Electrode assembly, battery cell and battery

Abstract

The utility model relates to the electrode assembly, the battery monomer and the battery, and the electrode assembly comprises a plurality of layers of electrode units and a plurality of puncture-resistant layers. Each layer of electrode unit comprises a positive plate, a diaphragm and a negative plate which are stacked along the stacking direction, and the diaphragm is arranged between the adjacent positive plate and negative plate. The puncture-resistant layers and the electrode units are alternately arranged in the stacking direction, and the puncture-resistant layers are arranged on the outer sides of the multiple layers of electrode units. Wherein each puncture-resistant layer is configured to be stretched along with puncture of a test probe when the puncture-resistant layer is punctured by the test probe, and is insulated and isolated between the test probe and the electrode unit. In every two adjacent puncture-resistant layers, the puncture-resistant layer on the outer layer can be stretched to the puncture-resistant layer on the inner layer along with puncture of the test probe. According to the technical scheme, the risk of thermal runaway caused by internal short circuit of the electrode assembly due to foreign matter puncture can be reduced, and the safety of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to an electrode assembly, a battery cell, and a battery. Background Art

[0002] During the use of a lithium-ion battery, a short circuit may occur in case of an accident, which may further cause thermal runaway. In battery tests, a nail penetration test is generally used to simulate such a failure situation. The nail penetration test refers to the situation where a test probe penetrates into a battery cell to simulate the internal short circuit or thermal runaway of the battery cell induced by a foreign object piercing the battery cell.

[0003] In the related art, a protective film is usually wrapped around the entire outer side of the electrode assembly. During the nail penetration test, the test probe easily pierces through the protective film and contacts the positive electrode plate and the negative electrode plate, triggering a short circuit or thermal runaway of the battery cell, resulting in the failure of the nail penetration test of the battery cell, and the safety of the battery cell needs to be improved. Summary of the Utility Model

[0004] Based on this, the present application provides an electrode assembly, a battery cell, and a battery, aiming to reduce the problem that short circuit or thermal runaway easily occurs when the battery cell is punctured, and improve the safety of the battery.

[0005] In a first aspect, the present application provides an electrode assembly, which includes:

[0006] Multiple layers of electrode units, each layer of electrode unit including a positive electrode plate, a separator, and a negative electrode plate stacked in a stacking direction, and the separator is disposed between the adjacent positive electrode plate and the negative electrode plate; and

[0007] Multiple layers of puncture-resistant layers, the puncture-resistant layers and the electrode units are alternately arranged in the stacking direction, and the puncture-resistant layers are disposed outside the multiple layers of electrode units;

[0008] Wherein, each layer of the puncture-resistant layer is configured such that when being punctured by a test probe, it can be stretched following the puncture of the test probe and insulate and isolate between the test probe and the electrode unit; among every two adjacent layers of the puncture-resistant layers, the outer puncture-resistant layer can be stretched to the inner puncture-resistant layer following the puncture of the test probe.

[0009] In some embodiments, the elongation at break of each layer of the puncture-resistant layer is β, the stacking thickness of each layer of the electrode unit is H, and the diameter of the test probe is A, satisfying: β * A ≥ H.

[0010] In some embodiments, it satisfies: 5 mm ≤ A ≤ 8 mm.

[0011] In some embodiments, the puncture resistance of the puncture-resistant layer is α, and the tensile strength is θ, satisfying: β≥ 200%, α ≥ 0.125 N / μm, θ ≥ 50 MPa.

[0012] In some embodiments, the thickness of each puncture-resistant layer is 3 μm to 100 μm.

[0013] In some embodiments, the puncture-resistant layer includes at least one of unmodified or modified PTFE, ETFE, FEP, PFA, PCTFF, ECTFE, PE, and PA.

[0014] In some embodiments, the electrode unit has a fixed surface in the stacking direction; the puncture-resistant layer is fixedly connected to the fixed surface of the electrode unit;

[0015] Wherein, each fixed surface is formed by one of the positive electrode sheet, the separator, and the negative electrode sheet; the electrode sheet forming the fixed surface is a double-sided active layer structure or a single-sided active layer structure, and the surface of the electrode sheet with the single-sided active layer structure where the active layer is not provided forms the fixed surface;

[0016] In some embodiments, the puncture-resistant layer is thermocompression-bonded to the fixed surface of the electrode unit.

