WO2023040355A1 - 负极极片及其制备方法、二次电池、电池模块、电池包、用电装置 - Google Patents

负极极片及其制备方法、二次电池、电池模块、电池包、用电装置 Download PDF

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WO2023040355A1
WO2023040355A1 PCT/CN2022/096212 CN2022096212W WO2023040355A1 WO 2023040355 A1 WO2023040355 A1 WO 2023040355A1 CN 2022096212 W CN2022096212 W CN 2022096212W WO 2023040355 A1 WO2023040355 A1 WO 2023040355A1
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negative electrode
solid electrolyte
active material
secondary battery
film
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French (fr)
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谢岚
史松君
沙莹
林真
李伟
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to EP22868732.3A priority Critical patent/EP4246609A4/en
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Priority to US18/213,269 priority patent/US20230352664A1/en
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0438—Processes of manufacture in general by electrochemical processing
    • H01M4/044—Activating, forming or electrochemical attack of the supporting material
    • H01M4/0442—Anodisation, Oxidation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the technical field of batteries, and in particular relates to a negative pole piece and a preparation method thereof, a secondary battery, a battery module, a battery pack, and an electrical device.
  • Secondary batteries rely on active ions to reciprocate and deintercalate between the positive and negative electrodes for charging and discharging. It has the outstanding characteristics of high energy density, long cycle life, no pollution, and no memory effect. Therefore, secondary batteries, as clean energy, have been gradually popularized from electronic products to large-scale devices such as electric vehicles, in order to adapt to the sustainable development strategy of the environment and energy. However, secondary batteries also have their disadvantages, such as reduced capacity and increased gas production during long-term storage, which may even affect the safety of users.
  • the purpose of the present application is to provide a negative electrode sheet and its preparation method, a secondary battery, a battery module, a battery pack, and an electrical device, aiming at effectively reducing the gas production of the secondary battery and improving the storage performance of the secondary battery.
  • the first aspect of the present application provides a negative electrode sheet.
  • 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 comprising a negative electrode active material, at least part of the surface of the negative electrode active material has an artificial solid electrolyte interface film, and the artificial solid electrolyte interface film includes A first inorganic lithium salt, wherein the first inorganic lithium salt is selected from one or both of Li 2 CO 3 and Li 2 SO 3 .
  • the artificial SEI membrane has good physical and chemical stability, and is a solid electrolyte membrane with electronic insulation and good ion conductivity.
  • the artificial SEI film can inhibit the reduction and decomposition of the conventional SEI film and reduce the gas production of the secondary battery.
  • the artificial SEI film can also inhibit electrolyte salts, organic solvents, additives and impurities (such as trace amounts of H 2 O and dissolved O 2 ) in the electrolyte from obtaining electrons on the surface of the negative electrode active material and undergoing a reduction reaction, further reducing the gas production of the secondary battery . Therefore, the negative electrode sheet of the present application can effectively reduce the gas production of the secondary battery and improve the storage performance of the secondary battery.
  • the mass percentage of the first inorganic lithium salt is 20% to 90%.
  • the mass percentage of the first inorganic lithium salt is 80%-90%.
  • the mass percent content of the first inorganic lithium salt is in an appropriate range, and the artificial SEI film can continuously protect the negative electrode active material while having a lower impedance, so that the secondary battery has lower gas production and lower impedance at the same time. .
  • the artificial solid electrolyte interface film further includes Li 2 O.
  • Li 2 O can improve the stability of the artificial SEI film, so that the artificial SEI film can continuously protect the negative electrode active material, reduce the gas production of the secondary battery, and improve the storage performance of the secondary battery.
  • the mass percentage of Li 2 O is 10%-80%.
  • the mass percentage of Li 2 O is 10%-20%.
  • the artificial SEI film can continuously protect the negative electrode active material and have low impedance, so that the secondary battery has low gas production and low impedance at the same time.
  • the artificial solid electrolyte interface film is composed of the first inorganic lithium salt and Li 2 O.
  • the thickness of the artificial solid electrolyte interfacial film is 5 nm to 10 nm.
  • the artificial SEI film can continuously protect the negative electrode active material while having low impedance, so that the secondary battery has low gas production and low impedance at the same time.
  • the mass concentration deviations of C, O, S, and Li elements at any point in the artificial solid electrolyte interface film are all below 2%.
  • the artificial solid electrolyte interfacial film is located on 80% to 100% of the surface of the negative electrode active material particles.
  • the artificial solid electrolyte interface film is located on 95%-100% of the surface of the negative electrode active material particles.
  • the artificial SEI film is located on almost the entire surface of the negative electrode active material particles, which can continuously protect the negative electrode active material, further reduce the gas production of the secondary battery and improve the storage performance of the secondary battery.
  • the mass percentage of the negative active material having an artificial solid electrolyte interface film on its surface is 80% to 100%.
  • the mass percentage of the negative electrode active material with the artificial solid electrolyte interfacial film on the surface is 95%-100%.
  • Almost all of the negative electrode active material in the negative electrode film layer has an artificial SEI film on the surface, which can further reduce the gas production of the secondary battery and improve the storage performance of the secondary battery.
  • the negative electrode sheet is applied to a secondary battery, and after formation, at least part of the surface of the negative electrode active material has an artificial solid electrolyte interface film and a conventional solid electrolyte interface film on the surface of the artificial solid electrolyte interface film.
  • the second aspect of the present application provides a method for preparing a negative electrode sheet, including the following steps: S10, providing an initial negative electrode sheet, the initial negative electrode sheet includes a negative electrode current collector and is disposed on at least one surface of the negative electrode current collector and includes a negative electrode active material negative electrode film layer; S20, the lithium metal layer is arranged on the negative electrode film layer to obtain a lithium-supplementing negative electrode sheet; S30, the lithium metal in the lithium-supplementing negative electrode sheet is combined with one of O 2 and CO 2 , SO 2 One or two mixed gases react to form an artificial solid electrolyte interface film on the surface of at least part of the negative electrode active material, the artificial solid electrolyte interface film includes a first inorganic lithium salt, and the first inorganic lithium salt is selected from Li2 One or both of CO 3 and Li 2 SO 3 .
  • the mass of the lithium metal is 0.1 mg/1540 mm 2 to 2 mg/1540 mm 2 .
  • the ratio of the volume of O 2 in the mixed gas to the total volume of CO 2 and SO 2 is 1:12 ⁇ 4:1.
  • the ratio of the volume of O 2 in the mixed gas to the total volume of CO 2 and SO 2 is 1:8 ⁇ 2:1.
  • the reaction time is 1 h to 72 h.
  • the reaction time is 2h-48h.
  • the method of reacting the lithium metal in the lithium-replenishing negative electrode sheet with a mixed gas containing O 2 and one or both of CO 2 and SO 2 includes: The negative pole piece is placed in a non-aqueous organic solvent, and a mixed gas containing O 2 and one or both of CO 2 and SO 2 is continuously passed into the non-aqueous organic solvent to make lithium metal react with the mixed gas to obtain At least part of the surface of the negative electrode active material forms an artificial solid electrolyte interface film.
  • the non-aqueous organic solvent is selected from one or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the method of reacting the lithium metal in the lithium-replenishing negative electrode sheet with a mixed gas containing O 2 and one or both of CO 2 and SO 2 includes: The negative electrode sheet is directly placed in a mixed gas containing O 2 and one or both of CO 2 and SO 2 , and the lithium metal reacts with the mixed gas to form an artificial solid electrolyte interface film on the surface of at least part of the negative active material .
  • the third aspect of the present application provides a secondary battery, which includes the negative electrode sheet according to the first aspect of the present application or the negative electrode sheet prepared according to the method described in the second aspect of the present application.
  • a fourth aspect of the present application provides a battery module, which includes the secondary battery of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery pack, which includes one of the secondary battery of the third aspect of the present application and the battery module of the fourth aspect.
  • a sixth aspect of the present application provides an electric device, which includes at least one of the secondary battery of the third aspect of the present application, the battery module of the fourth aspect, and the battery pack of the fifth aspect.
  • the secondary battery of the present application has lower gas production, and thus the secondary battery of the present application can have significantly improved storage performance.
  • the secondary battery of the present application may also have lower impedance, and improved cycle performance and rate performance.
  • the battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of a secondary battery of the present application.
  • FIG. 2 is an exploded schematic diagram of an embodiment of the secondary battery of the present application.
  • 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 view of FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of an electrical device in which a secondary battery is used as a power source of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and 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 and may be combined arbitrarily, ie 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, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, 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" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • 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 in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, 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) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • the electrolyte salt, organic solvent, additives and impurities in the electrolyte (such as trace H 2 O and dissolved O 2, etc.) will undergo a reduction reaction at the solid-liquid phase interface between the negative electrode active material and the electrolyte .
  • the products of the reduction reaction include gaseous products, liquid products and solid products.
