WO2023130204A1 - 二次电池、电池模块、电池包和用电装置 - Google Patents

二次电池、电池模块、电池包和用电装置 Download PDF

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Publication number
WO2023130204A1
WO2023130204A1 PCT/CN2022/070054 CN2022070054W WO2023130204A1 WO 2023130204 A1 WO2023130204 A1 WO 2023130204A1 CN 2022070054 W CN2022070054 W CN 2022070054W WO 2023130204 A1 WO2023130204 A1 WO 2023130204A1
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Prior art keywords
current collector
secondary battery
concave
positive electrode
recessed
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PCT/CN2022/070054
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English (en)
French (fr)
Inventor
张翠平
韩昌隆
吴则利
黄磊
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2022/070054 priority Critical patent/WO2023130204A1/zh
Priority to EP22879656.1A priority patent/EP4235874A4/en
Priority to CN202280027758.7A priority patent/CN117157782A/zh
Priority to US18/314,120 priority patent/US11831002B2/en
Publication of WO2023130204A1 publication Critical patent/WO2023130204A1/zh
Anticipated expiration legal-status Critical
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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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the field of secondary batteries, and more specifically relates to a secondary battery in which at least one current collector contains a recessed structure, a battery module containing the secondary battery, a battery pack containing the battery module, and a battery pack containing the An electrical device for secondary batteries, battery modules, or battery packs.
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active material after the battery is discharged and continue to be used.
  • the main secondary batteries on the market are nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead storage) batteries, lithium-ion batteries, polymer lithium-ion batteries, etc.
  • Lithium-ion batteries have been commercialized for about 30 years and were originally used in consumer electronics such as cameras, laptops, and mobile phones. As people pay more and more attention to environmental issues, it is becoming an increasingly urgent need to replace fossil energy with clean energy. At the same time, with the advancement of lithium-ion battery technology, lithium-ion batteries have rapidly entered the field of electric vehicles in recent years.
  • the battery cell is the core component of the lithium-ion battery, and its service life is the primary factor considered by consumers. Therefore, the development of batteries with long life is a common pursuit of people. Lithium-ion batteries with high power performance have clear advantages in vehicle acceleration and energy recovery. However, during the long-term charge-discharge cycle of lithium-ion batteries, the positive and negative active materials gradually fall off from the current collector, which seriously affects the life and power performance of the battery cell.
  • the inventors of the present application have invented a new type of electrode through extensive and in-depth research, which can not only slow down or even avoid the problem of electrode active material falling off during the long cycle process, avoid the damage of the protective film on the surface of the current collector, and improve the performance of the battery cell at the same time. Long life performance and power performance. Moreover, the weight of the electrode is reduced, the energy density of the battery cell is improved, and the amount of the electrode collector is reduced, thereby reducing the cost.
  • a secondary battery comprising a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte
  • the positive electrode contains a positive electrode current collector having two main surfaces
  • the negative electrode contains A negative electrode current collector having two major surfaces
  • at least one of the positive electrode current collector and the negative electrode current collector comprising at least one recessed structure extending from at least one of the major surfaces into the interior of the current collector, the recessed structure having a recessed depth h 1
  • the unit is micron
  • the electrolyte has a conductivity ⁇
  • the unit is Siemens/m, where ⁇ and h 1 satisfy the following relation in value: 8tanhh 1 +0.2h 1 ⁇ 10tanh(h 1 ) 2 + 2+0.1h 1 .
  • the relationship between the recessed depth h 1 of the recessed structure and the thickness h 2 of the current collector where the recessed structure is located is: Wherein the depth h 1 of the depression and the thickness h 2 of the current collector are expressed in the same unit.
  • the recessed structure has a recessed width W, and the relationship between the recessed width W and the recessed depth h 1 is: h 1 ⁇ W ⁇ 6h 1 , wherein the recessed width W is the relationship between the recessed structure and the recessed depth h 1 .
  • the linear distance between two points with the largest linear distance on the periphery of the cross section where the main surface of the current collector intersects the concave structure is located, wherein the concave width W and the concave depth h1 are expressed in the same unit.
  • the current collector is provided with an electrode active material, and the relationship between the particle diameter D90 of the electrode active material on the current collector and the recessed depth h1 and the recessed width W of the recessed structure on the current collector is: h 1 ⁇ D90 ⁇ W, wherein the particle diameter D90, the depression depth h 1 and the depression width W are expressed in the same unit.
  • the relationship between the recessed area A1 of the recessed structure and the surface area A2 of the current collector where the recessed structure is located is: Wherein the concave area A1 is the sum of the cross-sectional areas where all the concave structures on the current collector intersect with the main surface of the current collector, and the concave area A1 is the same as the surface area A2 of the current collector unit representation.
  • the minimum distance d between the region where the concave structures are distributed on the surface of the current collector and the edge of the current collector satisfies 1mm ⁇ d ⁇ 10mm.
  • the current collector is selected from aluminum foil and copper foil.
  • recessed structures on both main surfaces of the current collector there are recessed structures on both main surfaces of the current collector, and the recessed structures on the two main surfaces can be optionally arranged in dislocation.
  • the recess depth h 1 is between 0.9-9.0 ⁇ m, optionally between 1-8 ⁇ m, and optionally between 2-7 ⁇ m.
  • the positive electrode current collector includes a recessed structure extending from at least one major surface into the interior of the positive electrode current collector.
  • the positive electrode current collector includes recessed structures extending from the two main surfaces into the interior of the positive electrode current collector, wherein the recessed structures on the two main surfaces are optionally arranged in dislocation.
  • the secondary battery is a lithium ion battery
  • the electrolyte contains a lithium salt and an additive, wherein the lithium salt is selected from LiFSI, LiPF 6 , lithium trifluoromethanesulfonate, lithium tetrafluoroborate , lithium perchlorate, at least one of LiFSI and LiPF 6 may be selected.
  • the additive is at least one selected from the group consisting of:
  • a battery module including the above-mentioned secondary battery.
  • a battery pack which includes the above-mentioned battery module.
  • an electric device which includes at least one of the above-mentioned secondary battery, battery module, and battery pack.
  • FIG. 1 is a cross-sectional view of a current collector having a concave structure according to an embodiment of the present application.
  • FIG. 2 is a top view of the current collector shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 4 is an exploded view of the secondary battery shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of a battery module of the present application.
  • Fig. 6 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 7 is an exploded view of the battery pack shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of an embodiment of a device using the secondary battery of the present application as a power source.
  • 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 herein mean an open type or a closed type.
  • 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.
  • 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 application provides a secondary battery comprising a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode contains a positive electrode current collector with two main surfaces, and the negative electrode contains a positive electrode collector with two main surfaces.
  • the negative electrode current collector of the main surface, at least one of the positive electrode current collector and the negative electrode current collector includes at least one recessed structure extending from at least one of the main surfaces into the interior of the current collector.
  • the inventors believe that during coating, the bottom of the active material particles is embedded in the concave structure, and after drying, the particles form a certain occlusal force with the pits of the concave structure, which can largely relieve or Avoiding the shedding of active particles in the middle and late stages of the cycle, and avoiding the comprehensive effect of the destruction of the passivation film on the surface of the current collector caused by the extrusion of the active material particles on the current collector during the cold pressing process, can improve the long-life performance of the battery cell.
  • the present application provides a secondary battery comprising a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte
  • the positive electrode includes a positive electrode current collector having two main surfaces
  • the negative electrode comprises a negative electrode current collector having two major surfaces
  • at least one of the positive electrode current collector and the negative electrode current collector comprises at least one recessed structure extending from at least one of the major surfaces into the interior of the current collector, the recessed structure having Depression h 1
  • the unit is micron
  • the electrolyte has a conductivity ⁇
  • the unit is Siemens/m, where ⁇ and h 1 satisfy the following relation in value: 8tanhh 1 +0.2h 1 ⁇ 10tanh(h 1 ) 2 +2+0.1h 1 .
  • the conductivity of the electrolyte can be measured in accordance with relevant standards, such as HG-T 4067-2015.
  • relevant standards such as HG-T 4067-2015.
  • the inventors believe that after the active material enters the interior of the concave structure, the transmission path of lithium ions is longer than that without the concave structure, so a faster lithium ion transmission speed is required.
  • the depth of the concave structure and the electrical conductivity satisfy the above relationship, lithium ions can be quickly conducted into the active material in the concave structure, avoiding the generation of internal polarization of the particles.
  • tanh is the hyperbolic tangent function symbol
  • any one or both of the positive electrode current collector and the negative electrode current collector may contain a concave structure, specifically, any one or both main surfaces of the positive electrode current collector and/or the negative electrode current collector may contain a concave structure.
  • a current collector having a recessed structure is described below.
