WO2023225804A1 - 二次电池以及包含其的电池模块、电池包及用电装置 - Google Patents

二次电池以及包含其的电池模块、电池包及用电装置 Download PDF

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WO2023225804A1
WO2023225804A1 PCT/CN2022/094511 CN2022094511W WO2023225804A1 WO 2023225804 A1 WO2023225804 A1 WO 2023225804A1 CN 2022094511 W CN2022094511 W CN 2022094511W WO 2023225804 A1 WO2023225804 A1 WO 2023225804A1
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optionally
secondary battery
lithium
aqueous electrolyte
current collector
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PCT/CN2022/094511
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English (en)
French (fr)
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吴则利
韩昌隆
陈慧玲
郭洁
黄磊
张翠平
刘文浩
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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 KR1020237033393A priority Critical patent/KR20230165235A/ko
Priority to EP22931263.2A priority patent/EP4307419A1/en
Priority to CN202280012718.5A priority patent/CN117441250A/zh
Priority to PCT/CN2022/094511 priority patent/WO2023225804A1/zh
Priority to US18/468,906 priority patent/US20240014445A1/en
Publication of WO2023225804A1 publication Critical patent/WO2023225804A1/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
    • 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
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • 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
    • 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
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated 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
    • H01M2300/0025—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
    • H01M2300/0048—Molten electrolytes used at high temperature
    • H01M2300/0051—Carbonates
    • 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

  • the present application belongs to the field of battery technology, and specifically relates to a secondary battery, a battery module, a battery pack and an electrical device containing the same.
  • secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.
  • energy storage power systems such as hydraulic, thermal, wind and solar power stations
  • the requirements for their energy density are getting higher and higher.
  • Copper foil current collectors do not contribute capacity in secondary batteries. Thinning copper foil current collectors can not only reduce costs, but also allow more active materials to be accommodated in the limited battery case. Therefore, copper foil current collector thinning is an important factor.
  • the purpose of this application is to provide a secondary battery and a battery module, a battery pack and an electrical device including the same, aiming to make the secondary battery using a thinned negative electrode current collector take into account low cost, high energy density and high power performance. and high safety performance.
  • a first aspect of the present application provides a secondary battery, including a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material located on at least one surface of the positive electrode current collector.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, wherein the non-aqueous electrolyte includes a compound shown in Formula 1, and X and Y each independently represent Fluorine atom, or at least one of the following partially fluorinated or fully fluorinated groups: C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl group, a C1-C10 alkoxy group, a C2-C10 alkenyloxy group, a C2-C10 alkynyloxy group, a C6-C8 aryloxy group, and at least one of X and Y represents a fluorine atom;
  • the mass percentage of the compound represented by Formula 1 is A1%, the thickness of the negative electrode current collector is H1 ⁇ m, and the compacted density of the negative electrode active material layer is P1 g/cm 3 , and the secondary battery satisfies: H1 is 3 to 7, A1/H1 is 0.003 to 0.40, and P1/A1 is 1 to 90.
  • the inventor of the present application found during the research process that in a secondary battery using a thinned negative electrode current collector, when the non-aqueous electrolyte contains the compound shown in Formula 1 and by controlling its content A1% and the thickness of the negative electrode current collector H1 ⁇ m and The relationship between the compacted density of the negative active material layer P1g/ cm3 enables the secondary battery to satisfy both low cost and high energy when A1/H1 is 0.003 to 0.40 and P1/A1 is 1 to 90. density, high power performance and high safety features.
  • A1/H1 is 0.003 to 0.1, more optionally 0.003 to 0.08. This enables the secondary battery to have both high power performance and high safety performance.
  • P1/A1 is from 3 to 90, more optionally from 5 to 90. This enables the secondary battery to have both high power performance and high safety performance.
  • the thickness of the positive electrode current collector is H2 ⁇ m
  • the fracture elongation of the positive electrode current collector is Q%
  • the compacted density of the positive electrode active material layer is P2g/cm 3
  • the The above secondary battery satisfies: H2 is 4 to 14, A1/H2 is 0.0015 to 0.20, Q+A1 is 1 to 4 and P2/A1 is 2 to 340.
  • the inventor of the present application also found during further research that when the content A1% of the compound represented by Formula 1 is related to the thickness H2 ⁇ m of the positive electrode current collector, the fracture elongation Q% of the positive electrode current collector, and the compacted density P2g of the positive electrode active material layer /cm 3 further satisfies H2 from 4 to 14, A1/H2 from 0.0015 to 0.20, Q+A1 from 1 to 4 and P2/A1 from 2 to 340, which helps to improve the performance of secondary batteries after thinning the positive electrode current collector. Negative effects on power performance, safety performance and processing performance.
  • A1/H2 is 0.002 to 0.05, more optionally 0.01 to 0.05. This helps to increase the strength of the cathode current collector, improve the processing performance of the cathode pole piece, and reduce or even avoid band breakage; it also helps the secondary battery to have high power performance and high safety performance.
  • Q+A1 is optionally 1.5 to 3.5, more optionally 2.0 to 3.5. This helps to increase the strength of the cathode current collector, improve the processing performance of the cathode pole piece, and reduce or even avoid band breakage; it also helps the secondary battery to have high power performance and high safety performance.
  • P2/A1 ranges from 5 to 340, and more optionally ranges from 10 to 340. This helps to improve the power performance and safety performance of secondary batteries.
  • A1 is optionally 0.02 to 1.6, more optionally 0.02 to 0.5. This can improve the defects such as poor power performance, increased safety hazards, and poor processing performance caused by thinning of the negative electrode current collector and positive electrode current collector.
  • P1 is from 1.4 to 1.8, more optionally from 1.55 to 1.75. This helps to increase the energy density of secondary batteries.
  • P2 is 3.2 to 3.7, more optionally 3.4 to 3.7. This helps to increase the energy density of secondary batteries.
  • Q optionally ranges from 0.5 to 3.5, more optionally from 1.5 to 3.5. Therefore, the positive electrode current collector has high strength and good processing performance, and is not easy to break.
  • the non-aqueous electrolyte further includes a first lithium salt
  • the first lithium salt includes lithium hexafluorophosphate
  • the mass percentage of the lithium hexafluorophosphate is A2%, based on the Total mass of non-aqueous electrolyte.
  • A2/A1 is 5 to 650, more optionally 15 to 300. This helps to further improve the capacity retention rate of the secondary battery while improving the problems of poor power performance and increased safety risks caused by thinning of the current collector.
  • A2 is 6 to 14.
  • the non-aqueous electrolyte further includes a first lithium salt
  • the first lithium salt includes a combination of lithium hexafluorophosphate and lithium bisfluorosulfonimide
  • the mass of the lithium hexafluorophosphate The percentage content is A2%, and the mass percentage content of the lithium bisfluorosulfonyl imide is A3%, both based on the total mass of the non-aqueous electrolyte.
  • A2 is 6 to 14, and A3 is greater than 0 and less than or equal to 5.
  • A3/A2 is below 0.8, more optionally 0.05 to 0.3. This helps to form an interface film with lower resistance.
  • A2/A1 is 5 to 650, more optionally 15 to 300. This helps to further improve the capacity retention rate of the secondary battery while improving the problems of poor power performance and increased safety risks caused by thinning of the current collector.
  • the non-aqueous electrolyte further includes a second lithium salt
  • the second lithium salt includes lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, At least one of lithium fluorophosphate, lithium difluorodioxalate phosphate and lithium tetrafluorooxalate phosphate
  • the total mass percentage of the second lithium salt in the non-aqueous electrolyte is A4%, based on the non-aqueous electrolyte Total mass of water electrolyte.
  • A4 is under 5, more optionally under 2.
  • the second lithium salt can be used as an auxiliary lithium salt to further improve the interface properties of the positive electrode and/or the negative electrode, or to improve the ionic conductivity or thermal stability of the non-aqueous electrolyte.
  • the second lithium salt includes lithium difluorophosphate
  • the mass ratio ⁇ of the lithium difluorophosphate to the lithium hexafluorophosphate is 0.01 to 0.15, more optionally Ground is 0.01 to 0.1.
  • Lithium difluorophosphate has high electrochemical stability, can increase the ionic conductivity of the non-aqueous electrolyte, improve the properties of the positive electrode interface film and the negative electrode interface film, and also helps to build a stable and low-impedance positive electrode interface film and The negative electrode interface film can effectively reduce the decomposition of non-aqueous electrolyte and further improve the power performance and safety performance of secondary batteries.
  • the non-aqueous electrolyte solution also includes a cyclic carbonate compound, and the mass percentage of the cyclic carbonate compound is B1%, based on the non-aqueous electrolyte solution total mass.
  • B1 is 0.5 to 20, more optionally 15 to 18.
  • B1/20+A1 is 1 to 3, and more optionally is 1 to 2. This helps to further improve the capacity retention rate of the secondary battery while improving the problems of poor power performance and increased safety risks caused by thinning of the current collector.
  • the cyclic carbonate compound includes at least one of ethylene carbonate, propylene carbonate, vinylene carbonate, and ethylene ethylene carbonate.
  • the non-aqueous electrolyte solution further includes fluorinated ethylene carbonate, the mass percentage of which is C1%, based on the total mass of the non-aqueous electrolyte solution.
  • fluorinated ethylene carbonate the mass percentage of which is C1%, based on the total mass of the non-aqueous electrolyte solution.
  • 0 ⁇ C1 ⁇ 2.5, more optionally, 0 ⁇ C1 ⁇ 2.0 This can effectively improve the cycle performance of the secondary battery.
  • any embodiment of the present application optionally, 0.25 ⁇ C1/A1 ⁇ 25, more optionally, 0.5 ⁇ C1/A1 ⁇ 10. This helps to further improve the cycle performance of the secondary battery while improving the problems of poor power performance and increased safety hazards caused by thinning of the current collector.
  • the non-aqueous electrolyte further includes a water-removing additive, and the water-removing additive includes hexamethyldisilazane and tris(trimethylsilyl)phosphate. of at least one.
  • the mass percentage of the water-removing additive is less than 2%, more preferably 0.05% to 1%, based on the total mass of the non-aqueous electrolyte. This helps to further improve the power performance, storage performance and safety performance of secondary batteries.
  • X and Y both represent fluorine atoms.
  • one of X and Y represents a fluorine atom, and the other represents at least one of the group consisting of the following partially fluorinated or fully fluorinated groups: C1- C5 alkyl, C2-C5 alkenyl, C2-C5 alkynyl, phenyl, phenoxy, C1-C5 alkoxy, C2-C5 alkenyloxy and C2-C5 alkynyloxy.
  • one of X and Y represents a fluorine atom, and the other represents at least one of the group consisting of the following partially fluorinated or fully fluorinated groups: methyl , ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, vinyl, propenyl, allyl, butadienyl, ethynyl, propynyl, phenyl, methoxy, ethyl Oxy, propoxy, vinyloxy, propyleneoxy, ethynyloxy, propynyloxy and phenoxy.
  • the presence of fluorine atoms helps to form a thinner positive electrode interface film and/or negative electrode interface film, thereby contributing to the uniform transport of lithium ions and also effectively inhibiting the formation of lithium dendrites.
  • the compound represented by Formula 1 includes at least one of the following compounds,
  • the negative electrode current collector uses copper foil or copper alloy foil.
  • the positive electrode current collector uses aluminum foil or aluminum alloy foil.
  • a second aspect of the present application provides a battery module, which includes the secondary battery of the first aspect of the present application.
  • a third aspect of the present application provides a battery pack, which includes one of the secondary battery of the first aspect of the present application and the battery module of the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, which includes at least one of the secondary battery of the first aspect of the present application, the battery module of the second aspect, and the battery pack of the third aspect of the present application.
  • the battery modules, battery packs and electrical devices of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of a power consumption device including the secondary battery of the present application as a power source.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that 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
  • the 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) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), 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).
  • C1-C6 alkyl is expressly contemplated to separately disclose C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2 -Alkyl groups of C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5 and C5-C6.
  • the thickness of the current collector and the active material layer have meanings known in the art, and can be tested using methods known in the art.
  • a spiral micrometer is used for measurement.
  • the compacted density of the active material layer has a meaning known in the art, and can be tested using methods known in the art.
  • the compacted density of the active material layer area density of the active material layer/thickness of the active material layer.
  • the areal density of the active material layer is a well-known meaning in the art, and can be tested using methods known in the art.
  • the rupture elongation of the positive electrode current collector refers to the rupture elongation at room temperature.
  • Copper foil current collector is one of the essential components of secondary batteries. In order to further improve the energy density of secondary batteries, thinning copper foil current collectors is still one of the most effective measures at present. Although thinning copper foil current collectors can reduce costs and increase the energy density of secondary batteries, this solution is difficult to implement in industry. The main reasons include the following points: first, after the copper foil current collector is thinned, the resistance of the copper foil increases, which leads to an increase in the internal resistance of the battery and poor power performance; second, because copper foil is a good thermal conductor material , its thinning will cause the secondary battery to increase heat production and make heat dissipation difficult, thereby increasing the safety risks of the secondary battery.
  • high-power batteries require a large discharge current during use, so the heat generated during the discharge process is high.
  • the decomposition reaction of the non-aqueous electrolyte at the positive and negative electrode interfaces increases significantly at high temperatures, resulting in positive and negative electrode interface impedances.
  • thickening the copper foil current collector is one of the commonly used measures.
  • the inventor of the present application was surprised to find during the research process that by using a suitable non-aqueous electrolyte, problems such as poor power performance and increased safety risks caused by thinning of the negative electrode current collector can be solved, so that the secondary battery can be balanced at the same time Low cost, high energy density, high power performance and high safety performance.
  • embodiments of the present application provide a secondary battery.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • the secondary battery of the present application may be a lithium secondary battery, particularly a lithium ion secondary battery.
  • a secondary battery includes an electrode assembly, a non-aqueous electrolyte, and an outer packaging.
  • the outer packaging is used to encapsulate the electrode assembly and the non-aqueous electrolyte.
  • the electrode assembly usually includes a positive electrode piece, and the electrode assembly may also include a negative electrode piece and a separator.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents short circuit between the positive electrode and the negative electrode and allows lithium ions to pass through.
  • the positive electrode piece, the isolation film and the negative electrode piece can be made into an electrode assembly through a winding process or a lamination process.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces opposite in its thickness direction, and the positive electrode active material layer disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two surfaces opposite in its thickness direction, and the negative electrode active material layer disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the non-aqueous electrolyte solution includes a compound represented by Formula 1, where X and Y each independently represent a fluorine atom, or at least one of the following groups that are partially fluorinated or fully fluorinated: One: C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl, C1-C10 alkoxy, C2-C10 alkenyloxy, C2-C10 an alkynyloxy group, a C6-C8 aryloxy group, and at least one of X and Y represents a fluorine atom.
  • X and Y each independently represent a fluorine atom, or at least one of the following groups that are partially fluorinated or fully fluorinated: One: C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl, C1-C10 alkoxy, C2-C10 al
  • the mass percentage of the compound represented by Formula 1 is A1%, the thickness of the negative electrode current collector is H1 ⁇ m, and the compacted density of the negative electrode active material layer is P1g /cm 3 , and the secondary battery satisfies: H1 is 3 to 7, A1/H1 is 0.003 to 0.40, and P1/A1 is 1 to 90.
  • the thickness H1 ⁇ m of the negative electrode current collector satisfies H1 between 3 and 7.
  • H1 can be between 3 and 6.5, between 3 and 6, between 3 and 5.5 or between 3 and 5. .
  • the inventor of the present application found during the research process that in a secondary battery using a thinned negative electrode current collector, when the non-aqueous electrolyte contains the compound shown in Formula 1 and by controlling its content A1% and the thickness of the negative electrode current collector H1 ⁇ m and The relationship between the compacted density of the negative active material layer P1g/ cm3 enables the secondary battery to satisfy both low cost and high energy when A1/H1 is 0.003 to 0.40 and P1/A1 is 1 to 90. density, high power performance and high safety features.