  • Gas products include hydrocarbon gases such as C 2 H 4 and inorganic gases such as CO 2 and H 2 ; liquid products will be dissolved in the electrolyte after generation; solid products will cover the surface of the negative electrode active material to form a passivation film. That is, solid electrolyte interface film (Solid Electrolyte Interface, referred to as SEI film).
  • This SEI film mainly includes various inorganic components (such as Li 2 CO 3 , LiF, Li 2 O, LiOH, etc.) and various organic components (such as alkyl lithium carbonate ROCO 2 Li and (ROCO 2 Li) 2 , alkoxy Lithium-based ROLi, etc., specifically CH 3 OCO 2 Li, CH 3 CH 2 OCO 2 Li, (CH 2 OCO 2 Li) 2 , Li(CH 2 CH 2 OCO 2 )Li, CH 3 CH(OCO 2 Li) CH2OCO2Li , CH2 ( OCO2Li ) CH2OCO2Li , CH3CH2OLi , etc. ) .
  • This SEI film is a solid electrolyte film with electronic insulation and good ion conductivity, which can prevent the reduction reaction of the solvent on the surface of the negative electrode active material, especially avoid the damage caused by the co-intercalation of solvent molecules to the negative electrode active material. .
  • a large amount of active ions are consumed during the SEI repair process, resulting in a decrease in the capacity of the secondary battery.
  • a large amount of gas products are produced during the SEI repair process, which further aggravates the volume expansion of the secondary battery and even affects the safety of users.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer that is arranged on at least one surface of the negative electrode current collector and includes a negative electrode active material. At least part of the surface of the negative electrode active material has an artificial solid electrolyte interface film (abbreviated as an artificial SEI film), so The artificial solid electrolyte interface film includes a first inorganic lithium salt, and the first inorganic lithium salt is selected from one or both of Li 2 CO 3 and Li 2 SO 3 .
  • the electrolyte salt, organic solvent, additives and impurities in the electrolyte such as trace H2O and dissolved O2, etc.
  • the reduction reaction will continue to occur on the solid-liquid phase interface between the artificial solid electrolyte membrane and the electrolyte, forming a conventional solid electrolyte interfacial membrane (conventional SEI membrane for short).
  • the conventional solid electrolyte interfacial film mainly includes various inorganic components (such as Li 2 CO 3 , LiF, Li 2 O, LiOH, etc.) and various organic components (such as alkyl lithium carbonate ROCO 2 Li and (ROCO 2 Li) 2 , Oxylithium ROLi, etc., specifically CH 3 OCO 2 Li, CH 3 CH 2 OCO 2 Li, (CH 2 OCO 2 Li) 2 , Li(CH 2 CH 2 OCO 2 )Li, CH 3 CH(OCO 2 Li ) CH 2 OCO 2 Li, CH 2 (OCO 2 Li)CH 2 OCO 2 Li, CH 3 CH 2 OLi, etc.). Therefore, at least part of the surface of the negative electrode active material has an artificial solid electrolyte interface film and a conventional solid electrolyte interface film on the surface of the artificial solid electrolyte interface film.
  • inorganic components such as Li 2 CO 3 , LiF, Li 2 O, LiOH, etc.
  • organic components such as alkyl lithium carbonate ROCO
  • the "artificial solid electrolyte interface film” on the surface of the negative electrode active material is different from the “conventional solid electrolyte interface film” formed on the surface of the negative electrode active material during the formation of the secondary battery, and the “artificial solid electrolyte interface film” of the present application
  • the “electrolyte interface film” is formed before the secondary battery is charged for the first time (corresponding to before formation).
  • the negative electrode sheet of the present application is applied to secondary batteries.
  • a layer of conventional solid electrolyte interface film will continue to be formed on the surface of the artificial solid electrolyte membrane, and then at least part of the surface of the negative electrode active material has an artificial solid electrolyte interface film and an artificial solid electrolyte interface film on the surface of the artificial solid electrolyte membrane.
  • Conventional solid electrolyte interface membrane on the surface of the solid electrolyte interface membrane Therefore, after the negative electrode sheet of the present application is applied to a secondary battery, at least part of the surface of the negative electrode active material has a double-layer SEI film.
  • the artificial SEI membrane of the present application has good physical and chemical stability, and is a solid electrolyte membrane with electronic insulation and good ion conductivity.
  • the potential of the negative electrode continues to rise, and the conventional SEI film is easy to decompose. Because the artificial SEI film is electronically insulating, it can inhibit the reduction and decomposition of the conventional SEI film and reduce the output of the secondary battery. gas.
  • the conventional SEI film When the secondary battery is stored at low voltage, high temperature, or over-discharged for a long time, the conventional SEI film will decompose and enter the repair process. Because the artificial SEI film has electronic insulation, it can inhibit the electrolyte salt, organic solvent, and additives in the electrolyte. And impurities (such as trace amounts of H 2 O and dissolved O 2 , etc.) obtain electrons on the surface of the negative electrode active material and undergo a reduction reaction, thereby further reducing the gas production of the secondary battery.
  • impurities such as trace amounts of H 2 O and dissolved O 2 , etc.
  • the existence of the artificial SEI film can also reduce the consumption of active ions during the repair of the conventional SEI film, avoid the damage to the negative electrode active material caused by the co-intercalation of solvent molecules, and thus improve the cycle performance of the secondary battery.
  • the mass percentage of the first inorganic lithium salt is 20%-90%.
  • the mass percentage of the first inorganic lithium salt is 20%-90%, 25%-90%, 30%-90%, 35%-90%, 40%-90%, 45%-90%, 50% %-90%, 55%-90%, 60%-90%, 65%-90%, 70%-90%, 75%-90%, 80%-90%, or 85%-90%.
  • the mass percent content of the first inorganic lithium salt is in an appropriate range, and the artificial SEI film can continuously protect the negative electrode active material while having a lower impedance, so that the secondary battery has lower gas production and lower impedance at the same time. .
  • the artificial solid electrolyte interface film further includes Li2O .
  • Li 2 O can improve the stability of the artificial SEI film, so that the artificial SEI film can continuously protect the negative electrode active material, reduce the gas production of the secondary battery, and improve the storage performance of the secondary battery.
  • the Li 2 O content is 10%-80% by mass.
  • the mass percentage of Li 2 O is 10%-80%, 10%-75%, 10%-70%, 10%-65%, 10%-60%, 10%-55%, 10%- 50%, 10% ⁇ 45%, 10% ⁇ 40%, 10% ⁇ 35%,
  • the artificial SEI film can continuously protect the negative electrode active material and have low impedance, so that the secondary battery has low gas production and low impedance at the same time.
  • the artificial solid electrolyte interface film may also include a small amount of organic lithium salt, and based on the total mass of the artificial solid electrolyte interface film, the mass percentage of the organic lithium salt is less than 40%.
  • the mass percentage content of organic lithium salt is 0% ⁇ 40%, 0% ⁇ 35%, 0% ⁇ 30%, 0% ⁇ 25%, 0% ⁇ 20%, 0% ⁇ 15%, 0% ⁇ 10%, 0% to 5%, 0% to 3%, or 0% to 1%.
  • Organolithium salts may include lithium alkyl carbonates ROCO 2 Li and (ROCO 2 Li) 2 , lithium alkoxides ROLi, and the like.
  • organolithium salts may include CH3OCO2Li , CH3CH2OCO2Li , ( CH2OCO2Li ) 2 , Li ( CH2CH2OCO2 ) Li, CH3CH ( OCO2Li ) CH 2 OCO 2 Li, CH 2 (OCO 2 Li)CH 2 OCO 2 Li, CH 3 CH 2 OLi, etc.
  • the mass percentage of organic lithium salt in the artificial SEI film is low, and the stability of the artificial SEI film is higher, which can continuously protect the negative electrode active material, effectively reduce the gas production of the secondary battery, and improve the storage performance of the secondary battery.
  • the artificial solid electrolyte interfacial membrane consists of a first inorganic lithium salt and Li 2 O.
  • the first inorganic lithium salt is selected from Li 2 SO 3 .
  • the artificial SEI film can continuously protect the negative electrode active material while having a lower impedance, so that the secondary battery has lower gas production and lower impedance at the same time; in addition, the secondary battery can also have better cycle performance. performance and rate performance.
  • the artificial solid electrolyte interfacial membrane consists of Li 2 SO 3 and Li 2 O.
  • the mass percentage of Li2SO3 can be 20% ⁇ 90%, 25% ⁇ 90%, 30% ⁇ 90%, 35% ⁇ 90%, 40% ⁇ 90 %, 45% ⁇ 90%, 50% ⁇ 90%, 55%-90%, 60%-90%, 65%-90%, 70%-90%, 75%-90%, 80%-90%, or 85%-90%.
  • the mass percentage of Li2O is 10%-80%, 10%-75%, 10%-70%, 10%-65%, 10%-60%, 10%-55%, 10%-50% , 10% to 45%, 10% to 40%, 10% to 35%, 10% to 30%, 10% to 25%, 10% to 20%, or 10% to 15%.
  • the artificial solid electrolyte interfacial film has a thickness of 5 nm to 10 nm.
