WO2023060534A1 - 一种二次电池 - Google Patents

一种二次电池 Download PDF

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Publication number
WO2023060534A1
WO2023060534A1 PCT/CN2021/123995 CN2021123995W WO2023060534A1 WO 2023060534 A1 WO2023060534 A1 WO 2023060534A1 CN 2021123995 W CN2021123995 W CN 2021123995W WO 2023060534 A1 WO2023060534 A1 WO 2023060534A1
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Prior art keywords
negative electrode
oxide
active material
layer
secondary battery
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PCT/CN2021/123995
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English (en)
French (fr)
Inventor
郭锁刚
付成华
张辰辰
叶永煌
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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 CN202180094959.4A priority Critical patent/CN116941084A/zh
Priority to EP21945364.4A priority patent/EP4195349B1/en
Priority to PCT/CN2021/123995 priority patent/WO2023060534A1/zh
Priority to US18/147,201 priority patent/US20230387380A1/en
Publication of WO2023060534A1 publication Critical patent/WO2023060534A1/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
    • H01M10/052—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
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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 invention relates to the field of batteries, in particular to a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles , military equipment, aerospace and other fields. Due to the great development of secondary batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • the lithium dendrites generated during the use of secondary batteries will pierce the separator, thereby causing a short circuit and causing unsafe phenomena such as fire, explosion, and scrapping of the battery.
  • a coating is provided on the separator of the battery to avoid the rapid growth of lithium dendrites from piercing the separator.
  • the tension of the separator is relatively high.
  • the separator may be broken, and the coating on the surface is broken, so that it cannot function.
  • the lithium storage capacity of the material of the coating is low.
  • a solution in the prior art is to adopt a design in which the capacity of the positive electrode of the battery is smaller than that of the negative electrode.
  • the present application is made in view of the above problems, and its purpose is to provide a secondary battery that can not only improve the energy density, but also solve the problem of lithium deposition.
  • the present application provides the following secondary battery, a battery module including the secondary battery, a battery pack including the battery module, and an electrical device.
  • the first aspect of the present application provides a secondary battery, which includes a positive electrode sheet and a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is arranged on the negative electrode On at least one surface of the current collector, the surface of the negative electrode active material layer opposite to the negative electrode current collector is provided with an insulating layer and a reaction layer in sequence, and the reaction layer includes graphite, silicon, silicon oxide, oxide At least one of silicon oxide, tin oxide, copper oxide, zinc oxide, the capacity of the positive electrode active material layer per unit area in the positive electrode sheet is denoted as A1, the capacity of the negative electrode active material layer per unit area in the negative electrode sheet The capacity is recorded as B1, then B1/A1 ⁇ 1, which may be 0.3 ⁇ B1/A1 ⁇ 1, more preferably 0.5 ⁇ B1/A1 ⁇ 0.91.
  • the present application makes the energy density of the battery higher than that of a conventional battery by making the capacity of the positive active material layer per unit area in the positive pole sheet greater than that of the negative active material layer per unit area in the negative pole piece, and by setting a specific
  • the layer structure, especially the insulating layer and reaction layer on the surface of the negative electrode active material layer, can effectively prevent the problem of lithium precipitation, thereby improving the energy density, safety and cycle performance of the secondary battery.
  • the insulating layer comprises alumina, boehmite, zirconia, titania, magnesia, cobalt oxide, nickel oxide, gallium oxide, germanium oxide, yttrium oxide, strontium oxide, barium oxide, molybdenum oxide at least one of the In this way, a barrier can be formed through physical action and the growth of lithium dendrites can be suppressed.
  • the battery satisfies:
  • d thickness of the reaction layer, in ⁇ m
  • A1 The capacity of the positive electrode active material per unit area of the positive electrode sheet, the unit is mAh/cm 2 ;
  • B1 the capacity of the negative electrode active material per unit area of the negative electrode sheet, the unit is mAh/cm 2 ;
  • m1 the gram capacity of the reaction layer, in mAh/g
  • ⁇ density of the reaction layer, in g/cm 3 .
  • the reaction layer can fully absorb the lithium dendrites passing through the insulating layer, ensuring the safety of the secondary battery performance and cycle performance.
  • the gram capacity m1 of the reaction layer satisfies m1 ⁇ 150mAh/g, and may be 1000mAh/g ⁇ m1 ⁇ 2500mAh/g.
  • m1 ⁇ 150mAh/g may be 1000mAh/g ⁇ m1 ⁇ 2500mAh/g.
  • the density ⁇ of the reaction layer satisfies 0.2 g/cm 3 ⁇ ⁇ ⁇ 3 g/cm 3 , and may be 1 g/cm 3 ⁇ ⁇ ⁇ 2 g/cm 3 . Thereby, lithium dendrites can be better absorbed.
  • the thickness of the reaction layer is 1 ⁇ m-30 ⁇ m, optionally 2 ⁇ m-30 ⁇ m, so that the lithium dendrites can be fully absorbed without increasing the volume of the battery.
  • the thickness of the insulating layer is 1 ⁇ m-10 ⁇ m, optionally 2 ⁇ m-4 ⁇ m. Therefore, while exerting the physical barrier effect, the volume of the battery is not increased.
  • the Young's modulus of the insulating layer is greater than or equal to 6GPa, and may be 6GPa-30GPa. As a result, the physical barrier effect can be better exerted.
  • the particle size of the material in the reaction layer is 0.1 ⁇ m-4 ⁇ m, optionally 0.1 ⁇ m-0.8 ⁇ m; and/or, the particle size of the material in the insulating layer is 0.1 ⁇ m-10 ⁇ m , optional 0.1 ⁇ m-4 ⁇ m. In this way, the respective functions of preventing lithium precipitation of the reaction layer and the insulating layer can be better exerted.
  • the capacity B1 of the negative electrode active material layer per unit area in the negative electrode sheet is 0.3mAh/cm 2 -7mAh/cm 2 , optionally 1mAh/cm 2 -5mAh/cm 2 .
  • the capacity A1 of the positive electrode active material layer per unit area in the positive electrode sheet is 1mAh/cm 2 -7mAh/cm 2 , optionally 2mAh/cm 2 -5mAh/cm 2 .
  • the energy density of a battery can be improved.
  • the second aspect of the present application also provides a battery module including the secondary battery of the first aspect of the present application.
  • a third aspect of the present application provides a battery pack, including the battery module of the second aspect of the present application.
  • the fourth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. kind.
