Liquid electrolytes for lithium secondary batteries

Abstract

The present invention provides a liquid electrolyte for a lithium secondary battery, comprising: a) a liquid electrolyte of formula (I)R 1 -OR 2 -OR 3 (In the formula, R 1 and R 3 each represents a fluorinated linear alkyl group; R 2 represents an optionally fluorinated linear alkylene group; and R 1 , R 2 and R 3 wherein the total carbon atoms in the formula (II) is 5 to 8, preferably 6; and b) at least one fluorinated acyclic diether represented by formula (II) R 4 -C(O)OR 5 (In the formula, R 4 and R 5 Each represents an alkyl group; R 4 and R 5 The total number of carbon atoms in R is 2 to 7; and R 5 wherein at least one hydrogen is replaced by fluorine; c) at least one organic carbonate; and d) at least one lithium salt. The present invention also relates to a lithium secondary battery comprising an anode, a cathode, a separator, and the liquid electrolyte according to the present invention.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to European Patent Application Publication No. 21167334.8, filed April 8, 2021, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a) Formula (I) R 1 -OR 2 -OR 3 (I) (In the formula, R 1 and R 3 each represents a fluorinated linear alkyl group; R 2 represents an optionally fluorinated linear alkylene group; and R 1 , R 2 and R 3 The total number of carbon atoms is 5 to 8, preferably 6. and at least one fluorinated acyclic diether represented by: b) Formula (II) R 4 -C(O)OR 5 (II) (In the formula, R 4 and R 5 Each represents an alkyl group; R 4 and R 5 The total number of carbon atoms in R is 2 to 7; and R 5 At least one hydrogen atom of the formula (I) is replaced by a fluorine atom. and at least one fluorinated acyclic carboxylic acid ester represented by: c) at least one organic carbonate; d) at least one lithium salt; The present invention relates to a liquid electrolyte for a lithium secondary battery, comprising:

[0003] The present invention also relates to a lithium secondary battery comprising an anode, a cathode, a separator and a liquid electrolyte according to the present invention. [Background technology]

[0004] For over 20 years, lithium secondary batteries, including lithium-ion batteries, have held a dominant position in the market of rechargeable energy storage devices due to their many advantages, including light weight, moderate energy density, and good cycle life. Nevertheless, current lithium secondary batteries still suffer from a relatively low energy density relative to the ever-increasing required energy density for high-power applications such as electric vehicles (EVs), hybrid electric vehicles (HEVs), grid energy storage, etc.

[0005] At a cut-off voltage higher than about 4.2V, the electrolyte system often deteriorates because the components of the electrolyte, such as solvents, conductive salts and additives, especially film-forming additives that are believed to form a protective layer (often called "solid electrolyte interphase (SEI)") on the surface of the electrode during initial charging, cannot withstand such high voltage. Rather, batteries that can be operated at higher voltages (up to 5.0V) are desired in the art, and thus there is a consistent need in the art to develop electrolytes suitable for high voltage batteries and / or components for such electrolytes. In terms of charge cut-off voltage, such high voltage batteries have a charge cut-off voltage higher than 4.2V, particularly at least 4.35V.

[0006] As electrolyte solvents for lithium secondary batteries, organic carbonates, including acyclic carbonates such as ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, and cyclic carbonates such as ethylene carbonate or propylene carbonate, have been used conventionally. However, these organic carbonates can easily decompose above 4.35 V, and there are also safety concerns about the use of organic carbonates due to their relatively low boiling points and high flammability, which can lead to deterioration of battery performance.

[0007] Therefore, various approaches are being investigated to overcome the limitations of commonly used liquid electrolytes based on organic carbonates, in order to increase the energy density at higher voltages, improve the cycling performance at high temperatures, and reduce the battery swelling, while ensuring high safety.

[0008] As one of various research efforts for such a purpose, a specific solvent mixture for use as a liquid electrolyte in a lithium secondary battery, which contains ethylene carbonate and a certain concentration of a fluorine-containing carboxylic acid ester, was reported in WO 2013 / 033579 (EIDUPONT DE NEMOURS AND COMPANY) to contribute to improving cycling performance at high temperatures, especially in high-voltage cathodes.

[0009] Moreover, there have been several approaches to the same objective, consisting in using certain hydrofluoroethers as essential components of electrolytes for lithium-ion batteries. For example, US Pat. No. 5,916,708 (HOESHST AKTIENGESELLSHAFT) describes hydrofluoroethers of formula (i) and / or (ii): RO-[CH2] m O] n -CF2-CFHX(i) X-CFH-CF2O-[(CH2) m O] n -CF2-CFH-X (ii) (wherein R is a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms; X is a perfluoroalkyl group having 1 to 6 carbon atoms which may also contain fluorine, chlorine or ether oxygen; m is an integer from 2 to 6, and n is an integer from 1 to 8). The present invention discloses certain hydrofluoroethers represented by the formula:

[0010] WO 2015 / 078791 (Solvay Specialty Polymers Italy SpA) discloses that liquid electrolytes comprising certain hydrofluoroethers with a high degree of fluorination, obtained by the process disclosed in WO 2012 / 084745 A (Solvay Specialty Polymers Italy SpA), exhibit advantageous properties in terms of solubility of lithium salts, operating temperature range, ionic conductivity, oxidative stability at high voltages and low flammability.

[0011] As briefly described above, despite efforts in this field, there remains an unmet need for liquid electrolytes for lithium secondary batteries with improved cycling performance at high temperatures, especially with high voltage cathodes. Summary of the Invention

[0012] The present invention relates to a) Formula (I) R 1 -OR 2 -OR 3 (I) (In the formula, R 1 and R 3 each represents a fluorinated linear alkyl group; R 2 represents an optionally fluorinated linear alkylene group; and R 1 , R 2 and R 3 The total number of carbon atoms is 5 to 8, preferably 6. and at least one fluorinated acyclic diether represented by: b) Formula (II) R 4 -C(O)OR 5 (II) (In the formula, R 4 and R 5 Each represents an alkyl group; R 4 and R 5 The total number of carbon atoms in R is 2 to 7; and R 5 At least one hydrogen atom of the formula (I) is replaced by a fluorine atom. and at least one fluorinated acyclic carboxylic acid ester represented by: c) at least one organic carbonate; d) at least one lithium salt; The present invention relates to a liquid electrolyte for a lithium secondary battery, comprising:

[0013] Surprisingly, it has been found by the inventors that the above mentioned technical problems can be solved by using the liquid electrolyte according to the present invention, which is clearly evidenced by the excellent capacity retention and coulombic efficiency. [Brief description of the drawings]

[0014] [Figure 1] The cycle retention (%) of E1 to E2 and CE1 to CE3 at 25° C. is shown. [Diagram 2] The cycle retention (%) of E1 to E2 and CE1 to CE3 at 45° C. is shown. [Diagram 3] 1 shows the storage expansion performance in terms of thickness change (in mm) of E1-E2 and CE1-CE3 at 60° C. for 4 weeks. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] definition Throughout this specification, unless the context requires otherwise, the terms "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 terms "comprise" and "comprises" and variations thereof mean "consisting only of."