  • the molecular structure of the compound shown in Formula 1 contains fluorine atoms, which can be reduced on the surface of the negative active material in preference to organic solvents, and its reduction products also have low-resistance characteristics, which helps to form a low-resistance negative electrode.
  • Interface film at the same time, the B atoms in the molecular structure of the compound shown in Formula 1 can easily combine with inorganic components such as LiF in the negative electrode interface film, which can speed up the transmission of lithium ions and significantly reduce the internal resistance of the battery, making the secondary Batteries not only have high energy density but also have high power performance and are capable of high current discharge.
  • the compound shown in Formula 1 has higher thermal stability, for example, better than the common LiPF 6 , which helps to improve the overall heat resistance of the non-aqueous electrolyte; at the same time, the compound shown in Formula 1 is not as sensitive to moisture as LiPF 6 , which also helps to improve the water resistance of the non-aqueous electrolyte, reduce the formation of HF and reduce the acidity of the non-aqueous electrolyte. Therefore, the non-aqueous electrolyte of the present application can have high thermal stability and electrochemical stability, thereby reducing the decomposition reaction of the non-aqueous electrolyte at high temperatures and reducing the internal resistance of the battery.
  • the heat production of the secondary battery is directly related to the internal resistance of the battery. Therefore, when the internal resistance of the battery is reduced, the heat production of the secondary battery will also be reduced, which in turn enables the secondary battery to have high energy density while also having High power performance and high safety performance.
  • the inventor was also surprised to find that since the anion radius in the compound shown in Formula 1 is large and easy to be reduced, the lithium ions dissociated from its molecular structure can also become active lithium ions, contributing part of the capacity, thus Helps improve the energy density of secondary batteries.
  • the non-aqueous electrolyte contains the compound shown in Formula 1, it helps to form a low-resistance interfacial film on the surface of the negative active material, improves the power performance and safety performance of the secondary battery, and also helps to increase active lithium
  • the number of ions contributes part of the capacity.
  • the inventor of the present application found in further research that the content of the compound shown in Formula 1 needs to be reasonably matched with the thickness of the negative electrode current collector and the compaction density of the negative electrode active material layer to effectively reduce the negative electrode current collector after thinning.
  • the negative impact on power performance and safety performance makes secondary batteries take into account low cost, high energy density, high power performance and high safety performance at the same time.
  • the content A1% of the compound represented by Formula 1 and the thickness H1 ⁇ m of the negative electrode current collector satisfy that A1/H1 is between 0.003 and 0.40.
  • A1/H1 is less than 0.003
  • the negative electrode current collector is thicker and the content of the compound shown in Formula 1 is low, and a low-impedance negative electrode interface film cannot be formed. Therefore, the negative electrode interface impedance is high, and the negative electrode current collector thinning cannot effectively reduce the impact on the internal battery of the battery. The resistance and heat generation deteriorate, so the power performance and safety performance of the secondary battery are poor.
  • the compound shown in Formula 1 cannot contribute active lithium ions; when A1/H1 is greater than 0.40, the negative electrode current collector is thin.
  • the higher content of the compound shown in Formula 1 results in the formation of an overly thick negative electrode interface film, resulting in higher negative electrode interface resistance, higher battery internal resistance and higher heat production, and poorer power performance and safety performance of the secondary battery.
  • A1/H1 is 0.003 to 0.30, 0.003 to 0.25, 0.003 to 0.20, 0.003 to 0.16, 0.003 to 0.12, 0.003 to 0.10, 0.003 to 0.08, 0.003 to 0.06, 0.01 to 0.30, 0.01 to 0.25, 0.01 to 0.20, 0.01 to 0.16, 0.01 to 0.12, 0.01 to 0.10, 0.01 to 0.08 or 0.01 to 0.06.
  • the content A1% of the compound represented by Formula 1 and the compacted density P1g/cm of the negative active material layer satisfy P1/A1 between 1 and 90. Therefore, the compound represented by Formula 1 contributes to The formation of a low-resistance interface film on the surface of the negative electrode active material can, on the one hand, help increase lithium ion transmission, and on the other hand, it can reduce the negative electrode interface resistance, thereby effectively reducing the deterioration of the battery's internal resistance and heat generation caused by thinning of the negative electrode current collector. Secondary batteries have both high power performance and high safety performance.
  • P1/A1 is 1.5 to 90, 1.5 to 75, 1.5 to 50, 1.5 to 35, 1.5 to 30, 1.5 to 25, 1.5 to 20, 1.5 to 15, 1.5 to 10, 3 to 90, 3 to 75, 3 to 50, 3 to 35, 3 to 30, 3 to 25, 3 to 20, 3 to 15, 3 to 10, 5 to 90, 5 to 75, 5 to 50, 5 to 35, 5 to 30, 5 to 25, 5 to 20, 5 to 15 or 5 to 10.
  • the negative electrode current collector uses copper foil or copper alloy foil.
  • the copper foil may be rolled copper foil or electrolytic copper foil.
  • As the copper alloy foil Cu-Ag, Cu-Te, Cu-Mg, Cu-Sn, Cu-Si, Cu-Mn, Cu-Be-Co, Cu-Ti, Cu-Ni-Si, Cu-Cr, Cu-Zr, Cu-Fe, Cu-Al, Cu-Zn, Cu-Co and other alloy foils.
  • the thickness of the positive electrode current collector is H2 ⁇ m, and H2 is 4 to 14.
  • H2 can be 4 to 13, 4 to 12, 4 to 11, 4 to 10, 4 to 9 or 4 to 8.
  • Thinning the cathode current collector can help further improve the energy density of secondary batteries.
  • the resistance and heat generation increase, resulting in poor power performance and safety performance of the secondary battery.
  • the aluminum foil current collector is thinned, its own strength becomes worse.
  • thinned cathode current collectors are usually used with higher compaction densities, so the cathode tabs are prone to being crushed during the rolling process, which will also affect the cathode tabs and secondary batteries. processing performance.
  • the inventor of the present application also found during further research that when the content A1% of the compound represented by Formula 1 is related to the thickness H2 ⁇ m of the positive electrode current collector, the fracture elongation Q% of the positive electrode current collector, and the compacted density P2g of the positive electrode active material layer /cm 3 further satisfies H2 from 4 to 14, A1/H2 from 0.0015 to 0.20, Q+A1 from 1 to 4 and P2/A1 from 2 to 340, which helps to improve the performance of secondary batteries after thinning the positive electrode current collector. Negative effects on power performance, safety performance and processing performance.
  • the molecular structure of the compound shown in Formula 1 contains an oxalate group, which can be oxidized on the surface of the cathode active material in preference to the organic solvent, and its oxidation product also has low resistance characteristics, which helps to form Low-resistance positive electrode interface film; at the same time, the B atoms in the molecular structure of the compound shown in Formula 1 can easily combine with inorganic components such as LiF in the positive electrode interface film, which can accelerate lithium ion transmission and significantly reduce the internal resistance of the battery.
  • the BO bond in the molecular structure of the compound shown in Formula 1 can bond with Al 3+ and form a passivation film on the surface of the cathode current collector, thereby helping to increase the strength of the cathode current collector and improve the performance of the cathode current collector. Improve the processing performance of the chip, reduce or even avoid the occurrence of belt breakage.
  • the content A1% of the compound shown in Formula 1 and the thickness H2 ⁇ m of the cathode current collector satisfy that A1/H2 is between 0.0015 and 0.20. Therefore, the BO bond energy in the molecular structure of the compound shown in Formula 1 is related to Al 3+ Better bonding and formation of a passivation film with appropriate thickness on the surface of the cathode current collector will help increase the strength of the cathode current collector, improve the processing performance of the cathode pole piece, and reduce or even avoid band breakage.
  • A1/H2 is 0.002 to 0.15, 0.002 to 0.1, 0.002 to 0.08, 0.002 to 0.07, 0.002 to 0.06, 0.002 to 0.05, 0.005 to 0.15, 0.005 to 0.1, 0.005 to 0.08, 0.005 to 0.07, 0.0 05 to 0.06, 0.005 to 0.05, 0.01 to 0.15, 0.01 to 0.1, 0.01 to 0.08, 0.01 to 0.07, 0.01 to 0.06 or 0.01 to 0.05.
  • the content A1% of the compound represented by Formula 1 and the fracture elongation Q% of the cathode current collector satisfy that Q+A1 is between 1 and 4. Therefore, the BO bond energy in the molecular structure of the compound represented by Formula 1 is equal to Al 3+ bonds better and forms a passivation film with appropriate thickness on the surface of the cathode current collector, which helps to increase the strength of the cathode current collector, improve the processing performance of the cathode pole piece, and reduce or even avoid band breakage. And it can effectively avoid the following situation: when Q+A1 is less than 1, there may not be enough compounds shown in Formula 1 to bond with Al 3+ and form a passivation film on the surface of the positive electrode current collector.
  • the ductility of the positive electrode current collector is poor, and the roll Belt breakage is prone to occur during the pressing process, resulting in poor processing performance of the secondary battery.
  • Q+A1 is greater than 4
  • the positive electrode current collector has high ductility and good pressure resistance, but it is not resistant to puncture.
  • the material is squeezed, it is easy to break and produce large burrs, causing a high risk of short circuit in the battery.
  • the safety performance of the secondary battery may be poor.
  • more compounds shown in Formula 1 will also form a thicker interface film. , resulting in high positive electrode interface impedance, which may also affect the power performance and safety performance of the secondary battery.
  • Q+A1 is 1.5 to 4, 1.8 to 4, 2.0 to 4, 2.2 to 4, 2.4 to 4, 2.6 to 4, 2.8 to 4, 3.0 to 4, 1.5 to 3.5, 1.8 to 3.5, 2.0 to 3.5, 2.2 to 3.5, 2.4 to 3.5, 2.6 to 3.5, 2.8 to 3.5 or 3.0 to 3.5.
  • the content A1% of the compound represented by Formula 1 and the compacted density P2g/cm of the positive electrode active material layer satisfy P2/A1 between 2 and 340. Therefore, the compound represented by Formula 1 contributes to the positive electrode active material layer.
  • a low-resistance interface film is formed on the surface of the active material, which reduces the interface resistance of the cathode; it also helps the B atoms in the molecular structure of the compound shown in Formula 1 to better combine with the O atoms in the cathode active material, thereby reducing the cathode
  • the charge transfer resistance of the active material and the lithium ion phase diffusion resistance can reduce the internal resistance and heat generation of the battery and improve the power performance and safety performance of the secondary battery.
  • P2/A1 is 2 to 200, 2 to 100, 2 to 75, 2 to 50, 2 to 35, 2 to 30, 2 to 25, 2 to 20, 2 to 15, 3.5 to 340, 3.5 to 200, 3.5 to 100, 3.5 to 75, 3.5 to 50, 3.5 to 35, 3.5 to 30, 3.5 to 25, 3.5 to 20, 3.5 to 15, 5 to 340, 5 to 200, 5 to 100, 5 to 75 , 5 to 50, 5 to 35, 5 to 30, 5 to 25, 5 to 20, 10 to 340, 10 to 200, 10 to 100, 10 to 75, 10 to 50, 10 to 35, 10 to 30, 10 to 25 or 10 to 20.
  • the content A1% of the compound represented by Formula 1 is further related to the thickness H2 ⁇ m of the cathode current collector, the fracture elongation Q% of the cathode current collector, and the compacted density P2g/cm of the cathode active material layer. It satisfies that H2 is 4 to 11, A1/H2 is 0.006 to 0.1, Q+A1 is 1.5 to 3.5 and P2/A1 is 2 to 340.
  • the content A1% of the compound shown in Formula 1, the thickness H2 ⁇ m of the cathode current collector, the fracture elongation Q% of the cathode current collector, and the compacted density P2g/cm of the cathode active material layer further satisfy that H2 is 4 to 11, A1/H2 is 0.01 to 0.05, Q+A1 is 1.5 to 3.5 and P2/A1 is 5 to 75.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil or aluminum alloy foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the positive electrode current collector uses aluminum foil or aluminum alloy foil.
  • aluminum foil with a purity of more than 99.99% is used.
  • the aluminum alloy foil in addition to the aluminum element, it also contains at least one element of iron, magnesium, zinc, manganese and silicon.
  • the aluminum alloy foil can be an Al-Fe alloy foil, an Al-Mn alloy foil or an Al- Mg alloy foil.
  • the mass percentage of aluminum element in the aluminum alloy foil is optionally 95% to 99.5%, more optionally 98% to 99.5%.
  • the content A1% of the compound represented by Formula 1 satisfies A1 from 0.02 to 1.8.
  • A1 is 0.02 to 1.6, 0.02 to 1.4, 0.02 to 1.2, 0.02 to 1.0, 0.02 to 0.8, 0.02 to 0.7, 0.02 to 0.6, 0.02 to 0.5, 0.05 to 1.6, 0.05 to 1.4, 0.05 to 1.2, 0.05 to 1.0, 0.05 to 0.8, 0.05 to 0.7, 0.05 to 0.6, 0.05 to 0.5, 0.1 to 1.6, 0.1 to 1.4, 0.1 to 1.2, 0.1 to 1.0, 0.1 to 0.8, 0.1 to 0.7, 0.1 to 0.6 or 0.1 to 0.5.
  • a low-resistance positive electrode interface film and/or a negative electrode interface film can be formed, and a passivation film with a suitable thickness can be formed on the surface of the positive electrode current collector, thereby improving the negative electrode current collector. And defects such as poor power performance, increased safety hazards, and poor processing performance caused by thinning the cathode current collector.
  • the compacted density P1g/cm 3 of the negative active material layer satisfies P1 to be 1.4 to 1.8.
  • P1 is 1.4 to 1.75, 1.4 to 1.7, 1.4 to 1.65, 1.4 to 1.6, 1.55 to 1.8, 1.55 to 1.75, 1.55 to 1.7, 1.55 to 1.65 or 1.55 to 1.6.
  • the compaction density of the negative active material layer is in a higher range, it helps to increase the energy density of the secondary battery.
  • the compacted density P2g/cm of the cathode active material layer satisfies P2 to be 3.2 to 3.7.
  • P2 is 3.3 to 3.7, 3.4 to 3.7, 3.5 to 3.7, 3.2 to 3.6, 3.3 to 3.6, 3.4 to 3.6 or 3.5 to 3.6.
  • the compaction density of the positive active material layer is in a higher range, it helps to increase the energy density of the secondary battery.
  • the positive electrode current collector has a break elongation Q% that satisfies Q of 0.5 to 3.5.
  • Q is 1 to 3.5, 1.5 to 3.5, 1.8 to 3.5, 2.0 to 3.5, 2.2 to 3.5, 2.4 to 3.5, 2.6 to 3.5, 2.8 to 3.5 or 3.0 to 3.5.
  • the fracture elongation of the positive electrode current collector is within a suitable range, the positive electrode current collector has high strength and good processing performance, and is not easy to break.
  • one of X and Y represents a fluorine atom, and the other represents at least one of the following groups that are partially fluorinated or fully fluorinated: C1-C5 alkyl, C2- C5 alkenyl, C2-C5 alkynyl, phenyl, phenoxy, C1-C5 alkoxy, C2-C5 alkenyloxy and C2-C5 alkynyloxy.
  • one of X and Y represents a fluorine atom, and the other represents at least one of the following groups that are partially fluorinated or fully fluorinated: methyl, ethyl, n-propyl, iso Propyl, n-butyl, tert-butyl, vinyl, propenyl, allyl, butadienyl, ethynyl, propynyl, phenyl, methoxy, ethoxy, propoxy, vinyloxy base, propenyloxy, ethynoxy, propynyloxy and phenoxy.
  • X and Y both represent fluorine atoms.
  • the compound represented by Formula 1 includes at least one of the following compounds,
  • the non-aqueous electrolyte further includes a first lithium salt
  • the first lithium salt includes lithium hexafluorophosphate (LiPF 6 ) or lithium hexafluorophosphate (LiPF 6 ) and lithium bisfluorosulfonyl imide (LiFSI). combination.