  • the artificial SEI film can continuously protect the negative electrode active material while having low impedance, so that the secondary battery has low gas production and low impedance at the same time.
  • the conventional solid electrolyte interfacial film has a thickness of 5 nm to 20 nm.
  • the thickness of the artificial solid electrolyte interface membrane and the thickness of the conventional solid electrolyte interface membrane can be measured by methods known in the art.
  • a section polisher such as the IB-09010CP type argon ion section polisher of Japan Electronics (JEOL) company
  • JEOL Japan Electronics
  • TEM Transmission Electron Microscope, transmission electron microscope
  • SEM Sccanning Electron Microscope, scanning electron microscope
  • the artificial solid electrolyte interfacial film is located on 80% to 100% of the surface of the negative electrode active material particles.
  • the artificial solid electrolyte interface film is located on 95%-100% of the surface of the negative electrode active material particles.
  • the artificial SEI film is located on almost the entire surface of the negative electrode active material particles, which can continuously protect the negative electrode active material, further reduce the gas production of the secondary battery and improve the storage performance of the secondary battery.
  • the mass percentage of the negative active material having an artificial solid electrolyte interface film on its surface is 80% to 100%.
  • the mass percentage of the negative electrode active material with the artificial solid electrolyte interfacial film on the surface is 95%-100%.
  • Almost all of the negative electrode active material in the negative electrode film layer has an artificial SEI film on the surface, which can further reduce the gas production of the secondary battery and improve the storage performance of the secondary battery.
  • the mass concentration deviations of C, O, S, and Li elements at any point in the artificial solid electrolyte interface film are all below 2%.
  • the respective mass concentrations of C, O, S, and Li elements at any point in the artificial solid electrolyte interface film are the mass concentrations of C, O, S, and Li elements that account for all elements in the extremely small volume of the point.
  • the elements contained in the very small volume micro-area of this point can be obtained by peak fitting with XPS peak software, and the relative content of each element is calculated through the peak area, which is recorded as the mass concentration of each element.
  • the mass concentration of a certain element at different positions of the artificial solid electrolyte interface film is respectively recorded as ⁇ 1 , ⁇ 2 , ⁇ 3 , ..., ⁇ n , n is a positive integer greater than or equal to 10, and the element The average mass concentration at different sites is recorded as ⁇ .
  • the mass concentration deviation ⁇ of C, O, S, and Li elements at any point in the artificial solid electrolyte interface film can be calculated according to the following formula (1):
  • the negative electrode film layer generally includes negative electrode active materials, optional binders, optional conductive agents and other optional additives.
  • 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 coating is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, optional auxiliary agent, etc. in a solvent and stirring them evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • NMP N-methylpyrrolidone
  • the type and content of the conductive agent and the binder are not specifically limited, and can be selected according to actual needs.
  • the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black, ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin (SR-1B), water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polypropylene One or more of amide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).
  • Other optional additives may include thickeners (such as sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.
  • the type of the negative electrode active material is not specifically limited, and negative electrode active materials known in the art for secondary batteries can be used.
  • the negative electrode active material may include one or more of graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fibers, carbon nanotubes, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.
  • the tin-based material may include one or more of simple 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 may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • a metal foil or a composite current collector can be used as the negative electrode current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is laminated on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the present application also provides a preparation method of the negative electrode sheet.
  • the preparation method of the negative electrode sheet at least includes the following steps S10, S20 and S30.
  • the initial negative electrode sheet includes a negative electrode collector and a negative electrode film layer disposed on at least one surface of the negative electrode collector and including a negative electrode active material.
  • the artificial solid electrolyte interface film includes a first inorganic lithium salt selected from one or both of Li 2 CO 3 and Li 2 SO 3 .
  • the moisture in the negative electrode film layer cannot be removed 100%, so there will be a small amount of H 2 O in the negative electrode film layer; at the same time, the mixed gas will inevitably contain a small amount of H 2 O.
  • the lithium metal can react with the mixed gas under the action of the trace amount of H 2 O to generate the first inorganic lithium salt. Due to the low moisture content, lithium metal reacts mildly with mixed gases.
  • the preparation method of the negative electrode sheet of the present application can make Li 2 CO 3 and Li 2 SO 3 evenly distributed in the artificial solid electrolyte interface film, and the respective masses of C, O, S, and Li elements at any point in the artificial solid electrolyte interface film The concentration deviations were all 2% or less.
  • the lithium metal has a mass of 0.1 mg/1540 mm 2 to 2 mg/1540 mm 2 .
  • the raw material and form of the lithium metal layer are not limited, and the raw material of the lithium metal layer can be selected from one or more of lithium powder, lithium ingot, lithium sheet, and lithium ribbon.
  • the lithium metal layer may also not be completely densely and evenly distributed on the surface of the initial negative electrode sheet.
  • the raw material of the lithium metal layer is lithium powder
  • there may be a certain gap between the lithium powder particles and the size of the gap can be controlled at 1 ⁇ m to 5000 ⁇ m
  • the raw material of the lithium metal layer is lithium ingot, lithium strip or lithium sheet, also A plurality of lithium sheets (or lithium strips) can be formed and arranged at intervals on the surface of the initial negative electrode sheet, and the distance between two adjacent lithium sheets (or lithium strips) can be controlled at 1 ⁇ m to 5000 ⁇ m.
  • a lithium metal layer may be provided on the surface of the negative electrode film layer by rolling.
  • the O 2 purity is ⁇ 99.995%
  • the CO 2 purity is ⁇ 99%
  • the SO 2 purity is ⁇ 99%.
  • the mass percentage of water in the mixed gas is ⁇ 0.2%.
  • the ratio of the volume of O 2 in the mixed gas to the total volume of CO 2 and SO 2 is 1:12 ⁇ 4:1.
  • the ratio of the volume of O 2 in the mixed gas to the total volume of CO 2 and SO 2 is 1:8 ⁇ 2:1.
  • the mixed gas includes O 2 and CO 2 , and the volume ratio of O 2 to CO 2 is 1:12 ⁇ 4:1.
  • the volume ratio of O 2 to CO 2 is 1:8 ⁇ 2:1.
  • the mixed gas includes O 2 and SO 2 , and the volume ratio of O 2 to SO 2 is 1:12 ⁇ 4:1.
  • the volume ratio of O 2 to SO 2 is 1:8 ⁇ 2:1.
  • the mixed gas includes O 2 , CO 2 and SO 2 , and the ratio of the volume of O 2 to the total volume of CO 2 and SO 2 is 1:12 ⁇ 4:1.
  • the ratio of the volume of O 2 to the total volume of CO 2 and SO 2 is 1:8 ⁇ 2:1.
  • the reaction time is 1 h-72 h.
  • the reaction time is 2h-48h.
  • the ratio of the volume of O2 in the mixed gas to the total volume of CO2 and SO2 , the reaction time, etc. can be adjusted reasonably according to the desired composition and thickness of the artificial SEI film.
  • the method for reacting the lithium metal in the lithium-supplementing negative electrode sheet with a mixed gas containing O 2 and one or both of CO 2 and SO 2 includes: placing the lithium-supplementing negative electrode sheet in a non- In the water organic solvent, the mixed gas containing O 2 and one or both of CO 2 and SO 2 is continuously passed into the non-aqueous organic solvent, so that the lithium metal and the mixed gas react, so that at least part of the negative electrode active material An artificial solid electrolyte interfacial film is formed on the surface.
  • the organic solvent is selected from one or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the method for reacting the lithium metal in the lithium-replenishing negative electrode sheet with a mixed gas containing O 2 and one or both of CO 2 and SO 2 includes: directly placing the lithium-replenishing negative electrode sheet In a mixed gas containing O 2 and one or both of CO 2 and SO 2 , the lithium metal is reacted with the mixed gas to form an artificial solid electrolyte interfacial film on at least part of the surface of the negative electrode active material.
  • the embodiment of the present application also provides a secondary battery, which includes the negative electrode sheet of the present application or the negative electrode sheet prepared by the method of the present application.
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active materials and continue to be used after the battery is discharged.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions such as lithium ions, etc.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the electrolyte is between the positive pole piece and the negative pole piece, and mainly plays the role of conducting active ions.
  • the positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including positive electrode active materials.
  • the positive electrode current collector has two opposite surfaces 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 positive electrode film layer generally includes a positive electrode active material, optionally a binder, and optionally a conductive agent.
  • 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, an optional conductive agent, an optional binder and any other components in a solvent and stirring them uniformly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder used for the positive film layer may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoro One or more of propylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • the conductive agent used in the positive film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used for the positive electrode current collector.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the positive electrode film layer includes a positive electrode active material, and the positive electrode active material can be a positive electrode active material known in the art for secondary batteries.
  • the secondary battery of the present application may be a lithium ion battery or a sodium ion battery.
  • the positive electrode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds .
  • lithium transition metal oxides may include, but are not limited to, 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 One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, lithium manganese iron phosphate
  • One or more of the composite materials with carbon and their respective modified compounds is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials of lithium ion batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • the positive electrode active material of lithium ion battery can be selected from LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 One of O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O 2 , LiFePO 4 (LFP) and LiMnPO 4 species or several.
  • LiCoO 2 LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 One of O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O
  • the positive electrode active material can be selected from transition metal oxides Na x MO 2 (M is a transition metal, optionally selected from Mn, Fe, Ni, Co , one or more of V, Cu, Cr, 0 ⁇ x ⁇ 1), polyanion materials (such as phosphate, fluorophosphate, pyrophosphate, sulfate, etc.), Prussian blue materials, etc., but this application It is not limited to these materials, and other materials that can be used as a positive electrode active material of a sodium ion battery can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • the positive electrode active material of the sodium ion battery may be selected from NaFeO 2 , NaCoO 2 , NaCrO 2 , NaMnO 2 , NaNiO 2 , NaNi 1/2 Ti 1/2 O 2 , NaNi 1/2 Mn 1/2 O 2 , Na 2/3 Fe 1/3 Mn 2/3 O 2 , NaNi 1/3 Co 1/3 Mn 1/3 O 2 , NaFePO 4 , NaMnPO 4 , NaCoPO 4 , Prussian blue material, and the general formula is A a One or more of the materials of M b (PO 4 ) c O x Y 3-x .
  • A is selected from one or more of H + , Li + , Na + , K + and NH 4 + ;
  • M is a transition metal Cation, can be selected from one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn;
  • Y is a halogen anion, can be selected from one or more of F, Cl and Br ; 0 ⁇ a ⁇ 4, 0 ⁇ b ⁇ 2, 1 ⁇ c ⁇ 3, 0 ⁇ x ⁇ 2.
  • the modified compounds of the above-mentioned positive electrode active materials may be doping modification, surface coating modification, or doping and surface coating modification on the positive electrode active material.
  • the electrolyte plays the role of conducting active ions between the positive pole piece and the negative pole piece.
  • the electrolyte of the present application adopts electrolytic solution.
  • the electrolytic solution includes electrolyte salts and solvents.
  • the type of electrolyte salt is not specifically limited, and can be selected according to actual needs.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), dioxalic acid
  • LiBOB lithium difluorophosphate
  • LiDFOP lithium difluorooxalatephosphate
  • LiTFOP lithium tetrafluorooxalatephosphate
  • the electrolyte salt can be selected from one of NaPF 6 , NaClO 4 , NaBCl 4 , NaSO 3 CF 3 and Na(CH 3 )C 6 H 4 SO 3 or several.
  • the type of solvent is not specifically limited, and can be selected according to actual needs.
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA) , ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate One or more of ester (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl sulfone (GB
  • the solvent is a non-aqueous solvent.
  • additives are optionally included in the electrolyte.
  • additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance. Additives etc.
  • the additives may include cyclic carbonate compounds containing unsaturated bonds, halogen-substituted cyclic carbonate compounds, sulfate ester compounds, sulfite compounds, sultone compounds, disulfonic acid compounds , one or more of nitrile compounds, aromatic compounds, isocyanate compounds, phosphazene compounds, cyclic anhydride compounds, phosphite compounds, phosphate compounds, borate compounds, and carboxylate compounds.
  • the second additive may include one or both of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS) and the like.
  • FIG. 1 shows a secondary battery 5 with a square structure 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, the bottom plate and the side plates enclose to form a receiving cavity.
  • the housing 51 has an opening communicating with the receiving chamber, and the cover plate 53 is used to cover the opening to close the receiving chamber.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to requirements.
  • the secondary battery can be assembled into a battery module, and 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 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 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • 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 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 is used to cover the lower box body 3 and forms a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • Embodiments of the present application further provide an electric device, the electric device includes at least one of the secondary battery, the battery module, and the battery pack of the present application.
  • the secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, 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 electric device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 6 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • the positive electrode active material lithium iron phosphate, the conductive agent acetylene black, and the binder polyvinylidene fluoride at a mass ratio of 97.2:1.3:1.5, add the solvent N-methylpyrrolidone, and fully stir and mix to form a uniform positive electrode slurry;
  • the positive electrode slurry is evenly coated on the aluminum foil of the positive electrode current collector, and then dried and cold pressed to obtain the positive electrode sheet.
