WO2024130626A1 - 二次电池及用电装置 - Google Patents

二次电池及用电装置 Download PDF

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Publication number
WO2024130626A1
WO2024130626A1 PCT/CN2022/140954 CN2022140954W WO2024130626A1 WO 2024130626 A1 WO2024130626 A1 WO 2024130626A1 CN 2022140954 W CN2022140954 W CN 2022140954W WO 2024130626 A1 WO2024130626 A1 WO 2024130626A1
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WIPO (PCT)
Prior art keywords
primer layer
secondary battery
positive electrode
electrode assembly
area
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CN2022/140954
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English (en)
French (fr)
Inventor
雷廷玲
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Dongguan Amperex Technology Ltd
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Dongguan Amperex Technology Ltd
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Application filed by Dongguan Amperex Technology Ltd filed Critical Dongguan Amperex Technology Ltd
Priority to PCT/CN2022/140954 priority Critical patent/WO2024130626A1/zh
Priority to EP22968927.8A priority patent/EP4636899A4/en
Priority to CN202280012545.7A priority patent/CN116830346A/zh
Publication of WO2024130626A1 publication Critical patent/WO2024130626A1/zh
Priority to US19/244,654 priority patent/US20250316774A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/668—Composites of electroconductive material and synthetic resins
    • 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
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/105—Pouches or flexible bags
    • 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
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/131—Primary casings; Jackets or wrappings characterised by physical properties, e.g. gas permeability, size or heat resistance
    • 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
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/14—Primary casings; Jackets or wrappings for protecting against damage caused by external factors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application belongs to the field of battery technology, and specifically relates to a secondary battery and an electrical device.
  • Secondary batteries represented by lithium-ion batteries have outstanding features such as high energy density, long cycle life, no pollution, and no memory effect. As a clean energy, the application of secondary batteries has gradually spread from electronic products to large-scale devices such as electric vehicles to adapt to the sustainable development strategy of the environment and energy. Therefore, higher requirements are also placed on the safety performance of secondary batteries.
  • the purpose of the present application is to provide a secondary battery and an electrical device, aiming to improve the safety performance of the secondary battery.
  • the first aspect of the present application provides a secondary battery, comprising an electrode assembly and a housing for accommodating the electrode assembly.
  • the positive electrode sheet of the electrode assembly comprises: a positive electrode current collector and a primer layer coated on the surface of the positive electrode current collector.
  • the second primer layer is arranged on at least part of the surface of the outermost circle of the electrode assembly. Compared with the blank positive current collector or the primer layer of uniform thickness, the second primer layer has a higher roughness, so that the outermost circle of the electrode assembly and the inner wall of the shell have a larger friction coefficient. As a result, in the case of a fall of the secondary battery, the electrode assembly is not easy to slide relative to the shell, so that the impact of the electrode assembly on the shell can be reduced, thereby reducing the risk of failure of the secondary battery due to falling, thereby improving the safety performance of the secondary battery.
  • the ratio of the thickness d1 of the concave area to the thickness d2 of the convex area is 0 to 4/5.
  • the ratio of the thickness of the concave area to the thickness of the convex area is within the above-mentioned appropriate range, which can increase the friction coefficient between the outermost circle of the electrode assembly and the inner wall of the shell while making the second primer layer have a higher structural stability. As a result, a larger friction coefficient can be maintained between the outermost circle of the electrode assembly and the inner wall of the shell, thereby reducing the risk of failure of the secondary battery after falling, thereby improving the safety performance of the secondary battery.
  • the ratio of the thickness d1 of the concave area to the thickness d2 of the convex area is 1/3 to 4/5.
  • the ratio of the thickness of the concave area to the thickness of the convex area within the above-mentioned appropriate range can increase the friction coefficient between the outermost ring of the electrode assembly and the inner wall of the shell while further improving the structural stability of the second primer layer. As a result, the risk of failure of the secondary battery after falling can be further reduced, thereby further improving the safety performance of the secondary battery.
  • the thickness d1 of the concave area is 1 ⁇ m to 2.5 ⁇ m.
  • the thickness of the concave area is within the above-mentioned suitable range, on the one hand, it is conducive to reducing the processing difficulty of the second primer layer; on the other hand, it is conducive to making the second primer layer have a certain mechanical strength, so that the second primer layer has good structural stability; on the other hand, it is conducive to the secondary battery to maintain a high volume energy density. Therefore, the secondary battery of the present application can have both high safety performance and high volume energy density.
  • the raised area is composed of a plurality of spaced raised portions, and/or the recessed area is composed of a plurality of spaced recessed portions.
  • the outermost circle of the electrode assembly includes two curved portions and two straight portions, and a second primer layer is disposed on the surface of at least one straight portion.
  • the second primer layer may also be disposed on the outermost circle.
  • a second aspect of the present application provides an electrical device, comprising the secondary battery of the present application.
  • the electric device of the present application includes the secondary battery of the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an electrode assembly in a secondary battery according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of an electrode assembly in a secondary battery according to another embodiment of the present application.
  • FIG. 3 is a schematic diagram of an electrode assembly in a secondary battery according to another embodiment of the present application.
  • FIG. 5 is a schematic longitudinal cross-sectional view of a positive electrode sheet in a secondary battery according to an embodiment of the present application.
  • FIG. 6 is a top view of the positive electrode sheet shown in FIG. 5 .
  • FIG. 7 is a schematic longitudinal cross-sectional view of a positive electrode sheet in a secondary battery according to another embodiment of the present application.
  • FIG. 9 is a schematic diagram of a second primer layer in a secondary battery according to an embodiment of the present application.
  • FIG. 10 is a schematic diagram of a second primer layer in a secondary battery according to another embodiment of the present application.
  • FIG. 11 is a schematic diagram of a second primer layer in a secondary battery according to another embodiment of the present application.
  • FIG. 12 is a schematic diagram of a second primer layer in a secondary battery according to another embodiment of the present application.
  • FIG. 13 is a schematic diagram of a second primer layer in a secondary battery according to another embodiment of the present application.
  • FIG. 14 is a schematic diagram of a second primer layer in a secondary battery according to another embodiment of the present application.
  • FIG. 15 is a schematic diagram of a second primer layer in a secondary battery according to another embodiment of the present application.
  • FIG. 16 is a schematic diagram of a second primer layer in a secondary battery according to another embodiment of the present application.
  • FIG. 17 is a schematic diagram of an electric device using an embodiment of the secondary battery of the present application as a power source.
  • 10 electrode assembly 100 positive electrode sheet; 110 positive electrode current collector; 110a positive electrode current collector surface; 120a first primer layer; 120b second primer layer; 130 positive electrode active material layer; 01 convex portion; 02 concave portion.
  • any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range.
  • each point or single value between the range endpoints is included in the range.
  • each point or single value can be combined as its own lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unambiguous range.
  • the term “about” is used to describe and illustrate small changes.
  • the term may refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very approximately.
  • the term may refer to a range of variation of less than or equal to ⁇ 10% of the numerical value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • amounts, ratios, and other numerical values are sometimes presented in this article in a range format.
  • a list of items connected by the terms “at least one of,” “at least one of,” “at least one of,” or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • Secondary batteries usually consist of an electrode assembly and an outer packaging for containing the electrode assembly.
  • Common outer packaging such as aluminum-plastic film, has a relatively smooth inner wall. Therefore, the friction between the electrode assembly and the inner wall of the outer packaging is small, and it is easy for the electrode assembly to move inside the outer packaging. In the event of a fall, the electrode assembly is likely to move relative to the outer packaging, causing the aluminum foil to tear, the top seal to break, and the outer packaging corners to break, thus causing the battery to fail.
  • double-sided tape is usually installed between the electrode assembly and the outer packaging, or the inner wall of the outer packaging is bonded to the electrode assembly with glue to reduce the movement of the electrode assembly; or the outer packaging is reinforced, for example, glue is applied to the aluminum foil of the outer packaging to increase the local strength of the aluminum foil; or a buffer structure is added between the electrode assembly and the outer packaging to alleviate the impact force of the electrode assembly on the outer packaging when the battery falls.
  • glue is applied to the aluminum foil of the outer packaging to increase the local strength of the aluminum foil
  • a buffer structure is added between the electrode assembly and the outer packaging to alleviate the impact force of the electrode assembly on the outer packaging when the battery falls.
  • the electrode assembly of the secondary battery includes a specific positive electrode plate, which can make the secondary battery have high safety performance.
  • the first aspect of the present application provides a secondary battery, including any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy.
  • a secondary battery may include all kinds of lithium secondary batteries or sodium secondary batteries.
  • the secondary battery of the present application includes an electrode assembly and a housing for accommodating the electrode assembly.
  • the electrode assembly can be made of a positive electrode sheet, a negative electrode sheet and a separator through a winding process.
  • the positive electrode sheet of the electrode assembly includes: a positive electrode current collector, and a primer layer coated on the surface of the positive electrode current collector.
  • the bottom coating layer includes a first bottom coating layer and a second bottom coating layer
  • the positive electrode active material layer is located on the surface of the first bottom coating layer
  • the second bottom coating layer is arranged on at least part of the surface of the outermost circle of the electrode assembly
  • the positive electrode active material layer is not arranged on the surface of the second bottom coating layer
  • a convex area and a concave area are also arranged on the second bottom coating layer
  • the convex area accounts for 50% to 80% of the area of the second bottom coating layer.
  • the area of the convex area can account for 50%, 55%, 60%, 65%, 70%, 75%, 80% of the area of the second bottom coating layer, or within the range of any of the above values.
  • the shell may include, but is not limited to, a shell known in the art for encapsulating an electrode assembly and an electrolyte.
  • the shell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc., or a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PBS polybutylene succinate
  • the positive electrode current collector may be, but is not limited to, a metal foil or a composite current collector.
  • the positive electrode current collector may be aluminum foil.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, and the like.
  • the above-mentioned second primer layer can be a primer layer having substantially the same composition as the first primer layer.
  • the second primer layer is disposed on at least a portion of the surface of the outermost circle of the electrode assembly, that is, the second primer layer can completely cover the outermost circle of the electrode assembly, or can cover a portion of the surface of the outermost circle of the electrode assembly.
  • FIG. 1 is a schematic diagram of an embodiment of an electrode assembly in a secondary battery of the present application. As shown in FIG. 1 , in the exemplary electrode assembly 10, the outermost circle surface of the electrode assembly 10 is entirely provided with a second primer layer 120 b.
  • the outermost circle of the electrode assembly 10 includes two curved portions and two straight portions, and at least one straight portion surface is provided with a second primer layer 120 b. Therefore, the scheme of FIG. 1 can adopt the structure of FIG. 2. In addition, the schemes of simplified structures FIG. 3 and FIG. 4 also significantly improve the pass rate of the drop test.
