WO2023221121A1 - 非水电解液以及包含其的二次电池、电池模块、电池包及用电装置 - Google Patents

非水电解液以及包含其的二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023221121A1
WO2023221121A1 PCT/CN2022/094228 CN2022094228W WO2023221121A1 WO 2023221121 A1 WO2023221121 A1 WO 2023221121A1 CN 2022094228 W CN2022094228 W CN 2022094228W WO 2023221121 A1 WO2023221121 A1 WO 2023221121A1
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aqueous electrolyte
optionally
lithium salt
secondary battery
lithium
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PCT/CN2022/094228
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English (en)
French (fr)
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吴则利
韩昌隆
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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 KR1020237026605A priority Critical patent/KR20230162773A/ko
Priority to CN202280012714.7A priority patent/CN117178402A/zh
Priority to PCT/CN2022/094228 priority patent/WO2023221121A1/zh
Priority to EP22924570.9A priority patent/EP4307431A1/en
Priority to US18/228,223 priority patent/US20230378538A1/en
Publication of WO2023221121A1 publication Critical patent/WO2023221121A1/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
    • H01M10/052—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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M2004/028—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
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three 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

  • This application belongs to the field of battery technology, and specifically relates to a non-aqueous electrolyte and secondary batteries, battery modules, battery packs and electrical devices 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
  • electric tools electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.
  • secondary batteries need to simultaneously meet the requirements of high energy density, long cycle life, high safety performance, and good rate performance.
  • the non-aqueous electrolyte plays a role in conducting ions between the positive electrode and the negative electrode, and is one of the key factors affecting the performance of secondary batteries. Therefore, there is an urgent need to provide a non-aqueous electrolyte with good comprehensive performance.
  • the purpose of this application is to provide a non-aqueous electrolyte and a secondary battery, battery module, battery pack and electrical device containing the same, which can enable the secondary battery to achieve good cycle performance, storage performance and dynamic performance at the same time.
  • a first aspect of the application provides a non-aqueous electrolyte solution, including an electrolyte salt and a non-aqueous solvent, wherein the electrolyte salt includes: a first lithium salt having a structure shown in Formula 1, R 1 represents a fluorine atom or partial fluorination Or a fully fluorinated C1-C10 alkyl group, whose mass content in the non-aqueous electrolyte is A1, based on the total mass of the non-aqueous electrolyte; a second lithium salt having the structure shown in Formula 2 , R 2 and R 3 each independently represent a fluorine atom or at least one of the group consisting of the following groups that are partially or fully fluorinated: C1-C10 alkyl, C2-C10 alkenyl, C2- C10 alkynyl group, C6-C8 aryl group, C1-C10 alkoxy group, C2-C10 alkenyloxy group, C2-C10 alkynyloxy group,
  • the non-aqueous electrolyte solution satisfies: A1+A2+A3 is below 1%, A1/A2 is 0.016 to 40, and A1/(A2+A3) is 0.006 to 13.5.
  • the content A1, the content A2 of the second lithium salt, and the content A3 of the third lithium salt are such that A1/A2 is 0.016 to 40, and A1/(A2+A3) is 0.006 to 13.5, the obtained non-aqueous electrolyte can At the same time, it has high thermal stability, high ionic conductivity and a wide electrochemical window, and the non-aqueous electrolyte can also passivate the aluminum foil current collector and form dense layers on the surface of both the positive and negative active materials. , stable, low impedance and high ionic conductivity interface film, thus the secondary battery using the non-aqueous electrolyte of the present application can take into account good cycle performance, storage performance and dynamic performance at the same time.
  • A1/A2 is from 0.03 to 10, optionally from 0.1 to 5. This is conducive to giving full play to the synergistic effect between the first lithium salt and the second lithium salt, thereby forming a denser, more stable and more ionic conductive interface film on the surface of the negative electrode active material.
  • A1/(A2+A3) is 0.02 to 3.5, optionally 0.1 to 2. This is conducive to giving full play to the synergistic effect between the first lithium salt, the second lithium salt and the third lithium salt, thereby forming a denser, more stable and more ionic conductive interface film on the surface of the positive electrode active material. .
  • the non-aqueous electrolyte solution also satisfies A3/A2 of 0.04 to 30, optionally 1 to 10. This is conducive to giving full play to the synergistic effect between the second lithium salt and the third lithium salt, thereby further improving the cycle performance, storage performance and dynamic performance of the secondary battery.
  • A1 is 0.005% to 0.2%, optionally 0.01% to 0.1%.
  • A2 is 0.005% to 0.3%, optionally 0.01% to 0.3%.
  • A3 is 0.01% to 0.5%, optionally 0.02% to 0.2%.
  • the first lithium salt includes at least one of the following compounds:
  • the second lithium salt includes at least one of the following compounds:
  • the electrolyte salt further includes at least one of a fourth lithium salt and a fifth lithium salt.
  • the fourth lithium salt is lithium hexafluorophosphate, and its mass in the non-aqueous electrolyte is The content is A4, based on the total mass of the non-aqueous electrolyte.
  • the fifth lithium salt is lithium bisfluorosulfonyl imide, and its mass content in the non-aqueous electrolyte is A5, based on the non-aqueous electrolyte. Based on the total mass of the aqueous electrolyte, the non-aqueous electrolyte satisfies: A4+A5 is 10% to 20%, optionally 10% to 18%.
  • A4/A5 is 0.2 to 3, optionally 0.5 to 1.5. Therefore, the non-aqueous electrolyte is not easily hydrolyzed, and can also achieve higher thermal stability while helping to form an interface film with lower impedance.
  • (A4+A5)/(A1+A2+A3) is 10 to 200, optionally 20 to 120, more optionally 40 to 100.
  • a dense, stable, low-resistance and highly ionic conductive interface film is formed on the surface of the material and the negative active material.
  • the non-aqueous solvent includes: a first solvent, including at least one of ethylene carbonate, propylene carbonate, and butylene carbonate, the mass content of which in the non-aqueous solvent is B1, based on the total mass of the non-aqueous solvent;
  • the second solvent includes at least one of methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, and ethylpropyl carbonate.
  • the non-aqueous electrolyte solution satisfies: B1 is 10% to 30%, B2 is 50% to 90%, and B3 is 0% to 20%.
  • B1/(B2+B3) is 0.1 to 0.45, optionally 0.2 to 0.3. This helps to make the interface film formed on the surface of the negative active material denser and smoother, thereby effectively inhibiting the growth of dendrites.
  • the non-aqueous electrolyte further includes: a first additive, including at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, and 1,3-propanesultone.
  • a first additive including at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, and 1,3-propanesultone.
  • One, its mass content in the non-aqueous electrolyte solution is C1
  • C1 is 0.05% to 2%, optionally 0.1% to 1%.
  • the first additive helps to further improve the interface properties of the positive electrode and/or the negative electrode, thereby further improving at least one of cycle performance, storage performance and kinetic performance of the secondary battery.
  • the non-aqueous electrolyte solution also satisfies (C1+A5)/B1 of 0.3 to 0.8, optionally 0.3 to 0.6. This helps to give full play to the synergy between the above components, and effectively reduces the defects of each component when used alone, so that the secondary battery has excellent cycle performance, and can also avoid deterioration of kinetic performance and power performance. .
  • the non-aqueous electrolyte solution further includes: a second additive, including at least one of sulfamic acid and its salts, whose mass content in the non-aqueous electrolyte solution is C2, Based on the total mass of the non-aqueous electrolyte, C2 is 0.005% to 0.1%, optionally 0.005% to 0.05%. This helps to improve the cycle performance and kinetic performance of the secondary battery.
  • a second additive including at least one of sulfamic acid and its salts, whose mass content in the non-aqueous electrolyte solution is C2, Based on the total mass of the non-aqueous electrolyte, C2 is 0.005% to 0.1%, optionally 0.005% to 0.05%. This helps to improve the cycle performance and kinetic performance of the secondary battery.
  • a second aspect of the present application provides a secondary battery, including an electrode assembly, a non-aqueous electrolyte and an outer packaging, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of the first aspect of the present application, so the second aspect of the present application Secondary batteries can simultaneously take into account good cycle performance, storage performance and kinetic performance.
  • the electrode assembly includes a positive electrode piece and a negative electrode piece, the charge transfer resistance of the positive electrode piece is Rct1, the charge transfer resistance of the negative electrode piece is Rct2, and Rct1/Rct2 is 0.5 to 2, optionally 1.25 to 2.
  • Rct1 the charge transfer resistance of the positive electrode piece
  • Rct2 the charge transfer resistance of the negative electrode piece
  • Rct1/Rct2 is 0.5 to 2, optionally 1.25 to 2.
  • the charge transfer resistance of the positive electrode piece is obtained by the following test method: assemble the positive electrode piece into a symmetrical battery, use the electrochemical AC impedance method of the electrochemical workstation to test its electrochemical impedance spectrum, draw the Nyquist diagram, and use the equivalent The circuit curve fitting method was used to analyze the obtained Nyquist diagram, and the diameter of the semicircle was used as the charge transfer resistance of the positive electrode piece as Rct1.
  • the charge transfer resistance of the negative electrode plate is obtained by the following test method: assemble the negative electrode plate into a symmetrical battery, use the electrochemical AC impedance method of the electrochemical workstation to test its electrochemical impedance spectrum, draw a Nyquist diagram, and use an equivalent circuit The obtained Nyquist diagram was analyzed by the curve fitting method, and the charge transfer resistance of the negative electrode piece was taken as the diameter of the semicircle as Rct2.
  • the non-aqueous electrolyte includes a first electrolyte that infiltrates the electrode assembly and a second electrolyte located between the electrode assembly and the outer package.
  • the first electrolyte The sum of the mass contents of the first lithium salt, the second lithium salt, the third lithium salt, the first additive and the second additive in the liquid is X1.
  • the second electrolyte Based on the total mass of the first electrolyte, the second electrolyte The sum of the mass contents of the first lithium salt, the second lithium salt, the third lithium salt, the first additive and the second additive is X2, based on the total mass of the second electrolyte, and 0.5 ⁇ X1/X2 ⁇ 1.
  • the first electrolyte is obtained by the following test method: after the secondary battery is discharged to the discharge cut-off voltage, the electrode assembly is disassembled and centrifuged, and then the liquid obtained by the centrifugation is the third electrolyte. An electrolyte.
  • 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, optionally, A is selected from F.
  • c 0.
  • 0 ⁇ c ⁇ 0.20 optionally, 0 ⁇ c ⁇ 0.10.
  • 0 ⁇ d ⁇ 0.50 and 0 ⁇ e ⁇ 0.50 optionally, 0 ⁇ d ⁇ 0.30 and 0 ⁇ e ⁇ 0.10.
  • a third aspect of the present application provides a battery module, including the secondary battery of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack, including one of the secondary battery of the second aspect of the present application and the battery module of the third aspect of the present application.
  • a fifth aspect of the present application provides an electrical device, including at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect, and the battery pack of the fourth aspect of the present application.
  • the secondary battery of the present application can take into account good cycle performance, storage performance and dynamic performance at the same time.
  • the battery module, battery pack and electrical device of the present application include the secondary battery provided by the present application, and therefore have at least the same characteristics as the secondary battery. Batteries have the same advantages.
  • 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 combined in any combination, i.e., 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).
  • alkyl refers to a saturated hydrocarbon group, including both straight-chain and branched-chain structures.
  • alkyl groups include, but are not limited to, methyl, ethyl, propyl (such as n-propyl, isopropyl), butyl (such as n-butyl, isobutyl, sec-butyl, tert-butyl), pentyl (Such as n-pentyl, isopentyl, neopentyl).
  • a C1-C10 alkyl group ie, an alkyl group, may contain 1 to 10 carbon atoms.
  • alkenyl refers to an unsaturated hydrocarbon group containing carbon-carbon double bonds, including both linear and branched structures. The number of carbon-carbon double bonds may be one or multiple. Examples of alkenyl groups include, but are not limited to, vinyl, propenyl, allyl, butadienyl. In various embodiments, a C2-C10 alkenyl group, i.e., alkenyl group, may contain 2 to 10 carbon atoms.
  • alkynyl refers to an unsaturated hydrocarbon group containing a carbon-carbon triple bond, including both a straight-chain structure and a branched-chain structure.
  • the number of carbon-carbon triple bonds may be one or multiple.
  • alkynyl groups include, but are not limited to, ethynyl, propynyl, butynyl, butadiynyl.
  • a C2-C10 alkynyl group i.e., an alkynyl group, may contain 2 to 10 carbon atoms.