  • Polyethylene porous membrane is used as the isolation membrane.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation step of the negative electrode sheet are adjusted, see Table 1 for details.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the negative electrode sheet is prepared according to the following method.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the negative electrode sheet is prepared according to the following method.
  • the Escalab 250Xi X-ray photoelectron spectrometer of Thermo Fisher Scientific Corporation of the United States is used for testing.
  • the analysis area of the negative electrode diaphragm is 700 ⁇ m ⁇ 300 ⁇ m
  • the spectra of C, O, S, and Li elements were collected at a distance of ⁇ 5nm from the surface of the negative electrode film layer and processed by XPS peak software, and quantitatively analyzed Li 2 CO 3 , Li 2 SO 3 in the artificial SEI film through the content of each element mass percent content.
  • multiple (for example, 10) spectra at different positions can be taken for quantitative analysis, and the average value can be taken as the test result.
  • Table 1 gives the parameters of Examples 1-24 and Comparative Examples 1-2.
  • Table 2 shows the test results of Examples 1-24 and Comparative Examples 1-2.
  • Example 10 2mg/1540mm 2 O 2 :CO
  • the negative pole sheet of comparative example 1 has not been through any treatment, and the film-forming resistance of the conventional SEI film on the surface of the negative electrode active material is higher, so the DCR of the secondary battery is higher; in addition, the structure of the conventional SEI film is also unstable, and the secondary battery is low. It is easy to decompose during voltage storage, so the volume expansion rate of the secondary battery is also high.
  • the lithium metal in Comparative Example 2 was not treated with a mixed gas. After the liquid injection, the lithium metal reacted with the negative electrode and embedded in the negative electrode active material particles. The thickness of the conventional SEI film formed on the surface of the negative electrode active material was reduced, which can reduce the secondary battery to a certain extent. The DCR. However, the thickness of the conventional SEI film is reduced, which cannot effectively protect the negative electrode active material, and the organic solvent in the electrolyte is likely to undergo a reduction reaction on the surface of the negative electrode active material and produce a large amount of gas products. Therefore, the volume expansion rate of the secondary battery increases.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请公开了一种负极极片及其制备方法、二次电池、电池模块、电池包、用电装置。所述负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜层，至少部分负极活性材料表面具有人造固体电解质界面膜，所述人造固体电解质界面膜包括第一无机锂盐，所述第一无机锂盐选自Li 2CO 3、Li 2SO 3中的一种或两种。本申请的负极极片能有效降低二次电池产气、提高二次电池的存储性能。

Description

负极极片及其制备方法、二次电池、电池模块、电池包、用电装置
相关申请的交叉引用
本申请要求享有于2021年09月18日提交的名称为“负极极片及其制备方法、二次电池、电池模块、电池包、用电装置”的中国专利申请202111104915.3的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请属于电池技术领域，尤其涉及一种负极极片及其制备方法、二次电池、电池模块、电池包、用电装置。
背景技术
二次电池依靠活性离子在正极和负极之间往复脱嵌来进行充电和放电，其具有能量密度高、循环寿命长，以及无污染、无记忆效应等突出特点。因此，二次电池作为清洁能源，已由电子产品逐渐普及到电动汽车等大型装置领域，以适应环境和能源的可持续发展战略。但是二次电池也有其缺点，例如长时间存储时，容量降低、产气增加，甚至影响用户的生命安全。
发明内容
本申请的目的在于提供一种负极极片及其制备方法、二次电池、电池模块、电池包、用电装置，旨在有效降低二次电池产气、提高二次电池的存储性能。
为了实现上述发明目的，本申请第一方面提供一种负极极片。所述负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜层，至少部分负极活性材料表面具有人造固体电解质界面膜，所述人造固体电解质界面膜包括第一无机锂盐，所述第一无机锂盐选自Li 2CO 3、Li 2SO 3中的一种或两种。
人造SEI膜具有良好的物理及化学稳定性，是一种具有电子绝缘性和良好的离子导通性的固体电解质膜。二次电池在长时间低电压存储、过度放电时，由于人造SEI膜具有电子绝缘性，因此能抑制常规SEI膜的还原分解，降低二次电池产气。人造SEI膜还能抑制电解液中的电解质盐、有机溶剂、添加剂以及杂质(例如微量H 2O和溶解O 2等)在负极活性材料表面得到电子并发生还原反应，进一步降低二次电池产气。因此，本申请的负极极片能有效降低二次电池产气、提高二次电池的存储性能。
在本申请任意实施方式中，基于人造固体电解质界面膜的总质量计，第一无机锂盐的质量百分含量为20％～90％。可选地，第一无机锂盐的质量百分含量为80％～90％。第一无机锂盐的质量百分含量在合适的范围内，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池同时具有较低的产气和较低的阻抗。
在本申请任意实施方式中，所述人造固体电解质界面膜还包括Li 2O。Li 2O能够提高人造SEI膜的稳定性，从而人造SEI膜能持续保护负极活性材料，降低二次电池产气，提高二次电池的存储性能。
在本申请任意实施方式中，基于人造固体电解质界面膜的总质量计，Li 2O的质量百分含量为10％～80％。可选地，Li 2O的质量百分含量为10％～20％。Li 2O的质量百分含量在合适的范围内，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池同时具有较低的产气和较低的阻抗。
在本申请任意实施方式中，人造固体电解质界面膜由第一无机锂盐以及Li 2O组成。
在本申请任意实施方式中，人造固体电解质界面膜的厚度为5nm～10nm。人造固体电解质界面膜的厚度在合适的范围内，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池同时具有较低的产气和较低的阻抗。
在本申请任意实施方式中，人造固体电解质界面膜中任意一点的C、O、S、Li元素各自的质量浓度偏差均为2％以下。
在本申请任意实施方式中，人造固体电解质界面膜位于所述负极活性材料颗粒的80％～100％的表面。可选地，人造固体电解质界面膜位于所述负极活性材料颗粒的95％～100％的表面。人造SEI膜位于负极活性材料颗粒几乎全部表面，能持续保护负极活性材料，进一步降低二次电池产气并提高二次电池的存储性能。
在本申请任意实施方式中，基于负极膜层中负极活性材料的总质量计，表面具有人造固体电解质界面膜的负极活性材料的质量百分含量为80％～100％。可选地，表面具有人造固体电解质界面膜的负极活性材料的质量百分含量为95％～100％。负极膜层中几乎全部的负极活性材料表面均具有人造SEI膜，能进一步降低二次电池产气并提高二次电池的存储性能。
在本申请任意实施方式中，负极极片应用于二次电池，化成结束后，至少部分负极活性材料表面具有人造固体电解质界面膜以及位于人造固体电解质界面膜表面的常规固体电解质界面膜。
本申请第二方面提供一种负极极片的制备方法，包括如下步骤：S10，提供初始负极极片，初始负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜层；S20，将锂金属层设置在负极膜层上，得到补锂负极极片；S30，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜，所述人造固体电解质界面膜包括第一无机锂盐，所述第一无机锂盐选自Li 2CO 3、Li 2SO 3中的一种或两种。
在本申请任意实施方式中，在S20中，锂金属的质量为0.1mg/1540mm 2～2mg/1540mm 2。
在本申请任意实施方式中，在S30中，混合气体中O 2的体积与CO 2和SO 2的总体积之比为1:12～4:1。可选地，混合气体中O 2的体积与CO 2和SO 2的总体积之比为1:8～2:1。
在本申请任意实施方式中，在S30中，反应时间为1h～72h。可选地，反应时间为2h～48h。
在本申请任意实施方式中，在S30中，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应的方法包括：将补锂负极极片置于非水有机溶剂中，向非水有机溶剂中持续通入包含O 2以及CO 2、SO 2中的一种或两种的混合气体，使锂金属与混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜。可选地，非水有机溶剂选自碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯中的一种或几种。
在本申请任意实施方式中，在S30中，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应的方法包括：将补锂负极极片直接置于包含O 2以及CO 2、SO 2中的一种或两种的混合气体中，使锂金属与混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜。
本申请第三方面提供一种二次电池，其包括本申请第一方面的负极极片或根据本申请第二方面所述的方法制备的负极极片。
本申请第四方面提供一种电池模块，其包括本申请第三方面的二次电池。
本申请第五方面提供一种电池包，其包括本申请第三方面的二次电池、第四方面的电池模块中的一种。
本申请第六方面提供一种用电装置，其包括本申请第三方面的二次电池、第四方面的电池模块、第五方面的电池包中的至少一种。