  • the second primer layer and the first primer layer may be continuously distributed except for the welding tab region.
  • FIG. 5 and 6 are schematic diagrams of an embodiment of a positive electrode sheet in a secondary battery of the present application, and the positive electrode sheet can be formed into an electrode assembly through a winding process with a negative electrode sheet and a separator.
  • FIG. 5 is a schematic diagram of a longitudinal section of the exemplary positive electrode sheet 100
  • FIG. 6 is a top view of the exemplary positive electrode sheet 100.
  • a primer layer is provided on the surface of the positive current collector 110, and the primer layer includes a first primer layer 120a and a second primer layer 120b. After winding, the second primer layer 120b can be located at the outermost circle of the electrode assembly.
  • the first primer layer 120a is located in the middle section of the positive electrode sheet of the electrode assembly.
  • the first primer layer 120a can extend to the tail of the positive electrode sheet and be arranged opposite to the second primer layer 120b. Further optionally, the first primer layer 120a can also extend to the winding start end of the positive electrode sheet.
  • the positive active material layer 130 is located on the surface of the first primer layer 120a. The tab can be welded to the positive current collector surface 110a located in the middle of the positive electrode sheet.
  • the positive current collector surface 110a can be a hollow current collector surface reserved during coating, on which the primer layer and the positive active material layer are not coated, or a hollow current collector surface formed by hollowing out a part of the positive active material layer 130 and the first primer layer 120a after continuous coating.
  • FIGS. 7 and 8 are schematic diagrams of an embodiment of a positive electrode sheet in a secondary battery of the present application, and the positive electrode sheet can be formed into an electrode assembly through a winding process with a negative electrode sheet and a separator.
  • FIG. 7 is a schematic diagram of a longitudinal section of the exemplary positive electrode sheet 100
  • FIG. 8 is a top view of the exemplary positive electrode sheet 100.
  • a primer layer is provided on the surface of the positive current collector 110, and the primer layer includes a first primer layer 120a and a second primer layer 120b. After winding, the second primer layer 120b can be located at the outermost circle of the electrode assembly.
  • the first primer layer 120a is located in the middle section of the positive electrode sheet of the electrode assembly.
  • the first primer layer 120a can extend to the tail of the positive electrode sheet and be arranged opposite to the second primer layer 120b. Further optionally, the first primer layer 120a can also extend to the winding starting end of the positive electrode sheet.
  • the positive electrode active material layer 130 is located on the surface of the first primer layer 120a. The tab can be welded to the positive electrode current collector surface 110a located at the starting end of the positive electrode sheet.
  • the positive electrode current collector surface 110a can be an empty current collector surface reserved during coating, on which the primer layer and the positive electrode active material layer are not coated, or it can be an empty current collector surface formed by hollowing out part of the first primer layer 120a located at the starting end of the positive electrode sheet after continuous coating.
  • the raised area may be an area with a relatively large thickness in the second primer layer.
  • the above-mentioned concave area may be an area with a relatively small thickness in the second primer layer.
  • the raised area and the concave area may be distributed alternately.
  • the present application does not particularly limit the formation method of the raised area and the concave area. No matter how the raised area and the concave area are formed, as long as the second primer layer includes a raised area with a large thickness and a concave area with a small thickness, so that the outermost circle of the electrode assembly has a certain roughness.
  • the raised area may be formed by thickening part of the primer layer, and the concave area may be formed by an untreated part of the primer layer, a thinned part of the primer layer, or a hollowed part of the primer layer.
  • the raised area may be formed by an untreated primer layer, and the concave area may be formed by a thinned primer layer or a hollowed primer layer.
  • the raised area may be formed by a thinned primer layer, and the concave area may be formed by a thinned primer layer or a hollowed primer layer.
  • the second primer layer is arranged on at least part of the surface of the outermost circle of the electrode assembly. Compared with the blank positive current collector or the primer layer of uniform thickness, the second primer layer has a higher roughness, so that the outermost circle of the electrode assembly and the inner wall of the shell have a larger friction coefficient. As a result, in the case of a fall of the secondary battery, the electrode assembly is not easy to slide relative to the shell, so that the impact of the electrode assembly on the shell can be reduced, thereby reducing the risk of failure of the secondary battery due to falling, thereby improving the safety performance of the secondary battery.
  • the present application can reduce the risk of failure of the secondary battery due to falling by arranging the second primer layer on at least part of the surface of the outermost circle of the electrode assembly.
  • the secondary battery of the present application is not only simple in process, but also does not need to introduce a complex structure inside the secondary battery, which greatly reduces the processing difficulty and manufacturing cost of the secondary battery. As a result, the secondary battery of the present application can have both high safety performance and high production capacity.
  • the area of the raised area in the second primer layer may account for 55% to 70%.
  • the area of the raised area may account for 55%, 58%, 60%, 62%, 65%, 68%, 70% of the area of the second primer layer, or within the range of any of the above values.
  • the second primer layer can have both high roughness and certain mechanical strength.
  • the outermost ring of the electrode assembly can not only have a high friction coefficient with the inner wall of the shell, but also have a certain strength. Therefore, when the secondary battery of the present application falls, the electrode assembly is not only not easy to slide relative to the shell, but also can withstand a certain impact force, thereby further improving the safety performance of the secondary battery.
  • the ratio of the thickness d1 of the concave region to the thickness d2 of the convex region is 0 to 4/5.
  • the ratio of the thickness d1 of the concave region to the thickness d2 of the convex region can be 0, 1/5, 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, or within the range of any of the above values.
  • the thickness of the convex region is greater than the thickness of the concave region; the thickness d1 of the concave region refers to the vertical distance from the surface of the concave region away from the positive electrode current collector to the surface of the positive electrode current collector, and the thickness d2 of the convex region refers to the vertical distance from the surface of the convex region away from the positive electrode current collector to the surface of the positive electrode current collector.
  • the ratio of the thickness of the concave area to the thickness of the convex area within the above-mentioned suitable range can increase the friction coefficient between the outermost circle of the electrode assembly and the inner wall of the shell, while making the second primer layer have a higher structural stability.
  • a larger friction coefficient can be maintained between the outermost circle of the electrode assembly and the inner wall of the shell, thereby reducing the risk of failure of the secondary battery after falling, thereby improving the safety performance of the secondary battery.
  • the ratio of the thickness d1 of the concave region to the thickness d2 of the convex region is 1/3 to 4/5.
  • the ratio of the thickness d1 of the concave region to the thickness d2 of the convex region can be 1/3, 1/2, 2/3, 3/5, 2/3, 3/4, 4/5, or within the range of any of the above values.
  • the ratio of the thickness of the inner concave area to the thickness of the convex area within the above-mentioned suitable range can increase the friction coefficient between the outermost ring of the electrode assembly and the inner wall of the shell, while further improving the structural stability of the second primer layer. As a result, the risk of failure of the secondary battery after falling can be further reduced, thereby further improving the safety performance of the secondary battery.
  • the thickness d1 of the concave region may be 1 ⁇ m to 2.5 ⁇ m.
  • the thickness d1 of the concave region may be 1 ⁇ m, 1.2 ⁇ m, 1.5 ⁇ m, 1.8 ⁇ m, 2 ⁇ m, 2.2 ⁇ m, 2.5 ⁇ m or any range thereof.
  • the secondary battery of the present application can have both high safety performance and high volume energy density.
  • the friction coefficient ⁇ between the outermost ring of the electrode assembly and the inner wall of the housing may satisfy: 0.35 ⁇ 0.5.
  • ⁇ may be 0.35, 0.4, 0.45, 0.5, or within a range of any of the above values.
  • the friction coefficient ⁇ between the outermost ring of the electrode assembly and the inner wall of the housing may satisfy: 0.39 ⁇ 0.45.
  • ⁇ may be 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, or within a range of any of the above values.
  • the raised area may be composed of a plurality of convex portions arranged at intervals.
  • the concave area may be composed of a plurality of concave portions arranged at intervals.
  • the raised area may be formed by thickening a portion of the primer layer, and these thickened areas may form a plurality of convex portions arranged at intervals.
  • the concave area may be formed by thinning a portion of the primer layer, or by hollowing out a portion of the primer layer, and these thinning or hollowing areas may form a plurality of concave portions arranged at intervals.
  • the second primer layer may include a plurality of convex portions formed by thickening a portion of the primer layer, and a plurality of concave portions formed by thinning a portion of the primer layer or by hollowing out a portion of the primer layer.
  • a plurality of convex portions and a plurality of concave portions may be arranged at intervals, or may be continuously arranged in different regions of the second primer layer, respectively.
  • the raised area may be composed of a plurality of spaced raised portions 01, and the concave area may be composed of a plurality of spaced concave portions 02.
  • the raised area may be composed of a plurality of spaced raised portions 01, and the concave area may be composed of a plurality of spaced concave portions 02.
  • the raised area may be composed of a plurality of spaced raised portions 01, and the concave area may be composed of a plurality of spaced concave portions 02.
  • the outermost circle of the electrode assembly includes two curved portions and two straight portions, and a second primer layer is disposed on the surface of at least one straight portion. In order to further increase the friction surface, a second primer layer may also be disposed on the outermost circle.
  • the peel strength between the primer layer and the positive electrode current collector may be no less than 150 N/m, for example, may be greater than 150 N/m, greater than 200 N/m, greater than 300 N/m or greater than 400 N/m.
  • the peel strength between the primer layer and the positive electrode current collector is within the above-mentioned relatively high range, which enables the primer layer and the positive electrode current collector to be closely combined, thereby improving the structural stability of the positive electrode current collector.
  • the primer layer is not easy to fall off from the surface of the positive electrode current collector to expose the positive electrode current collector, thereby reducing the probability of the positive electrode current collector contacting the negative electrode and causing a short circuit.
  • the safety performance of the secondary battery can be further improved.
  • the primer layer may include inorganic particles, a binder, a conductive agent and an optional auxiliary agent.
  • the primer layer may also only include a binder, a conductive agent and an optional auxiliary agent.
  • the second primer layer may include inorganic particles, a binder, an optional conductive agent and an optional auxiliary agent.
  • the second primer layer may also only include a binder, an optional conductive agent and an optional auxiliary agent.
  • the inorganic particles can be selected from inorganic particles known in the art and can be used for the base coating, for example, the inorganic particles can be selected from at least one of boehmite, diaspore, alumina, barium sulfate, calcium carbonate, and calcium silicate. Alternatively, the inorganic particles can be selected from boehmite and/or alumina.
  • the binder can be selected from the binders known in the art and can be used for the primer layer, for example, the binder can be selected from at least one of polypropylene binders, polyacrylate binders, acrylonitrile multipolymers, and carboxymethyl cellulose salts. Alternatively, the binder can be selected from a binder obtained by polymerizing one or more of acrylic acid nitrile, acrylic acid salt, acrylamide, and acrylic acid ester as monomers.
