fluoroborate (Li2B 10 F 10 ), Li2B 12 F x H 12-x (x = 0 to 12); LiPF x (R F ) 6-x and LiBF y (R F ) 4-y (where R F represents a perfluorinated C1 - C 20 alkyl group or a perfluorinated aromatic group, x = 0 to 5, and y = 0 to 3), LiBF2[O2C(CX2) n CO2], LiPF2[O2C(CX2) n CO2]2, LiPF4[O2C(CX2) n CO2](where X is selected from the group consisting of H, F, Cl, C1 - C4 alkyl groups, and fluorinated alkyl groups, and n = 0 to 4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), LiN(SO2C m F 2m+1 )(SO2C n F 2n+1 ) and LiC(SO2C k F 2k+1 )(SO2C m F 2m+1 )(SO2C n F 2n+1 )(where k = 1 to 10, m = 1 to 10, and n = 1 to 10), LiN(SO2C p F<于 2p SO2) and LiC(SO2C<0000I16>[[ID=S2]]F 2pSO2)(SO2C q F 2q+1 ) (wherein p=1 to 10 and q=1 to 10), lithium salts of chelated orthoborates and chelated orthophosphates, e.g., lithium bis(oxalato)borate [LiB(C2O4)2], lithium bis(malonato)borate [LiB(O2CCH2CO2)2], lithium bis(difluoromalonato)borate [LiB(O2CCF2CO2)2]2], lithium (malonatooxalato)borate [LiB(C2O4)(O2CCH2CO2)] These are described as lithium ion complexes such as lithium (difluoromalonatooxalato) borate [LiB(C2O4)(O2CCF2CO2)], lithium tris(oxalato) phosphate [LiP(C2O4)3], lithium tris(difluoromalonato) phosphate [LiP(O2CCF2CO2)3], lithium difluorophosphate (LiPO2F2), lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI), and mixtures of the above.

[0064] Preferred lithium salts are LiPF6, LiTFSI, and LiFSI, which can be used individually or in combination.

[0065] In one embodiment, c) the lithium salt is LiPF6.

[0066] In a preferred embodiment, c) the lithium salt is LiFSI.

[0067] In one embodiment, the molar concentration (M) of the lithium salt in the liquid electrolyte composition according to the present invention is 1M to 8M, preferably 1M to 4M, and more preferably 1M to 2M.

[0068] According to one embodiment, the electrolyte composition according to the present invention further comprises d) at least one fluorinated organic carbonate compound.

[0069] d) Non-limiting examples of fluorinated organic carbonate compounds include 4-fluoroethylene carbonate, 4,5-difluoro-1,3-dioxolan-2-one, 4,5-difluoro-4-methyl-1,3-dioxolan-2-one, 4,5-difluoro-4,5-dimethyl-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, and tetrafluoroethylene carbonate. Carbonate, 2,2,3,3-tetrafluoropropylmethyl carbonate, bis(2,2,3,3-tetrafluoropropyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2,2,2-trifluoroethylmethyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2-difluoroethylmethyl carbonate, 1-fluoroethylmethyl carbonate, 1-fluoroethylpropyl carbonate, 1-fluoroethylethyl carbonate, 1-fluoroethylphenyl carbonate, 1-fluoroethyl-2,2,2-trifluoroethyl carbonate, allyl-1-fluoroethylmethyl carbonate, fluoromethyl methyl carbonate, 2-cyanoethyl-1-fluoroethyl carbonate, 1-fluoroethylpropanyl carbonate, 4-(2,2-difluoroethoxy)ethylene carbonate, 4-(2,2,2-trifluoroethoxy)ethylene carbonate This includes ionate, ethyl fluoro(phenyl)methyl carbonate, tris(trifluoroethyl) phosphate, methyl-3,3,3-trifluoropropanonate, 3-((2-oxo-1,3-dioxolan-4-yl)oxy)propanenitrile, 2,2-difluoroethyl methyl carbonate, 2,2-difluoroethyl acetate, 2,2-difluoroethyl methyl carbonate, 2,2-difluoroethyl propionate, and mixtures thereof.

[0070] In the present invention, d) the total amount of at least one fluorinated organic carbonate compound may be 0 to 50% by weight, preferably 0 to 40% by weight, and more preferably 0 to 30% by weight, relative to the total weight of the electrolyte. d) The total amount of at least one fluorinated organic carbonate compound, when included in the electrolyte composition of the present invention, is 5 to 50.0% by weight, preferably 10 to 40% by weight, and more preferably 20 to 30% by weight, relative to the total weight of the electrolyte composition.

[0071] According to one embodiment, the electrolyte composition according to the present invention further comprises e) at least one film-forming additive that promotes the formation of a solid electrolyte interface (SEI) layer on the negative electrode surface by pre-reacting the solvent on the electrode surface. Thus, the main components for the SEI layer include an electrolyte solvent and salt decomposition products, which may include Li2CO3 (in the case of LiCoO2 as the positive electrode), lithium alkyl carbonate, lithium alkyl oxide, and other salt portions such as LiF for LiPF6-based electrolytes. According to another embodiment, e) the film-forming additive stabilizes the cathode electrolyte interface (CEI) layer on the positive electrode surface by preventing structural changes of the positive electrode, particularly under high voltage. Typically, the reduction potential of the film-forming additive is higher than the reduction potential of the solvent when the reaction occurs on the negative electrode surface, and the oxidation potential of the film-forming additive is lower than the oxidation potential of the solvent when the reaction occurs on the negative electrode side.