  • “current collector” may refer to a positive electrode current collector and/or a negative electrode current collector, and the two main surfaces of the current collector may be referred to as the first main surface and the second main surface.
  • the current collector can be selected from aluminum foil and copper foil, usually aluminum foil is used as the positive electrode current collector, and copper foil is used as the negative electrode current collector.
  • major surface may refer to a first major surface and/or a second major surface. In some embodiments, the first major surface can be substantially parallel to the second major surface.
  • electrode may refer to a positive electrode and/or a negative electrode unless otherwise specified. It should be understood that when both the current collector and the recessed structure are mentioned in the following description, the recessed structure refers to the recessed structure on the current collector.
  • the shape of the cross-section of the recessed structure extending from the main surface into the interior of the current collector is not particularly limited.
  • the cross section refers to a section parallel to the main surface of the current collector.
  • the cross section where the concave structure intersects with the main surface of the current collector can be circular, elliptical, semicircular, triangular, square, rectangular, trapezoidal, star-shaped, polygonal, and irregular.
  • the shape of the longitudinal section perpendicular to the cross section of the concave structure is not particularly limited, for example, it may be rectangular, triangular, trapezoidal, arcuate and irregular.
  • the recessed structure is cylindrical.
  • the recessed structure is cone-shaped.
  • the recessed structures are prism-shaped.
  • the recessed structures are hemispherical.
  • the recessed structure extending from the main surface into the interior of the current collector has a recessed depth h 1 , and the possible relationship between the recessed depth h 1 and the thickness h 2 of the current collector is:
  • the recess depth h 1 and the current collector thickness h 2 are represented by the same unit.
  • the depression depth refers to the maximum distance from the main surface of the current collector to the bottom of the depression structure.
  • the concave depth is the distance from the main surface of the current collector to the bottom surface of the cylinder.
  • the concave depth is the distance from the apex of the cone to the main surface of the current collector.
  • the recess depth h 1 is in the range of 0.9-9.0 ⁇ m, optionally between 1-8 ⁇ m, and optionally between 2-7 ⁇ m.
  • the recess depth h 1 includes but is not limited to 0.9 ⁇ m, 1.0 ⁇ m, 1.2 ⁇ m, 1.4 ⁇ m, 1.6 ⁇ m, 1.8 ⁇ m, 2.0 ⁇ m, 2.2 ⁇ m, 2.4 ⁇ m, 2.6 ⁇ m, 2.8 ⁇ m, 3.0 ⁇ m, 3.2 ⁇ m, 3.4 ⁇ m ⁇ m, 3.6 ⁇ m, 3.8 ⁇ m, 4.0 ⁇ m, 4.2 ⁇ m, 4.4 ⁇ m, 4.6 ⁇ m, 4.8 ⁇ m, 5.0 ⁇ m, 5.2 ⁇ m, 5.4 ⁇ m, 5.6 ⁇ m, 5.8 ⁇ m, 6.0 ⁇ m, 6.2 ⁇ m, 6.4 ⁇ m, 6.6 ⁇ m, 6.8 ⁇ m, 7.0 ⁇ m, 7.2 ⁇ m, 7.4 ⁇ m, 7.6 ⁇ m, 7.8 ⁇ m, 8.0 ⁇ m, 8.2 ⁇ m, 8.4 ⁇ m, 8.6 ⁇ m, 8.8 ⁇ m, 9.0 ⁇ m and
  • the current collector thickness h2 is in the range of 9.0-18.0 ⁇ m, including but not limited to 9.5 ⁇ m, 10.0 ⁇ m, 10.5 ⁇ m, 11.0 ⁇ m, 11.5 ⁇ m, 12.0 ⁇ m, 12.5 ⁇ m, 13.0 ⁇ m, 13.5 ⁇ m , 14.0 ⁇ m, 14.5 ⁇ m, 15.0 ⁇ m, 15.5 ⁇ m, 16.0 ⁇ m, 16.5 ⁇ m, 17.0 ⁇ m, 17.5 ⁇ m and the range formed by any two of the above-mentioned endpoints.
  • the depth h1 of the depression and the thickness h2 of the current collector can be measured by methods known in the art, for example, the profile analysis of the current collector can be carried out according to JY/T010-1996, and can be measured online.
  • the inventors have found that when the depth h1 of the above-mentioned concave structure and the thickness h2 of the current collector satisfy the above-mentioned relationship, the adhesion (occlusal force) between the current collector and the active material is the largest, which can effectively inhibit the shedding of the active material during long-term cycling. .
  • the recessed structure has a recessed width W
  • the relationship between the recessed width W and the recessed depth h 1 may be: h 1 ⁇ W ⁇ 6h 1 , wherein the recessed width W is the relationship between the recessed structure and the recessed depth h 1 .
  • the width W of the recess is the diagonal length of the rectangle; when the cross-section of the recessed structure and the main surface of the current collector is circular, the width of the recess is W is the diameter of the circle; when the cross-section where the concave structure intersects the main surface of the current collector is a triangle, the width W of the depression is the length of the longest side of the triangle.
  • the recess width W can be h 1 , 1.5h 1 , 2.0h 1 , 2.5h 1 , 3.0h 1 , 3.5h 1 , 4.0h 1 , 4.5h 1 , 5.0h 1 , 5.5h 1 , 6h 1 and the range formed by the endpoints of any two of the above values.
  • the recess width W is in the range of 0.9-54.0 ⁇ m, including but not limited to 1.0 ⁇ m, 1.5 ⁇ m, 2.0 ⁇ m, 2.5 ⁇ m, 3.0 ⁇ m, 3.5 ⁇ m, 4.0 ⁇ m, 4.5 ⁇ m, 5.0 ⁇ m, 5.5 ⁇ m ⁇ m, 6.0 ⁇ m, 6.5 ⁇ m, 7.0 ⁇ m, 7.5 ⁇ m, 8.0 ⁇ m, 8.5 ⁇ m, 9.0 ⁇ m, 9.5 ⁇ m, 10.0 ⁇ m, 12.0 ⁇ m, 14.0 ⁇ m, 16.0 ⁇ m, 18.0 ⁇ m, 20.0 ⁇ m, 22.0 ⁇ m, 24.0 ⁇ m, 26.0 ⁇ m, 28.0 ⁇ m, 30.0 ⁇ m, 32.0 ⁇ m, 34.0 ⁇ m, 36.0 ⁇ m, 38.0 ⁇ m, 40.0 ⁇ m, 42.0 ⁇ m, 44.0 ⁇ m, 46.0 ⁇ m, 48.0 ⁇ m, 50.0 ⁇ m, 52.0 ⁇ m and any two values above as the endpoint range of composition.
  • the depression width W can be analyzed on-line according to JY/T010-1996 for surface morphology analysis.
  • the inventors found that when the width and depth of the concave structure satisfy the above relationship, the active material particles have good effective contact with the current collector, which can quickly conduct electrons, reduce the polarization of the pole piece, and improve the battery life.
  • the electrode further includes an electrode active material on the current collector.
  • the electrode active material is on the first major surface and/or the second major surface of the current collector. It can be understood that the positive electrode active material is provided on the first main surface and/or the second main surface of the positive electrode current collector, and the negative electrode active material is provided on the first main surface and/or the second main surface of the negative electrode current collector.
  • the relationship between the particle diameter D90 of the electrode active material and the recess depth h 1 and the recess width W may be: h 1 ⁇ D90 ⁇ W, wherein the particle diameter D90, the recess depth h 1 and The recess width W is expressed in the same unit.
  • the particle size D90 of the electrode active material is in the range of 0.9-54.0 ⁇ m, including but not limited to 1.0 ⁇ m, 1.5 ⁇ m, 2.0 ⁇ m, 2.5 ⁇ m, 3.0 ⁇ m, 3.5 ⁇ m, 4.0 ⁇ m, 4.5 ⁇ m, 5.0 ⁇ m, 5.5 ⁇ m, 6.0 ⁇ m, 6.5 ⁇ m, 7.0 ⁇ m, 7.5 ⁇ m, 8.0 ⁇ m, 8.5 ⁇ m, 9.0 ⁇ m, 9.5 ⁇ m, 10.0 ⁇ m, 12.0 ⁇ m, 14.0 ⁇ m, 16.0 ⁇ m, 18.0 ⁇ m, 20.0 ⁇ m, 22.0 ⁇ m , 24.0 ⁇ m, 26.0 ⁇ m, 28.0 ⁇ m, 30.0 ⁇ m, 32.0 ⁇ m, 34.0 ⁇ m, 3
  • D90 can be measured according to GB/T19077-2016.
  • the inventors found that when the particle size D90 of the electrode active material satisfies the above relationship with the recess depth h1 and the recess width W, there is matching between the recessed structure and the positive electrode material particles, ensuring that the benefits of the recessed structure can be fully utilized.
