WO2021093265A1 - 一种电解液和电化学装置 - Google Patents

一种电解液和电化学装置 Download PDF

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WO2021093265A1
WO2021093265A1 PCT/CN2020/084960 CN2020084960W WO2021093265A1 WO 2021093265 A1 WO2021093265 A1 WO 2021093265A1 CN 2020084960 W CN2020084960 W CN 2020084960W WO 2021093265 A1 WO2021093265 A1 WO 2021093265A1
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lithium
electrolyte
carbon atoms
substituted
group
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PCT/CN2020/084960
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English (en)
French (fr)
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王振东
何�轩
褚春波
张耀
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欣旺达电动汽车电池有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of energy storage technology, in particular to an electrolyte and an electrochemical device.
  • lithium-ion batteries Compared with traditional lead-acid batteries, lithium-ion batteries have the advantages of small size, light weight, high specific energy, and long cycle life. They play an increasingly important role in the process of human production and life. However, in areas with higher latitudes or altitudes, the winter temperature is lower. When lithium batteries work in this environment, the viscosity of the electrolyte increases, the ion mobility decreases, the internal resistance of the battery increases sharply, and the lithium ionization window of the battery decreases, which is slightly larger. The high charging current may cause lithium precipitation, and the precipitated metallic lithium may form lithium dendrites that may pierce the diaphragm and affect the safety performance of the battery cell. At the same time, low temperature will also cause problems such as battery discharge capacity degradation, which seriously restricts the application of lithium-ion batteries.
  • embodiments of the present application provide an electrolyte and an electrochemical device.
  • the electrolyte provided by the embodiments of the present application has good cycle performance, low internal resistance at low temperature, excellent low-temperature discharge performance and a wide low-temperature charging lithium evolution window, which improves the electrochemical performance of electrochemical devices at low temperatures. .
  • the present application provides an electrolyte, which includes an organic solvent, a lithium salt, and additives, where the additives include cyclic sulfate, lithium difluorooxalate, and fluorosilane.
  • the cyclic sulfuric acid ester of the present application is selected from at least one of the compounds represented by the formula I,
  • R is selected from C 2-3 straight chain alkylene, substituted with a substituent A C 2-3 straight chain alkylene, substituted C 2-3 alkenyl group and a straight-chain alkylene group A is substituted C 2- 3 One of straight chain alkenylene groups;
  • the substituent A is selected from halogen atoms, alkoxy groups, carboxyl groups, sulfonic acid groups, alkyl groups with 1-20 carbon atoms, haloalkyl groups with 1-20 carbon atoms, and those with 2-20 carbon atoms At least one of an unsaturated hydrocarbon group and a halogenated unsaturated hydrocarbon group having 2-20 carbon atoms.
  • the cyclic sulfate of the present application is selected from at least one of the following compounds:
  • the fluorosilane of the present application is selected from at least one of the compounds represented by the formula II,
  • R 1, R 2, R 3, R 4 are each independently selected from hydrogen, halogen, C 1-10 alkyl, substituted C 1-10 alkyl group substituted with B, C 1-10 alkoxy, substituted substituent B C 1-10 alkoxy, C 2-10 alkenyl group, substituted with a substituent B C 2-10 alkenyl, C 2-10 alkynyl, substituted with B, C 2- 10
  • the substituent B is selected from halogen, alkoxy, carboxyl, sulfonic acid, alkyl with 1-20 carbon atoms, haloalkyl with 1-20 carbon atoms, and 2-20 carbon atoms. At least one of the unsaturated hydrocarbon group and the halogenated unsaturated hydrocarbon group having 2-20 carbon atoms.
  • the fluorosilane of the present application is selected from at least one of the following compounds:
  • the mass percentage of lithium difluorooxalate borate in the electrolyte of the present application is 0.1%-3.0%;
  • the mass percentage of lithium difluorooxalate borate in the electrolyte of the present application is 0.1%-2.0%.
  • the mass percentage of the cyclic sulfate in the electrolyte of the present application is 0.1%-4.0%;
  • the mass percentage of the cyclic sulfate in the electrolyte of the present application is 0.5%-3.0%.
  • the mass percentage content of the fluorosilane of the present application in the electrolyte is 0.1%-4.0%;
  • the mass percentage of the fluorosilane of the present application in the electrolyte is 0.3%-2.0%.
  • the additives of the present application also include vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, methylene methane disulfonate, and ethylene carbonate. At least one of ethylene, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, adiponitrile, and fumaronitrile.
  • the additives of the present application further include lithium salt additives, wherein the lithium salt additives include at least one of lithium tetrafluoroborate, lithium difluorophosphate, and lithium bisfluorosulfonimide.
  • the mass percentage of the lithium salt additive of the present application in the electrolyte is less than 3%.
  • the present invention also provides an electrochemical device, which includes a positive electrode sheet, a negative electrode sheet, a separator, and any one of the foregoing electrolytes.
  • the invention can effectively improve the low-temperature DC impedance of the battery, the low-temperature discharge performance, and the low-temperature charging lithium-depletion window of the battery by adding additives cyclic sulfate ester, lithium difluorooxalate borate and fluorosilane in the electrolyte.
  • the term "about” is used to describe and illustrate small changes.
  • the term can refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very closely.
  • the term can refer to a range of variation less than or equal to ⁇ 10% of the stated value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • the amount, ratio, and ratio are presented in a range format in this article Other values.
  • halogen encompasses fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).
  • hydrocarbyl encompasses alkyl, alkenyl, and alkynyl groups.
  • alkyl is intended to be a linear saturated hydrocarbon structure having 1 to 20 carbon atoms. "Alkyl” is also expected to be a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. When an alkyl group having a specific carbon number is specified, it is expected to encompass all geometric isomers having that carbon number; therefore, for example, “butyl” means to include n-butyl, sec-butyl, isobutyl, tert-butyl And cyclobutyl; “propyl” includes n-propyl, isopropyl and cyclopropyl.
  • alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopropyl Pentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-ethyl, hexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl Base and so on.
  • the alkyl group may be optionally substituted.
  • alkenyl refers to a monovalent unsaturated hydrocarbon group that may be branched or branched and has at least one and usually 1, 2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl group usually contains 2 to 20 carbon atoms and includes, for example, -C 2-4 alkynyl, -C 3-6 alkynyl, and -C 3-10 alkynyl. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like.
  • alkylene means a divalent saturated hydrocarbon group which may be linear or branched. Unless otherwise defined, the alkylene group usually contains 2 to 10 carbon atoms, and includes, for example, a -C 2-3 alkylene group and a -C 2-6 alkylene group. Representative alkylene groups include, for example, methylene, ethane-1,2-diyl ("ethylene”), propane-1,2-diyl, butane-1,4-diyl, pentane -1,5-diyl and so on.
  • alkenylene refers to a straight or branched chain alkenylene group, and the number of double bonds in the alkenyl group is preferably one. Specific examples of the alkenylene group include vinylene, allylylene, isopropenylene, alkenylene, and alkenylene pentylene.
  • aryl means a monovalent aromatic hydrocarbon having a single ring (for example, phenyl) or a condensed ring.
  • Condensed ring systems include those fully unsaturated ring systems (e.g., naphthalene) as well as those partially unsaturated ring systems (e.g., 1,2,3,4-tetrahydronaphthalene).
  • the aryl group generally contains 6 to 26 carbon ring atoms and includes, for example, a -C 6-10 aryl group.
  • Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl and naphth-1-yl, naphth-2-yl, and the like.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example two, if items A, B and C are listed, then the phrase "at least one of A, B and C" means only A; only B; only C; A and B (excluding C); A and C (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single element or multiple elements.
  • Project B can contain a single element or multiple elements.
  • Project C can contain a single element or multiple elements.
  • the relative content of each component is based on the total mass of the electrolyte.
  • This application relates to an electrolyte, including organic solvents, lithium salts and additives.
