WO2023193230A1 - 电解液、二次电池、电池模块、电池包和用电装置 - Google Patents

电解液、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023193230A1
WO2023193230A1 PCT/CN2022/085783 CN2022085783W WO2023193230A1 WO 2023193230 A1 WO2023193230 A1 WO 2023193230A1 CN 2022085783 W CN2022085783 W CN 2022085783W WO 2023193230 A1 WO2023193230 A1 WO 2023193230A1
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partially halogenated
battery
electrolyte
halogenated saturated
electrolyte solution
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PCT/CN2022/085783
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English (en)
French (fr)
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张明
吴启凡
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宁德时代新能源科技股份有限公司
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Priority to CN202280030803.4A priority Critical patent/CN117223141A/zh
Priority to JP2023547841A priority patent/JP2024516058A/ja
Priority to KR1020237026587A priority patent/KR20230145336A/ko
Priority to EP22922548.7A priority patent/EP4283745A4/en
Priority to PCT/CN2022/085783 priority patent/WO2023193230A1/zh
Priority to US18/449,311 priority patent/US20240021864A1/en
Publication of WO2023193230A1 publication Critical patent/WO2023193230A1/zh

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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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/045—Cells or batteries with folded plate-like electrodes
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • 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
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • 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
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • 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 batteries, specifically to an electrolyte, a secondary battery, a battery module, a battery pack and an electrical device.
  • Secondary batteries have the characteristics of high capacity and long life, so they are widely used in electronic equipment, such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools etc.
  • electronic equipment such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools etc.
  • higher requirements have been placed on the performance of secondary batteries.
  • the materials in the secondary battery such as the electrolyte, are usually optimized and improved.
  • electrolyte As a transmission medium for metal ions in secondary batteries, electrolyte has a non-negligible impact on the performance of secondary batteries.
  • This application was made in view of the above-mentioned problems, and its purpose is to provide an electrolyte solution, a secondary battery, a battery module, a battery pack, and an electrical device.
  • a first aspect of the present application provides an electrolyte for a secondary battery, the electrolyte comprising C2-C4 olefins substituted by halogen atoms and/or partially halogenated saturated polyolefins.
  • the electrolyte solution of the embodiment of the present application is provided with C2-C4 olefins substituted by halogen atoms and/or partially halogenated saturated polyolefins.
  • the above substances can undergo electrochemical reduction reactions on the surface of the negative active material to generate a halogen-containing solid state.
  • Electrolyte interface membrane The generated halogen-containing solid electrolyte interface film has, on the one hand, a lower interface resistance, allowing the secondary battery to have better low-temperature characteristics; on the other hand, it can reduce the risk of direct contact between the electrolyte and the negative active material, reducing electrolysis Reduce the risk of reduction reaction in the liquid, thereby extending the life of the secondary battery.
  • an electrochemical reduction reaction can occur on the surface of the negative electrode active material to generate a solid electrolyte interface film; and the partially halogenated saturated polyolefin has a certain viscosity, which can improve the performance of the negative electrode.
  • the binding force between the active material and the solid electrolyte interface film can improve the reliability of forming the solid electrolyte interface film during the charging and discharging process of the secondary battery, thereby improving the electrochemical performance of the secondary battery; thereby improving both low-temperature performance and service life.
  • the C2-C4 olefin substituted by a halogen atom includes one or more compounds represented by Formula I,
  • R 11 to R 13 are each independently selected from a hydrogen atom, a halogen atom or a C1-C2 alkyl group substituted or unsubstituted by a halogen atom, and the sum of the number of carbon atoms in R 11 to R 13 is 0 , 1 or 2; optionally, the halogen atom includes a fluorine atom or a chlorine atom;
  • R 11 to R 13 are each independently selected from a hydrogen atom, a fluorine atom or -CF 3 .
  • the C2-C4 olefin substituted with halogen atoms in the embodiments of the present application can more easily control its solubility in the electrolyte, and is conducive to the electrochemical reaction with the negative active material.
  • the C2-C4 olefin substituted by a halogen atom includes one or more compounds represented by Formula I-1 to Formula I-5,
  • the mass percentage a of C2-C4 olefins substituted by halogen atoms satisfies 0.05% ⁇ a ⁇ 10%, optionally, 0.1% ⁇ a ⁇ 1%.
  • the C2-C4 olefins substituted by halogen atoms can be stably dissolved in the electrolyte and can be active in the negative electrode.
  • a dense protective film is formed on the surface of the material, which can protect the negative electrode plate well.
  • the partially halogenated saturated polyolefin includes one or more of the structural units represented by Formula II, and the partially halogenated saturated polyolefin includes at least one partially halogenated olefin structural unit,
  • R 21 to R 24 are each independently selected from a hydrogen atom, a halogen atom, or a linear or branched C1 to C8 alkyl group substituted or unsubstituted by a halogen atom; optionally, the halogen atom includes a fluorine atom or a chlorine atom. atoms; further optionally, R 21 to R 24 are each independently selected from hydrogen atoms, fluorine atoms or -CF 3 ; the total degree of polymerization m of the partially halogenated saturated polyolefin satisfies 1 ⁇ m ⁇ 220, and m is a positive integer ;Optionally, 4 ⁇ m ⁇ 220.
  • the molecular weight of the partially halogenated saturated polyolefin in the embodiments of the present application is relatively small, and its solubility with other substances in the electrolyte is relatively high, which is beneficial to controlling the use of the partially halogenated saturated polyolefin in the negative active material. Electrochemical reduction reaction on the surface.
  • the partially halogenated saturated polyolefin includes one or more of the structural units represented by Formula II-1 to Formula II-5, and the partially halogenated saturated polyolefin includes at least one partially fluorinated olefin Structural units,
  • the weight average molecular weight of the partially halogenated saturated polyolefin is less than or equal to 10,000 Da; optionally, the weight average molecular weight of the partially halogenated saturated polyolefin is 200 Da to 10,000 Da.