  • the conductive agent can be selected from conductive agents known in the art and can be used for the base coating.
  • the conductive agent can be selected from at least one of conductive carbon black (Super P), carbon fiber, graphene or carbon nanotubes (CNT).
  • the primer layer may include 50% to 95% of inorganic particles, 2% to 50% of a binder, and 0.5% to 10% of a conductive agent, based on 100% of the total mass.
  • the base coating layer may include 50% to 95% of inorganic particles, 5% to 50% of a binder, and 0 to 2% of other optional additives, based on the total mass as 100%.
  • the other optional additives may include, but are not limited to, a leveling agent or a dispersant.
  • the specific type of the positive electrode active material of the positive electrode active material layer is not subject to specific restrictions and can be selected according to needs.
  • the positive electrode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds.
  • the modified compounds of the above-mentioned positive electrode active materials may be doping modification, surface coating modification, or doping and surface coating modification of the positive electrode active material.
  • the lithium transition metal oxide may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof.
  • the lithium phosphate containing olivine structure may include one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and modified compounds thereof. These positive electrode active materials may be used alone or in combination of two or more.
  • the positive electrode active material layer may further include a binder.
  • the specific type of the binder is not specifically limited and may be selected according to demand.
  • the binder includes but is not limited to at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • VDF polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer vinylidene fluor
  • the positive electrode active material layer may further include a conductive agent.
  • the specific type of the conductive agent is not subject to specific restrictions and may be selected according to demand.
  • the conductive agent includes but is not limited to at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet in the present application can be prepared according to conventional methods in the art.
  • the primer slurry is applied to the surface of the positive current collector, and part of the surface of the primer is treated to form a second primer, thereby obtaining a positive current collector having a first primer and a second primer on the surface;
  • the positive active material layer is usually formed by applying the positive electrode slurry on the surface of the first primer of the positive current collector, drying and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive active material, an optional conductive agent, an optional binder and any other components in a solvent and stirring them evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the material, composition and manufacturing method of the negative electrode plate may include any technology known in the prior art.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector and including a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • a metal foil or a porous metal plate can be used, for example, a foil or a porous plate of a metal such as copper, nickel, titanium, iron, or an alloy thereof.
  • the negative electrode current collector is a copper foil.
  • negative electrode active material is not subject to specific restrictions and can be selected according to needs.
  • other negative electrode active materials include but are not limited to at least one of natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li- Sn -O alloy, Sn, SnO, SnO2 , spinel structured Li4Ti5O12 , and Li-Al alloy.
  • the negative electrode active material layer may further include a binder.
  • the specific type of the binder is not subject to specific restrictions and can be selected according to needs.
  • the binder includes butadiene styrene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin and at least one of carboxymethyl cellulose.
  • the negative electrode active material layer may further include a conductive agent.
  • the specific type of the conductive agent is not subject to specific restrictions and may be selected according to demand.
  • the conductive agent includes but is not limited to at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet in the present application can be prepared according to conventional methods in the art.
  • the negative electrode active material, the conductive agent, the binder and the thickener are dispersed in a solvent, and the solvent can be N-methylpyrrolidone (NMP) or deionized water to form a uniform negative electrode slurry, and the negative electrode slurry is coated on the negative electrode current collector, and the negative electrode sheet is obtained through drying, cold pressing and other processes.
  • NMP N-methylpyrrolidone
  • the negative electrode sheet in the present application does not exclude other additional functional layers besides the negative electrode active material layer.
  • the negative electrode sheet of the present application also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the current collector and the active material layer and disposed on the surface of the negative electrode current collector.
  • the negative electrode sheet of the present application also includes a protective layer covering the surface of the negative electrode active material layer.
  • the separator is arranged between the positive electrode plate and the negative electrode plate, mainly to prevent the positive and negative electrodes from short-circuiting, and at the same time to allow active ions to pass through.
  • the present application has no particular restrictions on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited thereto.
  • the isolation membrane can be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different. In some embodiments, a ceramic coating or a metal oxide coating can also be provided on the isolation membrane.
  • the secondary battery of the present application may further include an electrolyte.
  • the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.
  • the electrolyte that can be used in the secondary battery of the present application may be an electrolyte known in the prior art.
  • the electrolyte includes an organic solvent, a lithium salt, and optional additives.
  • the types of the organic solvent, the lithium salt, and the additives are not subject to specific limitations and can be selected according to requirements.
  • the lithium salt includes, but is not limited to, at least one of LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiFSI (lithium bisfluorosulfonyl imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO 2 F 2 (lithium difluorophosphate), LiDFOP (lithium difluorobisoxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiFSI lithium bisflu
  • the organic solvent includes but is not limited to 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), cyclopentane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sul
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the additive includes, but is not limited to, at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl carbonate (VEC), diethylene sulfate (DTD), propylene sulfate, vinyl sulfite (ES), 1,3-propane sultone (PS), 1,3-propylene sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN), adiponitrile (AND), tris(trimethylsilyl) phosphate (TMSP), and tris(trimethylsilyl) borate (TMSB).
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • VEC vinyl carbonate
  • DTD diethylene sulfate
  • ES vinyl sulfite
  • PS 1,3-propane sultone
  • PST 1,3-propylene sultone
  • succinic anhydride succin
  • the electrolyte can be prepared according to conventional methods in the art.
  • an organic solvent, a lithium salt, and an optional additive can be mixed evenly to obtain an electrolyte.
  • an organic solvent, a lithium salt, and an optional additive can be mixed evenly to obtain an electrolyte.
  • an optional additive can be added to an organic solvent and mixed evenly to obtain an electrolyte; or, a lithium salt is first added to an organic solvent, and then the optional additive is added to the organic solvent and mixed evenly to obtain an electrolyte.
  • the friction coefficient between the outermost ring of the electrode assembly and the inner wall of the shell can be determined according to the test standard GB/T10006-2021 "Method for determining the friction coefficient of plastic films and sheets”.
  • the thickness of the primer layer may be measured by scanning electron microscopy (SEM).
  • the thickness of the first primer layer can be tested by the following steps: soak the positive electrode plate in DMC and bake it in an oven at 60°C to 80°C; select the area coated with the first primer layer and use ion polishing to perform cross-section processing on the positive electrode plate; spray gold on the cross section; take a cross-section image with SEM, and use the measurement tool provided by the software to measure the thickness of the single-layer coating at different positions (excluding the positive electrode current collector), wherein at least 3 positions are taken for each sample as the cross section, and at least 3 measurement points are taken for each cross section; calculate the average value to obtain the thickness of the first primer layer.
  • the thickness of the raised area in the second primer layer can be tested by the following steps: soak the positive electrode plate in DMC and then bake it in an oven at 60°C to 80°C; select the area coated with the second primer layer, and use ion polishing to perform cross-section processing on the positive electrode plate; spray gold on the cross section; take a cross-section image with SEM, and use the measurement tool provided by the software to measure the coating thickness of the raised area at different positions (excluding the positive electrode current collector), wherein at least 3 positions are taken for each sample as the cross section, and at least 3 raised area measurement points are taken for each cross section; calculate the average value to obtain the thickness of the raised area in the second primer layer.
  • the thickness of the concave area in the second primer layer can be tested by the following steps: soak the positive electrode plate in DMC and then bake it in an oven at 60°C to 80°C; select the area coated with the second primer layer, and use ion polishing to perform cross-section processing on the positive electrode plate; spray gold on the cross section; use SEM to take a cross-sectional view, and use the measurement tool provided by the software to measure the coating thickness of the concave area at different positions (excluding the positive electrode current collector), wherein at least 3 positions are taken for each sample as the cross section, and at least 3 concave area measurement points are taken for each cross section; calculate the average value to obtain the thickness of the concave area in the second primer layer.
  • the area ratio of the raised area in the second primer layer can be measured by SEM (scanning electron microscope).
  • SEM scanning electron microscope
  • a sample coated with the second primer layer is taken and placed in the field of view of the SEM for photography. Due to the high resolution of the SEM, the raised area can be identified and circled as a mark, and the area S1 of the circled raised area in the field of view is counted; the area of the field of view is calculated to obtain the area S0 of the second primer layer; S1 / S0 is calculated to obtain the area ratio of the raised area in the second primer layer.
  • the peel strength between the bottom coating and the positive electrode current collector has a well-known meaning in the art and can be measured by methods and instruments known in the art. For example, it can be measured by a high-speed rail tensile machine using a 90° angle method.
  • the lithium-ion secondary battery is mainly used as a specific example to illustrate the beneficial effects that can be achieved by the secondary battery according to the present application
  • the surface of the positive electrode collector includes a primer layer as described in the present application, and therefore when applied to other types of secondary batteries, the corresponding beneficial effects can also be achieved.
  • a second aspect of the present application provides an electrical device, which includes the secondary battery of the first aspect of the present application.
  • the electric device of the present application is not particularly limited, and it can be used for any electronic device known in the prior art.
  • the electric device can include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.
  • Fig. 17 is an example of an electric device, which may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • Graphite, binder styrene-butadiene rubber (SBR), conductive agent carbon black, and thickener sodium carboxymethyl cellulose (CMC-Na) are mixed in a mass ratio of 97.4:1.2:1.4, and an appropriate amount of solvent deionized water is added. After fully stirring, the negative electrode slurry is obtained; the negative electrode slurry is evenly coated on the two surfaces of the negative electrode current collector copper foil; and then dried in a 120°C oven, cold pressed, cut, etc. to obtain a negative electrode sheet.
  • Boehmite, polyacrylate, conductive agent carbon black, and other additives are mixed in a mass ratio of 92.5:5:2:0.5, and dispersed evenly in water to obtain a primer slurry;
  • the primer slurry is applied to both surfaces of the positive electrode current collector aluminum foil (only the tab welding area is exposed) according to a certain process so that the primer completely covers the surface of the primer, and dried in an oven at 80° C. to 150° C. to obtain a positive electrode current collector coated with a primer on both sides, wherein the thickness of the primer on one side is 3 ⁇ m;
  • the positive electrode active material lithium iron phosphate, the binder PVDF, and the conductive agent carbon black are mixed in a mass ratio of 97.5:1.3:1.2, and an appropriate amount of solvent NMP is added. After being fully stirred, additives are added and mixed to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the surface of the first primer layer on both sides of the positive electrode current collector; and then dried in an oven at 80°C to 150°C, cold pressed, cut, etc. to obtain a positive electrode sheet.
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent; LiPF 6 is dissolved in the organic solvent, and then fluoroethylene carbonate (FEC) is added and mixed uniformly to obtain an electrolyte.
  • the concentration of LiPF 6 is 1 mol/L, and the mass percentage of fluoroethylene carbonate is 5% based on the total mass of the electrolyte.