[0072] In one embodiment, the film-forming additive according to the present invention includes: e) cyclic sulfites and sulfate compounds comprising 1,3-propanesultone (PS), ethylene sulfite (ES), and prop-1-ene-1,3-sultone (PES); sulfone derivatives comprising dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethylmethylsulfone, and isopropylmethylsulfone; nitrile derivatives comprising succinonitrile, adiponitrile, glutalonitrile, and 4,4,4-trifluoronitrile; lithium nitrate (LiNO3); boron derivative salts such as lithium difluorooxalatoborate (LiDFOB) and lithium fluoromalonato(difluoro)borate (LiFMDFB); vinyl acetate, biphenylbenzene, isopropylbenzene, hexafluorobenzene, tris(trimethylsilyl)phosphate, triphenylphosphine, ethyldiphenylphosphinite, and triethylphosphine Ito, tris(2,2,2-trifluoroethyl) phosphite, maleic anhydride, vinylene carbonate, vinylethylene carbonate, cesium bis(trifluorosulfonyl)imide (CsTFSI), cesium hexafluorophosphate (CsPF6), cesium fluoride (CsF), trimethylboroxine (TMB), tributylborate (TBB), 2-(2,2,3,3,3-pentafluoropropoxy)-1,3,2-dioxaphospho The following are selected from the group consisting of PFPOEPi, 2-(2,2,3,3,3-pentafluoropropoxy)-4-(trifluoromethyl)-1,3,2-dioxaphosphorane (PFPOEPi-1CF3), lithium hexafluorophosphate (LiPF6), silver nitrate (AgNO3) hexafluorophosphate (AgPF6), tris(trimethylsilyl)phosphine (TMSP), 1,6-divinylperfluorohexane, and mixtures thereof.

[0073] In a preferred embodiment, e) the film-forming additive according to the present invention is vinylene carbonate.

[0074] In another embodiment, e) the film-forming additive according to the present invention is an ionic liquid.

[0075] As used herein, the term "ionic liquid" refers to a compound that contains positively charged cations and negatively charged anions and is in a liquid state at atmospheric pressure and temperatures below 100°C. While ordinary liquids such as water are composed mainly of electrically neutral molecules, ionic liquids are composed mainly of ions and short-lived ion pairs. As used herein, the term "ionic liquid" refers to a solvent-free compound.

[0076] As used herein, the term "onium cation" refers to a positively charged ion in which at least a portion of its charge is localized on at least one nonmetallic atom such as O, N, S, or P.

[0077] In this invention, the ionic liquid is A n- Q l+ (n / l) (In the formula, -A n- This represents an anion, -Q l+ (n / l) This represents a cation, -n and l are independently selected from 1 to 5, and each is an anion A n- and cation Q l+ (n / l) (Represents the electric charge) It has a general formula.

[0078] The cations can be independently selected from metal cations and organic cations. The cations can be monovalent or polyvalent.

[0079] Preferred examples of metal cations include alkali metal cations, alkaline earth metal cations, and d-block element cations.

[0080] In this invention, Q l+ (n / l)This can represent an onium cation. An onium cation is a cation formed by elements of groups VB and VIB (as defined in the old European IUPAC system according to the periodic table) having three or four hydrocarbon chains. Group VB includes N, P, As, Sb, and Bi atoms. Group VIB includes O, S, Se, Te, and Po atoms. An onium cation may be a cation formed by three or four hydrocarbon chains with atoms selected from the group consisting of N, P, O, and S, more preferably N and P.

[0081] Onium Cation Q l+ (n / l) teeth, - Heterocyclic onium cations, especially: [ka] One selected from the group consisting of; - Unsaturated cyclic onium cations, particularly those consisting of the following: - Saturated cyclic onium cations, particularly those consisting of the following: [ka] - Acyclic onium cations, especially those with a general formula + L-R' s (In the formula, L represents an atom selected from the group consisting of N, P, O, and S, more preferably N and P; s represents the number of R' groups selected from 2, 3, or 4 depending on the valence of element L; each R' independently represents a hydrogen atom or a C1-C8 alkyl group, L + The bond between and R' can be a single bond or a double bond. You can choose from these options.

[0082] In the above formula, each "R" symbol independently represents a hydrogen atom or an organic group. Preferably, each "R" symbol in the above formula independently represents a hydrogen atom, or is optionally substituted one or more times with a halogen atom, amino group, imino group, amide group, ether group, ester group, hydroxyl group, carboxyl group, carbamoyl group, cyano group, sulfone group, or sulfite group, and is a saturated or unsaturated linear, branched or cyclic C1-C1 group. 18 It can represent hydrocarbon groups.

[0083] Cation Q l+ (n / l) More specifically, these can be selected from ammonium, phosphonium, pyridinium, pyrrolidinium, pyrazolinium, imidazolium, arsenic, quaternary phosphonium, and quaternary ammonium cations.