  • the additives include cyclic sulfates, lithium difluorooxalate and fluorosilane. Due to the combined use of cyclic sulfate and lithium difluorooxalate borate, SEI (Solid Electrolyte Interface) richer in organic components can be formed after the cell is formed, which increases the lithium ion in the pole piece and electrolysis. The permeability of the liquid interface reduces the interface impedance of the cell. Fluorinated silane does not participate in the formation of the SEI film, which can improve the low-temperature conductivity of the electrolyte in the cell.
  • the synergistic effect of cyclic sulfate, lithium difluorooxalate and fluorosilane improves the lithium ion between the positive and negative electrodes.
  • the conduction of the battery cell reduces the low-temperature DC resistance (DCR) of the battery cell, improves the battery cell's low-temperature charging and lithium-discharging window and low-temperature discharge performance, and improves the cycle performance.
  • DCR low-temperature DC resistance
  • the mass percentage of lithium difluorooxalate borate in the electrolyte of the present application is about 0.1%-3.0%.
  • the content of lithium difluorooxalate borate is less than 0.1%, the film-forming ability is insufficient, resulting in limited improvement of battery cell performance; when the content of lithium difluorooxalate borate is greater than 3%, the film formation is too thick and the lithium ion permeability decreases , The impedance increases.
  • the content of lithium difluorooxalate is in the range of about 0.1%-3.0%, it can form a dense and organic-rich SEI film with the cyclic sulfate in the cell formation stage, inhibiting the pole pieces and the electrolyte. Response, improve gas production, thereby improving cell impedance performance and cycle performance.
  • the mass percentage of lithium difluorooxalate borate in the electrolyte is about 0.1%-2.0%.
  • the cyclic sulfate of the present application is selected from at least one of the compounds represented by the formula I,
  • R is selected from C 2-3 straight chain alkylene, substituted with a substituent A C 2-3 straight chain alkylene, substituted C 2-3 alkenyl group and a straight-chain alkylene group A is substituted C 2- 3 One of straight chain alkenylene groups;
  • the substituent A is selected from halogen atoms, alkoxy groups, carboxyl groups, sulfonic acid groups, alkyl groups with 1-20 carbon atoms, haloalkyl groups with 1-20 carbon atoms, and those with 2-20 carbon atoms. At least one of an unsaturated hydrocarbon group and a halogenated unsaturated hydrocarbon group having 2-20 carbon atoms.
  • the cyclic sulfate of the present application is selected from at least one of the following compounds:
  • the mass percentage of the cyclic sulfate of the present application in the electrolyte is about 0.1%-4.0%.
  • the mass percentage of the cyclic sulfate in the electrolyte is about 0.5%-3.0%, which is probably due to the film-forming ability when the content of the cyclic sulfate is less than 0.5% Insufficiency leads to limited improvement in battery cell performance.
  • the content of the cyclic sulfate is higher than 3.0%, the formation of the film is too thick, resulting in a decrease in lithium ion permeability and an increase in impedance.
  • the fluorinated silane of the present application is selected from at least one of the compounds represented by the formula II,
  • R 1, R 2, R 3, R 4 are each independently selected from hydrogen, halogen, C 1-10 alkyl, substituted C 1-10 alkyl group substituted with B, C 1-10 alkoxy, substituted substituent B C 1-10 alkoxy, C 2-10 alkenyl group, substituted with a substituent B C 2-10 alkenyl, C 2-10 alkynyl, substituted with B, C 2- 10
  • the substituent B is selected from the group consisting of halogen, alkoxy, carboxyl, sulfonic acid, alkyl with 1-20 carbon atoms, haloalkyl with 1-20 carbon atoms, and non-carbon atoms with 2-20 carbon atoms. At least one of a saturated hydrocarbon group and a halogenated unsaturated hydrocarbon group having 2-20 carbon atoms.
  • the fluorosilane of the application is selected from at least one of the following compounds:
  • the mass percentage of the fluorosilane of the present application in the electrolyte is about 0.1%-4.0%.
  • the mass percentage of the fluorosilane is about 0.3%-2.0%.
  • the content of the fluorosilane is less than 0.3%, its effect on the low-temperature conductivity of the electrolyte is not obvious, and when the mass percentage of the fluorosilane is higher than 2.0%, the boiling point of the fluorosilane is generally lower, and the battery The vapor pressure of the electrolyte is too high during use, which is easy to cause safety problems.
  • the additives of the application also include vinylene carbonate (VC), 1,3-propane sultone (PS), 1-propene-1,3-sultone (PST), methane disulfonate At least one of methylene acid (MMDS), vinyl ethylene carbonate (VEC), tris(trimethylsilyl) phosphate (TMSP), and tris(trimethylsilyl) phosphite additives.
  • VC vinylene carbonate
  • PS 1,3-propane sultone
  • PST 1-propene-1,3-sultone
  • methane disulfonate At least one of methylene acid (MMDS), vinyl ethylene carbonate (VEC), tris(trimethylsilyl) phosphate (TMSP), and tris(trimethylsilyl) phosphite additives.
  • MMDS methylene acid
  • VEC vinyl ethylene carbonate
  • TMSP tris(trimethylsilyl) phosphite additives
  • the additives of the application further include lithium salt additives, where the lithium salt additives include at least one of lithium tetrafluoroborate, lithium difluorophosphate, and lithium bisfluorosulfonimide. Furthermore, the mass percentage of the lithium salt additive in the electrolyte in this application is less than 3.0%. The introduction of the above-mentioned lithium salt additives can further optimize the characteristics of the electrode-electrolyte interface film, thereby improving the performance of the battery cell.
  • the organic solvent of the present application may be selected from at least one of cyclic carbonate and chain carbonate.
  • the cyclic carbonate includes at least one of ethylene carbonate, fluoroethylene carbonate, and propylene carbonate
  • the chain ethylene carbonate includes dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate. At least one.
  • the organic solvent of this application can also be selected from other solvents, and this application is not specifically limited.
  • the lithium salt of the application is selected from at least one of organic lithium salt and inorganic lithium salt. Further, the lithium salt in this application may contain at least one of fluorine, boron, and phosphorus. Further, the lithium salt of the present application can be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium bisoxalate borate (LiBOB), lithium hexafluoroarsenate (LiAsF 6 ), lithium difluorophosphate (LiPO) 2 F 2 ), lithium bis(trifluoromethylsulfonyl) imide (LiN(CF 3 SO 2 ) 2 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium perchlorate (LiClO 4 ) At least one of.
  • LiPF 6 lithium tetrafluoroborate
  • LiBOB lithium bisoxalate borate
  • LiAsF 6 lithium di
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors.
  • the electrochemical device includes a lithium secondary battery, specifically, it includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, and a lithium ion polymer secondary battery. In the specific embodiments of the present application, only the embodiments of the lithium ion battery are shown, but the present application is not limited thereto.
  • the application also provides a lithium ion battery, including a positive electrode sheet, a negative electrode sheet, a separator arranged between the positive electrode sheet and the negative electrode sheet, an electrolyte and a packaging foil;
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode current collector coated on the separator
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film coated on the negative electrode current collector;
  • the electrolyte is any one of the above-mentioned electrolytes.
  • the positive electrode membrane of the present application includes a positive electrode active material, a binder, and a conductive agent. Furthermore, the positive electrode active material of the present application is selected from at least one of lithium cobalt oxide, lithium nickel manganese cobalt ternary material, lithium iron phosphate, and lithium manganate.
  • the negative electrode membrane of the present application includes a negative electrode active material, a binder, and a conductive agent.
  • the negative electrode active material of the present application can be selected from any one of graphite, silicon, or silicon-carbon composite materials.
  • the silicon-carbon composite material refers to a negative electrode active material obtained by doping silicon-carbon at any ratio.
  • Electrolyte preparation in an argon atmosphere glove box (H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm), ethylene carbonate (simplified EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) ) After mixing uniformly according to the mass ratio of 40:30:30, a non-aqueous solvent is obtained, and then fully dried lithium salt LiPF 6 is dissolved in the above non-aqueous solvent to prepare a basic electrolyte with a LiPF 6 concentration of 1.3 mol/L.