  • the insulating layer can form a barrier through physical action to inhibit the growth of lithium dendrites.
  • the amount of lithium precipitated is too large, after the lithium dendrites penetrate the insulating layer, the It can react with it and ablate the part of lithium dendrites that pass through the insulating layer.
  • the two coatings on the negative electrode namely the insulating layer and the reactive layer, can prevent failures caused by battery manufacturing defects such as tab insertion, pole piece folding, and dust particles falling inadvertently.
  • the insulating layer and the reaction layer can increase the short-circuit resistance and prevent the positive electrode aluminum foil, dust particles, etc. from contacting the negative electrode active material layer.
  • the design in which the positive electrode capacity is greater than the negative electrode capacity used in this application can increase the energy density, but if the above coating is not added, the design will fail due to the formation of lithium dendrites. After adding the above coating, the design can be used safely.
  • the two coatings provided on the negative electrode by the present application have a synergistic effect, and the dendrite suppression effect of the insulating layer can prevent the reaction layer from conducting at the beginning and causing capacity loss.
  • the combination of the two makes the reaction layer only for emerging and The risky dendrites react to improve the safety performance of the battery, and finally obtain a battery with both high energy density and high safety.
  • FIG. 1 is a schematic diagram of a layer structure of a negative electrode of a secondary battery according to an embodiment of the present application.
  • Fig. 2 is the photograph of the layer structure of the negative electrode of the secondary battery of the present application one embodiment, wherein (a) is the X-ray energy spectrum (EDS) image of negative electrode layer structure, (b) is the scanning electron microscope of negative electrode layer structure ( SEM) images.
  • EDS X-ray energy spectrum
  • SEM scanning electron microscope of negative electrode layer structure
  • FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment 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.
  • step (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 also 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).
  • a secondary battery which includes a positive electrode sheet and a negative electrode sheet.
  • the above-mentioned negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer.
  • the surface of the above-mentioned negative electrode active material layer opposite to the above-mentioned negative electrode current collector is provided with an insulating layer and a reaction layer in sequence, and the above-mentioned reaction layer includes graphite, silicon, silicon oxide, silicon oxide, oxide At least one of tin, copper oxide, and zinc oxide, the capacity of the positive electrode active material layer per unit area in the above-mentioned positive electrode sheet is marked as A1, and the capacity of the negative electrode active material layer per unit area in the above-mentioned negative electrode sheet is marked as B1, then B1/A1 ⁇ 1.
  • 0.3 ⁇ B1/A1 ⁇ 1 such as 0.5 ⁇ B1/A1 ⁇ 0.91. It is possible to design following customer requirements. For example, the use scenario is high battery life, but it does not need to carry out long cycle, so it can use the design of extremely low B1/A1.
  • the B1/A1 value is related to the theoretical gram capacity of the positive and negative active materials, the coating thickness of the positive and negative electrodes, and the proportion of the active material.
  • the positive and negative electrode capacity ratio of the battery generally needs to be less than a certain value, so as to ensure that the battery does not undergo significant lithium deposition during normal use, resulting in battery failure.
  • setting the capacity ratio of the positive and negative electrodes in this way can avoid lithium deposition, it will lead to a thicker battery cell and seriously reduce the energy density of the battery.
  • the present application is contrary to the conventional battery, by making the capacity of the positive electrode active material layer per unit area in the positive pole sheet (hereinafter also referred to as the positive electrode capacity for short) greater than the capacity of the negative electrode active material layer per unit area in the negative electrode sheet (hereinafter sometimes referred to as Referred to as negative electrode capacity), it can make the energy density of the battery higher than that of conventional batteries.
  • the positive electrode capacity is greater than the negative electrode capacity used in this application, the battery will fail due to the formation of a large number of lithium dendrites.
  • the applicant of the present application found that by setting a special layer structure, especially setting an insulating layer and a reaction layer on the surface of the negative electrode active material layer, that is, a composite coating, the problem of lithium precipitation can be effectively prevented.
  • the battery of the present invention not only realizes the improvement of the energy density of the secondary battery, but also solves the hidden danger in safety.
  • the insulating layer arranged on the surface of the negative electrode active material layer prevents lithium dendrites from piercing the layer of the separator with physical effects, and the reaction layer arranged on the insulating layer prevents lithium dendrites from chemically acting Puncture the layer of the barrier membrane.
  • the insulating layer may be a coating coated on the surface of the negative electrode active material layer, and the reaction layer may be a coating coated on the insulating layer.
  • a battery with a positive electrode capacity greater than the negative electrode capacity will precipitate lithium during any cycle, most of the lithium layer exists under the insulating layer, and some of the precipitated lithium forms lithium dendrites that penetrate the insulating layer and pass through the insulating layer. Lithium dendrites will be absorbed by the reaction layer after touching the reaction layer, so that the dendrites will no longer grow.
  • the material that can be used in the reaction layer only needs to be capable of chemically reacting with lithium dendrites, so as to prevent lithium dendrites from piercing the separator.
  • the same active material as that used in the negative electrode active material layer can be used.
  • Examples of such a material that reversibly reacts with lithium dendrites include graphite, silicon, silicon oxide, and silicon oxide, among which silicon oxide can be used in particular.
  • the lithium ions that form the lithium dendrites that penetrate the insulating layer and are consumed by the reaction layer do not account for too much in the entire battery, even if the reaction layer is a material that irreversibly reacts with lithium dendrites, the impact on capacity Also very small.
  • Examples of such irreversible materials include tin oxide, copper oxide, and zinc oxide. Such materials can form LiM alloys with metallic lithium, which contributes to better deposition of lithium.
  • the above-mentioned insulating layer comprises aluminum oxide, boehmite, zirconium oxide, titanium oxide, magnesium oxide, cobalt oxide, nickel oxide, gallium oxide, germanium oxide, yttrium oxide, strontium oxide, barium oxide, molybdenum oxide at least one of .
  • boehmite is particularly optional.
  • the above battery satisfies:
  • d thickness of the reaction layer, in ⁇ m
  • A1 The capacity of the positive electrode active material per unit area of the positive electrode sheet, the unit is mAh/cm 2 ;
  • B1 the capacity of the negative electrode active material per unit area of the negative electrode sheet, the unit is mAh/cm 2 ;
  • m1 the gram capacity of the reaction layer, in mAh/g
  • ⁇ density of the reaction layer, in g/cm 3 .