  • Lithium hexafluorophosphate has the characteristic of high ionic conductivity. Therefore, when its content is within a suitable range, it helps to increase the overall ionic conductivity of the non-aqueous electrolyte, accelerate lithium ion transmission, and improve the capacity retention rate of secondary batteries.
  • lithium hexafluorophosphate has poor thermal stability in high temperature environments and will decompose to form PF 5 at higher temperatures.
  • PF 5 reacts with water to form HF, which easily corrodes the positive active material and increases battery flatulence.
  • the non-aqueous electrolyte contains both the compound shown in formula 1 and lithium hexafluorophosphate
  • the compound shown in formula 1 can react with lithium hexafluorophosphate to form the compound LiPF 4 C 2 O 4 , thereby reducing the decomposition of part of the lithium hexafluorophosphate and the formation of HF, thereby improving the secondary battery It also has good cycle performance.
  • lithium bisfluorosulfonimide is F 2 NO 4 S 2 .
  • Li and N atoms are connected to two electron-withdrawing sulfonyl groups, which fully delocalizes the charges on the N atoms.
  • Lithium bisfluorosulfonyl imide has a lower lattice energy and is easy to dissociate. It can improve the ionic conductivity of the non-aqueous electrolyte and reduce the viscosity of the non-aqueous electrolyte; in addition, lithium bisfluorosulfonyl imide also has the characteristics of good high temperature resistance and not easy to hydrolyze, and can form a thinner, more durable electrolyte on the surface of the negative active material.
  • the mass percentage of the lithium hexafluorophosphate is A2%, and A2 is 6 to 14, based on the total mass of the non-aqueous electrolyte. More optionally, A2 is 6 to 12, 6 to 10, 8 to 14, 8 to 12 or 8 to 10.
  • the mass percentage of the lithium bisfluorosulfonimide is A3%, and A3 is greater than 0 and less than or equal to 5, based on the total mass of the non-aqueous electrolyte. More optionally, A3 is 0.1 to 2.5, 0.1 to 2, 0.1 to 1.5, 0.1 to 1, 0.2 to 2.5, 0.2 to 2, 0.2 to 1.5, 0.2 to 1, 0.5 to 2.5, 0.5 to 2, 0.5 to 1.5 Or 0.5 to 1.
  • A3/A2 is below 0.8, more optionally 0.01 to 0.8, 0.05 to 0.8, 0.1 to 0.8, 0.01 to 0.6, 0.05 to 0.6, 0.1 to 0.6, 0.01 to 0.4, 0.05 to 0.4, 0.1 to 0.4, 0.01 to 0.3, 0.05 to 0.3 or 0.1 to 0.3. Therefore, the non-aqueous electrolyte is not easily hydrolyzed, can also achieve higher thermal stability, and at the same time, can help form an interface film with lower impedance.
  • A2/A1 ranges from 5 to 650, based on the total mass of the non-aqueous electrolyte.
  • Lithium hexafluorophosphate has the characteristic of high ionic conductivity. A reasonable combination of the content A1% of the compound shown in Formula 1 and the content A2% of lithium hexafluorophosphate will help to improve the deterioration of power performance and increase in safety risks caused by thinning of the current collector. Further improve the capacity retention rate of secondary batteries under the premise of solving other problems.
  • Performance, storage performance and safety performance may deteriorate; when the content of lithium hexafluorophosphate is low and the content of the compound shown in Formula 1 is high, the compound shown in Formula 1 is not easy to completely dissociate in the non-aqueous electrolyte, and the anions and cations are easy to associate , thus causing the ionic conductivity of the non-aqueous electrolyte to decrease, and the capacity retention rate of the secondary battery may become worse.
  • A2/A1 is 5 to 500, 5 to 300, 5 to 250, 5 to 200, 5 to 150, 5 to 100, 5 to 75, 5 to 50, 10 to 500, 10 to 300, 10 to 250,10 to 200,10 to 150,10 to 100,10 to 75,10 to 50,15 to 500,15 to 300,15 to 250,15 to 200,15 to 150,15 to 100,15 to 75 or 15 to 50.
  • the non-aqueous electrolyte may further include a second lithium salt, the second lithium salt including lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluoroxalate phosphate (LiTFOP).
  • the second lithium salt can be used as an auxiliary lithium salt to further improve the interface properties of the positive electrode and/or the negative electrode, or to improve the ionic conductivity or thermal stability of the non-aqueous electrolyte.
  • the total mass percentage of the second lithium salt in the non-aqueous electrolyte is A4%, and A4 is below 5, more optionally below 2, based on the total mass of the non-aqueous electrolyte. .
  • the second lithium salt includes lithium difluorophosphate (LiPO 2 F 2 ), lithium tetrafluorooxalate phosphate (LiTFOP), or a combination thereof, and more optionally, the second lithium salt Salts include lithium difluorophosphate (LiPO 2 F 2 ).
  • Lithium difluorophosphate has high electrochemical stability, can increase the ionic conductivity of the non-aqueous electrolyte, improve the properties of the positive electrode interface film and the negative electrode interface film, and also helps to build a stable and low-impedance positive electrode interface film and The negative electrode interface film can effectively reduce the decomposition of non-aqueous electrolyte and further improve the power performance and safety performance of secondary batteries.
  • the mass ratio ⁇ of lithium difluorophosphate to lithium hexafluorophosphate is 0.01 to 0.15, optionally 0.01 to 0.1.
  • A1+A2+A3+A4 is 10 to 20, optionally 12 to 16.
  • the non-aqueous electrolyte solution includes an organic solvent
  • the organic solvent includes at least one of a cyclic carbonate compound, a chain carbonate compound, and a carboxylate compound.
  • the cyclic carbonate compound may include at least one of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and ethylene ethylene carbonate (VEC).
  • the chain carbonate compound may include ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate ( At least one of MPC) and ethyl propyl carbonate (EPC).
  • the carboxylate compound may include methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), propionic acid At least one of ethyl ester (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).
  • MF methyl formate
  • MA methyl acetate
  • EA ethyl acetate
  • PA propyl acetate
  • MP methyl propionate
  • EP ethyl ester
  • PP propyl propionate
  • MB methyl butyrate
  • EB ethyl butyrate
  • the organic solvent includes at least a cyclic carbonate compound and a chain carbonate compound.
  • a cyclic carbonate compound When the content of lithium salts such as lithium hexafluorophosphate is high, the viscosity of the non-aqueous electrolyte increases and the ionic conductivity decreases, which is not conducive to the transmission of lithium ions.
  • the cyclic carbonate compound can increase the ionic conductivity of the non-aqueous electrolyte due to its high dielectric constant, and the chain carbonate compound can reduce the viscosity of the non-aqueous electrolyte due to its small viscosity. Therefore, when the organic solvent includes both cyclic carbonate compounds and chain carbonate compounds, it helps to make the non-aqueous electrolyte solution have appropriate viscosity and ionic conductivity, which is beneficial to the transport of lithium ions.
  • Cyclic carbonate compounds have a high dielectric constant and help increase the ionic conductivity of non-aqueous electrolytes, but they are prone to decomposition reactions and affect the storage performance of secondary batteries. Therefore, their content needs to be controlled within an appropriate range.
  • the mass percentage of the cyclic carbonate compound is B1%, and B1 is greater than 0 and less than or equal to 20, based on the total mass of the non-aqueous electrolyte.
  • B1 is 0.5 to 20, 1 to 20, 2 to 20, 5 to 20, 10 to 20, 12 to 20, 15 to 20 or 15 to 18.
  • the mass percentage of the chain carbonate compound is B2%, and B2 is 45 to 80, based on the total mass of the non-aqueous electrolyte.
  • B2 is 50 to 80, 55 to 80, 60 to 80 or 60 to 75.
  • Carboxylate compounds have the advantages of low viscosity and high dielectric constant. Their application in non-aqueous electrolytes helps the non-aqueous electrolytes to have appropriate viscosity and ionic conductivity, which is beneficial to the transmission and improvement of lithium ions. Rate performance of secondary batteries. Carboxylate compounds can improve the power performance of secondary batteries, but their oxidation resistance is poor and they are prone to decomposition when stored in a high state of charge, so their content should not be too high.
  • the mass percentage of the carboxylate compound is B3%, and B3 is 0 to 15, based on the total mass of the non-aqueous electrolyte. In some embodiments, B3 may be 0. In some embodiments, optionally, B3 is 2 to 15, 2 to 10, 2 to 8 or 2 to 5.
  • the organic solvent of the present application may also contain other solvents other than the above-mentioned cyclic carbonate compound, chain carbonate compound, and carboxylate compound.
  • the other solvents may include sulfone solvents, such as sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), and the like.
  • the content A1% of the compound represented by Formula 1 and the content B1% of the cyclic carbonate compound satisfy that B1/20+A1 is 1 to 3, optionally 1 to 2, 1 to 1.8, 1 to 1.6, 1 to 1.4.
  • B1/20+A1 is 1 to 3, optionally 1 to 2, 1 to 1.8, 1 to 1.6, 1 to 1.4.
  • a reasonable combination of the content A1% of the compound shown in Formula 1 and the content B1% of the cyclic carbonate compound will help to further improve the power performance and safety hazards caused by thinning of the current collector. Improve the capacity retention rate of secondary batteries.
  • the non-aqueous electrolyte may also include additives, such as halogen-substituted cyclic carbonate compounds, nitrile compounds, phosphazene compounds, aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds, isocyanate compounds, acid anhydride compounds, At least one of a sulfate compound, a sulfite compound, a sulfonate compound, and a disulfonate compound.
  • additives such as halogen-substituted cyclic carbonate compounds, nitrile compounds, phosphazene compounds, aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds, isocyanate compounds, acid anhydride compounds, At least one of a sulfate compound, a sulfite compound, a sulfonate compound, and a disulfonate compound.
  • additives such as halogen-substituted cyclic carbonate compounds, nitrile compounds, phosphazene
  • the non-aqueous electrolyte may also include fluoroethylene carbonate (FEC), the mass percentage of which is C1%, 0 ⁇ C1 ⁇ 2.5, based on the non-aqueous electrolyte total mass.
  • FEC fluoroethylene carbonate
  • C1 is a range consisting of 0, 0.10, 0.20, 0.50, 0.75, 1.0, 1.25, 1.50, 1.75, 2.0, 2.25, 2.50 or any above values.
  • fluorinated ethylene carbonate can undergo a reductive decomposition reaction at a higher potential and form an interface film with a certain degree of flexibility on the surface of the negative active material. It can also inhibit the degradation of organic solvents with lower potentials. Reduce decomposition and inhibit the insertion of organic solvents into the negative active material. Therefore, when the non-aqueous electrolyte contains fluorinated ethylene carbonate, the cycle performance of the secondary battery can be effectively improved.
  • fluorinated ethylene carbonate is resistant to high-pressure oxidation and is conducive to matching high-voltage negative active materials, which is conducive to further improving the energy density of secondary batteries.
  • the content A1% of the compound represented by Formula 1 and the content C1% of fluoroethylene carbonate also satisfy 0.25 ⁇ C1/A1 ⁇ 25.
  • the non-aqueous electrolyte contains fluorinated ethylene carbonate
  • fluorinated ethylene carbonate easily decomposes and forms HF.
  • HF will corrode the positive electrode active material and increase the heat production of the secondary battery. and gas production.
  • the compound shown in Formula 1 can be used as a stabilizer for the cathode active material.
  • the B atoms in its structure have the function of interacting with the O atoms on the surface of the cathode active material, thereby stabilizing the crystal structure of the cathode active material and reducing HF. Destruction of the crystal structure of the cathode active material.
  • the combined use of the compound represented by Formula 1 and fluorinated ethylene carbonate is conducive to fully utilizing the further improvement effect of fluorinated ethylene carbonate on the cycle performance of secondary batteries.
  • the relationship between the content A1% of the compound shown in Formula 1 and the content C1% of fluorinated ethylene carbonate is reasonably controlled to satisfy 0.25 ⁇ C1/A1 ⁇ 25, which can give full play to the compound shown in Formula 1 and the content of fluorinated ethylene carbonate.
  • the synergistic effect of ethylene carbonate helps to further improve the cycle performance of secondary batteries while improving the problems of poor power performance and increased safety hazards caused by thinning of the current collector.
  • fluoroethylene carbonate has a high dielectric constant.
  • the relationship between the content A1% of the compound shown in Formula 1 and the content C1% of fluoroethylene carbonate is reasonably controlled so that it meets 0.25 ⁇ C1/A1 ⁇ 25. It can also ensure that the anions and cations of the compound shown in formula 1 form free ions and reduce the association of anions and cations. On the one hand, it can increase the ionic conductivity of the non-aqueous electrolyte and improve the cycle performance of the secondary battery. On the other hand, it can also increase the activity. Number of lithium ions.
  • the non-aqueous electrolyte may also include a water-removing additive.
  • the water-removing additive helps to reduce the water content of the non-aqueous electrolyte and reduce a series of side reactions caused by moisture, thereby reducing the gas production of the secondary battery. and heat production, so that the secondary battery has better storage performance and safety performance.
  • the water removal additive includes hexamethyldisilazane (HMDS), tris(trimethylsilyl)phosphate (TMSP), or a combination thereof.
  • HMDS hexamethyldisilazane
  • TMSP tris(trimethylsilyl)phosphate
  • these two water-removing additives can also react with lithium hexafluorophosphate and form lithium difluorophosphate.
  • the interface film and/or the negative electrode interface film reduces the positive electrode interface resistance and/or the negative electrode interface resistance, thereby helping to further improve the power performance, storage performance and safety performance of the secondary battery.
  • the mass percentage of the water-removing additive is less than 2%, optionally 0.05% to 1%, more optionally 0.1% to 1%, based on the non-aqueous electrolyte. Total mass meter.
  • the non-aqueous electrolyte solution of the present application can be prepared according to conventional methods in this field.
  • the organic solvent, the lithium salt, the additive, etc. can be mixed uniformly to obtain a non-aqueous electrolyte solution.
  • the order of adding each material is not particularly limited.
  • the lithium salt and the additives can be added to the organic solvent and mixed evenly to obtain a non-aqueous electrolyte.
  • each component and its content in the non-aqueous electrolyte solution can be determined according to methods known in the art. For example, it can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), or the like.
  • GC-MS gas chromatography-mass spectrometry
  • IC ion chromatography
  • LC liquid chromatography
  • NMR nuclear magnetic resonance spectroscopy
  • the non-aqueous electrolyte can be obtained from the secondary battery.
  • An exemplary method of obtaining non-aqueous electrolyte from a secondary battery includes the following steps: discharging the secondary battery to the discharge cutoff voltage (for safety reasons, the battery is generally in a fully discharged state), then centrifuging, and then centrifuging an appropriate amount
  • the liquid obtained by the treatment is the non-aqueous electrolyte.
  • the non-aqueous electrolyte can also be obtained directly from the liquid filling port of the secondary battery.
  • the negative active material layer includes a negative active material
  • the negative active material may be a negative active material for secondary batteries known in the art.
  • the negative active material includes but is not limited to at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitride composite, and silicon alloy material.
  • the tin-based material may include at least one of elemental tin, tin oxide, and tin alloy materials.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries 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 active material layer optionally further includes a negative conductive agent.
  • a negative conductive agent This application has no special limitation on the type of the negative electrode conductive agent.
  • the negative electrode conductive agent may include superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite At least one of alkenes and carbon nanofibers.
  • the mass percentage of the negative conductive agent is less than 5%.
  • the negative active material layer optionally further includes a negative binder.
  • the negative electrode binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, At least one of polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) kind.
  • the mass percentage of the negative electrode binder is less than 5% based on the total mass of the negative electrode active material layer.
  • the negative active material layer optionally further includes other auxiliaries.
  • other auxiliaries may include thickeners, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • the mass percentage of the other additives is less than 2% based on the total mass of the negative active material layer.
  • the negative active material layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying, and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the cathode active material layer includes a cathode active material
  • the cathode active material may be a cathode active material known in the art for secondary batteries.
  • the cathode active material may include at least one of a lithium transition metal oxide, an olivine-structured lithium-containing phosphate, and their respective modified compounds.