  • H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • cyclic sulfates are: ethylene glycol cyclic sulfate (S), 1,2-propanediol cyclic sulfate (S1), 2,3-butanediol cyclic sulfate (S2), 1-fluoroethyl Diol cyclic sulfate (S3), 1-trifluoromethyl glycol cyclic sulfate (S4), 1,3-propanediol cyclic sulfate (S5), 2-methyl-1,3-propanediol cyclic sulfate (S6), 2-fluoro-1,3-propanediol cyclic sulfate (S7).
  • S ethylene glycol cyclic sulfate
  • S1 1,2-propanediol cyclic sulfate
  • S2 2,3-butanediol cyclic sulfate
  • S3 1-fluoroethy
  • fluorosilanes examples include trimethylfluorosilane (F), triethylfluorosilane (F1), dimethylethylfluorosilane (F2), trimethylsilyl-dimethylfluorosilane (F3 ), trimethoxyfluorosilane (F4), dimethyldifluorosilane (F5), methyltrifluorosilane (F6), ethyltrifluorosilane (F7).
  • F trimethylfluorosilane
  • F1 triethylfluorosilane
  • F2 dimethylethylfluorosilane
  • F3 trimethylsilyl-dimethylfluorosilane
  • trimethoxyfluorosilane F4
  • dimethyldifluorosilane F5
  • methyltrifluorosilane F6
  • ethyltrifluorosilane ethyltrifluorosilane
  • positive electrode sheet the positive electrode active material lithium nickel cobalt manganese (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ), conductive agent acetylene black, binder polyvinylidene fluoride (PVDF) according to the weight ratio of 97:2:1
  • NMP N-methylpyrrolidone
  • the electrolytes and lithium ion batteries of Examples 1-32 and Comparative Examples 1-7 were prepared according to the above-mentioned preparation method; the additives in the electrolyte and their respective addition amounts are shown in Table 1.
  • the prepared lithium-ion batteries were all subjected to the following tests:
  • Example 1 Group Capacity retention rate (%) Example 1 78.5 Example 2 81.1 Example 3 84.6 Example 4 89.1 Example 5 81.4 Example 6 74.8 Example 7 82.6 Example 8 84.2 Example 9 86.7 Example 10 86.2 Example 11 83.1 Example 12 77.8 Example 13 87.4 Example 14 88.1 Example 15 87.3 Example 16 88.6 Example 17 87.5 Example 18 87.7 Example 19 81.5 Example 20 83.2 Example 21 85.2 Example 22 84.7 Example 23 81.4 Example 24 82.4 Example 25 81.2 Example 26 87.5 Example 27 88.2 Example 28 87.4 Example 29 89.2 Example 30 87.2 Example 31 88.1
  • Example 32 87.6 Comparative example 1 59.7 Comparative example 2 83.2 Comparative example 3 70.9 Comparative example 4 61.3 Comparative example 5 88.5 Comparative example 6 82.7 Comparative example 7 69.3
  • the prepared lithium-ion batteries were all subjected to the following tests:
  • Example 19 267.7 Example 20 256.9 Example 21 272.1 Example 22 258.3 Example 23 264.1
  • Example 24 259.1 Example 25 252.9 Example 26 245.6 Example 27 241.9 Example 28 246.2 Example 29 251.9 Example 30 245.3 Example 31 241.0 Example 32 244.9 Comparative example 1 359.7 Comparative example 2 298.1 Comparative example 3 321.3 Comparative example 4 329.8 Comparative example 5 278.2 Comparative example 6 271.9 Comparative example 7 306.1
  • the prepared lithium-ion batteries were all subjected to the following tests:
  • Example 1 Group Low temperature discharge capacity retention rate (%) Example 1 52.4 Example 2 57.5 Example 3 63.8 Example 4 66.9 Example 5 63.2 Example 6 57.1 Example 7 60.1 Example 8 62.4 Example 9 64.4 Example 10 65.1 Example 11 61.8 Example 12 58.2 Example 13 58.1
  • Example 14 62.6 Example 15 68.1 Example 16 71.2 Example 17 73.7 Example 18 74.9 Example 19 52.7 Example 20 54.9 Example 21 53.3 Example 22 57.2 Example 23 58.0 Example 24 56.8 Example 25 55.1 Example 26 65.1 Example 27 65.8 Example 28 63.2 Example 29 61.1 Example 30 63.9 Example 31 62.0 Example 32 63.6 Comparative example 1 37.2 Comparative example 2 54.9 Comparative example 3 41.5 Comparative example 4 44.2 Comparative example 5 58.8 Comparative example 6 59.5 Comparative example 7 48.2
  • the prepared lithium-ion batteries were all subjected to the following tests:
  • the cut-off current is 0.05C, and let stand for 5 minutes; then put the battery cell at 25°C, stand for 2h, and then charge to 4.3V with 1C constant current and constant voltage.
  • the cut-off current is 0.05C;
  • the percentage of lithium-evolving area the area of the lithium-evolving part/total area of the negative electrode*100%, and the recorded results are shown in Table 5.
  • the prepared lithium-ion batteries were all subjected to the following tests:
  • Example 1 Group High temperature storage thickness expansion rate ⁇ (%) Example 1 40.1 Example 2 35.5 Example 3 32.2 Example 4 29.5 Example 5 27.7 Example 6 25.9 Example 7 29.9 Example 8 30.1 Example 9 30.1 Example 10 28.7 Example 11 29.6 Example 12 31.5 Example 13 28.7 Example 14 28.6 Example 15 35.9 Example 16 44.1 Example 17 53.9 Example 18 60.9 Example 19 33.2 Example 20 32.1 Example 21 30.4 Example 22 31.2 Example 23 32.9 Example 24 33.1 Example 25 30.5 Example 26 29.4 Example 27 28.6 Example 28 27.9 Example 29.7 Example 30 32.7 Example 31 34.6 Example 32 32.8
  • Comparative example 1 51.7 Comparative example 2 27.8 Comparative example 3 45.2 Comparative example 4 52.2 Comparative example 5 28.1 Comparative example 6 29.4 Comparative example 7 46.2
  • the mass percentage of ethylene glycol cyclic sulfate is 0.1%-4.0%, and the preferred mass percentage is 0.5%-3.0%.
  • Comparative Example 1 and Comparative Example 3 It can be seen from Comparative Example 1 and Comparative Example 3 that only adding lithium difluorooxalate borate can slightly improve the cycle performance of the cell, but the improvement of other properties of the cell is relatively limited, indicating that only lithium difluorooxalate borate is used. The membrane cannot effectively inhibit the side reaction between the pole piece and the electrolyte solvent. It can be seen from Comparative Example 5 that when lithium difluorooxalate borate is used in combination with ethylene glycol cyclic sulfate, the cycle performance, low-temperature DCR, low-temperature discharge capacity and discharge capacity of the cell can be further improved compared to only adding ethylene glycol cyclic sulfate.
  • Example 4 and Examples 7-12 From Comparative Example 2 and Comparative Example 3, Example 4 and Examples 7-12, it can be seen that in the presence of ethylene glycol cyclic sulfate, when the concentration of lithium difluorooxalate is low, as the concentration increases, the The improvement effect of the core cycle performance is increased. When the concentration further increases, the low temperature resistance of the battery cell will increase and the cycle performance will decrease. This is because when the concentration of lithium difluorooxalate borate is low, the film-forming ability is insufficient, resulting in limited improvement in cell performance. As its concentration increases, the formation is more conducive to lithium ion penetration and inhibits electrode-electrolyte side reactions The SEI film enhances the improvement effect of the battery cell cycle.
  • the content is too high, the film formation is too thick, resulting in a decrease in lithium ion permeability, an increase in impedance, and a decrease in cycle performance.