本申请的二次电池具有较低的产气，进而本申请的二次电池能具有显著改善的存储性能。本申请的二次电池还可具有较低的阻抗，以及改善的循环性能和倍率性能。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是本申请的二次电池的一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的分解图。
图6是本申请的二次电池用作电源的用电装置的一实施方式的示意图。
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负极极片及其制备方法、二次电池、电池模块、电池包、用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。 这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，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)。
负极极片
二次电池首次充电过程中，电解液中的电解质盐、有机溶剂、添加剂以及杂质(例如微量H 2O和溶解O 2等)会在负极活性材料与电解液的固液相界面上发生还原反应，还原反应的产物包括气体产物、液体产物以及固体产物。气体产物包括C 2H 4等烃类气体以及CO 2、H 2等无机气体；液体产物生成后会溶解在电解液中；固体产物生成后会覆盖于负极活性材料表面形成一层钝化膜，即固体电解质界面膜(Solid Electrolyte Interface，简称SEI膜)。这种SEI膜主要包括各种无机成分(例如Li 2CO 3、LiF、Li 2O、LiOH等)和各种有机成分(例如烷基碳酸锂ROCO 2Li和(ROCO 2Li) 2、烷氧基锂ROLi等，具体可包 括CH 3OCO 2Li、CH 3CH 2OCO 2Li、(CH 2OCO 2Li) 2、Li(CH 2CH 2OCO 2)Li、CH 3CH(OCO 2Li)CH 2OCO 2Li、CH 2(OCO 2Li)CH 2OCO 2Li、CH 3CH 2OLi等)。这种SEI膜是一种具有电子绝缘性和良好的离子导通性的固体电解质膜，能阻止溶剂在负极活性材料表面的还原反应，尤其是避免因溶剂分子共嵌入对负极活性材料造成的破坏。
但是，二次电池在长时间低电压存储、过度放电时，负极电位不断升高、SEI膜容易分解；二次电池在高温环境存储时，SEI膜不稳定也会分解。SEI分解会产生气体导致二次电池体积膨胀；此外，负极活性材料表面的SEI膜分解后，暴露的负极活性材料表面会继续与电解液中的电解质盐、有机溶剂、添加剂以及杂质(例如微量H 2O和溶解O 2等)反应，这一过程称为SEI的修复。SEI修复过程中消耗了大量活性离子导致二次电池容量降低，同时SEI修复过程中还会产生大量气体产物，进一步加剧二次电池体积膨胀，甚至影响用户的生命安全。
为了解决上述问题，发明人经过大量研究提出了一种新型的负极极片，所述负极极片能有效降低二次电池产气，提高二次电池的存储性能。所述负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜层，至少部分负极活性材料表面具有人造固体电解质界面膜(简称为人造SEI膜)，所述人造固体电解质界面膜包括第一无机锂盐，所述第一无机锂盐选自Li 2CO 3、Li 2SO 3中的一种或两种。
本申请的负极极片应用于二次电池中后，在首次充电过程(对应化成过程)中，电解液中的电解质盐、有机溶剂、添加剂以及杂质(例如微量H 2O和溶解O 2等)会在人造固体电解质膜与电解液的固液相界面上继续发生还原反应，形成常规固体电解质界面膜(简称为常规SEI膜)。常规固体电解质界面膜主要包括各种无机成分(例如Li 2CO 3、LiF、Li 2O、LiOH等)和各种有机成分(例如烷基碳酸锂ROCO 2Li和(ROCO 2Li) 2、烷氧基锂ROLi等，具体可包括CH 3OCO 2Li、CH 3CH 2OCO 2Li、(CH 2OCO 2Li) 2、Li(CH 2CH 2OCO 2)Li、CH 3CH(OCO 2Li)CH 2OCO 2Li、CH 2(OCO 2Li)CH 2OCO 2Li、CH 3CH 2OLi等)。因此，至少部分负极活性材料表面同时具有人造固体电解质界面膜以及位于人造固体电解质界面膜表面的常规固体电解质界面膜。
本申请的负极极片中，负极活性材料表面的“人造固体电解质界面膜”与二次电池化成过程中在负极活性材料表面形成的“常规固体电解质界面膜”不同，且本申请的“人造固体电解质界面膜”是在二次电池首次充电前(对应化成前)形成。本申请的负极极片应用于二次电池，化成结束后，会在人造固体电解质膜表面继续形成一层常规固体电解质界面膜，进而至少部分负极活性材料表面同时具有人造固体电解质界面膜以及位于人造固体电解质界面膜表面的常规固体电解质界面膜。因此，本申请的负极极片应用于二次电池中后，至少部分负极活性材料表面具有双层SEI膜。
本申请的人造SEI膜具有良好的物理及化学稳定性，是一种具有电子绝缘性和良好的离子导通性的固体电解质膜。二次电池在长时间低电压存储、过度放电时，负极电位不断升高，常规SEI膜容易分解，由于人造SEI膜具有电子绝缘性，因此能抑制常规SEI膜的还原分解，降低二次电池产气。
二次电池在长时间低电压存储、高温存储、过度放电时，常规SEI膜会分解并进入修复程序，由于人造SEI膜具有电子绝缘性，因此能抑制电解液中的电解质盐、有机 溶剂、添加剂以及杂质(例如微量H 2O和溶解O 2等)在负极活性材料表面得到电子并发生还原反应，从而进一步降低二次电池产气。
此外，人造SEI膜的存在还能降低常规SEI膜修复时对活性离子的消耗，避免因溶剂分子共嵌入对负极活性材料造成的破坏，因此还能提高二次电池的循环性能。
在一些实施方式中，基于人造固体电解质界面膜的总质量计，第一无机锂盐的质量百分含量为20％～90％。例如，第一无机锂盐的质量百分含量为20％～90％，25％～90％，30％～90％，35％～90％，40％～90％，45％～90％，50％～90％，55％～90％，60％～90％，65％～90％，70％～90％，75％～90％，80％～90％，或85％～90％。第一无机锂盐的质量百分含量在合适的范围内，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池同时具有较低的产气和较低的阻抗。
在一些实施方式中，所述人造固体电解质界面膜还包括Li 2O。Li 2O能提高人造SEI膜的稳定性，从而人造SEI膜能持续保护负极活性材料，降低二次电池产气、提高二次电池的存储性能。
在一些实施方式中，基于人造固体电解质界面膜的总质量计，Li 2O的质量百分含量为10％～80％。例如，Li 2O的质量百分含量为10％～80％，10％～75％，10％～70％，10％～65％，10％～60％，10％～55％，10％～50％，10％～45％，10％～40％，10％～35％，
10％～30％，10％～25％，10％～20％，或10％～15％。Li 2O的质量百分含量在合适的范围内，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池同时具有较低的产气和较低的阻抗。
在一些实施方式中，所述人造固体电解质界面膜还可包括少量有机锂盐，且基于人造固体电解质界面膜的总质量计，有机锂盐的质量百分含量在40％以下。例如，有机锂盐的质量百分含量为0％～40％，0％～35％，0％～30％，0％～25％，0％～20％，0％～15％，0％～10％，0％～5％，0％～3％，或0％～1％。有机锂盐可以包括烷基碳酸锂ROCO 2Li和(ROCO 2Li) 2、烷氧基锂ROLi等。例如，有机锂盐可包括CH 3OCO 2Li、CH 3CH 2OCO 2Li、(CH 2OCO 2Li) 2、Li(CH 2CH 2OCO 2)Li、CH 3CH(OCO 2Li)CH 2OCO 2Li、CH 2(OCO 2Li)CH 2OCO 2Li、CH 3CH 2OLi等。人造SEI膜中有机锂盐的质量百分含量较低，人造SEI膜的稳定性更高，能持续保护负极活性材料，有效降低二次电池产气、提高二次电池的存储性能。
在一些实施方式中，所述人造固体电解质界面膜由第一无机锂盐以及Li 2O组成。
在一些实施方式中，所述第一无机锂盐选自Li 2SO 3。此时，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池同时具有较低的产气和较低的阻抗；此外，二次电池还能具有更好的循环性能和倍率性能。
在一些实施方式中，所述人造固体电解质界面膜由Li 2SO 3以及Li 2O组成。Li 2SO 3的质量百分含量可为20％～90％，25％～90％，30％～90％，35％～90％，40％～90％，45％～90％，50％～90％，55％～90％，60％～90％，65％～90％，70％～90％，75％～90％，80％～90％，或85％～90％。Li 2O的质量百分含量为10％～80％，10％～75％，10％～70％，10％～65％，10％～60％，10％～55％，10％～50％，10％～45％，10％～40％，10％～35％，10％～30％，10％～25％，10％～20％，或10％～15％。
在一些实施方式中，所述人造固体电解质界面膜的厚度为5nm～10nm。人造固体电解质界面膜的厚度在合适的范围内，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池同时具有较低的产气和较低的阻抗。
在一些实施方式中，所述常规固体电解质界面膜的厚度为5nm～20nm。
人造固体电解质界面膜的厚度和常规固体电解质界面膜的厚度可以采用本领域公知的方法进行测定。作为示例，可以采用截面抛光仪(如日本电子(JEOL)公司的IB-09010CP型氩离子截面抛光仪)制备负极活性材料颗粒的截面，该截面经过负极活性材料颗粒的核心；然后由EDX(Energy Dispersive X-Ray Spectroscopy，能量色散X射线光谱仪)或EDS元素分析结合TEM(Transmission Electron Microscope，透射电子显微镜)或SEM(Scanning Electron Microscope，扫描电子显微镜)扫描测试得到截面中的元素分布图；根据截面的元素分布得到人造固体电解质界面膜的厚度和常规固体电解质界面膜的厚度。更精确地，可以测试截面上多个(3个以上，如5个、8个、10个、12个等)不同位置处的厚度，取平均值作为测试结果。
在一些实施方式中，所述人造固体电解质界面膜位于所述负极活性材料颗粒的80％～100％的表面。可选地，所述人造固体电解质界面膜位于所述负极活性材料颗粒的95％～100％的表面。人造SEI膜位于负极活性材料颗粒几乎全部表面，能持续保护负极活性材料，进一步降低二次电池产气并提高二次电池的存储性能。
在一些实施方式中，基于负极膜层中负极活性材料的总质量计，表面具有人造固体电解质界面膜的负极活性材料的质量百分含量为80％～100％。可选地，表面具有人造固体电解质界面膜的负极活性材料的质量百分含量为95％～100％。负极膜层中几乎全部的负极活性材料表面均具有人造SEI膜，能进一步降低二次电池产气并提高二次电池的存储性能。
在一些实施方式中，所述人造固体电解质界面膜中任意一点的C、O、S、Li元素各自的质量浓度偏差均为2％以下。
在本申请中，人造固体电解质界面膜中任意一点的C、O、S、Li元素各自的质量浓度为在该一点极小体积内，C、O、S、Li元素分别占所有元素的质量浓度，可由XPS(X-ray photoelectron spectroscopy)测得。通过XPS peak软件分峰拟合可以得到该一点极小体积微区内所含有的元素，并通过峰面积计算各元素的相对含量，以此记为各元素的质量浓度。以XPS元素分析时，人造固体电解质界面膜不同位点处某一元素的质量浓度分别记作η 1、 η 2 、η 3、…、η n，n为大于或等于10的正整数，该元素在不同位点处的平均质量浓度记作η。
人造固体电解质界面膜中任意一点的C、O、S、Li元素各自的质量浓度偏差σ均可根据下式(1)计算得到：
Figure PCTCN2022096212-appb-000001
在本申请的负极极片中，负极膜层通常包含负极活性材料以及可选的粘结剂、可选的导电剂和其它可选助剂。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。负极浆料涂通常是将负极活性材料以及可选的导电剂、可选的粘结剂、可选助剂等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。导电剂以及粘结剂的种类和含量不受具体的限制，可根据实际需求进行选择。作为示例，导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑等)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。作为示例，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)及羧甲基壳聚糖(CMCS)中的一种或几种。其他可选的助剂可包括增稠剂(例如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