[0017] In some embodiments, the puncture-resistant layer is coated on the fixed surface of the electrode unit.

[0018] In some embodiments, along the stacking direction, the projection of the electrode unit falls within the projection range of the puncture-resistant layer.

[0019] In some embodiments, the edge of the puncture-resistant layer forms a hem that is bent along the stacking direction, and the hem is fixedly connected to the separator in the electrode unit;

[0020] In some embodiments, the puncture-resistant layer is configured not to allow ions to penetrate.

[0021] In a second aspect, the present application provides a battery cell, including:

[0022] A package; and

[0023] The electrode assembly described in the above embodiments, and the electrode assembly is accommodated in the package.

[0024] In a third aspect, the present application provides a battery, including the battery cell described in the above embodiments.

[0025] In the above-mentioned electrode assembly, battery cell and battery, during the needle penetration test of the electrode assembly, the puncture-resistant layer can well wrap the test probe part located in the electrode unit, so that the test probe is insulated from the electrode assembly. Moreover, when the test probe pierces the electrode unit, the outer puncture-resistant layer can stretch along with the test probe to the inner puncture-resistant layer, so that the adjacent inner and outer puncture-resistant layers can continuously wrap around the test probe, significantly reducing the probability of direct contact between the test probe and the electrode unit, greatly reducing the risk of thermal runaway caused by short circuit inside the electrode assembly when a foreign object pierces the electrode assembly, and helping to improve the safety of the electrode. Description of the Drawings

[0026] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0027] Figure 1 It is a schematic structural diagram of an electrode assembly for some embodiments.

[0028] Figure 2 is Figure 1 a schematic diagram of the needle penetration test for the shown electrode assembly.

[0029] Figure 3 It is a schematic structural diagram of an electrode assembly for some other embodiments.

[0030] Figure 4 It is a schematic structural diagram of an electrode assembly for some other embodiments.

[0031] Figure 5 It is a schematic structural diagram of an electrode assembly for some other embodiments.

[0032] Figure 6 It is a schematic structural diagram of an electrode assembly for some other embodiments.

[0033] The reference numerals in the specific embodiments are as follows:

[0034] 100, electrode assembly; X, lamination direction; 10, electrode unit; 11, positive electrode sheet; 12, separator; 13, negative electrode sheet; 20, puncture-resistant layer; 20a, hem; 200, test probe. Specific Embodiments

[0035] To make the above objects, features, and advantages of the present application more apparent and understandable, the following provides a detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings. Many specific details are set forth in the following description to facilitate a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0036] In the description of the present application, it should be understood that if present, the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0037] In addition, if present, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0038] In the present application, unless otherwise clearly specified and limited, if present, the terms "install", "connect", "join", "fix", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0039] In this application, if it appears, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0040] It should be noted that if it appears, when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only implementation.

[0041] In view of the problem that when the battery is punctured by foreign objects, it is easy to cause internal short circuit or thermal runaway, reducing the safety of the battery, the embodiments of the present application propose an electrode assembly, a battery cell and a battery.

[0042] The battery cell involved in the embodiments of the present application includes a package and the electrode assembly mentioned in the embodiments of the present application, and the electrode assembly is accommodated in the package. The package can be a rigid outer shell, a soft aluminum-plastic film, etc., which plays a role in protecting the internal electrode assembly. Usually, multiple electrode assemblies are encapsulated in the package. Usually, a liquid injection port for injecting electrolyte and a terminal for electrically connecting to each electrode assembly are provided on the package. Specifically, the package can be a square shell structure, a cylindrical shell structure, etc.

[0043] The battery involved in the embodiments of the present application can be a battery module or a battery pack. In addition to the battery cell, in some embodiments, the battery further includes a box body, and the battery cell is accommodated in the box body. Usually, multiple battery cells are arranged in the box body, and the battery cells are connected in series or in parallel with each other. In addition, a thermal management system, a battery management system, etc. can also be configured in the battery.

[0044] The electrode assembly in the embodiments of the present application will be introduced in detail below.