  • a porous polypropylene film (from Celgard Corporation) having a thickness of 14 ⁇ m was used as a separator.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in order so that the second primer layer is located at the outermost circle to obtain an electrode assembly.
  • the electrode assembly is placed in an outer package, and the above-mentioned electrolyte is added. After packaging, static formation, shaping and other processes, a secondary battery is obtained.
  • Example 2 Based on the preparation process of Example 1, the area ratio of the raised area in the second primer layer was adjusted as shown in Table 1 to prepare the positive electrode sheets of Examples 2 to 5. In Examples 2 to 5, the preparation of the negative electrode sheet, the positive electrode sheet, the electrolyte, the separator and the secondary battery was the same as that of Example 1.
  • Example 1 Based on the preparation process of Example 1, the preparation process of the primer layer was adjusted, and the primer layer at the tail of the positive electrode current collector and the area used to form the outermost circle of the electrode assembly by winding was thickened to form a second primer layer, and the positive electrode sheets of Examples 6 to 7 were prepared. In Examples 6 to 7, the preparation of the negative electrode sheet, the positive electrode sheet, the electrolyte, the separator and the secondary battery was the same as that of Example 1.
  • the thickness of the thinned area in the second primer layer was adjusted to prepare the positive electrode sheets of Examples 8 to 13. Among them, in the second primer layer of Example 13, the thickness of the thinned area was 0, indicating that the primer layer was hollowed out to expose the positive electrode collector in the concave area.
  • the preparation of the negative electrode sheet, positive electrode sheet, electrolyte, separator and secondary battery of Examples 8 to 13 is the same as that of Example 1.
  • the preparation process of the primer layer was adjusted to adjust the position of the thinned area in the second primer layer at the outermost circle of the electrode assembly to prepare the positive electrode sheets of Examples 14 to 16.
  • the preparation of the negative electrode sheets, positive electrode sheets, electrolytes, separators and secondary batteries of Examples 14 to 16 was the same as that of Example 1.
  • the position of the second primer layer is shown in Figure 4; in the electrode assembly of Example 15, the position of the second primer layer is shown in Figure 3; in the electrode assembly of Example 16, the position of the second primer layer is shown in Figure 2.
  • the second primer layer has different components from the first primer layer, and the second primer layer does not contain a conductive agent, wherein boehmite, polyacrylate, and other additives are mixed in a mass ratio of 94.5:5:0.5 and dispersed evenly in water to obtain a primer layer slurry.
  • the area ratio of the raised area in the second primer layer was adjusted as shown in Table 1 to prepare the positive electrode sheets of Comparative Examples 1 to 3.
  • the preparation of the negative electrode sheet, the positive electrode sheet, the electrolyte, the separator and the secondary battery was the same as that of Example 1.
  • Example 1 Based on the preparation process of Example 1, the preparation process of the primer layer was adjusted, and the primer layer was applied only on part of the surface of the aluminum foil so that the outermost circle of the electrode assembly did not have the primer layer, and the positive electrode sheet of Comparative Example 4 was prepared. The preparation of the negative electrode sheet, positive electrode sheet, electrolyte, separator and secondary battery of Comparative Example 4 was the same as that of Example 1.
  • Example 1 Based on the preparation process of Example 1, the preparation process of the primer layer was adjusted, and the primer layer was not thinned, so that the outermost circle of the electrode assembly had a primer layer with a uniform thickness, and the positive electrode sheet of Comparative Example 5 was prepared.
  • the preparation of the negative electrode sheet, positive electrode sheet, electrolyte, separator and secondary battery of Comparative Example 5 was the same as that of Example 1.
  • the concave region thickness d 1 ⁇ m, the convex region thickness d 2 ⁇ m, the ratio of the concave region thickness to the convex region thickness d 1 /d 2 , and the area ratio of the convex region to the second primer layer S 1 /S 0 are respectively as shown in Table 1.
  • d 1 , d 2 , and S 1 /S 0 can be measured by the method described in the specification of this application, which will not be described in detail here.
  • Discharge the secondary battery disassemble the battery and take out the positive electrode sheet, and soak the positive electrode sheet in DMC for 2 hours; then take out the positive electrode sheet and dry it at 60° C. for 4 hours, and then take out the positive electrode sheet after drying.
  • the friction coefficient ⁇ between the outermost ring of the electrode assembly and the inner wall of the shell is measured.
  • the specific process is as follows.
  • test is carried out in accordance with the provisions of the national standard GB 8897.4-2008, and the drop test pass rate is recorded in the form of "passed number/total test number".
  • the secondary battery according to the present application includes a second primer layer at the outermost circle of the electrode assembly, which can significantly reduce the risk of failure of the secondary battery due to falling, thereby improving the safety performance of the secondary battery.