[0084] The quaternary phosphonium or quaternary ammonium cation can more preferably be selected from tetraalkylammonium or tetraalkylphosphonium cation, trialkylbenzylammonium or trialkylbenzylphosphonium cation, or tetraarylammonium or tetraarylphosphonium cation, wherein these alkyl groups are identical or different and represent a linear or branched alkyl chain having 4 to 12 carbon atoms, preferably 4 to 6 carbon atoms, and these aryl groups are identical or different and represent a phenyl group or a naphthyl group.

[0085] In a particular embodiment, Q l+ (n / l) This represents a quaternary phosphonium or quaternary ammonium cation.

[0086] In one preferred embodiment, Q l+ (n / l) This represents a quaternary phosphonium cation. Non-exclusive examples of quaternary phosphonium cations include trihexyl(tetradecyl)phosphonium and tetraalkylphosphonium cations, particularly the tetrabutylphosphonium (PBu4) cation.

[0087] In another embodiment, Q l+ (n / l) represents an imidazolium cation. Non-restrictive examples of imidazolium cations include 1,3-dimethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-allyl-3H-imidazolium, 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-octyl-3-methylimidazolium.

[0088] In another embodiment, Q l+ (n / l) In particular, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, trimethylbenzylammonium, methyltributylammonium, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium, N,N-dimethyl-N-ethyl-N-(3-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-benzylammonium, N,N-dimethyl-N-ethyl-N-phenylethylammonium, N-tributyl-N-methylammonium, N-trimethyl-N-butylammonium, N-trimethyl-N-hexylammonium, N-trimethyl-N-propylammonium and Aliquat336 (methyltri(C8~C) 10 This represents a quaternary ammonium cation selected from the group consisting of alkyl (ammonium compound mixtures).

[0089] In one embodiment, Q l+ (n / l) This represents piperidinium cations, particularly N-butyl-N-methylpiperidinium and N-propyl-N-methylpiperidinium.

[0090] In another embodiment, Q l+ (n / l) This represents a pyridinium cation, specifically N-methylpyridinium.

[0091] In a more preferred embodiment, Q l+ (n / l)This represents a pyrrolidinium cation. Among the specific pyrrolidinium cations, the following can be listed: C 1~12 Alkyl-C 1~12 Alkyl-pyrrolidinium, more preferably C 1~4 Alkyl-C 1~4 Alkyl-pyrrolidinium. Examples of pyrrolidinium cations, though not limited to them, include N,N-dimethylpyrrolidinium, N-ethyl-N-methylpyrrolidinium, N-isopropyl-N-methylpyrrolidinium, N-methyl-N-propylpyrrolidinium, N-butyl-N-methylpyrrolidinium, N-octyl-N-methylpyrrolidinium, N-benzyl-N-methylpyrrolidinium, N-cyclohexylmethyl-N-methylpyrrolidinium, and N-[(2-hydroxy)ethyl]-N-methylpyrrolidinium. More preferred are N-methyl-N-propylpyrrolidinium (PYR13) and N-butyl-N-methylpyrrolidinium (PYR14). Non-limiting examples of anions in ionic liquids include iodides, bromides, chlorides, bisulfate ions, dicyanamides, acetates, diethyl phosphates, methyl phosphates, and fluorinated anions, such as hexafluorophosphate (PF6). - ) and tetrafluoroborate (BF4 - ), and the following formula: [ka] Oxalatobolate Includes.

[0092] In one embodiment, A n- This is a fluorinated anion. Among the fluorinated anions that can be used in the present invention, the fluorinated sulfonimide anion may be particularly advantageous. This organic anion is particularly characterized by the following general formula: (E a -SO2)N - R (In the formula, - E arepresents a fluorine atom or a group having preferably 1 to 10 carbon atoms, selected from fluoroalkyl, perfluoroalkyl and fluoroalkenyl, and - R represents a substituent.) Anions having the following characteristics can be selected:

[0093] Preferably, E a This can represent F or CF3.

[0094] According to the first embodiment, R represents a hydrogen atom.

[0095] According to the second embodiment, R preferably represents a group based on a linear or branched cyclic or acyclic hydrocarbon having 1 to 10 carbon atoms, which may optionally have one or more unsaturated atoms and may be optionally substituted once or once by a halogen atom, by a nitrile functional group, or by an alkyl group which may be optionally substituted once or once by a halogen atom. Furthermore, R may represent a nitrile group -CN.

[0096] According to the third embodiment, R represents a sulfinate group. In particular, R is E a The base -SO2-E is defined above. a This can represent the fluorinated anion being symmetric, i.e., the two E's of the anion. a They can be identical in their groups, or asymmetric, i.e., the two E's of the anion a They could be based on completely different principles.

[0097] Furthermore, R can represent the group -SO2-R', where R' preferably represents a group based on a linear or branched cyclic or acyclic hydrocarbon having 1 to 10 carbon atoms, which may optionally have one or more unsaturated atoms and may be optionally substituted once or more by halogen atoms, by nitrile functional groups, or by alkyl groups which may be optionally substituted once or more by halogen atoms. In particular, R' may include a vinyl group or an allyl group. Furthermore, R can represent the group -SO2-N-R' (where R' is as defined above, or otherwise R' represents a sulfonate functional group -SO3).