  • the reaction layer can fully absorb the lithium dendrites passing through the insulating layer, ensuring the safety and reliability of the secondary battery. cycle performance, and it can also ensure that the battery volume is not excessively increased.
  • the gram capacity m1 of the above reaction layer satisfies m1 ⁇ 150mAh/g, may be 150mAh/g-3000mAh/g, more preferably 1000mAh/g-2500mAh/g.
  • lithium dendrites can be better absorbed, and the volume occupied by the reaction layer can be reduced.
  • the density ⁇ of the reaction layer satisfies 0.2 g/cm 3 ⁇ ⁇ ⁇ 3 g/cm 3 , optionally 1 g/cm 3 ⁇ ⁇ ⁇ 2 g/cm 3 . Thereby, lithium dendrites can be better absorbed.
  • the thickness of the reaction layer is 1 ⁇ m-30 ⁇ m, optionally 2 ⁇ m-30 ⁇ m, so that the lithium dendrites can be fully absorbed without increasing the volume of the battery.
  • the thickness of the insulating layer is 1 ⁇ m-10 ⁇ m, optionally 2 ⁇ m-4 ⁇ m. In this way, while the barrier is formed through physical action, the volume of the battery is not increased.
  • the thickness of the insulating layer depends on the particle size of the material constituting the insulating layer and the process of forming the insulating layer. A certain range of thickness does not affect the cycle performance. If the process can meet the requirements, the thinner the better, but the premise is that complete insulation can be achieved , otherwise the active lithium will be consumed in the initial stage.
  • the Young's modulus of the insulating layer is greater than or equal to 6GPa, and may be 6GPa-30GPa. As a result, the physical barrier effect can be better exerted.
  • the mechanical penetration strength of lithium dendrites is 6GPa. In order to play a physical barrier role, the Young's modulus of the insulating layer needs to be greater than or equal to 6GPa.
  • the particle size of the material constituting the above-mentioned reaction layer is 0.1 ⁇ m-4 ⁇ m, optionally 0.1 ⁇ m-0.8 ⁇ m; and/or, the particle size of the material constituting the above-mentioned insulating layer is 0.1 ⁇ m-10 ⁇ m , optional 0.1 ⁇ m-4 ⁇ m.
  • the particle size of the material in the reaction layer is not larger than the thickness of the reaction layer, and the particle size of the material in the insulating layer is not larger than the thickness of the insulating layer. In this way, the respective functions of the reaction layer and the insulating layer to prevent lithium precipitation can be better exerted.
  • the capacity of the negative electrode active material layer per unit area in the negative electrode sheet is 0.3mAh/cm 2 -7mAh/cm 2 , optionally 1mAh/cm 2 -5mAh/cm 2 .
  • the capacity of the positive electrode active material layer per unit area in the positive electrode sheet is 1mAh/cm 2 -7mAh/cm 2 , optionally 2mAh/cm 2 -5mAh/cm 2 .
  • the second aspect of the present application also provides a battery module including the secondary battery of the first aspect of the present application.
  • a third aspect of the present application provides a battery pack, including the battery module of the second aspect of the present application.
  • the fourth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. kind.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • 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 ions to pass through.
  • the positive pole piece includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • positive active materials known in the art for batteries can be used in the positive active material layer.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon At least one of a composite material, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also may be abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive active material layer may optionally further include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive active material layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, and the surface of the negative electrode active material layer opposite to the negative electrode current collector is provided with an insulating layer and a reaction layer in sequence. layer.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • negative electrode active materials known in the art for batteries can be used in the negative electrode active material.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other conventional materials that can be used as the active material of the negative electrode of the battery can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative active material layer may further optionally include a binder.
  • the binding agent can be a binding agent commonly used in the battery field without special limitation, and the binding agent can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide ( PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS), polyvinylidene fluoride, acryl-based polymers, diene-based polymers At least one of materials and natural rubber.
  • polystyrene-acrylate emulsion binders can be used.
  • the negative active material layer may optionally further include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a dispersant may also be used when preparing the negative active material layer.
  • the dispersant is used to improve dispersion uniformity and coating property, and may be a dispersant commonly used in the battery field, such as a polymer dispersant.
  • polyvinyl alcohol modified polyvinyl alcohol having functional groups other than hydroxyl group such as acetyl group, sulfo group, carboxyl group, carbonyl group, amino group, modified by various salts, others modified by anion or cation, by Acetal-modified polyvinyl alcohol-based resins, various (meth)acrylic polymers, polymers derived from ethylenically unsaturated hydrocarbons, various cellulose-based resins, etc., or copolymers of these , but are not limited to these.
  • the polymer dispersants may be used alone or in combination of two or more.
  • the negative electrode active material layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • At least one material including graphite, silicon, silicon oxide, silicon oxide, tin oxide, copper oxide, and zinc oxide may be used in the reaction layer.
  • the insulating layer can use at least one material containing alumina, boehmite, zirconia, titanium oxide, magnesium oxide, cobalt oxide, nickel oxide, gallium oxide, germanium oxide, yttrium oxide, strontium oxide, barium oxide, and molybdenum oxide .
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode active material layer slurry; the above-mentioned materials for forming an insulating layer, as well as a dispersant, a binding agent and any other components are dispersed in a solvent (such as deionized water) to form a slurry for an insulating layer, Wherein the dispersant and binding agent can use the above-mentioned materials enumerated in the negative electrode active material layer; the above-mentioned material forming the reaction layer, and dispersant, binding agent and any other components are dispersed in solvent (such as deionized water) , form the slurry for the reaction layer, wherein the dispersant and the binder can use the above-mentioned materials listed in the negative electrode
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is further included in the secondary battery.
  • 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 at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • 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 case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • Fig. 1 is a schematic diagram of the layer structure of the negative electrode of the secondary battery according to an embodiment of the present application. Fig. 1 only shows the sequentially stacked negative electrode current collector 500, negative electrode active material layer 501, insulating layer 502 and reaction layer 503 in the negative electrode. .
  • FIG. 2 is a photograph of a layer structure of a negative electrode of a secondary battery according to an embodiment of the present application.
  • (a) is the X-ray energy spectrum (EDS) image of the negative electrode layer structure
  • (b) is the scanning electron microscope (SEM) image of the negative electrode layer structure.
  • EDS X-ray energy spectrum
  • SEM scanning electron microscope
  • FIG. 3 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • 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 chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 5 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 one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 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 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • a plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in 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 devices may include 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, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 8 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 may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the battery is repeatedly charged and discharged through the following steps, and the discharge capacity retention rate of the battery is calculated.