  • Example 1 and Example 6 and Example 3 it can be seen that the second primer layer formed by thinning a portion of the primer layer and the primer layer formed by thickening a portion of the primer layer can both allow the outermost circle of the electrode assembly and the inner wall of the shell to have a higher friction coefficient, thereby improving the pass rate of the drop test of the secondary battery.
  • the pass rate of the drop test of the secondary battery can be significantly improved.
  • Example 3 It can be seen from Example 3 and Examples 15 to 17 that, in the two straight portions of the outermost circle of the electrode assembly, at least one of the straight portions is provided with a second primer layer, which can improve the pass rate of the drop test of the secondary battery.
  • the second primer layer is provided on both straight portions, the pass rate of the drop test of the secondary battery can be further improved.
  • the pass rates of the drop tests of the secondary batteries of Example 3 and Example 17 are equivalent, indicating that when the curved portion of the outermost circle of the electrode assembly is not squeezed, or the degree of squeezing is small, the area of the outermost circle of the electrode assembly with the second primer layer can be reduced, and the second primer layer is only provided on the two straight portions of the outermost circle of the electrode assembly to reduce the raw material cost of the secondary battery.
  • the second primer layer does not contain a conductive agent and its inorganic particle component content is high, the pass rate of the drop will be further improved.
  • the outermost ring of the electrode assembly of Comparative Example 4 is not provided with a primer layer, the friction coefficient between the outermost ring of the electrode assembly and the inner wall of the shell is small, and the pass rate of the drop test of the secondary battery is significantly lower than that of Examples 1 to 17.
  • the outermost ring of the electrode assembly of Comparative Example 5 is provided with a primer layer of uniform thickness, the friction coefficient between the outermost ring of the electrode assembly and the inner wall of the shell is still small, and thus, the pass rate of the drop test of the secondary battery is also lower than that of Examples 1 to 17.
  • Comparative Example 1 Although the outermost ring of the electrode assembly of Comparative Examples 1 to 3 is provided with a second primer layer having a raised area and a concave area, in Comparative Example 1, the area ratio of the raised area to the second primer layer is too small, and in Comparative Examples 2 to 3, the area ratio of the raised area to the second primer layer is too large. Therefore, in Comparative Examples 1 to 3, the friction coefficient between the outermost ring of the electrode assembly and the inner wall of the shell is still small, and the pass rate of the drop test of the secondary battery is also not ideal.

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Abstract

本申请公开了一种二次电池及用电装置。二次电池，包括电极组件，以及用于容纳电极组件的壳体；电极组件的正极极片包括：正极集流体，以及涂覆于正极集流体表面的底涂层，其中，沿电极组件卷绕方向，底涂层包括第一底涂层和第二底涂层，正极活性材料层位于第一底涂层的表面上，电极组件最外圈至少部分表面设置第二底涂层，且第二底涂层的表面上未设置正极活性材料层，第二底涂层上还设置有凸起区和内凹区，且凸起区在第二底涂层的面积占比为50％至80％。本申请能够提升二次电池的安全性能。

Description

二次电池及用电装置 技术领域
本申请属于电池技术领域，具体涉及一种二次电池及用电装置。
背景技术
以锂离子电池为代表的二次电池具有能量密度高、循环寿命长，以及无污染、无记忆效应等突出特点。作为清洁能源，二次电池的应用已由电子产品逐渐普及到电动汽车等大型装置领域，以适应环境和能源的可持续发展战略。由此，也对二次电池的安全性能提出了更高的要求。
因此，寻找合适的方法，以提升二次电池的安全性能，对二次电池的发展具有重要的意义。
发明内容
本申请的目的在于提供一种二次电池及用电装置，旨在提升二次电池的安全性能。
本申请的第一方面提供一种二次电池，包括电极组件，以及用于容纳电极组件的壳体。电极组件的正极极片包括：正极集流体，以及涂覆于正极集流体表面的底涂层。
其中，沿电极组件卷绕方向，底涂层包括第一底涂层和第二底涂层，正极活性材料层位于第一底涂层的表面上，第二底涂层设置于电极组件最外圈的至少部分表面上，且第二底涂层的表面上未设置正极活性材料层，第二底涂层上还设置有凸起区和内凹区，且凸起区在第二底涂层的面积占比为50％至80％。
并非意在受限于任何理论或解释，第二底涂层设置于电极组件的最外圈的至少部分表面上，相较于空白正极集流体，或者厚度一致的底涂层，第二底涂层具有更高的粗糙度，从而能够使得电极组件的最外圈与壳体内壁之间具有较大的的摩擦系数。由此，在二次电池发生跌落的情况下，电极组件不易与壳体发生相对滑动，从而能够减小电极组件为壳体的冲击作用，从而降低二次电池因发生跌落而失效的风险，进而提升二次电池的安全性能。此外，本申请通过将第二底涂层设置于电极组件的最外圈的至少部分表面上，即可降低二次电池因发生跌落而失效的风险。本申请的二次电池不仅工艺简单，而且无需在二次电池内部引入复杂的结构，大大降低了二次电池的加工难度和制造成本。由此，本申请的二次电池能够兼具高安全性能和高产能。
在任意实施方式中，凸起区在第二底涂层的面积占比为55％至70％。当凸起区在第二底涂层中的面积占比在上述合适的范围内时，能够使得第二底涂层兼具较高的粗糙度以及一定的机械强度。由此，电极组件的最外圈不仅能够与壳体内壁之间具有高摩擦系数，而且能够具有一定的强度。因此，在本申请的二次电池跌落时，电极组件不仅不 易与壳体发生相对滑动，而且能够承受一定的冲击力，从而能够进一步提升二次电池的安全性能。
在任意实施方式中，内凹区的厚度d 1与凸起区的厚度d 2之比为0～4/5。内凹区的厚度与凸起区的厚度之比在上述合适的范围内，能够在增大电极组件的最外圈与壳体内壁之间的摩擦系数的同时，使得第二底涂层具有较高的结构稳定性。由此，能够使得电极组件最外圈与壳体内壁之间保持较大的摩擦系数，从而降低二次电池发生跌落后失效的风险，进而提升二次电池的安全性能。
在任意实施方式中，内凹区的厚度d 1与凸起区的厚度d 2之比为1/3～4/5。内凹区的厚度与凸起区的厚度之比在上述合适的范围内，能够在增大电极组件的最外圈与壳体内壁之间的摩擦系数的同时，进一步提升第二底涂层的结构稳定性。由此，能够进一步降低二次电池发生跌落后失效的风险，从而进一步提升二次电池的安全性能。
在任意实施方式中，内凹区的厚度d 1为1μm至2.5μm。当内凹区的厚度在上述合适的范围内时，一方面，有利于降低第二底涂层的加工难度；另一方面有利于使得第二底涂层具有一定的机械强度，从而使得第二底涂层具有良好的结构稳定性；再一方面有利于二次电池保持高体积能量密度。由此，本申请的二次电池能够兼具高安全性能和高体积能量密度。
在任意实施方式中，电极组件的最外圈与壳体内壁的摩擦系数μ满足：0.35≤μ≤0.5。
在任意实施方式中，电极组件的最外圈与壳体内壁的摩擦系数μ满足：0.39≤μ≤0.45。
当电极组件的最外圈与壳体内壁的摩擦系数在上述合适的范围内时，能够显著降低二次电池发生跌落后失效的风险，从而有利于进一步提升二次电池的安全性能。
在任意实施方式中，凸起区由多个间隔设置的凸部组成，和/或内凹区由多个间隔设置的凹部组成。
在任意实施方式中，电极组件最外圈包括两个弯曲部和两个平直部，至少一个平直部表面设置第二底涂层，为了进一步增大摩擦面，也可以最外圈上都设置第二底涂层。由此，能够进一步提升二次电池的安全性能。
本申请的第二方面提供一种用电装置，包括本申请的二次电池。
本申请的用电装置包括本申请的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施方式。
图1是本申请一实施例的二次电池中电极组件的示意图。
图2是本申请另一实施例的二次电池中电极组件的示意图。
图3是本申请又一实施例的二次电池中电极组件的示意图。
图4是本申请再一实施例的二次电池中电极组件的示意图。
图5是本申请一实施例的二次电池中，正极极片的纵截面示意图。
图6是图5所示的正极极片的俯视图。
图7是本申请另一实施例的二次电池中，正极极片的纵截面示意图。
图8是图7所示的正极极片的俯视图。
图9是本申请一实施例的二次电池中第二底涂层的示意图。
图10是本申请另一实施例的二次电池中第二底涂层的示意图。
图11是本申请又一实施例的二次电池中第二底涂层的示意图。
图12是本申请再一实施例的二次电池中第二底涂层的示意图。
图13是本申请再一实施例的二次电池中第二底涂层的示意图。
图14是本申请再一实施例的二次电池中第二底涂层的示意图。
图15是本申请再一实施例的二次电池中第二底涂层的示意图。
图16是本申请再一实施例的二次电池中第二底涂层的示意图。
图17是本申请本申请的二次电池的实施例用作电源的用电装置的示意图。
附图标记说明：
10电极组件；100正极极片；110正极集流体；110a正极集流体表面；120a第一底涂层；120b第二底涂层；130正极活性材料层；01凸部；02凹部。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合实施例对本申请进行进一步详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本申请，并非为了限定本申请。
为了简便，本文仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