[0045] Refer to Figure 1, the electrode assembly 100 provided by the embodiment of the present application includes multiple layers of electrode units 10 and multiple layers of puncture-resistant layers 20. Each layer of electrode unit 10 includes a positive electrode sheet 11, a separator 12, and a negative electrode sheet 13 stacked along the stacking direction X. The separator 12 is disposed between adjacent positive electrode sheets 11 and negative electrode sheets 13. The puncture-resistant layer 20 is alternately disposed with the electrode unit 10 in the stacking direction X, and the puncture-resistant layer 20 is disposed outside the multiple layers of electrode units 10. Wherein, each layer of puncture-resistant layer 20 is configured to be stretched following the puncture of the test probe 200 when being punctured by the test probe 200, and insulate and isolate between the test probe 200 and the electrode unit 10. In each adjacent two layers of puncture-resistant layers 20, the outer puncture-resistant layer 20 can be stretched to the inner puncture-resistant layer 20 following the puncture of the test probe 200.

[0046] The positive electrode sheet 11 is composed of a positive electrode current collector and a positive electrode active layer coated on the positive electrode current collector. The positive electrode current collector can be but is not limited to aluminum. The positive electrode active layer can be but is not limited to include lithium borate, lithium titanate, lithium manganate, lithium cobaltate, lithium nickelate, etc. The negative electrode sheet 13 is composed of a negative electrode current collector and a negative electrode active layer coated on the negative electrode current collector. The negative electrode current collector can be but is not limited to copper. The negative electrode active layer can be but is not limited to include artificial graphite, natural graphite, mesophase carbon microspheres, lithium titanate, silicon-based materials, tin-based materials, etc. The separator 12 has insulation properties, and the positive electrode sheet 11 and the negative electrode sheet 13 are insulated and isolated by the separator 12. The separator 12 can also allow ions to pass through. When the battery is charged and discharged, lithium ions can pass through the separator 12 and intercalate and deintercalate between the positive electrode sheet 11 and the negative electrode sheet 13. The separator 12 can be but is not limited to materials such as polyolefin, polypropylene, or polyethylene.

[0047] The electrode unit 10 is a structure formed by sequentially stacking the positive electrode sheet 11, the separator 12, and the negative electrode sheet 13 along the stacking direction X. The positive electrode sheet 11 and the negative electrode sheet 13 are insulated and separated by the separator 12. The outer layer of the electrode unit 10 can be the positive electrode sheet 11, or the negative electrode sheet 13, or the separator 12. In each layer of electrode unit 10, the numbers of the positive electrode sheet 11, the negative electrode sheet 13, and the separator 12 are all at least one, and the three can be stacked in a stacked type or a wound type. That is, the electrode assembly 100 in the embodiment of the present application can be a stacked structure or a wound structure. The stacking direction X is the stacking direction of the positive electrode sheet 11, the negative electrode sheet 13, and the separator 12, corresponding to the thickness direction of the separator 12.

[0048] The multi-layer puncture-resistant layer 20 and the multi-layer electrode unit 10 are alternately arranged in the above-mentioned stacking direction X in the order of the puncture-resistant layer 20 and the electrode unit 10. There is a puncture-resistant layer 20 between adjacent electrode units 10, and a puncture-resistant layer 20 is provided outside the outermost electrode unit 10. Generally but not limitedly, the thicknesses of the respective puncture-resistant layers 20 are equal. Generally but not limitedly, the arrangement manners of the positive electrode sheet 11, the negative electrode sheet 13, and the separator 12 in each electrode unit 10 are the same.

[0049] The puncture-resistant layer 20 has good insulation, and has a certain puncture resistance, tensile strength, and good elongation at break.

[0050] Refer to Figure 2 , during the needle puncture test, the test probe 200 punctures the electrode assembly 100, and the puncture-resistant layer 20 can block the test probe 200, and at the same time is stretched by the test probe 200 in the puncture process. The stretched puncture-resistant layer 20 wraps around the test probe 200 to insulate and isolate the test probe 200 from the positive electrode sheet 11 and the negative electrode sheet 13 in the electrode assembly 100.