  • the relationship between the recessed area A1 and the current collector surface area A2 can be:
  • the recessed area A1 is the sum of the cross-sectional areas of all recessed structures intersecting the main surface of the current collector, and the recessed area A1 and the current collector surface area A2 are expressed in the same unit.
  • the units of the recessed area A1 and the current collector surface area A2 are centimeters.
  • the minimum distance d between the region where the concave structures are distributed on the surface of the current collector and the edge of the current collector may be in the following range: 1mm ⁇ d ⁇ 10mm.
  • the minimum distance between the area with concave structures distributed on the surface of the current collector and the edge of the current collector can be determined as follows: observe the cross-section where all the concave structures adjacent to the edge of the current collector intersect with the main surface of the current collector, and find out the distance between the edge of the cross-section and the edge of the current collector. The point closest to the edge of the fluid, the shortest distance between this point and the edge of the current collector is the above minimum distance d. d can be measured by methods known in the art, such as with a scale.
  • d includes, but is not limited to, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm and a range formed by endpoints of any two of the above values.
  • FIG. 1 shows a cross-sectional view of an exemplary current collector according to an embodiment of the present application, which shows a schematic diagram of a concave structure of the current collector.
  • FIG. 2 shows a top view of the current collector showing an exemplary shape and distribution of the recessed structures. It should be understood that the concave structure of the current collector is not limited to the illustrated situation.
  • recessed structures exist on both the first major surface and the second major surface of the current collector.
  • the recessed structures on the first main surface and the recessed structures on the second main surface may be arranged in dislocation.
  • the so-called "dislocation arrangement" means that if there is a concave structure at a certain position on the first main surface, there is no concave structure at the opposite position on the second main surface; and vice versa. This arrangement can effectively prevent the concave structures of the first main surface and the second main surface from being at the same position on both sides of the current collector, thereby avoiding the phenomenon that the current collector is too thin or even the current collector is perforated.
  • the electrode may be a positive electrode or a negative electrode.
  • the electrode is an anode.
  • the aforementioned electrodes may be positive and/or negative electrodes of secondary batteries, such as positive and/or negative electrodes of lithium ion batteries.
  • the above-mentioned electrodes are not limited to the electrodes of the secondary battery; all electrodes in which the above-mentioned improvements are made to the current collector of the electrode according to the present application fall within the scope of the present application.
  • the present application also provides a method for preparing the above electrode, the method comprising:
  • a current collector comprising a first major surface and a second major surface
  • At least one of the first and second main surfaces is formed with at least one recessed structure as described above extending into the interior of the current collector.
  • the recessed structure is formed by physical or chemical methods. In some embodiments, the recessed structure is formed by chemical etching. For example, a current collector with a thickness of 10-50 ⁇ m can be used, and a DC etching process is adopted on the surface of the current collector, the current is 0.1-1.0A, the energization time is 0.05-3.0s, and the energization frequency is at least once.
  • the secondary battery according to the present application may be a lithium ion battery, a potassium ion battery, a sodium ion battery, a lithium sulfur battery, or the like.
  • the secondary battery is a lithium ion battery, wherein the electrolyte contains a lithium salt and an additive, wherein the lithium salt is selected from LiFSI, LiPF 6 , lithium trifluoromethanesulfonate, lithium tetrafluoroborate, At least one in lithium perchlorate, can be at least one in LiFSI, LiPF 6 ; Described additive is selected from at least one in the following group:
  • the electrolyte containing the above-mentioned lithium salts and additives has a high conductivity, and an interface film with high stability and low impedance is preferentially formed at the cathode-anode interface during the formation capacity process. These characteristics are conducive to improving the cycle life and power performance of the battery cell. .
  • the present application also provides a method for preparing the above-mentioned secondary battery, which includes:
  • a positive electrode and a negative electrode are provided, the positive electrode includes a positive electrode collector having two major surfaces, the negative electrode includes a negative electrode collector having two major surfaces, at least one of the positive electrode collector and the negative electrode collector includes at least one recessed structure extending from at least one major surface into the interior of the current collector, said recessed structure having a recessed depth h 1 ,
  • the bare cell is placed in the outer package, and the electrolyte is injected into the outer package, and the electrolyte has a conductivity ⁇ ,
  • ⁇ and h 1 satisfy the following relationship numerically: 8tanhh 1 +0.2h 1 ⁇ 10tanh(h 1 )2+2+0.1h 1 , where the unit of the depression depth h1 is in microns, and the conductivity of the electrolyte ⁇ is The unit is Siemens/meter.
  • a negative electrode film layer is arranged on the negative electrode current collector, and the negative electrode film layer contains negative electrode active materials, such as natural graphite, artificial graphite, soft carbon, hard carbon, silicon current collector material, tin collector One or more of fluid material and lithium titanate.
  • the silicon current collector material can be selected from one or more of elemental silicon, silicon oxide, and silicon-carbon composites.
  • the tin current collector material can be selected from one or more of simple tin, tin oxide, and tin alloys.
  • Described negative electrode film layer comprises negative electrode active material and optional binding agent, optional conductive agent and other optional additives, is usually formed by coating and drying negative electrode slurry.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring them evenly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • carbon black such as acetylene black, ketjen black
  • carbon dots carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA) , sodium alginate (SA) and carboxymethyl chitosan (CMCS) in one or more.
  • the binder may include one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS) or several.
  • Other optional additives are, for example, thickeners (such as sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.
  • the negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer.
  • the negative electrode sheet of the present application can also include a conductive undercoat layer (for example, composed of a conductive agent and a binder) that is sandwiched between the negative electrode current collector and the negative electrode film layer and arranged on the surface of the negative electrode current collector. ).
  • the negative electrode sheet of the present application may further include a covering protective layer covering the surface of the negative electrode film layer.
  • a positive electrode film layer is provided on the positive electrode current collector, and the positive electrode film layer contains a positive electrode active material.
  • the positive electrode active material can be selected from LiNi 0.5-a Mn 1.5 M a O 4 (0 ⁇ a ⁇ 0.1), LiNi x Co y N z M 1-xyz O 2 , wherein N is selected from Mn and Al, and M is selected from Co, Any one of Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, x +y+z ⁇ 1.
  • Examples 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 oxides, 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 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and one or more of its modified compounds.
  • lithium cobalt oxides such as LiCoO 2
  • lithium nickel oxides such as LiNi
  • the positive film layer also optionally includes a binder.
  • the non-limiting example that can be used for the binding agent of anode membrane layer can include following one or more: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene meta-copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may further optionally contain a conductive agent.
  • the positive electrode can be prepared in the following manner: the above-mentioned components for preparing the positive electrode, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N- Methylpyrrolidone) to form a uniform 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 separator separates the anode side of the secondary battery from the cathode side, and provides selective permeation or barrier to substances of different types, sizes and charges in the system.
  • the separator can be electronically insulated, and the The positive and negative active materials of the secondary battery are physically separated to prevent internal short circuit and form an electric field in a certain direction, and at the same time enable the ions in the battery to move between the positive and negative electrodes through the separator.
  • the material used to prepare the separator may include one or more of glass fibers, non-woven fabrics, polyethylene, polypropylene and polyvinylidene fluoride.
  • the diaphragm 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 electrolyte may be selected from at least one of solid electrolyte and liquid electrolyte (ie, electrolyte).
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (difluorosulfonate Lithium imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO 2 F 2 One or more of (lithium difluorophosphate), LiDFOP (lithium difluorooxalatephosphate) and LiTFOP (lithium tetrafluorooxalatephosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the solvent can be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), Dimethyl Carbonate (DMC), Dipropyl Carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl 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 (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and two E
  • the content of the solvent is 60-99% by weight, such as 65-95% by weight, or 70-90% by weight, or 75- 89% by weight, or 80-85% by weight. In one embodiment of the present application, based on the total weight of the electrolyte, the content of the electrolyte is 1-40% by weight, such as 5-35% by weight, or 10-30% by weight, or 11- 25% by weight, or 15-20% by weight.
  • the electrolyte may optionally contain additives.
  • additives can include one or more of the following: 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 battery high-temperature performance, Additives to improve low-temperature performance of batteries, etc.
  • the above-mentioned positive electrode, negative electrode and separator can be made into an electrode assembly/bare cell by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to package the above-mentioned electrode assembly and electrolyte/electrolytic solution.
  • 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 package of the secondary battery may be a soft bag, such as a pouch-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. 3 shows a secondary battery 5 having a square structure as an example.
  • FIG. 4 shows an exploded view of the secondary battery 5 of FIG. 3, the outer package may include a housing 51 and a cover plate 53, the housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and the side plates Enclosed to form an accommodation chamber.
  • 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 form the electrode assembly 52 through a winding process or a lamination process.