  • the preferred quality of lithium difluorooxalate borate is 0.1 to 2.0%.
  • trimethylfluorosilane when its concentration is low, trimethylfluorosilane can be dissolved in the electrolysis In the liquid, when the concentration is too high, trimethylfluorosilane with a boiling point of only 16°C will volatilize from the electrolyte, resulting in increased gas production. Too high concentration is likely to bring safety hazards. On the whole, trimethyl fluoride
  • the preferred mass percentage content of silane is 0.3% to 2.0%.
  • trimethylfluorosilane does not participate in the formation of the SEI film on the electrode surface, it can improve Low temperature conductivity of electrolyte.
  • ethylene glycol cyclosulfate, lithium difluorooxalate borate and trimethylfluorosilane the conduction of lithium ions between the positive and negative electrodes is improved, which makes the cell low-temperature resistance, low-temperature charging lithium evolution window and low-temperature discharge performance Significant improvement, and the battery has better cycle performance.
  • the cyclic sulfuric acid ester can improve the gas production, circulation and low-temperature performance of the cell to a certain extent. This is because of the cyclic sulfuric acid
  • the ester structure compound can form a film on the surface of the electrode to form an SEI film that is conducive to the penetration of lithium ions and can inhibit the electrode-electrolyte side reaction, thereby improving the performance of the cell.
  • Example 6 From Comparative Example 5, Example 4 and Examples 25 to 31, it can be seen that the methyltrifluorosilane and ethyltrifluorosilane in the fluorosilane will increase the cell production compared to other types of fluorosilane. Other silanes have little effect on the gas production performance of the cell. This is because methyltrifluorosilane and ethyltrifluorosilane have lower boiling points and are easier to volatilize from the electrolyte, resulting in an increase in gas production.
  • the fluorosilane has no significant effect on the cycle performance of the cell, and can improve the low-temperature DCR, low-temperature discharge performance, and low-temperature charging lithium-ion window of the cell to a certain extent. This is because the fluorosilane structure can interact with lithium ions to a certain extent. The low-temperature conductivity of the electrolyte is reduced, and the low-temperature performance of the cell is improved.

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Abstract

一种电解液和电化学装置。该电解液包括有机溶剂、锂盐和添加剂，其中添加剂包括环状硫酸酯、二氟草酸硼酸锂和氟代硅烷。通过添加剂环状硫酸酯、二氟草酸硼酸锂和氟代硅烷的协同作用，可以有效改善电池的低温直流阻抗，低温放电性能以及电芯低温充电析锂窗口，从而提高电化学装置的低温电化学性能。

Description

一种电解液和电化学装置 技术领域
本申请涉及储能技术领域，具体涉及一种电解液和电化学装置。
背景技术
锂离子电池相比于传统铅酸电池，具有体积小，重量轻，比能量高，循环寿命长等优点，在人类生产生活过程中扮演着越来越重要的角色。然而在纬度或海拔较高的地区，冬季气温较低，锂电池在这种环境下工作，电解液粘度增加，离子迁移率降低，电池内阻急剧增加，电池充电析锂窗口减小，稍大的充电电流就可能造成析锂，析出的金属锂形成锂枝晶可能会刺穿隔膜，影响电芯安全性能，同时低温还会造成电池放电容量衰减等问题，严重制约着锂离子电池的应用。
技术问题
为了解决上述技术问题，本申请实施例提供了一种电解液和一种电化学装置。本申请实施例提供的电解液具有良好的循环性能，在低温下具有较低的内阻，优异低温放电性能及较宽的低温充电析锂窗口，提高了电化学装置在低温下的电化学性能。
技术解决方案
在一个实施例中，本申请提供了一种电解液，电解液包括有机溶剂、锂盐和添加剂，其中添加剂包括环状硫酸酯、二氟草酸硼酸锂和氟代硅烷。
根据本申请的实施例，本申请环状硫酸酯选自结构式为式I所示化合物中的至少一种，
Figure PCTCN2020084960-appb-000001
其中，R选自C 2-3直链亚烷基、被取代基A取代的C 2-3直链亚烷基、C 2-3直链亚烯基及被取代基A取代的C 2-3直链亚烯基中的一种；
所述取代基A选自卤素原子、烷氧基、羧基、磺酸基、碳原子数为1-20的烷基、碳原子数为1-20的卤代烷基、碳原子数为2-20的不饱和烃基及碳原子数为2-20的卤代不饱和烃基中的至少一种。
根据本申请的实施例，本申请环状硫酸酯选自以下化合物中的至少一种：
Figure PCTCN2020084960-appb-000002
Figure PCTCN2020084960-appb-000003
根据本申请的实施例，本申请氟代硅烷选自结构式为式II所示化合物中的至少一种，
Figure PCTCN2020084960-appb-000004