  • the mass percentage b of the partially halogenated saturated polyolefin satisfies 0.05% ⁇ a ⁇ 10%, optionally, 0.1% ⁇ a ⁇ 1%.
  • the weight average molecular weight of the partially halogenated saturated polyolefin in the embodiments of the present application is relatively small, and it is easier to dissolve in the electrolyte, thereby facilitating the electrochemical reaction on the surface of the negative active material to form a solid electrolyte interface. membrane.
  • a second aspect of the application also provides a secondary battery, including a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • the isolation film is arranged between the positive electrode piece and the negative electrode piece.
  • the electrolyte solution adopts the electrolyte solution of any embodiment of the first aspect of the application; optionally, the positive electrode plate includes lithium element and/or sodium element.
  • a third aspect of the present application also provides a battery module, including the secondary battery according to the embodiment of the second aspect of the present application.
  • a fourth aspect of the application also provides a battery pack, including the battery module according to the embodiment of the third aspect of the application.
  • a fifth aspect of the present application also provides an electrical device, including a secondary battery as in the second embodiment of the present application, a battery module as in the third embodiment of the present application, or a battery as in the fourth embodiment of the present application. Bag.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an electrical device according to an embodiment of the present application.
  • Secondary battery 11. Outer packaging; 111. Top cover assembly; 112. Housing; 12. Electrode assembly; 10. Battery module; 20. Battery pack; 21. Upper box; 22. Lower box; 30 , electrical equipment.
  • Ranges disclosed in this application are defined in terms of lower and upper limits.
  • a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the present application proposes an electrolyte solution for a secondary battery, which electrolyte solution includes C2-C4 olefins substituted by halogen atoms and/or partially halogenated saturated polyolefins.
  • the electrolyte solution may include C2-C4 olefins substituted by halogen atoms; the electrolyte solution may include partially halogenated saturated polyolefins; or the electrolyte solution may include C2-C4 olefins substituted by halogen atoms. C4 olefins and partially halogenated saturated polyolefins.
  • C2-C4 olefins substituted by halogen atoms means that one hydrogen atom or two or more hydrogen atoms in the C2-C4 olefins are replaced by halogen atoms.
  • different hydrogen atoms can be replaced by different halogen atoms, for example, one hydrogen atom is replaced by a fluorine atom F, and another hydrogen atom is replaced by a bromine atom Br.
  • C2-C4 olefin refers to one or more of ethylene, propylene and butylene.
  • the halogen atom can be a fluorine atom, a chlorine atom, etc.
  • the C2-C4 olefin substituted by a halogen atom may be vinyl fluoride, 1,1-difluoroethylene, 1,2-difluoroethylene, perfluoroethylene, fluoropropylene, 1,1-difluoropropene, 1 ,2,3-trifluoropropene, fluorobutene, vinyl chloride, 1,1-dichloroethylene, 1,2-dichloroethylene, perchlorethylene, chloropropene, 1,1-dichloropropene, 1,2 , one or more of 3-trichloropropene and chloroprene. It should be noted that the above is only an illustrative description and is not intended to limit the scope of C2-C4 olefins substituted by halogen atoms.
  • C2-C4 olefins substituted by halogen atoms are in a gaseous state.
  • an electrochemical reduction reaction can occur on the surface of the negative electrode active material to form a solid electrolyte interphase (SEI); and by halogen
  • SEI solid electrolyte interphase
  • halogen As small molecular substances, atomically substituted C2-C4 olefins have higher solubility in the electrolyte and are more easily dispersed evenly inside the electrolyte, thereby improving the thickness uniformity of the solid electrolyte interface film formed and ensuring solid state Uniform performance of electrolyte interface membranes.
  • Partially halogenated saturated polyolefin means that it contains halogen atoms in the repeating structural units, and the polymer still has hydrogen atoms.
  • the repeating structural units of the partially halogenated saturated polyolefin are vinyl fluoride, 1,1-difluoroethylene, 1,2-difluoroethylene, fluoropropylene, 1,1-difluoropropylene, 1,2,3 -Trifluoropropylene, fluorobutene, vinyl chloride, 1,1-dichloroethylene, 1,2-dichloroethylene, perchlorethylene, chloropropylene, 1,1-dichloropropene, 1,2,3-tris One or more of chloropropene and chloroprene.
  • Partially halogenated saturated polyolefin means that the repeating structural units contain halogen atoms and the polymer contains hydrogen atoms.
  • the repeating structural units of the partially halogenated saturated polyolefin are vinyl fluoride, 1,1-difluoroethylene, 1,2-difluoroethylene, fluoropropylene, 1,1-difluoropropylene, 1,2,3 -Trifluoropropylene, fluorobutene, vinyl chloride, 1,1-dichloroethylene, 1,2-dichloroethylene, perchlorethylene, chloropropylene, 1,1-dichloropropene, 1,2,3-tris One or more of chloropropene and chloroprene.
  • the electrolyte in the embodiment of the present application is provided with C2-C4 olefins substituted by halogen atoms and/or partially halogenated saturated polyolefins.
  • the above substances can undergo electrochemical reduction reactions on the surface of the negative active material to generate a halogen-containing solid electrolyte interface film.
  • the generated halogen-containing solid electrolyte interface film has, on the one hand, a lower interface resistance, allowing the secondary battery to have better low-temperature characteristics; on the other hand, it can reduce the risk of direct contact between the electrolyte and the negative active material, reducing electrolysis Reduce the risk of reduction reaction in the liquid, thereby extending the life of the secondary battery.