  • the number of electrode assemblies 52 included in the secondary battery 5 may be one or more.
  • 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.
  • two or more of the above-mentioned battery modules can be assembled into a battery pack, and the number of battery modules contained in the battery pack depends on the application of the battery pack and the parameters of a single battery module.
  • the battery pack can include a battery box and a plurality of battery modules arranged in the battery box.
  • the battery box includes an upper box and a lower box.
  • the upper box can be covered on the lower box and well matched with it to form a battery for accommodating The enclosed space of the module.
  • Two or more battery modules can be arranged in the battery box in a desired manner.
  • 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.
  • the electric device of the present application includes at least one of the secondary battery, battery module or battery pack of the present application, and the secondary battery, battery module or battery pack can be used as the A power source for an electrical device may also be used as an energy storage unit for said electrical device.
  • the electrical devices include but are not limited to mobile digital 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 golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • Figure 8 is an example device.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • battery packs or battery modules can be employed.
  • 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 present application arranges the concave structure on the electrode current collector and properly sets the particle size of the concave structure and/or the electrode active material arranged on the current collector, or properly sets the conductivity of the concave structure and the electrolyte, unexpectedly Greatly improve the battery cycle life and battery performance.
  • the active material particles have good effective contact with the current collector, which can quickly conduct electrons, reduce the polarization of the pole piece, and improve the life of the battery cell;
  • Embodiment 1-25 and comparative example 1 are identical to Embodiment 1-25 and comparative example 1
  • the cross-section is half of Circular concave structure.
  • the aluminum foil used had a thickness (h 2 ) of 18 ⁇ m and a width of 80 mm.
  • d represents the minimum distance between the area with concave structures distributed on the surface of the aluminum foil and the edge of the aluminum foil, measured with a scale;
  • a 1 represents the area of the depression,
  • a 2 represents the surface area of the aluminum foil;
  • h 1 represents the depth of the depression, and
  • h 2 represents the thickness of the aluminum foil , they conduct current collector profile analysis according to JY/T010-1996, and measure online;
  • W represents the width of the sag, conduct surface morphology analysis according to JY/T010-1996, and measure online;
  • D90 represents the D90 particle size of electrode active material particles, according to GB /T19077-2016 measurement;
  • ⁇ indicates that double-sided dislocation etching is used, and
  • ⁇ indicates that double-sided dislocation etching is not used.
  • a copper foil with a thickness of 18 ⁇ m and a width of 80 mm was used as the negative electrode current collector.
  • the cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the conductive agent Super P carbon black, and the binder polyvinylidene fluoride (PVDF) were prepared into a cathode slurry in N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • the solid content in the positive electrode slurry is 50 wt%, and the mass ratio of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , Super P, and PVDF in the solid component is 8:1:1.
  • Graphite as the negative electrode active material, conductive agent Super P carbon black, thickener carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were evenly mixed in deionized water to make negative electrode slurry.
  • the solid content in the negative electrode slurry is 30wt%, and the mass ratio of graphite, Super P, CMC and SBR in the solid component is 80:15:3:2.
  • the negative electrode slurry was coated on the current collector copper foil and dried at 85°C, then cold pressed, edge trimmed, cut into pieces, and stripped, and then dried under vacuum at 120°C for 12 hours to make negative electrode sheets.
  • a 16 ⁇ m polyethylene film (PE) was used as the separator.
  • PE polyethylene film
  • Embodiment 26-29 and comparative example 2 are identical to Embodiment 26-29 and comparative example 2
