Liquid electrolytes for lithium metal batteries

Abstract

The present invention provides a liquid electrolyte for a lithium metal battery, comprising: 1 -OR 2 -OR 3 (In the formula, each R 1 and R 3 are independently fluorinated alkyl groups; R 2 a) at least one fluorinated diether containing 4 to 10 carbon atoms, represented by formula (I) of formula (I): (wherein R is an optionally fluorinated alkyl group); b) at least one non-fluorinated ether; c) at least one lithium salt; d) lithium hexafluorophosphate (LiPF6) in an amount of 5 weight percent (wt%) or less, preferably 3 weight percent or less, more preferably 1 weight percent or less, based on the total weight of the liquid electrolyte, where 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; and c) the lithium salt is different from d) LiPF6. The present invention also relates to a lithium metal battery comprising an anode comprising lithium metal; a cathode; a separator; and a liquid electrolyte according to the present invention.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to European Patent Application No. 22161264.1, filed March 10, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention provides a liquid electrolyte for a lithium metal battery, comprising: 1 -OR 2 -OR 3 (In the formula, each R 1 and R 3 are independently fluorinated alkyl groups; R 2 a) at least one fluorinated diether containing 4 to 10 carbon atoms, represented by formula I) of the formula I, where R is an optionally fluorinated alkyl group; b) at least one non-fluorinated ether; c) at least one lithium salt; and d) lithium hexafluorophosphate (LiPF ) in an amount of 5 weight percent (wt %) or less, preferably 3 weight percent or less, and more preferably 1 weight percent or less, based on the total weight of the liquid electrolyte. 6 ), 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; and c) the lithium salt is d) LiPF 6 The present invention also relates to a lithium metal battery comprising an anode comprising lithium metal, a cathode, a separator and a liquid electrolyte according to the present invention. [Background technology]

[0003] Lithium-ion batteries have held a dominant position in the market of rechargeable energy storage devices thanks to their many advantages, such as light weight, reasonable energy density, and good cycle life. Nevertheless, current lithium-ion batteries still suffer from a relatively low energy density with respect to the required energy density, which is continuously increasing to meet the needs of high-power applications, such as electric vehicles, hybrid electric vehicles, grid energy storage (also known as large-scale energy storage), etc.

[0004] The use of lithium metal as an anode has been known since the 1970s, thanks to the favorable properties of lithium metal resulting from its low redox potential and high specific capacity. Such lithium metal batteries usually use conventional liquid electrolytes, such as carbonate-based electrolytes and / or ether-based electrolytes with low viscosity and high ionic conductivity. However, these liquid electrolytes easily decompose at the beginning of a cycle to create a passivation layer, which ultimately leads to the growth of dendrites and also further side reactions between the electrolyte and the deposited reactive lithium ions. These have been key issues that have hindered the commercialization of lithium metal batteries.

[0005] The basic requirements of a suitable electrolyte for lithium metal batteries are the same as those of conventional liquid electrolytes for lithium ion batteries: high ionic conductivity, low melting and high boiling points, (electro)chemical stability and also safety. In addition to the above basic requirements, a suitable electrolyte for lithium metal batteries should provide a solution to the shortcomings as mentioned above.

[0006] The use of solid electrolytes instead of liquid electrolytes has been considered as a solution to reduce or suppress lithium dendrite formation and to improve the cycling performance of lithium metal batteries. For example, R. Sudo et al., in Solid State Ionics, 262, 151 (2014), reported the use of Al-doped Li as a solid electrolyte in an electrochemical cell containing Li metal as the negative electrode. 7 La 3 Zr 2 O12 The use of is described.

[0007] D. Aurbach et al. in Solid State Ionics, 148, 405 (2002) and H. Ota et al. in Electrochimica Acta, 49, 565 (2004) 2 , S.O. 2 and vinylene carbonate are reported to help improve the stability of the passivation layer.

[0008] Despite such efforts, the appearance of lithium dendrites was still observed and the additive was consumed during operation of the cell such that the use of the additive could not provide a long-term solution against dendrite formation.

[0009] Various other approaches for the same purpose have been carried out by modifying the liquid electrolyte, for example by using a liquid electrolyte with a high lithium salt concentration in dimethoxyethane (DME)-1,3-dioxolane (DOL) (1:1 v:v) to suppress lithium dendrite formation [L. Suo et al. in Nature Communications, DOI: 10.1038 / ncomms2513 (2013)]; and by applying solvated ionic liquids of tetraglyme (G4) and LiFSI as electrolytes [H. Wang et al. in Chem Electro Chem, 2, 1144 (2015)].

[0010] WO 2015 / 078791 A1 (Solvay Specialty Polymers Italy SPA) discloses electrolyte formulations comprising a hydrofluoroether as an essential component of the electrolyte mixture and also a polar organic solvent, in particular an organic carbonate.

[0011] In particular, European Patent Specification No. 3118917 B1 (Samsung Electronics Co., Ltd.) discloses an electrolyte for a lithium metal battery, comprising a non-fluorinated ether capable of solvating lithium ions, a fluorinated ether that is a glyme-based solvent having a specific formula, and a lithium salt, wherein the amount of the fluorinated ether is greater than the amount of the non-fluorinated ether.

[0012] In addition, WO 2021 / 213743 (Solvay SA) discloses an anode-less lithium-ion battery comprising a liquid electrolyte composition comprising at least one fluorinated ether, at least one non-fluorinated ether, and at least one lithium salt.

[0013] However, there remains an unmet need to provide electrolytes for lithium metal batteries that provide improved cell performance, such as safety, while minimizing dendritic growth and side reactions between the liquid electrolyte and the anode. Summary of the Invention

[0014] The present invention provides a liquid electrolyte for a lithium metal battery, comprising: a) Formula I R 1 -OR 2 -OR 3 (Formula I) (In the formula, each R 1 and R 3 are independently fluorinated alkyl groups; R 2 is an optionally fluorinated alkyl group. and at least one fluorinated diether containing 4 to 10 carbon atoms represented by the formula: b) at least one non-fluorinated ether; c) at least one lithium salt; d) lithium hexafluorophosphate (LiPF ) in an amount of 5 weight percent (wt %) or less, preferably 3 weight percent or less, and more preferably 1 weight percent or less, based on the total weight of the liquid electrolyte. 6 ) and 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; and c) the at least one lithium salt is d) LiPF 6 Different from, Concerning liquid electrolytes.

[0015] The present invention also relates to a lithium metal battery comprising an anode comprising lithium metal, a cathode, a separator, and a liquid electrolyte according to the present invention.

