CN115172661B - Pole piece, electrode component, battery monomer, battery and power consumption device - Google Patents

Pole piece, electrode component, battery monomer, battery and power consumption device Download PDF

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Publication number
CN115172661B
CN115172661B CN202211050694.0A CN202211050694A CN115172661B CN 115172661 B CN115172661 B CN 115172661B CN 202211050694 A CN202211050694 A CN 202211050694A CN 115172661 B CN115172661 B CN 115172661B
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China
Prior art keywords
battery
pole piece
electrode assembly
active material
present application
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CN115172661A (en
Inventor
武新战
王欣
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Jiangsu Contemporary Amperex Technology Ltd
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Jiangsu Contemporary Amperex Technology Ltd
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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
    • H01M4/13—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
    • 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
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The application provides a pole piece, electrode subassembly, battery monomer, battery and power consumption device, and this pole piece includes mass flow body and active substance layer. The active material layer includes a first portion and a second portion applied to the surface of the current collector, the first portion having a lower compaction density than the second portion. In the pole piece provided by the embodiment of the application, the active material layer comprises a first part and a second part coated on the surface of the current collector, and the compaction density of the first part is smaller than that of the second part. When the pole piece is applied to a battery, along with the increase of the cycle number of the battery, the compaction density of the first part is smaller than that of the second part, so that the expansion of the pole piece can be effectively relieved, the extrusion between the pole pieces in the battery is reduced, the pole piece is favorably soaked by electrolyte, and the cycle performance of the battery is improved.

Description

Pole piece, electrode component, battery monomer, battery and power consumption device
Technical Field
The application relates to the technical field of batteries, in particular to a pole piece, an electrode assembly, a battery monomer, a battery and an electric device.
Background
The battery has the advantages of high energy density, good cycle performance, repeated charge and discharge, high safety performance and the like, so that the battery is widely applied to various fields of electronic equipment, power equipment and the like. Among them, the cycle performance of the battery has been one of the major points of research in the industry. As the requirements of each field for the cycle performance of the battery become higher, it is urgently needed to improve the cycle performance of the battery to meet the requirements of each field.
Disclosure of Invention
The application provides a pole piece, electrode subassembly, battery monomer, battery and power consumption device can improve the cycle performance of battery.
In a first aspect, an embodiment of the present application provides a pole piece, including a current collector and an active material layer. The active material layer includes a first portion and a second portion applied to the surface of the current collector, the first portion having a lower compaction density than the second portion.
In the pole piece provided by the embodiment of the application, the active material layer comprises a first part and a second part which are coated on the surface of the current collector, and the compaction density of the first part is smaller than that of the second part. When the pole piece is applied to a battery, along with the increase of the cycle number of the battery, the compaction density of the first part is smaller than that of the second part, so that the expansion of the pole piece can be effectively relieved, the extrusion between the pole pieces in the battery is reduced, the pole piece is favorably soaked by electrolyte, and the cycle performance of the battery is improved.
In some embodiments of the present application, the first portion has a compacted density of 1.35g/cm 3 -2.10g/cm 3 Within the range; and/or the second part has a compacted density of 2.25g/cm 3 -2.60g/cm 3 Within the range. Setting the compacted density of the first portion and the compacted density of the second portion within the above-described appropriate ranges may contribute to improving the energy density of the battery while improving the cycle performance of the battery.
In some embodiments of the present application, the first portion has an active material capacity per unit area that is less than the active material capacity per unit area of the second portion. Thus, the CB value of the first part can be increased, and the occurrence of the lithium extraction phenomenon of the electrode plate can be reduced.
In some embodiments of the present application, the first portion comprises a first active material and the second portion comprises a second active material. Wherein a weight ratio W1 of the first active material to the first portion to a weight ratio W2 of the second active material to the second portion satisfies the following relationship: 0.6W2W 1 not less than 0.8W2. The weight ratio W1 of the first active material to the first part and the weight ratio W2 of the second active material to the second part satisfy the above-described relationship, and can contribute to an increase in the CB value of the first part.
In some embodiments of the present application, the weight ratio W1 of the first active substance to the first part is 0.15g/1540.25mm 2 -0.28g/1540.25mm 2 Within the range. The weight ratio W2 of the second active substance to the second part is 0.25g/1540.25mm 2 -0.40g/1540.25mm 2 Within the range. W1 and W2 are set within the above-mentioned suitable ranges so that the first portion has a suitable CB value to further contribute to the reduction of the occurrence of the lithium-evolving phenomenon of the electrode.
In some embodiments of the present application, the porosity of the first portion is greater than the porosity of the second portion. The electrolyte storage capacity of the first part can be enhanced, so that the infiltration of the electrolyte to the pole piece is enhanced.
In some embodiments of the present application, the first portion is strip-shaped, and the width of the first portion is in the range of 2mm-10 mm. The width of the first part is set in the proper range, which is helpful for storing a proper amount of electrolyte to reduce the phenomenon of lithium precipitation, thereby being beneficial to relieving the expansion of the pole piece. Further, setting the width of the first portion within the above-described appropriate range also helps the battery to maintain a high energy density.
In some embodiments of the present application, the pole piece includes a plurality of the first portions arranged at intervals, and the second portion is connected between two adjacent first portions. The first parts arranged at intervals can further relieve the expansion of the pole piece and can also help to promote the infiltration of electrolyte on the pole piece.
In some embodiments of the present application, a pitch between adjacent two of the first portions in an arrangement direction of the plurality of the first portions is in a range of 40mm to 100 mm. The distance between two adjacent first parts is set in the proper range, so that the pole piece can be favorably soaked by the electrolyte, and the battery can be further favorably kept at a high energy density.