[0098] Groups based on cyclic hydrocarbons may preferably refer to cycloalkyl or aryl groups. "Cycloalkyl" refers to a monocyclic hydrocarbon chain having 3 to 8 carbon atoms. Preferred examples of cycloalkyl groups are cyclopentyl and cyclohexyl. "Aryl" refers to a monocyclic or polycyclic aromatic hydrocarbon group having 6 to 20 carbon atoms. Preferred examples of aryl groups are phenyl and naphthyl. If the group is a polycyclic group, the rings may be condensed or bonded by sigma (σ) bonds.

[0099] According to the fourth embodiment, R represents a carbonyl group. In particular, R can be represented by the formula -CO-R' (where R' is as defined above).

[0100] The organic anion that can be used in this invention is, advantageously, CF3SO2N - SO2CF3 (bis(trifluoromethanesulfonyl)imide anion, commonly shown as TFSI), FSO2N - SO2F (bis(fluorosulfonyl)imide anion, commonly shown as FSI), CF3SO2N - SO2F and CF3SO2N - SO2N - You can choose from the group consisting of SO2CF3.

[0101] In a preferred embodiment, the ionic liquid is -1 or more C1-C30 A positively charged cation selected from the group consisting of imidazolium, pyridinium, pyrrolidinium, and piperidinium ions, which optionally contain an alkyl group, - A negatively charged anion selected from the group consisting of halides, fluorinated anions, and borates. It contains.

[0102] C1-C 30 Non-limiting examples of alkyl groups include, in particular, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, 2,2-dimethylpropyl, hexyl, 2,3-dimethyl-2-butyl, heptyl, 2,2-dimethyl-3-pentyl, 2-methyl-2-hexyl, octyl, 4-methyl-3-heptyl, nonyl, decyl, undecyl, and dodecyl groups.

[0103] In one preferred embodiment, the film-forming additive according to the present invention is selected from the group consisting of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI), N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI), and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI).

[0104] In the present invention, e) the total amount of the film-forming additive may be 0 to 10% by weight, preferably 0 to 8% by weight, and more preferably 0 to 5% by weight, relative to the total weight of the electrolyte composition.

[0105] e) The total amount of the film-forming additive, when included in the liquid electrolyte of the present invention, is 0.05 to 5.0% by weight, preferably 0.05 to 3.0% by weight, and more preferably 0.05 to 2.0% by weight, relative to the total weight of the electrolyte composition.

[0106] In a preferred embodiment, e) the total amount of the film-forming additive accounts for at least 1.0% by weight of the electrolyte composition.

[0107] Furthermore, the present invention provides a negative electrode containing lithium metal; a positive electrode; a separator; and a lithium metal battery containing the electrolyte according to the present invention.

[0108] In the present invention, the term "negative electrode" is specifically intended to represent the electrode of an electrochemical cell where oxidation occurs during discharge.

[0109] In the present invention, the term "positive electrode" is specifically intended to represent the electrode of an electrochemical cell where reduction occurs during discharge. In the present invention, the term "electroactive material" is intended to mean an electroactive material that can be incorporated or inserted into its structure during the charging and discharging stages of the battery and can substantially release lithium ions therefrom.

[0110] When forming a positive electrode for a lithium metal battery, the electroactive material of the positive electrode is not particularly limited. It may include a composite metal chalcogenide of the formula LiMQ2 (where M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr, and V, and Q is a chalcogen such as O or S). Among these, it is preferable to use a lithium-based composite metal oxide of the formula LiMO2 (where M is the same as defined above). Preferred examples thereof include LiCoO2, LiNiO2, LiNi x Co 1-x O2 (0 < x < 1) and spinel-structured LiMn2O4 may be mentioned. Another preferred example thereof is an oxide based on lithium-nickel-manganese-cobalt of the formula LiNi x Mn y Co z O2 (x + y + z = 1, called NMC), for example LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi0.6 Mn 0.2 Co 0.2 O2 and formula LiNi x Co y Al z Metal oxides based on lithium-nickel-cobalt-aluminum (x+y+z=1, called NCA), such as LiNi 0.8 Co 0.15 Al 0.05 O 2. These could be cited.

[0111] As an alternative, when forming a positive electrode for a lithium metal battery, the electroactive material of the positive electrode is given by formula M1M2(JO4) f E 1-f The formula may include a lithified or partially lithified transition metal oxyanion electroactive material (wherein M1 is lithium, which may be partially substituted by another alkali metal corresponding to less than 20% of the M1 metal; M2 is a transition metal with an oxidation level of +2 selected from Fe, Mn, Ni or mixtures thereof, which may be partially substituted by one or more further metals with oxidation levels of +1 to +5, corresponding to less than 35% of the M2 metal, including 0; JO4 is any oxyanion; J is any of P, S, V, Si, Nb, Mo or combinations thereof; E is a fluoride, hydroxide, or chloride anion; and f is typically the mole fraction of the JO4 oxyanion contained in 0.75 to 1).