[0016] Surprisingly, the inventors have found that the above technical problems can be solved by using a liquid electrolyte for a lithium metal battery according to the present invention, which is evidenced by the excellent capacity retention. In particular, the inventors have found that c) a lithium salt is combined with LiPF 6 It was found that the incorporation of LiPF contributes to improving the cycle retention rate. 6 LiPF, which is incorporated into a liquid electrolyte in addition to the lithium salt, 6 It is believed that this supports the formation of a more resistive solid electrolyte interface (SEI) layer, reducing the initial discharge capability. [Brief description of the drawings]

[0017] [Figure 1] Figure 1 shows the cycle retention (%) of LiCoO2 / Li cells with liquid electrolytes E1 and CE1-CE3 at 3.0-4.4V (0.5C / 0.5C). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] definition Throughout this specification, unless the context requires otherwise, the words "comprise" or "include", or variations such as "comprises", "including", "includes", "comprising" and the like, will be understood to imply the inclusion of a stated element or method step or group of elements or method steps, but not the exclusion of any other element or method step or group of elements or method steps. According to a preferred embodiment, the words "comprise" and "comprises" and variations thereof mean "consisting exclusively of".

[0019] As used herein, the singular forms "a", "an" and "the" include plural aspects unless the context clearly indicates otherwise. The term "and / or" includes the meaning "and", "or" and also all other possible combinations of the elements associated with this term.

[0020] The term "~" should be understood to be inclusive.

[0021] As used herein, "alkyl" groups include saturated hydrocarbons having one or more carbon atoms, including straight-chain alkyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and the like; cyclic alkyl groups (or "cycloalkyl" or "alicyclic" or "carbocyclic" groups), such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl; branched-chain alkyl groups, such as isopropyl, tert-butyl, sec-butyl, and isobutyl; and alkyl-substituted alkyl groups, such as alkyl-substituted cycloalkyl groups and cycloalkyl-substituted alkyl groups.

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

[0023] As used herein, the terminology for organic groups is “(C n ~C m )" (where n and m are each integers) indicates that the group may contain from n carbon atoms to m carbon atoms per group.

[0024] Ratios, concentrations, amounts, and other numerical data may be presented in range format herein. It should be understood that such range formats are used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly recited as the upper and lower limits of the range, but also to include all individual numerical values ​​or subranges contained within the range as if each numerical value and subrange were explicitly recited. For example, a temperature range of about 120°C to about 150°C should be interpreted not only to include the explicitly recited upper and lower limits of about 120°C to about 150°C, but also to include subranges such as 125°C to 145°C, 130°C to 150°C, etc., and individual amounts, such as fractional amounts, within the stated range, such as, for example, 122.2°C, 140.6°C, and 141.3°C.

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

[0026] The components of a lithium metal battery, including an anode containing lithium metal, a cathode, a separator, and a liquid electrolyte according to the present invention, are described in detail herein below. It should be understood that both the foregoing summary and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed. Thus, various changes and modifications described herein will be apparent to those skilled in the art. Furthermore, descriptions of well-known functions and structures may be omitted for clarity and brevity.

[0027] The present invention provides a liquid electrolyte for a lithium metal battery, comprising: a) Formula I R 1 -OR 2 -OR 3 (Formula I) (In the formula, each R 1 and R 3 are independently fluorinated alkyl groups; R 2 is an optionally fluorinated alkyl group. and at least one fluorinated diether containing 4 to 10 carbon atoms represented by the formula: b) at least one non-fluorinated ether; c) at least one lithium salt; d) lithium hexafluorophosphate (LiPF ) in an amount of 5% by weight or less, preferably 3% by weight or less, and more preferably 1% by weight or less, based on the total weight of the liquid electrolyte. 6 )and Including, wherein a) the fluorinated diether is a) a fluorinated diether and b) a non-fluorinated ether; and c) d) LiPF 6 In an amount of at least 50% by volume (vol%), based on the total volume of at least one lithium salt different from Concerning liquid electrolytes.

[0028] In one embodiment, a) the fluorinated diether contains 5 to 8 carbon atoms.

[0029] In other embodiments, a) the fluorinated diether contains 8 carbon atoms.

[0030] In another embodiment, a) the fluorinated diether contains 7 carbon atoms.

[0031] In a preferred embodiment, a) the fluorinated diether contains 6 carbon atoms.

[0032] In one embodiment, a) the molar ratio F / H in the fluorinated diether is from 1.3 to 13.0, preferably from 2.5 to 6.0.

[0033] In one embodiment, a) the fluorinated diether is acyclic.

[0034] In the present invention, the term "fluorinated acyclic diether" is intended to mean an acyclic diether compound in which at least one hydrogen atom is replaced by fluorine. One, two, three or a higher number of hydrogen atoms may be replaced by fluorine.

[0035] In the present 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 and the liquid changes its physical state to vapor. The boiling point of a liquid substance varies depending on the surrounding environmental pressure, and the boiling point according to the present invention corresponds to the boiling point when the liquid is at atmospheric pressure, also known as the atmospheric boiling point.

[0036] In one embodiment, the boiling point of the a) fluorinated diether is at least 80°C, preferably 80°C to 160°C, more preferably 100°C to 160°C.

[0037] In one embodiment, the liquid electrolyte according to the present invention contains, relative to the total volume of the fluorinated diether and the non-fluorinated ether, - 60-90% by volume of at least one fluorinated ether compound; - 10 to 40% by volume of at least one non-fluorinated ether compound; Includes.

[0038] In another embodiment, the liquid electrolyte according to the present invention contains, relative to the total volume of the fluorinated diether and the non-fluorinated ether, - 80-90% by volume of at least one fluorinated diether compound; - 10 to 20% by volume of at least one non-fluorinated ether compound; Includes.