  • aryl refers to a carbocyclic ring system with aromatic properties, and its structure can be monocyclic, polycyclic or condensed. Examples of aryl groups include, but are not limited to, phenyl. In various embodiments, a C6-C8 aryl group, i.e., an aryl group, may contain 6 to 8 carbon atoms.
  • alkoxy refers to an alkyl group containing an oxygen atom (-O-)
  • alkenyloxy refers to an alkenyl group containing an oxygen atom (-O-)
  • alkynyloxy refers to an alkyl group containing an oxygen atom (-O-)
  • aryloxy refers to an alkyl group containing an oxygen atom (-O-).
  • 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.
  • Non-aqueous electrolyte is one of the key factors affecting the performance of secondary batteries.
  • the most widely used non-aqueous electrolyte system currently commercially is a mixed carbonate solution of lithium hexafluorophosphate.
  • lithium hexafluorophosphate has poor thermal stability in high temperature environments. It decomposes at higher temperatures to form LiF and PF 5 .
  • LiF will increase the interface resistance; PF 5 has strong Lewis acidity, which will interact with the lone pair of electrons on the oxygen atoms in the solvent molecules to cause the solvent to decompose; in addition, PF 5 has a high resistance to trace amounts of moisture in the non-aqueous electrolyte. Sensitivity, HF will be generated when contacting water, thereby increasing the acidity of the non-aqueous electrolyte, which will easily corrode the positive active material and positive current collector, causing the transition metal ions in the positive active material to dissolve. In addition, after the transition metal ions in the positive electrode active material are eluted and migrate to the negative electrode, they will be reduced to transition metals.
  • the transition metal thus produced is equivalent to a "catalyst” and will catalyze the solid electrolyte interphase film (solid electrolyte interphase) on the surface of the negative electrode active material.
  • SEI decomposes, producing by-products. Part of the by-product is gas, which causes the secondary battery to expand and affects the safety performance of the secondary battery; another part of the by-product is deposited on the surface of the negative active material, which blocks the lithium ion transmission channel and causes secondary battery failure.
  • the battery impedance increases, thereby affecting the dynamic performance of the secondary battery; in addition, in order to replenish the lost interface film, the non-aqueous electrolyte and the active lithium ions inside the battery are continuously consumed, which will bring irreversible losses to the secondary battery capacity retention rate. Influence.
  • the inventor of the present application surprisingly discovered that when the non-aqueous electrolyte contains an appropriate content of auxiliary lithium salt, the secondary battery can achieve good cycle performance, storage performance and dynamic performance at the same time.
  • the first aspect of the embodiment of the present application provides a non-aqueous electrolyte solution including an electrolyte salt and a non-aqueous solvent.
  • the electrolyte salt includes: a first lithium salt having a structure shown in Formula 1, R1 represents a fluorine atom or a partially fluorinated or fully fluorinated C1-C10 alkyl group, and its mass in the non-aqueous electrolyte solution The content is A1, based on the total mass of the non-aqueous electrolyte; the second lithium salt has the structure shown in Formula 2, R 2 and R 3 each independently represent a fluorine atom or the following partially fluorinated or fully fluorinated At least one of the group consisting of: C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl, C1-C10 alkoxy, C2-C10 Alkenyloxy group, C2-C10 alkynyloxy group, C6-C8 aryloxy group, the mass content of which in the non-aqueous electrolyte solution is A2, based on the total mass of the non-a
  • the non-aqueous electrolyte solution satisfies: A1+A2+A3 is below 1%, A1/A2 is 0.016 to 40, and A1/(A2+A3) is 0.006 to 13.5.
  • the content A1, the content A2 of the second lithium salt, and the content A3 of the third lithium salt are such that A1/A2 is 0.016 to 40, and A1/(A2+A3) is 0.006 to 13.5, the obtained non-aqueous electrolyte can At the same time, it has high thermal stability, high ionic conductivity and a wide electrochemical window, and the non-aqueous electrolyte can also passivate the aluminum foil current collector and form dense layers on the surface of both the positive and negative active materials. , stable, low impedance and high ionic conductivity interface film, thus the secondary battery using the non-aqueous electrolyte of the present application can take into account good cycle performance, storage performance and dynamic performance at the same time.
  • the first lithium salt contains sulfonate anions, which can be reduced to form highly conductive ionic compounds such as Li 2 SO 4 , which is beneficial to improving the ion transport characteristics of the negative electrode interface film; the molecular structure of the second lithium salt contains an oxalate group, which reduces
  • the product can further react with organic components such as (LiOCO 2 CH 2 ) 2 in the interface film to form complex and stable oligomers, which can fully coat the surface of the negative active material and prevent direct contact between the non-aqueous electrolyte and the negative active material. And reduce the embedding of non-aqueous solvent into the negative active material.
  • the negative electrode interface film cannot fully cover the surface of the negative electrode active material, thereby increasing the irreversible consumption of lithium ions and reducing the capacity retention rate of the secondary battery; when A1/A2 is less than 0.016, the negative electrode interface film The ion transport characteristics of the membrane are poor, causing the internal resistance of the secondary battery to increase and the kinetic performance to deteriorate.
  • the B atoms in the second lithium salt molecular structure are easily combined with the O atoms in the cathode active material, which can also reduce the charge transfer resistance of the cathode active material and reduce the diffusion resistance of lithium ions in the bulk phase of the cathode active material.
  • A1/(A2+A3) is greater than 13.5, the second lithium salt and the third lithium salt cannot effectively compensate for the deterioration of the internal resistance of the battery caused by the excessive first lithium salt, so the dynamic performance of the secondary battery is poor.
  • the positive electrode interface film cannot fully cover the surface of the positive electrode active material, thereby increasing the irreversible consumption of lithium ions and reducing the capacity retention rate of the secondary battery; when A1/(A2+A3) is less than 0.006, LiF in the positive electrode interface film Excessive content increases the interface resistance of the positive electrode and affects the dynamic performance of the secondary battery.
  • the first lithium salt can not only form an interface film on the negative electrode, but also form an interface film on the positive electrode, thereby improving the capacity and kinetic performance of the secondary battery.
  • the fluorosulfonic acid group in the first lithium salt can easily corrode the aluminum foil current collector, affecting the performance of the secondary battery. For example, it will increase battery polarization and irreversible capacity loss, and even affect the safety performance of the secondary battery.
  • the main surfaces are in the following aspects: some solid insoluble corrosion products will increase the internal resistance of the secondary battery; some soluble corrosion products will contaminate and intensify the decomposition of the non-aqueous electrolyte, increasing the self-discharge of the secondary battery; Al generated during the corrosion process 3+ may migrate to the negative electrode through diffusion and be reduced to aluminum dendrites.
  • the BO bond in the molecular structure of the second lithium salt can bond with Al 3+ and form a passivation film on the surface of the aluminum foil current collector.
  • the third lithium salt can be preferentially oxidized and decomposed on the surface of the aluminum foil current collector and form a passivation film. , Therefore, the non-aqueous electrolyte of the present application can passivate the aluminum foil current collector, effectively improve the corrosion of the aluminum foil current collector by the first lithium salt, and reduce the irreversible capacity loss of the secondary battery.
  • the reason why the secondary battery using the non-aqueous electrolyte of the present application can achieve good cycle performance, storage performance and dynamic performance at the same time may be due to the synergistic effect formed between the above components.
  • the first lithium salt forms an interface film on both the positive and negative electrodes, and the synergistic effect between the second lithium salt, the third lithium salt and the first lithium salt improves the ion conductivity of the non-aqueous electrolyte, thereby making up for the first lithium salt.
  • the interface side reactions between the non-aqueous electrolyte and the electrode are reduced, the irreversible consumption of active lithium ions is reduced, the capacity of the secondary battery is increased, and the gas production is reduced; in addition, the interface film formed on the surface of the positive electrode active material and the negative electrode active material With low impedance and high ionic conductivity, the internal resistance of the secondary battery is reduced.
  • A1/A2 can be 0.03 to 40, 0.03 to 30, 0.03 to 20, 0.03 to 15, 0.03 to 10, 0.03 to 8, 0.03 to 6, 0.05 to 40, 0.05 to 30, 0.05 to 20 , 0.05 to 15, 0.05 to 10, 0.05 to 8, 0.05 to 6, 0.05 to 5, 0.1 to 40, 0.1 to 30, 0.1 to 20, 0.1 to 15, 0.1 to 10, 0.1 to 8, 0.1 to 6, 0.1 to 5, 0.2 to 40, 0.2 to 30, 0.2 to 20, 0.2 to 15, 0.2 to 10, 0.2 to 8, 0.2 to 6, 0.2 to 5 or 0.2 to 2.5.
  • A1/A2 is within a suitable range, it is conducive to giving full play to the synergistic effect between the first lithium salt and the second lithium salt, thereby forming a denser, more stable and higher ionic conductivity on the surface of the negative electrode active material. interface film.
  • A1/(A2+A3) can be 0.01 to 13.5, 0.01 to 10, 0.01 to 8, 0.01 to 6, 0.01 to 5, 0.01 to 4, 0.01 to 3.5, 0.01 to 3, 0.01 to 2.5 , 0.01 to 2, 0.02 to 13.5, 0.02 to 10, 0.02 to 8, 0.02 to 6, 0.02 to 5, 0.02 to 4, 0.02 to 3.5, 0.02 to 3, 0.02 to 2.5, 0.02 to 2, 0.1 to 13.5, 0.1 to 10, 0.1 to 8, 0.1 to 6, 0.1 to 5, 0.1 to 4, 0.1 to 3.5, 0.1 to 3, 0.1 to 2.5, 0.1 to 2 or 0.1 to 1.
  • A1/(A2+A3) is within a suitable range, it is conducive to giving full play to the synergistic effect between the first lithium salt, the second lithium salt and the third lithium salt, thereby forming a denser surface on the surface of the cathode active material. , a more stable and more ionic conductive interface film.
  • the molecular structure of the second lithium salt contains an oxalate group, its thermal stability is lower than that of the third lithium salt. It will be oxidized to form carbon dioxide gas when heated. Therefore, when its content is high, it may reduce the thermal stability of the non-aqueous electrolyte. stability and increase the gas production of secondary batteries. Since the ionic radius of BF 4 - is small and easy to associate, when the content of the third lithium salt is high, the ionic conductivity of the non-aqueous electrolyte may be reduced.
  • the non-aqueous electrolyte can simultaneously have high thermal stability.
  • properties and high ionic conductivity not only can form a low-resistance and highly ionic conductive interface film on both the positive and negative electrodes, but can also better protect the aluminum foil current collector, thereby further improving the cycle performance and storage performance of the secondary battery. and dynamic properties.
  • the effect of the second lithium salt on reducing the interface resistance of the negative electrode is weak, which may not be enough to compensate for the deterioration of the third lithium salt on the dynamic performance of the secondary battery; when A3/A2 is less than 0.04, more The second lithium salt may cause the thermal stability of the non-aqueous electrolyte to decrease and the storage performance of the secondary battery to deteriorate.
  • A3/A2 is 0.1 to 30, 0.1 to 25, 0.1 to 20, 0.1 to 18, 0.1 to 15, 0.1 to 13.5, 0.1 to 12, 0.1 to 11, 0.1 to 10, 0.1 to 9, 0.1 to 8, 0.1 to 7, 0.1 to 6, 0.1 to 5, 0.5 to 30, 0.5 to 25, 0.5 to 20, 0.5 to 18, 0.5 to 15, 0.5 to 13.5, 0.5 to 12, 0.5 to 11, 0.5 to 10, 0.5 to 9, 0.5 to 8, 0.5 to 7, 0.5 to 6, 0.5 to 5, 1 to 30, 1 to 25, 1 to 20, 1 to 18, 1 to 15, 1 to 13.5, 1 to 12, 1 to 11, 1 to 10, 1 to 9, 1 to 8, 1 to 7, 1 to 6 or 1 to 5.
  • A3/A2 is within a suitable range, it is conducive to giving full play to the synergistic effect between the second lithium salt and the third lithium salt, thereby further improving the cycle performance, storage performance and kinetic performance of the secondary battery.
  • A1 is 0.005% to 0.2%.
  • A1 is 0.005% to 0.18%, 0.005% to 0.16%, 0.005% to 0.14%, 0.005% to 0.12%, 0.005% to 0.1%, 0.005% to 0.08%, 0.008% to 0.18%, 0.008% to 0.16%, 0.008% to 0.14%, 0.008% to 0.12%, 0.008% to 0.1%, 0.008% to 0.08%, 0.01% to 0.18%, 0.01% to 0.16%, 0.01% to 0.14%, 0.01% to 0.12 %, 0.01% to 0.1% or 0.01% to 0.08%.