[0051] When the test probe 200 penetrates the electrode unit 10 located between two adjacent puncture-resistant layers 20, the outer puncture-resistant layer 20 can be stretched by the test probe 200 to the inner puncture-resistant layer 20, so that the inner puncture-resistant layer 20 can well connect and wrap around the outside of the test probe 200 to prevent the test probe 200 from being exposed inside the electrode unit 10.

[0052] Among them, when the test probe 200 penetrates the electrode unit 10, the outer puncture-resistant layer 20 may or may not be punctured. The outer puncture-resistant layer 20 follows the test probe 200 and is stretched to the inner puncture-resistant layer 20, including that the projections of both the outer puncture-resistant layer 20 and the inner puncture-resistant layer 20 in the puncture direction of the test probe 200 are overlapped or connected. When the projections of the two overlap, the stretched end of the outer puncture-resistant layer 20 can follow the test probe 200 and extend into the interior of the inner puncture-resistant layer 20. When the projections of the two are connected, the stretched end of the outer puncture-resistant layer 20 is flush with the end face of the inner puncture-resistant layer 20.

[0053] Thus, during the needle puncture test of the above-mentioned electrode assembly 100, the puncture-resistant layer 20 can well wrap the part of the test probe 200 located in the electrode unit 10, isolating the test probe 200 from the electrode assembly 100 insulatively. Moreover, when the test probe 200 pierces the electrode unit 10, the outer puncture-resistant layer 20 can stretch along with the test probe 200 to the inner puncture-resistant layer 20, so that the adjacent inner and outer puncture-resistant layers 20 can continuously wrap around the test probe 200, significantly reducing the probability of direct contact between the test probe 200 and the electrode unit 10, and greatly reducing the risk of thermal runaway caused by short circuit inside the electrode assembly 100 when a foreign object pierces the electrode assembly 100, which helps to improve the safety of the electrode assembly 100.

[0054] It should be noted that the needle puncture test can be carried out according to test standards such as GB / T 31467.3-2015 and IEC62133-2:2017.

[0055] In some embodiments, combined with Figure 2 , the elongation at break of each layer of the puncture-resistant layer 20 is β, the stacked thickness of each layer of the electrode unit 10 is H, and the diameter of the test probe 200 is A, satisfying: β*A > H.

[0056] The elongation at break is one of the important indicators to measure the tensile strength of a material. It refers to the ratio of the elongation length of the material when stretched to break to the original length. The higher the elongation at break, the better the toughness and the stronger the tensile ability of the material. Regarding the specific measurement method of the elongation at break, relevant national standards can be referred to. Generally, the puncture-resistant layer 20 is made of plastic material, and the measurement of its elongation at break can be carried out according to the standard of GB / T1040.3-2006 "Testing of Plastics - Part 3: Test Conditions for Films and Sheets".

[0057] The stacked thickness H of the electrode unit 10 refers to the dimension of the electrode unit 10 in the stacking direction X, which can be specifically understood as the total thickness after the positive electrode sheet 11, the negative electrode sheet 13 and the separator 12 in the electrode unit 10 are stacked. During the needle puncture test, a circular test probe 200 is usually used.

[0058] In the embodiments of the present application, the elongation at break β of the puncture-resistant layer 20, the diameter A of the test probe 200, and the stacked thickness H of the electrode unit 10 satisfy: β*A ≥ > H. Among them, H and A have the same unit, and the unit is usually mm.

[0059] It has been experimentally proven that when the elongation at break β of the puncture-resistant layer, the diameter A of the test probe 200, and the stacked thickness H of the electrode unit 10 meet the above conditions, it can ensure that the puncture-resistant layer 20 of the outer layer can follow the test probe 200 and stretch to the puncture-resistant layer 20 of the inner layer, so that the adjacent inner and outer puncture-resistant layers 20 can continuously wrap around the test probe 200, ensuring that there is no contact between the test probe 200 and the electrode unit 10, and greatly reducing the risks of battery short circuit and thermal runaway caused by foreign object puncture.

[0060] Specifically in the embodiment, it satisfies: 5mm ≤ A ≤ 8mm. Generally, when the diameter of the test probe 200 is between 5mm and 8mm and the value of H does not exceed 5 * β, the electrode assembly 100 can meet the requirements of most needle puncture tests.