  • capacity loss rate ((discharge capacity of the first cycle-discharge capacity after N cycles)/discharge capacity of the first cycle) ⁇ 100%, the capacity loss rate of the battery after N cycles is calculated.
  • the capacity of the battery is tested by charging and discharging at a small rate (0.1-0.3C), and the volume energy density is calculated by the following formula.
  • volume energy density (Wh/L) capacity (Ah) * platform voltage (V) / cell volume (L)
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , superconducting carbon black SP as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were dispersed in N- Methylpyrrolidone (NMP) was uniformly mixed to obtain positive electrode slurry; the positive electrode slurry was evenly coated on the aluminum foil of the positive electrode current collector, and after drying, cold pressing, slitting, and cutting into pieces, the positive electrode sheet was obtained.
  • NMP N- Methylpyrrolidone
  • Polyethylene film is used as the isolation film.
  • Slurry preparation for the insulating layer disperse boehmite, polyvinyl alcohol dispersant, and polystyrene-acrylate emulsion binder at a mass ratio of 96.5:0.5:3 in deionized water as a solvent and mix evenly.
  • the particle size of the boehmite namely, the median particle size Dv50 is 0.3 ⁇ m.
  • Slurry preparation for the reaction layer disperse silicon oxide, polyvinyl alcohol dispersant, and polystyrene-acrylate emulsion binder in deionized water as a solvent at a mass ratio of 96.5:0.5:3 and mix evenly.
  • the particle size (ie median particle size) of silicon oxide is 1 ⁇ m.
  • Slurry preparation of the negative electrode active material layer the negative electrode active material artificial graphite, superconducting carbon black as a conductive agent, SBR as a binder and CMC-Na as a thickener according to a mass ratio of 96:1:1:2 Disperse in deionized water as a solvent and mix uniformly to obtain negative electrode slurry.
  • Preparation of the negative electrode sheet uniformly coat the slurry of the negative electrode active material layer on the copper foil of the negative electrode current collector, and after drying, coat the slurry of the insulating layer on the negative electrode active material layer.
  • the thickness of the insulating layer is 2 ⁇ m; after drying, the slurry of the reaction layer is coated on the insulating layer, the thickness of the reaction layer is 7 ⁇ m, after drying, cold pressing, slitting and cutting, the negative electrode sheet is obtained.
  • ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, and then dissolve fully dried lithium salt LiPF 6 in the mixed In the final organic solvent, an electrolyte solution with a concentration of 1 mol/L was prepared.
  • the above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and the battery is prepared by winding, wherein the capacity of the negative electrode is 0.3 times the capacity of the positive electrode;
  • the preparation of the battery cell is carried out; then, the battery cell is placed in the outer packaging shell, and after drying, the electrolyte is injected, and the secondary battery is obtained through vacuum packaging, standing, chemical formation, shaping and other processes.
  • a secondary battery was prepared in the same manner as in Example 1 except that the reaction conditions were changed as shown in Table 1 and Table 2.
  • Example 2 to 11 shown in Table 1 the value of B1/A1 was changed by changing the negative electrode capacity B1, and the thickness d of the reaction layer was also changed.
  • Embodiment 12,13 shown in table 2 changed the kind of insulating layer material
