Electrode assembly, battery cell, battery and power consuming device

Abstract

The present application provides an electrode assembly, a battery cell, a battery, and a power consuming device. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, and an expansion layer disposed between the positive electrode sheet and the negative electrode sheet that expands under predetermined conditions to interrupt electrical connection between the positive electrode sheet and the negative electrode sheet.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to Chinese Patent Application No. 202310075434.7, entitled "Electrode Assembly, Battery Cell, Battery and Power Consumption Device," filed on January 16, 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] The present application relates to the field of battery technology, and in particular to electrode assemblies, battery cells, batteries, and power consuming devices. [Background technology]

[0003] Batteries, as a new energy source, have become an indispensable energy source for industry and society. With the development of battery technology, batteries are widely used in various fields, such as electronic devices, electric vehicles, power tools, and aerospace equipment. As the need for batteries in these fields increases, the demands for battery performance are also becoming increasingly high. Among these, battery safety performance is attracting attention in various fields as one of the important performance aspects. Therefore, how to improve the safety performance of batteries has become one of the technical challenges that must be solved in the field of battery technology. Summary of the Invention

[0004] The present application provides an electrode assembly, a battery cell, a battery, and a power consuming device that can achieve excellent safety performance of the battery.

[0005] A first aspect of the present application provides an electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator provided between the positive electrode sheet and the negative electrode sheet, and an expansion layer provided between the positive electrode sheet and the negative electrode sheet that expands in response to predetermined conditions so as to interrupt electrical connection between the positive electrode sheet and the negative electrode sheet.

[0006] In the electrode assembly according to the present application, an expansion layer is provided between the positive electrode sheet and the negative electrode sheet. When the electrode assembly is applied to a battery, metal dendrites may form inside the battery during use. When these dendrites grow to a certain extent, they break through the separator, electrically connecting the positive electrode sheet and the negative electrode sheet, causing a short circuit inside the battery. When a predetermined condition is met, the expansion layer expands in accordance with the predetermined condition to spread the short circuit point between the positive electrode sheet and the negative electrode sheet and to envelop the dendrite at the short circuit point, thereby cutting off the electrical connection between the positive electrode sheet and the negative electrode sheet, reducing the occurrence of thermal runaway inside the battery and thereby improving the safety performance of the battery.

[0007] According to any of the above embodiments of the first aspect of the present application, the predetermined conditions include a predetermined temperature and / or a predetermined pressure, which allows the expansion layer to easily react and expand, thereby quickly cutting off the electrical connection between the positive electrode sheet and the negative electrode sheet, further reducing the occurrence of thermal runaway inside the battery, and improving the safety performance of the battery.

[0008] According to any of the above-described embodiments of the first aspect of the present application, the predetermined conditions include a predetermined temperature, which is 80° C. or higher, preferably 110° C. to 150° C. When the predetermined conditions include a predetermined temperature and the predetermined temperature is in the above-described range, the expansion layer can more easily react and expand in accordance with the predetermined conditions, thereby further reducing the occurrence of thermal runaway inside the battery and further improving the safety performance of the battery.

[0009] According to any of the above-described embodiments of the first aspect of the present application, the expansion layer has a thicknesswise expansion coefficient of 50% to 2000%, preferably 150% to 1000%, under predetermined conditions. When the expansion layer has an expansion coefficient within the above range, it can spread out many short-circuit points and encapsulate dendrites at many short-circuit points, thereby isolating many electrical connection points between the positive electrode sheet and the negative electrode sheet, further reducing the occurrence of thermal runaway inside the battery and advantageously improving the safety performance of the battery.

[0010] According to any of the above-described embodiments of the first aspect of the present application, the expandable layer includes thermally expandable particles and a conductive agent, and the mass ratio of the thermally expandable particles to the conductive agent, based on the mass of the expandable layer, is (1 to 6): 1. When the expandable layer includes thermally expandable particles and a conductive agent, and the mass ratio of the thermally expandable particles to the conductive agent satisfies the above relationship, it contributes to reducing the occurrence of thermal runaway in the battery, and also reduces the resistance of the expandable layer, thereby improving the safety performance and cycle performance of the battery.