[0061] In some embodiments, the puncture resistance of the puncture-resistant layer 20 is α, and the tensile strength is θ, satisfying β ≥ 200%, α ≥ 0.125 N / μm, θ ≥ 50 MPa.

[0062] Specifically, the optional range of the elongation at break β includes β = 200% and β > 200%. At this time, the puncture-resistant layer 20 has good toughness and strong tensile ability, and can effectively follow the required length of the test probe 200. For example, the elongation at break β can be selected as 200%, 230%, 250%, 280%, 300%, etc. Specifically, the optional range of the puncture resistance α includes α = 0.125 N / μm and α > 0.125 N / μm. The optional range of the tensile strength θ includes θ = 50 MPa and θ > 50 MPa.

[0063] Among them, the tensile strength θ of the puncture-resistant layer 20 can be measured with reference to the test method shown in the standard of GB / T 1040.3 - 2006. The puncture resistance α can be measured with reference to the test method shown in the standard of GB / T 36363 - 2018.

[0064] It has been experimentally proven that when α, θ, and β meet the above conditions, the puncture-resistant layer 20 has a good tensile effect and can effectively wrap the test probe 200 during the puncture process of the test probe 200.

[0065] In some embodiments, the thickness of each puncture-resistant layer 20 is 3μm - 100μm.

[0066] Generally, the thicknesses of the puncture-resistant layers 20 of each layer are equal. The thickness of the puncture-resistant layer 20 refers to the dimension in the stacking direction X. Specifically, the thickness of the puncture-resistant layer 20 is selected from 3 μm, 5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, and values between any two adjacent selected values.

[0067] When the thickness of the puncture-resistant layer 20 is within the above range, the puncture-resistant layer 20 not only has a good tensile effect and is not easily broken, but also does not occupy too much volume space of the electrode assembly 100, which helps to improve the energy density of the electrode assembly 100.

[0068] In some embodiments, the puncture-resistant layer 20 includes at least one of unmodified or modified PTFE, ETFE, FEP, PFA, PCTFF, ECTFE, PE, and PA.

[0069] Among them, PTFE (polytetrafluoroethylene), ETFE (ethylene-tetra-fluoro-ethylene copolymer), PFA (Polyfluoroalkoxy copolymer), FEP (Fluorinated ethylene propylene copolymer), PCTFF (Polytrifluorochloroethylene), ECTFE (Ethylene-chlorotrifluoroethylene copolymer), PE (Polyethylene), PVC (Polyvinyl chloride), and PA (Polyamide) are all insulating materials with good puncture resistance, tensile strength, and high elongation at break. The puncture-resistant layer 20 can be a layer structure prepared by one or a mixture of the above various unmodified or modified materials. For example, the puncture-resistant layer 20 is formed by nylon (BOPA, a modified PA material). Another example is that the puncture-resistant layer 20 is formed by PFA. Another example is that the puncture-resistant layer 20 is formed by ETFE.

[0070] At this time, the puncture-resistant layer 20 not only has good insulation, but also has good puncture resistance, tensile strength, and extensibility, and can effectively wrap the test probe 200 in the puncture test.

[0071] In some embodiments, the electrode unit 10 has a fixed surface in the stacking direction X, and the puncture-resistant layer 20 is fixedly connected to the fixed surface of the electrode unit 10. Each fixed surface is formed by one of the positive electrode sheet 11, the separator 12, and the negative electrode sheet 13. The electrode sheet forming the fixed surface is of a double-sided active layer structure or a single-sided active layer structure, and the surface of the electrode sheet of the single-sided active layer structure without the active layer forms the fixed surface.

[0072] The electrode unit 10 is fixedly connected to the puncture-resistant layer 20 through its fixed surface, which can prevent the puncture-resistant layer 20 from sliding along the surface of the electrode unit 10, resulting in the exposure of the electrode sheet and the inability to obtain protection. The puncture-resistant layer 20 can be fixed on the fixed surface of the electrode unit 10 by means such as adhesion and hot pressing.

[0073] Each fixed surface can be formed by any one of the positive electrode sheet 11, the negative electrode sheet 13, and the separator 12, specifically depending on the arrangement of the positive electrode sheet 11, the separator 12, and the negative electrode sheet 13 in the electrode unit 10.