  • embodiment 14,15 changed the kind and thickness of reaction layer material
  • embodiment 16 ⁇ 18 changed the thickness of insulating layer
  • embodiment 19 ⁇ 23 The capacity A1 of the positive electrode active material layer per unit area in the positive electrode sheet is changed.
  • the capacity is adjusted by changing the thickness of the positive electrode active material layer. Thick coating is required, and the existing process is difficult. The larger the value of A1, The higher the requirements of the coating process, the more thick the coating is, the solvent is difficult to volatilize, and the diaphragm is easy to crack.
  • a secondary battery was prepared in the same manner as in Example 1 except that the reaction conditions were changed as shown in Table 3.
  • Comparative Example 5 when only an insulating layer is provided without a reaction layer, the cycle life is still very poor. It can be seen from Comparative Example 6 that when only the reaction layer is provided without the insulation layer, the cycle life is greatly improved, but the cycle life is still shorter than that of Example 11 in which both the reaction layer and the insulation layer are provided. From this, it can be seen that by providing the reaction layer and the insulating layer on the negative electrode sheet, there is a synergistic effect of greatly improving safety.
  • 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

本申请提供了一种二次电池，包括正极极片和负极极片，负极极片包括负极集流体和负极活性物质层，负极活性物质层设置在负极集流体的至少一个表面上，负极活性物质层的与负极集流体侧相反一侧的表面依次设置有绝缘层和反应层，且反应层包括石墨、硅、氧化硅、氧化亚硅、氧化锡、氧化铜、氧化锌中的至少一种，正极极片中单位面积的正极活性物质层的容量记为A1，负极极片中单位面积的负极活性物质层的容量记为B1，则B1/A1＜1。在本申请所提供的二次电池中，通过使B1/A1＜1，提高了能量密度，并且通过设置特殊的层结构，而具有较好的循环性能。

Description

一种二次电池 技术领域
本发明涉及电池领域，尤其涉及一种二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，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。由于二次电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。
但是二次电池、特别是锂离子二次电池在使用的过程中产生的锂枝晶会刺穿隔离膜，从而造成短路，引起电池起火、爆炸、报废等不安全现象。为此，现有技术中有在电池的隔离膜上设置涂层以避免锂枝晶快速增长后刺破隔离膜的发明。但是在实际电池使用过程中，隔离膜的张力比较大，在锂枝晶穿刺隔离膜的过程中，隔离膜可能被顶破，表面的涂层破碎，从而无法起到作用。而且，还存在涂层的材料的储锂量低的问题。
为了防止电池在使用过程中发生析锂，现有技术中的一个解决手段是采用使电池的正极容量小于负极容量的设计。虽然这样设置正负极容量比能够避免析锂，但会导致电芯厚度较厚，严重降低电池的能量密度。因此，现有的电池结构仍有待改进。
发明内容
本申请是鉴于上述问题而进行的，其目的在于，提供一种不仅可以提高能量密度，还可以解决析锂问题的二次电池。
为了达到上述目的，本申请提供了如下的二次电池以及包括该二次电池的电池模块、包括该电池模块的电池包、和用电装置。
本申请的第一方面提供了一种二次电池，其包括正极极片和负极极片，所述负极极片包括负极集流体和负极活性物质层，所述负极活 性物质层设置在所述负极集流体的至少一个表面上，所述负极活性物质层的与所述负极集流体侧相反一侧的表面依次设置有绝缘层和反应层，且所述反应层包括石墨、硅、氧化硅、氧化亚硅、氧化锡、氧化铜、氧化锌中的至少一种，所述正极极片中单位面积的正极活性物质层的容量记为A1，所述负极极片中单位面积的负极活性物质层的容量记为B1，则B1/A1＜1，可选为0.3≤B1/A1≤1，更可选为0.5≤B1/A1≤0.91。
由此，本申请通过使正极极片中单位面积的正极活性物质层的容量大于负极极片中单位面积的负极活性物质层的容量，使电池的能量密度高于常规电池，并且通过设置特定的层结构，特别是在负极活性物质层的表面设置绝缘层和反应层，能够有效防止析锂问题，从而提高二次电池的能量密度、安全性和循环性能。
在任意实施方式中，所述绝缘层包含氧化铝、勃姆石、氧化锆、氧化钛、氧化镁、氧化钴、氧化镍、氧化镓、氧化锗、氧化钇、氧化锶、氧化钡、氧化钼中的至少一种。由此能够通过物理作用形成阻隔，抑制锂枝晶的生长。
在任意实施方式中，所述电池满足：
Figure PCTCN2021123995-appb-000001
d：反应层的厚度，单位为μm；
A1：正极极片的单位面积正极活性物质的容量，单位为mAh/cm 2；
B1：负极极片的单位面积负极活性物质的容量，单位为mAh/cm 2；
m1：反应层的克容量，单位为mAh/g；
ρ：反应层的密度，单位为g/cm 3。
通过使反应层的厚度与正极极片和负极极片中单位面积的活性物质层的容量满足上述关系，能够使反应层充分吸收掉穿过绝缘层的锂枝晶，保证了二次电池的安全性和循环性能。
在任意实施方式中，所述反应层的克容量m1满足m1≥150mAh/g，可选为1000mAh/g≤m1≤2500mAh/g。由此，能够更好地吸收锂枝晶，且减小反应层所占的体积。
在任意实施方式中，所述反应层的密度ρ满足0.2g/cm 3≤ρ≤3g/cm 3，可选为1g/cm 3≤ρ≤2g/cm 3。由此，能够更好地吸收锂枝晶。
在任意实施方式中，所述反应层的厚度为1μm-30μm，可选为2μm-30μm，由此能够在充分吸收锂枝晶的同时，不增大电池的体积。
在任意实施方式中，所述绝缘层的厚度为1μm-10μm，可选为2μm-4μm。由此在发挥物理阻隔作用的同时，不增大电池的体积。
在任意实施方式中，所述绝缘层的杨氏模量大于等于6GPa，可选为6GPa-30GPa。由此能够更好地发挥物理阻隔作用。
在任意实施方式中，所述反应层中材料的颗粒粒径为0.1μm-4μm，可选为0.1μm-0.8μm；和/或，所述绝缘层中材料的颗粒粒径为0.1μm-10μm，可选为0.1μm-4μm。由此能够更好地发挥反应层和绝缘层各自的防析锂作用。
在任意实施方式中，所述负极极片中单位面积的负极活性物质层的容量B1为0.3mAh/cm 2-7mAh/cm 2，可选为1mAh/cm 2-5mAh/cm 2。