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”的含义是两种或两种以上。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述 范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
如背景技术所述，提高二次电池的安全性能对于二次电池的发展十分重要。
二次电池通常由电极组件以及用于容纳电极组件的外包装组成。常用的外包装，例如铝塑膜等，其内壁较为光滑。因此，电极组件与外包装内壁的摩擦力小，容易在外包装内发生窜动。在发生跌落时，电极组件容易与外包装发生相对运动，导致铝箔撕裂、顶封冲开、外包装角位破损，从而导致电池失效。
相关技术中，为提升电池的跌落测试通过率，通常会在电极组件和外包装之间设置双面胶，或利用胶水等将外包装内壁与电极组件粘接起来，以减少电极组件的窜动；或者对外包装进行增强处理，例如，在外包装铝箔上贴胶，以增加铝箔的局部强度；再或者在电极组件和外包装之间增加缓冲结构，以缓解电池跌落时电极组件对外包装的冲击力。但是，这些方法不仅成本高、难度大，而且对于二次电池安全性能的提升作用十分有限，不能满足人们的期望。
为了解决上述问题，发明人经深入思考与大量实验，提供了一种二次电池及用电装置，该二次电池的电极组件中包含特定的正极极片，能够使得二次电池具备高安全性能。
二次电池
本申请第一方面提供一种二次电池，包括其中发生电化学反应以将化学能与电能互相转化的任何装置。二次电池的具体实例可以包括所有种类的锂二次电池或钠二次电池。
本申请的二次电池包括电极组件，以及用于容纳电极组件的壳体。该电极组件可以由正极极片、负极极片和隔离膜可通过卷绕工艺制成。
电极组件的正极极片包括：正极集流体，以及涂覆于正极集流体表面的底涂层。
其中，沿电极组件卷绕方向，底涂层包括第一底涂层和第二底涂层，正极活性材料层位于第一底涂层的表面上，第二底涂层设置于电极组件最外圈的至少部分表面上，且第二底涂层的表面上未设置正极活性材料层，第二底涂层上还设置有凸起区和内凹区，且凸起区在第二底涂层的面积占比为50％至80％。例如，凸起区的面积可以占第二底涂层面积的50％，55％，60％，65％，70％，75％，80％，或处于以上任意数值所组成的范围内。
在本申请中，对壳体的具体实施例不作限定。壳体可以包括，但不限于本领域公知的、用于封装电极组件及电解液的壳体。在一些实施方式中，壳体可以是硬壳，例如硬塑料壳、铝壳、钢壳等，也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)中的至少一种。
在本申请中，对正极集流体的具体实施例不作限定。正极集流体可以是，但不限于金属箔片或复合集流体。作为金属箔片的示例，正极集流体可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等。
上述第二底涂层可以为与第一底涂层的组成基本相同的底涂层。在一些实施方式中，第二底涂层设置于电极组件最外圈至少的部分表面上，即第二底涂层可以全部覆盖电极组件最外圈，也可以覆盖电极组件最外圈的部分表面。图1是本申请的二次电池中，电极组件的一实施方式的示意图。如图1所示，该示例性的电极组件10中，电极组件10最外圈表面全部设置第二底涂层120b。另外，通常情况下电池在手机等产品内安装时，左右的圆弧面位置通常不受挤压，或受挤压程度很小，此位置摩擦系数的增加对跌落测试通过率改善有限，电极组件10最外圈包括两个弯曲部和两个平直部，至少一个平直部表面设置第二底涂层120b，因此图1的方案可以采用图2的结构，此外简化结构图3和图4的方案对跌落测试通过率也有明显的提升。
在一些实施方式中，在正极集流体的表面，第二底涂层和第一底涂层除焊接极耳区域之外的部分可以连续分布。
图5和图6是本申请的二次电池中，正极极片的一实施方式的示意图，该正极极片可与负极极片和隔离膜通过卷绕工艺制成电极组件。图5为该示例性的正极极片100的纵截面的示意图，图6为该示例性的正极极片100的俯视图。如图5和图6所示，正极极片100中，正极集流体110的表面设置有底涂层，底涂层包括第一底涂层120a以及第二底涂层120b。第二底涂层120b经卷绕后，可位于电极组件的最外圈。第一底涂层120a位于电极组件的正极极片的中段部位。可选地，第一底涂层120a可以延伸至正极极片的尾部，与第二底涂层120b相对设置。进一步可选地，第一底涂层120a还可以延伸至正极极片的卷绕起始端。正极活性材料层130位于第一底涂层120a的表面上。极耳可焊接在位于正极极片中段部位的正极集流体表面110a上。容易理解的，正极集流体表面110a可以为涂布时预留的、表面未涂布底涂层和正极活性材料层的空集流体表面，也可以为经连续涂布后，将正极活性材料层130和第一底涂层120a的部分区域镂空形成的空集流体表面。
图7和图8是本申请的二次电池中，正极极片的一实施方式的示意图，该正极极片可与负极极片和隔离膜通过卷绕工艺制成电极组件。图7为该示例性的正极极片100的纵截面的示意图，图8为该示例性的正极极片100的俯视图。如图7和图8所示，正极极片100中，正极集流体110的表面设置有底涂层，底涂层包括第一底涂层120a以及第二 底涂层120b。第二底涂层120b经卷绕后，可位于电极组件的最外圈。第一底涂层120a位于电极组件的正极极片的中段部位。可选地，第一底涂层120a可以延伸至正极极片的尾部，与第二底涂层120b相对设置。进一步可选地，第一底涂层120a还可以延伸至正极极片的卷绕起始端。正极活性材料层130位于第一底涂层120a的表面上。极耳可焊接在位于正极极片卷绕起始端的正极集流体表面110a上。容易理解的，正极集流体表面110a可以为涂布时预留的、表面未涂布底涂层和正极活性材料层的空集流体表面，也可以为经连续涂布后，将位于正极极片起始端的部分第一底涂层120a镂空形成的空集流体表面。
在本申请中，凸起区可以为第二底涂层中，厚度相对较大的区域。上述内凹区可以为第二底涂层中，厚度相对较小的区域。凸起区和内凹区可以交替分布。本申请对凸起区和内凹区的形成方式不作特别限定，无论凸起区和内凹区经由何种方式形成，只要使得第二底涂层包括厚度较大的凸起区以及厚度较小的内凹区，以使得电极组件的最外圈具有一定的粗糙度即可。作为一个示例，凸起区可以由部分底涂层加厚形成，内凹区可以由未经处理的部分底涂层、经减薄的部分底涂层或者经镂空的部分底涂层形成。作为另一个示例，凸起区可以由未经处理的底涂层形成，内凹区可以由经减薄的底涂层或者经镂空的底涂层形成。作为再一个示例，凸起区可以由经减薄的底涂层形成，内凹区可以由经减薄的底涂层或者经镂空的底涂层形成。
虽然机理尚不明确，发明人意外地发现，在正极集流体的表面涂覆上述第一底涂层和第二底涂层，能够简单、有效提升二次电池的安全性能。
具体地，并非意在受限于任何理论或解释，第二底涂层设置于电极组件的最外圈至少部分表面上，相较于空白正极集流体，或者厚度一致的底涂层，第二底涂层具有更高的粗糙度，从而能够使得电极组件的最外圈与壳体内壁之间具有较大的的摩擦系数。由此，在二次电池发生跌落的情况下，电极组件不易与壳体发生相对滑动，从而能够减小电极组件为壳体的冲击作用，从而降低二次电池因发生跌落而失效的风险，进而提升二次电池的安全性能。此外，本申请通过将第二底涂层设置于电极组件的最外圈的至少部分表面上，即可降低二次电池因发生跌落而失效的风险。本申请的二次电池不仅工艺简单，而且无需在二次电池内部引入复杂的结构，大大降低了二次电池的加工难度和制造成本。由此，本申请的二次电池能够兼具高安全性能和高产能。
在一些实施方式中，凸起区在第二底涂层的面积占比可为55％至70％。例如，凸起区的面积可占第二底涂层面积的55％，58％，60％，62％，65％，68％，70％，或处于以上任意数值所组成的范围内。
并非意在受限于任何理论或解释，当凸起区在第二底涂层中的面积占比在上述合适的范围内时，能够使得第二底涂层兼具较高的粗糙度以及一定的机械强度。由此，电极组件的最外圈不仅能够与壳体内壁之间具有高摩擦系数，而且能够具有一定的强度。因此，在本申请的二次电池跌落时，电极组件不仅不易与壳体发生相对滑动，而且能够承受一定的冲击力，从而能够进一步提升二次电池的安全性能。
在一些实施方式中，内凹区的厚度d 1与凸起区的厚度d 2之比为0～4/5。例如，内凹区的厚度d 1与凸起区的厚度d 2之比可以为0，1/5，1/4，1/3，2/5，1/2，3/5，2/3，3/4，4/5，或处于以上任意数值所组成的范围内。从正极集流体的表面向背离集流体表面 的垂直方向上，凸起区的厚度大于内凹区的厚度；内凹区的厚度d 1是指内凹区背离正极集流体的表面向正极集流体表面的垂直距离，凸起区的厚度d 2是指凸起区背离正极集流体的表面向正极集流体表面的垂直距离。
并非意在受限于任何理论或解释，内凹区的厚度与凸起区的厚度之比在上述合适的范围内，能够在增大电极组件的最外圈与壳体内壁之间的摩擦系数的同时，使得第二底涂层具有较高的结构稳定性。由此，能够使得电极组件最外圈与壳体内壁之间保持较大的摩擦系数，从而降低二次电池发生跌落后失效的风险，进而提升二次电池的安全性能。
在一些实施方式中，内凹区的厚度d 1与凸起区的厚度d 2之比为1/3～4/5。例如，内凹区的厚度d 1与凸起区的厚度d 2之比可以为1/3，1/2、2/3、3/5，2/3，3/4，4/5，或处于以上任意数值所组成的范围内。
并非意在受限于任何理论或解释，内凹区的厚度与凸起区的厚度之比在上述合适的范围内，能够在增大电极组件的最外圈与壳体内壁之间的摩擦系数的同时，进一步提升第二底涂层的结构稳定性。由此，能够进一步降低二次电池发生跌落后失效的风险，从而进一步提升二次电池的安全性能。
在一些实施方式中，内凹区的厚度d 1可为1μm至2.5μm。例如，内凹区的厚度d 1可以为1μm，1.2μm，1.5μm，1.8μm，2μm，2.2μm，2.5μm或处于以上任意数值所组成的范围内。
并非意在受限于任何理论或解释，当内凹区的厚度在上述合适的范围内时，一方面，有利于降低第二底涂层的加工难度；另一方面有利于使得第二底涂层具有较高的机械强度，从而使得第二底涂层具有良好的结构稳定性；再一方面有利于二次电池保持高体积能量密度。由此，本申请的二次电池能够兼具高安全性能和高体积能量密度。
在一些实施方式中，电极组件的最外圈与壳体内壁的摩擦系数μ可满足：0.35≤μ≤0.5。例如，μ可以为0.35，0.4，0.45，0.5，或处于以上任意数值所组成的范围内。
在一些实施方式中，电极组件的最外圈与壳体内壁的摩擦系数μ可满足：0.39≤μ≤0.45。例如，μ可以为0.39，0.40，0.41，0.42，0.43，0.44，0.45，或处于以上任意数值所组成的范围内。
并非意在受限于任何理论或解释，当电极组件的最外圈与壳体内壁的摩擦系数在上述合适的范围内时，能够显著降低二次电池发生跌落后失效的风险，从而有利于进一步提升二次电池的安全性能。
本申请对凸起区和内凹区的形状不作限制。在一些实施方式中，凸起区可由多个间隔设置的凸部组成。在一些实施方式中，内凹区可由多个间隔设置的凹部组成。作为一个示例，凸起区可以由部分底涂层加厚形成，这些的加厚区域可以形成间隔设置的多个凸部。作为另一个示例，内凹区可以由部分底涂层减薄形成，或者由部分底涂层镂空形成，这些的减薄或镂空区域可以形成间隔设置的多个凹部。作为再一个示例，第二底涂层中可以包括由部分底涂层加厚形成的多个凸部，以及由部分底涂层减薄或者由部分 底涂层镂空形成的多个凹部。多个凸部和多个凹部可以间隔设置，也可以分别连续设置于第二底涂层的不同区域。
在一些实施方式中，如图9、图10、图11或图12所示，凸起区可以由多个间隔设置的凸部01组成，内凹区可以由连续设置的凹部02组成。作为另一个示例，如图13所示，凸起区可以由多个间隔设置的凸部01组成，内凹区可以由多个间隔设置的凹部02组成。作为再一个示例，如图14、图15或图16所示，凸起区可以由多个连续设置的凸部01组成，内凹区可以由多个间隔设置的凹部02组成。
在一些实施方式中，电极组件最外圈包括两个弯曲部和两个平直部，至少一个平直部表面设置第二底涂层，为了进一步增大摩擦面，也可以最外圈上都设置第二底涂层。
在一些实施方式中，底涂层与正极集流体的剥离强度可不低于150N/m，例如可以为150N/m以上，200N/m以上，300N/m以上或400N/m以上。
并非意在受限于任何理论或解释，底涂层与正极集流体的剥离强度在上述较高的范围内，能够使得底涂层与正极集流体紧密地结合在一起，从而提升正极集流体的结构稳定性。由此，在二次电池发生针刺或收到机械撞击时，底涂层不易从正极集流体表面脱落而使得正极集流体裸露，从而能够降低正极集流体与负极接触而引发短路的概率。由此，能够进一步提升二次电池的安全性能。
本申请对底涂层的组成不作限制，能够实现本申请各实施方式所对应的技术方案即可。作为示例，底涂层中可包括无机颗粒，粘结剂，导电剂以及任选的助剂。作为示例，底涂层中也可以仅包括粘结剂，导电剂以及任选的助剂。作为示例，底涂层中，第二底涂层可包括无机颗粒，粘结剂，可选的导电剂以及任选的助剂。作为示例，底涂层中，第二底涂层也可以仅包括粘结剂，可选的导电剂以及任选的助剂。
无机颗粒可以选自本领域公知的、可用于底涂层的无机颗粒，例如，无机颗粒可选自勃姆石、水铝石、氧化铝、硫酸钡、碳酸钙、硅酸钙中的至少一者。可选地，无机颗粒可选自勃姆石和/或氧化铝。
粘结剂可以选自本领域公知的、可用于底涂层的粘结剂，例如，粘结剂可选自聚丙烯类粘结剂、聚丙烯酸酯类粘结剂、丙烯氰多元共聚物、羧甲基纤维素盐中的至少一种。可选地，粘结剂可以选自以丙烯酸腈、丙烯酸盐、丙烯酰胺、丙烯酸酯中一种或几种物质作为单体聚合得到的粘结剂。
导电剂可以选自本领域公知的、可用于底涂层的导电剂，例如，导电剂可选自导电碳黑(Super P)、碳纤维、石墨烯或碳纳米管(CNT)中的至少一种。