  • the C2-C4 olefins substituted by halogen atoms include one or more compounds represented by Formula I,
  • R 11 to R 13 are each independently selected from a hydrogen atom, a halogen atom or a C1-C2 alkyl group substituted or unsubstituted by a halogen atom, and the sum of the number of carbon atoms in R 11 to R 13 is 0 , 1 or 2.
  • R 11 to R 13 are each independently selected from a hydrogen atom, a halogen atom or -CF 3 .
  • the C2-C4 olefin substituted by halogen atoms in the embodiments of the present application is easier to control its solubility in the electrolyte, and is conducive to the electrochemical reaction with the negative active material.
  • the halogen atom includes a fluorine atom or a chlorine atom; further optionally, the halogen atom includes a fluorine atom.
  • the potential of fluorine atoms and chlorine atoms is relatively high, especially the potential of fluorine atoms is relatively high, which is conducive to participating in electrochemical reactions to form an SEI film.
  • C2-C4 olefins substituted with fluorine atoms are more conducive to participating in electrochemical reactions to form SEI films.
  • the C2-C4 olefins substituted by halogen atoms include one or more of the compounds represented by Formula I-1 to Formula I-5,
  • the mass percentage a of C2-C4 olefins substituted by halogen atoms satisfies 0.05% ⁇ a ⁇ 10%.
  • C2-C4 olefins substituted by halogen atoms are gaseous at ambient temperature, such as 25°C, when the mass percentage a of the C2-C4 olefins substituted by halogen atoms is greater than 10%, the C2-C4 olefins substituted by halogen atoms will If the content in the electrolyte is too high and may exceed its own solubility, some of the C2-C4 olefins substituted by halogen atoms will volatilize. The volatilization process will affect the storage stability of the electrolyte.
  • the inventor set the mass percentage a of C2-C4 olefins substituted by halogen atoms to 0.05% ⁇ a ⁇ 10%, optionally, 0.1% ⁇ a ⁇ 1%.
  • C2-C4 olefins substituted by halogen atoms within this content range can be stably dissolved in the electrolyte and can form a dense protective film on the surface of the negative electrode active material, thus providing good protection for the negative electrode plate.
  • the partially halogenated saturated polyolefin includes one or more of the structural units represented by Formula II, and the partially halogenated saturated polyolefin includes at least one partially halogenated olefin structural unit,
  • R 21 to R 24 are each independently selected from a hydrogen atom, a halogen atom, or a C1 to C8 linear or branched alkyl group substituted or unsubstituted by a halogen atom; further optionally, each of R 21 to R 24 Independently selected from hydrogen atoms, halogen atoms or -CF 3 ; the total degree of polymerization m of the partially halogenated saturated polyolefin satisfies 1 ⁇ m ⁇ 220, and m is a positive integer; optionally, 4 ⁇ m ⁇ 220.
  • the molecular weight of this type of partially halogenated saturated polyolefin is relatively small, and its solubility with other substances in the electrolyte is relatively high, which is beneficial to controlling the electrochemical reduction reaction of the partially halogenated saturated polyolefin on the surface of the negative active material.
  • the halogen atom includes a fluorine atom or a chlorine atom; further optionally, the halogen atom includes a fluorine atom.
  • the potential of fluorine atoms and chlorine atoms is relatively high, especially the potential of fluorine atoms is relatively high, which is conducive to participating in electrochemical reactions to form an SEI film. In other words, partially fluorinated saturated polyolefins are more conducive to participating in electrochemical reactions to form SEI films.
  • the partially halogenated saturated polyolefin includes one or more structural units represented by Formula II-1 to Formula II-5, and the partially halogenated saturated polyolefin includes at least one partially fluorinated olefin structural unit,
  • the partially halogenated saturated polyolefin may be the following polymer
  • n and n are both positive integers.
  • the weight average molecular weight of the partially halogenated saturated polyolefin is less than or equal to 10,000 Da; further optionally, the weight average molecular weight of the partially halogenated saturated polyolefin is 200 Da to 10,000 Da.
  • the weight average molecular weight of the partially halogenated saturated polyolefin is relatively small, and it is easier to dissolve in the electrolyte, thereby facilitating the electrochemical reaction to form an SEI film on the surface of the negative active material.
  • the mass percentage b of the partially halogenated saturated polyolefin satisfies 0.05% ⁇ a ⁇ 10%, optionally, 0.1% ⁇ a ⁇ 1%.
  • the partially halogenated saturated polyolefin in the above content range can, on the one hand, form a dense and stable SEI film on the surface of the negative active material; on the other hand, it can maintain a certain viscosity and the viscosity is relatively low, thereby reducing its impact on metals.
  • the adverse effects of ion migration can ensure the transmission characteristics of metal ions in the electrolyte, thereby ensuring the electrochemical performance of secondary batteries.
  • the electrolyte in the embodiment of the present application plays a role in conducting metal ions between the positive electrode piece and the negative electrode piece, and is in a liquid state.
  • the electrolyte solution may also include electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, and trifluoromethanesulfonic acid.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.
  • Ester fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, At least one of 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may also include additives.
  • additives may include other negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • this application proposes a secondary battery.
  • the secondary battery includes a positive electrode piece, a negative electrode piece, a separator and an electrolyte.
  • the isolation film is disposed between the positive electrode piece and the negative electrode piece to separate the positive electrode piece and the negative electrode piece.
  • the electrolyte solution of the first aspect of the present application can be used.
  • the electrolyte can form a stable SEI film on the surface of the negative electrode material.
  • the SEI film can effectively protect the negative electrode active material and ensure the structural stability of the negative electrode active material, thereby improving the low-temperature performance of the secondary battery. and service life.
  • the positive electrode piece includes lithium element and/or sodium element.
  • lithium ions and/or sodium ions as active ions, can migrate stably between the positive electrode piece and the negative electrode piece, thereby ensuring the electrochemical performance of the secondary battery.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon.