[0074] As Figure 1 shown, when the internal arrangement of the electrode unit 10 is: the separator 12, the positive electrode sheet 11, the separator 12, the negative electrode sheet 13, and the separator 12 are stacked in sequence, the fixed surface of the electrode unit 10 is formed by the separator 12.

[0075] As Figure 3 shown, when the internal arrangement of the electrode unit 10 is: the positive electrode sheet 11, the separator 12, and the negative electrode sheet 13 are stacked in sequence, one of the fixed surfaces of the electrode unit 10 is formed by the positive electrode sheet 11, and the other fixed surface is formed by the negative electrode sheet 13.

[0076] As Figure 4 shown, when the internal arrangement of the electrode unit 10 is: the negative electrode sheet 13, the separator 12, the positive electrode sheet 11, the separator 12, the negative electrode sheet 13, the separator 12, the positive electrode sheet 11, and the separator 12 are stacked in sequence, one of the fixed surfaces of the electrode unit 10 is formed by the negative electrode sheet 13, and the other fixed surface is formed by the separator 12.

[0077] As Figure 5 shown, when the internal arrangement of the electrode unit 10 is: the separator 12, the negative electrode sheet 13, the separator 12, the positive electrode sheet 11, the separator 12, the negative electrode sheet 13, the separator 12, and the positive electrode sheet 11 are stacked in sequence, one of the fixed surfaces of the electrode unit 10 is formed by the positive electrode sheet 11, and the other fixed surface is formed by the separator 12.

[0078] It should be noted that the electrode sheets (including the positive electrode sheet 11 and the negative electrode sheet 13) forming the fixed surface can be of a double-sided active layer structure or a single-sided active layer structure. An electrode sheet with a double-sided active layer structure means that active layers are provided on both sides of the electrode sheet in its thickness direction (corresponding to the above-mentioned stacking direction X). An electrode sheet with a single-sided active layer structure means that an active layer is provided only on one side of the electrode sheet in its thickness direction, and the other side is a smooth surface (the smooth surface refers to the surface without an active layer). At this time, the smooth surface of the electrode sheet with a single-unit active layer structure is used as the fixed surface.

[0079] Among them, the active layer of the positive electrode sheet 11 is formed by a positive electrode material, and the active layer of the negative electrode sheet 13 is formed by a negative electrode material. In the figure, the reference numeral 11a is used to represent the positive electrode sheet 11 with active layers provided on both sides, the reference numeral 11b is used to represent the positive electrode sheet 11 with an active layer provided on one side, the reference numeral 13a is used to represent the negative electrode sheet 13 with active layers provided on both sides, and the reference numeral 13b is used to represent the negative electrode sheet 13 with an active layer provided on one side.

[0080] That is to say, in the electrode unit 10 of the embodiment of the present application, the specific arrangement forms of the internal positive electrode sheet 11, the separator 12, and the negative electrode sheet 13 are diverse, and the electrode sheet forming the fixed surface can be of a double-sided active layer structure or a single-sided active layer structure. Of course, the electrode sheet (not forming the fixed surface) located in the middle of the electrode unit 10 is usually of a double-sided active layer structure.

[0081] By using an electrode sheet with an active layer provided on one side and fixedly connecting the puncture-resistant layer 20 using its smooth surface, the size of the electrode assembly 100 in the stacking direction X can be reduced, the space occupied by the electrode assembly 100 in the battery cell can be reduced, and further the volume of the battery cell can be reduced, which helps to increase the number of battery cells included in the battery per unit volume and is beneficial to improving the energy density of the battery.

[0082] It can be understood that for an electrode sheet with a single-sided active layer structure, its smooth surface is formed by the current collector of the electrode sheet. The current collector can be a metal current collector, a composite current collector, etc.

[0083] In some embodiments, there is a puncture-resistant layer 20 thermally laminated to the fixed surface of the electrode unit 10. In the conventional battery production process, after the positive electrode sheet 11, the separator 12, and the negative electrode sheet 13 are stacked, they are often fixed together by thermal lamination. At this time, the puncture-resistant layer 20 can be thermally laminated to the electrode unit 10 synchronously, simplifying the process.