在任意实施方式中，所述正极极片中单位面积的正极活性物质层的容量A1为1mAh/cm 2-7mAh/cm 2，可选为2mAh/cm 2-5mAh/cm 2。由此，能够提高电池的能量密度。
本申请的第二方面还提供一种电池模块，包括本申请的第一方面的二次电池。
本申请的第三方面提供一种电池包，包括本申请的第二方面的电池模块。
本申请的第四方面提供一种用电装置，包括选自本申请的第一方面的二次电池、本申请的第二方面的电池模块或本申请的第三方面的电池包中的至少一种。
本申请能够发挥如下的技术效果：
防止电池使用过程中析锂后所形成的锂枝晶刺破隔离膜，导致电池短路失效。具体而言，当电芯析锂形成锂枝晶时，绝缘层可以通过物理作用形成阻隔，抑制锂枝晶的生长，当析锂量过大时，锂枝晶穿透绝缘层后，反应层能够与其发生反应，将穿过绝缘层的那部分锂枝晶消融掉。
此外，负极上的两个涂层、即绝缘层和反应层，能够防止电池制 造缺陷例如极耳内插、极片翻折、不慎掉入粉尘颗粒等所导致的失效。具体而言，当发生极耳翻折时，绝缘层和反应层可以起到增大短路电阻的作用，防止正极的铝箔、粉尘颗粒等接触到负极活性物质层。
本申请使用的正极容量大于负极容量的设计可以提升能量密度，但如果不增加上述涂层，该设计会由于锂枝晶的形成导致失效，增加上述涂层后，该设计就可以被安全使用。
本申请在负极上设置的两个涂层具有协同作用，绝缘层的抑制枝晶的作用可以防止反应层在起初就导电，发生容量损失，二者结和，使得反应层只针对冒出来并且有风险的枝晶进行反应，提高了电池的安全性能，最终得到既有高能量密度又具有高安全性的电池。
附图说明
图1是本申请一实施方式的二次电池的负极的层结构的示意图。
图2是本申请一实施方式的二次电池的负极的层结构的照片，其中(a)是负极层结构的X射线能谱(EDS)图像，(b)是负极层结构的扫描电子显微镜(SEM)图像。
图3是本申请一实施方式的二次电池的示意图。
图4是图3所示的本申请一实施方式的二次电池的分解图。
图5是本申请一实施方式的电池模块的示意图。
图6是本申请一实施方式的电池包的示意图。
图7是图6所示的本申请一实施方式的电池包的分解图。
图8是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
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顶盖组件；500负极集流体；501负极活性物质层；502绝缘层；503反应层。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池、电池模块、电池包和电学装置的实施方式。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，可选是顺序进行的。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)。
本申请的一个实施方式中，提出了一种二次电池，其包括正极极片和负极极片，上述负极极片包括负极集流体和负极活性物质层，上述负极活性物质层设置在上述负极集流体的至少一个表面上，上述负极活性物质层的与上述负极集流体侧相反一侧的表面依次设置有绝缘层和反应层，且上述反应层包括石墨、硅、氧化硅、氧化亚硅、氧化锡、氧化铜、氧化锌中的至少一种，上述正极极片中单位面积的正极活性物质层的容量记为A1，上述负极极片中单位面积的负极活性物质层的容量记为B1，则B1/A1＜1。
在一些实施方式中，0.3≤B1/A1＜1，例如0.5≤B1/A1≤0.91。可以跟进客户要求进行设计，比如使用场景为高续航，但是不需要进行长循环，就可以使用极低B1/A1的设计。B1/A1值与正负极活性材料的理论克容量、正负极的涂布厚度以及活性材料的占比等有关。
从电池设计上讲，为了防止电池在使用过程中发生析锂，电池的正负极容量比一般需要小于一定数值，才能保证电池在正常使用过程中不发生明显的析锂，导致电池失效。虽然这样设置正负极容量比能避免析锂，但会导致电芯厚度较厚，严重降低电池的能量密度。
而本申请与常规电池相反，通过使正极极片中单位面积的正极活性物质层的容量(以下有时也简称为正极容量)大于负极极片中单位面积的负极活性物质层的容量(以下有时也简称为负极容量)，能够使电池的能量密度高于常规电池。但本申请使用的正极容量大于负极容量的设计中，会由于大量锂枝晶的形成而导致电池失效。而本申请的申请人发现通过设置特殊的层结构，特别是在负极活性物质层的表面设置绝缘层和反应层，即，复合涂层，能够有效防止析锂问题。这样一来，本发明的电池即实现了二次电池的能量密度的提高，同时也解决了安全上的隐患。
在本发明的电池中，在负极活性物质层的表面上设置的绝缘层以物理作用来防止锂枝晶刺破隔离膜的层，在绝缘层上设置的反应层以化学作用来防止锂枝晶刺破隔离膜的层。绝缘层可以是涂覆在负极活性物质层的表面上的涂层，反应层可以是涂覆在绝缘层上的涂层。设置这种绝缘层和反应层后，保证了电池的安全性。正极容量大于负极容量的电池在任何一次循环的过程中，都会析锂，大部分的锂层存在于绝缘层下面，有部分析出的锂形成锂枝晶穿透绝缘层，穿过绝缘层的锂枝晶触碰到反应层后会被反应层吸收掉，也就使得枝晶不再生长。
反应层中可以使用的材料只要能够起到与锂枝晶发生化学反应的作用即可，从而能够防止锂枝晶刺破隔离膜，例如可以使用与负极活性物质层中相同的活性物质。作为这样的可逆地与锂枝晶发生反应的材料，可以列举例如石墨、硅、氧化硅、氧化亚硅等，特别可选使用氧化亚硅。另外，由于形成穿透绝缘层被反应层消耗的锂枝晶的锂离子在整个电池当中占比并不是太多，所以反应层即使是不可逆地与锂枝晶发生反应的材料，对容量的影响也很小。作为这样的不可逆材料可以列举例如氧化锡、氧化铜、氧化锌等，这类物质可以与金属锂形成LiM合金，有助于锂的更好的沉积。
在一些实施方式中，上述绝缘层包含氧化铝、勃姆石、氧化锆、氧化钛、氧化镁、氧化钴、氧化镍、氧化镓、氧化锗、氧化钇、氧化锶、氧化钡、氧化钼中的至少一种。特别可选使用勃姆石。通过由包含上述物质的材料形成绝缘层，能够通过物理作用形成阻隔，防止电池使用过程中产生的锂枝晶刺穿隔离膜，保证了电池的安全性。
在一些实施方式中，上述电池满足：
Figure PCTCN2021123995-appb-000002
d：反应层的厚度，单位为μm；
A1：正极极片的单位面积正极活性物质的容量，单位为mAh/cm 2；
B1：负极极片的单位面积负极活性物质的容量，单位为mAh/cm 2；
m1：反应层的克容量，单位为mAh/g；
ρ：反应层的密度，单位为g/cm 3。
通过使反应层的厚度与正极极片和负极极片的单位面积活性物质的容量满足上述关系，能够使反应层充分吸收掉穿过绝缘层的锂枝晶，保证了二次电池的安全性和循环性能，而且也能够保证不过分增大电池体积。
在一些实施方式中，上述反应层的克容量m1满足m1≥150mAh/g，可选为150mAh/g-3000mAh/g，更可选为1000mAh/g-2500mAh/g。由此，能够更好地吸收锂枝晶，且减小反应层所占的体积。
在一些实施方式中，上述反应层的密度ρ满足0.2g/cm 3≤ρ≤3g/cm 3，可选为1g/cm 3≤ρ≤2g/cm 3。由此，能够更好地吸收锂枝晶。
在一些实施方式中，上述反应层的厚度为1μm-30μm，可选为2μm-30μm，由此能够在充分吸收锂枝晶的同时，不增大电池的体积。
在一些实施方式中，上述绝缘层的厚度为1μm-10μm，可选为2μm-4μm。由此，在通过物理作用形成阻隔的同时，不增大电池的体积。绝缘层的厚度取决于构成绝缘层的材料的颗粒大小和形成绝缘层的工艺，一定范围的厚度并不影响循环性能，如果工艺可以满足要求，越薄越好，但前提是可以做到完全绝缘，否则在初期就会消耗活性锂。
在一些实施方式中，上述绝缘层的杨氏模量大于等于6GPa，可选为6GPa-30GPa。由此能够更好地发挥物理阻隔作用。锂枝晶的机械刺穿强度是6GPa，为了发挥物理阻隔作用，绝缘层的杨氏模量需要大于等于6GPa。
在一些实施方式中，构成上述反应层的材料的颗粒粒径为0.1μm-4μm，可选为0.1μm-0.8μm；和/或，构成上述绝缘层的材料的颗粒粒径为0.1μm-10μm，可选为0.1μm-4μm。其中，反应层中材料的颗粒粒径不大于反应层的厚度，绝缘层中材料的颗粒粒径不大于绝缘层的厚度。由此能够更好地发挥反应层和绝缘层各自的防止析锂作用。
在一些实施方式中，上述负极极片中单位面积的负极活性物质层的容量为0.3mAh/cm 2-7mAh/cm 2，可选为1mAh/cm 2-5mAh/cm 2。在一些实施方式中，上述正极极片中单位面积的正极活性物质层的容量为1mAh/cm 2-7mAh/cm 2，可选为2mAh/cm 2-5mAh/cm 2。由此，能够提高电池的能量密度。