In a second aspect, an embodiment of the present application provides an electrode assembly, including a first pole piece and a second pole piece with opposite polarities, where the first pole piece is the pole piece described in any one of the above embodiments. Since the electrode assembly includes the electrode plate in any embodiment of the first aspect of the present application, the electrode assembly has the technical effects of the electrode plate, which are not described herein again.
In some embodiments of the present application, the first and second pole pieces are wound in a winding direction, and at least part of the first portion is disposed at an inner end of the current collector in the winding direction. The provision of at least part of the first portion can help to reduce the stress to which the centre of winding is subjected.
In some embodiments of the present application, the electrode assembly is cylindrical. Because the electrode assembly comprises the pole piece in any embodiment of the first aspect of the application, the pole piece can reduce the occurrence of the central area collapse of the electrode assembly, thereby improving the cycle performance of the battery.
In some embodiments of the present application, the first pole piece is a positive pole piece. This can help to reduce the swelling of the second pole piece and promote the infiltration of the electrolyte to the first and second pole pieces.
In a third aspect, embodiments of the present application provide a battery cell including a case, an electrode assembly, and an electrolyte. The housing has a receiving cavity. An electrode assembly is disposed in the receiving cavity, and the electrode assembly is the electrode assembly described in any of the above embodiments. An electrolyte is contained in the containing cavity and infiltrates the electrode assembly. Since the battery cell includes the electrode assembly in any one of the embodiments described above, the battery cell has good cycle performance.
In a fourth aspect, embodiments of the present application provide a battery, including a battery cell as described in any of the above embodiments. Since the battery includes the battery cell in any of the above embodiments, the battery has the technical effects of the battery cell, and details are not repeated herein.
In a fifth aspect, embodiments of the present application provide an electric device, including the battery described in the above embodiments.
The foregoing description is only an overview of the technical solutions of the present application, and the present application can be implemented according to the content of the description in order to make the technical means of the present application more clearly understood, and the following detailed description of the present application is given in order to make the above and other objects, features, and advantages of the present application more clearly understandable.
Drawings
Various additional advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Moreover, like reference numerals are used to refer to like elements throughout. In the drawings:
fig. 1 is a schematic structural diagram of a vehicle according to some embodiments of the present application.
Fig. 2 illustrates an exploded view of a battery provided by some embodiments of the present application.
Fig. 3 illustrates an exploded view of a battery cell provided by some embodiments of the present application.
Fig. 4 is a schematic cross-sectional view illustrating an electrode assembly in a battery cell according to some embodiments of the present disclosure.
Fig. 5 is a schematic cross-sectional view illustrating an electrode assembly in a battery cell according to further embodiments of the present disclosure.
Fig. 6 illustrates a schematic top view structure diagram of a pole piece according to some embodiments of the present application.
Fig. 7 illustrates a schematic top view structure diagram of a pole piece according to some embodiments of the present disclosure.
Fig. 8 is a schematic diagram illustrating a top view structure of a pole piece according to still other embodiments of the present application.
Fig. 9 shows a graph of the change in the cycle number and the capacity retention rate of the battery cells in example 1 and comparative example 1 of the present application.
Fig. 10 shows a schematic top view of some prior art electrode assemblies after 600 cycles.
Figure 11 illustrates a schematic top view of an electrode assembly after 600 cycles in some embodiments of the present application.
The reference numbers in the detailed description are as follows:
1000-a vehicle;
100-battery, 200-controller, 300-motor;
10-box, 11-first box, 12-second box;
20-a battery cell;
21-a housing;
22-electrode assembly, 222-first pole piece, 223-second pole piece, 224-separator, 225-via;
23-end caps;
221-pole piece, 2211-current collector, 2212-active material layer, 2212 a-first portion, 2212 b-second portion.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are merely used to more clearly illustrate the technical solutions of the present application, and therefore are only examples, and the protection scope of the present application is not limited thereby.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "including" and "having," and any variations thereof in the description and claims of this application and the description of the figures above, are intended to cover non-exclusive inclusions.
In the description of the embodiments of the present application, the technical terms "first", "second", and the like are used only for distinguishing different objects, and are not to be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary-secondary relationship of the technical features indicated. In the description of the embodiments of the present application, "a plurality" means two or more unless specifically defined otherwise.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.
In the description of the embodiments of the present application, the term "and/or" is only one kind of association relationship describing an associated object, and means that three relationships may exist, for example, a and/or B, and may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
In the description of the embodiments of the present application, the term "plurality" refers to two or more (including two), and similarly, "plural sets" refers to two or more (including two), and "plural pieces" refers to two or more (including two).
In the description of the embodiments of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate orientations or positional relationships that are based on the orientations or positional relationships shown in the drawings, and are used only for convenience in describing the embodiments of the present application and for simplicity in description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the embodiments of the present application.
In the description of the embodiments of the present application, unless otherwise explicitly specified or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrally formed; mechanical connection or electrical connection is also possible; they may be directly connected or indirectly connected through intervening media, or may be connected through the use of two elements or the interaction of two elements. The specific meanings of the above terms in the embodiments of the present application can be understood by those of ordinary skill in the art according to specific situations.
In this application, the battery cell may include a lithium ion secondary battery cell, a lithium ion primary battery cell, a lithium sulfur battery cell, a sodium ion battery cell, a magnesium ion battery cell, or the like, which is not limited in this application. The battery cell may be a cylinder, a flat body, a rectangular parallelepiped, or other shapes, which is not limited in the embodiments of the present application. The battery cells are generally divided into three types in an encapsulation manner: the cylindrical battery monomer, the square battery monomer and the soft package battery monomer are also not limited in the embodiment of the application.
Reference to a battery in embodiments of the present application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in the present application may include a battery module or a battery pack, etc. Batteries generally include a case for enclosing one or more battery cells. The box can avoid liquid or other foreign matters to influence the charge or discharge of battery cells.