  • the electrolyte and the aluminum foil positive electrode collector with a concave structure were prepared according to the method described in the above "Example 1-25 and Comparative Example 1", the difference is that the conductivity ⁇ of the electrolyte and the depth h1 of the concave structure are as follows 3.
  • the preparation method of positive electrode sheet, negative electrode sheet and lithium-ion battery is the same as the method described in the "Example 1-25 and Comparative Example 1" section, and the cycle performance and power performance of the lithium-ion battery are tested in the same way, and the results are shown in the table 4.
  • the conductivity of the electrolyte can be determined by adjusting the type and content of the solvent and lithium salt. See Table 5 for details.
  • the conductivity of the electrolyte is measured according to HG-T 4067-2015.
  • the depth h 1 of the depressed structure on the aluminum foil and the conductivity ⁇ of the electrolyte satisfy 8tanhh 1 +0.2h 1 ⁇ 10tanh(h 1 ) 2 +2+0.1h 1 .
  • the results show that when the depth h 1 of the concave structure on the current collector and the conductivity ⁇ of the electrolyte satisfy the above relationship, the cycle performance and power performance of the lithium-ion battery are significantly improved, thereby improving the cycle life and overall performance of the battery.
  • the electrode active material particles are partially embedded in the concave structure of the current collector, it is not conducive to the rapid infiltration of the electrolyte, that is, it is not conducive to the migration of lithium ions in the solid phase, and the adjustment of the electrolyte's
  • the electrical conductivity (adjusting the transmission speed of lithium ions in the electrolyte) is beneficial to make up for the problems caused by the above-mentioned concave structure.

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Abstract

本申请提供了一种二次电池，其包含正极，负极，位于正极和负极之间的隔膜，以及电解液，其中正极包含具有两个主表面的正极集流体，负极包含具有两个主表面的负极集流体，所述正极集流体和所述负极集流体中的至少一者包含从至少一个主表面延伸进入集流体内部的至少一个凹陷结构，所述凹陷结构具有凹陷深度h 1，单位为微米，所述电解液具有电导率σ，单位为西门子/米，其中σ与h 1在数值上满足以下关系：8tanhh 1+0.2h 1≤σ≤10tanh(h 1) 2+2+0.1h 1。本申请还提供了包含上述二次电池的电池模块、电池包和用电装置。所述二次电池具有提高的循环性能和功率性能。

Description

二次电池、电池模块、电池包和用电装置 技术领域
本申请属于二次电池领域，更具体地涉及一种其至少一个集流体包含凹陷结构的二次电池，包含所述二次电池的电池模块，包含所述电池模块的电池包，以及包含所述二次电池、电池模块或电池包的用电装置。
背景技术
二次电池又称充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性物质激活而继续使用的电池。市场上主要的二次电池有镍氢电池、镍镉电池、铅酸(或铅蓄)电池、锂离子电池、聚合物锂离子电池等。
锂离子电池的商业化已有大约30年的时间，原来主要应用于消费电子产品，如照相机、笔记本电脑、移动电话等。随着人们对环境问题的日益关注，用清洁能源代替化石能源正在成为日益迫切的需求，同时随着锂离子电池技术的进步，近年来，锂离子电池迅速进入电动汽车领域。
电芯是锂离子电池的核心部件，其使用寿命是消费者考虑的首要因素。因此，开发具有长寿命电芯是人们的普遍追求。具有高功率性能的锂离子电池在汽车加速过程以及能量回收方面具有明显优势。但是，锂离子电池在长期充放电循环过程中，正负极活性材料逐渐从集流体上脱落，严重影响电芯的寿命和功率性能。
发明内容
本申请的发明人通过广泛而深入的研究，发明了一种新型电极，不仅能够减缓甚至避免长循环过程中电极活性材料脱落的问题，避免集流体表面的保护膜被破坏，同时改善电芯的长寿命性能和功率性能。而且，电极的重量得到减轻，电芯能量密度得到提高，电极集流体的用量减少，从而降低了成本。
根据本申请的第一方面，提供了一种二次电池，其包含正极，负极，位于正极和负极之间的隔膜，以及电解液，其中正极包含具有两个主表面的正极集流体，负极包含具有两个主表面的负极集流体，所述正极集流体和所述负极集流体中的至少一者包含从至少一个主表面延伸进入集流体内部的至少一个凹陷结构，所述凹陷结构具有凹陷深度h 1，单位为微米，所述电解液具有电导率σ，单位为西门子/米，其中σ与h 1在数值上满足以下关系：8tanhh 1+0.2h 1≤σ≤10tanh(h 1) 2+2+0.1h 1。
在一些实施方式中，所述凹陷结构的凹陷深度h 1与所述凹陷结构所在的集流体的厚度h 2之间的关系为：
Figure PCTCN2022070054-appb-000001
其中所述凹陷深度h 1和所述集流体的厚度h 2以相同的单位表示。
在一些实施方式中，所述凹陷结构具有凹陷宽度W，所述凹陷宽度W与凹陷深度h 1的关系为：h 1≤W≤6h 1，其中所述凹陷宽度W是所述凹陷结构与所述凹陷结构所在的集流体的主表面相交的横截面的周缘上具有最大直线距离的两点之间的直线距离，其中所述凹陷宽度W与所述凹陷深度h 1以相同的单位表示。
在一些实施方式中，集流体上设置有电极活性材料，集流体上的电极活性材料的粒径D90与该集流体上的凹陷结构的凹陷深度h 1和凹陷宽度W之间的关系为：h 1≤D90≤W，其中所述粒径D90、所述凹陷深度h 1和所述凹陷宽度W以相同的单位表示。
在一些实施方式中，所述凹陷结构的凹陷面积A 1与所述凹陷结构所在的集流体的表面面积A 2的关系为：
Figure PCTCN2022070054-appb-000002
其中所述凹陷面积A 1为该集流体上所有的凹陷结构与该集流体的主表面相交的横截面的面积之和，所述凹陷面积A 1与该集流体的表面面积A 2以相同的单位表示。
在一些实施方式中，集流体表面上分布有凹陷结构的区域与该集流体边缘的最小距离d满足1mm≤d≤10mm。
在一些实施方式中，所述集流体选自铝箔和铜箔。
在一些实施方式中，集流体的两个主表面上都存在凹陷结构，两个主表面上的凹陷结构可选错位设置。
在一些实施方式中，所述凹陷深度h 1在0.9-9.0μm之间，可选在1-8μm之间，可选在2-7μm之间。
在一些实施方式中，所述正极集流体包含从至少一个主表面延伸进入正极集流体内部的凹陷结构。
在一些实施方式中，所述正极集流体包含从两个主表面延伸进入正极集流体内部的凹陷结构，其中所述两个主表面上的凹陷结构可选错位设置。
在一些实施方式中，所述二次电池是锂离子电池，所述电解液包含锂盐和添加剂，其中所述锂盐选自LiFSI、LiPF 6、三氟甲基磺酸锂、四氟硼酸锂、高氯酸锂中的至少一种，可选为LiFSI、LiPF 6中的至少一种。
在一些实施方式中，所述添加剂选自下组中的至少一种：
Figure PCTCN2022070054-appb-000003
根据本申请的第二方面，提供了一种电池模块，其包括上述二次电池。
根据本申请的第三方面，提供了一种电池包，其包括上述电池模块。
根据本申请的第四方面，提供了一种用电装置，其包括上述二次电池、电池模块和电池包中的至少一种。
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，下面所描述的本申请实施例中的附图仅仅是示例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是根据本申请的一个实施方式的具有凹陷结构的集流体的剖面图。
图2是图1所示集流体的俯视图。
图3是本申请二次电池的一实施方式的示意图。
图4是图3所示二次电池的分解图。
图5是本申请电池模块的一实施方式的示意图。
图6是本申请电池包的一实施方式的示意图。
图7是图6所示电池包的分解图。
图8是使用本申请的二次电池用作电源的装置的一实施方式的示意图。
具体实施方式
下面对本申请的实施方式作进一步详细描述。以下详细描述用于示例性地说明本申请的原理，但不能用来限制本申请的范围，即本申请不限于所描述的实施方式。
本文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。
在本申请中，如果没有特别的说明，本文所提到的所有实施方式以及优选实施方式可以相互组合形成新的技术方案。
在本申请中，如果没有特别的说明，本文所提到的所有技术特征以及优选特征可以相互组合形成新的技术方案。
在本申请中，如果没有特别的说明，本文所提到的所有步骤可以顺序进行，也可以随机进行，但是优选是顺序进行的。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。