其中，R 1、R 2、R 3、R 4各自独立地选自氢、卤素、C 1-10烷基、被取代基B取代的C 1-10烷基、C 1-10烷氧基、被取代基B取代的C 1-10烷氧基、C 2-10烯基、被取代基B取代的C 2-10烯基、C 2-10炔基、被取代基B取代的C 2-10炔基、含硅基团中的一种；且R 1、R 2、R 3、R 4中至少一个为氟原子取代基；
其中，所述取代基B选自卤素、烷氧基、羧基、磺酸基、碳原子数为1-20的烷基、碳原子数为1-20的卤代烷基、碳原子数为2-20的不饱和烃基及碳原子数为2-20的卤代不饱和烃基中的至少一种。
根据本申请的实施例，本申请氟代硅烷选自以下化合物中的至少一种：
Figure PCTCN2020084960-appb-000005
根据本申请的实施例，本申请二氟草酸硼酸锂在电解液中的质量百分含量为0.1％-3.0％；
根据本申请的实施例，本申请二氟草酸硼酸锂在电解液中的质量百分含量为0.1％-2.0％。
根据本申请的实施例，本申请环状硫酸酯在电解液中的质量百分含量为0.1％-4.0％；
根据本申请的实施例，本申请环状硫酸酯在电解液中的质量百分含量为0.5％-3.0％。
根据本申请的实施例，本申请氟代硅烷在电解液中的质量百分含量为0.1％-4.0％；
根据本申请的实施例，本申请氟代硅烷在电解液中的质量百分含量为0.3％-2.0％。
根据本申请的实施例，本申请添加剂还包括碳酸亚乙烯酯、1,3-丙烷磺酸内酯、1-丙烯-1,3-磺酸内酯、甲烷二磺酸亚甲酯、碳酸乙烯亚乙酯、三(三甲基硅基)磷酸酯、三(三甲基硅基)亚磷酸酯、己二腈及反丁烯二腈中的至少一种。
根据本申请的实施例，本申请添加剂还包括锂盐添加剂，其中锂盐添加剂包括四氟硼酸锂、二氟磷酸锂及双氟磺酰亚胺锂中的至少一种。
根据本申请的实施例，本申请锂盐添加剂在电解液中的质量百分含量低于3％。
本发明还提供了一种电化学装置，包括正极片，负极片，隔膜和上述任意一种电解液。
有益效果
本发明通过在电解液中添加添加剂环状硫酸酯，二氟草酸硼酸锂和氟代硅烷，能够有效改善电池的低温直流阻抗，低温放电性能以及电芯低温充电析锂窗口。
本发明的最佳实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合本申请实施例，对本申请的技术方案进行清楚、完整地描述。显然，所描述的实施例是本申请的一部分实施例，而不是全部的实施例，本申请的实施例不应该被解释为对本申请的限制。基于本申请提供的技术方案及所给出的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
除非另外明确指明，本文使用的下文术语具有下文指出的含义。
术语“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数据使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％.另外，有时在本文中以范围格式呈现量、比率和其他数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地制定为范围限制的数值，而且包涵盖于所述范围内的所有个别数值或范围，如同明确地制定每一数值及子范围一般。
术语“卤素”涵盖氟(F)、氯(Cl)、溴(Br)、碘(I)。
术语“烃基”涵盖烷基、烯基、炔基。
术语“烷基”预期是具有1至20个碳原子的直链饱和烃结构。“烷基”还预期是具有3至20个碳原子的支链或环状烃结构。当指定具有具体碳数的烷基时，预期涵盖具有该碳 数的所有几何异构体；因此，例如，“丁基”意思是包括正丁基、仲丁基、异丁基、叔丁基和环丁基；“丙基”包括正丙基、异丙基和环丙基。烷基实例包括但不限于甲基、乙基、正丙基、异丙基、环丙基、正丁基、异丁基、仲丁基、叔丁基、环丁基、正戊基、异戊基、新戊基、环戊基、甲基环戊基、乙基环戊基、正乙基、已己基、环己基、正庚基、辛基、环丙基、环丁基、降冰片基等。另外，烷基可以任选地被取代。
术语“烯基”是指可为支链或具有支链且具有至少一个且通常1个、2个或3个碳碳双键的单价不饱和烃基团。除非另有定义，否则所述烯基通常含有2个到20个碳原子且包括例如，-C 2-4炔基、-C 3-6炔基及-C 3-10炔基。代表性炔基包括例如，乙炔基、丙-2-炔基(正-丙炔基)、正-丁-2-炔基、正-己-3-炔基等。
术语“亚烷基”意指可为直链或具有支链的二价饱和烃基。除非另有定义，否则所述亚烷基通常含有2到10个碳原子，且包括例如，-C 2-3亚烷基和-C 2-6亚烷基。代表性亚烷基包括例如，亚甲基、乙烷-1,2-二基(“亚乙基”)、丙烷-1,2-二基、丁烷-1,4-二基、戊烷-1,5-二基等。
术语“亚烯基”为直链或支链亚烯基，烯基中双键的个数优选为1个。作为亚烯基的实例，具体可以举出：亚乙烯基、亚烯丙基、亚异丙烯基、亚烯丁基、亚烯戊基。
术语“芳基”意指具有单环(例如，苯基)或稠合环的单价芳香族烃。稠合环系统包括那些完全不饱和的环系统(例如，萘)以及那些部分不饱和的环系统(例如，1,2,3,4-四氢萘)。除非另有定义，否则所述芳基通常含有6-26个碳环原子且包括(例如)-C 6-10芳基。代表性芳基包括(例如)苯基、甲基苯基、丙基苯基、异丙基苯基、苯甲基和萘-1-基、萘-2-基等。
在具体实施方式及权利要求中，由术语“中的至少一种”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一种”意味着仅A；仅B；或A及B。在另一实例二中，如果列出项目A、B及C，那么短语“A、B及C中的至少一种”意味着仅A；仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
如本文中所使用，各组分的相对含量均基于电解液的总质量得到的。
本申请涉及一种电解液，包括有机溶剂、锂盐和添加剂，添加剂包括环状硫酸酯、二氟草酸硼酸锂和氟代硅烷。由于，环状硫酸酯与二氟草酸硼酸锂联合使用，在电芯化成后能够形成更加富含有机组分的SEI(固体电解质界面膜，Solid Electrolyte Interface)，增加了锂离子在极片与电解液界面的通透性，降低了电芯的界面阻抗。氟代硅烷不参与SEI膜的形 成，其可以改善电芯中电解液的低温电导率通过环状硫酸酯，二氟草酸硼酸锂和氟代硅烷的协同作用，改善了锂离子在正负极间的传导，使得电芯低温直流电阻(DCR)得以降低，电芯低温充电析锂窗口和低温放电性能得以改善，循环性能提升。
在一些实施例中，本申请二氟草酸硼酸锂在电解液中的质量百分含量约为0.1％-3.0％。当二氟草酸硼酸锂含量低于0.1％时，成膜能力不足，导致对电芯性能改善有限；而当二氟草酸硼酸锂含量大于3％时，成膜太厚导致锂离子通透性下降，阻抗增加。当二氟草酸硼酸锂的含量处于约0.1％-3.0％范围内时，其可以与环状硫酸酯在电芯化成阶段形成致密且富含有机组分的SEI膜，抑制极片与电解液副反应，改善产气，从而改善电芯阻抗性能和循环性能。
在一些实施例中，二氟草酸硼酸锂在电解液中的质量百分含量约为0.1％-2.0％。
在一些实施例中，本申请环状硫酸酯选自结构式为式I所示化合物中的至少一种，
Figure PCTCN2020084960-appb-000006
其中，R选自C 2-3直链亚烷基、被取代基A取代的C 2-3直链亚烷基、C 2-3直链亚烯基及被取代基A取代的C 2-3直链亚烯基中的一种；
其中，取代基A选自卤素原子、烷氧基、羧基、磺酸基、碳原子数为1-20的烷基、碳原子数为1-20的卤代烷基、碳原子数为2-20的不饱和烃基及碳原子数为2-20的卤代不饱和烃基中的至少一种。
在一些实施例中本申请环状硫酸酯选自以下化合物中的至少一种：
Figure PCTCN2020084960-appb-000007
Figure PCTCN2020084960-appb-000008
在一些实施例中本申请环状硫酸酯在电解液中的质量百分含量约为0.1％-4.0％。
在一些实施例中所述环状硫酸酯在电解液中的质量百分含量约为0.5％-3.0％，很有可能是由于当所述环状硫酸酯含量低于0.5％时，成膜能力不足，导致对电芯性能改善有限，当所述环状硫酸酯含量高于3.0％时，成膜太厚导致锂离子通透性下降，阻抗增加。
在一些实施例中本申请氟代硅烷选自结构式为式II所示化合物中的至少一种，
Figure PCTCN2020084960-appb-000009
其中，R 1、R 2、R 3、R 4各自独立地选自氢、卤素、C 1-10烷基、被取代基B取代的C 1-10烷基、C 1-10烷氧基、被取代基B取代的C 1-10烷氧基、C 2-10烯基、被取代基B取代的C 2-10烯基、C 2-10炔基、被取代基B取代的C 2-10炔基、含硅基团中的一种；且R 1、R 2、R 3、R 4中至少一个为氟原子取代基；