[0039] Non-limiting examples of a) fluorinated diethers suitable according to the present invention include, inter alia, the following: CF 3 CH 2 -O-CF 2 CHF-O-CF 3、 CHF 2 CH 2 -O-CF 2 CF 2 -O-CF 3、 CF 3 CF 2 -O-CHFCHF-O-CHF 2、 CHF 2 CF 2 -O-CHFCHF-O-CF 3、 CF 3 CHF-O-CHFCF 2 -O-CHF 2、 CF 3 CHF-O-CF 2 CHF-O-CHF 2、 CH 3 CF 2 -O-CF 2 -O-CF 2 CF 3、 CFH 2 CHF-O-CF 2 -O-CF 2 CF 3、 CF 3 CF 2 -O-CHF-O-CHFCHF 2、 CF 3 CF 2 -O-CHF-O-CHFCHF 2、 CF 3 CH 2 -O-CF 2 CF 2 -O-CF 3、 CHF 2 CHF-O-CF 2 CF 2 -O-CF 3、 CH 2 FCF 2 -O-CF 2 CF 2 -O-CF 3、 CF 3 CF 2 -O-CHFCHF-O-CF3、 CF 3 CF 2 -O-CF 2 CH 2 -O-CF 3、 CF 3 CF 2 -O-CH 2 CF 2 -O-CF 3、 CF 3 CF 2 -O-CF 2 CFH-O-CHF 2, CF 3 CHF-O-CHFCF 2 -O-CF 3、 CF 3 CHF-O-CF 2 CHF-O-CF 3, CHF 2 CF 2 -O-CF 2 CHF-O-CF 3, CHF 2 CF 2 -O-CHFCF 2 -O-CF 3、 CHF 2 CF 2 -O-CF 2 CF 2 -O-CHF 2, CF 3 CHF-O-CF 2 CF 2 -O-CHF 2, CF 3 CF 2 -O-CF 2 -O-CHFCF 3 、CF 2 HCF 2 -O-CF 2 -O-CF 2 CF 3、 CF 3 CHF-O-CF 2 -O-CF 2 CF 3、 CF 3 CF 2 -O-CHF-O-CF 2 CF 3、 CF 3 CF 2 -O-CF 2 -O-CF2 CHF 2、 CF 2 HCF 2 -O-CF 2 CH 2 -O-CF 2 CF 2 H、CF 3 CF 2 -O-CH 2 CH 2 -O-CF 2 CF 3、 CF 2 HCF 2 -O-CHFCHF-O-CF 2 CF 2 H、CF 3 CF 2 -O-CHFCH 2 -O-CF 2 CF 2 H、CF 3 CF 2 -O-CH 2 CHF-O-CF 2 CF 2 H、CF 3 -O-CHFCF 2 CH 2 -O-CF 2 CF 2 H、CF 2 HCF 2 -O-CF 2 CF 2 -O-CF 2 CF 2 H、CF 3 CF 2 -O-CF 2 CHF-O-CF 2 CF 2 H、CF 3 CF 2 -O-CHFCF 2 -O-CF 2 CF 2 H、CF 3 CF 2 -O-CF 2 CH 2 -O-CF 2 CF 3 、CF 3 CF 2 -O-CHFCHF-O-CF 2 CF 3 、CF2 HCF 2 -O-CH 2 CH 2 -O-CF 2 CF 2 H, C.F. 2 HCF 2 -O-CF 2 CHF-O-CF 2 CF 2 H, and mixtures thereof.

[0040] In one embodiment, a) the fluorinated diether is CF 2 HCF 2 -O-CF 2 CH 2 -O-CF 2 CF 2 H, C.F. 3 CF 2 -O-CH 2 CH 2 -O-CF 2 CF 3、 CF 2 HCF 2 -O-CHFCHF-O-CF 2 CF 2 H, C.F. 3 CF 2 -O-CHFCH 2 -O-CF 2 CF 2 H, C.F. 3 CF 2 -O-CH 2 CHF-O-CF 2 CF 2 H, C.F. 2 HCF 2 -O-CF 2 CF 2 -O-CF 2 CF 2 H, C.F. 3 CF 2 -O-CF 2 CHF-O-CF 2 CF 2 H, C.F. 3 CF 2 -O-CHFCF 2 -O-CF 2 CF 2 H, C.F. 3 CF 2-O-CF 2 CH 2 -O-CF 2 CF 3 , C.F. 3 CF 2 -O-CHFCHF-O-CF 2 CF 3 , C.F. 2 HCF 2 -O-CH 2 CH 2 -O-CF 2 CF 2 H, C.F. 2 HCF 2 -O-CF 2 CHF-O-CF 2 CF 2 H, and mixtures thereof.

[0041] In a preferred embodiment, a) the fluorinated diether is CF 2 HCF 2 -O-CH 2 CH 2 -O-CF 2 CF 2 H, C.F. 2 HCF 2 -O-CHFCHF-O-CF 2 CF 2 H, C.F. 2 HCF 2 -O-CF 2 CHF-O-CF 2 CF 2 H, and mixtures thereof.

[0042] In a more preferred embodiment, a) the fluorinated diether is CF 2 HCF 2 -O-CH 2 CH 2 -O-CF 2 CF 2 It's H.

[0043] In the present invention, the term "non-fluorinated ether" is intended to mean an ether compound in which no fluorine atoms are present.

[0044] Non-limiting examples of suitable b) non-fluorinated ether compounds according to the present invention include, inter alia, the following: aliphatic, cycloaliphatic or aromatic ethers, more particularly 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); and - glycol ether esters such as ethylene glycol methyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate Examples include:

[0045] In a preferred embodiment, the b) non-fluorinated ethers according to the present invention include dimethoxyethane (DME), 1,3-dioxolane (DOL), dibutyl ether, tetraethylene glycol dimethyl ether (TEGME), diethylene glycol dimethyl ether (DEGME), diethylene glycol diethyl ether (DEGDEE), polyethylene glycol dimethyl ether (PEGDME), 2-methyltetrahydrofuran, and tetrahydrofuran (THF).

[0046] In a more preferred embodiment, b) the non-fluorinated ether is a mixture of DME and DOL.

[0047] In another more preferred embodiment, b) the non-fluorinated ether is DME.

[0048] Non-limiting examples of c) lithium salts according to the present invention include, inter alia, the following: Lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium hexafluoroantimonate (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 (wherein x=0 to 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, x=0-5, and y=0-3), lithium bis(oxalato)borate [LiB(C 2 O 4 ) 2 ], lithium bis(malonato)borate [LiB(O 2 CCH 2 CO 2 ) 2 ], lithium bis(difluoromalonato)borate [LiB(O 2 CCF 2 CO2 ) 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 alkyl groups and fluorinated alkyl groups, n=0-4), 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 ) (wherein 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 ) (wherein p=1 to 10 and q=1 to 10), and mixtures thereof.

[0049] In one embodiment, the lithium salt c) according to the present invention is lithium perchlorate (LiClO 4), lithium hexafluoroarsenate (LiAsF 6 ), lithium hexafluoroantimonate (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 (wherein x=0 to 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, x=0 to 5, and y=0 to 3), 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 ) (wherein 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 ) (wherein p=1-10 and q=1-10), and mixtures thereof.