在本申请中，如果没有特别的说明，本文所提到的“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。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种及两种以上。在本文的描述中，术语“第一”、“第二”、“第三”等仅用于描述目的，而不能理解为指示或暗示相对重要性。
在本文的描述中，除非另有说明，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)。
二次电池
锂离子电池在长期充放电循环过程中，正负极活性材料逐渐从集流体上脱落，严重影响电芯的寿命和功率性能。另外，新鲜集流体(铜箔、铝箔)在接触空气后，表面都会形成一层氧化物保护层，但是电芯在制作过程中的冷压步骤中，电极活性材料颗粒在压力的作用下会被部分压进集流体里面(这种情况对正极尤为显著)，破坏了集流体表面的氧化物保护层，在高温乃至长循环过程中，集流体慢慢被腐蚀，造成极片断裂，不仅严重影响电芯性能，而且可能导致电芯产生安全问题。
为此，本申请提供了一种二次电池，其包含正极，负极，位于正极和负极之间的隔膜，以及电解液，其中正极包含具有两个主表面的正极集流体，负极包含具有两个主表面的负极集流体，所述正极集流体和所述负极集流体中的至 少一者包含从至少一个主表面延伸进入集流体内部的至少一个凹陷结构。
不受限于任何特定理论，发明人认为，在涂布时，活性材料颗粒底部嵌入凹陷结构内部，干燥后，颗粒与凹陷结构的凹坑形成一定的咬合力，在很大程度上可以缓解或者避免循环中后期活性颗粒的脱落，另外，避免在冷压过程中，活性材料颗粒挤压集流体而造成集流体表面钝化膜的破坏的综合效果，可以改善电芯长寿命性能。
根据本申请的一些实施方式，本申请提供了一种二次电池，其包含正极，负极，位于正极和负极之间的隔膜，以及电解液，其中正极包含具有两个主表面的正极集流体，负极包含具有两个主表面的负极集流体，所述正极集流体和所述负极集流体中的至少一者包含从至少一个主表面延伸进入集流体内部的至少一个凹陷结构，所述凹陷结构具有凹陷深度h 1，单位为微米，所述电解液具有电导率σ，单位为西门子/米，其中σ与h 1在数值上满足以下关系：8tanhh 1+0.2h 1≤σ≤10tanh(h 1) 2+2+0.1h 1。
电解质的电导率可按照相关标准测量，例如HG-T 4067-2015。不受限于任何特定理论，发明人认为，活性材料进入凹陷结构内部后，锂离子的传输路径相对于没有凹陷结构的情况更长，因而需要更快的锂离子传输速度。当凹陷结构深度与电导率满足上述关系式时，锂离子能快速传导到凹陷结构内的活性材料里，避免了颗粒内部极化的产生。
在上式中，tanh是双曲线正切函数符号，
Figure PCTCN2022070054-appb-000004
如上所述，正极集流体和负极集流体中的任意一者或两者可包含凹陷结构，具体是正极集流体和/或负极集流体的任意一个或两个主表面可包含凹陷结构。以下描述具有凹陷结构的集流体。为方便描述，在本文中，在未具体指明的情况下，“集流体”可指正极集流体和/或负极集流体，集流体的两个主表面可称为第一主表面和第二主表面，集流体可选自铝箔和铜箔，通常铝箔用作正极集流体，铜箔用作负极集流体。在未具体指明的情况下，“主表面”可指第一主表面和/或第二主表面。在一些实施方式中，所述第一主表面可大致平行于所述第二主表面。在未具体指明的情况下，“电极”可指正极和/或负极。应当理解，在以下描述中同时提到集流体和凹陷结构时，该凹陷结构是指位于在该集流体上的凹陷结构。
从主表面延伸进入集流体内部的凹陷结构的横截面的形状不受特别限制。所述横截面是指与集流体主表面平行的截面。例如，凹陷结构与集流体主表面相交的横截面可以为圆形、椭圆形、半圆形、三角形、正方形、长方形、梯形、星形、多边形以及不规则形状等。凹陷结构的与其横截面垂直的纵截面的形状不受特别限制，例如，可以为矩形、三角形、梯形、弓形以及不规则形状等。在一些实施方式中，凹陷结构为圆柱体形。在一些实施方式中，凹陷结构为圆锥体形。在一些实施方式中，凹陷结构为棱柱体形。在一些实施方式中，凹陷结构为半球形。
在一些实施方式中，从主表面延伸进入集流体内部的凹陷结构具有凹陷深度h 1，所述凹陷深度h 1与集流体厚度h 2之间的可以关系为：
Figure PCTCN2022070054-appb-000005
其中所述凹陷深度h 1和所述集流体厚度h 2以相同的单位表示。例如，
Figure PCTCN2022070054-appb-000006
包括但不限于0.10，0.20，0.30，0.40，0.50以及以上述任意两个值为端点构成的范围。所述凹陷深度是指从集流体主表面到凹陷结构底部的最大距离。例如，对于圆柱体形凹陷结构，凹陷深度是集流体主表面到圆柱体的底面之间的距离。对于圆锥体形凹陷结构，凹陷深度是圆锥体顶点到集流体主表面之间的距离。在一些实施方式中，凹陷深度h 1在0.9-9.0μm的范围内，可选在1-8μm之间，可选在2-7μm之间。例如，凹陷深度h 1包括但不限于0.9μm，1.0μm，1.2μm，1.4μm，1.6μm，1.8μm，2.0μm，2.2μm，2.4μm，2.6μm，2.8μm，3.0μm，3.2μm，3.4μm，3.6μm，3.8μm，4.0μm，4.2μm，4.4μm，4.6μm，4.8μm，5.0μm，5.2μm，5.4μm，5.6μm，5.8μm，6.0μm，6.2μm，6.4μm，6.6μm，6.8μm，7.0μm，7.2μm，7.4μm，7.6μm，7.8μm，8.0μm，8.2μm，8.4μm，8.6μm，8.8μm，9.0μm以及以上述任意两个值为端点构成的范围。在一些实施方式中，集流体厚度h 2在9.0-18.0μm的范围内，包括但不限于9.5μm，10.0μm，10.5μm，11.0μm，11.5μm，12.0μm，12.5μm，13.0μm，13.5μm，14.0μm，14.5μm，15.0μm，15.5μm，16.0μm，16.5μm，17.0μm，17.5μm以及以上述任意两个值为端点构成的范围。凹陷深度h 1和集流体厚度h 2可以利用本领域已知方法测量，例如，可以按照JY/T010-1996进行集流体剖面分析，可以在线测量。发明人发现，上述凹陷结构的深度h 1和集流体厚度h 2满足上述关系时，集流体与活性材料之间的附着 力(咬合力)最大，能有效的抑制长期循环过程中活性材料的脱落。
在一些实施方式中，所述凹陷结构具有凹陷宽度W，所述凹陷宽度W与凹陷深度h 1的关系可以为：h 1≤W≤6h 1，其中所述凹陷宽度W是所述凹陷结构与集流体主表面相交的横截面的周缘上具有最大直线距离的两点之间的直线距离，其中所述凹陷宽度W与所述凹陷深度h 1以相同的单位表示。例如，当凹陷结构与集流体主表面相交的横截面是长方形或正方形时，凹陷宽度W为长方形的对角线长度；当凹陷结构与集流体主表面相交的横截面是圆形时，凹陷宽度W为圆形的直径；当凹陷结构与集流体主表面相交的横截面是三角形时，凹陷宽度W为三角形最长的边长。在一些实施方式中，凹陷宽度W可选为h 1，1.5h 1，2.0h 1，2.5h 1，3.0h 1，3.5h 1，4.0h 1，4.5h 1，5.0h 1，5.5h 1，6h 1以及以上述任意两个值为端点构成的范围。在一些实施方式中，凹陷宽度W在0.9-54.0μm的范围内，包括但不限于1.0μm，1.5μm，2.0μm，2.5μm，3.0μm，3.5μm，4.0μm，4.5μm，5.0μm，5.5μm，6.0μm，6.5μm，7.0μm，7.5μm，8.0μm，8.5μm，9.0μm，9.5μm，10.0μm，12.0μm，14.0μm，16.0μm，18.0μm，20.0μm，22.0μm，24.0μm，26.0μm，28.0μm，30.0μm，32.0μm，34.0μm，36.0μm，38.0μm，40.0μm，42.0μm，44.0μm，46.0μm，48.0μm，50.0μm，52.0μm以及以上述任意两个值为端点构成的范围。凹陷宽度W可以按照JY/T010-1996进行表面形貌分析，在线进行测量。发明人发现，所述凹陷结构的宽度与深度满足上述关系时，活性材料颗粒与集流体具有良好的有效接触，能快速传导电子，降低极片极化，提高电芯寿命。
在一些实施方式中，所述电极还包含位于集流体上的电极活性材料。电极活性材料位于集流体的第一主表面和/或第二主表面上。可以理解，正极集流体的第一主表面和/或第二主表面上设置正极活性材料，负极集流体的第一主表面和/或第二主表面上设置负极活性材料。在一些实施方式中，电极活性材料的粒径D90与凹陷深度h 1和凹陷宽度W之间的关系可以为：h 1≤D90≤W，其中所述粒径D90、所述凹陷深度h 1和所述凹陷宽度W以相同的单位表示。D90是指颗粒粒度分布中，从小到大累积分布百分数达到90％时对应的粒径值，即电极活性材料中，粒径小于D90的颗粒数占总颗粒数的90％。在一些实施方式中，电极活性材料的粒径D90在0.9-54.0μm的范围内，包括但不限于1.0μm， 1.5μm，2.0μm，2.5μm，3.0μm，3.5μm，4.0μm，4.5μm，5.0μm，5.5μm，6.0μm，6.5μm，7.0μm，7.5μm，8.0μm，8.5μm，9.0μm，9.5μm，10.0μm，12.0μm，14.0μm，16.0μm，18.0μm，20.0μm，22.0μm，24.0μm，26.0μm，28.0μm，30.0μm，32.0μm，34.0μm，36.0μm，38.0μm，40.0μm，42.0μm，44.0μm，46.0μm，48.0μm，50.0μm，52.0μm以及以上述任意两个值为端点构成的范围。D90可以按照GB/T19077-2016进行测量。发明人发现，当电极活性材料的粒径D90与凹陷深度h 1和凹陷宽度W之间满足上述关系时，凹陷结构与正极材料颗粒之间具有匹配性，保证凹陷结构的益处能被充分利用。
在一些实施方式中，凹陷面积A 1与集流体表面面积A 2的关系可以为：
Figure PCTCN2022070054-appb-000007
Figure PCTCN2022070054-appb-000008
其中所述凹陷面积A 1为所有凹陷结构与集流体主表面相交的横截面的面积之和，所述凹陷面积A 1与所述集流体表面面积A 2以相同的单位表示。例如，在一些实施方式中，凹陷面积A 1和集流体表面面积A 2的单位为厘米。在一些实施方式中，
Figure PCTCN2022070054-appb-000009
包括但不限于0.2，0.3，0.4，0.5，0.6，0.7，0.8以及以上述任意两个值为端点构成的范围。发明人发现，当集流体上所有凹陷结构的面积A1与集流体表面面积A2满足上述关系时，能从整体上抑制长期循环过程中活性材料的脱落。