[0016] As used herein, the singular forms "a", "an" and "the" include plural embodiments 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.

[0017] The term "~" should be understood to be inclusive.

[0018] The term "aliphatic group" includes organic moieties characterized by straight or branched chains, typically having from 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.

[0019] In the present invention, the term "cut-off voltage" is intended to mean a predetermined lower voltage limit below which the discharge is considered complete. The cut-off voltage is usually selected so that the maximum usable capacity of the battery is achieved. The cut-off voltage varies from battery to battery and is highly dependent on the type of battery, e.g., type of cathode or anode.

[0020] 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.

[0021] Ratios, concentrations, amounts, and other numerical data may be presented in a 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 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 to include not only the explicitly recited limits of about 120°C to about 150°C, but also subranges such as 125°C to 145°C, 130°C to 150°C, etc., and individual amounts such as fractions within the stated range, e.g., 122.2°C, 140.6°C, and 141.3°C.

[0022] Unless otherwise specified, in the context of the present invention, the amount of a component in a composition is indicated as the ratio between the volume of the component multiplied by 100 and the total volume of the composition, i.e., % by volume (vol%), or the ratio between the weight of the component multiplied by 100 and the total weight of the composition, i.e., % by weight (wt%). 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.

[0023] The present invention relates to a) Formula (I) R 1 -OR 2 -OR 3 (I) (In the formula, R 1 and R 3 each represents a fluorinated linear alkyl group; R 2 represents an optionally fluorinated linear alkylene group; and R 1 , R 2 and R 3 The total number of carbon atoms is 5 to 8, preferably 6. and at least one fluorinated acyclic diether represented by: b) Formula (II) R 4 -C(O)OR 5 (II) (In the formula, R 4 and R 5 Each represents an alkyl group; R 4 and R 5 The total number of carbon atoms in R is 2 to 7; and R 5 At least one hydrogen atom of the formula (I) is replaced by a fluorine atom. and at least one fluorinated acyclic carboxylic acid ester represented by: c) at least one organic carbonate; d) at least one lithium salt; The present invention relates to a liquid electrolyte for a lithium secondary battery, comprising:

[0024] In one embodiment, R 4 and R 5 does not contain any -CH2F- or -CHF- groups.

[0025] In one embodiment, R in formula (II) 4 The number of carbon atoms in R in formula (II) is 1, 3, 4 or 5. 4 The number of carbon atoms is 1.

[0026] In the present invention, the term "alkyl" is intended to mean 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.

[0027] 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 more hydrogen atoms may be replaced by fluorine.

[0028] 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.

[0029] In one embodiment, the boiling point of a) the fluorinated acyclic diether is at least 80°C, preferably 80°C to 160°C, more preferably 120°C to 160°C.

[0030] In one embodiment, a) the fluorinated acyclic diether is in an amount of 0.05 to 45 weight percent (wt %), preferably 0.5 to 40 wt %, based on the total weight of the liquid electrolyte.

[0031] In another embodiment, a) the fluorinated acyclic diether is in an amount of 10 to 45% by weight, preferably 20 to 40% by weight, based on the total weight of the liquid electrolyte.

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

[0033] In a preferred embodiment, a) the fluorinated acyclic diether contains 6 carbon atoms.

[0034] In a more preferred embodiment, a) the fluorinated acyclic diether is CHF2CF2-O-CH2CH2-O-CF2CF2H.

[0035] Non-limiting examples of suitable a) fluorinated acyclic diethers according to the present invention include, inter alia, CF3CH2-O-CF2CHF-O-CF3, CHF2CH2-O-CF2CF2-O-CF3, CF3CF2-O-CHFCHF-O-CHF2, CHF2CF2-O-CHFCHF-O-CF3, CF3CHF-O-CHFCF2-O-CHF2, CF3CHF-O-CF2CHF-O-CHF2, CH3CF2-O-CF2-O-CF2CF3, CFH2CHF-O-CF2-O-CF2CF3, CF3CF2-O-CHF-O-CHFCHF2, CF3CF2-O-CHF-O-CHFCHF2, CF3CH2-O-CF2CF2-O-CF3, CHF2CHF-O-CF2CF2-O-CF3, CH2FCF2-O-CF2CF2-O-CF3, CF3CF2-O-CHFCHF-O-CF3, CF3CF2-O-CF2CH2-O-CF3, CF3CF2-O-CH2CF2-O-CF3, CF3CF2-O-CF2CFH-O-CHF2, CF3CHF-O-CHFCF2-O-CF3, CF3CHF-O-CF2CHF-O-CF3, CHF2CF2-O-CF2CHF-O-CF3, CHF2CF2-O-CHFCF2-O-CF3, CHF2CF2-O-CF2CF2-O-CHF2, CF3CHF-O-CF2CF2-O-CHF2, CF3CF2-O-CF2-O-CHFCF3, CF2HCF2-O-CF2-O-CF2CF3, CF3CHF-O-CF2-O-CF2CF3, CF3CF2-O-CHF-O-CF2CF3, CF3CF2-O-CF2-O-CF2CHF2, CF2HCF2-O-CF2CH2-O-CF2CF2H, CF3CF2-O-CH2CH2-O-CF2CF3, 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-CF2CF2-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.

[0036] In another embodiment, a) the fluorinated acyclic diether contains 7 carbon atoms.

[0037] In another embodiment, a) the fluorinated acyclic diether contains 8 carbon atoms.

[0038] In one embodiment, the liquid electrolyte according to the present invention does not include non-fluorinated ethers or fluorinated monoethers.

[0039] In the present invention, the term "non-fluorinated ether" is intended to mean an ether compound in which no fluorine atoms are present.

[0040] In the present invention, the term "fluorinated monoether" is intended to mean a monoether compound in which at least one hydrogen atom is replaced by fluorine. One, two, three or more hydrogen atoms may be replaced by fluorine.

[0041] Non-limiting examples of suitable fluorinated acyclic carboxylic acid esters according to the present invention include, inter alia, CH3-C(O)O-CH2CF2H, CF3-C(O)O-CH2CF3, CH3-C(O)O-CH2CF3, CF3-C(O)O-CH2CF2CF2H, CH3-C(O)O-CH2CH2CF2H, CH3-C(O)O-CH2CF2CF2H, CH3CH2-C(O)O -CH2CH2CF2H, CF2H-C(O)O-CH2CF2H, CH3CH2-C(O)O-CH2CF2H, CH3-C(O)O-CH2CH2CH2CF2CF3, CH3-C(O)O-CH2CF2H, CH3-C(O)O-CH2CF3, CH3CH2-C(O)O-CH2CF2H, CH3CH2-C(O)O-CH2CF3 and mixtures thereof.