在一些实施方式中，负极活性材料的种类并不受到具体的限制，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，负极活性材料可包括石墨、软碳、硬碳、中间相碳微球、碳纤维、碳纳米管、硅基材料、锡基材料、钛酸锂中的一种或几种。硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或几种。锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或几种。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。
在一些实施方式中，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、银合金中的一种或几种。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。负极集流体具有在自身厚度方向相对的两个表面，负极膜层层合于负极集流体相对的两个表面的其中任意一者或两者上。
制备方法
本申请还提供了负极极片的制备方法。负极极片的制备方法至少包括下述S10、S20、S30。
S10，提供初始负极极片，初始负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜层。
S20，将锂金属层设置在负极膜层上，得到补锂负极极片。
S30，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜，所述人造固体电解质界面膜包括第一无机锂盐，所述第一无机锂盐选自Li 2CO 3、Li 2SO 3中的一种或两种。
在初始负极极片的制备工艺中，负极膜层中的水分不能100％除去，因此负极膜层中会存在微量H 2O；同时，混合气体中不可避免地也含有微量H 2O。锂金属在这部分微量H 2O作用下能与混合气体反应，生成第一无机锂盐。由于水分含量较低，锂金属与混合气体的反应比较温和。
本申请的负极极片的制备方法可以使Li 2CO 3、Li 2SO 3均匀分布在人造固体电解质界面膜中，人造固体电解质界面膜中任意一点的C、O、S、Li元素各自的质量浓度偏差均为2％以下。
在一些实施方式中，在S20中，锂金属的质量为0.1mg/1540mm 2～2mg/1540mm 2。
在一些实施方式中，在S20中，锂金属层的原料及形式不受限制，锂金属层的原料可选自锂粉、锂锭、锂片、锂带中的一种或几种。锂金属层也可以不完全密集均匀分布在初始负极极片的表面。例如当锂金属层的原料是锂粉时，锂粉颗粒之间可以存在一定的间隙，间隙大小可控制在1μm～5000μm；当锂金属层的原料是锂锭、锂带或锂片时，也可以形成多个锂片(或锂带)彼此间隔设置在初始负极极片的表面，相邻两个锂片(或锂带)之间的间距可控制在1μm～5000μm。
在一些实施方式中，在S20中，可采用压延的方式在负极膜层表面设置锂金属层。
在一些实施方式中，在S30中，O 2纯度≥99.995％，CO 2纯度≥99％，SO 2纯度≥99％。
在一些实施方式中，在S30中，混合气体中水分的质量百分含量≤0.2％。
在一些实施方式中，在S30中，混合气体中O 2的体积与CO 2和SO 2的总体积之比为1:12～4:1。可选地，混合气体中O 2的体积与CO 2和SO 2的总体积之比为1:8～2:1。
在一些实施方式中，混合气体包括O 2和CO 2，O 2的体积与CO 2的体积之比为1:12～4:1。可选地，O 2的体积与CO 2的体积之比为1:8～2:1。
在一些实施方式中，混合气体包括O 2和SO 2，O 2的体积与SO 2的体积之比为1:12～4:1。可选地，O 2的体积与SO 2的体积之比为1:8～2:1。
在一些实施方式中，混合气体包括O 2、CO 2和SO 2，O 2的体积与CO 2和SO 2的总体积之比为1:12～4:1。可选地，O 2的体积与CO 2和SO 2的总体积之比为1:8～2:1。
在一些实施方式中，在S30中，反应时间为1h～72h。可选地，反应时间为2h～48h。
混合气体中O 2的体积与CO 2和SO 2的总体积之比、反应时间等可以根据所需的人造SEI膜组成及厚度进行合理调节。
在一些实施方式中，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应的方法包括：将补锂负极极片置于非水有机溶剂中，向非水有机溶剂中持续通入包含O 2以及CO 2、SO 2中的一种或两种的混合气体，使锂金属与混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜。可选地，有机溶剂选自碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯中的一种或几种。
在另一些实施方式中，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应的方法包括：将补锂负极极片直接置于包含O 2以及CO 2、SO 2中的一种或两种的混合气体中，使锂金属与混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜。
二次电池
本申请的实施方式还提供一种二次电池，所述二次电池包括本申请的负极极片或通过本申请的方法制备的负极极片。
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解质。在电池充放电过程中，活性离子(例如锂离子等)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解质在正极极片和负极极片之间，主要起到传导活性离子的作用。
[正极极片]
正极极片通常包括正极集流体以及设置于正极集流体至少一个表面上且包括正极活性材料的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置在正极集流体的两个相对表面中的任意一者或两者上。
本申请的正极极片中，正极膜层通常包含正极活性材料以及可选地粘结剂和可选地导电剂。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。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。作为示例，用于正极膜层的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、含氟丙烯酸酯树脂中的一种或几种。作为示例，用于正极膜层的导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或几种。
在本申请的正极极片中，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，正极集流体可采用铝箔。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、银合金中的一种或几种。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。
在本申请的正极极片中，正极膜层包括正极活性材料，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。
需要说明的是，本申请的二次电池可以为锂离子电池、钠离子电池。
当本申请的二次电池为锂离子电池时，可选地，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一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、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改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、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一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作锂离子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。
例如，锂离子电池的正极活性材料可选自LiCoO 2、LiNiO 2、LiMnO 2、LiMn 2O 4、LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、LiNi 0.85Co 0.15Al 0.05O 2、LiFePO 4(LFP)及LiMnPO 4中的一种或几种。
当本申请的二次电池为钠离子电池时，可选地，所述正极活性材料可以选自过渡金属氧化物Na xMO 2(M为过渡金属，可选选自Mn、Fe、Ni、Co、V、Cu、Cr中的一种或几种，0＜x≤1)、聚阴离子材料(如磷酸盐、氟磷酸盐、焦磷酸盐、硫酸盐等)、普鲁士蓝材料等，但本申请并不限定于这些材料，还可以使用其他可被用作钠离子电池正极活性材料的材料。这些正极活性材料可以仅单独使用一种，也可以两种以上组合使用。
可选地，钠离子电池的正极活性材料可选自NaFeO 2、NaCoO 2、NaCrO 2、NaMnO 2、NaNiO 2、NaNi 1/2Ti 1/2O 2、NaNi 1/2Mn 1/2O 2、Na 2/3Fe 1/3Mn 2/3O 2、NaNi 1/3Co 1/3Mn 1/3O 2、NaFePO 4、NaMnPO 4、NaCoPO 4、普鲁士蓝材料、及通式为A aM b(PO 4) cO xY 3-x的材料中的一种或几种。在通式A aM b(PO 4) cO xY 3-x中，A选自H +、Li +、Na +、K +及NH 4 +中的一种或几种；M为过渡金属阳离子，可选选自V、Ti、Mn、Fe、Co、Ni、Cu及Zn中的一种或几种；Y为卤素阴离子，可选选自F、Cl及Br中的一种或几种；0＜a≤4，0＜b≤2，1≤c≤3，0≤x≤2。
在一些实施方式中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
[电解质]
电解质在正极极片和负极极片之间起到传导活性离子的作用。本申请的电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐的种类不受具体的限制，可根据实际需求进行选择。
当本申请的二次电池为锂离子电池时，作为示例，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、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)中的一种或几种。
当本申请的二次电池为钠离子电池时，作为示例，电解质盐可以选自NaPF 6、NaClO 4、NaBCl 4、NaSO 3CF 3及Na(CH 3)C 6H 4SO 3中的一种或几种。
在一些实施方式中，溶剂的种类不受具体的限制，可根据实际需求进行选择。作为示例，溶剂可选自碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、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)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、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)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，可选地，溶剂为非水溶剂。
在一些实施方式中，电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
在一些实施方式中，所述添加剂可包括含有不饱和键的环状碳酸酯化合物、卤素取代的环状碳酸酯化合物、硫酸酯化合物、亚硫酸酯化合物、磺酸内酯化合物、二磺酸化合物、腈化合物、芳香化合物、异氰酸酯化合物、磷腈化合物、环状酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、硼酸酯化合物、羧酸酯化合物中的一种或几种。可选地，所述第二添加剂可包括碳酸亚乙烯酯(VC)、氟代碳酸乙烯酯(FEC)中的一种或两种。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料可相同或不同。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，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)等中的一种或几种。
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。
在一些实施方式中，参照图2，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。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几个，可根据需求来调节。
在一些实施方式中，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。参照图3，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。