[0084] In other embodiments, there is a puncture-resistant layer 20 coated on the fixed surface of the electrode unit 10. On the one hand, the puncture-resistant layer 20 is coated on the fixed surface, and the bonding strength with the fixed surface is good. On the other hand, when the positive electrode sheet 11 or the negative electrode sheet 13 with a single-sided active layer structure forms the fixed surface, the puncture-resistant layer 20 can be directly coated on the smooth surface of the electrode sheet without an active layer, and at this time, the volume occupied by the electrode unit 10 can be greatly reduced.

[0085] It is worth noting that when the fixed surface of a certain electrode unit 10 is formed by the smooth surface of the electrode tab without an active layer in the single-sided active layer structure electrode tab, a puncture-resistant layer 20 can be coated on this smooth surface, and the puncture-resistant layer 20 and another electrode unit 10 adjacent to "this certain electrode unit 10" can be compounded by hot pressing, so that the puncture-resistant layer 20 and the adjacent electrode unit 10 are fixed as a whole.

[0086] In some embodiments, along the stacking direction X, the projection of the electrode unit 10 falls within the projection range of the puncture-resistant layer 20.

[0087] The projection of the electrode unit 10 falling within the projection range of the puncture-resistant layer 20 includes that the projection of the electrode unit 10 completely coincides with the projection of the puncture-resistant layer 20, and also includes that the projection of the puncture-resistant layer 20 extends beyond the projection range of the electrode unit 10.

[0088] It is easy to understand that taking the laminated structure as an example, the length dimension and / or width dimension of the separator 12 in the electrode unit 10 usually exceeds the size of the electrode tab to avoid short circuit caused by contact between the positive electrode tab 11 and the negative electrode tab 13. At this time, the projection of the separator 12 in the stacking direction X should fall within the projection range of the puncture-resistant layer 20, that is, the length dimension of the puncture-resistant layer 20 is not less than the length dimension of the separator 12, and the width dimension of the puncture-resistant layer 20 is not less than the width dimension of the separator 12.

[0089] In this way, the puncture-resistant layer 20 can completely cover the electrode unit 10, and the protection of the electrode unit 10 is more reliable.

[0090] In some embodiments, referring to Figure 6 , a folded edge 20a is formed at the edge of the puncture-resistant layer 20 and is bent along the stacking direction X, and the folded edge 20a is fixedly connected to the separator 12 in the electrode unit 10.

[0091] Specifically, the folded edge 20a can be fixedly connected to the outer edge surface of the separator 12 by means of hot pressing compounding or bonding. The outer edge surface of the separator 12 refers to the edge surface parallel to its thickness direction.

[0092] At this time, the setting of the folded edge 20a of the puncture-resistant layer 20 can strengthen its fixing reliability with the electrode unit 10 and reduce the sliding of the puncture-resistant layer 20 on the electrode unit 10.

[0093] Specifically, when the electrode assembly 100 is a wound structure, the folded edge 20a is located in the width direction of the puncture-resistant layer 20 that is substantially perpendicular to its winding direction. When the electrode assembly 100 is a laminated structure, the folded edge 20a can be in the width direction and / or length direction of the puncture-resistant layer 20.

[0094] Taking the laminated structure as an example, during actual production, the puncture-resistant layer 20, the separator 12, the positive electrode sheet 11, and the negative electrode sheet 13 can be laminated in a relevant order and then hot-pressed and compounded together along the lamination direction X. Then, a folded edge 20a of the puncture-resistant layer 20 is hot-pressed out, and the folded edge 20a is compounded with the outer edge surface of a part of the separator 12.

[0095] In some embodiments, the puncture-resistant layer 20 is configured not to allow ions to pass through.

[0096] That is, when the electrode assembly 100 undergoes an electrochemical reaction, lithium ions cannot pass through the puncture-resistant layer 20. At this time, the processing requirements for the puncture-resistant layer 20 are relatively low, which is convenient for the processing and manufacturing of the puncture-resistant layer 20. Moreover, when the puncture-resistant layer 20 allows lithium ions to pass through, a microporous structure needs to be processed inside it, and the existence of the microporous structure will reduce the tensile effect of the puncture-resistant layer 20, which is not conducive to preparing a puncture-resistant layer 20 with high ductility.

[0097] It can be understood that in the various drawings provided in this application, the number of electrode units and puncture-resistant layers is only for illustration and does not limit the solution.