[0042] In a preferred embodiment, b) the fluorinated acyclic carboxylic acid ester comprises CH3-C(O)O-CH2CF2H, CH3-C(O)O-CH2CH2CF2H, CH3CH2-C(O)O-CH2CH2CF2H, CH3-C(O)O-CH2CF3, CH3CH2-C(O)O-CH2CF2H, CH3CH2-C(O)O-CH2CF3, CH3CH2-C(O)O-CH2CF2H, CH3CH2-C(O)O-CH2CF3, CH3CH2-C(O)O-CH2CF2H or a mixture thereof.

[0043] In a more preferred embodiment, b) the fluorinated acyclic carboxylic acid ester is CH3-C(O)O-CH2CF2H (2,2-difluoroethyl acetate).

[0044] In one embodiment, the fluorinated acyclic carboxylic acid ester b) is present in an amount of 10 to 50% by weight, preferably 20 to 45% by weight, based on the total weight of the liquid electrolyte.

[0045] The liquid electrolyte according to the present invention does not include fluorinated cyclic carboxylic acid esters, such as fluorinated lactones containing a 1-oxacycloalkan-2-one structure.

[0046] c) Non-limiting examples of organic carbonates according to the invention include, inter alia, 4-fluoroethylene carbonate, 4,5-difluoro-1,3-dioxolane-2-one, 4,5-difluoro-4-methyl-1,3-dioxolane-2-one, 4,5-difluoro-4,5-dimethyl-1,3-dioxolane-2-one, 4,4-difluoro-1,3-dioxolane-2-one, 4,4,5-trifluoro-1,3-dioxolane-2-one, 4-fluoromethyl-1,3-dioxolane-2-one, tetrafluoroethylene carbonate, 4 -(2,2-difluoroethoxy)ethylene carbonate, 4-(2,2,2-trifluoroethoxy)ethylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, trimethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, dimethylvinylene carbonate, ethyl propyl carbonate, cyclohexene carbonate, bisphenol A, B and F carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and mixtures thereof.

[0047] In one embodiment, the total amount of c) at least one organic carbonate is 10 to 80% by weight, preferably 15 to 60% by weight, based on the total weight of the liquid electrolyte.

[0048] In certain embodiments, c) the organic carbonate comprises a fluorinated cyclic carbonate in an amount of 1 to 15 wt %, preferably 2 to 12 wt %, and more preferably 4 to 10 wt %, based on the total weight of the liquid electrolyte.

[0049] In one embodiment, c) the organic carbonate is represented by formula (III): R 6 -OC(O)OR 7 (III) (In the formula, R 6 and R 7 Each represents an alkyl group: R 6 and R 7 The total number of carbon atoms in R is 2 to 7; and R 6 and / or R 7At least one hydrogen atom of the formula (I) is replaced by a fluorine atom. The present invention includes fluorinated acyclic carbonates represented by the formula:

[0050] In one embodiment, R 6 and R 7 does not contain any -CH2F- or -CHF- groups.

[0051] In certain embodiments, R in formula (III) 6 does not contain fluorine, R 7 contains fluorine.

[0052] In another particular embodiment, R 6 and R 7 independently represents a linear or branched alkyl group having 2 to 7 carbon atoms, where at least two hydrogens are replaced by fluorine (i.e., R 6 At least two hydrogen atoms of R are replaced by fluorine, or 7 At least two hydrogen atoms of R are replaced by fluorine, or 6 At least two hydrogen atoms of R 7 at least two hydrogens are replaced by fluorine.

[0053] Non-limiting examples of suitable fluorinated acyclic carbonates according to the present invention include, inter alia, CH3-OC(O)O-CH2CF2H (methyl 2,2-difluoroethyl carbonate), CH3-OC(O)O-CH2CF3 (methyl 2,2,2-trifluoroethyl carbonate), CH3-OC(O)O-CH2CF2CF2H (methyl 2,2,3,3-tetrafluoropropyl carbonate), CF2HCH2-OC(O)O-CH2CF3 (ethyl 2,2-difluoroethyl carbonate), CF3CH2-OC(O)O-CH2CH3 (ethyl 2,2,2-trifluoroethyl carbonate), CF3CH2-OC Examples of such carbonates include (O)O-CH2CF3 (bis(2,2,2-trifluoroethyl)carbonate), CF2HCH2-OC(O)O-CH2CF2H (bis(2,2-difluoroethyl)carbonate), CH3-OC(O)O-CH2CF2H (methyl 2,2-difluoroethyl carbonate), CF3-OC(O)O-CF3, CFH2-OC(O)O-CH3, CF3CHF-OC(O)O-CF3, CH3CH2-OC(O)O-CHFCH3, CH3CHF-OC(O)O-CHFCH3, CH3CHF-OC(O)O-CH2CF3, CH3CHF-OC(O)O-CH2CH2CH3 and mixtures thereof.

[0054] d) Non-limiting examples of lithium salts according to the invention include, inter alia, 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 (wherein x=0 to 12), LiPF x (R F ) 6-x and LiBF y(R F ) 4-y (In the formula, R F Perfluorinated C1-C 20 represents an alkyl group or a perfluorinated aromatic group, x=0-5, and y=0-3), LiBF2[O2C(CX2) n CO2], LiPF2[O2C(CX2) n CO2]2, LiPF4[O2C(CX2) n CO2] (wherein X is selected from the group consisting of H, F, Cl, C1-C4 alkyl groups and fluorinated alkyl groups, and n=0-4), 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 ) (wherein k=1-10, m=1-10, and n=1-10), LiN(SO2C p F 2p SO2) and LiC(SO2C p F 2p SO2)(SO2C q F 2q+1 ) (wherein p=1-10 and q=1-10) and mixtures thereof.

[0055] In one embodiment, d) the lithium salt is lithium bis(trifluorosulfonyl)imide (LiN(CF3SO2)2; LiTFSI).

[0056] In another embodiment, d) the lithium salt is LiPF6.

[0057] In another embodiment, d) the lithium salt is LiFSI.

[0058] In one embodiment, the molar concentration (M) of the lithium salt in the liquid electrolyte according to the present invention is 1M to 8M, preferably 1M to 4M, and more preferably 1M to 2M.

[0059] Lithium salts according to the present invention do not include lithium salts having a nitrogen atom on a heterocyclic ring such as imidazole, for example lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI).

[0060] 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 a solid electrolyte interface (SEI) layer at the negative electrode surface by pre-reacting the solvent on the electrode surface. For the SEI layer, the main components therefore comprise the electrolyte solvent and the decomposition products of the salt, which may include Li2CO3 (in the case of LiCoO2 as the positive electrode), lithium alkyl carbonate, lithium alkyl oxide and other salt moieties such as LiF for LiPF6-based electrolytes. According to another embodiment, e) the film-forming additive stabilizes the cathode electrolyte interface (CEI) layer at the positive electrode surface by preventing structural changes of the positive electrode, especially under high voltage. Usually, the reduction potential of the film-forming additive is higher than the reduction potential of the solvent when the reaction occurs at 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 at the positive electrode side.