在一些实施方式中，以总质量为100％计，底涂层可包括50％至95％的无机颗粒、2％至50％的粘结剂以及0.5％至10％的导电剂。
在一些实施方式中，以总质量为100％计，以总质量为100％计，底涂层可包括50％至95％的无机颗粒、5％至50％的粘结剂以及0至2％的任选的其他助剂。该任选的其他助剂可以包括，但不限于流平剂或分散剂。
本申请的二次电池中，正极活性材料层的正极活性材料的具体种类不受到具体的限制，可根据需求进行选择。例如，正极活性材料可以包括锂过渡金属氧化物、橄榄石 结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。在本申请的二次电池中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
作为示例，锂过渡金属氧化物可以包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。作为示例，橄榄石结构的含锂磷酸盐可以包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其改性化合物中的一种或几种。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，正极活性材料层还可选地包括粘结剂。粘结剂的具体种类不受到具体的限制，可根据需求进行选择。作为示例，粘结剂包括但不限于聚偏氟乙烯(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，正极活性材料层还可选地包括导电剂。导电剂的具体种类不受到具体的限制，可根据需求进行选择。作为示例，导电剂包括但不限于导电石墨、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。
本申请中正极极片可以按照本领域常规方法制备。例如，将底涂层浆料涂布于正极集流体的表面，对底涂层的部分表面进行处理，以形成第二底涂层，从而得到表面具有第一底涂层和第二底涂层的正极集流体；正极活性材料层通常是将正极浆料涂布在正极集流体的第一底涂层的表面上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
本申请的二次电池中，负极极片的材料、构成和其制造方法可包括任何现有技术中公知的技术。
负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极活性材料。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的其中任意一者或两者上。
本申请对负极极片的负极集流体不作限定。可以使用金属箔材或多孔金属板，例如使用铜、镍、钛、铁等金属或它们的合金的箔材或多孔板。作为示例，负极集流体为铜箔。
负极活性材料的具体种类不受到具体的限制，可根据需求进行选择。作为示例，其他负极活性材料包括但不限于天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳，软碳、硅、硅-碳复合物、SiO、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的Li 4Ti 5O 12、Li-Al合金中的至少一种。
在一些实施方式中，负极活性材料层还可选地包括粘结剂。粘结剂的具体种类不受到具体的限制，可根据需求进行选择。作为示例，粘结剂包括但不限于丁苯橡胶(SBR)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、水性丙烯酸树脂(Water-based acrylic resin)及羧甲基纤维素中的至少一种。
在一些实施方式中，负极活性材料层还可选地包括导电剂。导电剂的具体种类不受到具体的限制，可根据需求进行选择。作为示例，导电剂包括但不限于导电石墨、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，负极活性材料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。
本申请中负极极片可以按照本领域常规方法制备。例如将负极活性材料，导电剂，粘结剂和增稠剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，形成均匀的负极浆料，将负极浆料涂覆在负极集流体上，经烘干、冷压等工序得到负极极片。
另外，本申请中的负极极片并不排除除了负极活性材料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包括夹在集流体和活性材料层之间、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包括覆盖在负极活性材料层表面的保护层。
本申请的二次电池中，隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯、聚偏氟乙烯中的一种或几种，但不仅限于这些。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。在一些实施方式中，隔离膜上还可以设置陶瓷涂层、金属氧化物涂层。
本申请的二次电池还可以包括电解液。电解液在正极极片和负极极片之间起到传导活性离子的作用。可用于本申请二次电池的电解液可以为现有技术已知的电解液。
在一些实施方式中，电解液包括有机溶剂、锂盐和可选的添加剂，有机溶剂、锂盐和添加剂的种类均不受到具体的限制，可根据需求进行选择。
在一些实施方式中，作为示例，锂盐包括但不限于LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、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)中的至少一种。上述锂盐可以单独使用一种，也可以同时使用两种或两种以上。
在一些实施方式中，作为示例，有机溶剂包括但不限于碳酸亚乙酯(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)中的至少一种。上述有机溶剂可以单独使用一种，也可以同时使用两种或两种以上。可选地，上述有机溶剂同时使用两种或两种以上。
在一些实施方式中，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。
作为示例，添加剂包括但不限于氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、乙烯基碳酸乙烯酯(VEC)、硫酸乙烯酯(DTD)、硫酸丙烯酯、亚硫酸乙烯酯(ES)、1,3-丙磺酸内酯(PS)、1,3-丙烯磺酸内酯(PST)、磺酸酯环状季铵盐、丁二酸酐、丁二腈(SN)、己二腈(AND)、三(三甲基硅烷)磷酸酯(TMSP)、三(三甲基硅烷)硼酸酯(TMSB)中的至少一种。
电解液可以按照本领域常规的方法制备。例如，可以将有机溶剂、锂盐、可选的添加剂混合均匀，得到电解液。各物料的添加顺序并没有特别的限制，例如，将锂盐、可选的添加剂加入到有机溶剂中混合均匀，得到电解液；或者，先将锂盐加入有机溶剂中，然后再将可选的添加剂加入有机溶剂中混合均匀，得到电解液。
在本申请中，电极组件的最外圈与壳体内壁的摩擦系数可参照测试标准GB/T10006-2021《塑料薄膜和薄片摩擦系数的测定方法》测定。
在本申请中，底涂层的厚度可以通过扫描电子显微镜(SEM)测定。
作为一个示例，第一底涂层的厚度可通过如下步骤测试：将正极极片经过DMC浸泡后，经烘箱于60℃至80℃烘烤；选取涂覆有第一底涂层的区域，使用离子抛光对正极极片进行截面处理；对截面进行喷金；用SEM拍摄截面图，用软件自带的测量工具测量不同位置的单层涂层厚度(不包括正极集流体)，其中，每个样品至少取3个位置作截面，每个截面至少取3个测量点；计算平均值，得到第一底涂层的厚度。
作为另一个示例，第二底涂层中，凸起区的厚度可通过如下步骤测试：将正极极片经过DMC浸泡后，经烘箱于60℃至80℃烘烤；选取涂覆有第二底涂层的区域，使用离子抛光对正极极片进行截面处理；对截面进行喷金；用SEM拍摄截面图，用软件自带的测量工具测量不同位置的凸起区涂层厚度(不包括正极集流体)，其中，每个样品至少取3个位置作截面，每个截面至少取3个凸起区测量点；计算平均值，得到第二底涂层中凸起区的厚度。
作为再一个示例，第二底涂层中，内凹区的厚度可通过如下步骤测试：将正极极片经过DMC浸泡后，经烘箱于60℃至80℃烘烤；选取涂覆有第二底涂层的区域，使用离子抛光对正极极片进行截面处理；对截面进行喷金；用SEM拍摄截面图，用软件自带的测量工具测量不同位置的内凹区涂层厚度(不包括正极集流体)，其中，每个样品至少取3个位置作截面，每个截面至少取3个内凹区测量点；计算平均值，得到第二底涂层中内凹区的厚度。
在本申请中，凸起区在第二底涂层的面积占比可以采用SEM(扫描电子显微镜)测量，作为一个示例，取涂覆有第二底涂层的样品，置于SEM视野区域内拍摄，由于SEM分辨率高，可识别出凸起区并圈起来作为标记，统计视野区域内被圈起的凸起区面积S 1；计算视野区域面积，即得到第二底涂层的面积S 0；计算S 1/S 0，得到凸起区在第二底涂层的面积占比。
本申请中底涂层与正极集流体的剥离强度具有本领域公知的含义，可采用本领域 公知的方法和仪器测定，例如，可以通过高铁拉力机，采用90°角法测定。
需要说明的是，上述针对正极集流体或底涂层的各种参数测试，可以在电池制备过程中取样测试，也可以从制备好的二次电池中取样测试。
当上述测试样品是从制备好的二次电池中取样时，作为示例，可以按如下步骤：将二次电池做放电处理(为了安全起见，一般使电池处于满放状态)；将电池拆卸后取出正极极片，使用碳酸二甲酯(DMC)将正极极片浸泡一定时间(例如2至10小时)；然后将正极极片取出并在一定温度和时间下干燥处理(例如60℃，4小时)，干燥后取出正极极片。此时即可以在干燥后的正极极片中取样测试本申请上述的正极集流体或底涂层相关的各参数。
虽然在上面关于二次电池的实施例的描述中，主要以锂离子二次电池为具体示例说明了根据本申请的二次电池能够实现的有益效果，但是本领域技术人员容易理解，根据本申请的二次电池中，正极集流体表面包含如本申请的底涂层，因此应用于其它类型的二次电池中时，同样能够实现相应的有益效果。
用电装置
本申请第二方面提供了一种用电装置，其包括本申请第一方面的二次电池。
本申请的用电装置没有特别限定，其可以是用于现有技术中已知的任何电子设备。在一些实施方式中，用电装置可以包括但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
图17是作为一个示例的用电装置。该用电装置可以为纯电动车、混合动力电动车、或插电式混合动力电动车等。
实施例
下述实施例更具体地描述了本发明公开的内容，这些实施例仅仅用于阐述性说明，因为在本发明公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
负极极片的制备
将石墨、粘结剂丁苯橡胶(SBR)、导电剂炭黑、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比97.4:1.2:1.4进行混合，加入适量的溶剂去离子水，充分搅拌均匀后得到负极浆料；将负极浆料均匀涂覆在负极集流体铜箔的两个表面上；然后经过120℃烘箱干燥、冷压、分切等，得到负极极片。
正极极片的制备
将勃姆石、聚丙烯酸酯、导电剂炭黑、其他助剂按质量比92.5:5:2:0.5混合后，于 水中分散均匀，得到底涂层浆料；
将底涂层浆料按照一定的工艺涂布于正极集流体铝箔的两个表面(仅露出极耳焊接区)，以使得底涂层完全覆盖底涂层的表面，在80℃至150℃的烘箱中烘干，得到双面涂覆底涂层的正极集流体，其中，单面底涂层的厚度为3μm；
对正极集流体尾部、用于经卷绕形成电极组件最外圈的区域的部分底涂层作减薄处理，以形成第二底涂层，除第二底涂层外的底涂层为第一底涂层；
将正极活性材料磷酸铁锂、粘结剂PVDF、导电剂炭黑按照质量比97.5:1.3:1.2进行混合，加入适量的溶剂NMP，充分搅拌均匀后，加入添加剂，混合均匀后得到正极浆料；将正极浆料均匀涂覆在正极集流体两侧第一底涂层的表面上；然后经80℃～150℃烘箱干燥、冷压、分切等，得到正极极片。
电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)及碳酸二乙酯(DEC)按照体积比为1:1:1进行混合，得到有机溶剂；将LiPF 6溶解在上述有机溶剂中，再加入氟代碳酸乙烯酯(FEC)混合均匀，得到电解液。其中，LiPF 6的浓度为1mol/L，基于电解液的总质量，氟代碳酸乙烯酯的质量百分含量为5％。
隔离膜的制备
采用厚度为14μm的多孔聚丙烯膜(来自Celgard公司)作为隔离膜。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，以使第二底涂层位于最外圈，得到电极组件，将电极组件放入外包装中，加入上述电解液，经封装、静置化成、整形等工序后，得到二次电池。
实施例2至5
基于实施例1的制备过程，根据表1中所示，调整第二底涂层中凸起区的面积占比，制备实施例2至5的正极极片。实施例2至5中，负极极片、正极极片、电解液、隔离膜及二次电池的制备与实施例1相同。
实施例6至7
基于实施例1的制备过程，调整底涂层的制备工艺，对正极集流体尾部、用于经卷绕形成电极组件最外圈的区域的部分底涂层作加厚处理，以形成第二底涂层，制备得到实施例6至7的正极极片。实施例6至7中，负极极片、正极极片、电解液、隔离膜及二次电池的制备与实施例1相同。