  • lithium transition metal oxides may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium At least one of nickel cobalt aluminum oxides and their respective modified compounds.
  • lithium-containing phosphates with an olivine structure may include lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon. At least one of the composite materials and their respective modifying compounds.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for secondary 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.
  • the cathode active material includes a layered material with a molecular formula of Li a Ni b Co c Mn d Ale M f O g A h , where M represents transition metal site doping cations, and A represents oxygen site doping.
  • M represents transition metal site doping cations
  • A represents oxygen site doping.
  • the layered material with the molecular formula Li a Ni b Co c Mn d Al e M f O g A h is optionally modified by M cation doping, A anion doping or simultaneous doping of M cations and A anions. property, the crystal structure of the layered material obtained after doping is more stable, the lattice oxygen is not easy to precipitate, and the transition metal ions are not easy to escape, which can reduce a series of side reactions caused by it, thereby further improving the safety performance and power of secondary batteries. Chemical properties, such as cycle performance, kinetic properties, etc.
  • M is selected from at least one of Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te, and W.
  • A is selected from at least one of F, N, P, and S.
  • A is selected from F.
  • the crystal structure of Li a Ni b Co c Mn d Al e M f O g A h is more stable, the lattice oxygen is not easy to precipitate, and the transition metal ions are not easy to escape, which can make the secondary battery have Better safety performance, cycle performance and dynamic performance.
  • 0 ⁇ b ⁇ 0.98 In some embodiments, 0 ⁇ b ⁇ 0.98. Alternatively, 0.50 ⁇ b ⁇ 0.98, 0.55 ⁇ b ⁇ 0.98, 0.60 ⁇ b ⁇ 0.98, 0.65 ⁇ b ⁇ 0.98, 0.70 ⁇ b ⁇ 0.98, 0.75 ⁇ b ⁇ 0.98 or 0.80 ⁇ b ⁇ 0.98.
  • c 0.
  • 0 ⁇ c ⁇ 0.20 In some embodiments, 0 ⁇ c ⁇ 0.15, 0 ⁇ c ⁇ 0.10, 0 ⁇ c ⁇ 0.09, 0 ⁇ c ⁇ 0.08, 0 ⁇ c ⁇ 0.07, 0 ⁇ c ⁇ 0.06, 0 ⁇ c ⁇ 0.05, 0 ⁇ c ⁇ 0.04, 0 ⁇ c ⁇ 0.03, 0 ⁇ c ⁇ 0.02 or 0 ⁇ c ⁇ 0.01.
  • Cobalt is less abundant in the earth's crust, difficult to mine, and expensive. Therefore, low-cobalt or cobalt-free has become an inevitable development trend for cathode active materials. However, cobalt contributes greatly to the lithium ion diffusion rate of the cathode active material.
  • the inventor of this application also accidentally discovered during the research process that the B atom in the compound structure shown in Formula 1 easily combines with the O atom in the cathode active material, reducing the charge transfer resistance of the cathode active material, thereby reducing the activity of lithium ions in the cathode active material. Diffusion resistance within the bulk phase of a material. Therefore, low-cobalt or cobalt-free cathode active materials can have significantly improved lithium ion diffusion rates. The lithium ions in the bulk phase of low-cobalt or cobalt-free cathode active materials can be replenished to the surface in a timely manner to avoid low-cobalt or cobalt-free cathode active materials.
  • the surface is delithiated, thereby stabilizing the crystal structure of the low-cobalt or cobalt-free cathode active material. Since the crystal structure of the low-cobalt or cobalt-free cathode active material of the present application is more stable, it can greatly reduce the structural properties, chemical properties or electrochemistry of the cathode active material due to excessive delithiation on the surface of the low-cobalt or cobalt-free cathode active material. The probability of problems such as properties becoming unstable, such as irreversible distortion of the cathode active material and increased lattice defects.
  • d 0 and 0 ⁇ e ⁇ 0.50.
  • e 0 and 0 ⁇ d ⁇ 0.50.
  • 0 ⁇ g ⁇ 2, 0 ⁇ h ⁇ 2, and g+h 2.
  • layered materials with the molecular formula Li a Ni b Co c Mn d Al e M f O g A h include but are not limited to LiNi 0.7 Mn 0.3 O 2 , LiNi 0.69 Co 0.01 Mn 0.3 O 2 , LiNi 0.68 Co 0.02 Mn At least one of 0.3 O 2 , LiNi 0.65 Co 0.05 Mn 0.3 O 2 , LiNi 0.63 Co 0.07 Mn 0.3 O 2 , and LiNi 0.61 Co 0.09 Mn 0.3 O 2 .
  • Li a Ni b Co c Mn d Al e M f O g A h can be prepared according to conventional methods in the art.
  • An exemplary preparation method is as follows: a lithium source, a nickel source, a cobalt source, a manganese source, an aluminum source, an M element precursor, and an A element precursor are mixed and then sintered.
  • the sintering atmosphere may be an oxygen-containing atmosphere, such as an air atmosphere or an oxygen atmosphere.
  • the O2 concentration of the sintering atmosphere is, for example, 70% to 100%.
  • the sintering temperature and sintering time can be adjusted according to actual conditions.
  • lithium sources include, but are not limited to, lithium oxide (Li 2 O), lithium phosphate (Li 3 PO 4 ), lithium dihydrogen phosphate (LiH 2 PO 4 ), lithium acetate (CH 3 COOLi), lithium hydroxide (LiOH ), at least one of lithium carbonate (Li 2 CO 3 ) and lithium nitrate (LiNO 3 ).
  • the nickel source includes, but is not limited to, at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate.
  • the cobalt source includes, but is not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate.
  • the manganese source includes, but is not limited to, at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate.
  • the aluminum source includes, but is not limited to, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum oxalate, and aluminum acetate.
  • the M element precursor includes, but is not limited to, at least one of an oxide of the M element, a nitric acid compound, a carbonic acid compound, a hydroxide compound, and an acetic acid compound.
  • precursors of element A include, but are not limited to, ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, phosphoric acid , at least one of ammonium sulfate, ammonium bisulfate, ammonium bisulfite, ammonium sulfite, ammonium bisulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide and elemental sulfur.
  • the content of the layered material with the molecular formula Li a Ni b Co c Mn d Al e M f O g A h is 80% to 99% based on the total mass of the cathode active material layer.
  • the content of a layered material with the molecular formula Li a Ni b Co c Mn d Al e M f O g A h can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87 %, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or any range above.
  • the content of the layered material with the molecular formula Li a Ni b Co c Mn d Al e M f O g A h is 85% to 99%, 90% to 99%, 95% to 99%, 80% to 98%, 85% to 98%, 90% to 98%, 95% to 98%, 80% to 97%, 85% to 97%, 90% to 97% or 95% to 97%.
  • the cathode active material layer optionally further includes a cathode conductive agent.
  • a cathode conductive agent This application has no special limitation on the type of the positive electrode conductive agent.
  • the positive electrode conductive agent includes superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, and graphene. , at least one of carbon nanofibers.
  • the mass percentage of the cathode conductive agent is less than 5% based on the total mass of the cathode active material layer.
  • the cathode active material layer optionally further includes a cathode binder.
  • the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene -At least one of propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • the mass percentage of the cathode binder is less than 5% based on the total mass of the cathode active material layer.
  • the positive electrode active material layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the isolation film is disposed between the positive electrode piece and the negative electrode piece, which mainly serves to prevent short circuit between the positive electrode and the negative electrode, and at the same time allows lithium ions to pass through.
  • the type of isolation membrane in this application and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane may include at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.
  • the isolation film may be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the soft bag may be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), 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. As shown in FIG. 1 , a square-structured secondary battery 5 is shown as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 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 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to 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 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the non-aqueous electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and can be adjusted according to needs.