  • the molecular structure of the second lithium salt contains an oxalate group, which will be oxidized to form carbon dioxide gas when heated, reducing the thermal stability of the non-aqueous electrolyte.
  • A2 is 0.005% to 0.3%.
  • A2 is 0.01% to 0.3%, 0.01% to 0.26%, 0.01% to 0.22%, 0.01% to 0.2%, 0.01% to 0.18%, 0.01% to 0.16%, 0.01% to 0.14%, 0.01% to 0.12%, 0.01% to 0.1%, 0.02% to 0.3%, 0.02% to 0.26%, 0.02% to 0.22%, 0.02% to 0.2%, 0.02% to 0.18%, 0.02% to 0.16%, 0.02% to 0.14 %, 0.02% to 0.12%, 0.02% to 0.1%, 0.05% to 0.3%, 0.05% to 0.26%, 0.05% to 0.22%, 0.05% to 0.2%, 0.05% to 0.18%, 0.05% to 0.16%, 0.05% to 0.14%, 0.05% to 0.12% or 0.05% to 0.1%.
  • A3 is 0.01% to 0.5%.
  • A3 can be 0.01% to 0.45%, 0.01% to 0.4%, 0.01% to 0.35%, 0.01% to 0.3%, 0.01% to 0.25%, 0.01% to 0.2%, 0.01% to 0.15%, 0.01 % to 0.1%, 0.02% to 0.45%, 0.02% to 0.4%, 0.02% to 0.35%, 0.02% to 0.3%, 0.02% to 0.25%, 0.02% to 0.2%, 0.02% to 0.15% or 0.02% to 0.1%.
  • R 1 represents a fluorine atom or a partially or fully fluorinated C1-C6 alkyl group.
  • R 1 represents a fluorine atom or a partially or fully fluorinated methyl, ethyl, or propyl group. More alternatively, R 1 represents a fluorine atom, trifluoromethyl, difluoromethyl or monofluoromethyl.
  • the first lithium salt includes at least one of the following compounds:
  • R 2 and R 3 represent fluorine atoms or fluorine-containing groups.
  • the presence of fluorine atoms or fluorine-containing groups helps to form a thinner positive electrode interface film and/or negative electrode interface film, thereby contributing to the uniform transmission of lithium ions. It can also effectively inhibit the formation of lithium dendrites.
  • R 2 and R 3 each independently represent a fluorine atom or at least one of the group consisting of the following groups that are partially or fully fluorinated: C1-C6 alkyl, C2-C6 Alkenyl, C2-C6 alkynyl, C6-C8 aryl, C1-C6 alkoxy, C2-C6 alkenyloxy, C2-C6 alkynyloxy, C6-C8 aryloxy.
  • R 2 and R 3 each independently represent a fluorine atom or at least one of the group consisting of the following groups that are partially or fully fluorinated: methyl, ethyl, propyl, phenyl, methyl Oxy, ethoxy, propoxy, phenoxy. More optionally, R 2 and R 3 both represent fluorine atoms.
  • the second lithium salt includes at least one of the following compounds:
  • the electrolyte salt further includes at least one of a fourth lithium salt and a fifth lithium salt.
  • the fourth lithium salt is lithium hexafluorophosphate, and its mass content in the non-aqueous electrolyte is A4.
  • the fifth lithium salt is lithium bisfluorosulfonimide.
  • A5 its mass content in the non-aqueous electrolyte is A5, based on the total mass of the non-aqueous electrolyte, the non-aqueous electrolyte satisfies: A4 + A5 is 10% to 20%, optionally 10% to 18%, 10% to 17%, 10% to 16%, 10% to 15%, 12% to 18%, 12% to 17%, 12% to 16% or 12% to 15%.
  • the non-aqueous electrolyte of the present application uses lithium hexafluorophosphate and/or lithium bisfluorosulfonyl imide as the main lithium salt.
  • Lithium hexafluorophosphate has the characteristics of high ionic conductivity and resistance to corrosion of aluminum foil current collectors.
  • As the main lithium salt it can improve the overall ionic conductivity and thermal stability of the non-aqueous electrolyte.
  • the chemical formula of 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. An interfacial film with lower impedance and higher thermal stability, thereby reducing side reactions between the negative active material and the non-aqueous electrolyte.
  • the non-aqueous electrolyte uses lithium hexafluorophosphate as the main lithium salt, that is, A5 is 0%, A4 is 10% to 20%, optionally 10% to 18%, 10% to 17%, 10 % to 16%, 10% to 15%, 12% to 18%, 12% to 17%, 12% to 16% or 12% to 15%.
  • the non-aqueous electrolyte uses lithium bisfluorosulfonyl imide as the main lithium salt, A4 is 0%, A5 is 10% to 20%, optionally 10% to 18%, 10% to 17%, 10% to 16%, 10% to 15%, 12% to 18%, 12% to 17%, 12% to 16% or 12% to 15%.
  • the electrolyte salt may include both a fourth lithium salt and a fifth lithium salt.
  • A4/A5 is 0.2 to 3, more optionally 0.3 to 2, 0.4 to 1.8 or 0.5 to 1.5. Therefore, the non-aqueous electrolyte is not easily hydrolyzed, and can also achieve higher thermal stability while helping to form an interface film with lower impedance.
  • the non-aqueous electrolyte solution satisfies (A4+A5)/(A1+A2+A3) of 10 to 200.
  • (A4+A5)/(A1+A2+A3) is 15 to 250, 20 to 120, 40 to 100 or 40 to 80.
  • the mass ratio of the main lithium salt and the auxiliary lithium salt is within a suitable range, it helps the non-aqueous electrolyte to have higher thermal stability, higher ion conductivity and wider electrochemical window at the same time, and the The non-aqueous electrolyte can also passivate the aluminum foil current collector and form a dense, stable, low-resistance and highly ionic conductive interface film on the surfaces of both the positive and negative active materials.
  • the non-aqueous electrolyte may also include other electrolyte salts, such as lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), and lithium difluorophosphate (LiPO 2 F 2 ). , at least one of lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • These other electrolyte salts can serve as auxiliary lithium salts to further improve the interfacial 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 content of these other electrolyte salts in the non-aqueous electrolyte solution is below 1%, more optionally below 0.5%, based on the total mass of the non-aqueous electrolyte solution.
  • the non-aqueous solvent may include at least one of a first solvent, a second solvent, and a third solvent.
  • the first solvent is a cyclic carbonate compound, which may include, for example, at least one of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).
  • the first solvent includes ethylene carbonate (EC).
  • the second solvent is a chain carbonate compound, which may include, for example, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate At least one of ester (MPC) and ethyl propyl carbonate (EPC).
  • the second solvent includes at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC). More optionally, the second solvent includes ethyl methyl carbonate (EMC), diethyl carbonate (DEC) or a combination thereof.
  • the non-aqueous solvent includes at least a first solvent and a second solvent.
  • the content of the above-mentioned electrolyte salt is high, the viscosity of the non-aqueous electrolyte increases and the ionic conductivity decreases, which is not conducive to the formation of a dense, stable and low-impedance interfacial film.
  • the first solvent has a higher dielectric constant, it can increase the conductivity of the non-aqueous electrolyte, and because the second solvent has a smaller viscosity, it can reduce the viscosity of the non-aqueous electrolyte. Therefore, when the non-aqueous solvent includes both the first solvent and the second solvent, it helps the non-aqueous electrolyte to have appropriate viscosity and ionic conductivity, which is beneficial to the transport of lithium ions.
  • the non-aqueous solvent may also include a third solvent.
  • the third solvent is a carboxylate compound, which may include, for example, methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), At least one of ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).
  • the third solvent has the advantages of low viscosity and high dielectric constant. Its application in the non-aqueous electrolyte helps the non-aqueous electrolyte to have appropriate viscosity and ionic conductivity, which is beneficial to the transmission of lithium ions.
  • the mass content of the first solvent in the non-aqueous solvent is B1
  • the mass content of the second solvent in the non-aqueous solvent is B2
  • the mass content of the third solvent in the non-aqueous solvent is B2.
  • the mass content of the non-aqueous solvent is B3, which is based on the total mass of the non-aqueous solvent, and the non-aqueous solvent satisfies: B1 is 10% to 30%, B2 is 50% to 90%, and B3 is 0% to 20%.
  • the third solvent has poor oxidation resistance and is prone to oxidative decomposition when stored in a high charge state, so its content should not be too high.
  • B3 is 0%. In some embodiments, B3 is 2% to 20%, optionally 5% to 10%.
  • B1/(B2+B3) is 0.1 to 0.45, optionally 0.2 to 0.3.
  • the non-aqueous solvent contains an appropriate content of the first solvent, especially when it contains an appropriate content of ethylene carbonate
  • the free radicals formed by the decomposition of the second lithium salt can induce the ring opening and polymerization of the ethylene carbonate, causing the formation of ethylene carbonate on the surface of the negative active material.
  • the interface film is denser and smoother, which can effectively inhibit the growth of dendrites.
  • the non-aqueous solvent of the present application may also include other solvents other than the above-mentioned first solvent, second solvent, and third solvent.
  • 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 non-aqueous electrolyte further includes: a first additive, including fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate
  • a first additive including fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • DTD vinyl sulfate
  • PS 1,3-propanesulfonate
  • At least one of the acid lactones (PS) has a mass content in the non-aqueous electrolyte solution of C1, and based on the total mass of the non-aqueous electrolyte solution, C1 is 0.05% to 2%.
  • C1 is 0.1% to 2%, 0.1% to 1.5%, 0.1% to 1.2%, 0.1% to 1%, 0.1% to 0.8%, 0.1% to 0.6% or 0.1% to 0.5%
  • the non-aqueous electrolyte further includes: a first additive, including fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate
  • a first additive including fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • DTD vinyl sulfate
  • PS acid lactones
  • its mass content in the non-aqueous electrolyte is C1 based on the total mass of the non-aqueous electrolyte
  • the content of the first additive is C1, bisfluorosulfonate
  • the content A5 of the lithium imide and the content B1 of the first solvent satisfy (C1+A5)/B1 of 0.3 to 0.8, optionally 0.3 to 0.6.
  • the first additive helps to form a film on the surface of the positive electrode and the negative electrode to reduce continued side reactions, thereby improving at least one of the cycle performance, storage performance and kinetic performance of the secondary battery, but the content of the first additive is relatively high.
  • the positive electrode interface impedance and/or the negative electrode interface impedance increases, affecting the power performance of the secondary battery.
  • Lithium bisfluorosulfonyl imide can improve the ionic conductivity and thermal stability of non-aqueous electrolyte, and reduce the positive electrode interface resistance and/or negative electrode interface resistance, but it has certain corrosion on the aluminum foil current collector, and its high content will affect Cycling performance of secondary batteries.
  • the first solvent has a high dielectric constant, which helps to dissociate the lithium salt, so it can improve the ionic conductivity of the non-aqueous electrolyte to a certain extent.
  • the viscosity on the other hand, will affect the thermal stability of the non-aqueous electrolyte and the storage performance of the secondary battery.
  • the inventor found that by controlling (C1+A5)/B1 between 0.3 and 0.8, it is helpful to give full play to the synergy between the above components and effectively reduce the defects of each component when used alone. , thus enabling the secondary battery to have excellent cycle performance and avoid deterioration in kinetic performance and power performance.
  • the non-aqueous electrolyte solution further includes: a second additive including at least one of sulfamic acid and its salts.
  • the molecular formula of sulfamate is H 3 NO 3 S.
  • Sulfamate includes at least one of ammonium salt, alkali metal salt, alkaline earth metal salt, and alkaline earth metal salt.
  • sulfamate may include ammonium sulfamate.
  • the second additive includes sulfamic acid, lithium sulfamate, or a combination thereof.
  • Sulfamic acid is highly acidic and is usually used to prepare lithium bisfluorosulfonyl imide. It has not yet been found that it can be used in non-aqueous electrolytes.
  • the inventor of the present application surprisingly discovered during further research that when the non-aqueous electrolyte solution containing the above-mentioned auxiliary lithium salts (the first lithium salt, the second lithium salt and the third lithium salt) further contains an appropriate amount of sulfamic acid and its salts, Helps improve the cycle performance and kinetic performance of secondary batteries.
  • sulfamic acid and its salts help to increase the ionic conductivity of the non-aqueous electrolyte, reduce the viscosity of the non-aqueous electrolyte, and at the same time can also play a role in The role of slowly dissolving metals such as lithium dendrites can reduce the reduction and deposition of lithium elements, aluminum elements, transition metal elements, etc. on the surface of the negative active material, so that the secondary battery can have improved cycle performance and kinetic properties.