[0112] M1M2(JO4) as defined above f E 1-f The electroactive material is preferably a phosphate-based material and may have a regular or modified olivine structure.

[0113] More preferably, the electroactive material of the positive electrode is Li 3-x M' y M'' 2-y(JO4)3 (where 0 ≦ x ≦ 3, 0 ≦ y ≦ 2, M’ and M’’ are the same or different metals, at least one of which is a transition metal, JO4 is preferably PO4 which may be partially substituted with another oxyanion, and J is any one of S, V, Si, Nb, Mo or a combination thereof). More preferably, the electroactive material has the formula Li(Fe x Mn 1-x )PO4 (where 0 ≦ x ≦ 1, and x is preferably 1 (i.e., lithium iron phosphate of the formula LiFePO4)), which is a phosphate-based electroactive material.

[0114] In a preferred embodiment, the electroactive material of the positive electrode is LiMQ2 (M is at least one metal selected from Co, Ni, Fe, Mn, Cr, and V; Q is O or S); LiNi x Co 1-x O2 (0 < x < 1); LiMn2O4 having a spinel structure; the formula LiNi x Mn y Co z O2 (x + y + z = 1) lithium-nickel-manganese-cobalt-based metal oxide, the formula LiNi x Co y Al z O2 (x + y + z = 1) lithium-nickel-cobalt-aluminum-based metal oxide, and is selected from the group consisting of LiFePO4.

[0115] As used herein, the term "separator" is intended to refer to a single-layer or multi-layer polymer, non-woven cellulose or ceramic material / membrane that electrically and physically separates electrodes of opposite polarities within an electrochemical device and permits the passage of ions flowing therebetween.

[0116] In the present invention, the separator can be any porous substrate commonly used for separators of electrochemical devices.

[0117] In one embodiment, the separator is polyethylene terephthalate and polybutylene terephthalate PolyesterPolyphenylene sulfide, polyacetal, polyamide, polycarbonate, polyimide, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, polyethylene oxide, polyacrylonitrile, polyolefin (such as polyethylene and polypropylene), or mixtures thereof. Is it an object? A porous polymer material comprising at least one material selected from the group, which may be coated with inorganic nanoparticles.

[0118] Non-limiting examples of inorganic nanoparticles include SiO2, TiO2, Al2O3, and ZrO2.

[0119] In one particular embodiment, the separator is a polyester film coated with SiO2.

[0120] In another specific embodiment, the separator is a polyester film coated with Al2O3.

[0121] In another specific embodiment, the separator is a porous polymer material coated with polyvinylidene difluoride (PVDF).

[0122] If any disclosure of patents, patent applications, and published materials incorporated herein by reference conflicts with any description of this application to such an extent that it could obscure any term, the description herein shall prevail.

[0123] The present invention will be described in more detail below with reference to the following examples, but this is for illustrative purposes only and is not intended to limit the scope of the invention. [Examples]

[0124] raw materials BP120: Based on the total weight of fluorinated diethers with a boiling point of approximately 120°C synthesized in Solvay, 70% by weight of C6F 10 Fluorinated diether as a mixture containing H4O2 BP120*: Based on the total weight of fluorinated diethers synthesized in Solvay, with a boiling point of approximately 120°C, 45% by weight of C6F 10 Fluorinated diether as a mixture containing H4O2 BP80: Based on the total weight of fluorinated diethers with a boiling point of approximately 80°C synthesized in Solvay, 50% by weight of C6F 12 Fluorinated diether as a mixture containing H2O2 Fluorinated diether as a single compound of 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, synthesized in TFEE:Solvay, with a boiling point of approximately 160°C. TTE: A fluorinated monoether of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, which has a boiling point of approximately 93°C and is commercially available from SynQuest. DME: 1,2-dimethoxyethane, commercially available from Enchem. DMC: Dimethyl carbonate, commercially available from Enchem. EC: Ethylene carbonate, commercially available from Enchem. EMC: Ethyl methyl carbonate, commercially available from Enchem. Li salt: Lithium bis(fluorosulfonyl)imide (LiFSI), commercially available from Nippon Shokubai.

[0125] A / Electrolyte composition formulation: Electrolyte compositions were prepared for the examples of the present invention (E1-E2) and comparative examples (CE1-CE9). Their components are summarized in Table 1 below: [Table 1]

[0126] To prepare the E1 electrolyte composition, 1 M LiFSI, as a lithium salt, was dissolved in a mixture of 20% by volume of DME and 80% by volume of BP120 relative to the total volume of the electrolyte composition, and mixed in a glove box using a magnetic stirrer. All components were added to a single bottle and mixed until the solution became clear.

[0127] The electrolyte composition for E2 was prepared in the same manner as for E1, except that BP80 was used instead of BP120 as the diether fluoride compound. When preparing the electrolyte composition for CE1, a 1M solution of lithium salt was prepared by dissolving LiFSI in a mixture of EC and DMC in a volume ratio of 50:50.

[0128] The electrolyte composition for CE2 was prepared in the same manner as for CE1, except that LiFSI was dissolved in a mixture of EC, DMC, and BP120 in a volume ratio of 40:40:20 to prepare a 1M solution of lithium salt.