The battery monomer comprises an electrode assembly and electrolyte, wherein the electrode assembly comprises a positive pole piece, a negative pole piece and an isolating membrane. The battery cell mainly depends on metal ions to move between the positive pole piece and the negative pole piece to work. The positive pole piece comprises a positive pole current collector and a positive pole active material layer, wherein the positive pole active material layer is coated on the surface of the positive pole current collector, the positive pole current collector which is not coated with the positive pole active material layer protrudes out of the positive pole current collector which is coated with the positive pole active material layer, and the positive pole current collector which is not coated with the positive pole active material layer is used as a positive pole lug.
The battery has the advantages of high energy density, good cycle performance, repeated charge and discharge, high safety performance and the like, so that the battery is widely applied to various fields of electronic equipment, power equipment and the like. Among them, the cycle performance of the battery has been one of the major points of research in the industry.
In the related art, as the number of cycles of the battery increases, the inside of the battery expands, which compresses the storage space of the electrolyte, so that the electrolyte cannot completely infiltrate into the inside of the battery, and even a phenomenon of lithium deposition occurs, which causes uneven distribution of stress generated inside the battery, and thus the expansion inside the battery may cause a decrease in the cycle performance thereof. As the requirements of each field for the cycle performance of the battery become higher, it is urgently needed to improve the cycle performance of the battery to meet the requirements of each field.
In view of this, the embodiment of the present application provides an electrode plate, a battery cell, a battery and an electric device, which can improve the cycle performance of the battery.
In this application, the powered device may be, but is not limited to, a cell phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, and the like. The electric toy may include a stationary or mobile electric toy, such as a game machine, an electric car toy, an electric ship toy, an electric airplane toy, and the like, and the spacecraft may include an airplane, a rocket, a space shuttle, a spacecraft, and the like.
For convenience of description, the following embodiments are described by taking an electric device as an example of a vehicle according to an embodiment of the present application.
FIG. 1 illustrates a schematic structural diagram of a vehicle provided by some embodiments of the present application.
Referring to fig. 1, a battery 100 is disposed inside a vehicle 1000, and the battery 100 may be disposed at the bottom or the head or the tail of the vehicle 1000. The battery 100 may be used for power supply of the vehicle 1000, for example, the battery 100 may serve as an operation power source of the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300, the controller 200 being configured to control the battery 100 to supply power to the motor 300, for example, for starting, navigation, and operational power requirements while the vehicle 1000 is traveling.
In some embodiments of the present application, the battery 100 may be used not only as an operating power source of the vehicle 1000, but also as a driving power source of the vehicle 1000, instead of or in part of fuel or natural gas, to provide driving power for the vehicle 1000.
Fig. 2 shows a schematic diagram of a battery provided in some embodiments of the present application.
Referring to fig. 2, the battery 100 includes a case 10 and a battery cell 20, and the case 10 is used for accommodating the battery cell 20.
The case 10 is a component for accommodating the battery cell 20, the case 10 provides an accommodating space for the battery cell 20, and the case 10 may have various structures. In some embodiments, the case 10 may include a first case 11 and a second case 12, and the first case 11 and the second case 12 cover each other to define a receiving space for receiving the battery cell 20. The first casing 11 and the second casing 12 may be in various shapes, for example, a rectangular parallelepiped, a cylinder, etc. The first casing 11 may have a hollow structure with one side open, the second casing 12 may have a hollow structure with one side open, and the casing 10 having the accommodating space is formed by closing the open side of the second casing 12 to the open side of the first casing 11. The first casing 11 may have a hollow structure with one side open, the second casing 12 may have a plate-like structure, and the second casing 12 may cover the open side of the first casing 11 to form the casing 10 having the accommodation space. The first casing 11 and the second casing 12 may be sealed by a sealing member, which may be a sealing ring, a sealant, or the like.
In the battery 100, one or more battery cells 20 may be provided. If there are a plurality of battery cells 20, the plurality of battery cells 20 may be connected in series, in parallel, or in series-parallel, where in series-parallel refers to that the plurality of battery cells 20 are connected in series or in parallel. A plurality of battery cells 20 may be connected in series, in parallel, or in series-parallel to form a battery module, and a plurality of battery modules may be connected in series, in parallel, or in series-parallel to form a whole, and may be accommodated in the box 10. Or all the battery cells 20 may be directly connected in series or in parallel or in series-parallel, and the whole of all the battery cells 20 is accommodated in the case 10.
Fig. 3 shows a schematic structural diagram of a battery cell provided in some embodiments of the present application.
Referring to fig. 3, the battery cell 20 is a minimum unit constituting the battery, and includes a case 21, an electrode assembly 22, an end cap 23, and other functional components.
The end cap 23 refers to a member that covers an opening of the case 21 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 23 may be adapted to the shape of the housing 21 to fit the housing 21. Alternatively, the end cap 23 may be made of a material (e.g., an aluminum alloy) having a certain hardness and strength, so that the end cap 23 is not easily deformed when being extruded and collided, and the battery cell 20 may have a higher structural strength and an improved safety performance. The end cap 23 may be provided with functional parts such as electrode terminals. The electrode terminals may be used to electrically connect with the electrode assembly 22 for outputting or inputting electric power of the battery cell 20.
The material of the end cap 23 may also be various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which is not limited in this embodiment.
In some embodiments of the present application, insulation may also be provided on the inside of the end cap 23, which may be used to isolate the electrical connection components within the housing 21 from the end cap 23 to reduce the risk of short circuits. Illustratively, the insulator may be plastic, rubber, or the like.