在一些实施方式中，集流体表面上分布有凹陷结构的区域与集流体边缘的最小距离d可在以下范围：1mm≤d≤10mm。集流体表面上分布有凹陷结构的区域与集流体边缘的最小距离可以这样确定：观察与集流体边缘相邻的所有凹陷结构跟集流体主表面相交的横截面，找出横截面周缘上与集流体边缘最近的点，该点与该集流体边缘之间的最短距离即为上述最小距离d。d可用本领域已知的方法测量，例如用刻度尺测量。在一些实施方式中，d包括但不限于1mm，2mm，3mm，4mm，5mm，6mm，7mm，8mm，9mm，10mm以及以上述任意两个值为端点构成的范围。对于当前主流的卷绕式装配，电池在使用过程中通常轴向两端边缘极片在卷绕以及后续使用过程中会优先断裂，影响电芯寿命。
图1显示了根据本申请的一个实施方式的示例性集流体的剖面图，其示出了该集流体的凹陷结构的示意图。图2显示了该集流体的俯视图，其示出了凹陷结构的示例性形状和分布。应当理解，集流体的凹陷结构不限于图示的情形。
在一些实施方式中，集流体的一个主表面(第一主表面或第二主表面)上存在凹陷结构。在一些实施方式中，集流体的第一主表面和第二主表面上都存在凹陷结构。在集流体的第一主表面和第二主表面上都存在凹陷结构的实施方式中，第一主表面上的凹陷结构与第二主表面上的凹陷结构可以错位设置。所谓“错位设置”，是指若在第一主表面上的某个位置存在一个凹陷结构，则在第二主表面上与之相对的位置不存在凹陷结构；反之亦然。该设置可有效避免第一主表面和第二主表面的凹陷结构在集流体两侧的同一位置，进而避免了集流体过薄甚至集流体穿孔的现象发生。
在一些实施方式中，所述电极可以是正极，也可以是负极。可选地，所述电极是正极。
上述电极可以是二次电池的正极和/或负极，例如锂离子电池的正极和/或负极。但应理解，上述电极可以不限于二次电池的电极；根据本申请对电极的集流体作出上述改进的所有电极都落在本申请的范围之内。
本申请还提供了制备上述电极的方法，所述方法包括：
提供集流体，所述集流体包含第一主表面和第二主表面；
在所述第一主表面和第二主表面中的至少一个主表面形成延伸进入集流体内部的至少一个如上文所述的凹陷结构。
在一些实施方式中，所述凹陷结构通过物理方法或化学方法形成。在一些实施方式中，所述凹陷结构通过化学蚀刻形成。例如，可以取厚度为10-50μm的集流体，在集流体表面采用直流蚀刻工序，电流为0.1-1.0A，通电时间为0.05-3.0s，通电次数至少为一次。
根据本申请的二次电池可以是锂离子电池、钾离子电池、钠离子电池、锂硫电池等。
在一些实施方式中，所述二次电池是锂离子电池，其中电解液包含锂盐和添加剂，其中所述锂盐选自LiFSI、LiPF 6、三氟甲基磺酸锂、四氟硼酸锂、高氯酸锂中的至少一种，可选为LiFSI、LiPF 6中的至少一种；所述添加剂选自下组中的至少一种：
Figure PCTCN2022070054-appb-000010
含有上述锂盐和添加剂的电解液的电导率较高，且在化成容量过程优先在阴阳极界面形成稳定性高、阻抗较低的界面膜，这些特点有利于提高电芯的循环寿命和功率性能。
本申请还提供了制备上述二次电池的方法，其包括：
提供正极和负极，所述正极包含具有两个主表面的正极集流体，所述负极包含具有两个主表面的负极集流体，所述正极集流体和所述负极集流体中的至少一者包含从至少一个主表面延伸进入集流体内部的至少一个凹陷结构，所述凹陷结构具有凹陷深度h 1，
将隔膜置于正极和负极之间，形成裸电芯；
将裸电芯置于外包装中，向外包装中注入电解质，所述电解质具有电导率σ，
其中σ与h 1在数值上满足以下关系：8tanhh 1+0.2h 1≤σ≤10tanh(h 1)2+2+0.1h 1，其中凹陷深度h1的单位以微米计，电解质的电导率σ的单位以西门子/米计。
在本申请的二次电池中，负极集流体上设置有负极膜层，所述负极膜层包含负极活性材料，例如，天然石墨、人造石墨、软炭、硬炭、硅集流体料、锡集流体料、钛酸锂中的一种或几种。所述硅集流体料可选自单质硅、硅氧化物、硅碳复合物中的一种或几种。所述锡集流体料可选自单质锡、锡氧化合物、锡合金中的一种或几种。
所述负极膜层包含负极活性材料以及可选的粘结剂、可选的导电剂和其他 可选助剂，通常是由负极浆料涂布干燥而成的。负极浆料涂通常是将负极活性材料以及可选的导电剂和粘结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。
作为示例，导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑)、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、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)和羧甲基壳聚糖(CMCS)中的一种或几种。作为示例，粘结剂可包括丁苯橡胶(SBR)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或几种。其他可选助剂例如是增稠剂(如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
另外，在本申请的二次电池中，负极极片并不排除除了负极膜层之外的其他附加功能层。例如在某些实施方式中，本申请的负极极片还可包括夹在负极集流体和负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还可包括覆盖在负极膜层表面的覆盖保护层。
在本申请的二次电池中，正极集流体上设置有正极膜层，所述正极膜层包含正极活性材料。正极活性材料可选自LiNi 0.5-aMn 1.5M aO 4(0≤a≤0.1)、LiNi xCo yN zM 1-x-y-zO 2，其中N选自Mn和Al，M选自Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V和Ti中的任意一种，0≤x＜1，0≤y≤1，0≤z≤1，x+y+z≤1。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(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811))、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一种或几种。
正极膜层还可选地包括粘结剂。可用于正极膜层的粘结剂的非限制性例子可以包括以下的一种或多种：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。在一些实施方式中，正极膜层还可任选地包含导电剂。用于正极膜层的导电剂的例子可以包括超导碳、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一种或几种。在本申请的一个实施方式中，可以通过以下方式制备正极：将上述用于制备正极的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成均匀的正极浆料；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。
在本申请的二次电池中，隔膜将二次电池的阳极侧与阴极侧隔开，对体系内不同种类、尺寸和电荷的物质提供选择性透过或阻隔，例如隔膜可以对电子绝缘，将二次电池的正负极活性物质物理隔离，防止内部发生短路并形成一定方向的电场，同时使得电池中的离子能够穿过隔膜在正负极之间移动。在本申请的一个实施方式中，用来制备隔膜的材料可包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔膜可以是单层薄膜，也可以是多层复合薄膜。隔膜为多层复合薄膜时，各层的材料可以相同或不同。
在本申请的二次电池中，电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。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LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。在本申请的一个实施方式中，溶剂可选自以下的一种或多种：碳酸亚乙酯(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)。在本申请的一个实施方式中，以所述电解液的总重量为基准计，所述溶剂的含量为60-99重量％，例如65-95重量％，或者70-90重量％，或者75-89重量％，或者80-85重量％。在本申请的一个实施方式中，以所述电解液的总重量为基准计，所述电解质的含量为1-40重量％，例如5-35重量％，或者10-30重量％，或者11-25重量％，或者15-20重量％。
在本申请的二次电池的一个实施方式中，所述电解液中还可任选地包含添加剂。例如添加剂可以包括以下的一种或多种：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、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
在本申请的一个实施方式中，上述正极、负极和隔膜可通过卷绕工艺或叠片工艺制成电极组件/裸电芯。
在本申请的一个实施方式中，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/电解液。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。在另一些实施方式中，所述二次电池的外包装可以是软包，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。
本申请二次电池的形状可以是圆柱形、方形或其他任意的形状。图3是作为一个示例的方形结构的二次电池5。图4显示了图3的二次电池5的分解图，所述外包装可包括壳体51和盖板53，壳体51可包括底板和连接于底板上的侧板，所述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，该电极组件封装于所述容纳腔中，所述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。
电池模块、电池包和用电装置
在本申请的一个实施方式中，可以将若干个二次电池组装在一起以构成电 池模块，电池模块中包含两个或更多个本申请所述的二次电池，具体数量取决于电池模块的应用和单个电池模块的参数。
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。
在本申请的一个实施方式中，可以将两个或更多个上述电池模块组装成电池包，电池包所含电池模块的数量取决于电池包的应用和单个电池模块的参数。电池包可以包括电池箱和设置于电池箱中的多个电池模块，该电池箱包括上箱体和下箱体，上箱体能够盖在下箱体上并与之良好匹配，形成用于容纳电池模块的封闭空间。两个或更多个电池模块可以按照所需的方式排布于该电池箱中。
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。
在本申请的一个实施方式中，本申请的用电装置包括本申请的二次电池、电池模块或电池包中的至少一种，所述二次电池、电池模块或电池包可以用作所述电学装置的电源，也可以用作所述电学装置的能量存储单元。所述电学装置包括但不限于移动数字装置(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。