在一些实施方式中，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。参照图4和图5，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
本申请的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、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。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、和比值都是基于重量计，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
负极极片的制备
将负极活性材料石墨、导电剂乙炔黑、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按质量比95:2:2:1进行混合，加入溶剂去离子水，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上，然后经烘干、冷压，得到初始负极极片。
采用压延技术将1mg/1540mm 2锂金属片覆盖在初始负极极片上，之后在O 2(纯度≥99.995％)、CO 2(纯度≥99％)体积比为1:12的混合气体中静置12h，使锂金属与混合气体反应，得到负极极片。
正极极片的制备
将正极活性材料磷酸铁锂、导电剂乙炔黑、粘结剂聚偏氟乙烯按质量比97.2:1.3:1.5进行混合，加入溶剂N-甲基吡咯烷酮，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上，然后经烘干、冷压，得到正极极片。
电解液的制备
在含水量<10ppm的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)按质量30:70进行混合，得到有机溶剂；将充分干燥的锂盐LiPF 6和添加剂碳酸亚乙烯酯(VC)溶解于上述有机溶剂中，搅拌均匀后，获得电解液。LiPF 6的浓度为1mol/L，VC质量百分含量为1％。
隔离膜的制备
采用聚乙烯多孔膜作为隔离膜。
二次电池的制备
将上述制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极极片之间起到隔离的作用，然后卷绕得到电极组件，将电极组件置于外包装中；将上述制备好的电解液注入到干燥后的电极组件中，然后经过真空封装、静置、化成、整形等工序，得到二次电池。
实施例2～24
二次电池的制备方法与实施例1类似，不同的是：调节了负极极片制备步骤中的相关参数，具体详见表1。
对比例1
二次电池的制备方法与实施例1类似，不同的是负极极片按照如下方法制备。
将负极活性材料石墨、导电剂乙炔黑、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按质量比95:2:2:1进行混合，加入溶剂去离子水，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上，然后经烘干、冷压，得到负极极片。
对比例2
二次电池的制备方法与实施例1类似，不同的是负极极片按照如下方法制备。
将负极活性材料石墨、导电剂乙炔黑、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按质量比95:2:2:1进行混合，加入溶剂去离子水，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上，然后经烘干、冷压，得到初始负极极片。采用压延技术将1mg/1540mm 2锂金属片覆盖在初始负极极片上，得到负极极片。
测试部分
(1)人造SEI膜中第一无机锂盐含量测试
取制备好的负极极片(二次电池化成前)，测试负极活性材料表面的人造SEI膜中第一无机锂盐的含量。
采用美国赛默飞世尔(Thermo)科技公司的Escalab 250Xi型X射线光电子能谱仪进行测试，X射线激发源是单色Al Kα(hv＝1486.6eV)，负极膜片的分析区域为700μm×300μm，取距离负极膜层表层～5nm处采集C、O、S、Li元素的光谱并用XPS peak软件分峰处理，通过各元素的含量定量分析人造SEI膜中Li 2CO 3、Li 2SO 3的质量百分含量。
为了保证测试结果的准确度，可取多个(例如10个)不同位置处的光谱进行定量分析，取平均值作为测试结果。
(2)二次电池直流内阻DCR测试
在25℃下，将二次电池以0.5C恒流充电到50％SOC，静置10min后，以0.1C恒定电流放电10s，记录放电后的电压U 1；然后将二次电池以1C恒定电流继续放电1s，记录放电后的电压U 2。二次电池的直流内阻DCR(mohm)＝(U 1-U 2)/(1C-0.1C)。
(3)二次电池高温存储性能测试
在25℃下，将二次电池以1C恒流充电至3.65V，然后以3.65V恒压充电至电流小于0.05C；将二次电池以1C恒流放电至2.5V，再以0.04C放电至2.5V，此时二次电 池为0％SOC，测试此时二次电池的体积作为存储前的体积。然后将二次电池置于60℃环境下存储30天，每5天测试一次二次电池的体积。二次电池的体积膨胀率(％)＝(存储后体积/存储前体积-1)×100％。
表1给出实施例1～24和对比例1～2的参数。表2给出实施例1～24和对比例1～2的测试结果。
表1
  锂金属质量 混合气体 静置时间(h)
实施例1 1mg/1540mm 2 O 2:CO 2＝1:12(体积比) 12
实施例2 1mg/1540mm 2 O 2:CO 2＝1:8(体积比) 12
实施例3 1mg/1540mm 2 O 2:CO 2＝1:4(体积比) 12
实施例4 1mg/1540mm 2 O 2:CO 2＝1:2(体积比) 12
实施例5 1mg/1540mm 2 O 2:CO 2＝2:1(体积比) 12
实施例6 1mg/1540mm 2 O 2:CO 2＝4:1(体积比) 12
实施例7 0.1mg/1540mm 2 O 2:CO 2＝1:2(体积比) 12
实施例8 0.5mg/1540mm 2 O 2:CO 2＝1:2(体积比) 12
实施例9 0.8mg/1540mm 2 O 2:CO 2＝1:2(体积比) 12
实施例10 2mg/1540mm 2 O 2:CO 2＝1:2(体积比) 12
实施例11 1mg/1540mm 2 O 2:SO 2＝1:2(体积比) 1
实施例12 1mg/1540mm 2 O 2:SO 2＝1:2(体积比) 6
实施例13 1mg/1540mm 2 O 2:SO 2＝1:2(体积比) 12
实施例14 1mg/1540mm 2 O 2:SO 2＝1:2(体积比) 48
实施例15 1mg/1540mm 2 O 2:SO 2＝1:2(体积比) 72
实施例16 0.5mg/1540mm 2 O 2:SO 2＝4:1(体积比) 12
实施例17 1mg/1540mm 2 O 2:SO 2＝4:1(体积比) 12
实施例18 1mg/1540mm 2 O 2:SO 2＝2:1(体积比) 12
实施例19 1mg/1540mm 2 O 2:SO 2＝1:1(体积比) 12
实施例20 1mg/1540mm 2 O 2:SO 2＝1:4(体积比) 12
实施例21 1mg/1540mm 2 O 2:SO 2＝1:12(体积比) 12
实施例22 1mg/1540mm 2 O 2:CO 2:SO 2＝1:2:2(体积比) 12
实施例23 1mg/1540mm 2 O 2:CO 2:SO 2＝1:1:2(体积比) 12
实施例24 1mg/1540mm 2 O 2:CO 2:SO 2＝1:2:1(体积比) 12
对比例1 \ \ \
对比例2 1mg/1540mm 2 \ \
表2
Figure PCTCN2022096212-appb-000002
Figure PCTCN2022096212-appb-000003
由表2的测试结果可以看出，负极极片补锂且经过混合气体处理后能在负极活性材料表面形成一层均匀的人造SEI膜，应用于二次电池中后，人造SEI膜表面还会继续生成一层常规SEI膜。人造SEI膜具有电子绝缘性，能抑制常规SEI膜的分解，降低二次电池产气，因此二次电池能具有较低的体积膨胀率。
由表2的测试结果可以看出，选择合适的补锂量、合适的混合气体比例、合适的静置反应时间，可以使人造SEI膜中Li 2CO 3、Li 2SO 3含量适中，人造SEI膜能在持续保护负极活性材料的同时具有较低的阻抗，进而二次电池还同时具有较低的体积膨胀率和较低的DCR。
对比例1的负极极片没有经过任何处理，负极活性材料表面常规SEI膜的成膜阻抗较高，因此二次电池的DCR较高；此外，常规SEI膜的结构也不稳定，二次电池低电压存储时易分解，因此二次电池的体积膨胀率也较高。
对比例2的锂金属没有经过混合气体处理，注液后锂金属与负极发生反应嵌入负极活性材料颗粒内部，负极活性材料表面形成的常规SEI膜的厚度降低，可以在一定程度上降低二次电池的DCR。但是常规SEI膜的厚度降低，不能有效保护负极活性材料， 电解液中的有机溶剂等容易在负极活性材料表面发生还原反应并产生大量气体产物，因此，二次电池的体积膨胀率增加。
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 (15)

  1. 一种负极极片，包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜层，其中，
    至少部分负极活性材料表面具有人造固体电解质界面膜，所述人造固体电解质界面膜包括第一无机锂盐，所述第一无机锂盐选自Li 2CO 3、Li 2SO 3中的一种或两种；
    可选地，基于人造固体电解质界面膜的总质量计，第一无机锂盐的质量百分含量为20％～90％，可选地为80％～90％。
  2. 根据权利要求1所述的负极极片，其中，所述人造固体电解质界面膜还包括Li 2O，可选地，所述人造固体电解质界面膜由第一无机锂盐以及Li 2O组成，
    可选地，基于人造固体电解质界面膜的总质量计，Li 2O的质量百分含量为10％～80％，可选地为10％～20％。
  3. 根据权利要求1或2所述的负极极片，其中，所述人造固体电解质界面膜的厚度为5nm～10nm。
  4. 根据权利要求1-3任一项所述的负极极片，其中，所述人造固体电解质界面膜中任意一点的C、O、S、Li元素各自的质量浓度偏差均为2％以下。
  5. 根据权利要求1-4任一项所述的负极极片，其中，所述人造固体电解质界面膜位于所述负极活性材料颗粒的80％～100％的表面，可选地为95％～100％。
  6. 根据权利要求1-5任一项所述的负极极片，其中，基于负极膜层中负极活性材料的总质量计，表面具有人造固体电解质界面膜的负极活性材料的质量百分含量为80％～100％，可选地为95％～100％。
  7. 根据权利要求1-6任一项所述的负极极片，其中，所述负极极片应用于二次电池，化成结束后，至少部分负极活性材料表面同时具有人造固体电解质界面膜以及位于人造固体电解质界面膜表面的常规固体电解质界面膜。
  8. 一种用于制备负极极片的方法，包括如下步骤：
    S10，提供初始负极极片，初始负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜层；
    S20，将锂金属层设置在负极膜层上，得到补锂负极极片；
    S30，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜，所述人造固体电解质界面膜包括第一无机锂盐，所述第一无机锂盐选自Li 2CO 3、Li 2SO 3中的一种或两种。
  9. 根据权利要求8所述的方法，其中，在S20中，锂金属的质量为0.1mg/1540mm 2～2mg/1540mm 2。
  10. 根据权利要求8或9所述的方法，其中，在S30中，
    混合气体中O 2的体积与CO 2和SO 2的总体积之比为1:12～4:1，可选地为1:8～2:1；和/或，
    反应时间为1h～72h，可选地为2h～48h。
  11. 根据权利要求8-10任一项所述的方法，其中，在S30中，使补锂负极极片中的锂金属与包含O 2以及CO 2、SO 2中的一种或两种的混合气体反应的方法包括：
    将补锂负极极片置于非水有机溶剂中，可选地，所述非水有机溶剂选自碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯中的一种或几种，向非水有机溶剂中持续通入包含O 2以及CO 2、SO 2中的一种或两种的混合气体，使锂金属与混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜；或
    将补锂负极极片直接置于包含O 2以及CO 2、SO 2中的一种或两种的混合气体中，使锂金属与混合气体反应，以在至少部分负极活性材料的表面形成人造固体电解质界面膜。
  12. 一种二次电池，包括根据权利要求1-7任一项所述的负极极片，或根据权利要求8-11任一项所述的方法制备的负极极片。
  13. 一种电池模块，包括根据权利要求12所述的二次电池。
  14. 一种电池包，包括根据权利要求12所述的二次电池、根据权利要求13所述的电池模块中的一种。
  15. 一种用电装置，包括根据权利要求12所述的二次电池、根据权利要求13所述的电池模块、根据权利要求14所述的电池包中的至少一种。
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