[0050] In the present invention, the lithium salt d) is LiPF 6 is different.

[0051] In one embodiment, d) the lithium salt is lithium bis(trifluorosulfonyl)imide (LiN(CF 3 SO 2 ) 2 )(LiTFSI).

[0052] In another embodiment, d) the lithium salt is LiFSI.

[0053] In one embodiment, the molar concentration (M) of the lithium salt in the liquid electrolyte according to the present invention is 0.5M to 8M, preferably 0.7M to 3M, and more preferably 1M to 2M.

[0054] The liquid electrolyte according to the present invention contains d) lithium hexafluorophosphate (LiPF ) in an amount of 5% by weight or less, preferably 3% by weight or less, more preferably 1% by weight or less, based on the total weight of the liquid electrolyte. 6 ).

[0055] The present inventors have also discovered that the lithium salt is in the form of a 5% by weight or less lithium salt. 6 It was found that the cycle retention rate could be improved by incorporating LiPF 6 c) LiPF 6 contributes to the decrease in initial discharge capacity and also to the formation of a more resistive solid electrolyte interface (SEI) layer on the surface of the electrode.

[0056] According to one embodiment, the liquid electrolyte according to the invention further comprises e) at least one film-forming additive, which promotes the formation of an SEI layer at the anode surface by reacting on the anode surface prior to the solvent. 2 CO 3 (LiCoO as cathode electroactive material 2 In the case of (a), the decomposition products of the liquid electrolyte and the salts may include lithium alkyl carbonates, lithium alkyl oxides, and other salt moieties such as LiF.

[0057] In the present invention, e) the film-forming additive is different from c) the lithium salt and d) LiPF 6 is different.

[0058] According to another embodiment, e) the film-forming additive stabilizes the cathode electrolyte interface (CEI) layer at the cathode surface by preventing structural changes of the cathode, especially under high voltage.

[0059] This is because e) the reduction potential of the film-forming additive is higher than that of the liquid electrolyte when the reaction occurs on the anode surface, and the oxidation potential of the film-forming additive is lower than that of the liquid electrolyte when the reaction occurs on the cathode side.

[0060] In one embodiment, the film-forming additive e) according to the present invention is selected from the group consisting of cyclic sulfite and sulfate compounds including 1,3-propane sultone (PS), ethylene sulfite (ES) and prop-1-ene-1,3-sultone (PES); sulfone derivatives including dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethyl methyl sulfone and isopropyl methyl sulfone; nitrile derivatives including succinonitrile, adiponitrile, glutaronitrile, and 4,4,4-trifluoronitrile; lithium nitrate (LiNO 3); boron derivative salts including lithium difluorooxalatoborate (LiDFOB), lithium fluoromalonato(difluoro)borate (LiFMDFB); vinyl acetate, biphenylbenzene, isopropylbenzene, hexafluorobenzene, tris(trimethylsilyl)phosphate, triphenylphosphine, ethyl diphenylphosphinite, triethyl phosphite, tris(2,2,2-trifluoroethyl)phosphite, maleic anhydride, vinylene carbonate, vinyl ethylene carbonate, monofluorinated ethylene carbonate (4-fluoro-1,3-dioxolan-2-one), difluorinated ethylene carbonate, cesium bis(trifluorosulfonyl)imide (CsTFSI) and cesium fluoride (CsF), and mixtures thereof.

[0061] In another embodiment, the film-forming additive e) according to the present invention is selected from the group consisting of 1,3-propane sultone (PS), ethylene sulfite (ES), prop-1-ene-1,3-sultone (PES), dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethyl methyl sulfone, isopropyl methyl sulfone, succinonitrile, adiponitrile, glutaronitrile, 4,4,4-trifluoronitrile, vinyl acetate, biphenylbenzene, isopropylbenzene, hexafluorobenzene, tris(trimethylsilyl)phosphate, triphenylphosphine, ethyl diphenylphosphinite, triethyl phosphite, tris(2,2,2-trifluoroethyl)phosphite, maleic anhydride, vinylene carbonate, vinyl ethylene carbonate, monofluorinated ethylene carbonate, difluorinated ethylene carbonate, cesium bis(trifluorosulfonyl)imide (CsTFSI) and cesium fluoride (CsF), and mixtures thereof.

[0062] In one preferred embodiment, e) the film-forming additive according to the present invention is vinylene carbonate.

[0063] In another preferred embodiment, the film-forming additive e) according to the present invention is lithium nitrate (LiNO3 ).

[0064] In another embodiment, e) the film-forming additive according to the present invention is an ionic liquid.

[0065] The term "ionic liquid" as used herein refers to compounds that contain positively charged cations and negatively charged anions and that are in the liquid state at atmospheric pressure and temperatures below 100° C. While ordinary liquids such as water are primarily composed of electrically neutral molecules, ionic liquids are primarily composed of ions and short-lived ion pairs. As used herein, the term "ionic liquid" refers to compounds that do not contain solvent.

[0066] The term "onium cation" as used herein refers to a positively charged ion with at least a portion of its charge localized on at least one non-metallic atom such as O, N, S, or P.

[0067] In the present invention, the ionic liquid is n- Q l+ (n / l) (In the formula, - A n- represents an anion; - Q l+ (n / l) represents a cation; n and l are independently selected from 1 to 5, each of which represents an anion A n- and cation Q l+ (n / l) represents the charge of It has the general formula:

[0068] The cations may be selected, independently of one another, from metal cations and organic cations. The cations may be monovalent or polyvalent cations.

[0069] Metal cations may preferably include alkali metal cations, alkaline earth metal cations and cations of d-block elements.

[0070] In the present invention, Q l+ (n / l) may 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 of the elements) with 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 can be a cation formed by atoms selected from the group consisting of N, P, O and S, more preferably N and P, with three or four hydrocarbon chains.

[0071] Onium Cation Q l+ (n / l) teeth, heterocyclic onium cations; in particular [ka] Selected from the group consisting of: unsaturated cyclic onium cations; in particular [ka] Selected from the group consisting of: saturated cyclic onium cations; in particular [ka] and - acyclic onium cations, especially those of the general formula + L-R' s wherein 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 the element L, and each R′ is independently a hydrogen atom or a C 1 ~C 8 represents an alkyl group, L + and R' may be a single or double bond. You can choose from.