图8是作为一个示例的装置。该装置为纯电动车、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。
技术效果
本申请通过在电极集流体上设置凹陷结构并对凹陷结构和/或设置在集流体上的电极活性材料的粒度进行适当设置，或者对凹陷结构和电解液的导电率进行适当设置，出乎意料地提高了电池循环寿命和电池性能。
本申请包括但不限于以下有益的技术效果：
(1)提高电极活性材料颗粒与集流体的咬合力，增加电极活性材料颗粒与凹陷结构的匹配性，在冷压过程中避免活性材料颗粒挤压集流体而造成集流体表面钝化膜的破坏，有效抑制或者避免循环中后期电极活性材料颗粒的脱落，特别是能从整体上抑制长期循环过程中活性材料的脱落；
(2)活性材料颗粒与集流体具有良好的有效接触，能快速传导电子，降低极片极化，提高电芯寿命；
(3)有效弥补凹陷结构造成的锂离子传输路径边长的缺陷，帮助电子快速传输，提高电芯的功率性能。
实施例
下面将结合实施例进一步详细地描述本发明。应当理解，列举这些实施例只是为了起说明作用，而并不是用来限制本发明的范围。
在下述实施例、对比例中，所用到的试剂、材料以及仪器如没有特别说明，均可商购获得或合成获得。
实施例1-25和对比例1
1.电解液的制备
在充满氩气的手套箱中(水含量＜10ppm，氧气含量＜1ppm)，将碳酸乙烯酯(EC)、碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)三者按1∶1∶1的比例(质量比)均匀混合，向所得到的非水有机溶剂中缓慢加入适量的锂盐LiFSI和LiPF 6，待锂盐完全溶解后，加入1重量％的硫酸乙烯酯(DTD)，得到锂盐浓度为1mol/L(0.1M LiFSI+0.9M LiPF 6)的电解液。
2.正、负极集流体的制备
除对比例1中的正极集流体铝箔不制造凹陷结构外，按照下表1所示的参数，采用电化学刻蚀的方法在正极集流体铝箔的正反两个主表面上制造横截面是半圆形的凹陷结构。采用的铝箔的厚度(h 2)为18μm，宽度为80mm。表1中，d表示铝箔表面上分布有凹陷结构的区域与铝箔边缘的最小距离，使用刻度尺测量；A 1表示凹陷面积，A 2表示铝箔表面积；h 1表示凹陷深度，h 2表示铝箔厚度，它们按照JY/T010-1996进行集流体剖面分析，在线测量；W表示凹陷宽度，按照JY/T010-1996进行表面形貌分析，在线测量；D90表示电极活性材料颗粒的D90粒径，按照GB/T19077-2016测量；“√”表示采用双面错位刻蚀，“×”表示双面没有采用错位刻蚀。
以厚18μm、宽80mm的铜箔作为负极集流体。
表1 实施例1-25和对比例1中铝箔制备参数
Figure PCTCN2022070054-appb-000011
Figure PCTCN2022070054-appb-000012
3.正极片的制备
将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2、导电剂Super P炭黑、粘结剂聚偏二氟乙烯(PVDF)在N-甲基吡咯烷酮(NMP)中制成正极浆料。正极浆料中固体含量为50wt％，固体成分中LiNi 0.8Co 0.1Mn 0.1O 2、Super P、PVDF的质量比为8∶1∶1。将正极浆料涂布在铝箔集流体上并在85℃下烘干后进行冷压，然后进行切边、裁片、分条，接着在85℃的真空条件下烘干4h，制成正极片。
4.负极片的制备
将作为负极活性材的石墨与导电剂Super P炭黑、增稠剂羧甲基纤维素(CMC)、粘接剂丁苯橡胶(SBR)在去离子水中混合均匀，制成负极浆料。负极浆料中固体含量为30wt％，固体成分中石墨、Super P、CMC和SBR的质量比为80∶15∶3∶2。将负极浆料涂布在集流体铜箔上并在85℃下烘干，然后进行冷压、切边、裁片、分条，接着在120℃真空条件下烘干12h，制成负极片。
5.锂离子电池的制备
以16μm的聚乙烯薄膜(PE)作为隔膜。将制得的正极片、隔膜、负极片按顺序叠好，使隔膜处于正、负极片中间，起到隔离正、负极的作用，卷绕得到裸电芯，焊接极耳，将裸电芯置于外包装中，将上述制备的电解液注入到干燥后的电芯中，进行封装、静置、化成、整形、容量测试等，完成锂离子电池的制备(软包锂离子电池的厚度4.0mm、宽度60mm、长度140mm)。
接下来说明锂离子电池的测试过程。
1.锂离子电池的循环性能
25℃下，1C恒流充电到4.25V，恒压充电到0.05C，然后以1C放电到2.8V，记录首次放电容量C1。如此循环测试，第200圈的放电容量为Cn，容量保持率＝C1/Cn*100％。
2.锂离子电池的功率性能
室温条件下，锂离子电池以1C恒流充电到4.25V，恒压充电至电流为0.05C，电池满充后，静置5min，1C放电30min(电芯带电量为50％SOC(荷电状态))，静置5min，调节温度为25℃，静置1h，记录此时电芯的电压V1，0.4C放电15s，记录脉冲放电后的电压V2，则电芯50％SOC时的直流阻抗DCR＝(V 1-V2)/I，I＝0.4C。
测试结果见表2。
表2 实施例1-25和对比例1的电池性能表征结果
Figure PCTCN2022070054-appb-000013
Figure PCTCN2022070054-appb-000014
实施例26-29和对比例2
按照上面“实施例1-25和对比例1”部分所述的方法制备电解液和具有凹陷结构的铝箔正极集流体，不同的是，电解液的电导率σ和凹陷结构的深度h 1如下表3所示。正极片、负极片和锂离子电池的制备方法与“实施例1-25和对比例1”部分所述的方法相同，并且按照同样的方法测试锂离子电池的循环性能和功率性能，结果如表4所示。其中，电解液的电导率可以通过调节溶剂、锂盐的种类、含量来确定。具体见表5。电解液的电导率按照HG-T 4067-2015测量。
表3 实施例26-29和对比例2中铝箔凹陷结构和电解液参数
  凹陷结构深度h 1(μm) 电解液电导率σ(mS/cm)
实施例26 0.9 7.5
实施例27 2 10
实施例28 4 11
实施例29 9 12
对比例2 0.9 5
表4 实施例26-29和对比例2的电池性能表征结果
  电池循环性能 常温DCR(mΩ)
实施例26 98.9％ 21
实施例27 99.3％ 16
实施例28 99.5％ 17
实施例29 98.0％ 27
对比例2 83.2％ 41
表5 实施例26-29和对比例2的电解液中溶剂、锂盐的种类和含量
Figure PCTCN2022070054-appb-000015
实施例26-29中铝箔上凹陷结构的深度h 1与电解液电导率σ满足8tanhh 1+0.2h 1≤σ≤10tanh(h 1) 2+2+0.1h 1。结果显示，当集流体上的凹陷结构的深度h 1与电解液电导率σ满足上述关系时，锂离子电池的循环性能和功率性能得到显著提升，由此提高电池循环寿命和综合性能。不受限于任何特定理论，据认为，当电极活性材料颗粒部分嵌入集流体的凹陷结构中时，不利于电解液快速浸润，即不利于锂离子在固相中的迁移，而调整电解液的电导率(调整锂离子在电解液中的传输速度)，有利于弥补由于上述凹陷结构造成的问题。
虽然已经参考实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (16)

  1. 一种二次电池，其包含正极，负极，位于正极和负极之间的隔膜，以及电解液，其中正极包含具有两个主表面的正极集流体，负极包含具有两个主表面的负极集流体，所述正极集流体和所述负极集流体中的至少一者包含从至少一个主表面延伸进入集流体内部的至少一个凹陷结构，所述凹陷结构具有凹陷深度h 1，单位为微米，所述电解液具有电导率σ，单位为西门子/米，其中σ与h 1在数值上满足以下关系：8tanhh 1+0.2h 1≤σ≤10tanh(h 1) 2+2+0.1h 1。
  2. 如权利要求1所述的二次电池，其中所述凹陷结构的凹陷深度h 1与所述凹陷结构所在的集流体的厚度h 2之间的关系为：
    Figure PCTCN2022070054-appb-100001
    其中所述凹陷深度h 1和所述集流体的厚度h 2以相同的单位表示。
  3. 如权利要求1所述的二次电池，其中所述凹陷结构具有凹陷宽度W，所述凹陷宽度W与凹陷深度h 1的关系为：h 1≤W≤6h 1，其中所述凹陷宽度W是所述凹陷结构与所述凹陷结构所在的集流体的主表面相交的横截面的周缘上具有最大直线距离的两点之间的直线距离，其中所述凹陷宽度W与所述凹陷深度h 1以相同的单位表示。
  4. 如权利要求1所述的二次电池，其中集流体上设置有电极活性材料，集流体上的电极活性材料的粒径D90与该集流体上的凹陷结构的凹陷深度h 1和凹陷宽度W之间的关系为：h 1≤D90≤W，其中所述粒径D90、所述凹陷深度h 1和所述凹陷宽度W以相同的单位表示。
  5. 如权利要求1所述的二次电池，其中所述凹陷结构的凹陷面积A 1与所述凹陷结构所在的集流体的表面面积A 2的关系为：
    Figure PCTCN2022070054-appb-100002
    其中所述凹陷面积A 1为该集流体上所有的凹陷结构与该集流体的主表面相交的横截面的面积之和，所述凹陷面积A 1与该集流体的表面面积A 2以相同的单位表示。
  6. 如权利要求1所述的二次电池，其中集流体表面上分布有凹陷结构的区域与该集流体边缘的最小距离d满足1mm≤d≤10mm。
  7. 如权利要求1所述的二次电池，其中所述集流体选自铝箔和铜箔。
  8. 如权利要求1所述的二次电池，其中集流体的两个主表面上都存在凹 陷结构，两个主表面上的凹陷结构可选错位设置。
  9. 如权利要求1所述的二次电池，其中所述凹陷深度h 1在0.9-9.0μm之间，可选在1-8μm之间，可选在2-7μm之间。
  10. 如权利要求1所述的二次电池，其中所述正极集流体包含从其至少一个主表面延伸进入正极集流体内部的凹陷结构。
  11. 如权利要求10所述的二次电池，其中所述正极集流体包含从其两个主表面延伸进入正极集流体内部的凹陷结构，其中所述两个主表面上的凹陷结构可选错位设置。
  12. 如权利要求1所述的二次电池，其中所述二次电池是锂离子电池，所述电解液包含锂盐和添加剂，其中所述锂盐选自LiFSI、LiPF 6、三氟甲基磺酸锂、四氟硼酸锂、高氯酸锂中的至少一种，可选为LiFSI、LiPF 6中的至少一种。
  13. 如权利要求12所述的二次电池，其中所述添加剂选自下组中的至少一种：
    Figure PCTCN2022070054-appb-100003
  14. 一种电池模块，其包括权利要求1-13中任意一项所述的二次电池。
  15. 一种电池包，其包括权利要求14所述的电池模块。
  16. 一种用电装置，其包括权利要求1-13中任意一项所述的二次电池、权利要求14所述的电池模块和权利要求15所述的电池包中的至少一种。
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