The case 21 is an assembly for mating with the end cap 23 to form an internal environment of the battery cell 20, wherein the formed internal environment may be used to house the electrode assembly 22, electrolyte, and other components. The housing 21 and the end cap 23 may be separate components, and an opening may be formed in the housing 21, and the opening may be covered by the end cap 23 to form the internal environment of the battery cell 20. Without limitation, the end cap 23 and the housing 21 may be integrated, and specifically, the end cap 23 and the housing 21 may form a common connecting surface before other components are inserted into the housing, and when it is necessary to enclose the inside of the housing 21, the end cap 23 covers the housing 21. The housing 21 may be of various shapes and various sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism shape, and the like. Specifically, the shape of the case 21 may be determined according to the specific shape and size of the electrode assembly 22. The material of the housing 21 may be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present invention is not limited thereto.
The electrode assembly 22 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 22 may be contained within the case 21. Electrode assembly 22 is formed primarily by winding or stacking two oppositely polarized pole pieces, and typically a separator is disposed between the two pole pieces. The portions of the pole pieces having active material form the main body portion of the electrode assembly 22, and the portions of the pole pieces not having active material form tabs, which may be located at one end of the main body portion together or at both ends of the main body portion, respectively. During the charging and discharging process of the battery, the active substance reacts with the electrolyte, and the tabs are connected with the electrode terminals to form a current loop.
Fig. 5 illustrates a schematic top view structure diagram of a pole piece provided in some embodiments of the present application.
Referring to fig. 5, the present embodiment provides a pole piece 221, where the pole piece 221 includes a current collector 2211 and an active material layer 2212. The active material layer 2212 includes a first portion 2212a and a second portion 2212b coated on the surface of the current collector 2211, and the first portion 2212a has a compacted density that is less than the compacted density of the second portion 2212 b.
In the embodiment of the present application, the pole piece 221 may be any one of a positive pole piece and a negative pole piece, and the embodiment of the present application is not particularly limited herein.
In some examples, the pole piece 221 is a positive pole piece comprising a positive current collector and a positive active material layer comprising a first portion 2212a and a second portion 2212b coated on the surface of the positive current collector, and the compacted density of the first portion 2212a is less than the compacted density of the second portion 2212 b.
In these examples, the positive electrode collector may be made of a metal foil, a porous metal plate, or the like. For example, the material of the positive electrode current collector may be, but is not limited to, a foil or a porous plate of a metal such as copper, nickel, titanium, or silver, or an alloy thereof. Further, in some embodiments of the present application, the positive electrode current collector employs aluminum foil.
The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may be any one selected from lithium iron phosphate, a ternary positive electrode material, and a lithium-rich positive electrode active material. In addition, the positive electrode active material layer may further include a conductive agent and a binder. The embodiment of the application does not specifically limit the types of the conductive agent and the binder in the positive electrode active material layer, and can be selected according to actual requirements.
By way of example, the conductive agent may be, but is not limited to, one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder may be, but is not limited to, one or more of styrene-butadiene rubber (SBR), aqueous acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylic resin, and polyvinyl alcohol (PVA).
The positive pole piece of the embodiment of the application can be prepared by adopting a conventional method in the field, for example, a positive active material, a conductive agent and a binder are fully stirred and mixed in a proper amount of NMP according to a certain mass ratio to form uniform positive pole slurry; and coating the positive electrode slurry on the surface of the positive electrode current collector aluminum foil, and drying and cold pressing to obtain the positive electrode piece.
In other examples, the pole piece 221 may also be a negative pole piece including a negative current collector and a negative active material layer including a first portion 2212a and a second portion 2212b coated on the surface of the negative current collector, and the compacted density of the first portion 2212a is less than that of the second portion 2212 b.
In these examples, the negative electrode current collector may be made of a metal foil, a porous metal plate, or the like. For example, the material of the negative electrode current collector may be, but is not limited to, a foil or a porous plate of a metal such as copper, nickel, titanium, or iron, or an alloy thereof. Further, in some embodiments of the present disclosure, the negative current collector is a copper foil.
The negative electrode active material layer includes a negative electrode active material, which may include natural graphite, artificial graphite, mesophase micro carbon spheres (abbreviated as MCMB), hard carbon, soft carbon, silicon-carbon composite, li-Sn alloy, li-Sn-O alloy, sn, snO 2 Spinel-structured lithiated TiO 2 -Li 4 Ti 5 O 12 And Li-Al alloy. In addition, the anode active material layer may further include a conductive agent and a binder. The embodiment of the present application does not specifically limit the types of the conductive agent and the binder in the negative electrode active material layer, and may be selected according to actual needs.
By way of example, the conductive agent may be, but is not limited to, one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the binder may be, but is not limited to, one or more of Styrene Butadiene Rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), aqueous acrylic, and carboxymethyl cellulose (CMC).
The negative pole piece of the embodiment of the application can be prepared by adopting a conventional method in the field, for example, a negative active material, a conductive agent and a binder are mixed according to a certain mass ratio and are fully stirred in a proper amount of deionized water to form uniform negative pole slurry; and coating the negative electrode slurry on the surface of the copper foil of the negative current collector, and drying and cold-pressing to obtain the negative electrode piece.
In the embodiments of the present application, the compaction density of the active material layer 2212 refers to the ratio between the weight of the active material layer 2212 and the volume of the active material layer 2212.
In the electrode sheet provided in the embodiment of the present application, the active material layer 2212 includes a first portion 2212a and a second portion applied to the surface of the current collector 2211, and the compaction density of the first portion 2212a is less than that of the second portion 2212 b. When the pole piece 221 is applied to a battery, as the cycle number of the battery increases, the compaction density of the first portion 2212a is smaller than that of the second portion 2212b, so that the expansion of the pole piece can be effectively relieved, the extrusion between the pole pieces in the battery is reduced, the pole piece is favorably soaked by electrolyte, and the cycle performance of the battery is improved.
In some embodiments of the present application, the first portion 2212a has a compacted density of 1.35g/cm 3 -2.10g/cm 3 Within the range. And/or, the second portion 2212b has a compacted density of 2.25g/cm 3 -2.60g/cm 3 Within the range.