[0098] In addition, the embodiments of the present application also provide a battery cell, including a packaging member and the electrode assembly 100 in the above embodiments, and the electrode assembly 100 is accommodated in the packaging member. The packaging member can be a hard shell, a soft aluminum-plastic film, etc., which plays a role in protecting the internal electrode assembly.

[0099] In addition, the embodiments of the present application also provide a battery, which includes the battery cell in the above embodiments.

[0100] The technical features of the above embodiments can be combined arbitrarily. For the sake of brief description, not all possible combinations of the technical features in the above embodiments are described. However, as long as these combinations of technical features do not conflict, they should be considered as the scope described in this specification.

[0101] The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An electrode assembly (100), characterized in that: The electrode assembly (100) comprises: A multilayer electrode unit (10), each layer of the electrode unit (10) comprising a positive electrode sheet (11), a separator (12) and a negative electrode sheet (13) stacked in a stacking direction (X), the separator (12) being arranged between adjacent positive electrode sheets (11) and negative electrode sheets (13); and A multi-layer puncture-resistant layer (20), wherein the puncture-resistant layer (20) and the electrode unit (10) are arranged alternately in sequence in the stacking direction (X), and the puncture-resistant layer (20) is arranged on the outer side of the multi-layer electrode unit (10); Each puncture-resistant layer (20) is configured to be stretched following the puncture of the test probe (200) when punctured by the test probe (200), and to be insulated and isolated between the test probe (200) and the electrode unit (10); and in each of two adjacent puncture-resistant layers (20), the puncture-resistant layer (20) of the outer layer can be stretched to the puncture-resistant layer (20) of the inner layer following the puncture of the test probe (200).

2. The electrode assembly (100) according to claim 1, characterized in that: The elongation at break of each puncture-resistant layer (20) is β, the stacking thickness of each electrode unit (10) is H, and the diameter of the test probe (200) is A, satisfying: β*A ≥ H.

3. The electrode assembly (100) according to claim 2, characterized in that: Satisfies: 5mm≤A≤8mm.

4. The electrode assembly (100) according to claim 2, characterized in that: The puncture resistance strength of the puncture-resistant layer (20) is α, and the tensile strength is θ, satisfying: β ≥ 200%, α ≥ 0.125N / μm,θ ≥ 50MPa.

5. The electrode assembly (100) according to claim 1, characterized in that: The thickness of each puncture-resistant layer (20) is 3 μm to 100 μm.

6. The electrode assembly (100) according to claim 1, characterized in that: The puncture-resistant layer (20) comprises at least one of unmodified or modified PTFE, ETFE, FEP, PFA, PCTFF, ECTFE, PE, and PA.

7. The electrode assembly (100) according to claim 1, characterized in that: The electrode unit (10) has a fixed surface located in the stacking direction (X); the puncture-resistant layer (20) is fixedly connected to the fixed surface of the electrode unit (10); Each of the fixed surfaces is formed by one of the positive electrode sheet (11), the diaphragm (12) and the negative electrode sheet (13); the electrode sheet forming the fixed surface is a double-sided active layer structure or a single-sided active layer structure, and the surface of the electrode sheet with a single-sided active layer structure that is not covered with an active layer forms the fixed surface; The puncture-resistant layer (20) is thermally pressed and laminated to the fixed surface of the electrode unit (10); and / or the puncture-resistant layer (20) is coated on the fixed surface of the electrode unit (10).

8. The electrode assembly (100) according to claim 1, characterized in that: Along the stacking direction (X), the projection of the electrode unit (10) falls within the projection range of the puncture-resistant layer (20); and / or, the edge of the puncture-resistant layer (20) forms a folded edge (20a) bent along the stacking direction (X), and the folded edge (20a) is fixedly connected to the diaphragm (12) in the electrode unit (10); And / or, the puncture-resistant layer (20) is configured to not allow ions to penetrate therethrough.

9. A battery cell, characterized in that: include: Packages; and The electrode assembly (100) according to any one of claims 1 to 8, wherein the electrode assembly (100) is accommodated in the packaging member.

10. A battery, characterized in that: Comprising the battery cell as claimed in claim 9.

Images