[0061] In one embodiment, e) the film-forming additive according to the present invention is 1,3,2-dioxathiolane-2,2-dioxide, 1,3,2-dioxathiolane-4-ethynyl-2,2-dioxide, 1,3,2-dioxathiolane-4-ethenyl-2,2-dioxide, 1,3,2-dioxathiolane-4,5-diethenyl-2,2-dioxide, 1,3,2-dioxathiolane-4-methyl-2,2-dioxide, 1,3,2-dioxathiolane-4,5-dimethyl-2,2-dioxide, 1,3,2-dioxathiane-2,2-dioxide, 1,3,2 -Dioxathiane-4-ethynyl-2,2-dioxide, 1,3,2-dioxathiane-5-ethynyl-2,2-dioxide, 1,3,2-dioxathiane-4-ethenyl-2,2-dioxide, 1,3,2-dioxathiane-5-ethenyl-2,2-dioxide, 1,3,2-dioxathiane-4,5-diethenyl-2,2-dioxide, 1,3,2-dioxathiane-4,6-diethenyl-2,2-dioxide, 1,3,2-dioxathiane-4,5,6-triethenyl-2,2-dioxide, 1,3,2-dioxathiane-4-methyl-2,2- Dioxide, 1,3,2-dioxathiane-5-methyl-2,2-dioxide, 1,3,2-dioxathiane-4,5-dimethyl-2,2-dioxide, dioxathiane-4,6-dimethyl-2,2-dioxide, dioxathiane-4,5,6-trimethyl-2,2-dioxide; 1,3-propane sultone, 3-fluoro-1,3-propane sultone, 4-fluoro-1,3-propane sultone, 5-fluoro-1,3-propane sultone, 1,4-butane sultone, 3-fluoro-1,4-butane sultone, 4-fluoro-1,4-butane sultone , 5-fluoro-1,4-butane sultone, 6-fluoro-1,4-butane sultone, preferably sulfur compounds including 1,3,2-dioxathiolane-2,2-dioxide, 1,3,2-dioxathiane-2,2-dioxide, oxathiolane-2,2-dioxide (1,3-propane sultone), 1,3,2-dioxathiolane-2-oxide (ethylene sulfite) and prop-1-ene-1,3-sultone, dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethyl methyl sulfone and isopropyl methyl sulfone;Nitrile derivatives including succinonitrile, adiponitrile and glutaronitrile; lithium nitrate (LiNO3); lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalato)borate (LiB(C2O4)2; LiBOB), lithium fluoromalonato(difluoro)borate (LiB(O2CCHFCO2)2; LiFMDFB), lithium bis(malonato)borate [LiB(O2CCH2CO2)2], lithium bis(difluoromalonato)borate [LiB(O2CCF2 boron derivative salts including lithium (malonato oxalato)borate [LiB(C2O4)(O2CCH2CO2)], lithium (difluoromalonato oxalato)borate [LiB(C2O4)(O2CCF2CO2)]; lithium tris(oxalato)phosphate [LiP(C2O4)3], lithium tris(difluoromalonato)phosphate [LiP(O2CCF2CO2)3], lithium difluorophosphate (LiPO2F2), vinyl acetate, biphenylbenzene, isopropylbenzene, heptane, xafluorobenzene, tris(trimethylsilyl)phosphate, triphenylphosphine, ethyl diphenylphosphinite, triethyl phosphite, tris(2,2,2-trifluoroethyl)phosphite, maleic anhydride, vinylene carbonate, vinyl ethylene carbonate, cesium bis(trifluorosulfonyl)imide (CsTFSI), cesium hexafluorophosphate (CsPF6), 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-1CF3), lithium hexafluorophosphate (LiPF6), silver nitrate (AgNO3), silver hexafluorophosphate (AgPF6), tris(trimethylsilyl)phosphine (TMSP), 1,6-divinylperfluorohexane and mixtures thereof;

[0062] In a preferred embodiment, e) the film forming additive is selected from the group consisting of sulfur compounds including 1,3,2-dioxathiolane-2,2-dioxide, 1,3,2-dioxathiane-2,2-dioxide, 1,3-propane sultone, ethylene sulfite and propa-1-salt-1,3-sultone; sulfone derivatives including dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethyl methyl sulfone and isopropyl methyl sulfone; nitrile derivatives including succinonitrile, adiponitrile and glutaronitrile; and lithium nitrate (LiNO3); lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalato)borate (LiB(CO)2; LiBOB), lithium fluoromalonato(difluoro)borate (LiB(OCHFCO)2; LiFMDFB), lithium bis(malonato)borate [LiB(OCCHCO)2], lithium bis(difluoro ... Boron derivative salts including lithium (malonato) phosphate [LiB(O2CCF2CO2)2], lithium (malonato oxalato)borate [LiB(C2O4)(O2CCH2CO2)], lithium (difluoromalonato oxalato)borate [LiB(C2O4)(O2CCF2CO2)]; lithium tris(oxalato)phosphate [LiP(C2O4)3], lithium tris(difluoromalonato)phosphate [LiP(O2CCF2CO2)3], lithium difluorophosphate ( LiPO2F2), vinyl acetate, biphenylbenzene, isopropylbenzene, hexafluorobenzene, tris(trimethylsilyl)phosphate, triphenylphosphine, ethyldiphenylphosphinite, triethylphosphite, tris(2,2,2-trifluoroethyl)phosphite, maleic anhydride, cesium bis(trifluorosulfonyl)imide (CsTFSI), cesium fluoride (CsF), and mixtures thereof.

[0063] In a more preferred embodiment, e) the film-forming additive according to the present invention is LiBOB.

[0064] In another more preferred embodiment, e) the film forming additive according to the present invention is maleic anhydride.

[0065] In another more preferred embodiment, e) the film forming additive according to the present invention is a mixture of maleic anhydride and LiBOB.

[0066] In another embodiment, e) the film-forming additive according to the present invention is an ionic liquid.

[0067] 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 temperatures below 100° C. at atmospheric pressure. Whereas ordinary liquids such as water are composed primarily of electrically neutral molecules, ionic liquids are composed primarily of ions and short-lived ion pairs. As used herein, the term "ionic liquid" refers to compounds that do not contain solvent.

[0068] 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 nonmetallic atom, such as O, N, S, or P.

[0069] 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:

[0070] The cations may be selected, independently of one another, from metal cations and organic cations. The cations may be monovalent or polyvalent cations.

[0071] Metal cations may preferably include alkali metal cations, alkaline earth metal cations and cations of d-block elements.

[0072] 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 may in particular be a cation formed by an atom selected from the group consisting of N, P, O and S, more preferably N and P, and three or four hydrocarbon chains.

[0073] 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] selected from the group consisting of: - acyclic onium cations, in particular 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, each R' independently represents a hydrogen atom or a C1-C8 alkyl group; L+ and R' may be a single or double bond. You can choose from.