In the above embodiments, the compaction density of the first portion 2212a is set within the above suitable range, which can further alleviate the expansion of the electrode sheet, and is helpful for the electrolyte to better infiltrate into the interior of the battery, so as to reduce the phenomenon of lithium precipitation, and the reduction of the phenomenon of lithium precipitation can make the stress generated in the interior of the battery be distributed uniformly, so as to further improve the cycle performance of the battery. Also, the packing density of the second portion 2212b is set within the above-mentioned appropriate range, which can contribute to an increase in the energy density of the battery while improving the cycle performance of the battery.
Illustratively, the compacted density of the first portion 2212a may be, but is not limited to, 1.35g/cm 3 、1.36g/cm 3 、1.37g/cm 3 、1.38g/cm 3 、1.39g/cm 3 、1.40g/cm 3 、1.41g/cm 3 、1.42g/cm 3 、1.43g/cm 3 、1.44g/cm 3 、1.45g/cm 3 、1.46g/cm 3 、1.47g/cm 3 、1.48g/cm 3 、1.49g/cm 3 、1.5g/cm 3 、1.51g/cm 3 、1.52g/cm 3 、1.53g/cm 3 、1.54g/cm 3 、1.55g/cm 3 、1.56g/cm 3 、1.57g/cm 3 、1.58g/cm 3 、1.59g/cm 3 、1.60g/cm 3 、1.61g/cm 3 、1.62g/cm 3 、1.63g/cm 3 、1.64g/cm 3 、1.65g/cm 3 、1.66g/cm 3 、1.67g/cm 3 、1.68g/cm 3 、1.69g/cm 3 、1.70g/cm 3 、1.71g/cm 3 、1.72g/cm 3 、1.73g/cm 3 、1.74g/cm 3 、1.75g/cm 3 、1.76g/cm 3 、1.77g/cm 3 、1.78g/cm 3 、1.79g/cm 3 、1.80g/cm 3 、1.81g/cm 3 、1.82g/cm 3 、1.83g/cm 3 、1.84g/cm 3 、1.85g/cm 3 、1.86g/cm 3 、1.87g/cm 3 、1.88g/cm 3 、1.89g/cm 3 、1.90g/cm 3 、1.91g/cm 3 、1.92g/cm 3 、1.93g/cm 3 、1.94g/cm 3 、1.95g/cm 3 、1.96g/cm 3 、1.97g/cm 3 、1.98 g/cm 3 、1.99g/cm 3 、2.0g/cm 3 、2.01g/cm 3 、2.02g/cm 3 、2.03g/cm 3 、2.04g/cm 3 、2.05g/cm 3 、2.06g/cm 3 、2.07g/cm 3 、2.08g/cm 3 、2.09g/cm 3 、2.10g/cm 3 。
The compacted density of the second portion 2212b may be, but is not limited to, 2.25g/cm 3 、2.26g/cm 3 、2.27g/cm 3 、2.28g/cm 3 、2.29g/cm 3 、2.3g/cm 3 、2.31g/cm 3 、2.32g/cm 3 、2.33g/cm 3 、2.34g/cm 3 、2.35g/cm 3 、2.36g/cm 3 、2.37g/cm 3 、2.38g/cm 3 、2.39g/cm 3 、2.40g/cm 3 、2.41g/cm 3 、2.42g/cm 3 、2.43g/cm 3 、2.44g/cm 3 、2.45g/cm 3 、2.46g/cm 3 、2.47g/cm 3 、2.48g/cm 3 、2.49g/cm 3 、2.50g/cm 3 、2.51g/cm 3 、2.52g/cm 3 、2.53g/cm 3 、2.54g/cm 3 、2.55g/cm 3 、2.56g/cm 3 、2.57g/cm 3 、2.58g/cm 3 、2.59g/cm 3 、2.60g/cm 3 。
In some embodiments of the present application, the active material capacity per unit area of the first portion 2212a is less than the active material capacity per unit area of the second portion 2212 b.
In the above embodiments, when the electrode sheet 221 is a positive electrode sheet, the material capacity per unit area of the first portion 2212a is smaller than the active material capacity per unit area of the second portion 2212b, which is equivalent to increasing the CB value of the first portion 2212a, so as to help reduce the occurrence of the lithium deposition phenomenon of the electrode sheet, and thus, the stress distribution generated inside the battery can be more uniform, thereby further improving the cycle performance of the battery.