  • the mass content of the second additive in the non-aqueous electrolyte is C2, and based on the total mass of the non-aqueous electrolyte, C2 is 0.005% to 0.1%, optionally 0.005 % to 0.05%.
  • the non-aqueous electrolyte solution may also include the above-mentioned first additive and second additive at the same time.
  • the non-aqueous electrolyte solution of the present application can be prepared according to conventional methods in this field.
  • the additive, the non-aqueous solvent, the electrolyte salt, etc. can be mixed uniformly to obtain a non-aqueous electrolyte solution.
  • the order of adding each material is not particularly limited.
  • the additive, the electrolyte salt, etc. can be added to the non-aqueous 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 freshly prepared non-aqueous electrolyte can be directly obtained, or the non-aqueous electrolyte can be obtained from a 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.
  • a second aspect of the embodiment of the present application provides a secondary battery.
  • the secondary battery includes an electrode assembly, a non-aqueous electrolyte and an outer packaging, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of the first aspect of the present application.
  • the secondary battery of the present application can take into account good cycle performance, storage performance and dynamic performance at the same time.
  • the secondary battery of the present application may be a lithium secondary battery, particularly a lithium ion secondary battery.
  • the electrode assembly usually includes a positive electrode piece, a negative electrode piece and an isolation film.
  • the isolation film is set between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows lithium ions to pass through.
  • the secondary battery of the present application uses the non-aqueous electrolyte of the first aspect of the present application, which helps to form a dense, stable, low-resistance and highly ionic conductive interface film on the surfaces of both the positive electrode active material and the negative electrode active material, thereby enabling Balance the charge transfer resistance of the positive and negative electrodes to reduce the difference and improve the performance of the secondary battery.
  • the charge transfer resistance of the positive electrode piece is Rct1
  • the charge transfer resistance of the negative electrode piece is Rct2
  • Rct1/Rct2 is 0.5 to 2, optionally 1.25 to 2, 1.3 to 2, 1.35 to 2, 1.4 to 2, 1.25 to 1.8, 1.3 to 1.8, 1.35 to 1.8, 1.4 to 1.8, 1.25 to 1.6, 1.3 to 1.6, 1.35 to 1.6 or 1.4 to 1.6.
  • the charge transfer resistance of the positive electrode piece is obtained by the following test method: assemble the positive electrode piece into a symmetrical battery, use the electrochemical AC impedance method of the electrochemical workstation to test its electrochemical impedance spectrum, draw the Nyquist diagram, and use the equivalent
  • the circuit curve fitting method was used to analyze the obtained Nyquist diagram, and the diameter of the semicircle was used as the charge transfer resistance of the positive electrode piece as Rct1.
  • the test voltage can be 10mV and the test frequency can be 0.1Hz to 100KHz.
  • the positive electrode piece can be disassembled from the secondary battery. For safety reasons, the secondary battery is generally kept in a fully discharged state.
  • the charge transfer resistance of the negative electrode plate is obtained by the following test method: assemble the negative electrode plate into a symmetrical battery, use the electrochemical AC impedance method of the electrochemical workstation to test its electrochemical impedance spectrum, draw a Nyquist diagram, and use an equivalent circuit
  • the obtained Nyquist diagram was analyzed by the curve fitting method, and the charge transfer resistance of the negative electrode piece was taken as the diameter of the semicircle as Rct2.
  • the test voltage can be 10mV and the test frequency can be 0.1Hz to 100KHz.
  • the negative electrode piece can be disassembled from the secondary battery. For safety reasons, the secondary battery is generally kept in a fully discharged state.
  • the non-aqueous electrolyte includes a first electrolyte that infiltrates the electrode assembly and a second electrolyte located between the electrode assembly and the outer package.
  • the first electrolyte is obtained by the following test method: after the secondary battery is discharged to the discharge cut-off voltage, the electrode assembly is disassembled and centrifuged, and then the liquid obtained by the centrifugation is the third electrolyte. An electrolyte.
  • the second electrolyte is a free electrolyte, which can be obtained from the liquid injection port of the secondary battery.
  • the sum of the mass contents of the first lithium salt, the second lithium salt, the third lithium salt, the first additive and the second additive in the first electrolyte is X1, based on the total mass of the first electrolyte, so The sum of the mass contents of the first lithium salt, the second lithium salt, the third lithium salt, the first additive and the second additive in the second electrolyte solution is X2, based on the total mass of the second electrolyte solution, and 0.5 ⁇ X1/X2 ⁇ 1.
  • the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and including a positive active material.
  • the positive electrode current collector has two surfaces opposite in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the cathode film 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. properties, the crystal structure of the layered material obtained after doping is more stable, and can further improve the electrochemical performance of secondary batteries, such as cycle performance, kinetic performance, 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, thus enabling the secondary battery to have better cycle performance and kinetic 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 surface of the positive electrode active material can also be formed.
  • a low-resistance interfacial film is formed, and the B atoms in the second lithium salt and third lithium salt structures can easily combine with the O atoms in the positive electrode active material, reducing the charge transfer resistance of the positive electrode active material, thus reducing the activity of lithium ions in the positive electrode. Diffusion resistance within the bulk phase of a material.
  • the low-cobalt or cobalt-free cathode active material can have a significantly improved lithium ion diffusion rate, and the low-cobalt or cobalt-free cathode active material body
  • the lithium ions in the phase can be replenished to the surface in time to avoid excessive delithiation on the surface of low-cobalt or cobalt-free cathode active materials, thereby stabilizing the crystal structure of low-cobalt or cobalt-free cathode active materials.
  • the crystal structure of the low-cobalt or cobalt-free cathode active material is more stable, it can greatly reduce the change in structural properties, chemical properties or electrochemical properties 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 instability, for example, 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 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.8 Co 0.05 Mn 0.15 O 2 , 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 0.3 O 2 , LiNi 0.65 Co 0.05 Mn 0. 3 O 2 , LiNi At least one of 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 mass percentage of the layered material with the molecular formula Li a Ni b Co c Mn d Ale M f O g A h is 80% to 99%.
  • the mass percentage of the 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 mass percentage 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 positive electrode film layer optionally further includes a positive electrode conductive agent.
  • a 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%.
  • the positive electrode film layer optionally further includes a positive electrode 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 film layer.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum 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 film 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 negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative active material may be a negative active material known in the art for secondary batteries.
  • 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 electrode film layer optionally further includes a negative electrode conductive agent.
  • a 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 electrode conductive agent is less than 5%.
  • the negative electrode film layer optionally further includes a negative electrode 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.
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • 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%.
  • the negative electrode film layer optionally includes other additives.
  • other auxiliaries may include thickeners, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • CMC-Na sodium carboxymethylcellulose
  • PTC thermistor materials such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • the mass percentage of the other additives is less than 2%.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper 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 copper, copper 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 negative electrode film 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 isolation film is disposed between the positive electrode piece and the negative electrode piece, and mainly plays a role in preventing short circuit between the positive electrode and the negative electrode, and at the same time allows lithium ions to pass through.
  • 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 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 secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and non-aqueous electrolyte.
  • 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 method for preparing a secondary battery further includes a secondary liquid injection process performed after the formation process, and the first lithium salt, the second lithium salt, the third lithium salt, and the second injected non-aqueous electrolyte are The contents of the trilithium salt, the first additive and the second additive are lower than the first injected non-aqueous electrolyte solution.
  • the second injected non-aqueous electrolyte contains less auxiliary lithium salts and additives, thereby increasing the stability of the non-aqueous electrolyte.
  • the liquid injection coefficient of the secondary battery is 2.0g/Ah to 5.0g/Ah
  • the mass of the non-aqueous electrolyte is the first injected non-aqueous electrolyte and the second injected non-aqueous electrolyte. the sum of the masses.
  • 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 51 and Comparative Examples 1 to 10 were all prepared according to the following methods.
  • a porous polyethylene (PE) film is used as the isolation membrane.
  • Electrode assembly Stack and wind the positive electrode sheet, isolation film, and negative electrode sheet in order to obtain the electrode assembly; put the electrode assembly into the outer packaging, add the above-mentioned non-aqueous electrolyte, and then go through the processes of packaging, standing, forming, aging, etc. , get the secondary battery.
  • the secondary battery At 25°C, charge the secondary battery to 4.3V with a constant current of 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 0.5C and adjust When the secondary battery reaches 50% SOC, the voltage of the secondary battery at this time is recorded as U 1 ; the secondary battery is discharged with a constant current of 4C I 1 for 30 seconds, using a 0.1 second sampling point, and the voltage at the end of the discharge is recorded as U 2 .
  • the initial DC internal resistance of the secondary battery is represented by the discharge DC internal resistance of the secondary battery at 50% SOC.
  • the initial DC internal resistance of the secondary battery (m ⁇ ) (U 1 -U 2 )/I 1 .
  • the positive electrode piece is disassembled, the positive electrode piece is assembled into a symmetrical battery, the above-mentioned non-aqueous electrolyte is injected, and then the battery of Solartron 1470E CellTest multi-channel electrochemical workstation is used.
  • the chemical AC impedance method was used to test and the Nyquist diagram was drawn; Zview software was used to analyze the obtained Nyquist diagram using the equivalent circuit curve fitting method, and the semicircle diameter was used as the charge transfer resistance of the positive electrode piece as Rct1.
  • the test voltage is 10mV and the test frequency is 0.1Hz to 100KHz.
  • the negative electrode pieces are disassembled, and the negative electrode pieces are assembled into a symmetrical battery.
  • the above-mentioned non-aqueous electrolyte is injected into the battery, and then the battery of Solartron 1470E CellTest multi-channel electrochemical workstation is used.
  • the chemical AC impedance method was used to test and the Nyquist diagram was drawn; Zview software was used to analyze the obtained Nyquist diagram using the equivalent circuit curve fitting method, and the semicircle diameter was used as the charge transfer resistance of the negative electrode piece as Rct2.
  • the test voltage is 10mV and the test frequency is 0.1Hz to 100KHz.
  • each of the above tests can be performed on at least 3 parallel samples and the average value is taken as the test result.
  • Table 1 shows the non-aqueous electrolyte preparation parameters of Examples 1 to 35 and Comparative Examples 1 to 10.
  • Table 2 shows the test results of Examples 1 to 35 and Comparative Examples 1 to 10 according to the above performance test method.
  • Table 3 shows the non-aqueous electrolyte preparation parameters of Examples 36 to 51
  • Table 4 shows the test results of Examples 36 to 51 obtained according to the above performance test method.
  • the secondary battery can At the same time, it takes into account higher capacity retention rate, lower volume expansion rate and lower internal resistance.
  • the non-aqueous electrolyte does not use the auxiliary lithium salt of the present application, or only uses part of the auxiliary lithium salt of the present application.
  • the capacity retention rate of the secondary battery prepared is low, and the volume expansion rate and internal content of the secondary battery are low. The resistance is higher.
  • Comparative Example 10 uses LiBOB as an auxiliary lithium salt. The volume expansion rate of the secondary battery obtained is improved to a certain extent, but the capacity retention rate is still low and the internal resistance is still high.
  • the non-aqueous electrolyte solution includes both the fourth lithium salt and the fifth lithium salt, and the mass ratio A4/A5 of the two is between 0.2 and 3, optionally between 0.5 and 1.5. between them, it helps to further improve the overall performance of the secondary battery.