  • At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl At least one of acrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • auxiliaries such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • a separator film is further included in the secondary battery.
  • This application has no special restrictions on the type of isolation membrane, and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece, and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer casing of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape.
  • FIGS. 1 and 2 illustrate a square-structured secondary battery 1 as an example.
  • the secondary battery 1 includes an outer packaging 11 .
  • the outer package 11 includes a top cover assembly 111 and a housing 112 .
  • the positive electrode piece, the negative electrode piece and the separator constitute the electrode assembly 12 and are accommodated in the casing 112.
  • the casing 112 also contains electrolyte.
  • the positive or negative pole piece contains the tabs.
  • active ions are inserted and detached back and forth between the positive electrode piece and the negative electrode piece.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • the secondary battery 1 may be a wound or laminated battery, such as a lithium-ion battery or a sodium-ion battery, but is not limited thereto.
  • the housing 112 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity.
  • the housing 112 has an opening communicating with the accommodation cavity, and the top cover assembly 111 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 12 through a winding process or a lamination process.
  • the electrode assembly 12 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 12 .
  • the number of electrode assemblies 12 contained in the secondary battery 1 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery 1 may be assembled into a battery.
  • the battery may be a battery module or a battery included.
  • the number of secondary batteries 1 contained in the battery module may be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 10 as an example.
  • a plurality of secondary batteries 1 may be arranged in sequence along the length direction of the battery module 10 .
  • the plurality of secondary batteries 1 can be fixed by fasteners.
  • the battery module 10 may further include a housing having an accommodation space in which a plurality of secondary batteries 1 are accommodated.
  • the above-mentioned battery modules 10 can also be assembled into a battery pack.
  • the number of battery modules 10 contained in the battery pack can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack can also be directly composed of multiple secondary batteries 1 .
  • the battery pack 20 may include a battery box and a plurality of battery modules 10 disposed in the battery box.
  • the battery box includes an upper box 21 and a lower box 22 .
  • the upper box 21 can be covered with the lower box 22 and form a closed space for accommodating the battery module 10 .
  • Multiple battery modules 10 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 6 shows an electrical device 30 as an example.
  • the electric device 30 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack or battery module may be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • An aluminum foil with a thickness of 8 ⁇ m was used as the positive electrode current collector.
  • NMP N-methylpyrrolidone
  • Preparation of the negative electrode sheet Combine the negative active material graphite, conductive carbon black, thickener sodium carboxymethylcellulose (CMC), and binder styrene-butadiene rubber emulsion (SBR) according to the weight of 96.5:1.0:1.0:1.5 Mix thoroughly with an appropriate amount of deionized water to form a uniform negative electrode slurry; apply the negative electrode slurry on the negative electrode current collector, and undergo drying and other processes to obtain a negative electrode piece.
  • CMC thickener sodium carboxymethylcellulose
  • SBR binder styrene-butadiene rubber emulsion
  • the positive electrode piece, isolation film (PP/PE/PP composite film), and negative electrode piece are stacked in sequence, then rolled into a battery core and packed into a packaging shell.
  • the above electrolyte is injected into the battery core, and then sealed , standing, hot and cold pressing, formation and other processes to obtain a secondary battery.
  • Capacity retention rate (%) of the secondary battery after 1000 cycles (discharge capacity of the 1000th cycle/discharge capacity of the first cycle) ⁇ 100%.
  • SOC state of charge
  • the low-temperature DCR of the secondary battery (U1-U2)/I, where I represents the current.
  • Example 17 and Example 18 It can be seen from Example 17 and Example 18 that using a variety of partially halogenated saturated polyolefins can also improve the cycle performance and low temperature performance of secondary batteries.
  • Example 12 Example 19 to Example 22 that when the weight average molecular weight of the partially halogenated saturated polyolefin is less than 10,000 Da, especially between 200 Da and 10,000 Da, the capacity retention rate of the secondary battery is relatively high, and the DCR Relatively small.
  • Example 23 uses both C2-C4 olefins substituted by halogen atoms and partially halogenated saturated polyolefins. All three can significantly improve the performance of the secondary battery.