Wherein the CB (Cell Balance) value is a ratio of the negative electrode active material capacity per unit area to the positive electrode active material capacity per unit area. For example, the CB (Cell Balance) value = Q of the active material of the first portion 2212a in the pole piece 221 1 /Q 2 Wherein, Q 1 Expressed as the active material capacity per unit area, Q, of the active material in the region of the negative electrode sheet corresponding to the first portion 2212a 2 Expressed as the positive electrode active material capacity per unit area of the first portion 2212a in the positive electrode sheet. The procedure for testing the active material capacity per unit area and the CB value is as follows:
s10: the average discharge capacity of the single-sided active material layer of the positive electrode is tested and specifically as follows:
s11: taking the positive pole piece of each embodiment, and obtaining a small sheet containing a positive single-sided active material layer by using a punching die;
s12: using a metal lithium sheet as a counter electrode and a Celgard membrane as a separation membrane, and dissolving LiPF 6 A (1 mol/L) solution of EC + DMC + DEC (ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) in a volume ratio of 1;
s13: standing for 12h after the battery is assembled, and carrying out constant current charging at the charging current of 0.1C until the voltage reaches the upper limit cut-off voltage x 1 V, then the voltage x is maintained 1 V, performing constant-voltage charging until the current is 50uA;
s14: standing for 5min, and performing constant current discharge at 0.1C until the voltage reaches lower limit cut-off voltage y 1 V；
S15: standing for 5min, repeating the above steps S11-S14, recording the discharge capacity of the 2 nd cycle, wherein the average value of the discharge capacities of 6 button cells is the average discharge capacity of the single-sided active material layer of the positive electrode, for example, when the active material of the positive electrode is lithium iron phosphate (LFP), the upper limit cut-off voltage x 1 V =3.75V, lower cut-off voltage y 1 V =2V; when the positive electrode active material is lithium nickel cobalt manganese oxide (NCM), the upper cut-off voltage x 1 V =4.25V, lower cut-off voltage y 1 V=2.8V。
S20: the average charge capacity of the single-sided active material layer of the negative electrode is tested, and the average charge capacity is specifically as follows:
s21: taking the negative electrode piece of each embodiment, and obtaining a small piece which has the same area as the positive electrode small piece in the step S10 and contains a negative electrode single-sided film layer by using a punching die;
s22: using a metal lithium sheet as a counter electrode and a Celgard membrane as a separation membrane, and dissolving LiPF 6 A (1 mol/L) solution of EC + DMC + DEC (ethylene carbonate, dimethyl carbonate, diethyl carbonate in a volume ratio of 1;
s23: standing for 12h after the battery is assembled, and performing constant current discharge at a discharge current of 0.05C until the voltage reaches a lower limit cut-off voltage y 2 mV, then discharged with a constant current of 50uA until the voltage reaches the lower cut-off voltage y 2 mV；
S24: standing for 5min, and performing constant current discharge with 10uA discharge current until reaching lower limit cut-off voltage y 2 mV；
S25: standing for 5min, and performing constant current charging at 0.1C until the final voltage reaches the upper limit and is cut off to voltage x 2 V；
S26: standing for 5min, repeating the steps S21-S25, and recording the charging capacity of the 2 nd cycle. The average value of the charge capacity of 6 button cells is the average charge capacity of the negative electrode single-sided film layer, for example, when the negative electrode active material is graphite, the upper limit cut-off voltage x 2 V =2V, lower cut-off voltage y 2 V =5mV. When the negative electrode active material is silicon, the upper cut-off voltage x 2 V =2V, lower cut-off voltage y 2 V=5mV。
S30: the CB value is calculated by dividing the average charge capacity (mAh) of the negative electrode single-side active material layer by the average discharge capacity (mAh) of the positive electrode single-side active material layer.
In some embodiments of the present application, the first portion 2212a includes a first active substance and the second portion 2212b includes a second active substance. The weight ratio W1 of the first active material to the first portion 2212a to the weight ratio W2 of the second active material to the second portion 2212b satisfies the following relationship: 0.6W2 is not less than W1 and not more than 0.8W2. The weight ratio W1 of the first active material to the first portion 2212a and the weight ratio W2 of the second active material to the second portion 2212b satisfy the above-described relationship, which can contribute to an increase in the CB value of the first portion 2212 a.
In some embodiments of the present application, the weight ratio W1 of the first active material to the first portion 2212a is 0.15g/1540.25mm 2 -0.28g/1540.25mm 2 Within the range. The weight ratio W2 of the second active material to the second portion 2212b is 0.25g/1540.25mm 2 -0.40g/1540.25mm 2 Within the range. W1 and W2 are set atWithin the above suitable range, the first portion 2212a has a suitable CB value to further contribute to the reduction of the occurrence of the lithium-deposition phenomenon on the electrode.
In the above embodiments, the first active material may be the same as or different from the second active material, as long as the weight ratio of the first active material to the first portion 2212a is smaller than that of the second active material to the second portion 2212b, which may contribute to increase the CB value of the first portion 2212a, thereby further improving the cycle performance of the battery.
In some embodiments of the present application, the porosity of the first portion 2212a is greater than the porosity of the second portion 2212 b.
The porosity is a ratio of a pore area per unit area of the active material layer, and the number of pores is set to be large, or the area of a single pore is set to be large, which contributes to improvement of the porosity. Thus, more apertures may be provided in the first portion 2212a than in the second portion 2212b, or the size of a single aperture in the first portion 2212a may be set larger than the size of a single aperture in the second portion 2212b, such that the porosity of the first portion 2212a is greater than the porosity of the second portion 2212 b. Through the arrangement, the capacity of the first part 2212a for storing the electrolyte is higher than that of the second part 2212b for storing the electrolyte, so that the infiltration of the electrolyte on the pole piece can be enhanced, and the cycle performance of the battery is improved.
In some embodiments of the present application, the porosity of the first portion 2212a can be set in the range of 25% -40%, and the porosity of the second portion 2212b can be set in the range of 20% -30%.
In these embodiments, the porosity of the first portion 2212a and the porosity of the second portion 2212b are set in the above suitable ranges, so that the first portion 2212a can store electrolyte more strongly than the second portion 2212b, which further helps to enhance the electrolyte infiltration into the pole piece, thereby improving the cycle performance of the battery.
In some embodiments of the present application, the first portion 2212a is bar-shaped, and the width of the first portion 2212a is in the range of 2mm-10 mm.
In the above embodiments, the width of the first portion 2212a is set within the above suitable range, which can help store a proper amount of electrolyte to reduce the phenomenon of lithium deposition, thereby being beneficial to relieve the swelling of the electrode sheet. In addition, setting the width of the first portion 2212a within the above-described appropriate range may also help the battery to maintain a high energy density.
Illustratively, the width of the first portion 2212a may be, but is not limited to, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm.
In some embodiments of the present application, the pole piece includes a plurality of first portions 2212a arranged at intervals, and the second portion 2212b is connected between two adjacent first portions 2212 a.
In the embodiments, the first portions 2212a arranged at intervals can further alleviate the expansion of the pole piece, and can also help to promote the electrolyte to infiltrate the pole piece.