[0072] In the above formula, each "R" symbol represents, independently of one another, a hydrogen atom or an organic group. Preferably, each "R" symbol represents, independently of one another, a hydrogen atom or a saturated or unsaturated, linear, branched or cyclic C 1 -C 2 -C 3 -C 4 -C 5 -C 6 -C 7 -C 8 -C 9 -C 10 -C 11 -C 12 -C 13 -C 14 -C 15 -C 16 -C 17 -C 18 -C 19 -C 20 -C 21 -C 22 -C 23 -C 24 -C 25 -C 26 -C 27 -C 28 -C 29 -C 30 -C 31 -C 32 -C 33 -C 34 -C 35 -C 36 -C 37 -C 38 -C 39 -C 40 -C 41 -C 1 ~C 18 It may represent a hydrocarbon group.

[0073] Cation Q l+ (n / l) may more particularly be selected from ammonium, phosphonium, pyridinium, pyrrolidinium, pyrazolinium, imidazolium, arsenium, quaternary phosphonium and quaternary ammonium cations.

[0074] The quaternary phosphonium or ammonium cation may more preferably be selected from tetraalkylammonium or tetraalkylphosphonium cations, trialkylbenzylammonium or trialkylbenzylphosphonium cations or tetraarylammonium or tetraarylphosphonium cations, the alkyl groups of which are either the same or different and represent linear or branched alkyl chains having from 4 to 12 carbon atoms, preferably from 4 to 6 carbon atoms, and the aryl groups of which are either the same or different and represent phenyl or naphthyl groups.

[0075] In certain embodiments, Q l+ (n / l) represents a quaternary phosphonium or quaternary ammonium cation.

[0076] In one preferred embodiment, Q l+ (n / l)represents a quaternary phosphonium cation. Non-limiting examples of quaternary phosphonium cations are trihexyl (tetradecyl) phosphonium, and tetraalkyl phosphonium cations, in particular tetrabutyl phosphonium (PBu 4 ) cations.

[0077] In another embodiment, Q l+ (n / l) represents the imidazolium cation. Non-limiting examples of the imidazolium cation 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.

[0078] In another embodiment, Q l+ (n / l) are 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 Aliquat 336 (methyltri(C 8 ~C 10 (a) a mixture of alkyl (quaternary ammonium compounds) and (b) a mixture of quaternary ammonium compounds.

[0079] In one embodiment, Q l+ (n / l) represents a piperidinium cation, in particular N-butyl-N-methylpiperidinium, N-propyl-N-methylpiperidinium.

[0080] In another embodiment, Q l+ (n / l) represents a pyridinium cation, in particular N-methylpyridinium.

[0081] In a more preferred embodiment, Q l+ (n / l) represents a pyrrolidinium cation. Among the specific pyrrolidinium cations are the following: 1~12 Alkyl-C 1~12 Alkyl-pyrrolidinium, more preferably C 1~4 Alkyl-C 1~4 Alkyl-pyrrolidinium may be mentioned. Examples of pyrrolidinium cations include, but are not limited to, 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).

[0082] Non-limiting examples of anions of ionic liquids include iodide, bromide, chloride, hydrogen sulfate, dicyanamide, acetate, diethyl phosphate, methyl phosphonate, fluorinated anions such as hexafluorophosphate (PF 6 - ) and tetrafluoroborate (BF 4 - ), as well as the following formula: [ka] Contains oxalatoborate.

[0083] In one embodiment, A n-is a fluorinated anion. Among the fluorinated anions that can be used in the present invention, fluorinated sulfonimide anions can be particularly advantageous. The organic anion is in particular a compound represented by the following general formula: (E a -SO 2 )N - R (In the formula: -E a represents a fluorine atom or a group selected from fluoroalkyl, perfluoroalkyl and fluoroalkenyl, preferably having 1 to 10 carbon atoms; - R represents a substituent. The anion may be selected from those having the following formula:

[0084] Preferably, E a is F or CF 3 can be represented as follows.

[0085] According to a first embodiment, R represents a hydrogen atom.

[0086] According to a second embodiment, R represents a linear or branched, cyclic or acyclic hydrocarbon-based group, preferably having from 1 to 10 carbon atoms, which may optionally have one or more unsaturations and which is optionally substituted one or more times with a halogen atom, with a nitrile function or with an alkyl group optionally substituted one or more times with a halogen atom. Furthermore, R may represent a nitrile group -CN.

[0087] According to a third embodiment, R represents a sulfinate group. In particular, R represents a group -SO 2 -E a (E a is as defined above). In this case, the fluorinated anion may be symmetric, i.e., the two E a The groups can be identical or asymmetric, i.e., the two E a The groups can be different.

[0088] Furthermore, R is a group -SO 2-R' may represent, preferably, a linear or branched, cyclic or acyclic hydrocarbon-based group having from 1 to 10 carbon atoms, which may optionally have one or more unsaturations and which is optionally substituted one or more times with a halogen atom, with a nitrile function or with an alkyl group which is optionally substituted one or more times with a halogen atom. In particular, R' may comprise a vinyl or allyl group. Furthermore, R may represent a group -SO 2 -N-R', where R' is as defined above or R' is a sulfonate functional group, -SO 3 (representing

[0089] The cyclic hydrocarbon-based group may preferably refer to a cycloalkyl group or to an aryl group. "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 fused or linked by σ (sigma) bonds.

[0090] According to a fourth embodiment, R represents a carbonyl group. R may in particular be represented by the formula -CO-R', where R' is as defined above.

[0091] The organic anion that can be used in the present invention is advantageously CF 3 SO 2 N - SO 2 CF 3 (bis(trifluoromethanesulfonyl)imide anion, commonly referred to as TFSI), FSO 2 N - SO 2 F (bis(fluorosulfonyl)imide anion, commonly referred to as FSI), CF 3 SO 2 N - SO 2 F, and CF 3 SO 2 N- SO 2 N - SO 2 CF 3 may be selected from the group consisting of:

[0092] In a preferred embodiment, the ionic liquid is - At least one C 1 ~C 30 a positively charged cation selected from the group consisting of imidazolium, pyridinium, pyrrolidinium and piperidinium ions, optionally containing an alkyl group; a negatively charged anion selected from the group consisting of halides, fluorinated anions, and borates; Contains:

[0093] C 1 ~C 30 Non-limiting examples of alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, 2,2-dimethyl-propyl, 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, among others.

[0094] In one preferred embodiment, the film-forming additive e) 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).