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Abstract

一种电解液、二次电池、电池包和用电装置。电解液包括经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃。经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃可以在负极活性材料的表面发生电化学还原反应生成固态电解质界面膜；通过在电解液中添加经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃，能够兼顾改善二次电池的低温性能及使用寿命。

Description

电解液、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电池领域，具体涉及一种电解液、二次电池、电池模块、电池包和用电装置。
背景技术
二次电池具有容量高、寿命长等特性，因此广泛应用于电子设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。由于二次电池取得了极大的进展，因此对二次电池的性能提出了更高的要求。为了提高二次电池的性能，通常对二次电池内的材料例如电解液进行优化改善。电解液作为二次电池中金属离子的传输介质，对二次电池的性能具有不可忽略的影响。
然而，目前改进后的电解液在应用于二次电池时，二次电池在使用过程中仍无法同时兼顾改善低温性能及使用寿命。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种电解液、二次电池、电池模块、电池包和用电装置。
本申请的第一方面提供了一种用于二次电池的电解液，电解液包括经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃。
由此，本申请实施例的电解液通过设置经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃，上述物质可以在负极活性材料的表面发生 电化学还原反应生成含卤素的固态电解质界面膜。所生成的含卤素固态电解质界面膜，一方面具有较低的界面阻抗，使得二次电池具有较好的低温特性；另一方面，可以降低电解液与负极活性材料的直接接触的风险，降低电解液发生还原反应的风险，从而提升二次电池的寿命。
本申请实施例通过在电解液中添加部分卤化的饱和聚烯烃，可以在负极活性材料的表面发生电化学还原反应生成固态电解质界面膜；并且部分卤化的饱和聚烯烃具有一定的粘性，可以提高负极活性材料和固态电解质界面膜的结合力，从而在二次电池充放电过程中能够提高形成固态电解质界面膜的可靠性，进而提高二次电池的电化学性能；从而能够兼顾改善低温性能及使用寿命。
在任意实施方式中，经卤素原子取代的C2-C4烯烃包括式I所示的化合物中的一种或多种，
Figure PCTCN2022085783-appb-000001
其中，R 11～R 13各自独立地选自氢原子、卤素原子或者经卤素原子取代或未经取代的C1-C2的烷基，且R 11至R 13中的碳原子的数量加和为0、1或2；可选地，卤素原子包括氟原子或氯原子；
进一步可选地，R 11～R 13各自独立地选自氢原子、氟原子或者-CF 3。
由此，本申请实施例的经卤素原子取代的C2-C4烯烃，更容易控制其在电解液中的溶解度，且有利于其与负极活性材料发生电化学反应。
在任意实施方式中，经卤素原子取代的C2-C4烯烃包括式I-1至式I-5所示的化合物中的一种或多种，
Figure PCTCN2022085783-appb-000002
Figure PCTCN2022085783-appb-000003
在任意实施方式中，基于电解液的质量，经卤素原子取代的C2-C4烯烃的质量百分含量a满足0.05％≤a≤10％，可选地，0.1％≤a≤1％。
由此，本申请实施例通过调节经卤素原子取代的C2-C4烯烃的质量百分含量在上述范围内，经卤素原子取代的C2-C4烯烃可以稳定溶解于电解液中，并且能够在负极活性材料表面形成致密的保护膜，从而能够对负极极片起到良好的保护作用。
在任意实施方式中，部分卤化的饱和聚烯烃包括式II所示的结构单元中的一种或多种，且部分卤化的饱和聚烯烃包括至少一个部分卤化的烯烃结构单元，
Figure PCTCN2022085783-appb-000004
其中，R 21～R 24各自独立地选自氢原子、卤素原子或者经卤素原子取代或未经取代的C1～C8的直链或支链烷基；可选地，卤素原子包括氟原子或氯原子；进一步可选地，R 21～R 24各自独立地选自氢原子、氟原子或者-CF 3；部分卤化的饱和聚烯烃的总聚合度m满足1＜m≤220，且m为正整数；可选地，4＜m≤220。
由此，本申请实施例中的部分卤化的饱和聚烯烃的分子量相对较小，其与电解液中的其他物质之间的溶解度相对较高，有利于控制部分卤化的饱和聚烯烃在负极活性材料表面的电化学还原反应。
在任意实施方式中，部分卤化的饱和聚烯烃包括式II-1至式II-5所示的结构单元中的一种或多种，且部分卤化的饱和聚烯烃包括至少一个部分氟化的烯烃结构单元，
Figure PCTCN2022085783-appb-000005
在任意实施方式中，部分卤化的饱和聚烯烃的重均分子量小于等于10000Da；可选地，部分卤化的饱和聚烯烃的重均分子量为200Da～10000Da。
在任意实施方式中，基于电解液的质量，部分卤化的饱和聚烯烃的质量百分含量b满足0.05％≤a≤10％，可选地，0.1％≤a≤1％。
由此，本申请实施例中的部分卤化的饱和聚烯烃的重均分子量的分子量相对较小，其更容易溶解于电解液中，从而有利于在负极活性材料表面发生电化学反应形成固态电解质界面膜。
本申请的第二方面还提供了一种二次电池，包括正极极片、负极极片、隔离膜和电解液。隔离膜设置于正极极片和负极极片之间。电解液采用本申请第一方面任一实施例的电解液；可选地，正极极片包括锂元素和/或钠元素。
本申请的第三方面还提供了一种电池模块，包括如本申请第二方面实施例的二次电池。
本申请的第四方面还提供了一种电池包，包括如本申请第三方面实施例的电池模块。
本申请第五方面还提供了一种用电装置，包括如本申请第二方面实施例的二次电池、如本申请第三方面实施例的电池模块或如本申请第四方面实施例的电池包。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的用电装置的示意图。
其中，附图标记说明如下：
1、二次电池；11、外包装；111、顶盖组件；112、壳体；12、电极组件；10、电池模块；20、电池包；21、上箱体；22、下箱体；30、用电装置。
具体实施方式
以下，详细说明具体公开了本申请的电解液、二次电池、电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范 围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为 假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
电解液
第一方面，本申请提出了一种用于二次电池的电解液，该电解液包括经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃。