Fig. 6 illustrates a schematic top view structure diagram of a pole piece according to some embodiments of the present disclosure. Fig. 7 illustrates a schematic top view structure diagram of a pole piece according to some embodiments of the present disclosure. Fig. 8 is a schematic diagram illustrating a top view structure of a pole piece according to still other embodiments of the present application.
In some embodiments of the present application, a distance between two adjacent first portions 2212a in an arrangement direction of the plurality of first portions 2212a is in a range of 40mm to 100 mm.
It is understood that the arrangement direction of the plurality of first portions 2212a may be arranged along the width direction of the pole piece, as shown in fig. 6; or arranged along the length direction of the pole piece, as shown in fig. 7; the arrangement can also be irregular as long as the distance between two adjacent first portions 2212a is in the range of 40mm-100mm, as shown in fig. 8. The embodiments of the present application are not particularly limited herein.
In the embodiments, the distance between two adjacent first portions 2212a is set within the above suitable range, which can help promote the electrolyte to infiltrate into the pole piece, and can further help the battery to maintain a high energy density.
For example, the spacing between two adjacent first portions 2212a may be, but is not limited to, 40mm, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100.
Fig. 4 is a schematic cross-sectional view illustrating an electrode assembly in a battery cell according to some embodiments of the present disclosure. Fig. 5 is a schematic cross-sectional view illustrating an electrode assembly in a battery cell according to further embodiments of the present disclosure.
Referring to fig. 4 and 5, an electrode assembly 22 according to an embodiment of the present disclosure includes a first pole piece 222 and a second pole piece 223 with opposite polarities, where the first pole piece 222 is the pole piece 221 of any one of the embodiments described above. Since the electrode assembly includes the pole piece 221 in any of the embodiments, the electrode assembly 22 has the technical effects of the pole piece 221, which are not described herein again.
Referring to fig. 5, in some embodiments of the present application, the first pole piece 222 and the second pole piece 223 are wound along the winding direction a, and at least a portion of the first portion 2212a is disposed at an inner end of the current collector along the winding direction a. In the above embodiments, at least part of the first portion 2212a is disposed at the inner end of the current collector in the winding direction a, so that the stress generated inside the electrode assembly 22 is released to the through hole 225, and the damage to the external parts due to the outward diffusion of the stress is reduced. And the arrangement of at least part of the first portion 2212a can help to reduce the stress on the hole wall of the through hole 225, thereby effectively relieving the expansion of the pole piece.
In some embodiments of the present application, electrode assembly 22 is cylindrical.
The cylindrical electrode assembly 22 is wound in the winding direction a by the first and second pole pieces 222 and 223 such that the electrode assembly 22 has a through-hole 225 at the center thereof.
Referring to fig. 10, in the related art, as the number of cycles of the cylindrical electrode assembly increases, stress generated in the cylindrical electrode assembly is released toward the center hole, causing the center hole to collapse, thereby allowing the cycle performance of the battery to jump.
Referring to fig. 11, since the compaction density of the first portion of the first electrode sheet is less than that of the second portion, the occurrence of the collapse of the through hole in the center of the electrode assembly can be reduced, thereby improving the cycle performance of the battery.
In some embodiments of the present application, the first pole piece 222 is a positive pole piece. This can help reduce swelling of the second pole piece 222 and promote wetting of the first and second pole pieces 222, 223 by the electrolyte.
In some embodiments of the present application, the electrode assembly may further include a separation film 224, and the separation film 224 serves to separate the first pole piece 222 and the second pole piece 223 to reduce the risk of a short circuit between the first pole piece 222 and the second pole piece 223. The separation film 224 has a large number of micropores penetrating therethrough, and can ensure free passage of electrolyte ions and good permeability to lithium ions, so that the separation film 224 cannot substantially block passage of lithium ions.
The material of the isolation film 224 may be polypropylene (PP), polyethylene (PE), or the like.
The embodiment of the application provides a battery cell, which comprises a shell, an electrode assembly and electrolyte. The housing has a receiving cavity. The electrode assembly is arranged in the accommodating cavity, and the electrode assembly is the electrode assembly in any one of the embodiments. The electrolyte is contained in the containing cavity and infiltrates the electrode assembly. Since the battery cell includes the electrode assembly in any one of the embodiments described above, the battery cell has good cycle performance.
An embodiment of the present application provides a battery, including the battery cell in any one of the above embodiments. Since the battery includes the battery cell in any of the above embodiments, the battery has the technical effects of the battery cell, which are not described herein again.
The embodiment of the application provides an electric device which comprises the battery in the embodiment.
Example 1
Preparation of positive pole piece
Lithium iron phosphate (LiFePO) as positive electrode active material 4 ) The conductive agent Super P and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in N-methyl pyrrolidone (NMP) according to the mass ratio of 95; coating positive electrode slurry on the surface of a current collector aluminum foil, drying at 85 ℃, then carrying out cold pressing, trimming, cutting and slitting, and drying for 4h at 85 ℃ under a vacuum condition to obtain a positive electrode plate, wherein the surface of a current collector in the positive electrode plate is coated with a first part and a second part 2212b positive electrode active material layer, and the compaction density rho of the first part 1 Second part compacted density p 2 。
Preparation of negative pole piece
Mixing graphite serving as a negative active material, a conductive agent Super P, a thickening agent CMC and Styrene Butadiene Rubber (SBR) serving as a binder according to a ratio of 92:3:2.5:2.5, fully stirring in deionized water to form uniform cathode slurry; and coating the negative electrode slurry on the surface of the current collector copper foil, drying at 85 ℃, then carrying out cold pressing, trimming, cutting and slitting, and drying for 12h at 120 ℃ under a vacuum condition to obtain a negative electrode plate.
Isolation film
A polyethylene film (PE) having a thickness of 16 μm was used.