[0074] In the above formula, each "R" symbol represents, independently of one another, a hydrogen atom or an organic group. Preferably, each "R" symbol in the above formula represents, independently of one another, a hydrogen atom or a saturated or unsaturated linear, branched or cyclic C1-C alkyl group optionally substituted one or more times with a halogen atom, an amino group, an imino group, an amide group, an ether group, an ester group, a hydroxyl group, a carboxyl group, a carbamoyl group, a cyano group, a sulfone group or a sulfite group. 18 It may represent a hydrocarbon group.

[0075] Cation Q l+ (n / l) may more particularly be selected from ammonium, phosphonium, pyridinium, pyrrolidinium, pyrazolinium, imidazolium, arsenium, quaternary phosphonium and quaternary ammonium cations.

[0076] The quaternary phosphonium or ammonium cations may more preferably be selected from tetraalkylammonium or tetraalkylphosphonium cations, trialkylbenzylammonium or trialkylbenzylphosphonium cations or tetraarylammonium or tetraarylphosphonium cations, whose alkyl groups, either the same or different, represent a linear or branched alkyl chain having from 4 to 12 carbon atoms, preferably from 4 to 6 carbon atoms, and whose aryl groups, either the same or different, represent a phenyl group or a naphthyl group.

[0077] In certain embodiments, Q l+ (n / l) represents a quaternary phosphonium or quaternary ammonium cation.

[0078] In a preferred embodiment, Q l+(n / l) represents a quaternary phosphonium cation. Non-limiting examples of quaternary phosphonium cations include trihexyl(tetradecyl)phosphonium and tetraalkylphosphonium cations, in particular the tetrabutylphosphonium (PBu4) cation.

[0079] 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.

[0080] 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(C8-C 10 (a) a mixture of alkyl (quaternary ammonium compounds) and (b) a mixture of quaternary ammonium compounds.

[0081] In one embodiment, Q l+ (n / l) represents a piperidinium cation, in particular N-butyl-N-methylpiperidinium, N-propyl-N-methylpiperidinium.

[0082] In another embodiment, Q l+ (n / l) represents a pyridinium cation, in particular N-methylpyridinium.

[0083] In a more preferred embodiment, Q l+ (n / l) represents a pyrrolidinium cation. Among the specific pyrrolidinium cations, C 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).

[0084] Non-limiting examples of anions of ionic liquids include iodide, bromide, chloride, hydrogen sulfate, dicyanamide, acetate, diethyl phosphate, methyl phosphate, fluorinated anions such as hexafluorophosphate (PF6 - ) and tetrafluoroborate (BF4 - ) and the following formula: [ka] Contains oxalatoborate.

[0085] 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 an anion of the following general formula: (E a -SO2)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, and - R represents a substituent. The anion may be selected from those having the following formula:

[0086] Preferably, E a may represent F or CF3.

[0087] According to a first embodiment, R represents a hydrogen atom.

[0088] According to a second embodiment, R preferably represents a linear or branched, cyclic or acyclic hydrocarbon-based group having 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, a nitrile function or an alkyl group optionally substituted one or more times with a halogen atom. Furthermore, R may represent a nitrile group -CN.

[0089] According to a third embodiment, R represents a sulfinate group. In particular, R represents the group -SO2-E a (E a is as defined above). In this case, the fluorinated anion is 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.

[0090] Furthermore, R may represent the group -SO2-R', where R' preferably represents a linear or branched, cyclic or acyclic, hydrocarbon-based group having 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, a nitrile function or 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 the group -SO2-N-R', where R' is as defined above or otherwise R' represents a sulfonate function -SO3.

[0091] 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.

[0092] 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.

[0093] The organic anion that can be used in the present invention is advantageously CF3SO2N - SO2CF3 (bis(trifluoromethanesulfonyl)imide anion, commonly referred to as TFSI), FSO2N - SO2F (bis(fluorosulfonyl)imide anion, commonly referred to as FSI), CF3SO2N - SO2F and CF3SO2N - SO2N - It may be selected from the group consisting of SO2CF3.

[0094] In a preferred embodiment, the ionic liquid is - One or more C1~C30 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:

[0095] C1~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.

[0096] In a 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).

[0097] In the present invention, the total amount of e) the film-forming additives may be 0 to 10% by weight, preferably 0 to 8% by weight, and more preferably 0 to 5% by weight, based on the total weight of the liquid electrolyte.

[0098] e) The total amount of the film-forming additives, when contained in the liquid electrolyte of the present invention, is 0.05 to 5.0% by weight, preferably 0.05 to 3.0% by weight, based on the total weight of the liquid electrolyte.

[0099] In a more preferred embodiment, the total amount of e) film-forming additives comprises at least 1.0% by weight of the electrolyte composition.

[0100] In one embodiment, the liquid electrolyte for the lithium secondary battery according to the present invention comprises: a) a compound represented by formula (I) in an amount of 0.05 to 45% by weight based on the total weight of the liquid electrolyte; R 1 -OR 2 -OR 3 (I) (In the formula, R 1 and R 3 each represents a fluorinated linear alkyl group; R 2 represents an optionally fluorinated linear alkyl group; and R 1 , R 2 and R 3 The total number of carbon atoms is 5 to 8, preferably 6. and at least one fluorinated acyclic diether represented by: b) Formula (II) R 4 -C(O)OR 5 (II) (In the formula, R 4 and R 5 Each represents an alkyl group; R 4 and R 5 The total number of carbon atoms in R is 2 to 7; and R 5 At least one hydrogen atom of R is replaced by fluorine. 4 and R 5 does not contain any CH2F- or -CHF- groups) and at least one fluorinated acyclic carboxylic acid ester represented by: c) at least one organic carbonate in an amount of 10 to 80% by weight based on the total weight of the liquid electrolyte; d) at least one lithium salt; Includes.

[0101] In a particular embodiment, the liquid electrolyte for the lithium secondary battery according to the present invention comprises: - CF2HCF2-O-CH2CH2-O-CF2CF2H as fluorinated acyclic diethers; - CH3-C(O)O-CH2CF2H as fluorinated acyclic carboxylic acid esters; - a mixture of PC and FEC as organic carbonate; - 1M LiPF6 as lithium salt; - With LIBOB and maleic anhydride as film forming additives Includes.

[0102] The present invention relates to - with the anode; - with the cathode; - with separator; a liquid electrolyte according to the invention; Also provided is a lithium secondary battery comprising:

[0103] 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.

[0104] 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.

[0105] In the present invention, the type of "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 comprises, and is preferably composed of, at least one metal selected from the group consisting of aluminum (Al), nickel (Ni), titanium (Ti) and alloys thereof, preferably Al. When the electrode of the present invention is an anode, the current collector typically comprises, and is preferably composed of, at least one metal selected from the group consisting of lithium (Li), sodium (Na), zinc (Zn), magnesium (Mg), copper (Cu) and alloys thereof, preferably Cu.