实施例8至13
基于实施例1的制备过程，调整第二底涂层中减薄区域的厚度，制备实施例8至13的正极极片。其中，实施例13的第二底涂层中，减薄区域的厚度为0，表示对底涂层进行镂空处理，以在内凹区露出正极集流体。实施例8至13的负极极片、正极极片、电解液、隔离膜及二次电池的制备与实施例1相同。
实施例14至16
基于实施例1的制备过程，调整底涂层的制备工艺，以调整第二底涂层中减薄区域在电极组件最外圈的位置，制备实施例14至16正极极片。实施例14至16的负极极片、 正极极片、电解液、隔离膜及二次电池的制备与实施例1相同。其中，实施例15的电极组件中，第二底涂层的位置如图4所示；实施例15的电极组件中，第二底涂层的位置如图3所示；实施例16的电极组件中，第二底涂层的位置如图2所示。
实施例17
基于实施例1的制备过程，第二底涂层与第一底涂层组分不同，第二涂层不含导电剂，其中勃姆石、聚丙烯酸酯、其他助剂按质量比94.5:5:0.5混合后，于水中分散均匀，得到底涂层浆料。
对比例1至3
基于实施例1的制备过程，根据表1中所示，调整第二底涂层中凸起区的面积占比，制备对比例1至3的正极极片。对比例1至3中，负极极片、正极极片、电解液、隔离膜及二次电池的制备与实施例1相同。
对比例4
基于实施例1的制备过程，调整底涂层的制备工艺，仅在铝箔的部分表面涂布底涂层，以使得电极组件的最外圈不具有底涂层，制备对比例4的正极极片。对比例4的负极极片、正极极片、电解液、隔离膜及二次电池的制备与实施例1相同。
对比例5
基于实施例1的制备过程，调整底涂层的制备工艺，不对底涂层作减薄处理，以使得电极组件的最外圈具有厚度一致的底涂层，制备对比例5的正极极片。对比例5的负极极片、正极极片、电解液、隔离膜及二次电池的制备与实施例1相同。
各实施例及对比例中，内凹区厚度d 1μm、凸起区厚度d 2μm、内凹区厚度与凸起区厚度之比d 1/d 2、凸起区在第二底涂层的面积占比S 1/S 0分别如表1中所示。其中，d 1、d 2、S 1/S 0可通过本申请说明书记载的方法测得，在此不加以赘述。
测试部分
将二次电池做放电处理；将电池拆卸后取出正极极片，使用DMC将正极极片浸泡2小时；然后将正极极片取出并在60℃进行4小时的干燥处理，干燥后取出正极极片。
对上述正极极片，以及各实施例及对比例的二次电池进行如下测试，测试结果分别如表1中所示。
(1)摩擦系数μ的测试
参照GB/T 10006-2021《塑料薄膜和薄片摩擦系数的测定方法》，测定电极组件的最外圈与壳体内壁的摩擦系数μ。具体流程如下。
裁切长度200±5mm、宽度80±2mm的包装铝膜并平贴在测试平台表面，并使用胶带固定；选取正极极片中，对应形成电极组件最外圈的部分，裁切长度为63±5mm、宽度93±2mm的试件；在总质量为200g±2g(以产生F P＝1.96N±0.02N的法向力)、面积为40cm 2的正方形(边长63mm)滑块底部粘贴双面胶，并将试件的非测试面(即，试件中不用于形成电极组件最外圈的表面)紧固在滑块上；将贴有试件滑块放置在贴有包装铝膜测试平台表面，以使试件的测试面(即，试件中位于电极组件最外圈的第二底涂层表面)与铝膜接触；驱动机构使滑块与铝膜以100mm/min拖动，测量在滑动的最初6cm的平均力，记为F D；电极组件的最外圈与壳体内壁的摩擦系数μ＝F D/F P(其中FP＝1.96N， 即总质量为200g±2g滑块产生的法向力)。
(2)二次电池的跌落测试
参照国标GB 8897.4-2008的规定进行测试，以“通过数量/总测试数量”方式记录跌落测试通过率。
在表1中，“/”表示未进行相应的处理，或相应的参数无法测得。
表1
序号 d 1/μm d 2/μm d 1/d 2 S 1/S 0 摩擦系数μ 跌落测试通过率
实施例1 2 3 2/3 0.5 0.38 16/20P
实施例2 2 3 2/3 0.55 0.42 17/20P
实施例3 2 3 2/3 0.6 0.42 17/20P
实施例4 2 3 2/3 0.7 0.41 17/20P
实施例5 2 3 2/3 0.8 0.37 16/20P
实施例6 3 4.5 2/3 0.5 0.35 15/20P
实施例7 3 4.5 2/3 0.6 0.35 15/20P
实施例8 2.4 3 4/5 0.6 0.39 17/20P
实施例9 1.5 3 1/2 0.6 0.43 18/20P
实施例10 1.2 3 2/5 0.6 0.43 18/20P
实施例11 1 3 1/3 0.6 0.44 17/20P
实施例12 0.7 3 1/4 0.6 0.44 15/20P
实施例13 0 3 0 0.6 0.45 14/20P
实施例14 2 3 2/3 0.6 0.42 14/20P
实施例15 2 3 2/3 0.6 0.42 15/20P
实施例16 2 3 2/3 0.6 0.42 17/20P
实施例17 2 3 2/3 0.6 0.42 18/20P
对比例1 2 3 2/3 0.4 0.33 13/20P
对比例2 2 3 2/3 0.9 0.33 13/20P
对比例3 2 3 2/3 0.95 0.33 13/20P
对比例4 / / / / 0.21 4/20
对比例5 / / / / 0.28 10/20
综合表1可知，根据本申请的二次电池在电极组件的最外圈包括第二底涂层，能够显著降低二次电池因发生跌落而失效的风险，从而提升二次电池的安全性能。
具体地，综合实施例1至5的测试结果可知，保持内凹区厚度与凸起区厚度不变时，随着凸起区在第二底涂层的面积占比增大，电极组件最外圈与壳体内壁的摩擦系数呈先增大后减小的趋势。当凸起区在第二底涂层的面积占比在本申请的范围内时，均能够提升二次电池的跌落测试通过率。
综合实施例1和实施例6、实施例7和实施例3可知由部分底涂层减薄形成的第二底涂层和由部分底涂层加厚形成的底涂层均能够使得电极组件最外圈与壳体内壁具有较高的的摩擦系数，从而提升二次电池的跌落测试通过率。
综合实施例3、实施例8至12可知，对于由部分底涂层减薄形成的第二底涂层，随着内凹区厚度的减小，电极组件最外圈与壳体内壁的摩擦系数大体上呈增大的趋势。由实施例13的测试结果可知，由部分底涂层镂空形成的第二底涂层也能够使得电极组件最外圈与壳体内壁具有较高的摩擦系数，但底涂层减薄形成的内凹区，一定程度上降低了底涂层厚度对铝箔强度的加强效果，所以随着内凹程度增加，摩擦系数虽然增加了，但底涂层对铝箔的强化效果降低，跌落过程中铝箔撕裂风险增加，跌落的通过率降低。当内凹区厚度在合适的范围内时，二次电池的跌落测试通过率能够得到显著提升。
综合实施例3、实施例15至17可知，在电极组件最外圈的两个平直部中，至少一个平直部设置第二底涂层，即可提升二次电池的跌落测试通过率。当两个平直部均设置第二底涂层时，二次电池的跌落测试通过率能够得到进一步提升。实施例3与实施例17的二次电池的跌落测试通过率相当，说明在电极组件最外圈的弯曲部不受挤压，或受挤压程度较小时，可减少电极组件最外圈设置有第二底涂层的区域，仅在电极组件最外圈的两个平直部设置第二底涂层，以降低二次电池的原料成本，此外通过实施例3和实施例18可知，当第二底涂层不含导电剂，其无机颗粒的组分含量较多时，跌落的通过率会进一步提升，这是由于无机颗粒含量增加，会增强电极组件最外圈的强度，同时不含导电剂，第二底涂层绝缘，避免在跌落过程中防止金属碎屑进入电极组件内部，导致短路。
而相对于此，对比例4的电极组件最外圈未设置底涂层，电极组件最外圈与壳体内壁的摩擦系数较小，二次电池的跌落测试通过率明显低于实施例1至17。对比例5的电极组件最外圈虽然设置了厚度一致的底涂层，但是电极组件最外圈与壳体内壁的摩擦系数仍然较小，由此，二次电池的跌落测试通过率也低于实施例1至17。对比例1至3的电极组件最外圈虽然设置了具有凸起区和内凹区的第二底涂层，但是对比例1中，凸起区在第二底涂层的面积占比过小，对比例2至3中，凸起区在第二底涂层的面积占比过大。由此，对比例1至3中，电极组件最外圈与壳体内壁的摩擦系数仍然较小，二次电池的跌落测试通过率也不理想。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (10)

  1. 一种二次电池，包括电极组件，以及用于容纳所述电极组件的壳体；
    所述电极组件的正极极片包括：
    正极集流体，以及涂覆于所述正极集流体表面的底涂层，
    其中，沿所述电极组件的卷绕方向，所述底涂层包括第一底涂层和第二底涂层，正极活性材料层位于所述第一底涂层的表面上，所述第二底涂层设置于所述电极组件最外圈的至少部分表面上，且所述第二底涂层的表面上未设置所述正极活性材料层，所述第二底涂层上还设置有凸起区和内凹区，且所述凸起区在所述第二底涂层的面积占比为50％至80％。
  2. 根据权利要求1所述的二次电池，其中，所述凸起区的面积在所述第二底涂层的面积占比为55％至70％。
  3. 根据权利要求1所述的二次电池，其中，所述内凹区的厚度d 1与所述凸起区的厚度d 2之比为0～4/5。
  4. 根据权利要求1所述的二次电池，其中，所述内凹区的厚度d 1与所述凸起区的厚度d 2之比为1/3～4/5
  5. 根据权利要求1所述的二次电池，所述内凹区的厚度d 1为1μm至2.5μm。
  6. 根据权利要求1所述的二次电池，所述电极组件的最外圈与所述壳体内壁的摩擦系数μ满足：0.35≤μ≤0.5。
  7. 根据权利要求6所述的二次电池，所述电极组件的最外圈与所述壳体内壁的摩擦系数μ满足：0.39≤μ≤0.45。
  8. 根据权利要求1所述的二次电池，所述凸起区由多个间隔设置的凸部组成，和/或所述内凹区由多个间隔设置的凹部组成。
  9. 根据权利要求1所述的二次电池，其中，所述电极组件最外圈包括两个弯曲部和两个平直部，至少一个所述平直部表面设置所述第二底涂层。
  10. 一种用电装置，包括根据权利要求1至9中任一项所述的二次电池。
PCT/CN2022/140954 2022-12-22 2022-12-22 二次电池及用电装置 Ceased WO2024130626A1 (zh)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119069831A (zh) * 2024-11-04 2024-12-03 中创新航科技集团股份有限公司 电芯及电池及电池模组
CN120072953A (zh) * 2025-04-25 2025-05-30 苏州臻锂新材科技有限公司 一种复合集流体及其制备方法和二次电池
WO2026007067A1 (zh) * 2024-07-04 2026-01-08 宁德新能源科技有限公司 电极组件、二次电池和电子装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN205985209U (zh) * 2016-09-20 2017-02-22 东莞新能源科技有限公司 一种电芯及二次电池
CN206532840U (zh) * 2016-12-27 2017-09-29 宁德新能源科技有限公司 一种卷绕式电芯
KR20190055994A (ko) * 2017-11-16 2019-05-24 삼성에스디아이 주식회사 이차 전지
CN115066767A (zh) * 2021-03-23 2022-09-16 珠海冠宇电池股份有限公司 一种正极片和锂离子电池

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101308260B1 (ko) * 2007-09-17 2013-09-13 삼성에스디아이 주식회사 이차전지
DE102011088739A1 (de) * 2011-12-15 2013-06-20 Robert Bosch Gmbh Gehäuse für eine Batteriezelle mit einer Lackbeschichtung zur elektrischen Isolation, Batteriezelle, Batterie sowie Kraftfahrzeug

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN205985209U (zh) * 2016-09-20 2017-02-22 东莞新能源科技有限公司 一种电芯及二次电池
CN206532840U (zh) * 2016-12-27 2017-09-29 宁德新能源科技有限公司 一种卷绕式电芯
KR20190055994A (ko) * 2017-11-16 2019-05-24 삼성에스디아이 주식회사 이차 전지
CN115066767A (zh) * 2021-03-23 2022-09-16 珠海冠宇电池股份有限公司 一种正极片和锂离子电池

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4636899A4 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2026007067A1 (zh) * 2024-07-04 2026-01-08 宁德新能源科技有限公司 电极组件、二次电池和电子装置
CN119069831A (zh) * 2024-11-04 2024-12-03 中创新航科技集团股份有限公司 电芯及电池及电池模组
CN120072953A (zh) * 2025-04-25 2025-05-30 苏州臻锂新材科技有限公司 一种复合集流体及其制备方法和二次电池

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