可以理解的是，该电解液可以包括经卤素原子取代的C2-C4烯烃；该电解液可以包括部分卤化的饱和聚烯烃；或者该电解液可以包括经卤素原子取代的经卤素原子取代的C2-C4烯烃和部分卤化的饱和聚烯烃。
经卤素原子取代的C2-C4烯烃是指C2-C4烯烃中的一个氢原子或者两个以上的氢原子被卤素原子取代。在两个以上的氢原子被卤素原子取代时，不同的氢原子可以被不同的卤素原子取代，例如，一个氢原子被氟原子F取代，另一个氢原子被溴原子Br取代。其中，C2-C4烯烃是指乙烯、丙烯和丁烯中的一种或多种。卤素原子可以为氟原子、氯原子等。示例性地，经卤素原子取代的C2-C4烯烃可以是氟乙烯、1,1-二氟乙烯、1,2-二氟乙烯、全氟乙烯、氟丙烯、1,1-二氟丙烯、1,2,3-三氟丙烯、氟丁烯、氯乙烯、1,1-二氯乙烯、1,2-二氯乙烯、全氯乙烯、氯丙烯、1,1-二氯丙烯、1,2,3-三氯丙烯和氯丁烯中的一种或多种。需要说明的是上述仅为举例性说明，并不用于限定经卤素原子取代的C2-C4烯烃的范围。
经卤素原子取代的C2-C4烯烃为气态，其作为电解液的负极成膜添加剂，可以在负极活性材料的表面发生电化学还原反应生成固态电解质界面膜(Solid Electrolyte Interphase，SEI)；并且经卤素原子取代的C2-C4烯烃作为小分子物质，其在电解液中的溶解度较高，更容易均匀分散于电解液内部，从而能够提高所形成的固态电解质界面膜的厚度均一性，进而能够保证固态电解质界面膜的均一性能。另外，经卤素原子取代的C2-C4气态烯烃作为工业原料，其成本相对较低。部分卤化的饱和聚烯烃是指其包含的重复的结构单元中包含卤素原子，且该聚合物仍具有氢原子。示例 性地，部分卤化的饱和聚烯烃的重复结构单元为氟乙烯、1,1-二氟乙烯、1,2-二氟乙烯、氟丙烯、1,1-二氟丙烯、1,2,3-三氟丙烯、氟丁烯、氯乙烯、1,1-二氯乙烯、1,2-二氯乙烯、全氯乙烯、氯丙烯、1,1-二氯丙烯、1,2,3-三氯丙烯和氯丁烯中的一种或多种。
部分卤化的饱和聚烯烃是指其包含的重复的结构单元中包含卤素原子，且该聚合物包含氢原子。示例性地，部分卤化的饱和聚烯烃的重复结构单元为氟乙烯、1,1-二氟乙烯、1,2-二氟乙烯、氟丙烯、1,1-二氟丙烯、1,2,3-三氟丙烯、氟丁烯、氯乙烯、1,1-二氯乙烯、1,2-二氯乙烯、全氯乙烯、氯丙烯、1,1-二氯丙烯、1,2,3-三氯丙烯和氯丁烯中的一种或多种。
本申请实施例的电解液通过设置经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃，上述物质可以在负极活性材料的表面发生电化学还原反应生成含卤素的固态电解质界面膜。所生成的含卤素固态电解质界面膜，一方面具有较低的界面阻抗，使得二次电池具有较好的低温特性；另一方面，可以降低电解液与负极活性材料的直接接触的风险，降低电解液发生还原反应的风险，从而提升二次电池的寿命。
在一些实施例中，经卤素原子取代的C2-C4烯烃包括式I所示的化合物中的一种或多种，
Figure PCTCN2022085783-appb-000006
其中，R 11～R 13各自独立地选自氢原子、卤素原子或者经卤素原子取代或未经取代的C1-C2的烷基，且R 11至R 13中的碳原子的数量加和为0、1或2。
可选地，R 11～R 13各自独立地选自氢原子、卤素原子或者-CF 3。
本申请实施例的经卤素原子取代的C2-C4烯烃，更容易控制其在电 解液中的溶解度，且有利于其与负极活性材料发生电化学反应。
可选地，卤素原子包括氟原子或氯原子；进一步可选地，卤素原子包括氟原子。氟原子和氯原子的电位相对较高，尤其是氟原子的电位相对较高，有利于参与电化学反应形成SEI膜。换言之，经氟原子取代的C2-C4烯烃更有利于参与电化学反应形成SEI膜。
示例性地，经卤素原子取代的C2-C4烯烃包括式I-1至式I-5所示的化合物中的一种或多种，
Figure PCTCN2022085783-appb-000007
在一些实施例中，基于电解液的质量，经卤素原子取代的C2-C4烯烃的质量百分含量a满足0.05％≤a≤10％。
发明人发现，经卤素原子取代的C2-C4烯烃的质量百分含量a小于0.05％时，经卤素原子取代的C2-C4烯烃在电解液中的含量过低，其在负极活性材料所形成的SEI不够致密，可能无法有效保护负极极片的界面。
由于经卤素原子取代的C2-C4烯烃在环境温度下例如25℃为气态，经卤素原子取代的C2-C4烯烃的质量百分含量a大于10％时，经卤素原子取代的C2-C4烯烃在电解液中的含量过高，可能超过其自身的溶解度，部分经卤素原子取代的C2-C4烯烃会挥发，挥发过程会影响电解液的存储稳定性。
鉴于上述问题，发明人将经卤素原子取代的C2-C4烯烃的质量百分含量a设置为0.05％≤a≤10％，可选地，0.1％≤a≤1％。在该含量范围的 经卤素原子取代的C2-C4烯烃，可以稳定溶解于电解液中，并且能够在负极活性材料表面形成致密的保护膜，从而能够对负极极片起到良好的保护作用。
在一些实施例中，部分卤化的饱和聚烯烃包括式II所示的结构单元中的一种或多种，且部分卤化的饱和聚烯烃包括至少一个部分卤化的烯烃结构单元，
Figure PCTCN2022085783-appb-000008
其中，R 21～R 24各自独立地选自氢原子、卤素原子或者经卤素原子取代或未经取代的C1～C8的直链或支链烷基；进一步可选地，R 21～R 24各自独立地选自氢原子、卤素原子或者-CF 3；部分卤化的饱和聚烯烃的总聚合度m满足1＜m≤220，且m为正整数；可选地，4＜m≤220。
该类部分卤化的饱和聚烯烃的分子量相对较小，其与电解液中的其他物质之间的溶解度相对较高，有利于控制部分卤化的饱和聚烯烃在负极活性材料表面的电化学还原反应。
可选地，卤素原子包括氟原子或氯原子；进一步可选地，卤素原子包括氟原子。氟原子和氯原子的电位相对较高，尤其是氟原子的电位相对较高，有利于参与电化学反应形成SEI膜。换言之，部分氟化的饱和聚烯烃更有利于参与电化学反应形成SEI膜。
具体地，部分卤化的饱和聚烯烃包括式II-1至式II-5所示的结构单元中的一种或多种，且部分卤化的饱和聚烯烃包括至少一个部分氟化的烯烃结构单元，
Figure PCTCN2022085783-appb-000009
示例性地，部分卤化的饱和聚烯烃可以为以下聚合物，
Figure PCTCN2022085783-appb-000010
其中，m和n均为正整数。
可选地，部分卤化的饱和聚烯烃的重均分子量小于等于10000Da；进一步可选地，部分卤化的饱和聚烯烃的重均分子量为200Da～10000Da。部分卤化的饱和聚烯烃的重均分子量的分子量相对较小，其更容易溶解于电解液中，从而有利于在负极活性材料表面发生电化学反应形成SEI膜。
在一些实施例中，基于电解液的质量，部分卤化的饱和聚烯烃的质量百分含量b满足0.05％≤a≤10％，可选地，0.1％≤a≤1％。
在上述含量范围的部分卤化的饱和聚烯烃，一方面能够在负极活性材料表面形成致密且稳定的SEI膜；另一方面，其能够保持一定的粘度，粘度相对较低，从而降低了其对金属离子迁移的不利影响，能够保证金属离子在电解液中的传输特性，进而保证二次电池的电化学性能。