Abstract

本申请提供一种非水电解液以及包含其的二次电池、电池模块、电池包及用电装置。所述非水电解液包含电解质盐以及非水溶剂，所述电解质盐包括第一锂盐、第二锂盐和第三锂盐，基于所述非水电解液的总质量计，所述第一锂盐的含量A1、所述第二锂盐的含量A2和所述第三锂盐的含量A3满足：A1+A2+A3在1％以下，A1/A2为0.016至40，并且A1/(A2+A3)为0.006至13.5。本申请能够使二次电池同时兼顾良好的循环性能、存储性能和动力学性能。

Description

非水电解液以及包含其的二次电池、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，具体涉及一种非水电解液以及包含其的二次电池、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，其综合性能受到越来越多的关注，例如二次电池需要同时满足能量密度高、循环寿命长、安全性能高、倍率性能好等。非水电解液在正极和负极之间起到传导离子的作用，其是影响二次电池性能的关键因素之一，因此，亟需提供一种综合性能良好的非水电解液。
发明内容
本申请的目的在于提供一种非水电解液以及包含其的二次电池、电池模块、电池包及用电装置，其能够使二次电池同时兼顾良好的循环性能、存储性能和动力学性能。
本申请第一方面提供一种非水电解液，包含电解质盐以及非水溶剂，其中，所述电解质盐包括：第一锂盐，具有式1所示结构，R 1表示氟原子或者部分氟化或全部氟化的C1-C10的烷基，其在所述非水电解液中的质量含量为A1，基于所述非水电解液的总质量计；第二锂盐，具有式2所示结构，R 2、R 3分别独立地表示氟原子或者由部分氟化或全部氟化的以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，其在所述非水电解液中的质量含量为A2，基于所述非水电解液的总质量计；第三锂盐，选自四氟硼酸锂，其在所述非水电解液中的质量含量为A3，基于所述非水电解液的总质量计；
Figure PCTCN2022094228-appb-000001
所述非水电解液满足：A1+A2+A3在1％以下，A1/A2为0.016至40，并且A1/(A2+A3)为0.006至13.5。
发明人通过大量研究发现，通过在非水电解液中采用上述第一锂盐、第二锂盐和第三锂盐作为辅助锂盐控制其总含量在1％以下，并合理调节第一锂盐的含量A1、第二锂盐的含量A2、第三锂盐的含量A3使其满足A1/A2为0.016至40，并且A1/(A2+A3)为0.006至13.5，得到的非水电解液能够同时具有较高的热稳定性、较高的离子电导率以及较宽的电化学窗口，并且所述非水电解液还能够钝化铝箔集流体并在正极活性材料和负极活性材料表面均形成致密、稳定、低阻抗且高导离子性的界面膜，由此采用本申请非水电解液的二次电池能够同时兼顾良好的循环性能、存储性能和动力学性能。
在本申请的任意实施方式中，A1/A2为0.03至10，可选地为0.1至5。由此有利于充分发挥第一锂盐和第二锂盐之间的协同作用效果，由此能够在负极活性材料表面形成更致密、更稳定且导离子性更高的界面膜。
在本申请的任意实施方式中，A1/(A2+A3)为0.02至3.5，可选地为0.1至2。由此有利于充分发挥第一锂盐、第二锂盐和第三锂盐之间的协同作用效果，由此能够在正极活性材料表面形成更致密、更稳定且导离子性更高的界面膜。
在本申请的任意实施方式中，所述非水电解液还满足A3/A2为0.04至30，可选地为1至10。由此有利于充分发挥第二锂盐和第三锂盐之间的协同作用效果，从而能够进一步改善二次电池的循环性能、存储性能和动力学性能。
在本申请的任意实施方式中，A1为0.005％至0.2％，可选地为0.01％至0.1％。
在本申请的任意实施方式中，A2为0.005％至0.3％，可选地为0.01％至0.3％。
在本申请的任意实施方式中，A3为0.01％至0.5％，可选地为0.02％至0.2％。
在本申请的任意实施方式中，所述第一锂盐包括如下化合物中的至少一种：
Figure PCTCN2022094228-appb-000002
在本申请的任意实施方式中，所述第二锂盐包括如下化合物中的至少一种：
Figure PCTCN2022094228-appb-000003
Figure PCTCN2022094228-appb-000004
在本申请的任意实施方式中，所述电解质盐还包括第四锂盐、第五锂盐中的至少一种，所述第四锂盐为六氟磷酸锂，其在所述非水电解液中的质量含量为A4，基于所述非水电解液的总质量计，所述第五锂盐为双氟磺酰亚胺锂，其在所述非水电解液中的质量含量为A5，基于所述非水电解液的总质量计，所述非水电解液满足：A4+A5为10％至20％，可选地为10％至18％。
在本申请的任意实施方式中，A4/A5为0.2至3，可选地为0.5至1.5。由此所述非水电解液不易水解，并且还能够同时兼顾更高的热稳定性，同时，有助于形成阻抗更低的界面膜。
在本申请的任意实施方式中，(A4+A5)/(A1+A2+A3)为10至200，可选地为20至120，更可选地为40至100。由此有助于非水电解液同时具有较高的热稳定性、较高的离子电导率以及较宽的电化学窗口，并且所述非水电解液还能够钝化铝箔集流体并在正极活性材料和负极活性材料表面均形成致密、稳定、低阻抗且高导离子性的界面膜。
在本申请的任意实施方式中，所述非水溶剂包括：第一溶剂，包括碳酸乙烯酯、碳酸丙烯酯、碳酸亚丁酯中的至少一种，其在所述非水溶剂中的质量含量为B1，基于所述非水溶剂的总质量计；第二溶剂，包括碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯中的至少一种，其在所述非水溶剂中的质量含量为B2，基于所述非水溶剂的总质量计；第三溶剂，包括甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯中的至少一种，其在所述非水溶剂中的质量含量为B3，基于所述非水溶剂的总质量计，所述非水电解液满足：B1为10％至30％，B2为50％至90％，B3为0％至20％。
在本申请的任意实施方式中，B1/(B2+B3)为0.1至0.45，可选地为0.2至0.3。由此有助于使负极活性材料表面形成的界面膜更加致密、光滑，由此可以有效抑制枝晶的生长。
在本申请的任意实施方式中，所述非水电解液还包括：第一添加剂，包括氟代碳酸乙烯酯、碳酸亚乙烯酯、硫酸乙烯酯、1,3-丙磺酸内酯中的至少一种，其在所述非水电解液中的质量含量为C1，基于所述非水电解液的总质量计，C1为0.05％至2％，可选地为0.1％至1％。第一添加剂有助于进一步改善正极和/或负极的界面性能，从而进一步改善二次电池的循环性能、存储性能和动力学性能中的至少一者。
在本申请的任意实施方式中，所述非水电解液还满足(C1+A5)/B1为0.3至0.8，可 选地为0.3至0.6。由此有助于充分发挥上述各组分之间的协同作用，并有效降低各组分单独使用时的缺陷，使二次电池具有优异循环性能，并且还能避免动力学性能和功率性能变差。
在本申请的任意实施方式中，所述非水电解液还包括：第二添加剂，包括氨基磺酸及其盐中的至少一种，其在所述非水电解液中的质量含量为C2，基于所述非水电解液的总质量计，C2为0.005％至0.1％，可选地为0.005％至0.05％。由此有助于改善二次电池的循环性能和动力学性能。
本申请第二方面提供一种二次电池，包括电极组件、非水电解液以及外包装，其中，所述非水电解液为本申请第一方面的非水电解液，由此本申请的二次电池能够同时兼顾良好的循环性能、存储性能和动力学性能。
在本申请的任意实施方式中，所述电极组件包括正极极片和负极极片，所述正极极片的电荷转移电阻为Rct1，所述负极极片的电荷转移电阻为Rct2，并且Rct1/Rct2为0.5至2，可选地为1.25至2。由此正极和负极的电荷转移电阻差异较小，能够更好地提高二次电池的性能发挥。
所述正极极片的电荷转移电阻通过如下测试方法得到：将所述正极极片组装成对称电池，采用电化学工作站的电化学交流阻抗法测试其电化学阻抗谱，绘制Nyquist图，利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为所述正极极片的电荷转移电阻为Rct1。所述负极极片的电荷转移电阻如下测试方法得到：将所述负极极片组装成对称电池，采用电化学工作站的电化学交流阻抗法测试其电化学阻抗谱，绘制Nyquist图，利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为所述负极极片的电荷转移电阻为Rct2。
在本申请的任意实施方式中，所述非水电解液包括浸润所述电极组件的第一电解液以及位于所述电极组件和所述外包装之间的第二电解液，所述第一电解液中第一锂盐、第二锂盐、第三锂盐、第一添加剂和第二添加剂的质量含量之和为X1，基于所述第一电解液的总质量计，所述第二电解液中第一锂盐、第二锂盐、第三锂盐、第一添加剂和第二添加剂的质量含量之和为X2，基于所述第二电解液的总质量计，并且0.5≤X1/X2＜1。所述第一电解液通过如下测试方法得到：将所述二次电池放电至放电截止电压后拆解出所述电极组件并对其进行离心处理，之后取离心处理得到的液体即为所述第一电解液。
在本申请的任意实施方式中，所述正极极片包括分子式为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。
在本申请的一些实施方式中，M选自Si、Ti、Mo、V、Ge、Se、Zr、Nb、Ru、Pd、Sb、Ce、Te及W中的至少一种。
在本申请的一些实施方式中，A选自F、N、P及S中的至少一种，可选地，A选自F。
在本申请的一些实施方式中，0＜b＜0.98，可选地，0.50≤b＜0.98。
在本申请的一些实施方式中，c＝0。
在本申请的一些实施方式中，0＜c≤0.20，可选地，0＜c≤0.10。
在本申请的一些实施方式中，d＝0并且0＜e＜0.50，可选地，d＝0并且0＜e≤0.10。
在本申请的一些实施方式中，e＝0并且0＜d＜0.50，可选地，e＝0并且0＜d≤0.10。
在本申请的一些实施方式中，0＜d＜0.50并且0＜e＜0.50，可选地，0＜d≤0.30并且0＜e≤0.10。
本申请第三方面提供一种电池模块，包括本申请第二方面的二次电池。
本申请第四方面提供一种电池包，包括本申请第二方面的二次电池、第三方面的电池模块中的一种。
本申请第五方面提供一种用电装置，包括本申请第二方面的二次电池、第三方面的电池模块、第四方面的电池包中的至少一种。
本申请的二次电池能够同时兼顾良好的循环性能、存储性能和动力学性能，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非水电解液以及包含其的二次电池、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)。
在本申请中，术语“多个”、“多种”是指两个或两种以上。
在本文中，术语“烷基”是指饱和烃基，既包括直链结构也包括支链结构。烷基的实例包括但不限于甲基、乙基、丙基(如正丙基、异丙基)、丁基(如正丁基、异丁基、仲丁基、叔丁基)、戊基(如正戊基、异戊基、新戊基)。在各种实施方式中，C1-C10的烷基即烷基可含有1至10个碳原子。
术语“烯基”是指含有碳-碳双键的不饱和烃基，既包括直链结构也包括支链结构，碳-碳双键的数量可以为一个也可以为多个。烯基的实例包括但不限于乙烯基、丙烯基、烯丙基、丁二烯基。在各种实施方式中，C2-C10的烯基即烯基可含有2至10个碳原子。
术语“炔基”是指含有碳-碳三键的不饱和烃基，既包括直链结构也包括支链结构，碳-碳三键的数量可以为一个也可以为多个。炔基的实例包括但不限于乙炔基、丙炔基、丁炔基、丁二炔基。在各种实施方式中，C2-C10的炔基即炔基可含有2至10个碳原子。
术语“芳基”是指具有芳香族性质的碳环体系，其结构可以是单环、多环或稠环。芳基的实例包括但不限于苯基。在各种实施方式中，C6-C8的芳基即芳基可含有6至8个 碳原子。
在本文中，术语“烷氧基”是指含有氧原子(-O-)的烷基，术语“烯氧基”是指含有氧原子(-O-)的烯基，术语“炔氧基”是指含有氧原子(-O-)的烷基，术语“芳氧基”是指含有氧原子(-O-)的烷基。
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。
随着二次电池的应用及推广，其综合性能受到越来越多的关注。非水电解液是影响二次电池性能的关键因素之一，目前商业化应用最广的非水电解液体系为六氟磷酸锂的混合碳酸酯溶液，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LiF和PF 5。LiF会增加界面阻抗；PF 5具有较强的路易斯酸性，会与溶剂分子中氧原子上的孤对电子作用而使溶剂发生分解；此外，PF 5对于非水电解液中微量的水分具有较高的敏感性，遇水会产生HF，从而增加非水电解液的酸度，进而容易腐蚀正极活性材料和正极集流体、造成正极活性材料中过渡金属离子溶出。另外，正极活性材料中过渡金属离子溶出并迁移到负极后，会被还原成过渡金属，这样产生的过渡金属相当于“催化剂”，会催化负极活性材料表面的固体电解质界面膜(solid electrolyte interphase，SEI)分解，产生副产物。所述副产物的一部分为气体，因此导致会二次电池发生膨胀，影响二次电池的安全性能；所述副产物的另一部分沉积在负极活性材料表面，会阻碍锂离子传输通道，造成二次电池阻抗增加，从而影响二次电池的动力学性能；此外，为补充损失的界面膜，非水电解液和电池内部的活性锂离子被不断消耗，会给二次电池容量保持率带来不可逆的影响。
因此，有必要提供一种综合性能良好的非水电解液。
本申请的发明人在进行大量研究后惊喜发现，当非水电解液含有合适含量的辅助锂盐时，能够使二次电池同时兼顾良好的循环性能、存储性能和动力学性能。
非水电解液
具体地，本申请实施方式第一方面提供一种非水电解液，包含电解质盐以及非水溶剂。
所述电解质盐包括：第一锂盐，具有式1所示结构，R 1表示氟原子或者部分氟化或全部氟化的C1-C10的烷基，其在所述非水电解液中的质量含量为A1，基于所述非水电解液的总质量计；第二锂盐，具有式2所示结构，R 2、R 3分别独立地表示氟原子或者由部分氟化或全部氟化的以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，其在所述非水电解液中的质量含量为A2，基于所述非水电解液的总质量计；第三锂盐，选自四氟硼酸锂，其在所述非水电解液中的质量含量为A3，基于所述非水电解液的总质量计。
Figure PCTCN2022094228-appb-000005
Figure PCTCN2022094228-appb-000006