本申请的第二方面还提供一种电池模块，包括本申请的第一方面 的二次电池。
本申请的第三方面提供一种电池包，包括本申请的第二方面的电池模块。
本申请的第四方面提供一种用电装置，包括选自本申请的第一方面的二次电池、本申请的第二方面的电池模块或本申请的第三方面的电池包中的至少一种。
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极活性物质层。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极活性物质层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性物质层中可采用本领域公知的用于电池的正极活性物质。作为示例，正极活性物质可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用 作电池正极活性物质的传统材料。这些正极活性物质可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极活性物质层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极活性物质层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性物质、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极活性物质层，且所述负极活性物质层的与所述负极集流体侧相反一侧的表面依次设置有绝缘层和反应层。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面， 负极活性物质层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性物质中可采用本领域公知的用于电池的负极活性物质。作为示例，负极活性物质可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性物质的传统材料。这些负极活性物质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，负极活性物质层还可选地包括粘结剂。粘结剂可以是电池领域中常用的粘结剂，没有特别限定，所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)、聚偏氟乙烯、丙烯酰基系聚合物、二烯系聚合物、天然橡胶中的至少一种。特别可以使用聚苯乙烯-丙烯酸酯乳液粘结剂。
在一些实施方式中，负极活性物质层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，在制备负极活性物质层时还可以使用分散剂。分散剂用于提高分散均匀性和涂覆性，可以是电池领域中常用的分散剂，例如可以是聚合物分散剂。聚合物分散剂可以使用聚乙烯醇、具有羟基以外的官能团例如乙酰基、磺基、羧基、羰基、氨基的改性聚 乙烯醇、通过各种盐改性、其他经阴离子或阳离子改性、通过醛类进行了缩醛改性的聚乙烯醇系树脂、或者各种(甲基)丙烯酸系聚合物、源于乙烯性不饱和烃的聚合物、各种纤维素系树脂等、或者这些的共聚物，但并不限定于这些。聚合物分散剂可单独使用一种，或者将两种以上组合使用。
在一些实施方式中，负极活性物质层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，反应层中可以使用包括石墨、硅、氧化硅、氧化亚硅、氧化锡、氧化铜、氧化锌中的至少一种材料。绝缘层可以使用包含氧化铝、勃姆石、氧化锆、氧化钛、氧化镁、氧化钴、氧化镍、氧化镓、氧化锗、氧化钇、氧化锶、氧化钡、氧化钼中的至少一种材料。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性物质、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极活性物质层浆料；将上述形成绝缘层的材料、以及分散剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成绝缘层用浆料，其中分散剂和粘结剂可以使用上述在负极活性物质层中列举的物质；将上述形成反应层的材料、以及分散剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成反应层用浆料，其中分散剂和粘结剂可以使用上述在负极活性物质层中列举的物质；将负极浆料涂覆在负极集流体上烘干后，依次涂覆绝缘层用浆料和反应层用浆料，经烘干、冷压等工序后，即可得到负极极片，其中，涂覆操作也可以通过一次涂布成型，比如在挤压涂布机上按照双层微凹版装置；或者通过多层涂布机实现。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、 高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液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、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，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，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
图1是本申请一实施方式的二次电池的负极的层结构的示意图，图1中仅表示了负极中的依次层叠的负极集流体500、负极活性物质层501、绝缘层502和反应层503。
图2是本申请一实施方式的二次电池的负极的层结构的照片。其中(a)是负极层结构的X射线能谱(EDS)图像，(b)是负极层结构的扫描电子显微镜(SEM)图像。图2的(a)和(b)中，以从上到下的顺序，最上层为反应层503，中间层为绝缘层502，最下层是负极活性物质层501(石墨)。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图3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4，外包装可包括壳体51和盖板53。其中，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能够盖设于所述开口，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封装于所述容纳腔内。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，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，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一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图5是作为一个示例的电池模块4。参照图5，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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图6和图7是作为一个示例的电池包1。参照图6和图7，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能够盖设于下箱体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。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图8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二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
测定方法：
(1)循环性能测试
通过以下步骤对电池重复进行充电和放电，并计算电池的放电容量保持率。