[0129] The electrolyte compositions for CE3 and CE4 were prepared in the same manner as for CE2, except that the volume ratios of EC, DMC, and BP120 were 25:25:50 and 10 / 10 / 80, respectively.

[0130] The electrolyte composition for CE5 was prepared in the same manner as for E1, except that TFEE was used instead of BP120 and the volume ratio of DME / TFEE was set to 40 / 60.

[0131] The electrolyte composition for CE6 was prepared in the same manner as for CE5, except that the volume ratio of DME to TFEE was changed from 40 / 60 to 20 / 80.

[0132] The electrolyte compositions for CE7 and CE8 were prepared in the same manner as for E1, except that BP120* and TTE were used instead of BP120, respectively.

[0133] When preparing the electrolyte for CE9, a 1M lithium salt solution was prepared by dissolving LiFSI in DME only. All components were added to a single bottle and mixed until the solution became clear.

[0134] B / Manufacturing of lithium metal batteries: A positive electrode composition was obtained by mixing LiCoO2, the conductive agent Super-P (commercially available from LiFUN Technology), polyvinylidene fluoride (PVDF), and N-methyl-2-pyrrolidone (NMP).

[0135] The positive electrode composition contained LiCoO2, a conductive agent, and PVDF in a weight ratio of approximately 97.8:1.2:1.0. This positive electrode composition was applied to the upper surface of an aluminum foil approximately 20 μm thick, and then heat-treated under vacuum at approximately 110°C to obtain the positive electrode.

[0136] A lithium metal battery, specifically a coin cell (CR2032 type), was fabricated by placing a polyethylene separator (commercially available from Tonen Corporation) with a thickness of approximately 20 μm between the positive electrode and lithium metal (commercially available from Honjo Metal Ltd.) obtained through the above process, which served as the negative electrode.

[0137] C / Cell activation and initial cell performance measurement 1. Formation (Activation of Lithium Metal Batteries): After manufacturing the coin cells, they were stored at 25°C for 10 hours (aging process). Then, the cells were charged to 4.4V and repeatedly discharged to 3.0V for 3 cycles to activate them.

[0138] 2. Measurement of Cyclic Performance: The cycle performance of each cell was evaluated. Then, each cell was subjected to repeated charge and discharge cycles. One cycle consisted of a charge phase with the charge current of C, followed by a discharge phase with the discharge current of C.

[0139] D / Performance measurement of lithium metal batteries The coin cells were tested under various conditions to verify their properties, as detailed below: i) Check the capacity of the 3 cycles Charging: Constant current and constant voltage of 0.1C / 4.2V / 0.05C (CC-CV) Discharge: 0.1C / 3.0V(CC) ii) Continuous cycle test (maximum 300 cycles) Charging: 0.5C / 4.4V / 0.05C (CC-CV) Discharge: 0.5C / 3.0V(CC)

[0140] E / cycle test - capacity maintenance: The cycle performance of each cell was evaluated. Then, each cell was subjected to repeated charge and discharge cycles. The results are shown in Table 2 below. [Table 2]

[0141] Figure 1 shows the number of cycles at an 80% capacity retention rate for Examples E1-E2 and Comparative Examples CE1-CE4 of the present invention as a function of the number of cycles. Note that the number of cycles at an 80% capacity retention rate for E1-E2 using the electrolyte composition of the present invention was significantly higher than that for Comparative Examples CE1-CE4.

[0142] Furthermore, as shown in Table 2 above, the average Coulomb efficiency (%) for E1-E2 was up to 220 cycles for E1 and up to 231 cycles for E2, and it should be noted that both E1 and E2 exceeded 99.9% and were superior to the comparative examples. The Coulomb efficiency of E1-E2 remained essentially constant up to at least about 180 cycles and decreased very slowly as the cycles increased further, whereas the Coulomb efficiency of CE1-CE4 decreased rapidly, mainly between about 10 and 40 cycles.

[0143] The electrolyte composition of CE6, a mixture of DME and TFEE (v / v 20 / 80), showed a relatively good capacity retention rate, i.e., 172 cycles with an 80% capacity retention rate, but this was still significantly lower than the 220 and 231 cycles of E1 and E2, respectively, according to the present invention. Furthermore, the average Coulomb efficiency (%) of CE6 was lower than the average Coulomb efficiency of E1 and E2.

[0144] The electrolyte composition of CE7 is a mixture of DME and BP120*, where BP120* is C6F in an amount of 45% by weight based on the total weight of fluorinated diethers with a boiling point of approximately 120°C. 10 The fluorinated diether was a mixture containing H4O2. The number of cycles at a capacity retention rate of 80% (187 cycles) was relatively high, the highest among comparative examples CE1 to CE9, but was about 15% lower than E1 according to the present invention and about 19% lower than E2. This represented a substantial difference in cycle performance. The average Coulomb efficiency (%) of CE7 (99.80%) was also relatively high, the highest among the comparative examples, but was still lower than the average Coulomb efficiency of E1-E2.

[0145] The electrolyte compositions E1 to E2 according to the present invention have been clearly demonstrated to exhibit excellent balanced performance in terms of both capacity retention and Coulomb efficiency.