其中，取代基B选自卤素、烷氧基、羧基、磺酸基、碳原子数为1-20的烷基、碳原子数为1-20的卤代烷基、碳原子数为2-20的不饱和烃基及碳原子数为2-20的卤代不饱和烃基中的至少一种。
在一些实施例中本申请氟代硅烷选自以下化合物中的至少一种：
Figure PCTCN2020084960-appb-000010
在一些实施例中本申请氟代硅烷在电解液中的质量百分含量约为0.1％-4.0％。
在一些实施例中所述氟代硅烷质量百分含量约为0.3％-2.0％。当所述氟代硅烷含量低于0.3％时，其对电解液低温电导率的影响不明显，而当氟代硅烷质量百分含量高于2.0％时，因氟代硅烷沸点普遍较低，电池在使用过程中电解液蒸气压过高，容易引发安全问题。
在一些实施例中本申请添加剂还包括碳酸亚乙烯酯(VC)、1,3-丙烷磺酸内酯(PS)、1-丙烯-1,3-磺酸内酯(PST)、甲烷二磺酸亚甲酯(MMDS)、碳酸乙烯亚乙酯(VEC)、三(三甲基硅基)磷酸酯(TMSP)及三(三甲基硅基)亚磷酸酯添加剂中的至少一种。以上添加剂的加入可以进一步的优化电极-电解液界面膜特性，从而改善电芯性能。
在一些实施例中本申请添加剂还包括锂盐添加剂，其中，锂盐添加剂包括四氟硼酸锂、二氟磷酸锂及双氟磺酰亚胺锂中的至少一种。更进一步的，本申请中锂盐添加剂在电解液中的质量百分含量低于3.0％。上述锂盐添加剂的引入可以进一步优化电极-电解液界面膜特性，从而改善电芯性能。
在一些实施例中本申请有机溶剂可选自环状碳酸酯和链状碳酸酯中的至少一种。其中环状碳酸酯包括碳酸乙烯酯、氟代碳酸乙烯酯、碳酸丙烯酯的至少一种，链状碳酸乙烯酯包括碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸二丙酯的至少一种。本申请有机溶剂还可以选自其他溶剂，本申请不再具体限定。
在一些实施例中本申请锂盐选自有机锂盐和无机锂盐中的至少一种。进一步的，本申请中锂盐可含有氟元素、硼元素、磷元素中的至少一种。进一步的，本申请锂盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二草酸硼酸锂(LiBOB)、六氟合砷酸锂(LiAsF 6)、二氟磷酸锂(LiPO 2F 2)、二(三氟甲基磺酰)亚胺锂(LiN(CF 3SO 2) 2)、三氟甲磺酸锂(LiCF 3SO 3)、高氯酸锂(LiClO 4)中的至少一种。
本申请还涉及一种电化学装置，包括正极片、负极片和上述任一种电解液。本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池和电容器。特别地，该电化学装置包括锂二次电池，具体而言，其包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池和锂离子聚合物二次电池。在本申请的下属具体实施例中，仅示出锂离子电池的实施例，但本申请不限于此。
本申请还提供了一种锂离子电池，包括正极片、负极片、间隔设置于正极片和负极片之间的隔膜，电解液以及包装箔；正极片包括正极集流体及涂布在正极集流体上的正极膜片，负极片包括负极集流体及涂布在负极集流体上的负极膜片；电解液为上述任意一种电解液。
在一些实施例中本申请正极膜片包括正极活性材料、粘接剂和导电剂。更进一步的，本申请正极活性材料选自钴酸锂、锂镍锰钴三元材料、磷酸铁锂、锰酸锂中的至少一种。
在一些实施例中本申请负极膜片包括负极活性材料、粘结剂和导电剂。更进一步的，本申请负极活性材料可以选自石墨、硅或硅碳复合材料的任一种。其中，硅碳复合材料是指硅碳以任意比例掺杂得到的负极活性材料。
以下通过具体实施例对本申请的技术方案做示例性描述：
电解液的制备：在氩气氛围手套箱中(H 2O<0.1ppm,O 2<0.1ppm)，将碳酸乙烯酯(简EC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)按照40:30:30的质量比混合均匀后，得到非水溶剂，再将充分干燥的锂盐LiPF 6溶解于上述非水溶剂，配成LiPF 6浓度为1.3mol/L的基础电 解液。
按照表1所示，在基础电解液中加入环状硫酸酯、二氟草酸硼酸锂和氟代硅烷。
作为环状硫酸酯的实例为：乙二醇环硫酸酯(S)、1,2-丙二醇环硫酸酯(S1)、2,3-丁二醇环硫酸酯(S2)、1-氟代乙二醇环硫酸酯(S3)、1-三氟甲基乙二醇环硫酸酯(S4)、1,3-丙二醇环硫酸酯(S5)、2-甲基-1,3-丙二醇环硫酸酯(S6)、2-氟-1,3-丙二醇环硫酸酯(S7)。
作为氟代硅烷的实例为：三甲基氟硅烷(F)、三乙基氟硅烷(F1)、二甲基乙基氟硅烷(F2)、三甲基硅基-二甲基氟硅烷(F3)、三甲氧基氟硅烷(F4)、二甲基二氟硅烷(F5)、甲基三氟硅烷(F6)、乙基三氟硅烷(F7)。
表1 实施例1-32以及对比例1-7的电解液添加剂及添加量
Figure PCTCN2020084960-appb-000011
Figure PCTCN2020084960-appb-000012
Figure PCTCN2020084960-appb-000013
Figure PCTCN2020084960-appb-000014
锂离子电池的制备：
1)正极片的制备：将正极活性材料锂镍钴锰(LiNi 0.8Co 0.1Mn 0.1O 2)、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按照重量比97:2:1在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料；将此浆料涂覆于正极集流体铝箔上，经烘干、辊压、裁片后得到正极片。
2)负极片的制备：将负极活性材料石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)按照重量比96:1:3在适量的去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料；将此浆料涂覆于负极集流体铜箔上，经烘干、辊压、裁片后得到负极片。
3)锂离子电池的制备：将正极片、隔膜、负极片按照顺序叠好，使隔离膜处于正极片和负极片之间起到隔离的作用，然后经卷绕，热压整形，极耳焊接，得到裸电芯；将裸电芯置于外包装箔中，将上述制备好的电解液注入到干燥后的电池中，经真空封装、静置，化成，整形等工序，即完成锂离子电池的制备。
按照上述制备方法制备实施例1-32以及对比例1-7的电解液及锂离子电池；电解液中添加剂及各自的添加量如表1所示。
以下将通过实验对本申请各对比例和实施例的锂电子电池进行性能测试。
测试一、循环实验
将制备得到的锂离子电池均分别进行下述测试：
在25℃条件下，以1C/1C的充放电倍率在2.8-4.3V电压范围内进行充放电循环测试，并分别记录电池的首次充放电容量及每次循环后的放电容量，循环500次，计算各个锂电池的容量保留率，其中，容量保持率＝每次循环放电容量/电池首次放电容量*100％。各个锂离子电池所选用的电解液以及循环500次后容量保持率的数据参见表2。
表2 实施例1-32以及对比例1-7的锂离子电池电容保留率
组别 容量保持率(％)
实施例1 78.5
实施例2 81.1
实施例3 84.6
实施例4 89.1
实施例5 81.4
实施例6 74.8
实施例7 82.6
实施例8 84.2
实施例9 86.7
实施例10 86.2
实施例11 83.1
实施例12 77.8
实施例13 87.4
实施例14 88.1
实施例15 87.3
实施例16 88.6
实施例17 87.5
实施例18 87.7
实施例19 81.5
实施例20 83.2
实施例21 85.2
实施例22 84.7
实施例23 81.4
实施例24 82.4
实施例25 81.2
实施例26 87.5
实施例27 88.2
实施例28 87.4
实施例29 89.2
实施例30 87.2
实施例31 88.1
实施例32 87.6
对比例1 59.7
对比例2 83.2
对比例3 70.9
对比例4 61.3
对比例5 88.5
对比例6 82.7
对比例7 69.3
测试二、低温DCR测试
将制备得到的锂离子电池均分别进行下述测试：
在1C恒流恒压充电至4.3V，截止电流0.05C，再以1C容量放电30min，调至50％SOC，之后在-20℃下放置2h，执行脉冲程序，0.3C恒流放电10s，静置1min，0.3C恒流充电10s，静置5min，完成测试。DCR＝(脉冲放电前电压-脉冲放电后电压)/放电电流*100％，所得记录结果见表3。