  • the positive electrode sheet, the separator, the negative electrode sheet, and the non-aqueous electrolyte may be assembled to form a secondary battery.
  • the positive electrode sheet, isolation film, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in an outer package, dried, and then injected with non-aqueous electrolyte. After vacuum packaging, static Through processes such as placement, formation, and shaping, secondary batteries are obtained.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • An embodiment of the present application also provides an electrical device, which includes at least one of a secondary battery, a battery module or a battery pack of 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 electrical device may be, but is not limited to, 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, electric Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the power-consuming device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 6 is a schematic diagram of an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • battery packs or battery modules can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • the secondary batteries of Examples 1 to 30 and Comparative Examples 1 to 4 were all prepared according to the following methods.
  • negative active material graphite binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na), and conductive agent carbon black (Super P) in a mass ratio of 96.2:1.8:1.2:0.8.
  • SBR styrene-butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • Super P conductive agent carbon black
  • a porous polyethylene (PE) film is used as the isolation membrane.
  • the positive electrode sheet, isolation film, and negative electrode sheet are stacked and wound in order to obtain the electrode assembly; the electrode assembly is placed in the outer packaging, dried and injected with non-aqueous electrolyte, followed by vacuum packaging, standing, forming, shaping, etc. process to obtain a secondary battery.
  • the secondary battery At 25°C, charge the secondary battery to 4.25V with a constant current of 0.1C, and continue charging with a constant voltage until the current is 0.05C. At this time, the secondary battery is fully charged; discharge the secondary battery with a constant current of 1C for about 30 seconds. minutes and adjust the state of charge of the secondary battery to 50% SOC. At this time, the voltage of the secondary battery is recorded as V 0 ; discharge the secondary battery with a current I 1 of 4C for 30 seconds, and use the 0.1 second sampling point to determine the voltage at the end of the discharge Denote it as V 1 .
  • the internal resistance of the secondary battery DCR (V 0 -V 1 )/I 1 . The smaller the internal resistance of the secondary battery, the better the power performance.
  • Table 1 shows the preparation parameters of the positive electrode sheet, negative electrode sheet and non-aqueous electrolyte solution of Examples 1 to 30 and Comparative Examples 1 to 4.
  • Table 2 shows the test results obtained according to the above performance test method for Examples 1 to 30 and Comparative Examples 1 to 4.
  • the secondary battery when the secondary battery also uses a thinned positive electrode current collector, by adjusting the content of the compound shown in Formula 1 A1% and the thickness of the positive electrode current collector H2 ⁇ m, the fracture of the positive electrode current collector
  • the secondary battery can have a relatively high performance. It has further improved energy density on the premise of low internal resistance, high hot box safety performance, high capacity retention rate and low volume expansion rate.
  • the compound shown in Formula 1 can also be oxidized on the surface of the cathode active material prior to the organic solvent, and its oxidation product also has low resistance characteristics, thus helping to form a low resistance cathode interface film; at the same time,
  • the B atom in the molecular structure of the compound shown in Formula 1 can also easily combine with inorganic components such as LiF in the positive electrode interface film, which can accelerate lithium ion transport and significantly reduce battery internal resistance and heat production.

Abstract

提供了一种二次电池（5）以及包含其的电池模块（4）、电池包（1）及用电装置。二次电池（5）包括正极极片、负极极片以及非水电解液，非水电解液包括式1化合物，基于非水电解液的总质量计，式1化合物的质量百分含量为A1％，负极集流体的厚度为H1 μm，负极活性材料层的压实密度为P1 g/cm 3，并且二次电池（5）满足：H1为3至7，A1/H1为0.003至0.40和P1/A1为1至90。从而能使采用减薄负极集流体的二次电池（5）同时兼顾低成本、高能量密度、高功率性能和高安全性能。

Description

二次电池以及包含其的电池模块、电池包及用电装置 技术领域
本申请属于电池技术领域，具体涉及一种二次电池以及包含其的电池模块、电池包及用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池的应用及推广，对其能量密度的要求越来越高。铜箔集流体在二次电池并不贡献容量，通过铜箔集流体减薄不仅可以降低成本，还能使有限的电池壳体中容纳更多的活性材料，因此，铜箔集流体减薄是提高二次电池能量密度最有效的措施之一。尽管铜箔集流体减薄可以降低成本并提升二次电池的能量密度，但该方案在工业上却难以实际应用，主要是由于铜箔集流体减薄后，电池内阻和产热量增加。由此，目前二次电池并不能同时兼具低成本、高能量密度以及高功率性能和高安全性能。
发明内容
本申请的目的在于提供一种二次电池以及包含其的电池模块、电池包及用电装置，旨在使采用减薄负极集流体的二次电池同时兼顾低成本、高能量密度、高功率性能和高安全性能。
本申请第一方面提供一种二次电池，包括正极极片、负极极片以及非水电解液，所述正极极片包括正极集流体以及位于所述正极集流体至少一个表面上的正极活性材料层，所述负极极片包括负极集流体以及位于所述负极集流体至少一个表面上的负极活性材料层，其中，所述非水电解液包括式1所示化合物，X、Y各自独立地表示氟原子，或者部分氟化或全部氟化的如下基团组成的组中的至少一种：C1-C10的烷基、C2-C10的烯基、C2-C10的炔基、C6-C8的芳基、C1-C10的烷氧基、C2-C10的烯氧基、C2-C10的炔氧基、C6-C8的芳氧基，并且X、Y中的至少一者表示氟原子；
Figure PCTCN2022094511-appb-000001
基于所述非水电解液的总质量计，所述式1所示化合物的质量百分含量为A1％，所述负极集流体的厚度为H1 μm，所述负极活性材料层的压实密度为P1 g/cm 3，并且所述二次电池满足：H1为3至7，A1/H1为0.003至0.40和P1/A1为1至90。
本申请的发明人在研究过程中发现，在采用减薄负极集流体的二次电池中，当非水电解液含有式1所示化合物并且通过控制其含量A1％与负极集流体的厚度H1μm和负极活性材料层的压实密度P1g/cm 3之间的关系，使二次电池满足A1/H1为0.003至0.40和P1/A1为1至90时，二次电池能同时兼顾低成本、高能量密度、高功率性能和高安全性能。
在本申请的任意实施方式中，可选地，A1/H1为0.003至0.1，更可选地为0.003至0.08。由此能够使二次电池同时具有高功率性能和高安全性能。
在本申请的任意实施方式中，可选地，P1/A1为3至90，更可选地为5至90。由此能够使二次电池同时具有高功率性能和高安全性能。
在本申请的任意实施方式中，所述正极集流体的厚度为H2μm、所述正极集流体的断裂延伸率为Q％，所述正极活性材料层的压实密度为P2g/cm 3，并且所述二次电池满足：H2为4至14，A1/H2为0.0015至0.20，Q+A1为1至4和P2/A1为2至340。
本申请的发明人在进一步研究过程中还发现，当式1所示化合物的含量A1％与正极集流体的厚度H2μm、正极集流体的断裂延伸率Q％和正极活性材料层的压实密度P2g/cm 3进一步满足H2为4至14，A1/H2为0.0015至0.20，Q+A1为1至4和P2/A1为2至340时，有助于改善正极集流体减薄后对二次电池功率性能、安全性能和加工性能的负面影响。
在本申请的任意实施方式中，可选地，A1/H2为0.002至0.05，更可选地为0.01至0.05。由此有助于提高正极集流体的强度，改善正极极片的加工性能，减少甚至避免断带情况发生；同时有助于二次电池具有高功率性能和高安全性能。
在本申请的任意实施方式中，可选地，Q+A1为1.5至3.5，更可选地为2.0至3.5。由此有助于提高正极集流体的强度，改善正极极片的加工性能，减少甚至避免断带情况发生；同时有助于二次电池具有高功率性能和高安全性能。
在本申请的任意实施方式中，可选地，P2/A1为5至340，更可选地为10至340。由此有助于提升二次电池的功率性能和安全性能。
在本申请的任意实施方式中，可选地，A1为0.02至1.6，更可选地为0.02至0.5。由此能够改善负极集流体和正极集流体减薄后带来的功率性能变差、安全隐患增加、加工性能变差等缺陷。
在本申请的任意实施方式中，可选地，P1为1.4至1.8，更可选地为1.55至1.75。由此有助于提升二次电池的能量密度。
在本申请的任意实施方式中，可选地，P2为3.2至3.7，更可选地为3.4至3.7。由此有助于提升二次电池的能量密度。
在本申请的任意实施方式中，可选地，Q为0.5至3.5，更可选地为1.5至3.5。由此正极集流体具有较高的强度以及良好的加工性能，不易断带。
在本申请的任意实施方式中，可选地，所述非水电解液还包括第一锂盐，所述第一锂盐包括六氟磷酸锂，所述六氟磷酸锂的质量百分含量为A2％，基于所述非水电解液的总质量计。可选地，A2/A1为5至650，更可选地为15至300。由此有助于在改善集流体减薄后带来的功率性能变差、安全隐患增加等问题的前提下进一步改善二次电池的容量保持率。
在本申请的任意实施方式中，可选地，A2为6至14。
在本申请的任意实施方式中，可选地，所述非水电解液还包括第一锂盐，所述第一锂盐包括六氟磷酸锂和双氟磺酰亚胺锂的组合，所述六氟磷酸锂的质量百分含量为A2％，所述双氟磺酰亚胺锂的质量百分含量为A3％，均基于所述非水电解液的总质量计。可选地，A2为6至14，A3大于0且小于等于5。
可选地，A3/A2在0.8以下，更可选地为0.05至0.3。由此有助于形成阻抗更低的界面膜。
可选地，A2/A1为5至650，更可选地为15至300。由此有助于在改善集流体减薄后带来的功率性能变差、安全隐患增加等问题的前提下进一步改善二次电池的容量保持率。
在本申请的任意实施方式中，可选地，所述非水电解液还包括第二锂盐，所述第二锂盐包括四氟硼酸锂、高氯酸锂、六氟砷酸锂、二氟磷酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种，所述第二锂盐在所述非水电解液中的总质量百分含量为A4％，基于所述非水电解液的总质量计。可选地，A4在5以下，更可选地在2以下。第二锂盐可以作为辅助锂盐，起到进一步改善正极和/或负极的界面性能、或者改善非水电解液的离子电导率或热稳定性的作用。
本申请的任意实施方式中，可选地，所述第二锂盐包括二氟磷酸锂，可选地，所述二氟磷酸锂与所述六氟磷酸锂的质量比α为0.01至0.15，更可选地为0.01至0.1。二氟磷酸锂具有较高的电化学稳定性，能够提高非水电解液的离子电导率，改善正极界面膜和负极界面膜的性质，并还有助于构建稳定且低阻抗的正极界面膜和负极界面膜，从而有效减少非水电解液的分解，进一步改善二次电池的功率性能和安全性能。
在本申请的任意实施方式中，可选地，所述非水电解液还包括环状碳酸酯化合物，所述环状碳酸酯化合物的质量百分含量为B1％，基于所述非水电解液的总质量计。可选地，B1为0.5至20，更可选地为15至18。
在本申请的任意实施方式中，可选地，B1/20+A1为1至3，更可选地为1至2。由此有助于在改善集流体减薄后带来的功率性能变差、安全隐患增加等问题的前提下进一步改善二次电池的容量保持率。
本申请的任意实施方式中，可选地，所述环状碳酸酯化合物包括碳酸乙烯酯、碳酸丙烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯中的至少一种。
在本申请的任意实施方式中，可选地，所述非水电解液还包括氟代碳酸乙烯酯，其质量百分含量为C1％，基于所述非水电解液的总质量计。可选地，0＜C1≤2.5，更可选地，0＜C1≤2.0。由此能有效提升二次电池的循环性能。
在本申请的任意实施方式中，可选地，0.25≤C1/A1≤25，更可选地，0.5≤C1/A1≤10。由此有助于在改善集流体减薄后带来的功率性能变差、安全隐患增加等问题的前提下，进一步改善二次电池的循环性能。
在本申请的任意实施方式中，可选地，所述非水电解液还包括除水添加剂，所述除水添加剂包括六甲基二硅氮烷、三(三甲基硅基)磷酸酯中的至少一种。可选地，所述除水添加剂的质量百分含量在2％以下，更可选地为0.05％至1％，基于所述非水电解液的总质量计。由此有助于进一步提升二次电池的功率性能、存储性能和安全性能。
在本申请的任意实施方式中，可选地，X、Y均表示氟原子。
在本申请的任意实施方式中，可选地，X、Y中的一者表示氟原子，另一者表示部分氟化或全部氟化的如下基团组成的组中的至少一种：C1-C5的烷基、C2-C5的烯基、C2-C5的炔基、苯基、苯氧基、C1-C5的烷氧基、C2-C5的烯氧基和C2-C5的炔氧基。
在本申请的任意实施方式中，可选地，X、Y中的一者表示氟原子，另一者表示部分氟化或全部氟化的如下基团组成的组中的至少一种：甲基、乙基、正丙基、异丙基、正丁基、叔丁基、乙烯基、丙烯基、烯丙基、丁二烯基、乙炔基、丙炔基、苯基、甲氧基、乙氧基、丙氧基、乙烯氧基、丙烯氧基、乙炔氧基、丙炔氧基和苯氧基。
氟原子的存在有助于形成更薄的正极界面膜和/或负极界面膜，从而有助于锂离子的均匀传输，并还能有效抑制锂枝晶形成。
在本申请的任意实施方式中，可选地，所述式1所示化合物包括如下化合物中的至少一种，
Figure PCTCN2022094511-appb-000002
在本申请的任意实施方式中，可选地，所述负极集流体采用铜箔或铜合金箔。
在本申请的任意实施方式中，可选地，所述正极集流体采用铝箔或铝合金箔。
本申请第二方面提供一种电池模块，其包括本申请第一方面的二次电池。
本申请第三方面提供一种电池包，其包括本申请第一方面的二次电池、第二方面的电池模块中的一种。
本申请第四方面提供一种用电装置，其包括本申请第一方面的二次电池、第二方面的电池模块、第三方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
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方式，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是本申请的二次电池的一实施方式的示意图。
图2是图1的二次电池的实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