Claims

1. An electrolyte composition for lithium metal batteries, a) At least one fluorinated diether containing 4 to 10 carbon atoms, represented by formula I. R １ -O-R ２ -O-R ３ (Equation I) (In the formula, each R １ and R ３ R is independently a fluorinated alkyl group. ２ is optionally a fluorinated alkyl group, and formula II C ａ F ｂ H ｃ (Formula II) (In the formula, a is an integer from 1 to 6, b+c is an integer from 2 to 10, and when b is 0, R １ and R ３ (is represented by (which does not independently possess H); b) at least one nonfluorinated ether; and c) At least one lithium salt; It contains, a) An electrolyte composition for lithium metal batteries, wherein the fluorinated diether is present in an amount of at least 50% by volume (vol%) based on the total volume of a) the fluorinated diether and b) the non-fluorinated ether.

2. a) The electrolyte composition for lithium metal batteries according to claim 1, wherein the fluorinated diether contains 5 to 8 carbon atoms.

3. an electrolyte composition for a lithium metal battery according to claim 1 or 2, comprising 60 to 90 volume% of a) the fluorinated diether and 10 to 40 volume% of b) the non-fluorinated ether, based on the total volume of a) the fluorinated diether and b) the non-fluorinated ether.

4. a) The electrolyte composition for lithium metal batteries according to any one of claims 1 to 3, wherein the molar ratio F / H of the fluorinated diether is 2.0 to 11.

0.

5. a) The fluorinated diether contains C in an amount of at least 50% by weight, based on the total weight of the fluorinated diether. ６ F １０ H ４ O ２ An electrolyte composition for lithium metal batteries according to any one of claims 1 to 4, comprising a mixture containing the following.

6. a) The fluorinated diether contains C in an amount of at least 50% by weight, based on the total weight of the fluorinated diether. ６ F １２ H ２ O ２ An electrolyte composition for lithium metal batteries according to any one of claims 1 to 4, comprising a mixture containing the following.

7. b) The electrolyte composition for lithium metal batteries according to any one of claims 1 to 6, wherein the non-fluorinated ether comprises dimethoxyethane (DME), 1,3-dioxolane (DOL), dibutyl ether, tetraethylene glycol dimethyl ether (TEGME), diethylene glycol dimethyl ether (DEGDME), diethylene glycol diethyl ether (DEGDEE), polyethylene glycol dimethyl ether (PEGDME), 2-methyltetrahydrofuran, tetrahydrofuran (THF), triethyl phosphate (TEP), and mixtures thereof.

8. c) The lithium salt is lithium hexafluorophosphate (LiPF) ６ ), lithium perchlorate (LiClO ４ ), lithium hexafluoroarsenate (LiAsF ６ ), lithium hexafluoroantimone (LiSbF ６ ), lithium hexafluorotantalate (LiTaF ６ ), lithium tetrachloroaluminate (LiAlCl ４ ), lithium tetrafluoroborate (LiBF ４ ), lithium chloroborate (Li ２ B １０ Cl １０ ), lithium fluoroborate (Li ２ B １０ F １０ ), Li ２ B １２ F ｘ H １２－ｘ (x=0~12);LiPF ｘ (R Ｆ ) ６－ｘ and LiBF ｙ (R Ｆ ) ４－ｙ (In the formula, R Ｆ is perfluorinated C １ ~C ２０ (Represents an alkyl group or a perfluorinated aromatic group, where x = 0 to 5 and y = 0 to 3), LiBF ２ [O ２ C (CX ２ ) ｎ CO ２ ], LiPF ２ [O ２ C (CX ２ ) ｎ CO ２ ] ２ LiPF ４ [O ２ C (CX ２ ) ｎ CO ２ ] (wherein X is H, F, Cl, C １ ~C ４ Selected from the group consisting of alkyl groups and fluorinated alkyl groups, n = 0 to 4), lithium trifluoromethanesulfonate (LiCF ３ SO ３ ), lithium bis(fluorosulfonyl)imide Li(FSO ２ ), ２ N(LiFSI), LiN(SO ２ C ｍ F ２ｍ＋１ )(SO ２ C ｎ F ２ｎ＋１ ), and LiC(SO ２ C ｋ F ２ｋ＋１ )(SO ２ C ｍ F ２ｍ＋１ )(SO ２ C ｎ F ２ｎ＋１ )(where k = 1 to 10, m = 1 to 10, and n = 1 to 10), LiN(SO ２ C ｐ F ２ｐ SO ２ ), and LiC(SO ２ C ｐ F ２ｐ SO ２ )(SO ２ C ｑ F ２ｑ＋１ )(where p = 1 to 10 and q = 1 to 10), lithium salts of chelated orthoborates and chelated orthophosphates, such as lithium bis(oxalato)borate [LiB(C ２ O ４ ), lithium bis(malonato)borate [LiB(O ２ CCH ２ CO ２ ), ２ , lithium bis(difluoromalonato)borate [LiB(O ２ C C F ２ CO ２ ), ２ , lithium (malonatooxalato)borate [LiB(C ２ O ２ )(O ４ CCH ２ CO ２ ), lithium (difluoromalonatooxalato)borate [LiB(C ２ O ２ )(O ４ )(O ２ CCF ２ CO ２ )], lithium tris(oxalate) phosphate [LiP(C) ２ O ４ ) ３ ], lithium tris(difluoromalonato) phosphate [LiP(O ２ CCF ２ CO ２ ) ３ ], lithium difluorophosphate (LiPO ２ F ２ The electrolyte composition for lithium metal batteries according to any one of claims 1 to 7, comprising lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI) and a mixture thereof.