表3 实施例1-32以及对比例1-7的锂离子电池低温DCR
组别 -20℃DCR(mΩ)
实施例1 280.1
实施例2 267.4
实施例3 251.2
实施例4 238.5
实施例5 279.8
实施例6 309.2
实施例7 271.4
实施例8 260.6
实施例9 246.1
实施例10 249.1
实施例11 262.7
实施例12 296.0
实施例13 257.8
实施例14 243.6
实施例15 231.7
实施例16 219.9
实施例17 208.2
实施例18 204.1
实施例19 267.7
实施例20 256.9
实施例21 272.1
实施例22 258.3
实施例23 264.1
实施例24 259.1
实施例25 252.9
实施例26 245.6
实施例27 241.9
实施例28 246.2
实施例29 251.9
实施例30 245.3
实施例31 241.0
实施例32 244.9
对比例1 359.7
对比例2 298.1
对比例3 321.3
对比例4 329.8
对比例5 278.2
对比例6 271.9
对比例7 306.1
实验三、低温放电容量测试
将制备得到的锂离子电池均分别进行下述测试：
以1C恒流恒压充电至4.3V，截止电流0.05C，静置5min，之后将电芯1C放电至3.0V,静置5min，将该放电容量记为C 0；将电芯以1C恒流恒压充电至4.3V,截止电流为0.05C,静置5min；将电芯置于-20℃温箱中，静置120min(确保电芯温度达到-20℃)；之后将电芯1C放电至3.0V,静置5min，将放电容量记为C 1；容量保持率＝C 1/C 0*100％，所得记录结果见表4。
表4 实施例1-32以及对比例1-7的锂离子电池低温放电容量
组别 低温放电容量保持率(％)
实施例1 52.4
实施例2 57.5
实施例3 63.8
实施例4 66.9
实施例5 63.2
实施例6 57.1
实施例7 60.1
实施例8 62.4
实施例9 64.4
实施例10 65.1
实施例11 61.8
实施例12 58.2
实施例13 58.1
实施例14 62.6
实施例15 68.1
实施例16 71.2
实施例17 73.7
实施例18 74.9
实施例19 52.7
实施例20 54.9
实施例21 53.3
实施例22 57.2
实施例23 58.0
实施例24 56.8
实施例25 55.1
实施例26 65.1
实施例27 65.8
实施例28 63.2
实施例29 61.1
实施例30 63.9
实施例31 62.0
实施例32 63.6
对比例1 37.2
对比例2 54.9
对比例3 41.5
对比例4 44.2
对比例5 58.8
对比例6 59.5
对比例7 48.2
实验四、低温析锂测试
将制备得到的锂离子电池均分别进行下述测试：
①以1C放电至3.0V,静置5min；
②将电芯置于-10℃温度下，静置120min；之后以k C恒流恒压充电至4.3V,截止电流为0.05C,静置5min；再以1C放电至3.0V,静置5min；
③重复步骤②，循环5次；
④再以k C恒流恒压充电至4.3V,截止电流为0.05C，静置5min；之后将电芯置于25℃下，静置2h，再以1C恒流恒压充电至4.3V,截止电流为0.05C；
其中k＝0.25、0.45、0.65、0.85；
⑤将上述电芯在空气中水含量较低的干燥房(露点低于-35℃)中拆解，对所得负极片拍照，记录析锂部分面积，完成测试。
析锂面积百分比＝析锂部分面积/负极片总面积*100％，所得记录结果见表5。
表5 实施例1-32以及对比例1-7的锂离子电池低温析锂面积比
Figure PCTCN2020084960-appb-000015
实验五、高温存储厚度膨胀率测试
将制备得到的锂离子电池均分别进行下述测试：
分别取5支，在常温下以1C倍率恒流充电至电压4.3V，进一步在4.3V恒压充电至电流低于0.05C，使其处于4.3V满充状态。测试存储前的满充电池厚度并记为D 0；再将满充状态的电池置于85℃烘箱中，3d后，将电池取出，立即测试其存储后的厚度并记为D 1；根据公式ε＝(D 1-D 0)/D 0×100％计算电池存储前后的厚度膨胀率，取5组实验数据平均值，记为ε，所得结果见表6。
表6 实施例1-32以及对比例1-7的锂离子电池高温存储厚度膨胀率
组别 高温存储厚度膨胀率ε(％)
实施例1 40.1
实施例2 35.5
实施例3 32.2
实施例4 29.5
实施例5 27.7
实施例6 25.9
实施例7 29.9
实施例8 30.1
实施例9 30.1
实施例10 28.7
实施例11 29.6
实施例12 31.5
实施例13 28.7
实施例14 28.6
实施例15 35.9
实施例16 44.1
实施例17 53.9
实施例18 60.9
实施例19 33.2
实施例20 32.1
实施例21 30.4
实施例22 31.2
实施例23 32.9
实施例24 33.1
实施例25 30.5
实施例26 29.4
实施例27 28.6
实施例28 27.9
实施例29 29.7
实施例30 32.7
实施例31 34.6
实施例32 32.8
对比例1 51.7
对比例2 27.8
对比例3 45.2
对比例4 52.2
对比例5 28.1
对比例6 29.4
对比例7 46.2
结合表1-6中的数据可以得出以下结论：
1)从对比例1和对比例2的实验结果可以看出，仅添加乙二醇环硫酸酯可以改善电芯循环性能，降低电芯产气，改善电芯低温阻抗，改善电芯低温放电性能及低温充电析锂窗口，这是因为其可以在电极表面形成可以抑制电极-电解液副反应且有利于锂离子通透的SEI膜，改善电芯循环性能，抑制电芯产气。从实施例1-6可以看出，当其质量百分含量低于2％时，随着其浓度增加，对电芯各项性能的改善与其含量增加正相关，而当其质量百分含量高于2％时，含量继续增加甚至会引起电芯性能恶化。这是因为当其浓度较低时，成膜能力不足，导致对电芯性能改善有限，随着其浓度的增加，形成更有利于锂离子通透及抑制电极-电解液副反应的SEI膜，对电芯循环改善效果增强，而当含量高于2.0％时，成膜太厚导致锂离子通透性下降，阻抗增加，循环性能变差。综合上述情况，乙二醇环硫酸酯的质量百分含量为0.1％-4.0％，其优选的质量百分含量为0.5％-3.0％。
2)从对比例1和对比例3可以看出，仅添加二氟草酸硼酸锂可以稍微改善电芯的循环性能，但对电芯其它性能的改善较为有限，说明仅依靠二氟草酸硼酸锂成膜并不能有效抑制极片与电解液溶剂的副反应。从对比例5可以看出，当二氟草酸硼酸锂与乙二醇环硫酸酯联合使用时，相比仅添加乙二醇环硫酸酯可以进一步改善电芯循环性能，低温DCR，低温放电容量和低温充电析锂窗口，但对产气性能影响不大。这是因为乙二醇环硫酸酯可以和二氟草酸硼酸锂共同成膜，形成相比仅添加乙二醇环硫酸酯有机组分含量更高，更有利于锂离子通透的SEI膜，改善电芯性能，但形成的SEI膜致密程度与仅添加乙二醇环硫酸酯相当，因此，并不能进一步改善电芯产气性能。从对比例2和对比例3，实施例4和实施例7～12可以看出，在乙二醇环硫酸酯存在下，当二氟草酸硼酸锂浓度较低时，随着浓度增加,对电芯循环性能改善效果增加，当浓度进一步增加时，会导致电芯低温阻抗增加，循环性能下降。这是因为当二氟草酸硼酸锂浓度较低时，成膜能力不足，导致对电芯性能改善有限，随着其浓度的增加，形成更有利于锂离子通透及抑制电极-电解液副反应的SEI膜，对电芯循环改善效果增强，而当含量过高时，成膜太厚导致锂离子通透性下降，阻抗增加，循环性能下降，综合上述情况，二氟草酸硼酸锂的优选质量百分含量为0.1～2.0％。
3)从对比例1和对比例4可以看出，单一的三甲基氟硅烷不影响电芯的循环性能，一定程度的改善电池的低温性能。从对比例2和对比例6可以看出，三甲基氟硅烷可以在乙二醇环硫酸酯基础上进一步改善电芯的低温性能。从实施例4和实施例13～18可以看出，随着三甲基氟硅烷含量的上升，可以更近一步的提升电池的低温性能，且对循环性能影响不大。然而，当三甲基氟硅烷高于1％时，随着含量进一步增加，随着含量增加会加剧电芯产气，这是因为当其浓度较低时，三甲基氟硅烷可以溶解在电解液中，当浓度过高时，沸点仅有16℃的三甲基氟硅烷会从电解液中挥发出来，造成产气增加，浓度过高容易带来安全隐患，综合来看，三甲基氟硅烷优选的质量百分含量为0.3％～2.0％。