[0095] In the present invention, the total amount of e) the film-forming additive may be 0 to 30% by weight, preferably 0 to 20% by weight, more preferably 0 to 15% by weight, and even more preferably 0 to 5% by weight, based on the total weight of the liquid electrolyte.

[0096] e) The total amount of the film-forming additives, when contained in the liquid electrolyte of the present invention, is 0.05 to 10.0% by weight, preferably 0.05 to 5.0% by weight, and more preferably 0.05 to 2.0% by weight, based on the total weight of the liquid electrolyte.

[0097] In a preferred embodiment, the total amount of e) film-forming additives comprises at least 1.0% by weight of the liquid electrolyte.

[0098] The present invention also provides - an anode comprising lithium metal; - with the cathode; - with separator; a liquid electrolyte according to the invention; The present invention provides a lithium metal battery comprising:

[0099] In the present invention, the term "anode" is intended to mean in particular the electrode of an electrochemical cell where oxidation takes place during discharge.

[0100] In the present invention, the term "cathode" is intended to mean in particular the electrode of an electrochemical cell where reduction takes place during discharge.

[0101] In the present invention, the type of the "current collector" depends on whether the electrode provided thereby is a cathode or an anode. When the electrode of the present invention is a cathode, the current collector typically includes at least one metal selected from the group consisting of aluminum (Al), nickel (Ni), titanium (Ti), and alloys thereof, preferably includes Al, and is preferably composed of them. When the electrode of the present invention is an anode, the current collector typically includes at least one metal selected from the group consisting of lithium (Li), sodium (Na), zinc (Zn), magnesium (Mg), copper (Cu), and alloys thereof, preferably includes Cu, and is preferably composed of them.

[0102] In the present invention, the term "electroactive material" is intended to mean an electroactive material that can incorporate or insert lithium ions into its structure and substantially release them therefrom during the charging and discharging stages of the battery.

[0103] When forming a cathode for a lithium metal battery, the cathode electroactive material is not particularly limited. It may include a composite metal chalcogenide of the formula LiMQ 2 (wherein 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 LiMO 2 (wherein M is the same as defined above). Preferred examples thereof may include LiCoO 2 , LiNiO 2 , LiNi x Co 1-x O 2 (0 < x < 1), and spinel-structured LiMn 2 O 4 .

[0104] Another preferred example thereof is of the formula LiNi x Mn y Co z O 2(x+y+z=1, called NMC), e.g. LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 Lithium-nickel-manganese-cobalt metal oxide, with the formula LiNi x Co y Al z O 2 (x+y+z=1, called NCA), e.g. LiNi 0.8 Co 0.15 Al 0.05 O 2 Lithium-cobalt-aluminum-based metal oxides. Lithium-cobalt-based metal oxides, or lithium-nickel-manganese-based metal oxides (LNMO) may be mentioned as cathode electroactive materials.

[0105] Alternatively, when further forming a cathode for a lithium metal battery, the cathode electroactive compound can be of the formula M 1 M 2 (J.O. 4 ) f E 1-f (In the formula, M 1 is M 1 Lithium, which may be partially replaced by another alkali metal representing less than 20% of the metal; M 2 M is a metal with oxidation levels from +1 to +5, including 0. 2 a transition metal at an oxidation level of +2 selected from Fe, Mn, Ni or mixtures thereof, which may be partially replaced by one or more additional metals representing less than 35% of the metal; 4 is any oxyanion, where J is any of P, S, V, Si, Nb, Mo, or a combination thereof, E is a fluoride, hydroxide, or chloride anion, and f is generally comprised between 0.75 and 1; JO 4 The lithiated or partially lithiated transition metal oxyanion based electroactive material may comprise a lithiated or partially lithiated transition metal oxyanion based electroactive material having a molar fraction of oxyanion of at least one of the lithiated or partially lithiated transition metal oxyanion.

[0106] M as defined above 1 M 2 (JO 4 ) f E 1-f The electroactive material is preferably phosphate-based and may have an ordered or modified olivine structure.

[0107] More preferably, the cathode electroactive material has the formula Li 3-x M’ y M’’ 2-y (JO 4 ) 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, and JO 4 is preferably PO 4 which may be partially substituted with another oxyanion, where J is any of S, V, Si, Nb, Mo or a combination thereof). Even more preferably, the electroactive material has the formula Li(Fe x Mn 1-x )PO 4 (where 0 ≦ x ≦ 1 and x is preferably 1 (i.e., lithium iron phosphate of the formula LiFePO 4 )) and is a phosphate-based electroactive material.

[0108] In a preferred embodiment, the cathode electroactive material is LiMQ 2 (where M is at least one metal selected from Co, Ni, Fe, Mn, Cr and V, and Q is O or S); LiNi x Co 1-x O 2 (where 0 < x < 1); spinel-structured LiMn 2 O 4 ; the lithium-nickel-manganese-cobalt-based metal oxide of the formula LiNi x Mn y Co z O 2 (where x + y + z = 1), the lithium-nickel-cobalt-aluminum-based metal oxide of the formula LiNi x Co y Al z O 2Lithium-nickel-cobalt-aluminum-based metal oxides, where x+y+z=1, and LiFePO 4 is selected from the group consisting of:

[0109] In another preferred embodiment, the cathode has the formula LiNi x Mn y Co z O 2 Lithium-nickel-manganese-cobalt metal oxide, with x+y+z=1, formula LiNi x Co y Al z O 2 The cathode electroactive material comprises a lithium-nickel-cobalt-aluminum metal oxide, a lithium-cobalt metal oxide, or a lithium-nickel-manganese metal oxide (LNMO), where x+y+z=1.

[0110] In one embodiment, at least one electroactive compound according to the present invention has a density of 1.0 mAh / cm 2 ~10.0mAh / cm 2 , preferably 3.0 mAh / cm 2 ~8.0mAh / cm 2 , more preferably 4.0 mAh / cm 2 ~7.0mAh / cm 2 is loaded onto the cathode current collector to have an areal capacity of

[0111] In the present invention, the expression "cathode thickness" is intended to mean the total combined thickness of the cathode current collector and the cathode electroactive material layer.

[0112] In one embodiment, the cathode according to the present invention has a thickness of 40 μm to 150 μm, preferably 50 μm to 120 μm, and more preferably 60 μm to 100 μm.

[0113] The term "separator" is intended herein to mean a single or multi-layer polymeric, non-woven cellulosic or ceramic material / membrane that electrically and physically separates electrodes of opposite polarity in an electrochemical device and is permeable to ions flowing between them.

[0114] In the present invention, the separator can be any porous substrate commonly used for separators in electrochemical devices.