在附图中，附图未必按照实际的比例绘制。附图标记说明如下：1电池包，2上箱体，3下箱体，4电池模块，5二次电池，51壳体，52电极组件，53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池以及包含其的电池模块、电池包及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，并且这样的技术方案应被认为包含在本申请的公开内容中。
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，并且这样的技术方案应被认为包含在本申请的公开内容中。
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，所述方法包括步骤(a)和(b)，表示所述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，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(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，所述“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)。
在本说明书的各处，化合物的取代基以组或范围公开。明确地预期这种描述包括这些组和范围的成员的每一个单独的子组合。例如，明确地预期术语“C1-C6的烷基”单独地公开C1、C2、C3、C4、C5、C6、C1-C6、C1-C5、C1-C4、C1-C3、C1-C2、C2-C6、C2-C5、C2-C4、C2-C3、C3-C6、C3-C5、C3-C4、C4-C6、C4-C5和C5-C6的烷基。
在本申请中，术语“多个”、“多种”是指两个或两种以上。
在本申请中，集流体和活性材料层的厚度为本领域公知的含义，可采用本领域已知的方法进行测试。例如采用螺旋测微仪进行测定。
在本申请中，活性材料层的压实密度为本领域公知的含义，可采用本领域已知的方法进行测试。活性材料层的压实密度＝活性材料层的面密度/活性材料层的厚度。活性材料层的面密度为本领域公知的含义，可采用本领域已知的方法进行测试，例如取单面涂布且经冷压后的电极片(若是双面涂布的电极片，可先擦拭掉其中一面的活性材料层)，冲切成面积为S 0的小圆片，称其重量，记录为M 1；然后将上述称重后的电极片的活性材料层擦拭掉，称量集流体的重量，记录为M 0，活性材料层的面密度＝(M 1-M 0)/S 0。
在本申请中，正极集流体的断裂延伸率是指室温下的断裂延伸率。
铜箔集流体是二次电池必不可少的组成部件之一，而为了进一步提高二次电池的能量密度，铜箔集流体减薄依然是目前最有效的措施之一。尽管铜箔集流体减薄可以降低成本并提升二次电池的能量密度，但该方案在工业上却难以实际应用。主要原因包括如下几点：第一，铜箔集流体减薄后，铜箔电阻增加，由此导致电池内阻增加、功率性能变差；第二，由于铜箔是一种良好的热导体材料，其减薄后会导致二次电池产热量增加、散热困难，由此增加二次电池的安全隐患。
此外，高功率型电池在使用中要求放电电流较大，因此放电过程中产热量较高，高温下非水电解液在正极和负极界面的分解反应显著增加，由此引起正极界面阻抗和负极界面阻抗显著增加，二次电池功率性能变差。目前，为了获得高功率型电池，铜箔集流体加厚是常用的措施之一。
因此，目前通过负极集流体减薄提高二次电池能量密度的方案在实际应用中尚面临诸多困难，例如功率性能变差、安全隐患增加等。
本申请的发明人在研究过程中惊喜发现，通过采用合适的非水电解液能够解决负极集流体减薄后带来的功率性能变差、安全隐患增加等问题，从而能使二次电池同时兼顾低成本、高能量密度、高功率性能和高安全性能。
具体地，本申请实施方式提供了一种二次电池。
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。本申请的二次电池可为锂二次电池，特别地可为锂离子二次电池。二次电池包括电极组件、非水电解液以及外包装，外包装用于封装电极组件和 非水电解液。电极组件通常包括正极极片，电极组件还可以包括负极极片和隔离膜。隔离膜设置在正极极片和负极极片之间，主要起到防止正极和负极短路的作用，同时可以使锂离子通过。在一些实施例中，所述正极极片、所述隔离膜和所述负极极片可通过卷绕工艺或叠片工艺制成电极组件。
所述正极极片包括正极集流体以及位于所述正极集流体至少一个表面上的正极活性材料层，例如，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极活性材料层设置于所述正极集流体的两个相对表面中的任意一者或两者上。所述负极极片包括负极集流体以及位于所述负极集流体至少一个表面上的负极活性材料层，例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极活性材料层设置在所述负极集流体的两个相对表面中的任意一者或两者上。在二次电池充放电过程中，锂离子在正极极片和负极极片之间往返嵌入和脱出。非水电解液包括锂盐和有机溶剂，用于在正极极片和负极极片之间起到传导锂离子的作用。
在本申请的二次电池中，所述非水电解液包括式1所示化合物，X、Y各自独立地表示氟原子，或者部分氟化或全部氟化的如下基团组成的组中的至少一种：C1-C10的烷基、C2-C10的烯基、C2-C10的炔基、C6-C8的芳基、C1-C10的烷氧基、C2-C10的烯氧基、C2-C10的炔氧基、C6-C8的芳氧基，并且X、Y中的至少一者表示氟原子。
Figure PCTCN2022094511-appb-000003
基于所述非水电解液的总质量计，所述式1所示化合物的质量百分含量为A1％，所述负极集流体的厚度为H1μm，所述负极活性材料层的压实密度为P1g/cm 3，并且所述二次电池满足：H1为3至7，A1/H1为0.003至0.40和P1/A1为1至90。
在本申请中，负极集流体的厚度H1μm满足H1在3至7之间，可选地，H1可以在3至6.5之间，在3至6之间，3至5.5之间或3至5之间。
本申请的发明人在研究过程中发现，在采用减薄负极集流体的二次电池中，当非水电解液含有式1所示化合物并且通过控制其含量A1％与负极集流体的厚度H1μm和负极活性材料层的压实密度P1g/cm 3之间的关系，使二次电池满足A1/H1为0.003至0.40和P1/A1为1至90时，二次电池能同时兼顾低成本、高能量密度、高功率性能和高安全性能。
尽管机理尚不明确，发明人推测可能的原因包括如下几点。
第一，式1所示化合物分子结构中含有氟原子，其能优先于有机溶剂在负极活性材料表面被还原，并且其还原产物还具体低阻抗的特性，由此有助于形成低阻抗的负极界面膜；同时，式1所示化合物分子结构中的B原子还易与负极界面膜中的LiF等无机组分牢固地结合，由此可加快锂离子传输并明显降低电池内阻，使二次电池在具有高能量密度的同时还具有高功率性能，能够进行大电流放电。
第二，式1所示化合物自身热稳定性较高，例如优于常见的LiPF 6，从而有助于提高非水电解液整体的耐热性；同时式1所示化合物对水分不如LiPF 6敏感，从而还有助于 提高非水电解液的耐水性，减少HF形成并降低非水电解液酸度。因此，本申请的非水电解液可具有较高的热稳定性和电化学稳定性，由此能够减少高温下非水电解液的分解反应，降低电池内阻。根据焦耳定律还可知，二次电池的产热量与电池内阻直接相关，因此电池内阻降低后，二次电池的产热量也降低，进而能使二次电池在具有高能量密度的同时还具有高功率性能和高安全性能。
第三，发明人还惊喜发现，由于式1所示化合物中的阴离子半径较大，容易被还原，因此从其分子结构中解离出的锂离子还可以成为活性锂离子，贡献部分容量，从而有助于提高二次电池的能量密度。
因此，当非水电解液中含有式1所示化合物时，有助于在负极活性材料表面形成低阻抗的界面膜，改善二次电池的功率性能和安全性能，同时还有助于增加活性锂离子数量，贡献部分容量。但是，本申请的发明人在进一步研究中发现，式1所示化合物的含量还需要与负极集流体的厚度和负极活性材料层的压实密度进行合理搭配，以有效降低负极集流体减薄后对功率性能和安全性能的负面影响，使二次电池同时兼顾低成本、高能量密度、高功率性能和高安全性能。
在本申请中，式1所示化合物的含量A1％与负极集流体的厚度H1μm满足A1/H1在0.003至0.40之间。A1/H1小于0.003时，负极集流体较厚而式1所示化合物含量较低，不能形成低阻抗的负极界面膜，由此负极界面阻抗较高，不能有效降低负极集流体减薄对电池内阻和产热量的恶化，因此，二次电池的功率性能和安全性能较差，同时式1所示化合物也不能起到贡献活性锂离子的作用；A1/H1大于0.40时，负极集流体较薄而式1所示化合物含量较高，导致形成过厚的负极界面膜，由此负极界面阻抗也较高，进而电池内阻和产热量较高，二次电池的功率性能和安全性能较差。可选地，A1/H1为0.003至0.30，0.003至0.25，0.003至0.20，0.003至0.16，0.003至0.12，0.003至0.10，0.003至0.08，0.003至0.06，0.01至0.30，0.01至0.25，0.01至0.20，0.01至0.16，0.01至0.12，0.01至0.10，0.01至0.08或0.01至0.06。
在本申请中，式1所示化合物的含量A1％与负极活性材料层的压实密度P1g/cm 3满足P1/A1在1至90之间，由此，式1所示化合物有助于在负极活性材料表面形成低阻抗的界面膜，一方面有助于增加锂离子传输，另一方面能够降低负极界面阻抗，从而能够有效降低负极集流体减薄对电池内阻和产热量的恶化，使二次电池同时具有高功率性能和高安全性能。P1/A1小于1时，负极活性材料层的压实密度较小而式1所示化合物含量较高，导致形成过厚的负极界面膜，由此负极界面阻抗较高，进而电池内阻和产热量较高，二次电池的功率性能和安全性能较差；P1/A1大于90时，负极活性材料层的压实密度较大而式1所示化合物含量较低，从而没有足够的式1所示化合物在负极活性材料表面形成低阻抗的界面膜，不能有效降低负极集流体减薄对电池内阻和产热量的恶化，因此，二次电池的功率性能和安全性能较差。可选地，P1/A1为1.5至90，1.5至75，1.5至50，1.5至35，1.5至30，1.5至25，1.5至20，1.5至15，1.5至10，3至90，3至75，3至50，3至35，3至30，3至25，3至20，3至15，3至10，5至90，5至75，5至50，5至35，5至30，5至25，5至20，5至15或5至10。
在一些实施例中，所述负极集流体采用铜箔或铜合金箔。所述铜箔可以为压延铜箔或电解铜箔。作为铜合金箔可以采用Cu-Ag、Cu-Te、Cu-Mg、Cu-Sn、Cu-Si、Cu-Mn、 Cu-Be-Co、Cu-Ti、Cu-Ni-Si、Cu-Cr、Cu-Zr、Cu-Fe、Cu-Al、Cu-Zn、Cu-Co等合金箔。
在一些实施例中，所述正极集流体的厚度为H2μm，H2为4至14，可选地，H2可以为4至13，4至12，4至11，4至10，4至9或4至8。
通过正极集流体减薄有助于进一提升二次电池的能量密度。但是，正极集流体减薄后，电阻和产热量增加，由此导致二次电池的功率性能和安全性能较差；此外，铝箔集流体减薄后，其自身强度变差，同时为了进一步提高二次电池的能量密度，减薄的正极集流体通常搭配较高的压实密度使用，从而在辊压过程中容易出现正极极片被压断情况，由此还会影响正极极片和二次电池的加工性能。
本申请的发明人在进一步研究过程中还发现，当式1所示化合物的含量A1％与正极集流体的厚度H2μm、正极集流体的断裂延伸率Q％和正极活性材料层的压实密度P2g/cm 3进一步满足H2为4至14，A1/H2为0.0015至0.20，Q+A1为1至4和P2/A1为2至340时，有助于改善正极集流体减薄后对二次电池功率性能、安全性能和加工性能的负面影响。
可能的原因在于，式1所示化合物分子结构中含有草酸根基团，其还能优先于有机溶剂在正极活性材料表面被氧化，并且其氧化产物还具体低阻抗的特性，由此有助于形成低阻抗的正极界面膜；同时，式1所示化合物分子结构中的B原子还易与正极界面膜中的LiF等无机组分牢固地结合，由此可加快锂离子传输并明显降低电池内阻和产热量；此外，式1所示化合物分子结构中的B-O键能与Al 3+键合并在正极集流体表面形成一层钝化膜，从而有助于提高正极集流体的强度，改善正极极片的加工性能，减少甚至避免断带情况发生。
可选地，式1所示化合物的含量A1％与正极集流体的厚度H2μm满足A1/H2在0.0015至0.20之间，由此，式1所示化合物分子结构中的B-O键能与Al 3+更好地键合并在正极集流体表面形成具有合适厚度的钝化膜，从而有助于提高正极集流体的强度，改善正极极片的加工性能，减少甚至避免断带情况发生。并且能够有效避免以下情况：A1/H2小于0.0015时，可能没有足够的式1所示化合物与Al 3+键合并在正极集流体表面形成钝化膜，由此正极极片和二次电池的加工性能可能较差；A1/H2大于0.20时，式1所示化合物含量较高，可能形成较厚的正极界面膜，导致正极界面阻抗可能增加，由此导致电池内阻和产热量较高，二次电池的功率性能和安全性能可能变差。更可选地，A1/H2为0.002至0.15，0.002至0.1，0.002至0.08，0.002至0.07，0.002至0.06，0.002至0.05，0.005至0.15，0.005至0.1，0.005至0.08，0.005至0.07，0.005至0.06，0.005至0.05，0.01至0.15，0.01至0.1，0.01至0.08，0.01至0.07，0.01至0.06或0.01至0.05。
可选地，式1所示化合物的含量A1％与正极集流体的断裂延伸率Q％满足Q+A1在1至4之间，由此，式1所示化合物分子结构中的B-O键能与Al 3+更好地键合并在正极集流体表面形成具有合适厚度的钝化膜，从而有助于提高正极集流体的强度，改善正极极片的加工性能，减少甚至避免断带情况发生。并且能够有效避免以下情况：Q+A1小于1时，可能没有足够的式1所示化合物与Al 3+键合并在正极集流体表面形成钝化膜，同时正极集流体的延展性较差，辊压过程过程中易出现断带情况，导致二次电池的加工性能可能较差；Q+A1大于4时，正极集流体的延展性高、耐压性好，但是其不耐穿刺，在受到尖锐物质挤压时容易破损并出现较大的毛刺，引起电池内短路风险较高，由此二次电 池的安全性能可能较差，同时较多的式1所示化合物还会形成较厚的界面膜，导致正极界面阻抗较高，由此还可能影响二次电池的功率性能和安全性能。更可选地，Q+A1为1.5至4，1.8至4，2.0至4，2.2至4，2.4至4，2.6至4，2.8至4，3.0至4，1.5至3.5，1.8至3.5，2.0至3.5，2.2至3.5，2.4至3.5，2.6至3.5，2.8至3.5或3.0至3.5。
可选地，式1所示化合物的含量A1％与正极活性材料层的压实密度P2g/cm 3满足P2/A1在2至340之间，由此，式1所示化合物有助于在正极活性材料表面形成低阻抗的界面膜，降低正极界面阻抗；同时还有助于式1所示化合物分子结构中的B原子与正极活性材料中的O原子更好地结合，由此还能降低正极活性材料的电荷转移阻抗和锂离子体相扩散阻力，从而能够降低电池内阻和产热量并提升二次电池的功率性能和安全性能。并且能够有效避免以下情况：P2/A1小于2时，可能形成较厚的正极界面膜，导致正极界面阻抗较高，电池内阻和产热量较高，二次电池的功率性能和安全性能可能变差；P2/A1大于340时，可能没有足够的式1所示化合物在正极活性材料表面形成低阻抗的界面膜，并且正极活性材料的电荷转移阻抗以及锂离子体相扩散阻力较高，由此导致电池内阻和产热量较高，从而二次电池的功率性能和安全性能可能较差。更可选地，P2/A1为2至200，2至100，2至75，2至50，2至35，2至30，2至25，2至20，2至15，3.5至340，3.5至200，3.5至100，3.5至75，3.5至50，3.5至35，3.5至30，3.5至25，3.5至20，3.5至15，5至340，5至200，5至100，5至75，5至50，5至35，5至30，5至25，5至20，10至340，10至200，10至100，10至75，10至50，10至35，10至30，10至25或10至20。
可选地，在一些实施例中，式1所示化合物的含量A1％与正极集流体的厚度H2μm、正极集流体的断裂延伸率Q％和正极活性材料层的压实密度P2g/cm 3进一步满足H2为4至11，A1/H2为0.006至0.1，Q+A1为1.5至3.5和P2/A1为2至340。更可选地，式1所示化合物的含量A1％与正极集流体的厚度H2μm、正极集流体的断裂延伸率Q％和正极活性材料层的压实密度P2g/cm 3进一步满足H2为4至11，A1/H2为0.01至0.05，Q+A1为1.5至3.5和P2/A1为5至75。
在一些实施例中，所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔或铝合金箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的至少一种。作为示例，高分子材料基层可选自聚丙烯(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。
可选地，在一些实施例中，所述正极集流体采用铝箔或铝合金箔。为了提高正极集流体的耐蚀性和强度，可选地，采用纯度为99.99％以上的铝箔。作为铝合金箔，除包含铝元素外，还包含铁、镁、锌、锰和硅中的至少一种元素，例如，铝合金箔可为Al-Fe合金箔、Al-Mn合金箔或Al-Mg合金箔。铝合金箔中铝元素的质量百分含量可选地为95％至99.5％，更可选地为98％至99.5％。
在一些实施例中，式1所示化合物的含量A1％满足A1为0.02至1.8。可选地，A1为0.02至1.6，0.02至1.4，0.02至1.2，0.02至1.0，0.02至0.8，0.02至0.7，0.02至0.6，0.02至0.5，0.05至1.6，0.05至1.4，0.05至1.2，0.05至1.0，0.05至0.8，0.05至 0.7，0.05至0.6，0.05至0.5，0.1至1.6，0.1至1.4，0.1至1.2，0.1至1.0，0.1至0.8，0.1至0.7，0.1至0.6或0.1至0.5。式1所示化合物含量在合适范围内时，能够形成低阻抗的正极界面膜和/或负极界面膜，并还能在正极集流体表面形成具有合适厚度的钝化膜，由此改善负极集流体和正极集流体减薄后带来的功率性能变差、安全隐患增加、加工性能变差等缺陷。
在一些实施例中，负极活性材料层的压实密度P1g/cm 3满足P1为1.4至1.8。可选地，P1为1.4至1.75，1.4至1.7，1.4至1.65，1.4至1.6，1.55至1.8，1.55至1.75，1.55至1.7，1.55至1.65或1.55至1.6。负极活性材料层的压实密度在较高的范围内时，有助于提升二次电池的能量密度。
在一些实施例中，正极活性材料层的压实密度P2g/cm 3满足P2为3.2至3.7。可选地，P2为3.3至3.7，3.4至3.7，3.5至3.7，3.2至3.6，3.3至3.6，3.4至3.6或3.5至3.6。正极活性材料层的压实密度在较高的范围内时，有助于提升二次电池的能量密度。
在一些实施例中，正极集流体的断裂延伸率Q％满足Q为0.5至3.5。可选地，Q为1至3.5，1.5至3.5，1.8至3.5，2.0至3.5，2.2至3.5，2.4至3.5，2.6至3.5，2.8至3.5或3.0至3.5。正极集流体的断裂延伸率在合适的范围内时，正极集流体具有较高的强度以及良好的加工性能，不易断带。
在本申请中，X、Y中的至少一者表示氟原子，氟原子的存在有助于形成更薄的正极界面膜和/或负极界面膜，从而有助于锂离子的均匀传输，并还能有效抑制锂枝晶形成。在一些实施例中，X、Y中的一者表示氟原子，另一者表示部分氟化或全部氟化的如下基团组成的组中的至少一种：C1-C5的烷基、C2-C5的烯基、C2-C5的炔基、苯基、苯氧基、C1-C5的烷氧基、C2-C5的烯氧基和C2-C5的炔氧基。可选地，X、Y中的一者表示氟原子，另一者表示部分氟化或全部氟化的如下基团组成的组中的至少一种：甲基、乙基、正丙基、异丙基、正丁基、叔丁基、乙烯基、丙烯基、烯丙基、丁二烯基、乙炔基、丙炔基、苯基、甲氧基、乙氧基、丙氧基、乙烯氧基、丙烯氧基、乙炔氧基、丙炔氧基和苯氧基。
在一些实施例中，X、Y均表示氟原子。
作为示例，所述式1所示化合物包括如下化合物中的至少一种，
Figure PCTCN2022094511-appb-000004
Figure PCTCN2022094511-appb-000005
[锂盐]