本申请实施例的电解液在正极极片和负极极片之间起到传导金属离子的作用，其为液体状态。
在一些实施例中，电解液包括还可以包括电解质盐和溶剂。
可选地，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
可选地，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
可选地，电解液还可以包括添加剂。例如添加剂可以包括其他负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
二次电池
第二方面，本申请提出了一种二次电池。该二次电池包括正极极片、负极极片、隔离膜和电解液。隔离膜设置于正极极片和负极极片之间，以隔开正极极片和负极极片。电解液可以采用本申请第一方面的电解液。
根据本申请实施例的二次电池，电解液可以在负极材料表面形成稳定的SEI膜，SEI膜能够有效地防护负极活性材料，保证负极活性材料的结构稳定性，从而改善二次电池的低温性能和使用寿命。
可选地，正极极片包括锂元素和/或钠元素。在二次电池充放电过程中，锂离子和/或钠离子作为活性离子，能够在正极极片和负极极片之间稳定迁移，从而保证二次电池的电化学性能。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施例中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施例中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含 锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施例中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施例中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施例中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施例中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚 对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施例中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施例中，负极膜层还可选地包括粘结剂。粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施例中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施例中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施例中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[隔离膜]
在一些实施例中，二次电池中还包括隔离膜。本申请对隔离膜的种 类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施例中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施例中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施例中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施例中，二次电池的外包可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1和图2是作为一个示例的方形结构的二次电池1。
在一些实施例中，二次电池1包括外包装11。外包装11包括顶盖组件111和壳体112。正极极片、负极极片和隔离膜构成电极组件12容纳于壳体112内，壳体112内还容纳有电解液。正极极片或负极极片包含极耳。在二次电池1充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解液在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。具体地，该二次电池1可以为卷绕式或叠片式的电池，如锂离子电池、钠离子电池，但并不局限于此。
可选地，壳体112可包括底板和连接于底板上的侧板，底板和侧板 围合形成容纳腔。壳体112具有与容纳腔连通的开口，顶盖组件111能够盖设于开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件12。电极组件12封装于容纳腔内。电解液浸润于电极组件12中。二次电池1所含电极组件12的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施例中，二次电池1可以组装成电池。电池可以为电池模块或电池包括。例如，电池模块所含二次电池1的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块10。参照图3，在电池模块10中，多个二次电池1可以是沿电池模块10的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池1进行固定。可选地，电池模块10还可以包括具有容纳空间的外壳，多个二次电池1容纳于该容纳空间。
在一些实施例中，上述电池模块10还可以组装成电池包，电池包所含电池模块10的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。当然，电池包也可以由多个二次电池1直接组成。
图4和图5是作为一个示例的电池包20。参照图4和图5，在电池包20中可以包括电池箱和设置于电池箱中的多个电池模块10。电池箱包括上箱体21和下箱体22，上箱体21能够盖设于下箱体22，并形成用于容纳电池模块10的封闭空间。多个电池模块10可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的 能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置30。该用电装置30为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置30对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1～实施例23以及对比例1
1、正极极片的制备
采用厚度为8μm的铝箔作为正极集流体。将正极活性材料LiNi 1/3Co 1/3Mn 1/3O 2(NCM 333)、导电炭黑、粘结剂聚偏二氟乙烯(PVDF)按93：2：5的重量比在适量的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；将正极浆料涂覆于正极集流体的表面上，经烘干等工序后，得到正极极片。