[0115] In one embodiment, the separator is a porous polymeric material comprising at least one material selected from the group consisting of polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyphenylene sulfide, polyacetal, polyamide, polycarbonate, polyimide, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, polyethylene oxide, polyacrylonitrile, polyolefins such as polyethylene and polypropylene, or mixtures thereof.

[0116] In certain embodiments, the separator is made of inorganic nanoparticles, such as SiO 2 , TiO 2 , Al 2 O 3 , ZrO 2 and the like.

[0117] In another particular embodiment, the separator is a porous polymeric material coated with polyvinylidene difluoride (PVDF).

[0118] To the extent that the disclosures of any patents, patent applications, and publications incorporated herein by reference conflict with the statements of this application to the extent that any term may be unclear, this statement shall control.

[0119] The invention will now be described in more detail with reference to the following examples, the purpose of which is merely illustrative and is not intended to limit the scope of the invention. EXAMPLES

[0120] raw materials Fluorinated diethers: - C of 160°C bp, synthesized in Solvey 6 F 8 H 6 O 2 (CF 2 HCF 2 -OCH 2 CH 2 O-CF 2 CF 2 H) (hereinafter referred to as BP160) - C, synthesized in Solvey, with a boiling point of about 100°C 6 F 11 H 3 O 2 (hereinafter referred to as BP100) Fluorinated monoethers: - 1,1,2,2-Tetrafluoroethyl-2,2,2-trifluoroethyl ether (CF 3 CH 2 OCF 2 CF 2 H) (hereinafter referred to as HFE-347) Non-fluorinated ethers: - 1,2-dimethoxyethane (DME), available from Enchem Lithium salt: - Lithium bis(fluorosulfonyl)imide (LiFSI), available from Nippon Shokubai LiPF 6 ): Commercially available from Enchem

[0121] A / Liquid electrolyte formulation: Liquid electrolytes were prepared for the inventive example E1 and comparative examples CE1-CE3, the components of which are summarized in Table 1 below:

[0122] [Table 1]

[0123] To prepare the liquid electrolyte of E1, 1M LiFSI was first dissolved in 20% by volume of DME based on the total volume of DME and BP160 using a magnetic stirrer in a glove box and mixed. After the solution became clear, 80% by volume of BP160 based on the total volume of DME and BP160 was added to the solution. 1% by weight of LiPF (based on the total weight of the liquid electrolyte) was added to the solution. 6 was then added to the solution.

[0124] The liquid electrolyte for E2 was prepared similarly to E1, except that BP100 was used instead of BP160.

[0125] LiPF 6 The liquid electrolyte for CE1 was prepared similarly to E1, except that no was added.

[0126] To prepare the liquid electrolyte for CE2, 1 M LiFSI was first dissolved in DME and mixed using a magnetic stirrer in a glove box. 1 wt. % LiPF (based on the total weight of the liquid electrolyte) was added. 6 was then added to the solution.

[0127] LiPF 6 The liquid electrolyte for CE3 was prepared similarly to CE2, except that no was added.

[0128] LiPF 6 The liquid electrolyte for CE4 was prepared similarly to E2, except that no was added.

[0129] The liquid electrolyte for CE5 was prepared similarly to CE4, except that HFE-347 was used instead of BP100.

[0130] 1% by weight of LiPF based on the total weight of the liquid electrolyte 6 The liquid electrolyte for CE6 was prepared similarly to CE5, except that

[0131] B / Preparation of lithium metal batteries: LiCoO2 The cathode composition was prepared by mixing LiCoO 2 with a weight ratio of about 97.8:1.2:1.0, a conductive agent Super-P (available from LiFUN Technology), polyvinylidene fluoride (PVDF), and N-methyl-2-pyrrolidone (NMP). 2 , a conductive agent, and PVDF.

[0132] This cathode composition was coated on the upper surface of an aluminum foil with a thickness of about 20 μm, and then a heat treatment was applied at about 110° C. under vacuum to obtain a cathode.

[0133] A polyethylene separator (commercially available from Tonen Corporation) was placed with a thickness of about 20 μm between the cathode obtained according to the above process and lithium metal (commercially available from Honjo Metals Co., Ltd.) as the anode, thereby preparing a lithium metal battery as a coin cell (CR2032 type).

[0134] C / Cell activation and initial cell performance measurements 1- Formation (Activation of Lithium Metal Battery): After the coin cell fabrication, the cell was stored at 25° C. for 10 hours (aging process). The cell was then repeatedly charged to 4.4 V and discharged to 3.0 V for 3 cycles to activate the cell.

[0135] 2- Measurement of cycling performance: The cycling capability of each coin cell was evaluated. Each cell was then subjected to repeated cycles of charge and discharge. One cycle consisted of a charge phase with a charge current of C followed by a discharge phase with a discharge current of C.

[0136] D / Lithium metal battery performance measurement The coin cells were tested under various conditions as detailed below: Capacity check for 1-2 cycles Charging: Constant current and constant voltage (CC-CV) at 0.1C / 4.4V / 0.05C · Discharge: 0.1C / 3.0V(CC) 2-Continuous cycling test (up to 300 cycles) · Charging: 0.5C / 4.4V / 0.05C (CC-CV) · Discharge: 0.5C / 3.0V(CC)

[0137] E / Cycle Test-Capacity Retention: The cycling capability of each cell was evaluated and then each cell was subjected to repeated cycles of charge and discharge. One cycle consisted of a charge phase at a charge current of C followed by a discharge phase at a discharge current of C. The following results were obtained, as shown in Table 2 below:

[0138] [Table 2]

[0139] FIG. 1 shows the change in capacity retention of E1 and CE1-CE3 as a function of cycle number.

[0140] Notably, it was observed that the discharge capacity of E1 according to the present invention slowly decreased with increasing cycle number. In particular, FIG. 1 clearly shows that the cycle number at 80% capacity retention for the inventive example of E1, which contains the liquid electrolyte according to the present invention, was much higher than that for the comparative examples, i.e., CE1 to CE3. The difference in cycle number at 80% capacity retention for E2 and CE4 is due to the presence of 1 wt.% LiPF in addition to the lithium salt (1M LiFSI). 6 This clearly shows that the incorporation of

[0141] When a fluorinated monoether was incorporated instead of a fluorinated diether (CE5 and CE6), the number of cycles at 80% capacity retention was significantly higher than that of 1 wt.% LiPF 6 It was found that the fluorinated diethers (BP160 or BP100) but not LiPF 6 The activity of the CE1 and CE4 in the absence of CE1 was much inferior to that of CE4.