4)从对比例1～7和实施例4可以看出，乙二醇环硫酸酯、二氟草酸硼酸锂和三甲基氟硅烷联合使用，可以更好地改善电芯产气、循环、低温阻抗、低温放电以及低温充电析锂窗口，这是因为乙二醇环硫酸酯在电极表面成膜，当与二氟草酸硼酸锂联合使用时，形成了相比仅添加乙二醇环硫酸酯有机组分含量更高，更有利于锂离子通透的SEI膜，增加锂离子在电极与电解液界面的通透性，三甲基氟硅烷虽然不参与电极表面SEI膜的形成，但其可以改善电解液的低温电导率。通过乙二醇环硫酸酯、二氟草酸硼酸锂和三甲基氟硅烷的协同作用，改善了锂离子在正负极间的传导，使得电芯低温阻抗，低温充电析锂窗口和低温放电性能明显提升，且电池拥有较好的循环性能。
5)从对比例7，实施例4和实施例19～24可以看出，所述环状硫酸酯可在一定程度上改善电芯的产气，循环以及低温性能，这是因为拥有环状硫酸酯结构的化合物可以在电极表面成膜，形成有利于锂离子通透且能抑制电极-电解液副反应的SEI膜，改善电芯性能。
6)从对比例5，实施例4和实施例25～31可以看出，所述氟代硅烷中甲基三氟硅烷和乙基三氟硅烷相对于其他种类的氟代硅烷会加剧电芯产气，其它硅烷对电芯产气性能影响不大，这是因为甲基三氟硅烷和乙基三氟硅烷沸点更低，更容易从电解液中挥发出来，造成产气量增加。所述氟代硅烷对电芯循环性能无明显影响，可以一定程度的改善电芯低温DCR，低温放电性能，低温充电析锂窗口，这是因为氟硅烷结构可以和锂离子发生某种作用，使得电解液低温电导率降低，电芯低温性能得以改善。
本申请虽然以较佳实施例公开如上，但并不是用来限定权利要求，任何本领域技术人员在不脱离本申请构思的前提下，都可以做出若干可能的变动和修改，因此本申请的保护范围应当以本申请权利要求所界定的范围为准。

Claims (12)

  1. 一种电解液，包括有机溶剂，锂盐和添加剂，其中，所述添加剂包括环状硫酸酯、二氟草酸硼酸锂和氟代硅烷。
  2. 根据权利要求1所述的电解液，其中，所述环状硫酸酯选自结构式为式I所示化合物中的至少一种，
    Figure PCTCN2020084960-appb-100001
    其中，R选自C 2-3直链亚烷基、被取代基A取代的C 2-3直链亚烷基、C 2-3直链亚烯基及被取代基A取代的C 2-3直链亚烯基中的一种；
    所述取代基A选自卤素原子、烷氧基、羧基、磺酸基、碳原子数为1-20的烷基、碳原子数为1-20的卤代烷基、碳原子数为2-20的不饱和烃基及碳原子数为2-20的卤代不饱和烃基中的至少一种。
  3. 根据权利要求3所述的电解液，其中，所述环状硫酸酯选自以下化合物中的至少一种：
    Figure PCTCN2020084960-appb-100002
    Figure PCTCN2020084960-appb-100003
  4. 根据权利要求1所述的二次电池电解液，其中，所述氟代硅烷选自结构式为式II所示化合物中的至少一种，
    Figure PCTCN2020084960-appb-100004
    其中，R 1、R 2、R 3、R 4各自独立地选自氢、卤素、C 1-10烷基、被取代基B取代的C 1-10烷基、C 1-10烷氧基、被取代基B取代的C 1-10烷氧基、C 2-10烯基、被取代基B取代的C 2-10烯基、C 2-10炔基、被取代基B取代的C 2-10炔基、含硅基团中的一种；且R 1、R 2、R 3、R 4中至少一个为氟原子取代基；
    所述取代基B选自卤素、烷氧基、羧基、磺酸基、碳原子数为1-20的烷基、碳原子数为1-20的卤代烷基、碳原子数为2-20的不饱和烃基及碳原子数为2-20的卤代不饱和烃基中的至少一种。
  5. 根据权利要求4所述的电解液，其中，所述氟代硅烷选自以下化合物中的至少一种：
    Figure PCTCN2020084960-appb-100005
  6. 根据权利要求1所述的电解液，其中，所述二氟草酸硼酸锂在所述电解液中的质量百分含量为0.1％-3.0％；优选为0.1％-2.0％。
  7. 根据权利要求1所述的电解液，其中，所述环状硫酸酯在所述电解液中的质量百分含量为0.1％-4.0％；优选为0.5％-3.0％。
  8. 根据权利要求1所述的电解液，其中，所述氟代硅烷在所述电解液中的质量百分含量为0.1％-4.0％；优选为0.3％-2.0％。
  9. 根据权利要求1-8任一项所述的电解液，其中，所述添加剂还包括碳酸亚乙烯酯、1,3-丙烷磺酸内酯、1-丙烯-1,3-磺酸内酯、甲烷二磺酸亚甲酯、碳酸乙烯亚乙酯、三(三甲基硅基)磷酸酯、三(三甲基硅基)亚磷酸酯、己二腈及反丁烯二腈中的至少一种。
  10. 根据权利要求1所述的电解液，其中，所述添加剂还包括锂盐添加剂，所述锂盐添加剂包括四氟硼酸锂、二氟磷酸锂及双氟磺酰亚胺锂中的至少一种。
  11. 根据权利要求10所述的电解液，其中，所述锂盐添加剂在所述电解液中的质量百分含量低于3％。
  12. 一种电化学装置，包括正极片、负极片、隔膜和权利要求1-11任一项所述的电解液。
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CN110854433A (zh) * 2019-11-15 2020-02-28 欣旺达电动汽车电池有限公司 一种电解液和电化学装置
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CN112216867B (zh) * 2020-09-29 2023-02-07 中国科学院成都有机化学有限公司 电解液添加剂、锂离子高压电解液、锂离子电池
CN113948770B (zh) * 2021-10-12 2024-01-30 远景动力技术(江苏)有限公司 改善电池高温存储特性的电解液以及锂离子电池
CN115588779B (zh) * 2022-11-11 2023-11-28 广州天赐高新材料股份有限公司 高温型非水电解液和二次电池
CN116315086A (zh) * 2023-01-04 2023-06-23 珠海冠宇电池股份有限公司 电解液和锂离子电池
CN117712488B (zh) * 2024-02-04 2024-05-24 深圳海辰储能科技有限公司 电解液、包含该电解液的二次电池、电池包和用电设备
CN118040059B (zh) * 2024-04-12 2024-07-02 瑞浦兰钧能源股份有限公司 一种电解液及其应用

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014103066A (ja) * 2012-11-22 2014-06-05 Tdk Corp リチウムイオン二次電池用非水電解液及びリチウムイオン二次電池
CN105406126A (zh) * 2014-09-05 2016-03-16 Sk新技术株式会社 锂二次电池电解液及包含其的锂二次电池
CN108933294A (zh) * 2017-05-26 2018-12-04 宁德时代新能源科技股份有限公司 锂离子电池及其电解液
CN110112464A (zh) * 2019-04-17 2019-08-09 欣旺达电动汽车电池有限公司 一种含有三甲基氟硅烷的锂离子二次电池电解液
CN110854433A (zh) * 2019-11-15 2020-02-28 欣旺达电动汽车电池有限公司 一种电解液和电化学装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014103066A (ja) * 2012-11-22 2014-06-05 Tdk Corp リチウムイオン二次電池用非水電解液及びリチウムイオン二次電池
CN105406126A (zh) * 2014-09-05 2016-03-16 Sk新技术株式会社 锂二次电池电解液及包含其的锂二次电池
CN108933294A (zh) * 2017-05-26 2018-12-04 宁德时代新能源科技股份有限公司 锂离子电池及其电解液
CN110112464A (zh) * 2019-04-17 2019-08-09 欣旺达电动汽车电池有限公司 一种含有三甲基氟硅烷的锂离子二次电池电解液
CN110854433A (zh) * 2019-11-15 2020-02-28 欣旺达电动汽车电池有限公司 一种电解液和电化学装置

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