在一些实施例中，所述非水电解液还包括包括第一锂盐，所述第一锂盐包括六氟磷酸锂(LiPF 6)或六氟磷酸锂(LiPF 6)和双氟磺酰亚胺锂(LiFSI)的组合。六氟磷酸锂具有离子电导率高的特性，由此当其含量在合适的范围内时，有助于提高非水电解液整体的离子电导率，加速锂离子传输，提高二次电池的容量保持率。但是六氟磷酸锂在高温环境下的热稳定性较差，其在较高温度下会分解生成PF 5。PF 5与水反应形成HF，容易腐蚀正极活性材料并增加电池胀气。当非水电解液同时含有式1所示化合物和六氟磷酸锂时，式1所示化合物可以与六氟磷酸锂反应形成化合物LiPF 4C 2O 4，由此减少部分六氟磷酸锂的分解和HF的形成，进而二次电池还能具有良好的循环性能。双氟磺酰亚胺锂的化学式为F 2NO 4S 2﹒Li，N原子与两个吸电子的磺酰基团相连，由此使得N原子上的电荷得到了充分离域，进而双氟磺酰亚胺锂具有较低的晶格能、容易解离，从而能够提高非水电解液的离子电导率、降低非水电解液的粘度；此外，双氟磺酰亚胺锂还具有耐高温性好、不易水解的特性，能在负极活性材料表面形成更薄、阻抗更低且热稳定性更高的界面膜，从而减少负极活性材料与非水电解液之间的副反应。但是，双氟磺酰亚胺锂容易腐蚀正极集流体，因此其含量不宜太高。
在一些实施例中，可选地，所述六氟磷酸锂的质量百分含量为A2％，A2为6至14，基于所述非水电解液的总质量计。更可选地，A2为6至12，6至10，8至14，8至12或8至10。
在一些实施例中，可选地，所述双氟磺酰亚胺锂的质量百分含量为A3％，A3大于0且小于等于5，基于所述非水电解液的总质量计。更可选地，A3为0.1至2.5，0.1至2，0.1至1.5，0.1至1，0.2至2.5，0.2至2，0.2至1.5，0.2至1，0.5至2.5，0.5至2，0.5至1.5或0.5至1。
在一些实施例中，可选地，A3/A2在0.8以下，更可选地为0.01至0.8，0.05至0.8，0.1至0.8，0.01至0.6，0.05至0.6，0.1至0.6，0.01至0.4，0.05至0.4，0.1至0.4，0.01至0.3，0.05至0.3或0.1至0.3。由此所述非水电解液不易水解，并且还能够兼顾更高的热稳定性，同时，有助于形成阻抗更低的界面膜。
在一些实施例中，A2/A1为5至650，基于所述非水电解液的总质量计。六氟磷酸锂具有离子电导率高的特性，将式1所示化合物的含量A1％和六氟磷酸锂的含量A2％合理搭配后，有助于在改善集流体减薄后带来的功率性能变差、安全隐患增加等问题的前提下进一步改善二次电池的容量保持率。并且能够有效避免以下情况：六氟磷酸锂的含量较高而式1所示化合物含量较低时，非水电解液可能存在较多PF 5，由此导致非水电解液的分解反应较多，同时式1所示化合物在正极和/或负极形成的界面膜不够均匀致密，无法阻止HF对正极活性材料等的腐蚀以及由此引发的一系列副反应，进而二次电池产气量和产热量较高，功率性能、存储性能和安全性能可能变差；六氟磷酸锂的含量较低而式1所示化合物含量较高时，由于式1所示化合物在非水电解液中不易完全解离，并且阴 阳离子容易缔合，由此导致非水电解液的离子电导率下降，二次电池的容量保持率可能变差。可选地，A2/A1为5至500，5至300，5至250，5至200，5至150，5至100，5至75，5至50，10至500，10至300，10至250，10至200，10至150，10至100，10至75，10至50，15至500，15至300，15至250，15至200，15至150，15至100，15至75或15至50。
在一些实施例中，所述非水电解液还可以包括第二锂盐，所述第二锂盐包括四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的至少一种。第二锂盐可以作为辅助锂盐，起到进一步改善正极和/或负极的界面性能、或者改善非水电解液的离子电导率或热稳定性的作用。
可选地，第二锂盐在所述非水电解液中的总质量百分含量为A4％，A4在5以下，更可选地在2以下，基于所述非水电解液的总质量计。
可选地，在一些实施例中，所述第二锂盐包括二氟磷酸锂(LiPO 2F 2)、四氟草酸磷酸锂(LiTFOP)或其组合，更可选地，所述第二锂盐包括二氟磷酸锂(LiPO 2F 2)。二氟磷酸锂具有较高的电化学稳定性，能够提高非水电解液的离子电导率，改善正极界面膜和负极界面膜的性质，并还有助于构建稳定且低阻抗的正极界面膜和负极界面膜，从而有效减少非水电解液的分解，进一步改善二次电池的功率性能和安全性能。可选地，二氟磷酸锂与六氟磷酸锂的质量比α为0.01至0.15，可选地为0.01至0.1。
在一些实施例中，A1+A2+A3+A4为10至20，可选地为12至16。
[有机溶剂]
在一些实施例中，所述非水电解液包括有机溶剂，所述有机溶剂包括环状碳酸酯化合物、链状碳酸酯化合物、羧酸酯化合物中的至少一种。可选地，所述环状碳酸酯化合物可以包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)中的至少一种。可选地，所述链状碳酸酯化合物可以包括碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)中的至少一种。可选地，所述羧酸酯化合物可以包括甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)中的至少一种。
可选地，在一些实施例中，所述有机溶剂至少包括环状碳酸酯化合物和链状碳酸酯化合物。六氟磷酸锂等锂盐含量较高时，非水电解液的粘度增加、离子电导率降低，不利于锂离子的传输。而环状碳酸酯化合物由于具有较高的介电常数，可以增加非水电解液的离子电导率，链状碳酸酯化合物由于具有较小的粘度，可以降低非水电解液的粘度。因此，当有机溶剂同时包括环状碳酸酯化合物和链状碳酸酯化合物时，有助于使非水电解液具有合适的粘度和离子电导率，进而有利于锂离子的传输。
环状碳酸酯化合物具有较高的介电常数，有助于增加非水电解液的离子电导率，但容易发生分解反应，影响二次电池的存储性能，因此，其含量需要控制在合适的范围内。在一些实施例中，所述环状碳酸酯化合物的质量百分含量为B1％，B1大于0且小于等于20，基于所述非水电解液的总质量计。可选地，B1为0.5至20，1至20，2至20，5 至20，10至20，12至20，15至20或15至18。
在一些实施例中，所述链状碳酸酯化合物的质量百分含量为B2％，B2为45至80，基于所述非水电解液的总质量计。可选地，B2为50至80，55至80，60至80或60至75。
羧酸酯化合物具有低粘度、高介电常数的优点，将其应用于非水电解液中，有助于非水电解液具有合适的粘度和离子电导率，进而有利于锂离子的传输和改善二次电池的倍率性能。羧酸酯化合物可以改善二次电池的功率性能，但是其耐氧化能力较差，在高荷电状态存储时容易发生分解，因此其含量不宜太高。在一些实施例中，所述羧酸酯化合物的质量百分含量为B3％，B3为0至15，基于所述非水电解液的总质量计。在一些实施例中，B3可以为0。在一些实施例中，可选地，B3为2至15，2至10，2至8或2至5。
本申请的有机溶剂还可以包含上述环状碳酸酯化合物、链状碳酸酯化合物、羧酸酯化合物以外的其他溶剂。作为示例，所述其他溶剂可以包括砜类溶剂，例如环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)和二乙砜(ESE)等。
在一些实施例中，式1所示化合物的含量A1％和环状碳酸酯化合物的含量B1％满足B1/20+A1为1至3，可选地为1至2，1至1.8，1至1.6，1至1.4。式1所示化合物的含量A1％和环状碳酸酯化合物的含量B1％合理搭配后，有助于在改善集流体减薄后带来的功率性能变差、安全隐患增加等问题的前提下进一步改善二次电池的容量保持率。并且能够有效避免以下情况：式1所示化合物和环状碳酸酯化合物的含量均较高时，电池内阻和产气量较高，由此可能影响二次电池的功率性能和存储性能；式1所示化合物和环状碳酸酯化合物的含量均较低时，非水电解液的离子电导率较低，同时可能没有足够的式1所示化合物形成低阻抗的正极界面膜和负极界面膜，和在正极集流体表面形成钝化膜，由此二次电池的功率性能、安全性能和循环性能可能变差。
[添加剂]
在一些实施例中，所述非水电解液还可以包括添加剂，例如包括卤素取代的环状碳酸酯化合物、腈化合物、磷腈化合物、芳香烃及卤代芳香烃化合物、异氰酸酯化合物、酸酐化合物、硫酸酯化合物、亚硫酸酯化合物、磺酸酯化合物、二磺酸酯化合物中的至少一种。本申请对这些添加剂的种类没有特别的限制，只要不有损本申请的主旨即可。可选地，这些添加剂的总质量百分含量在5％以下，更可选地在2.5％以下，基于所述非水电解液的总质量计。
可选地，在一些实施例中，所述非水电解液还可以包括氟代碳酸乙烯酯(FEC)，其质量百分含量为C1％，0≤C1≤2.5，基于所述非水电解液的总质量计。例如，C1为0，0.10，0.20，0.50，0.75，1.0，1.25，1.50，1.75，2.0，2.25，2.50或以上任何数值所组成的范围。可选地，0＜C1≤2.5，0＜C1≤2.25，0＜C1≤2.0，0＜C1≤1.75，0＜C1≤1.5，0＜C1≤1.25，0＜C1≤1.0，0＜C1≤0.75或0＜C1≤0.5。
对二次电池而言，氟代碳酸乙烯酯能在较高的电位下发生还原分解反应，并在负极活性材料表面形成具有一定柔韧性的界面膜，同时还能抑制较低电位的有机溶剂的还原分解以及抑制有机溶剂嵌入负极活性材料。因此，当非水电解液含有氟代碳酸乙烯酯时，能有效提升二次电池的循环性能。此外，氟代碳酸乙烯酯耐高压氧化，有利于匹配高电压负极活性材料，从而有利于进一步提升二次电池的能量密度。
在一些实施例中，式1所示化合物的含量A1％和氟代碳酸乙烯酯的含量C1％还满足0.25≤C1/A1≤25。可选地，0.5≤C1/A1≤15，0.5≤C1/A1≤10，0.5≤C1/A1≤5，0.5≤C1/A1≤4，0.5≤C1/A1≤3，0.5≤C1/A1≤2.5，0.5≤C1/A1≤2，0.5≤C1/A1≤1.5或0.5≤C1/A1≤1.0。
当非水电解液含有氟代碳酸乙烯酯时，能有效提升二次电池的循环性能，但是，氟代碳酸乙烯酯容易分解并形成HF，HF会腐蚀正极活性材料，增加二次电池的产热量和产气量。而式1所示化合物可以作为一种正极活性材料的稳定剂，其结构中的B原子具有与正极活性材料表面的O原子相互作用的功能，由此能够稳定正极活性材料的晶体结构、减少HF对正极活性材料晶体结构的破坏。因此，将式1所示化合物与氟代碳酸乙烯酯联合使用，有利于充分发挥氟代碳酸乙烯酯对二次电池循环性能的进一步改善作用。此外，合理控制式1所示化合物的含量A1％和氟代碳酸乙烯酯的含量C1％之间的关系，使其满足0.25≤C1/A1≤25，能够充分发挥式1所示化合物和氟代碳酸乙烯酯的协同作用，从而有助于在改善集流体减薄后带来的功率性能变差、安全隐患增加等问题的前提下，进一步改善二次电池的循环性能。同时，氟代碳酸乙烯酯具有较高的介电常数，合理控制式1所示化合物的含量A1％和氟代碳酸乙烯酯的含量C1％之间的关系，使其满足0.25≤C1/A1≤25，还能够保证式1所示化合物的阴阳离子形成自由离子，减少阴阳离子缔合，一方面提高非水电解液的离子电导率，改善二次电池的循环性能，另一方面还能增加活性锂离子数量。
在一些实施例中，所述非水电解液还可以包括除水添加剂，除水添加剂有助于降低非水电解液的水含量并减少水分引起的一系列副反应，从而降低二次电池产气量和产热量，使二次电池具有更好的存储性能和安全性能。可选地，在一些实施例中，所述除水添加剂包括六甲基二硅氮烷(HMDS)、三(三甲基硅基)磷酸酯(TMSP)或其组合。这两种除水添加剂除能有效降低非水电解液的水分含量外，还能与六氟磷酸锂反应并形成二氟磷酸锂，一方面减少六氟磷酸锂分解和HF形成，另一方面还有助于进一步稳定正极界面膜和/或负极界面膜，降低正极界面阻抗和/或负极界面阻抗，从而有助于进一步提升二次电池的功率性能、存储性能和安全性能。
在一些实施例中，所述除水添加剂的质量百分含量在2％以下，可选地为0.05％至1％，更可选地为0.1％至1％，基于所述非水电解液的总质量计。
本申请的非水电解液可以按照本领域常规的方法制备。例如，可以将所述有机溶剂、所述锂盐和所述添加剂等混合均匀，得到非水电解液。各物料的添加顺序并没有特别的限制，例如，可以将所述锂盐和所述添加剂等加入到所述有机溶剂中混合均匀，得到非水电解液。
在本申请中，非水电解液中各组分及其含量可以按照本领域已知的方法测定。例如，可以通过气相色谱-质谱联用法(GC-MS)、离子色谱法(IC)、液相色谱法(LC)、核磁共振波谱法(NMR)等进行测定。
需要说明的是，本申请的非水电解液测试时，可以从二次电池中获取非水电解液。从二次电池中获取非水电解液的一个示例性方法包括如下步骤：将二次电池放电至放电截止电压(为了安全起见，一般使电池处于满放状态)后进行离心处理，之后取适量离心处理得到的液体即为非水电解液。也可以从二次电池的注液口直接获取非水电解液。
在本申请中，所述负极活性材料层包括负极活性材料，所述负极活性材料可采用本领域公知的用于二次电池的负极活性材料。作为示例，所述负极活性材料包括但不限于天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的至少一种。所述硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的至少一种。所述锡基材料可包括单质锡、锡氧化物、锡合金材料中的至少一种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。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，所述负极活性材料层还可选地包括负极导电剂。本申请对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的至少一种。在一些实施例中，基于所述负极活性材料层的总质量计，所述负极导电剂的质量百分含量在5％以下。
在一些实施例中，所述负极活性材料层还可选地包括负极粘结剂。本申请对所述负极粘结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、羧甲基壳聚糖(CMCS)中的至少一种。在一些实施例中，基于所述负极活性材料层的总质量计，所述负极粘结剂的质量百分含量在5％以下。
在一些实施例中，所述负极活性材料层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC-Na)、PTC热敏电阻材料等。在一些实施例中，基于所述负极活性材料层的总质量计，所述其他助剂的质量百分含量在2％以下。
所述负极活性材料层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
在本申请中，所述正极活性材料层包括正极活性材料，所述正极活性材料可采用本领域公知的用于二次电池的正极活性材料。例如，所述正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的至少一种。锂过渡金属氧化物的示例可包括锂钴氧化物、锂镍氧化物、锂锰氧化物、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、锂镍钴铝氧化物及其各自的改性化合物中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、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及其各自的改性化合物中的至少一种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池正极活性材料的传统公知的材料。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。
在一些实施例中，所述正极活性材料包括分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料，M表示过渡金属位掺杂阳离子，A表示氧位掺杂阴离子，0.8≤a≤1.2，0≤b≤1，0≤c≤1，0≤d≤1，0≤e≤1，0≤f≤0.2，0≤g≤2，0≤h≤2，b+c+d+e+f＝1，g+h＝ 2。
分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料可选地被M阳离子掺杂改性、A阴离子掺杂改性或被M阳离子和A阴离子同时掺杂改性，掺杂后得到的层状材料晶体结构更加稳定，晶格氧不易析出、过渡金属离子不易脱出，进而能够减少由其引起的一系列副反应，从而进一步提升二次电池的安全性能和电化学性能，例如循环性能、动力学性能等。
在一些实施例中，M选自Si、Ti、Mo、V、Ge、Se、Zr、Nb、Ru、Pd、Sb、Ce、Te及W中的至少一种。
在一些实施例中，A选自F、N、P及S中的至少一种。可选地，A选自F。经F掺杂改性后，Li aNi bCo cMn dAl eM fO gA h的晶体结构更加稳定，晶格氧不易析出、过渡金属离子不易脱出，由此能使二次电池具有更好的安全性能、循环性能和动力学性能。
a、b、c、d、e、f、g、h的值满足以下条件：使Li aNi bCo cMn dAl eM fO gA h保持电中性。
在一些实施例中，0＜b＜0.98。可选地，0.50≤b＜0.98，0.55≤b＜0.98，0.60≤b＜0.98，0.65≤b＜0.98，0.70≤b＜0.98，0.75≤b＜0.98或0.80≤b＜0.98。
在一些实施例中，c＝0。
在一些实施例中，0＜c≤0.20。可选地，0＜c≤0.15，0＜c≤0.10，0＜c≤0.09，0＜c≤0.08，0＜c≤0.07，0＜c≤0.06，0＜c≤0.05，0＜c≤0.04，0＜c≤0.03，0＜c≤0.02或0＜c≤0.01。钴在地壳中含量较少、开采困难且价格昂贵，因此，低钴或无钴成为正极活性材料必然的发展趋势。然而，钴对正极活性材料锂离子扩散速率贡献很大，低钴或无钴会降低正极活性材料的锂离子扩散速率，影响二次电池的循环性能。研究者们一直致力于提升低钴或无钴正极活性材料的锂离子扩散速率，但是目前尚没有很好的解决方案。
本申请的发明人在研究过程中还意外发现，式1所示化合物结构中的B原子容易与正极活性材料中的O原子结合，降低正极活性材料的电荷转移阻抗，从而降低锂离子在正极活性材料体相内的扩散阻力。因此，低钴或无钴正极活性材料能具有显著改善的锂离子扩散速率，低钴或无钴正极活性材料体相内的锂离子能及时地补充到表面，避免低钴或无钴正极活性材料表面过脱锂，从而稳定低钴或无钴正极活性材料的晶体结构。由于本申请的低钴或无钴正极活性材料的晶体结构更稳定，因此能够极大地降低由于低钴或无钴正极活性材料表面出现过脱锂而导致正极活性材料结构性质、化学性质或电化学性质变得不稳定等问题出现的概率，例如，正极活性材料不可逆畸变和晶格缺陷增加的问题。
在一些实施例中，d＝0并且0＜e＜0.50。可选地，d＝0并且0＜e≤0.45，d＝0并且0＜e≤0.40，d＝0并且0＜e≤0.35，d＝0并且0＜e≤0.30，d＝0并且0＜e≤0.25，d＝0并且0＜e≤0.20，d＝0并且0＜e≤0.15或d＝0并且0＜e≤0.10。
在一些实施例中，e＝0并且0＜d＜0.50。可选地，e＝0并且0＜d≤0.45，e＝0并且0＜d≤0.40，e＝0并且0＜d≤0.35，e＝0并且0＜d≤0.30，e＝0并且0＜d≤0.25，e＝0并且0＜d≤0.20，e＝0并且0＜d≤0.15或e＝0并且0＜d≤0.10。
在一些实施例中，0＜d＜0.50并且0＜e＜0.50。可选地，0＜d≤0.30并且0＜e≤ 0.10。
在一些实施例中，g＝2，h＝0。
在一些实施例中，g＝0，h＝2。
在一些实施例中，0＜g＜2，0＜h＜2，且g+h＝2。
作为示例，分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料包括但不限于LiNi 0.7Mn 0.3O 2、LiNi 0.69Co 0.01Mn 0.3O 2、LiNi 0.68Co 0.02Mn 0.3O 2、LiNi 0.65Co 0.05Mn 0.3O 2、LiNi 0.63Co 0.07Mn 0.3O 2、LiNi 0.61Co 0.09Mn 0.3O 2中的至少一种。
Li aNi bCo cMn dAl eM fO gA h可以按照本领域常规方法制备。示例性制备方法如下：将锂源、镍源、钴源、锰源、铝源、M元素前驱体、A元素前驱体混合后烧结得到。烧结气氛可为含氧气氛，例如，空气气氛或氧气气氛。烧结气氛的O 2浓度例如为70％至100％。烧结温度和烧结时间可根据实际情况进行调节。
作为示例，锂源包括但不限于氧化锂(Li 2O)、磷酸锂(Li 3PO 4)、磷酸二氢锂(LiH 2PO 4)、醋酸锂(CH 3COOLi)、氢氧化锂(LiOH)、碳酸锂(Li 2CO 3)及硝酸锂(LiNO 3)中的至少一种。作为示例，镍源包括但不限于硫酸镍、硝酸镍、氯化镍、草酸镍及醋酸镍中的至少一种。作为示例，钴源包括但不限于硫酸钴、硝酸钴、氯化钴、草酸钴及醋酸钴中的至少一种。作为示例，锰源包括但不限于硫酸锰、硝酸锰、氯化锰、草酸锰及醋酸锰中的至少一种。作为示例，铝源包括但不限于硫酸铝、硝酸铝、氯化铝、草酸铝及醋酸铝中的至少一种。作为示例，M元素前驱体包括但不限于M元素的氧化物、硝酸化合物、碳酸化合物、氢氧化合物及醋酸化合物中的至少一种。作为示例，A元素的前驱体包括但不限于氟化铵、氟化锂、氟化氢、氯化铵、氯化锂、氯化氢、硝酸铵、亚硝酸铵、碳酸铵、碳酸氢铵、磷酸铵、磷酸、硫酸铵、硫酸氢铵、亚硫酸氢铵、亚硫酸铵、硫化氢铵、硫化氢、硫化锂、硫化铵及单质硫中的至少一种。