Claims

1. 1. A liquid electrolyte for a lithium metal battery, comprising: a) Formula I R １ -O-R ２ -O-R ３ (Formula I) (In the formula, each R １ and R ３ is independently a fluorinated alkyl group; R ２ is an optionally fluorinated alkyl group. at least one fluorinated diether containing 4 to 10 carbon atoms represented by b) at least one non-fluorinated ether; c) at least one lithium salt; d) lithium hexafluorophosphate (LiPF) in an amount of 5 weight percent (wt%) or less, preferably 3 wt% or less, and more preferably 1 wt% or less, based on the total weight of the liquid electrolyte. ６ )and Including, 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; and c) the at least one lithium salt is d) LiPF ６ Different from, liquid electrolyte.

2. 2. The liquid electrolyte for lithium metal batteries according to claim 1, wherein a) the fluorinated diether contains 5 to 8 carbon atoms, preferably 6 carbon atoms.

3. 3. The liquid electrolyte for lithium metal batteries according to claim 1 or 2, wherein a) the molar ratio F / H in said fluorinated diether is between 1.3 and 13.0, preferably between 2.5 and 6.

0.

4. A liquid electrolyte for lithium metal batteries according to any one of claims 1 to 3, wherein a) the boiling point of the fluorinated diether is at least 80°C, preferably between 80°C and 160°C, more preferably between 100°C and 160°C.

5. a) the fluorinated diether is CF ２ HCF ２ -O-CH ２ CH ２ -O-CF ２ CF ２ H, C.F. ２ HCF ２ -O-CHFCHF-O-CF ２ CF ２ H, C.F. ２ HCF ２ -O-CF ２ CHF-O-CF ２ CF ２ 5. The liquid electrolyte for a lithium metal battery according to claim 1, comprising:

6. b) The liquid electrolyte for a lithium metal battery according to any one of claims 1 to 5, 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), triethylphosphate (TEP), and mixtures thereof.

7. 7. A liquid electrolyte for a lithium metal battery according to claim 1, 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.

8. 8. The liquid electrolyte for a lithium metal battery of claim 7, comprising 80-90 volume % of a) the fluorinated diether and 10-20 volume % of b) the non-fluorinated ether, based on the total volume of a) the fluorinated diether and b) the non-fluorinated ether.

9. c) The lithium salt is lithium perchlorate (LiClO ４ ), lithium hexafluoroarsenate (LiAsF ６ ), lithium hexafluoroantimonate (LiSbF ６ ), lithium hexafluorotantalate (LiTaF ６ ), lithium tetrachloroaluminate (LiAlCl ４ ), lithium tetrafluoroborate (LiBF ４ ), lithium chloroborate (Li ２ B １０ C １０ ), lithium fluoroborate (Li ２ B １０ F １０ ), Li ２ B １２ F ｘ H １２－ｘ (wherein x=0 to 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, x=0 to 5, and y=0 to 3), 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 ) (wherein 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 9. The liquid electrolyte for lithium metal batteries according to any one of claims 1 to 8, selected from the group consisting of LiFSI, ...

10. A liquid electrolyte for lithium metal batteries according to any one of claims 1 to 9, wherein the concentration of the lithium salt is from 0.5M to 8M, preferably from 0.7M to 4M, more preferably from 1M to 2M.

11. 11. A liquid electrolyte for a lithium metal battery according to claim 1, further comprising e) at least one film-forming additive in an amount of 0.05 to 5.0 wt. %, preferably 0.05 to 3.0 wt. %, based on the total weight of the liquid electrolyte, wherein e) the film-forming additive is selected from c) the lithium salt and d) LiPF ６ A different liquid electrolyte.

12. e) The film-forming additives include cyclic sulfite and sulfate compounds including 1,3-propane sultone (PS), ethylene sulfite (ES) and prop-1-ene-1,3-sultone (PES); sulfone derivatives including dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethyl methyl sulfone and isopropyl methyl sulfone; nitrile derivatives including succinonitrile, adiponitrile, glutaronitrile and 4,4,4-trifluoronitrile; and lithium nitrate (LiNO ３ ); boron derivative salts including lithium difluorooxalatoborate (LiDFOB), lithium fluoromalonato(difluoro)borate (LiFMDFB), vinyl acetate, biphenylbenzene, isopropylbenzene, hexafluorobenzene, tris(trimethylsilyl)phosphate, triphenylphosphine, ethyldiphenylphosphinite, triethylphosphite, tris(2,2,2-trifluoroethyl)phosphite, maleic anhydride, vinylene carbonate, vinylethylene carbonate, cesium bis(trifluorosulfonyl)imide (CsTFSI), cesium hexafluorophosphate (CsPF ６ ), cesium fluoride (CsF), trimethylboroxine (TMB), tributyl borate (TBB), 2-(2,2,3,3,3-pentafluoropropoxy)-1,3,2-dioxaphospholane (PFPOEPi), 2-(2,2,3,3,3-pentafluoropropoxy)-4-(trifluoromethyl)-1,3,2-dioxaphospholane (PFPOEPi-1CF ３ ), silver nitrate (AgNO ３ ), silver hexafluorophosphate (AgPF ６ ), tris(trimethylsilyl)phosphine (TMSP), 1,6-divinylperfluorohexane, and mixtures thereof, preferably LiNO ３ 12. The liquid electrolyte for a lithium metal battery according to claim 11, wherein

13. an anode comprising lithium metal; a cathode; a separator; - a liquid electrolyte according to any one of claims 1 to 12; Lithium metal batteries including:

14. The cathode has the formula LiNi ｘ Mn ｙ Co ｚ O ２ Lithium-nickel-manganese-cobalt-based metal oxides, where x+y+z=1, of the formula LiNi ｘ Co ｙ A ｚ O ２ 14. The lithium metal battery of claim 13 comprising a lithium-nickel-cobalt-aluminum metal oxide, a lithium-cobalt metal oxide, or a lithium-nickel-manganese metal oxide (LNMO), where x+y+z=1, as the cathode electroactive material.

15. 15. The lithium metal battery of claim 13 or 14, wherein the separator is a porous polymeric material comprising at least one material selected from the group consisting of polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyphenylene sulfide, polyacetal, polyamide, polycarbonate, polyimide, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, polyethylene oxide, polyacrylonitrile, polyolefins such as polyethylene and polypropylene, and mixtures thereof, optionally coated with inorganic nanoparticles.

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