[0106] In the present invention, the term "areal capacity" of an electrode, i.e., an anode and a cathode, is intended to particularly mean the areal-normalized specific capacity of the electrode.

[0107] The selection and preparation of the electrodes, the components contained therein, and other components that may be present in the battery, if any, are known in the art and can thus be appropriately configured according to the purpose.

[0108] For example, the electrodes of a battery such as a cathode and an anode can be formed from an electrode-forming composition containing an electrode active material, a binder, a solvent, and optionally one or more additives.

[0109] 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. The type of electroactive material will depend on whether it is used to form a cathode or an anode. The electroactive material can thus be selected from a cathode electroactive material and an anode electroactive material.

[0110] When forming a cathode for a lithium-ion battery, the cathode electroactive material is not particularly limited. It can include a composite metal chalcogenide of the formula LiMQ2 (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 LiMO2 (wherein M is the same as defined above). Lithium-based composite metal oxides such as LiCoO2 can include or consist of a layered structure. Composite metal chalcogenides such as lithium-based composite metal oxides can include or consist of a nanostructure. Preferred examples thereof can include LiCoO2, LiNiO2, LiNi x Co 1-x O2 (0 < x < 1) and spinel-structured LiMn2O4. Another preferred example thereof can include a compound of the formula LiNi xMn y Co z Lithium-nickel-manganese-cobalt-based metal oxides such as LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.5 Mn 0.2 Co 0.3 O2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, preferably LiNi 0.8 Mn 0.1 Co 0.1 O2 and formula LiNi x Co y Al z Lithium-nickel-cobalt-aluminium oxides such as LiNiO2 (x+y+z=1, called NCAs) 0.8 Co 0.15 Al 0.05 O2 may be mentioned. Nevertheless, the formula: - Li x Mn 1-y M' y A2(1) - Li x Mn 1-y M' y O 2-z Z z (2) - Li x MnO 4-z A z (3) - Li x Mn 2-y M' y A4(4) - Li x M 1-y M'' y A2(5) - Li x MO 2-z A z (6) - Li x Ni 1-y Co y O 2-z Az (7) - Li x Ni 1-y-z Co y M'' z A a (8) - Li x Ni 1-y-z Co y M'' z O 2-a Z a (9) - Li x Ni 1-y-z Mn y M' z A a (10) - Li x Ni 1-y-z Mn y M' z O 2-a Z a (11) (In the formula, - 0.95≦x≦1.1, 0≦y≦0.5, 0≦z≦0.5, and 0≦a≦2; - M is Ni or Co, M' is one or more elements selected from the group consisting of Al, Ni, Co, Cr, Fe, Mg, Sr, V, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th and Pa, M'' is one or more elements selected from the group consisting of Al, Cr, Mn, Fe, Mg, Sr, V, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th and Pa, A is selected from the group consisting of O, F, S and P, and Z is selected from the group consisting of F, S and P). A broader range of chalcogenides may be considered, such as those represented by:

[0111] Another preferred example is a lithium-nickel-manganese metal oxide (also called LNMO), such as LiNi 0.5 Mn 0.5 O2 and LiNi 0.5 Mn 1.5 O4 may be mentioned.

[0112] Alternatively, when further forming a cathode for a lithium ion battery, the cathode electroactive material may be of the formula M1M2(JO4): f E 1-f The electroactive materials may include lithiated or partially lithiated transition metal oxyanion based electroactive materials of the formula M1M2(JO4) as defined above, where M1 is lithium which may be partially replaced by another alkali metal representing 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 replaced by one or more additional metals with oxidation levels of +1 to +5 and inclusive which represent less than 35% of the M2 metal, and JO4 is any oxyanion, where J is either P, S, V, Si, Nb, Mo or combinations thereof, E is a fluoride, hydroxide or chloride anion, and f is the mole fraction of the JO4 oxyanion, generally comprised between 0.75 and 1. f E 1-f The electroactive material is preferably phosphate-based and may have an ordered or modified olivine structure. More preferably, the cathode electroactive material is of the formula Li 3-x M' y M'' 2-y (JO4)3, where 0≦x≦3 and 0≦y≦2, M′ and M″ are the same or different metals, at least one of which is a transition metal, and JO4 is preferably PO4 which may be partially substituted with another oxyanion, where J is any of S, V, Si, Nb, Mo or combinations thereof. Even more preferably, the cathode electroactive material has the formula Li(Fe x Mn 1-x LiFePO4 is a phosphate-based electroactive material having the formula: LiFePO4, where 0≦x≦1, and x is preferably 1 (i.e., lithium iron phosphate of the formula LiFePO4).

[0113] In a preferred embodiment, the cathode electroactive material is LiMQ2 (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 O2 (0 < x < 1); spinel structured LiMn2O4; lithium-nickel-manganese-cobalt based metal oxide (NMC), such as LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, lithium-nickel-cobalt-aluminum based metal oxide (NCA), such as LiNi 0.8 Co 0.15 Al 0.05 O2 and is selected from the group consisting of LiFePO4.

[0114] In one embodiment, the cathode is a lithium-nickel-manganese-cobalt based metal oxide of the formula LiNi x Mn y Co z O2 (where x + y + z = 1), a lithium-nickel-cobalt-aluminum based metal oxide of the formula LiNi x Co y Al z O2 (where x + y + z = 1), a lithium-cobalt based metal oxide or a lithium-nickel-manganese based metal oxide (LNMO) as the cathode electroactive material.

[0115] In a preferred embodiment, the cathode is LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.5 Mn 0.5 O2, LiNi 0.5 Mn 1.5 O4 and LiCoO2 as the cathode electroactive material.

[0116] When forming an anode for a lithium ion battery, the anode electroactive material is not particularly limited, and may be any of the following: - graphitic carbon capable of intercalating lithium, typically present in the form of lithium-hosting powder, flakes, fibers or spheres (e.g. mesocarbon microbeads) and the like; - Lithium metal; - lithium alloy compositions such as those described in particular in US Pat. No. 6,203,944 (3M Innovative Properties Co.) and WO 2000 / 03444 (Minnesota Mining & Manufacturing Co.); - Generally, the formula Li4Ti5O 12 Lithium titanates represented by the formula: (These compounds have mobile ions, i.e., Li + (generally considered to be a "zero-strain" intercalation material that has a low level of physical expansion when it absorbs stress); - Lithium-silicon alloys, commonly known as lithium silicides, with high Li / Si ratios, especially those of the formula Li 4.4 Si lithium silicide; - Formula Li 4.4 A lithium-germanium alloy containing a crystalline phase of Ge; - with silicon; - Silicon-carbon composites and may include.

[0117] In one embodiment, the anode comprises silicon or a silicon-carbon composite as the anode electroactive material.

[0118] The battery of the present invention can be a lithium secondary battery, such as a lithium ion battery, a lithium sulfur battery and a lithium air battery, and a sodium secondary battery, such as a sodium ion battery and a sodium sulfur battery, in particular a lithium ion battery. In the present invention, the battery with a high charging cut-off voltage is preferably a secondary battery, in particular a secondary lithium ion battery.