9. c) The electrolyte composition for lithium metal batteries according to any one of claims 1 to 8, wherein the concentration of the lithium salt is 1 M to 8 M.

10. d) The electrolyte composition for lithium metal batteries according to any one of claims 1 to 9, further comprising 5 to 50% by weight of at least one fluorinated organic carbonate compound based on the total weight of the electrolyte composition.

11. d) The fluorinated organic carbonate compounds are 4-fluoroethylene carbonate, 4,5-difluoro-1,3-dioxolan-2-one, 4,5-difluoro-4-methyl-1,3-dioxolan-2-one, 4,5-difluoro-4,5-dimethyl-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, tetrafluoroethylene carbonate, 2 ,2,3,3-tetrafluoropropyl methyl carbonate, bis(2,2,3,3-tetrafluoropropyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2,2,2-trifluoroethyl methyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2-difluoroethyl methyl carbonate, 1-fluoroethyl methyl carbonate, 1-fluoroethyl propyl carbonate, 1-fluoroethyl ethyl carbonate, 1-fluoroethylphenyl carbonate, 1-fluoroethyl-2,2,2-trifluoroethyl carbonate, allyl-1-fluoroethyl methyl carbonate, 2-cyanoethyl-1-fluoroethyl carbonate, 1-fluoroethylpropanyl carbonate, 4-(2,2-difluoroethoxy)ethylene carbonate, 4-(2,2,2-trifluoroethoxy)ethylene carbonate, ethyl-fluoro(phenyl)methyl carbonate The electrolyte composition for lithium metal batteries according to claim 10, comprising: nate, tris(trifluoroethyl) phosphate, methyl-3,3,3-trifluoropropanonate, 3-((2-oxo-1,3-dioxolan-4-yl)oxy)propanenitrile, 2,2-difluoroethyl methyl carbonate, 2,2-difluoroethyl acetate, 2,2-difluoroethyl methyl carbonate, 2,2-difluoroethyl propionate, and mixtures thereof.

12. e) The electrolyte composition for lithium metal batteries according to any one of claims 1 to 11, further comprising at least one film-forming additive in an amount of 0.05 to 5.0% by weight relative to the total weight of the electrolyte composition.

13. e) The film-forming additive comprises cyclic sulfites and sulfate compounds including 1,3-propanesultone (PS), ethylene sulfite (ES), and prop-1-ene-1,3-sultone (PES); sulfone derivatives including dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethylmethyl sulfone, and isopropylmethyl sulfone; nitrile derivatives including succinonitrile, adiponitrile, glutalonitrile, and 4,4,4-trifluoronitrile; lithium nitrate (LiNO2). ３ ); Boron derivative salts including lithium difluorooxalatoborate (LiDFOB) and lithium fluoromalonato(difluoro)borate (LiFMDFB); vinyl acetate, biphenylbenzene, isopropylbenzene, hexafluorobenzene, tris(trimethylsilyl) phosphate, triphenylphosphine, ethyldiphenylphosphinite, triethyl phosphite, tris(2,2,2-trifluoroethyl) phosphite, maleic anhydride, vinylene carbonate, vinyl ethylene carbonate, cesium bis(trifluorosulfonyl)imide (CsTFSI), cesium hexafluorophosphate (CsPF ６ ), cesium fluoride (CsF), trimethylboroxine (TMB), tributylborate (TBB), 2-(2,2,3,3,3-pentafluoropropoxy)-1,3,2-dioxaphosphoran (PFPOEPi), 2-(2,2,3,3,3-pentafluoropropoxy)-4-(trifluoromethyl)-1,3,2-dioxaphosphoran (PFPOEPi-1CF ３ ), lithium hexafluorophosphate (LiPF) ６ ), silver nitrate (AgNO) ３ ), silver hexafluorophosphate (AgPF ６ The electrolyte composition for lithium metal batteries according to claim 12, comprising tris(trimethylsilyl)phosphine (TMSP), 1,6-divinylperfluorohexane, and a mixture thereof.

14. Lithium metal battery, - A negative electrode containing lithium metal; -Positive electrode; - Separator, and - Electrolyte composition according to any one of claims 1 to 13 Lithium metal batteries, including those containing lithium metal.

15. The lithium metal battery according to claim 14, wherein the separator is a porous polymer material comprising at least one material selected from the group consisting of polyester, polyphenylene sulfide, polyacetal, polyamide, polycarbonate, polyimide, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylenenaphthalene, polyethylene oxide, polyacrylonitrile, polyolefin (such as polyethylene and polypropylene), or mixtures thereof, which may be coated with inorganic nanoparticles.

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