首先，在25℃的环境中，进行第一次充电和放电，在0.33C(即3h内完全放掉理论容量的电流值)的充电电流下先进行恒流充电，然后进行恒压充电，直到上限电压为4.25V，然后在0.33C的放电电流下进行恒流放电，直到最终电压为2.8V，记录首次循环的放电容量。然后进行充电和放电循环，直到电池容量损失率达到20％(即，容量保 持率为80％)，记录此时的循环次数。
其中，根据公式：容量损失率＝((首次循环的放电容量-循环N次后的放电容量)/首次循环的放电容量)×100％，计算电池循环N次后的容量损失率。
(2)体积能量密度测定
通过小倍率(0.1-0.3C)充放电，测试电池的容量，通过下式计算出体积能量密度。
体积能量密度(Wh/L)＝容量(Ah)*平台电压(V)/电芯体积(L)
实施例1
1、二次电池的制备
1)正极极片的制备：
将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2、作为导电剂的超导电炭黑SP和作为粘结剂的聚偏氟乙烯(PVDF)按照质量比96:1.2:2.8分散在作为溶剂的N-甲基吡咯烷酮(NMP)中混合均匀，得到正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，经烘干、冷压、分条、裁片后，得到正极极片。
2)隔离膜的制备：
选用聚乙烯膜作为隔离膜。
3)负极极片的制备：
绝缘层的浆料制备：将勃姆石、聚乙烯醇分散剂、聚苯乙烯-丙烯酸酯乳液粘结剂按质量比为96.5:0.5:3分散在作为溶剂的去离子水中混合均匀。其中，勃姆石的颗粒粒径(即中值粒径Dv50)为0.3μm。
反应层的浆料制备：将氧化亚硅、聚乙烯醇分散剂、聚苯乙烯-丙烯酸酯乳液粘结剂按质量比为96.5:0.5:3分散在作为溶剂的去离子水中混合均匀。其中，氧化亚硅的颗粒粒径(即中值粒径)为1μm。
负极活性物质层的浆料制备：将负极活性材料人造石墨、作为导电剂的超导电炭黑、作为粘结剂的SBR和作为增稠剂的CMC-Na按照质量比96:1:1:2分散在作为溶剂的去离子水中混合均匀，得到负极浆料。
负极极片的制备：将负极活性物质层的浆料均匀涂覆在负极集流 体铜箔上，经烘干后，将绝缘层的浆料涂布在负极活性物质层上，绝缘层的厚度为2μm；经烘干后，将反应层的浆料涂布在绝缘层上，反应层的厚度为7μm，经烘干、冷压、分条、裁切后，得到负极极片。
4)电解液的制备
将碳酸亚乙酯(EC)、碳酸二甲酯(DMC)、碳酸二乙酯(DEC)按照按体积比1:1:1混合得到有机溶剂，接着将充分干燥的锂盐LiPF 6溶解于混合后的有机溶剂中，配制成浓度为1mol/L的电解液。
5)二次电池的制备：
将上述正极极片、隔离膜、负极极片按顺序层叠，使隔离膜处于正极极片与负极极片之间起到隔离作用，卷绕制备电芯，其中负极容量是正极容量的0.3倍；另外卷绕之后然后热压，进行电芯的制备；然后，将电芯置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，获得二次电池。
2、二次电池的性能测试
按照上述记载，测定所得到的二次电池的循环性能和体积能量密度。
实施例2～23
按照表1和表2所示改变反应条件，除此以外，与实施例1同样进行，制备二次电池。
其中，表1所示的实施例2～11通过改变负极容量B1，改变了B1/A1的值，而且其中反应层的厚度d也有改变。表2所示的实施例12、13改变了绝缘层材料的种类，实施例14、15改变了反应层材料的种类以及厚度，实施例16～18改变了绝缘层的厚度，实施例19～23改变了正极极片中单位面积的正极活性物质层的容量A1，此处是通过改变正极活性物质层的厚度来调整容量的，其中需要厚涂布，现有工艺难度大，A1值越大，涂布工艺要求越高，涂布太厚溶剂难挥发，膜片容易开裂。
比较例1～6
按照表3所示改变反应条件，除此以外，与实施例1同样进行，制备二次电池。
其中，比较例1～3的B1/A1的值大于1，不设置绝缘层和反应层的至少一者，比较例4～6的B1/A1的值小于1时，不设置绝缘层和反应层的至少一者。
[表1]
Figure PCTCN2021123995-appb-000003
[表2]
Figure PCTCN2021123995-appb-000004
[表3]
Figure PCTCN2021123995-appb-000005
根据上述结果可知，实施例在体积能量密度和循环寿命上均表现出了良好的效果。而相对于此，比较例并不能兼顾体积能量密度和循环寿命两者。具体而言，比较例1～3研究了在B1/A1的值大于1时，绝缘层和反应层的作用，比较例4和比较例5研究了在B1/A1的值小于1时，绝缘层和反应层的作用，通过与比较例1比较可知，比较例4在减小B1/A1的值时，能够提高体积能量密度，但是在没有设置绝缘层和反应层时，循环寿命极差。而从比较例5可知，仅设置绝缘层而不设置反应层时，循环寿命仍很差。从比较例6可知，仅设置反应层而不设置绝缘层时，循环寿命得到极大提高，但是循环寿命仍旧短于既设置反应层又设置绝缘层的实施例11。由此可知，通过在负极极片上设置反应层和绝缘层，能够具有大幅提高安全性的协同效果。
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 (13)

  1. 一种二次电池，包括正极极片和负极极片，
    所述负极极片包括负极集流体和负极活性物质层，所述负极活性物质层设置在所述负极集流体的至少一个表面上，
    所述负极活性物质层的与所述负极集流体侧相反一侧的表面依次设置有绝缘层和反应层，
    且所述反应层包括石墨、硅、氧化硅、氧化亚硅、氧化锡、氧化铜、氧化锌中的至少一种，
    所述正极极片中单位面积的正极活性物质层的容量记为A1(mAh/cm 2)，所述负极极片中单位面积的负极活性物质层的容量记为B1(mAh/cm 2)，则B1/A1＜1，可选为0.3≤B1/A1＜1。
  2. 根据权利要求1所述的二次电池，其中，
    所述绝缘层包含氧化铝、勃姆石、氧化锆、氧化钛、氧化镁、氧化钴、氧化镍、氧化镓、氧化锗、氧化钇、氧化锶、氧化钡、氧化钼中的至少一种。
  3. 根据权利要求1或2所述的二次电池，其中，
    所述电池满足：
    Figure PCTCN2021123995-appb-100001
    d：反应层的厚度，单位为μm；
    A1：正极极片的单位面积正极活性物质的容量，单位为mAh/cm 2；
    B1：负极极片的单位面积负极活性物质的容量，单位为mAh/cm 2；
    m1：反应层的克容量，单位为mAh/g；
    ρ：反应层的密度，单位为g/cm 3。
  4. 根据权利要求1-3中任一项所述的二次电池，其中，所述反应层的克容量m1满足m1≥150mAh/g；可选地，1000mAh/g≤m1≤2500mAh/g。
  5. 根据权利要求1-4中任一项所述的二次电池，其中，所述反应层的密度ρ满足0.2g/cm 3≤ρ≤3g/cm 3，可选为1g/cm 3≤ρ≤2g/cm 3。
  6. 根据权利要求1-5中任一项所述的二次电池，其中，
    所述反应层的厚度为1μm-30μm，可选为2μm-30μm；和/或，
    所述绝缘层的厚度为1μm-10μm，可选为2μm-4μm。
  7. 根据权利要求1-6中任一项所述的二次电池，其中，
    所述绝缘层的杨氏模量大于等于6GPa，可选为6GPa-30GPa。
  8. 根据权利要求1-7中任一项所述的二次电池，其中，
    所述反应层中材料的颗粒粒径为0.1μm-4μm，可选为0.1μm-0.8μm；和/或，
    所述绝缘层中材料的颗粒粒径为0.1μm-10μm，可选为0.1μm-4μm。
  9. 根据权利要求1-8中任一项所述的二次电池，其中，
    所述负极极片中单位面积的负极活性物质层的容量B1为0.3mAh/cm 2-7mAh/cm 2；可选为1mAh/cm 2-5mAh/cm 2。
  10. 根据权利要求1-9中任一项所述的二次电池，其中，
    所述正极极片中单位面积的正极活性物质层的容量A1为1mAh/cm 2-7mAh/cm 2；可选为2mAh/cm 2-5mAh/cm 2。
  11. 一种电池模块，其中，包括权利要求1-10中任一项所述的二次电池。
  12. 一种电池包，其中，包括权利要求11所述的电池模块。
  13. 一种用电装置，其中，包括选自权利要求1-10中任一项所述的二次电池、权利要求11所述的电池模块或权利要求12所述的电池包中的至少一种。
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