[0119] The term "separator" is intended herein to mean a single or multi-layer polymeric, nonwoven cellulosic or ceramic material / film that electrically and physically separates electrodes of opposite polarity in an electrochemical device and is permeable to the flow of ions therebetween.

[0120] In the present invention, the separator can be any porous substrate commonly used for separators in electrochemical devices.

[0121] 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, optionally coated with inorganic nanoparticles.

[0122] Non-limiting examples of inorganic nanoparticles include SiO2, TiO2, Al2O3, and ZrO2.

[0123] In one particular embodiment, the separator is a polyester film coated with SiO2.

[0124] In another specific embodiment, the separator is a polyester film coated with Al2O3.

[0125] In another particular embodiment, the separator is a porous polymeric material coated with polyvinylidene difluoride (PVDF).

[0126] 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 a term may be unclear, this statement shall control.

[0127] The present invention will now be described in 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

[0128] raw materials - BP160: A fluorinated diether of C6F8H6O2 (CF2HCF2-O-CH2CH2-O-CF2CF2H) synthesized in-house at Solvay, with a boiling point of approximately 160°C. - BP120: C6F with a boiling point of about 120°C, synthesized in-house at Solvay 10 Fluorinated diethers as mixtures with H4O2 - FC4: C4 fluorinated diether of CF3-O-CH2CH2-O-CF3, commercially available from Appolo Scientific - TTE: a fluorinated monoether as a single compound, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, having a boiling point of about 93°C, commercially available from SynQuest - DFEA: Fluorinated acyclic carboxylic acid ester of CH3-C(O)O-CH2CF2H synthesized in-house at Solvay - PC: Propylene carbonate commercially available from Enchem - FEC: Fluoroethylene carbonate available from Enchem - DMC: Dimethyl carbonate available from Enchem - LiBOB: Lithium bis(oxalato)borate commercially available from Enchem - MA: Maleic anhydride available from Enchem - TMSPa: Tris(trimethylsilyl)phosphate, commercially available from Aldrich - Li salt: Lithium hexafluorophosphate (LiPF6) available from Enchem - Pouch cell: NCM811 / AG (artificial graphite)-575166 available from Lifun

[0129] A / Liquid electrolyte formulation: Liquid electrolytes were prepared for the inventive examples E1-E2 and comparative examples CE1-CE3, the components of which are summarized in Table 1 below.

[0130] [Table 1]

[0131] When preparing the liquid electrolyte of E1, DFEA and BP160 were mixed first, then FEC and PC were added under stirring. After that, 0.85 wt% LiBOB was mixed using a magnetic stirrer in a glove box until the solution became clear. Then, 1M LiPF6 was added. After the solution became clear, 0.5 wt% MA was finally added to the solution.

[0132] The liquid electrolyte for E2 was prepared similarly to E1, except that BP120 was used instead of BP160.

[0133] The liquid electrolyte for CE1 was prepared similarly to E1, except that FC4 was used instead of BP160.

[0134] When preparing the liquid electrolyte of CE2, FEC and PC were added to DFEA, and 0.85 wt% LiBOB was mixed together under stirring until the solution became clear. Then, 1M LiPF6 was dissolved in the solution. After the solution became clear, 0.5 wt% MA was then added to the solution.

[0135] The liquid electrolyte of CE3 was prepared by first mixing DMC and TTE, followed by FEC under stirring. 1M LiPF6 was dissolved in the solution until the solution became clear. Then, 2 wt% TMSPa was added to the solution.

[0136] B / Preparation of pouch cells Prior to use, the pouch cell was cut below the heat seal and dried under vacuum at 55°C for 96 hours to remove any excess moisture. After drying, the cell was filled with 3.077 ml of electrolyte solution and sealed using a vacuum sealer at -95 kPa pressure. The cell was then kept at 25°C for 24 hours. SEI formation was then carried out by connecting the cell to a Maccor 4000 series cycler and charging the cell at C / 10 for 3 hours. The cell was then kept at 25°C and 60°C for 24 hours consecutively. The cell was then degassed by cutting open the pouch and resealed using a vacuum sealer. The cell was cycled from 3.0 to 4.35 V at 25°C. The cell was charged and discharged at C / 2 rate for 3 cycles.

[0137] C / Cell evaluation procedure - Cycling at 25°C: The cells were maintained at 25±0.1°C and cycled at 1C charge / 2C discharge from 3.0 to 4.2V. - Cycling at 45°C: The cells were maintained at 45±0.1°C and cycled at 1C charge / 2C discharge from 3.0 to 4.2V. - Storage test: The cells were charged to 4.2V and transferred to a thermal chamber for storage test. The cell thickness was measured once a week for 4 weeks, and the capacity retention, recovery and DC-IR change were measured in the last 4 weeks.

[0138] D / Result The cycle retention rates of liquid electrolytes E1-E2 and CE1-CE3 at room temperature (25° C.) and high temperature (45° C.) are shown in Table 2 below and in Figures 1 and 2. The cycling of CE1 is still in progress.

[0139] [Table 2]

[0140] The liquid electrolytes E1-E2 according to the present invention show excellent cycling performance, much higher than that of CE2 and CE3, at both 25° C. and 45° C. In particular, CE1, i.e., a liquid electrolyte containing a C4 fluorinated diether of CF3-O-CH2CH2-O-CF3 (C4F6H4O2) instead of BP160 (or BP120), showed poorer cycle retention (90% at 25° C.) than E1. In addition, the cycle retention (90% at 45° C.) of E1 was 370 cycles, while the cycle retention (90% at 45° C.) of CE1 was 90 cycles.

[0141] Furthermore, the storage expansion performance (thickness difference between initial and after 4 weeks of storage at 60°C) of E1-E2 and CE1-CE3 after storage at 60°C is shown in Table 3 below in terms of thickness increase rate (in %) and thickness change (in mm) in Figure 3.

[0142] [Table 3]

[0143] It was clearly demonstrated that the liquid electrolytes E1-E2 according to the present invention provide higher capacity retention and less swelling than the liquid electrolytes CE1-CE3.

Claims

1. a) a compound represented by formula (I) R １ -O-R ２ -O-R ３ (I) (In the formula, R １ and R ３ each represents a fluorinated linear alkyl group; R ２ represents an optionally fluorinated linear alkylene group; and R １ , R ２ and R ３ The total number of carbon atoms in is 5 to 8, preferably 6. and at least one fluorinated acyclic diether represented by: b) Formula (II) ( ４ _________ ５ (=) (In the formula, R ４ and R ５ each represents an alkyl group; R ４ and R ５ The total number of carbon atoms in R is 2 to 7; and R ５ At least one hydrogen atom of the formula (I) is replaced by fluorine. and at least one fluorinated acyclic carboxylic acid ester represented by: c) at least one organic carbonate; d) at least one lithium salt; 1. A liquid electrolyte for a lithium secondary battery comprising:

2. R ４ and R ５ is CH ２ 2. The liquid electrolyte for a lithium secondary battery according to claim 1, which contains no F- or -CHF- groups.