在本申请中，所述非水电解液满足：A1+A2+A3在1％以下，A1/A2为0.016至40，并且A1/(A2+A3)为0.006至13.5。
发明人通过大量研究发现，通过在非水电解液中采用上述第一锂盐、第二锂盐和第三锂盐作为辅助锂盐控制其总含量在1％以下，并合理调节第一锂盐的含量A1、第二锂盐的含量A2、第三锂盐的含量A3使其满足A1/A2为0.016至40，并且A1/(A2+A3)为0.006至13.5，得到的非水电解液能够同时具有较高的热稳定性、较高的离子电导率以及较宽的电化学窗口，并且所述非水电解液还能够钝化铝箔集流体并在正极活性材料和负极活性材料表面均形成致密、稳定、低阻抗且高导离子性的界面膜，由此采用本申请非水电解液的二次电池能够同时兼顾良好的循环性能、存储性能和动力学性能。
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，通过合理调节第一锂盐的含量A1和第二锂盐的含量A2使其满足A1/A2为0.016至40时，有助于在负极活性材料表面形成致密、稳定且高导离子性的界面膜。第一锂盐含有磺酸根阴离子，能够还原形成Li 2SO 4等高导离子化合物，从而有利于提高负极界面膜的离子传输特性；第二锂盐的分子结构中含有一个草酸根基团，其还原产物可与界面膜中的(LiOCO 2CH 2) 2等有机组分进一步反应形成复杂且稳定的低聚物，充分包覆在负极活性材料表面，阻止非水电解液与负极活性材料直接接触，并减少非水溶剂嵌入负极活性材料。当A1/A2大于40时，负极界面膜无法充分覆盖在负极活性材料表面，由此增加了锂离子的不可逆消耗，降低了二次电池的容量保持率；当A1/A2小于0.016时，负极界面膜的离子传输特性较差，导致二次电池的内阻增加，动力学性能变差。
第二，通过合理调节第一锂盐的含量A1、第二锂盐的含量A2、第三锂盐的含量A3使其满足A1/(A2+A3)为0.006至13.5时，有助于在正极活性材料表面形成致密、稳定且含有少量LiF的界面膜，增加正极界面膜的锂离子传输通道、降低锂离子传输阻力；同时抑制正极活性材料的不可逆相变，保持正极活性材料的结构稳定性，由此二次电池具有更好的容量发挥。此外，第二锂盐分子结构中的B原子容易与正极活性材料中的O原子结合，由此还能够降低正极活性材料的电荷转移阻抗、降低锂离子在正极活性材料体相内的扩散阻力。当A1/(A2+A3)大于13.5时，第二锂盐和第三锂盐无法有效弥补过多的第一锂盐对电池内阻的恶化，由此二次电池的动力学性能较差，同时正极界面膜无法充分覆盖在正极活性材料表面，由此增加了锂离子的不可逆消耗，降低了二次电池的容量保持率；当A1/(A2+A3)小于0.006时，正极界面膜中LiF含量过多，由此增加了正极界面阻抗，影响了二次电池的动力学性能。
第三，第一锂盐不仅可以在负极形成界面膜，还可以在正极形成界面膜，从而改善二次电池的容量发挥和动力学性能。但是，第一锂盐中的氟磺酸基团容易腐蚀铝箔集流体，影响二次电池的性能，例如会增加电池极化和不可逆容量损失，甚至影响二次电池的安全性能。主要表面在以下几个方面：部分固体不溶性腐蚀产物会增加二次电池内 阻；部分可溶性腐蚀产物会污染并加剧非水电解液的分解，增加二次电池的自放电；腐蚀过程中产生的Al 3+可能经扩散作用迁移到负极并被还原成铝枝晶。第二锂盐分子结构中的B-O键可以与Al 3+键合并在铝箔集流体表面形成一层钝化膜，第三锂盐可以优先在铝箔集流体表面被氧化分解并形成一层钝化膜，因此，本申请的非水电解液能够钝化铝箔集流体，有效改善第一锂盐对铝箔集流体的腐蚀，减少二次电池的不可逆容量损失。
因此，采用本申请非水电解液的二次电池能够同时兼顾良好的循环性能、存储性能和动力学性能的原因可能在于上述各组分之间形成了协同作用效果。通过第一锂盐在正极和负极均形成界面膜，通过第二锂盐、第三锂盐和第一锂盐之间的协同作用提高非水电解液的离子电导率，从而弥补第一锂盐解离度小、离子电导率低的缺陷；通过第一锂盐和第二锂盐之间的协同作用在负极活性材料表面形成致密、稳定、低阻抗且高导离子性的界面膜；通过第一锂盐、第二锂盐和第三锂盐之间的协同作用在正极活性材料表面形成致密、稳定且含有少量LiF的界面膜。由此，非水电解液与电极之间的界面副反应减少、活性锂离子不可逆消耗减少，二次电池的容量发挥增加、产气量减少；此外，正极活性材料和负极活性材料表面形成的界面膜具有低阻抗和高导离子性，二次电池的内阻降低。
在一些实施例中，A1/A2可以为0.03至40，0.03至30，0.03至20，0.03至15，0.03至10，0.03至8，0.03至6，0.05至40，0.05至30，0.05至20，0.05至15，0.05至10，0.05至8，0.05至6，0.05至5，0.1至40，0.1至30，0.1至20，0.1至15，0.1至10，0.1至8，0.1至6，0.1至5，0.2至40，0.2至30，0.2至20，0.2至15，0.2至10，0.2至8，0.2至6，0.2至5或0.2至2.5。A1/A2在合适的范围内时，有利于充分发挥第一锂盐和第二锂盐之间的协同作用效果，由此能够在负极活性材料表面形成更致密、更稳定且导离子性更高的界面膜。
在一些实施例中，A1/(A2+A3)可以为0.01至13.5，0.01至10，0.01至8，0.01至6，0.01至5，0.01至4，0.01至3.5，0.01至3，0.01至2.5，0.01至2，0.02至13.5，0.02至10，0.02至8，0.02至6，0.02至5，0.02至4，0.02至3.5，0.02至3，0.02至2.5，0.02至2，0.1至13.5，0.1至10，0.1至8，0.1至6，0.1至5，0.1至4，0.1至3.5，0.1至3，0.1至2.5，0.1至2或0.1至1。A1/(A2+A3)在合适的范围内时，有利于充分发挥第一锂盐、第二锂盐和第三锂盐之间的协同作用效果，由此能够在正极活性材料表面形成更致密、更稳定且导离子性更高的界面膜。
由于第二锂盐的分子结构中含有一个草酸根基团，其热稳定性低于第三锂盐，受热时会被氧化形成二氧化碳气体，因此其含量较高时，可能降低非水电解液的热稳定性，增加二次电池的产气量。由于BF 4 -的离子半径较小，容易缔合，因此第三锂盐的含量较高时，可能降低非水电解液的离子电导率。发明人通过大量研究进一步发现，当合理调节第二锂盐的含量A2、第三锂盐的含量A3使其满足A3/A2为0.04至30时，非水电解液能够同时具有较高的热稳定性和较高的离子电导率，不仅能够在正极和负极均形成低阻抗且高导离子性的界面膜，还能够更好地保护铝箔集流体，从而进一步改善二次电池的循环性能、存储性能和动力学性能。当A3/A2大于30时，第二锂盐对负极界面阻抗的降低作用较弱，可能不足以弥补第三锂盐对二次电池动力学性能的恶化；当A3/A2小于0.04时，较多的第二锂盐可能导致非水电解液的热稳定性降低，二次电池的存储性能变差。
在一些实施例中，可选地，A3/A2为0.1至30，0.1至25，0.1至20，0.1至18，0.1至15，0.1至13.5，0.1至12，0.1至11，0.1至10，0.1至9，0.1至8，0.1至7，0.1至6，0.1至5，0.5至30，0.5至25，0.5至20，0.5至18，0.5至15，0.5至13.5，0.5至12，0.5至11，0.5至10，0.5至9，0.5至8，0.5至7，0.5至6，0.5至5，1至30，1至25，1至20，1至18，1至15，1至13.5，1至12，1至11，1至10，1至9，1至8，1至7，1至6或1至5。A3/A2在合适的范围内时，有利于充分发挥第二锂盐和第三锂盐之间的协同作用效果，从而能够进一步改善二次电池的循环性能、存储性能和动力学性能。
第一锂盐在非水溶剂中容易形成缔合离子对，降低非水电解液的离子电导率。在一些实施例中，A1为0.005％至0.2％。可选地，A1为0.005％至0.18％，0.005％至0.16％，0.005％至0.14％，0.005％至0.12％，0.005％至0.1％，0.005％至0.08％，0.008％至0.18％，0.008％至0.16％，0.008％至0.14％，0.008％至0.12％，0.008％至0.1％，0.008％至0.08％，0.01％至0.18％，0.01％至0.16％，0.01％至0.14％，0.01％至0.12％，0.01％至0.1％或0.01％至0.08％。
第二锂盐分子结构中含有一个草酸根基团，受热时会被氧化形成二氧化碳气体，降低非水电解液的热稳定性。在一些实施例中，A2为0.005％至0.3％。可选地，A2为0.01％至0.3％，0.01％至0.26％，0.01％至0.22％，0.01％至0.2％，0.01％至0.18％，0.01％至0.16％，0.01％至0.14％，0.01％至0.12％，0.01％至0.1％，0.02％至0.3％，0.02％至0.26％，0.02％至0.22％，0.02％至0.2％，0.02％至0.18％，0.02％至0.16％，0.02％至0.14％，0.02％至0.12％，0.02％至0.1％，0.05％至0.3％，0.05％至0.26％，0.05％至0.22％，0.05％至0.2％，0.05％至0.18％，0.05％至0.16％，0.05％至0.14％，0.05％至0.12％或0.05％至0.1％。
第三锂盐含量增加时，非水电解液的离子电导率降低，不利于在负极活性材料表面形成稳定的界面膜。在一些实施例中，A3为0.01％至0.5％。可选地，A3可以为0.01％至0.45％，0.01％至0.4％，0.01％至0.35％，0.01％至0.3％，0.01％至0.25％，0.01％至0.2％，0.01％至0.15％，0.01％至0.1％，0.02％至0.45％，0.02％至0.4％，0.02％至0.35％，0.02％至0.3％，0.02％至0.25％，0.02％至0.2％，0.02％至0.15％或0.02％至0.1％。
在一些实施例中，R 1表示氟原子或者部分氟化或全部氟化的C1-C6的烷基。可选地，R 1表示氟原子或者部分氟化或全部氟化的甲基、乙基、丙基。更可选地，R 1表示氟原子、三氟甲基、二氟甲基或者一氟甲基。
作为示例，所述第一锂盐包括如下化合物中的至少一种：
Figure PCTCN2022094228-appb-000007
R 2、R 3表示氟原子或含氟基团，氟原子或含氟基团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，R 2、R 3分别独立地表示氟原子或者由部分氟化或全部氟化的以下基团组成的组中的至少一种：C1-C6的烷基、C2-C6的烯基、C2-C6的炔基、C6-C8的芳基、C1-C6的烷氧基、C2-C6的烯氧基、C2-C6的炔氧基、C6-C8的芳氧基。可选地，R 2、R 3分别独立地表示氟原子或者由部分氟化或全部氟化的以下基团组成的组中的至少一种：甲基、乙基、丙基、苯基、甲氧基、乙氧基、丙氧基、苯氧基。更可选地，R 2、R 3均表示氟原子。
作为示例，所述第二锂盐包括如下化合物中的至少一种：
Figure PCTCN2022094228-appb-000008
在一些实施例中，所述电解质盐还包括第四锂盐、第五锂盐中的至少一种。所述第四锂盐为六氟磷酸锂，其在所述非水电解液中的质量含量为A4，基于所述非水电解液的总质量计，所述第五锂盐为双氟磺酰亚胺锂，其在所述非水电解液中的质量含量为A5，基于所述非水电解液的总质量计，所述非水电解液满足：A4+A5为10％至20％，可选地为10％至18％，10％至17％，10％至16％，10％至15％，12％至18％，12％至17％，12％至16％或12％至15％。
本申请的非水电解液以六氟磷酸锂和/或双氟磺酰亚胺锂作为主锂盐。六氟磷酸锂具有离子电导率高且不易腐蚀铝箔集流体的特性，作为主锂盐可以提高非水电解液整体的离子电导率和热稳定性。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。
在一些实施例中，所述非水电解液以六氟磷酸锂作为主锂盐，即A5为0％，A4为 10％至20％，可选地为10％至18％，10％至17％，10％至16％，10％至15％，12％至18％，12％至17％，12％至16％或12％至15％。
在一些实施例中，所述非水电解液以双氟磺酰亚胺锂作为主锂盐，A4为0％，A5为10％至20％，可选地为10％至18％，10％至17％，10％至16％，10％至15％，12％至18％，12％至17％，12％至16％或12％至15％。
在一些实施例中，所述电解质盐可以同时包括第四锂盐和第五锂盐。可选地，A4/A5为0.2至3，更可选地为0.3至2，0.4至1.8或0.5至1.5。由此所述非水电解液不易水解，并且还能够同时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，所述非水电解液满足(A4+A5)/(A1+A2+A3)为10至200。可选地，(A4+A5)/(A1+A2+A3)为15至250，20至120，40至100或40至80。主锂盐和辅助锂盐的质量比在合适的范围内时，有助于非水电解液同时具有较高的热稳定性、较高的离子电导率以及较宽的电化学窗口，并且所述非水电解液还能够钝化铝箔集流体并在正极活性材料和负极活性材料表面均形成致密、稳定、低阻抗且高导离子性的界面膜。
在一些实施例中，所述非水电解液还可以包括其他电解质盐，例如包括高氯酸锂(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。这些其他电解质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，这些其他电解质盐在所述非水电解液中的总质量含量在1％以下，更可选地在0.5％以下，基于所述非水电解液的总质量计。
在一些实施例中，所述非水溶剂可以包括第一溶剂、第二溶剂、第三溶剂中的至少一种。
所述第一溶剂为环状碳酸酯化合物，例如可以包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸亚丁酯(BC)中的至少一种。可选地，所述第一溶剂包括碳酸乙烯酯(EC)。
所述第二溶剂为链状碳酸酯化合物，例如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，所述第二溶剂包括碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)中的至少一种。更可选地，所述第二溶剂包括碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)或其组合。