Preparation of the electrolyte
After Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) were mixed uniformly in a glove box filled with argon (water content < 10ppm, oxygen content < 1 ppm) according to 3:7 (W%/W%), 1mol of LiFP was slowly added to the above solution 6 Wait for LiFP 6 And after complete dissolution, obtaining the electrolyte.
Preparation of battery cell
Stacking and winding the positive pole piece, the isolating membrane and the negative pole piece in sequence to obtain an electrode assembly; and (3) putting the electrode assembly into a shell, adding the prepared electrolyte, and carrying out processes of packaging, standing, formation, aging and the like to obtain the battery monomer.
Examples 1 to 3 and comparative example 1
The preparation is analogous to example 1, except that: the compacted densities of the first and second portions of the positive electrode active material layer are detailed in table 1.
Test section
1) Test of compacted Density
Taking the completely discharged battery monomer, disassembling a negative electrode, cleaning, drying, weighing a positive electrode (the positive active material layer is coated on the two sides of a positive current collector) with a certain area S by using an electronic balance, recording the weight as W1, and measuring the thickness T1 of the positive electrode by using a ten-thousandth ruler. And (3) washing away the positive active material layer by using a solvent, drying, measuring the weight of the positive current collector, recording as W2, and measuring the thickness T2 of the positive current collector by using a ten-thousandth ruler. The weight W0 and thickness T0 of the positive electrode active material layer provided on the positive electrode current collector side and the compacted density of the positive electrode active material layer were calculated by the following formulas:
W0＝(W1-W2)/2
T0＝(T1-T2)/2
the compacted density ρ = W0/(T0 × S) of the positive electrode active material layer.
2) Testing of battery cell cycle performance
Charging the battery monomer to 3.65V at a constant current of 0.5C, then charging to 0.05C at a constant voltage of 3.65V, then discharging to 2.5V at a constant current of 1C under the environment of 25 ℃, and recording the discharge capacity as C 1 . The discharge capacity of the battery cell after 600 cycles is recorded as C 2 . The capacity retention ratio (%) of the battery cell after 600 cycles = C 2 /C 1 X 100%, the test results are shown in table 1.
TABLE 1
Figure 555386DEST_PATH_IMAGE001
As a result of comparing the test results of the examples and the comparative examples according to table 1 and fig. 9, in the examples of the present application, the first part having a lower compacted density than the second part can improve the cycle performance of the battery as the number of cycles of the battery increases.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present disclosure, and the present disclosure should be construed as being covered by the claims and the specification. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. The present application is not intended to be limited to the particular embodiments disclosed herein but is to cover all embodiments that may fall within the scope of the appended claims.

Claims (10)

1. An electrode assembly, comprising: the polarity of the first pole piece and the second pole piece is opposite, and the first pole piece and the second pole piece are wound along the winding direction;
the first pole piece comprises a current collector and an active substance layer, the active substance layer comprises a first part and a second part which are coated on the same surface of the current collector and located in different areas, the first part and the second part are arranged along the winding direction, at least part of the first part is arranged at the inner end of the current collector along the winding direction, and the compaction density of the first part is smaller than that of the second part;
the active material capacity per unit area of the first portion is less than the active material capacity per unit area of the second portion;
the first portion comprises a first active material and the second portion comprises a second active material;
wherein the first active substance and the weight of the first partThe amount ratio W1 and the weight ratio W2 of the second active material to the second part satisfy the following relationship: 0.6W2 ≤ W1 ≤ 0.8W2, and the weight ratio W1 of the first active substance and the first part is 0.15g/1540.25mm 2 -0.28g/1540.25mm 2 Within the range;
the weight ratio W2 of the second active substance to the second part is 0.25g/1540.25mm 2 -0.40g/1540.25mm 2 Within the range;
the first pole piece is a positive pole piece.
2. The electrode assembly of claim 1, wherein the first portion has a compacted density of 1.35g/cm 3 -2.10g/cm 3 Within the range; and/or the presence of a gas in the gas,
the second part has a compacted density of 2.25g/cm 3 -2.60g/cm 3 Within the range.
3. The electrode assembly of claim 1, wherein the porosity of the first portion is greater than the porosity of the second portion.
4. The electrode assembly of claim 1, wherein the first portion is bar-shaped and has a width in the range of 2mm-10 mm.
5. The electrode assembly of claim 1, wherein the first pole piece includes a plurality of spaced apart first portions, and the second portion is connected between two adjacent first portions.
6. The electrode assembly according to claim 5, wherein a pitch between adjacent two of the first portions in an arrangement direction of the plurality of the first portions is in a range of 40mm to 100 mm.
7. The electrode assembly of claim 1, wherein the electrode assembly is cylindrical.
8. A battery cell, comprising:
a housing having an accommodating chamber;
an electrode assembly disposed within the receiving cavity, the electrode assembly being as in any one of claims 1-7;
and the electrolyte is accommodated in the accommodating cavity and infiltrates the electrode assembly.
9. A battery comprising the cell of claim 8.
10. An electrical device comprising the battery of claim 9, wherein the battery is configured to provide electrical energy.
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CN216872018U (en) * 2021-10-15 2022-07-01 宁德时代新能源科技股份有限公司 Pole piece, electrode component, battery monomer, battery and power consumption device
CN114122315A (en) * 2021-11-22 2022-03-01 宁德新能源科技有限公司 Electrochemical device and electronic device
CN114628630A (en) * 2022-03-21 2022-06-14 宁德新能源科技有限公司 Electrochemical device and electronic device
CN114784230B (en) * 2022-03-29 2023-12-12 东莞锂威能源科技有限公司 Method for improving lithium precipitation of soft-package square battery
CN114613935A (en) * 2022-03-31 2022-06-10 珠海冠宇电池股份有限公司 Lithium ion battery

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