在一些实施例中，基于正极活性材料层的总质量计，分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料的含量为80％至99％。例如，分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料的含量可以为80％，81％，82％，83％，84％，85％，86％，87％，88％，89％，90％，91％，92％，93％，94％，95％，96％，97％，98％，99％或以上任何数值所组成的范围。可选地，分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料的含量为85％至99％，90％至99％，95％至99％，80％至98％，85％至98％，90％至98％，95％至98％，80％至97％，85％至97％，90％至97％或95％至97％。
在一些实施例中，所述正极活性材料层还可选地包括正极导电剂。本申请对所述正极导电剂的种类没有特别的限制，作为示例，所述正极导电剂包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的至少一种。在一些实施例中，基于所述正极活性材料层的总质量计，所述正极导电剂的质量百分含量在5％以下。
在一些实施例中，所述正极活性材料层还可选地包括正极粘结剂。本申请对所述正极粘结剂的种类没有特别的限制，作为示例，所述正极粘结剂可包括聚偏氟乙烯(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、含氟丙烯酸酯类树脂中的至少一种。在一些实施例中，基于所述正极活性材料层的总质量计，所述正极粘结剂的质量百 分含量在5％以下。
所述正极活性材料层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
在本申请中，所述隔离膜设置在所述正极极片和所述负极极片之间，主要起到防止正极和负极短路的作用，同时可以使锂离子通过。本申请对所述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，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。当所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施例中，所述二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。所述二次电池的外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的至少一种。
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。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图2所示，外包装可包括壳体51和盖板53。壳体51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51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。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52。电极组件52封装于所述容纳腔。非水电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和非水电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入非水电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在本申请的一些实施例中，根据本申请的二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，在电池模块4中，多个二次电池5可以是沿电池模块4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5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可 以按照任意的方式排布于电池箱中。
本申请实施方式还提供一种用电装置，所述用电装置包括本申请的二次电池、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。所述用电装置可以但不限于是移动设备(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。
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的示意图。该用电装置为纯电动车、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对高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1至30和对比例1至4的二次电池均按照下述方法进行制备。
正极极片的制备
将正极活性材料LiNi 0.65Co 0.05Mn 0.3O 2、导电剂炭黑(Super P)、粘结剂聚偏氟乙烯(PVDF)按质量比97.5:1.4:1.1在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。正极集流体的厚度H2μm、断裂延伸率Q％以及正极活性材料层的压实密度P2g/cm 3的具体范围分别如表1所示。
负极极片的制备
将负极活性材料石墨、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)、导电剂炭黑(Super P)按质量比96.2:1.8:1.2:0.8在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。负极集流体的厚度H1μm以及负极活性材料层的压实密度P1g/cm 3的具体范围分别如表1所示。
隔离膜
采用多孔聚乙烯(PE)膜作为隔离膜。
非水电解液的制备
按照表1所示组成将环状碳酸酯化合物、链状碳酸酯化合物和羧酸酯化合物混合均匀得到有机溶剂，之后按照表1所示组成将式1所示化合物、氟代碳酸乙烯酯(FEC)、六氟磷酸锂(LiPF 6)和双氟磺酰亚胺锂(LiFSI)加入有机溶剂中混合均匀，得到非水电解液。在表1中，各组分的含量均基于非水电解液的总质量计，“/”表示未 加入对应的组分。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件置于外包装中，干燥后注入非水电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
测试部分
(1)二次电池质量能量密度测试
在25℃下，将二次电池以0.33C恒流充电至4.25V，继续恒压充电至电流为0.05C；将二次电池静置5min后，以0.33C恒流放电至2.8V，得到放电能量。二次电池的质量能量密度(Wh/Kg)＝放电能量/二次电池的质量。
(2)二次电池功率性能测试
在25℃下，将二次电池以0.1C恒流充电至4.25V，继续恒压充电至电流为0.05C，此时二次电池为满充状态；将二次电池以1C恒流放电约30分钟并调整二次电池的荷电状态为50％SOC，此时二次电池的电压记为V 0；将二次电池以4C的电流I 1放电30秒，采用0.1秒采点，放电末期电压记为V 1。二次电池的内阻DCR＝(V 0-V 1)/I 1。二次电池的内阻越小，功率性能越好。
(3)二次电池热箱安全性能测试
在25℃下，将二次电池以0.1C恒流充电至4.25V，继续恒压充电至电流为0.05C，此时二次电池为满充状态；将满充状态的二次电池置于密封良好的高温箱中，以5℃/min升温至100℃，保持1小时后以5℃/min升温至105℃，保持30分钟；之后以5℃/min升温速率每升高5℃后保持30min，直至二次电池失效，记录二次电池失效前的最高温度T max。T max越高，二次电池的热箱安全性能越好。
(4)二次电池循环性能测试
在45℃下，将二次电池以1C恒流充电至4.25V，继续恒压充电至电流为0.05C，此时二次电池为满充状态，记录此时的充电容量，即为第1圈充电容量；将二次电池静置5min后，以1C恒流放电至2.8V，此为一个循环充放电过程，记录此时的放电容量，即为第1圈放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量。二次电池45℃循环600圈容量保持率(％)＝600圈循环后的放电容量/第1圈放电容量×100％。
(5)二次电池存储性能测试
在60℃下，将二次电池以1C恒流充电到4.25V，继续恒压充电至电流为0.05C，此时用排水法测试二次电池的体积并记为V 0；将二次电池放入60℃的恒温箱，存储30天后取出，此时用排水法测试二次电池的体积并记为V 1。二次电池60℃存储30天后的体积膨胀率(％)＝[(V 1-V 0)/V 0]×100％。
表1示出实施例1至30和对比例1至4的正极极片、负极极片和非水电解液制备参数。表2示出实施例1至30和对比例1至4按照上述性能测试方法得到的测试结果。
Figure PCTCN2022094511-appb-000006
Figure PCTCN2022094511-appb-000007
Figure PCTCN2022094511-appb-000008
Figure PCTCN2022094511-appb-000009
综合表1和表2测试结果可知，在采用减薄负极集流体的二次电池中，当非水电解液含有式1所示化合物并且其含量A1％与负极集流体的厚度H1μm和负极活性材料层的压实密度P1g/cm 3满足A1/H1为0.003至0.40和P1/A1为1至90时，二次电池能同时兼顾较高的能量密度、较低的内阻、较高的热箱安全性能、较高的容量保持率以及较低的体积膨胀率。
综合实施例1至9和对比例2的测试结果可知，A1/H1小于0.003和/或P1/A1大于90时，没有足够的式1所示化合物形成低阻抗的负极界面膜，由此负极界面阻抗较高，不能有效降低负极集流体减薄对电池内阻和产热量的恶化，因此，二次电池的功率性能和安全性能较差，同时二次电池容量保持率增加也有限。
综合实施例1至9和对比例3至4的测试结果可知，A1/H1小于大于0.40和/或P1/A1小于1时，过多的式1所示化合物会导致负极界面阻抗不降反增，由此二次电池的内阻较高、容量保持率较差；尽管式1所示化合物可贡献部分活性锂离子，略增加二次电池的能量密度，但是阴离子的分解导致电池内部产气量较高、热箱安全性能明显变差。
综合表1和表2的测试结果还可知，当二次电池还采用减薄的正极集流体时，通过使式1所示化合物的含量A1％与正极集流体的厚度H2μm、正极集流体的断裂延伸率Q％和正极活性材料层的压实密度P2g/cm 3满足A1/H2为0.0015至0.20，Q+A1为1至4和P2/A1为2至340时，二次电池能在具有较低的内阻、较高的热箱安全性能、较高的容量保持率以及较低的体积膨胀率的前提下具有进一步提升的能量密度。可能的原因在于，式1所示化合物还能优先于有机溶剂在正极活性材料表面被氧化，并且其氧化产物还具体低阻抗的特性，由此有助于形成低阻抗的正极界面膜；同时，式1所示化合物分子结构中的B原子还易与正极界面膜中的LiF等无机组分牢固地结合，由此可加快锂离子传输并明显降低电池内阻和产热量。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (19)

  1. 一种二次电池，包括正极极片、负极极片以及非水电解液，所述正极极片包括正极集流体以及位于所述正极集流体至少一个表面上的正极活性材料层，所述负极极片包括负极集流体以及位于所述负极集流体至少一个表面上的负极活性材料层，
    其中，
    所述非水电解液包括式1所示化合物，X、Y各自独立地表示氟原子，或者部分氟化或全部氟化的如下基团组成的组中的至少一种：C1-C10的烷基、C2-C10的烯基、C2-C10的炔基、C6-C8的芳基、C1-C10的烷氧基、C2-C10的烯氧基、C2-C10的炔氧基、C6-C8的芳氧基，并且X、Y中的至少一者表示氟原子；
    Figure PCTCN2022094511-appb-100001
    基于所述非水电解液的总质量计，所述式1所示化合物的质量百分含量为A1％，所述负极集流体的厚度为H1μm，所述负极活性材料层的压实密度为P1g/cm 3，并且所述二次电池满足：H1为3至7，A1/H1为0.003至0.40和P1/A1为1至90。
  2. 根据权利要求1所述的二次电池，其中，
    A1/H1为0.003至0.1，可选地为0.003至0.08；和/或，
    P1/A1为3至90，可选地为5至90。
  3. 根据权利要求1或2所述的二次电池，其中，所述正极集流体的厚度为H2μm、所述正极集流体的断裂延伸率为Q％，所述正极活性材料层的压实密度为P2g/cm 3，并且所述二次电池满足：H2为4至14，A1/H2为0.0015至0.20，Q+A1为1至4和P2/A1为2至340。
  4. 根据权利要求3所述的二次电池，其中，
    A1/H2为0.002至0.05，可选地为0.01至0.05；和/或，
    Q+A1为1.5至3.5，可选地为2.0至3.5；和/或，
    P2/A1为5至340，可选地为10至340。
  5. 根据权利要求1-4中任一项所述的二次电池，其中，
    A1为0.02至1.6，可选地为0.02至0.5；和/或，
    P1为1.4至1.8，可选地为1.55至1.75；和/或，
    P2为3.2至3.7，可选地为3.4至3.7；和/或，
    Q为0.5至3.5，可选地为1.5至3.5。
  6. 根据权利要求1-5中任一项所述的二次电池，其中，所述非水电解液还包括第一锂盐，所述第一锂盐包括六氟磷酸锂，所述六氟磷酸锂的质量百分含量为A2％，基于所述非水电解液的总质量计，
    可选地，A2/A1为5至650，更可选地为15至300；和/或，
    可选地，A2为6至14。
  7. 根据权利要求1-5中任一项所述的二次电池，其中，所述非水电解液还包括第一锂盐，所述第一锂盐包括六氟磷酸锂和双氟磺酰亚胺锂的组合，所述六氟磷酸锂的质量百分含量为A2％，所述双氟磺酰亚胺锂的质量百分含量为A3％，均基于所述非水电解液的总质量计，
    可选地，A2为6至14，A3大于0且小于等于5；和/或，
    可选地，A3/A2在0.8以下，更可选地为0.05至0.3；和/或，
    可选地，A2/A1为5至650，更可选地为15至300。
  8. 根据权利要求1-7中任一项所述的二次电池，其中，所述非水电解液还包括第二锂盐，所述第二锂盐包括四氟硼酸锂、高氯酸锂、六氟砷酸锂、二氟磷酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种，所述第二锂盐在所述非水电解液中的总质量百分含量为A4％，基于所述非水电解液的总质量计，
    可选地，A4在5以下，更可选地在2以下。
  9. 根据权利要求8所述的二次电池，其中，所述第二锂盐包括二氟磷酸锂，
    可选地，所述二氟磷酸锂与所述六氟磷酸锂的质量比α为0.01至0.15，更可选地为0.01至0.1。
  10. 根据权利要求1-9中任一项所述的二次电池，其中，所述非水电解液还包括环状碳酸酯化合物，所述环状碳酸酯化合物的质量百分含量为B1％，基于所述非水电解液的总质量计，
    可选地，B1为0.5至20，更可选地为15至18；和/或，
    可选地，B1/20+A1为1至3，更可选地为1至2。
  11. 根据权利要求10所述的二次电池，其中，所述环状碳酸酯化合物包括碳酸乙烯酯、碳酸丙烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯中的至少一种。
  12. 根据权利要求1-11中任一项所述的二次电池，其中，所述非水电解液还包括氟代碳酸乙烯酯，其质量百分含量为C1％，基于所述非水电解液的总质量计，
    可选地，0＜C1≤2.5，更可选地，0＜C1≤2.0；和/或，
    可选地，0.25≤C1/A1≤25，更可选地，0.5≤C1/A1≤10。
  13. 根据权利要求1-12中任一项所述的二次电池，其中，所述非水电解液还包括除水添加剂，所述除水添加剂包括六甲基二硅氮烷、三(三甲基硅基)磷酸酯中的至少一种，
    可选地，所述除水添加剂的质量百分含量在2％以下，更可选地为0.05％至1％，基于所述非水电解液的总质量计。
  14. 根据权利要求1所述的二次电池，其中，X、Y满足如下条件(1)至(3)中的一者：
    (1)X、Y均表示氟原子；
    (2)X、Y中的一者表示氟原子，另一者表示部分氟化或全部氟化的如下基团组成的组中的至少一种：C1-C5的烷基、C2-C5的烯基、C2-C5的炔基、苯基、苯氧基、C1-C5的烷氧基、C2-C5的烯氧基和C2-C5的炔氧基；
    (3)X、Y中的一者表示氟原子，另一者表示部分氟化或全部氟化的如下基团组成的组中的至少一种：甲基、乙基、正丙基、异丙基、正丁基、叔丁基、乙烯基、丙烯基、 烯丙基、丁二烯基、乙炔基、丙炔基、苯基、甲氧基、乙氧基、丙氧基、乙烯氧基、丙烯氧基、乙炔氧基、丙炔氧基和苯氧基。
  15. 根据权利要求1所述的二次电池，其中，所述式1所示化合物包括如下化合物中的至少一种，
    Figure PCTCN2022094511-appb-100002
  16. 根据权利要求1-15中任一项所述的二次电池，其中，
    所述负极集流体采用铜箔或铜合金箔；和/或，
    所述正极集流体采用铝箔或铝合金箔。
  17. 一种电池模块，包括根据权利要求1-16中任一项所述的二次电池。
  18. 一种电池包，包括根据权利要求1-16中任一项所述的二次电池、根据权利要求17所述的电池模块中的一种。
  19. 一种用电装置，包括根据权利要求1-16中任一项所述的二次电池、根据权利要求17所述的电池模块、根据权利要求18所述的电池包中的至少一种。
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012079593A (ja) * 2010-10-04 2012-04-19 Sony Corp 非水電解質二次電池および非水電解質
CN203733894U (zh) * 2014-01-17 2014-07-23 宁德新能源科技有限公司 锂离子电池
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
CN111193071A (zh) * 2020-01-09 2020-05-22 重庆市紫建电子股份有限公司 一种高电压快充锂离子电池的电解液及锂离子电池
CN112349962A (zh) * 2019-08-08 2021-02-09 宁德时代新能源科技股份有限公司 锂离子电池
CN114605289A (zh) * 2022-03-02 2022-06-10 湖州师范学院 一种非水电解液用氨基甲酸酯化合物及其应用

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012079593A (ja) * 2010-10-04 2012-04-19 Sony Corp 非水電解質二次電池および非水電解質
CN203733894U (zh) * 2014-01-17 2014-07-23 宁德新能源科技有限公司 锂离子电池
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
CN112349962A (zh) * 2019-08-08 2021-02-09 宁德时代新能源科技股份有限公司 锂离子电池
CN111193071A (zh) * 2020-01-09 2020-05-22 重庆市紫建电子股份有限公司 一种高电压快充锂离子电池的电解液及锂离子电池
CN114605289A (zh) * 2022-03-02 2022-06-10 湖州师范学院 一种非水电解液用氨基甲酸酯化合物及其应用

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