在一些实施例中，可选地，所述非水溶剂至少包括第一溶剂和第二溶剂。上述电解质盐的含量较高时，非水电解液的粘度增加、离子电导率降低，不利于形成致密、稳定且低阻抗的界面膜。而第一溶剂由于具有较高的介电常数，可以增加非水电解液的电导率，第二溶剂由于具有较小的粘度，可以降低非水电解液的粘度。因此，当非水溶剂同时包括第一溶剂和第二溶剂时，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。
在一些实施例中，所述非水溶剂还可以包括第三溶剂。所述第三溶剂为羧酸酯化合物，例如可以包括甲酸甲酯(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。第三溶剂具有低粘度、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。
在一些实施例中，所述第一溶剂在所述非水溶剂中的质量含量为B1，所述第二溶剂在所述非水溶剂中的质量含量为B2，所述第三溶剂在所述非水溶剂中的质量含量为B3，均基于所述非水溶剂的总质量计，并且所述非水溶剂满足：B1为10％至30％，B2为50％至90％，B3为0％至20％。
第三溶剂的耐氧化能力较差，在高荷电状态存储时容易发生氧化分解，因此其含量不宜太高。在一些实施例中，B3为0％。在一些实施例中，B3为2％至20％，可选地为5％至10％。
在一些实施例中，B1/(B2+B3)为0.1至0.45，可选地为0.2至0.3。非水溶剂含有合适含量的第一溶剂时，特别地，含有合适含量的碳酸乙烯酯时，第二锂盐分解形成的自由基可以诱导碳酸乙烯酯开环、聚合，使负极活性材料表面形成的界面膜更加致密、光滑，由此可以有效抑制枝晶的生长。
本申请的非水溶剂还可以包含上述第一溶剂、第二溶剂、第三溶剂以外的其他溶剂。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，所述非水电解液还包括：第一添加剂，包括氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)、1,3-丙磺酸内酯(PS)中的至少一种，其在所述非水电解液中的质量含量为C1，基于所述非水电解液的总质量计，C1为0.05％至2％。可选地，C1为0.1％至2％，0.1％至1.5％，0.1％至1.2％，0.1％至1％，0.1％至0.8％，0.1％至0.6％或0.1％至0.5％。第一添加剂有助于进一步改善正极和/或负极的界面性能，从而进一步改善二次电池的循环性能、存储性能和动力学性能中的至少一者。
在一些实施例中，所述非水电解液还包括：第一添加剂，包括氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)、1,3-丙磺酸内酯(PS)中的至少一种，其在所述非水电解液中的质量含量为C1，基于所述非水电解液的总质量计，并且第一添加剂的含量C1、双氟磺酰亚胺锂的含量A5、第一溶剂的含量B1满足(C1+A5)/B1为0.3至0.8，可选地为0.3至0.6。第一添加剂有助于在正极和负极表面成膜以降低持续的副反应，由此能改善二次电池的循环性能、存储性能和动力学性能中的至少一者，但第一添加剂的含量较多时，正极界面阻抗和/或负极界面阻抗增加，影响二次电池的功率性能。双氟磺酰亚胺锂能提高非水电解液的离子电导率和热稳定性，降低正极界面阻抗和/或负极界面阻抗，但对铝箔集流体有一定的腐蚀，其含量较高时会影响二次电池的循环性能。第一溶剂具有较高的介电常数，有助于锂盐的解离，因此能在一定程度上提高非水电解液的离子电导率，但其含量较多时，一方面会增加非水电解液的粘度，另外一方面会影响非水电解液的热稳定性，影响二次电池的存储性能。发明人在进一步研究中发现，通过控制(C1+A5)/B1在0.3至0.8之间，有助于充分发挥上述各组分之间的协同作用，并有效降低各组分单独使用时的缺陷，由此可以使二次电池具有优异循环性能，并且还能避免动力学性能和功率性能变差。
在一些实施例中，所述非水电解液还包括：第二添加剂，包括氨基磺酸及其盐中的至少一种。氨基磺酸分子式为H 3NO 3S，氨基磺酸盐包括铵盐、碱金属盐、碱土金属盐、 类碱土金属盐中的至少一种，作为示例，氨基磺酸盐可以包括氨基磺酸铵、氨基磺酸锂、氨基磺酸钠、氨基磺酸锌中的至少一种。可选地，所述第二添加剂包括氨基磺酸、氨基磺酸锂或其组合。
氨基磺酸的酸性较强，通常用于制备双氟磺酰亚胺锂，目前尚未发现可以将其应用于非水电解液中。本申请的发明人在进一步研究中惊喜发现，当含有上述辅助锂盐(第一锂盐、第二锂盐和第三锂盐)的非水电解液进一步含有适量氨基磺酸及其盐时，有助于改善二次电池的循环性能和动力学性能。尽管机理尚不明确，发明人推测可能的原因为，氨基磺酸及其盐有助于提高非水电解液的离子电导率、降低非水电解液的粘度，同时还能在一定程度上起到缓慢溶解锂枝晶等金属的作用，由此能够减少在负极活性材料表面还原沉积的锂单质、铝单质以及过渡金属单质等，从而二次电池能够具有改善的循环性能和动力学性能。
氨基磺酸及其盐易溶于水且酸性较强，当其含量较高时，会腐蚀正极活性材料和破坏正极界面膜和/或负极界面膜的稳定性。在一些实施例中，所述第二添加剂在所述非水电解液中的质量含量为C2，基于所述非水电解液的总质量计，C2为0.005％至0.1％，可选地为0.005％至0.05％。
在一些实施例中，所述非水电解液还可以同时包括上述第一添加剂和第二添加剂。
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，可以将所述添加剂、所述非水溶剂、所述电解质盐等混合均匀，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，可以将所述添加剂、所述电解质盐等加入到所述非水溶剂中混合均匀，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，可直接取新鲜制备的非水电解液，也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。
二次电池
本申请实施方式第二方面提供一种二次电池，所述二次电池包括电极组件、非水电解液以及外包装，其中，所述非水电解液为本申请第一方面的非水电解液，由此本申请的二次电池能够同时兼顾良好的循环性能、存储性能和动力学性能。
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。
电极组件通常包括正极极片、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。
本申请的二次电池采用本申请第一方面的非水电解液，有助于在正极活性材料和负极活性材料表面均形成致密、稳定、低阻抗且高导离子性的界面膜，由此能够平衡正极和负极的电荷转移电阻，减小其差异，提高二次电池的性能发挥。
本申请的二次电池中，所述正极极片的电荷转移电阻为Rct1，所述负极极片的电 荷转移电阻为Rct2，并且Rct1/Rct2为0.5至2，可选地1.25至2，1.3至2，1.35至2，1.4至2，1.25至1.8，1.3至1.8，1.35至1.8，1.4至1.8，1.25至1.6，1.3至1.6，1.35至1.6或1.4至1.6。由此正极和负极的电荷转移电阻差异较小，能够更好地提高二次电池的性能发挥。
所述正极极片的电荷转移电阻通过如下测试方法得到：将所述正极极片组装成对称电池，采用电化学工作站的电化学交流阻抗法测试其电化学阻抗谱，绘制Nyquist图，利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为所述正极极片的电荷转移电阻为Rct1。测试电压可为10mV，测试频率可为0.1Hz至100KHz。所述正极极片可从二次电池中拆解得到，为了安全起见，一般使二次电池处于满放状态。
所述负极极片的电荷转移电阻如下测试方法得到：将所述负极极片组装成对称电池，采用电化学工作站的电化学交流阻抗法测试其电化学阻抗谱，绘制Nyquist图，利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为所述负极极片的电荷转移电阻为Rct2。测试电压可为10mV，测试频率可为0.1Hz至100KHz。所述负极极片可从二次电池中拆解得到，为了安全起见，一般使二次电池处于满放状态。
所述非水电解液包括浸润所述电极组件的第一电解液以及位于所述电极组件和所述外包装之间的第二电解液。所述第一电解液通过如下测试方法得到：将所述二次电池放电至放电截止电压后拆解出所述电极组件并对其进行离心处理，之后取离心处理得到的液体即为所述第一电解液。所述第二电解液为游离电解液，可以从二次电池的注液口导出获得。
所述第一电解液中第一锂盐、第二锂盐、第三锂盐、第一添加剂和第二添加剂的质量含量之和为X1，基于所述第一电解液的总质量计，所述第二电解液中第一锂盐、第二锂盐、第三锂盐、第一添加剂和第二添加剂的质量含量之和为X2，基于所述第二电解液的总质量计，并且0.5≤X1/X2＜1。
[正极极片]
在一些实施例中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面且包括正极活性材料的正极膜层。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，所述正极膜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。
所述正极膜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，能进一步提升二次电池的电化学性能，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，由此能使二次电池具有更好的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意外发现，当合理调节第二锂盐的含量A2和第三锂盐的含量A3并使其满足A3/A2为0.04至30时，还能在正极活性材料表面形成低阻抗的界面膜，且第二锂盐和第三锂盐结构中的B原子还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电阻，从而降低锂离子在正极活性材料体相内的扩散阻力。因此，当非水电解液中含有合适含量的第二锂盐和第三锂盐时，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 0.8Co 0.1Mn 0.1O 2、LiNi 0.6Co 0.2Mn 0.2O 2、LiNi 0.5Co 0.2Mn 0.3O 2、LiNi 0.8Co 0.05Mn 0.15O 2、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，基于正极膜层的总质量计，分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料的质量百分含量为80％至99％。例如，分子式为Li aNi bCo cMn dAl eM fO gA h的层状材料的质量百分含量可以为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的层状材料的质量百分含量为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，所述正极膜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，基于所述正极膜层的总质量计，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，所述正极膜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，基于所述正极膜层的总质量计，所述正极粘结剂的质量百分含量在5％以下。
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。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。
所述正极膜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。[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面且包括负极活性材料的负极膜层。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，所述负极膜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。
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，所述负极膜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，基于所述负极膜层的总质量计，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，所述负极膜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，基于所述负极膜层的总质量计，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，所述负极膜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，基于所述负极膜层的总质量计，所述其他助剂的质量百分含量在2％以下。
在一些实施例中，所述负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，可采用铜箔。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，金属材料可选自铜、铜合金、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。
所述负极膜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。
[隔离膜]
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。
在一些实施例中，所述二次电池可包括外包装。该外包装可用于封装上述电极组件及非水电解液。