3. 2. The liquid electrolyte for lithium secondary batteries according to claim 1, wherein the fluorinated acyclic diether is in an amount of 0.05 to 45.0 weight percent (wt %), preferably 0.5 to 40.0 wt %, based on the total weight of the liquid electrolyte.

4. 2. The liquid electrolyte for a lithium secondary battery according to claim 1, wherein a) the molar ratio F / H in the fluorinated acyclic diether is from 1.3 to 13.0, preferably from 2.5 to 6.

0.

5. a) The fluorinated acyclic diether is 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-CF ３ , 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-CF ２ CHF ２ 、CF ２ HCF ２ -O-CF ２ CH ２ -O-CF ２ CF ２ H、CF ２ HCF ２ -O-CH 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 ２ HCF ２ -O-CHFCHF-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 , C.F. ３ CF ２ -O-CHFCHF-O-CF ２ CF ３ , C.F. ３ CF ２ -O-CHFCHF-O-CF ２ CF ３ and mixtures thereof, preferably CF ２ HCF ２ -O-CH ２ CH ２ -O-CF ２ CF ２ 2. The liquid electrolyte for a lithium secondary battery according to claim 1, wherein the electrolyte is H.

6. b) the fluorinated acyclic carboxylic acid ester is CH ３ -C(O)O-CH ２ CF ２ H, C.H. ３ -C(O)O-CH ２ CH ２ CF ２ H, C.H. ３ CH ２ -C(O)O-CH ２ CH ２ CF ２ H, C.H. ３ -C(O)O-CH ２ CF ３ , C.H. ３ CH ２ -C(O)O-CH ２ CF ２ H, C.H. ３ CH ２ -C(O)O-CH ２ CF ３ , C.H. ３ CH ２ -C(O)O-CH ２ CF ２ 2. The liquid electrolyte for a lithium secondary battery according to claim 1, comprising: H or a mixture thereof.

7. c) The organic carbonate is 4-fluoroethylene carbonate, 4,5-difluoro-1,3-dioxolane-2-one, 4,5-difluoro-4-methyl-1,3-dioxolane-2-one, 4,5-difluoro-4,5-dimethyl-1,3-dioxolane-2-one, 4,4-difluoro-1,3-dioxolane-2-one, 4,4,5-trifluoro-1,3-dioxolane-2-one, 4-fluoromethyl-1,3-dioxolane-2-one, tetrafluoroethylene carbonate, 4-(2,2-difluoro 2. The liquid electrolyte for a lithium secondary battery according to claim 1, comprising: 4-(2,2,2-trifluoroethoxy)ethylene carbonate, 4-(2,2,2-trifluoroethoxy)ethylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, trimethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, dimethyl vinylene carbonate, ethyl propyl carbonate, cyclohexene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, or a mixture thereof.

8. c) the organic carbonate has the formula (III) R ６ -OC(O)O-R ７ (In the formula, R ６ and R ７ each represents an alkyl group; R ６ and R ７ The total number of carbon atoms in R is 2 to 7; and R ６ and / or R ７ At least one hydrogen atom of the formula (I) is replaced by fluorine.

2. The liquid electrolyte for a lithium secondary battery according to claim 1, comprising a fluorinated acyclic carbonate represented by:

9. The fluorinated acyclic carbonate is CH ３ -OC(O)O-CH ２ CF ２ H (Methyl 2,2-difluoroethyl carbonate), CH ３ -OC(O)O-CH ２ CF ３ (Methyl 2,2,2-trifluoroethyl carbonate), CH ３ -OC(O)O-CH ２ CF ２ CF ２ H (methyl 2,2,3,3-tetrafluoropropyl carbonate), CF ２ H.H.H. ２ -OC(O)O-CH ２ CF ３ (ethyl 2,2-difluoroethyl carbonate), CF ３ CH ２ -OC(O)O-CH ２ CH ３ 9. The liquid electrolyte for a lithium secondary battery according to claim 8, comprising (ethyl 2,2,2-trifluoroethyl carbonate) or a mixture thereof.

10. d) The lithium salt is lithium hexafluorophosphate (LiPF ６ ), 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), 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 alkyl groups and fluorinated alkyl groups, and 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 2. The liquid electrolyte for a lithium secondary battery according to claim 1, comprising:

11. 2. The liquid electrolyte for lithium secondary batteries according to claim 1, further comprising at least one film-forming additive in an amount of 0.05 to 5.0% by weight, preferably 0.05 to 3.0% by weight, based on the total weight of the liquid electrolyte.

12. e) The film forming additives include sulfur compounds including 1,3,2-dioxathiolane-2,2-dioxide, 1,3,2-dioxathiane-2,2-dioxide, 1,3-propane sultone, ethylene sulfite, and prop-1-ene-1,3-sultone; sulfone derivatives including dimethyl sulfone, tetramethylene sulfone (also known as sulfolane), ethyl methyl sulfone, and isopropyl methyl sulfone; nitrile derivatives including succinonitrile, adiponitrile, and glutaronitrile; and lithium nitrate (LiNO ３ ); lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalato)borate (LiB(C ２ O ４ ) ２ LiBOB), lithium fluoromalonato(difluoro)borate (LiB(O ２ CCHFCO ２ ) ２ LiFMDFB), lithium bis(malonato)borate [LiB(O ２ CCH ２ CO ２ ) ２ ], lithium bis(difluoromalonato)borate [LiB(O ２ CCF ２ CO ２ ) ２ ], lithium (malonato oxalato)borate [LiB(C ２ O ４ ) (O ２ CCH ２ CO ２ )], lithium (difluoromalonatooxalato)borate [LiB(C ２ O ４ ) (O ２ CCF ２ CO ２ boron derivative salts including lithium tris(oxalato)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 ), vinyl acetate, biphenylbenzene, isopropylbenzene, hexafluorobenzene, tris(trimethylsilyl)phosphate, triphenylphosphine, ethyldiphenylphosphinite, triethylphosphite, tris(2,2,2-trifluoroethyl)phosphite, maleic anhydride, cesium bis(trifluoromethanesulfonyl)imide (CsTFSI), cesium fluoride (CsF), and mixtures thereof.

13. A lithium secondary battery, an anode; a cathode; a separator; - a liquid electrolyte according to any one of claims 1 to 12; A lithium secondary battery comprising:

14. 14. The lithium secondary battery of claim 13, wherein the anode comprises graphitic carbon, silicon, or a silicon-carbon composite material.

15. 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 secondary battery according to claim 13, comprising a lithium-nickel-cobalt-aluminum-based metal oxide, a lithium-cobalt-based metal oxide, or a lithium-nickel-manganese-based metal oxide (LNMO) where x+y+z=1.

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