2、负极极片的制备：将负极活性材料石墨、导电炭黑、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶乳液(SBR)按96.5：1.0：1.0：1.5 重量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体上，经烘干等工序后，得到负极极片。
3、电解液的制备：将体积比为3：7的碳酸乙烯酯(EC)和碳酸甲乙酯(EMC)混合均匀，得到有机溶剂，然后将负极成膜添加剂和1mol/L的LiPF 6均匀溶解在上述有机溶剂中，其中负极成膜添加剂的种类和质量百分含量如表1和表2所示。
4、二次电池的制备
将正极极片、隔离膜(PP/PE/PP复合薄膜)、负极极片依次层叠设置，然后卷绕成电芯并装入包装外壳中，将上述电解液注入到电芯中，之后经过密封、静置、热冷压、化成等工序，得到二次电池。
表1
Figure PCTCN2022085783-appb-000011
表2
Figure PCTCN2022085783-appb-000012
Figure PCTCN2022085783-appb-000013
Figure PCTCN2022085783-appb-000014
测试部分
1、二次电池的循环性能测试
在45℃下，将二次电池静置30分钟，之后以1C恒流充电至电压为4.2V，进一步以4.2V恒压充电至电流为0.05C，静置5分钟，然后以1C恒流放电至电压为2.8V，此为一个充放电循环过程，此次的放电容量为电池的首次放电容量，将电池按照上述方法进行1000次循环充电/放电测试，并记录二次电池第1000次循环后的放电容量。
二次电池循环1000次后的容量保持率(％)＝(第1000循环的放电容量/首次循环的放电容量)×100％。
2、低温直流阻抗DCR的测试方法
常温时调整二次电池的荷电状态(SOC)至容量的20％，置于-25℃的高低温箱中，静置2小时，使二次电池温度达到-25℃，测试此时二次电池的电压并记为U1，然后以0.3C的倍率放电10S，测试二次电池放电后的电压并记为U2。
二次电池的低温DCR＝(U1-U2)/I，I表示电流。
测试结果
本申请的电解液在改善二次电池的低温性能和寿命方面的作用如 表3所示，
表3
Figure PCTCN2022085783-appb-000015
从表3的数据可以看出，相较于对比例1，本申请实施例在电解 液中添加经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃，二次电池的容量保持率和DCR能够得到显著的改善。
由实施例1至实施例7可以看出，经卤素原子取代的C2-C4烯烃的质量百分含量在0.05％～10％时，尤其是经卤素原子取代的C2-C4烯烃的质量百分含量在0.1％～1％时，二次电池的容量保持率相对较高，且DCR相对较小，换言之，二次电池的循环性能和低温性能得到了显著改善。
由实施例8和实施例9可以看出，采用多种经卤素原子取代的C2-C4烯烃也可以改善二次电池的循环性能和低温性能。
由实施例10至实施例16可以看出，部分卤化的饱和聚烯烃的质量百分含量在0.05％～10％时，尤其是部分卤化的饱和聚烯烃的质量百分含量在0.1％～1％时，二次电池的容量保持率相对较高，且DCR相对较小，换言之，二次电池的循环性能和低温性能得到了显著改善。
由实施例17和实施例18可以看出，采用多种部分卤化的饱和聚烯烃也可以改善二次电池的循环性能和低温性能。
由实施例12、实施例19至实施例22可以看出，部分卤化的饱和聚烯烃的重均分子量在小于10000Da时，尤其是200Da～10000Da，二次电池的容量保持率相对较高，且DCR相对较小。
相较于实施例3和实施例12，实施例23同时采用经卤素原子取代的C2-C4烯烃和部分卤化的饱和聚烯烃，三者均能显著改善二次电池的性能。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (12)

  1. 一种用于二次电池的电解液，包括经卤素原子取代的C2-C4烯烃和/或部分卤化的饱和聚烯烃。
  2. 根据权利要求1所述的电解液，其中，
    所述经卤素原子取代的C2-C4烯烃包括式I所示的化合物中的一种或多种，
    Figure PCTCN2022085783-appb-100001
    其中，R 11～R 13各自独立地选自氢原子、卤素原子或者经卤素原子取代或未经取代的C1-C2的烷基，且R 11至R 13中的碳原子的数量加和为0、1或2；可选地，所述卤素原子包括氟原子或氯原子；
    进一步可选地，R 11～R 13各自独立地选自氢原子、氟原子或者-CF 3。
  3. 根据权利要求1或2所述的电解液，其中，
    所述经卤素原子取代的C2-C4烯烃包括式(I-1)至式(I-5)所示的化合物中的一种或多种，
    Figure PCTCN2022085783-appb-100002
  4. 根据权利要求1至3中任一项所述的电解液，其中，
    基于所述电解液的质量，所述经卤素原子取代的C2-C4烯烃的质量百分含量a满足0.05％≤a≤10％，可选地，0.1％≤a≤1％。
  5. 根据权利要求1至4中任一项所述的电解液，其中，
    所述部分卤化的饱和聚烯烃包括式II所示的结构单元中的一种或多种，且所述部分卤化的饱和聚烯烃包括至少一个部分卤化的烯烃结构单元，
    Figure PCTCN2022085783-appb-100003
    其中，R 21～R 24各自独立地选自氢原子、卤素原子或者经卤素原子取代或未经取代的C1～C8的直链或支链烷基；可选地，所述卤素原子包括氟原子或氯原子；
    进一步可选地，R 21～R 24各自独立地选自氢原子、氟原子或者-CF 3；
    所述部分卤化的饱和聚烯烃的总聚合度m满足1＜m≤220，且m为正整数；可选地，4＜m≤220。
  6. 根据权利要求1至5中任一项所述的电解液，其中，
    所述部分卤化的饱和聚烯烃包括式(II-1)至式(II-5)所示的结构单元中的一种或多种，且所述部分卤化的饱和聚烯烃包括至少一个部分氟化的烯烃结构单元，
    Figure PCTCN2022085783-appb-100004
  7. 根据权利要求1至6中任一项所述的电解液，其中，
    所述部分卤化的饱和聚烯烃的重均分子量小于等于10000Da；
    可选地，所述部分卤化的饱和聚烯烃的重均分子量为200Da～10000Da。
  8. 根据权利要求1至7中任一项所述的电解液，其中，
    基于所述电解液的质量，所述部分卤化的饱和聚烯烃的质量百分含量b满足0.05％≤a≤10％，可选地，0.1％≤a≤1％。
  9. 一种二次电池，其特征在于，包括：
    正极极片；
    负极极片；
    设置于所述正极极片和所述负极极片之间的隔离膜；以及
    如权利要求1至8中任一项所述的电解液；
    可选地，所述正极极片包括锂元素和/或钠元素。
  10. 一种电池模块，包括如权利要求9所述的二次电池。
  11. 一种电池包，包括如权利要求10所述的电池模块。
  12. 一种用电装置，包括如权利要求9所述的二次电池、如权利要求10所述的电池模块或如权利要求11所述的电池包。
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