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。在一些实施例中，所述二次电池的制备方法还包括在化成工序后进行的二次注液工艺，并且第二次注入的非水电解液中第一锂盐、第二锂盐、第三锂盐、第一添加剂和第二添加剂的含量低于第一次注入的非水电解液。通过增加二次注液工艺有助于降低成本，同时能够改善二次电池的性能。这是由于，辅助锂盐和添加剂中的部分组分自身稳定性较差，仅采用一次注液工艺时，容易降低非水电解液的稳定性，而本申请的二次电池采用二次注液工艺，并 且第二次注入的非水电解液含有更少的辅助锂盐和添加剂，由此能够增加非水电解液的稳定性。在一些实施例中，二次电池的注液系数为2.0g/Ah至5.0g/Ah，非水电解液的质量为第一次注入的非水电解液和第二次注入的非水电解液的质量总和。
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。
用电装置
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51和对比例1至10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 0.6Co 0.2Mn 0.2O 2、导电剂炭黑、粘结剂聚偏氟乙烯(PVDF)按重量比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。
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(SuperP)按重量比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。
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
将锂盐、添加剂加入非水溶剂中混合均匀，得到非水电解液。各组分的组成及其含量分别如表1和表3所示。在表1和表3中，第一锂盐、第二锂盐、第三锂盐、第四锂盐、第五锂盐、第一添加剂、第二添加剂的含量均基于非水电解液的总质量计，第一溶剂、第二溶剂和第三溶剂的含量均基于非水溶剂的总质量计，“/”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；将电极组件放入外包装中，加入上述非水电解液，经封装、静置、化成、老化等工序后，得到二次电池。
测试部分
(1)二次电池常温循环性能测试
在25℃下，将二次电池以1C恒流充电至4.3V，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25℃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％。
(2)二次电池高温循环性能测试
在45℃下，将二次电池以1C恒流充电至4.3V，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％。
(3)二次电池高温存储性能测试
在60℃下，将二次电池以1C恒流充电到4.3V，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％。
(4)二次电池初始直流内阻测试
在25℃下，将二次电池以1C恒流充电到4.3V，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0.5C恒流放电并调整二次电池至50％SOC，此时二次电池的电压记为U 1；将二次电池以4C的电流I 1恒流放电30秒，采用0.1秒采点，放电末期电压记为U 2。用二次电池50％SOC时的放电直流内阻表示二次电池的初始直流内阻，二次电池的初始直流内阻(mΩ)＝(U 1-U 2)/I 1。
(5)正极极片的电荷转移电阻测试
将上述制备的二次电池满放后拆解出正极极片，将正极极片组装成对称电池，注入上述非水电解液，然后采用输力强(Solartron)1470E CellTest多通道电化学工作站的电化学交流阻抗法进行测试，绘制Nyquist图；采用Zview软件利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为正极极片的电荷转移电阻为Rct1。测试电压为10mV，测试频率为0.1Hz至100KHz。
(6)负极极片的电荷转移电阻测试
将上述制备的二次电池满放后拆解出负极极片，将负极极片组装成对称电池，注入上述非水电解液，然后采用输力强(Solartron)1470E CellTest多通道电化学工作站的电化学交流阻抗法进行测试，绘制Nyquist图；采用Zview软件利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为负极极片的电荷转移电阻为Rct2。测试电压为10mV，测试频率为0.1Hz至100KHz。
为保证测试结果可靠性，上述各测试可采用至少3个平行样本进行测试并取平均值作为测试结果。
表1给出实施例1至35和对比例1至10的非水电解液制备参数，表2给出实施例1至35和对比例1至10按照上述性能测试方法得到的测试结果。
表3给出实施例36至51的非水电解液制备参数，表4给出实施例36至51按照上述性能测试方法得到的测试结果。
Figure PCTCN2022094228-appb-000009
Figure PCTCN2022094228-appb-000010
Figure PCTCN2022094228-appb-000011
Figure PCTCN2022094228-appb-000012
Figure PCTCN2022094228-appb-000013
Figure PCTCN2022094228-appb-000014
综合实施例1至35的测试结果可知，通过在非水电解液中采用本申请的第一锂盐、第二锂盐和第三锂盐作为辅助锂盐并控制其总含量在1％以下，同时第一锂盐的含量A1、第二锂盐的含量A2、第三锂盐的含量A3满足A1/A2为0.016至40和A1/(A2+A3)为0.006至13.5时，二次电池能够同时兼顾较高的容量保持率、较低的体积膨胀率和较低的内阻。
对比例1至9中，非水电解液未采用本申请的辅助锂盐，或者仅采用本申请的部分辅助锂盐，所制备的二次电池的容量保持率较低，并且体积膨胀率和内阻较高。对比例10采用LiBOB作为辅助锂盐，所得到二次电池的体积膨胀率得到一定程度改善，但容量保持率仍较低，并且内阻仍较高。
综合实施例36至51的测试结果可知，通过在非水电解液中采用第一添加剂和/或第二添加剂，有助于改善二次电池的循环性能、存储性能和动力学性能中的至少一者。
综合实施例37至43的测试结果可知，非水电解液同时包括第四锂盐和第五锂盐，并且二者的质量比A4/A5在0.2至3之间，可选地在0.5至1.5之间时，有助于进一步提升二次电池的综合性能。
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. 一种非水电解液，包含电解质盐以及非水溶剂，其中，
    所述电解质盐包括：
    第一锂盐，具有式1所示结构，R 1表示氟原子或者部分氟化或全部氟化的C1-C10的烷基，其在所述非水电解液中的质量含量为A1，基于所述非水电解液的总质量计；
    第二锂盐，具有式2所示结构，R 2、R 3分别独立地表示氟原子或者由部分氟化或全部氟化的以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，其在所述非水电解液中的质量含量为A2，基于所述非水电解液的总质量计；
    第三锂盐，选自四氟硼酸锂，其在所述非水电解液中的质量含量为A3，基于所述非水电解液的总质量计；
    Figure PCTCN2022094228-appb-100001
    所述非水电解液满足：A1+A2+A3在1％以下，A1/A2为0.016至40，并且A1/(A2+A3)为0.006至13.5。
  2. 根据权利要求1所述的非水电解液，其中，
    A1/A2为0.03至10，可选地为0.1至5；和/或，
    A1/(A2+A3)为0.02至3.5，可选地为0.1至2。
  3. 根据权利要求1或2所述的非水电解液，其中，所述非水电解液还满足A3/A2为0.04至30，可选地为1至10。
  4. 根据权利要求1-3中任一项所述的非水电解液，其中，所述非水电解液满足如下条件(1)至(3)中的至少一者：
    (1)A1为0.005％至0.2％，可选地为0.01％至0.1％；
    (2)A2为0.005％至0.3％，可选地为0.01％至0.3％；
    (3)A3为0.01％至0.5％，可选地为0.02％至0.2％。
  5. 根据权利要求1-4中任一项所述的非水电解液，
    所述第一锂盐包括如下化合物中的至少一种：
    Figure PCTCN2022094228-appb-100002
    Figure PCTCN2022094228-appb-100003
    和/或，
    所述第二锂盐包括如下化合物中的至少一种：
    Figure PCTCN2022094228-appb-100004
  6. 根据权利要求1-5中任一项所述的非水电解液，其中，所述电解质盐还包括第四锂盐、第五锂盐中的至少一种，
    所述第四锂盐为六氟磷酸锂，其在所述非水电解液中的质量含量为A4，基于所述非水电解液的总质量计，
    所述第五锂盐为双氟磺酰亚胺锂，其在所述非水电解液中的质量含量为A5，基于所述非水电解液的总质量计，
    所述非水电解液满足：A4+A5为10％至20％，可选地为10％至18％；
    可选地，A4/A5为0.2至3，更可选地为0.5至1.5。
  7. 根据权利要求6所述的非水电解液，其中，(A4+A5)/(A1+A2+A3)为10至200，可选地为20至120，更可选地为40至100。
  8. 根据权利要求1-7中任一项所述的非水电解液，其中，所述非水溶剂包括：
    第一溶剂，包括碳酸乙烯酯、碳酸丙烯酯、碳酸亚丁酯中的至少一种，其在所述非水溶剂中的质量含量为B1，基于所述非水溶剂的总质量计；
    第二溶剂，包括碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯中的至少一种，其在所述非水溶剂中的质量含量为B2，基于所述非水溶剂的总质量计；
    第三溶剂，包括甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯中的至少一种，其在所述非水溶剂中的质量含量为B3，基于所述非水溶剂的总质量计，
    可选地，所述非水电解液满足：B1为10％至30％，B2为50％至90％，B3为0％至20％；
    可选地，B1/(B2+B3)为0.1至0.45，更可选地为0.2至0.3。
  9. 根据权利要求1-8中任一项所述的非水电解液，其中，所述非水电解液还包括：第一添加剂，包括氟代碳酸乙烯酯、碳酸亚乙烯酯、硫酸乙烯酯、1,3-丙磺酸内酯中的至少一种，其在所述非水电解液中的质量含量为C1，基于所述非水电解液的总质量计，可选地，C1为0.05％至2％，更可选地为0.1％至1％。
  10. 根据权利要求9所述的非水电解液，其中，所述非水电解液还满足(C1+A5)/B1为0.3至0.8，可选地为0.3至0.6。
  11. 根据权利要求1-10中任一项所述的非水电解液，其中，所述非水电解液还包括：第二添加剂，包括氨基磺酸及其盐中的至少一种，其在所述非水电解液中的质量含量为C2，基于所述非水电解液的总质量计，可选地，C2为0.005％至0.1％，更可选地为0.005％至0.05％。
  12. 一种二次电池，包括电极组件、非水电解液以及外包装，其中，所述非水电解液为根据权利要求1-11中任一项所述的非水电解液。
  13. 根据权利要求11述的二次电池，其中，所述电极组件包括正极极片和负极极片，所述正极极片的电荷转移电阻为Rct1，所述负极极片的电荷转移电阻为Rct2，并且Rct1/Rct2为0.5至2，可选地为1.25至2，
    所述正极极片的电荷转移电阻通过如下测试方法得到：将所述正极极片组装成对称电池，采用电化学工作站的电化学交流阻抗法测试其电化学阻抗谱，绘制Nyquist图，利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为所述正极极片的电荷转移电阻为Rct1，
    所述负极极片的电荷转移电阻如下测试方法得到：将所述负极极片组装成对称电池，采用电化学工作站的电化学交流阻抗法测试其电化学阻抗谱，绘制Nyquist图，利用等效电路曲线拟合法对所得到的Nyquist图进行分析，以半圆直径作为所述负极极片的电荷转移电阻为Rct2。
  14. 根据权利要求12或13所述的二次电池，其中，所述非水电解液包括浸润所述电极组件的第一电解液以及位于所述电极组件和所述外包装之间的第二电解液，
    所述第一电解液中第一锂盐、第二锂盐、第三锂盐、第一添加剂和第二添加剂的质量含量之和为X1，基于所述第一电解液的总质量计，
    所述第二电解液中第一锂盐、第二锂盐、第三锂盐、第一添加剂和第二添加剂的质量含量之和为X2，基于所述第二电解液的总质量计，
    并且0.5≤X1/X2＜1，
    所述第一电解液通过如下测试方法得到：将所述二次电池放电至放电截止电压后拆解出所述电极组件并对其进行离心处理，之后取离心处理得到的液体即为所述第一电解液。
  15. 根据权利要求12至14中任一项所述的二次电池，其中，所述正极极片包括分子式为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。
  16. 根据权利要求15所述的二次电池，其中，Li aNi bCo cMn dAl eM fO gA h满足如下条件(1)至(8)中的至少一者：
    (1)M选自Si、Ti、Mo、V、Ge、Se、Zr、Nb、Ru、Pd、Sb、Ce、Te及W中的至少一种；
    (2)A选自F、N、P及S中的至少一种，可选地，A选自F；
    (3)0＜b＜0.98，可选地，0.50≤b＜0.98；
    (4)c＝0；
    (5)0＜c≤0.20，可选地，0＜c≤0.10；
    (6)d＝0并且0＜e＜0.50，可选地，d＝0并且0＜e≤0.10；
    (7)e＝0并且0＜d＜0.50，可选地，e＝0并且0＜d≤0.10；
    (8)0＜d＜0.50并且0＜e＜0.50，可选地，0＜d≤0.30并且0＜e≤0.10。
  17. 一种电池模块，包括根据权利要求12-16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12-16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12-16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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