[0011] According to any of the above-described embodiments of the first aspect of the present application, the mass ratio of the thermally expandable particles in the expandable layer is 60% to 85%. When the mass ratio of the thermally expandable particles in the expandable layer is in the above range, it contributes to reducing thermal runaway of the battery and can improve the safety performance of the battery.

[0012] According to any of the above-described embodiments of the first aspect of the present application, the mass ratio of the conductive agent in the expansion layer is 15% to 35%. When the mass ratio of the conductive agent in the expansion layer is in the above range, the resistance of the expansion layer is reduced, and the cycle performance of the battery can be improved.

[0013] According to any of the above embodiments of the first aspect of the present application, the material of the thermally expandable particles comprises one or more of polyacrylonitrile, polymethacrylonitrile, N,N'-dimethyl-N,N'-dinitrosoterephthalamide, barium azodicarboxylate, and diisopropyl azodicarboxylate.

[0014] According to any of the above-described embodiments of the first aspect of the present application, the expandable layer further comprises a predetermined temperature regulator, and the mass ratio of the predetermined temperature regulator in the expandable layer is 0.1% to 15%, preferably 0.5% to 10%. When the expandable layer comprises the predetermined temperature regulator and the mass ratio of the predetermined temperature regulator in the expandable layer is within the above range, this contributes to improving the reaction sensitivity of the expandable layer and further contributes to improving the safety performance of the battery.

[0015] According to any of the above embodiments of the first aspect of the present application, the predetermined temperature regulator comprises one or more of vinylidene chloride, acrylic acid ester, methacrylonitrile, sodium chloride, citric acid, and potassium dichromate.

[0016] According to any of the above-described embodiments of the first aspect of the present application, the expansion layer is provided on the side of the negative electrode sheet facing the separator.

[0017] According to any of the above-described embodiments of the first aspect of the present application, the expansion layer is provided on the side of the positive electrode sheet facing the separator.

[0018] According to any of the above embodiments of the first aspect of the present application, the expansion layer is provided on the separator side.

[0019] According to any of the above embodiments of the first aspect of the present application, the expansion layer includes one or more of a striped expansion layer, a mesh expansion layer, and a dotted expansion layer, and when the expansion layer has the above shape, it can contribute to improving the safety performance and cycle performance of the battery.

[0020] According to any of the above-described embodiments of the first aspect of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector side and containing a positive electrode active material, and a thickness H1 of the expansion layer, a thickness H2 of the separator, and a thickness H3 of the positive electrode sheet satisfy the following formula: α*H1+(A*H3*ρ a ) / (B / ρb)≦H2

[0021] In the formula, α represents the expansion rate of the expansion layer in the thickness direction under specified conditions, A represents the gram capacity of the positive electrode sheet, and ρ a represents the density of the positive electrode active material, B represents the gram capacity of sodium metal, and ρ brepresents the density of sodium metal. When the thickness H1 of the expansion layer, the thickness H2 of the separator, and the thickness H3 of the positive electrode sheet satisfy the above relationship, the expansion layer can push out the dendrites at the short-circuit point between the positive electrode sheet and the negative electrode sheet after expansion, and reduce the probability of the separator being broken by the dendrites formed in other areas, thereby further improving the safety performance of the battery.

[0022] According to any of the above embodiments of the first aspect of the present application, α is between 150% and 2000%, and / or A is between 90 mAh / g and 150 mAh / g.

[0023] According to any of the above-described embodiments of the first aspect of the present application, the thickness H1 of the expansion layer is 0.1 μm to 10 μm. When the thickness of the expansion layer is in the above range, the expansion layer can spread the dendrites at the short-circuit point between the positive electrode sheet and the negative electrode sheet after expansion, and can reduce the probability of the separator being broken by the dendrites formed in other areas, thereby further improving the safety performance of the battery.

[0024] According to any of the above-described embodiments of the first aspect of the present application, the thickness H2 of the separator is 9 μm to 50 μm. A thickness of the separator in the above range contributes to reducing the probability of the separator being broken by dendrites, which is advantageous for improving the safety performance of the battery.

[0025] According to any of the above-described embodiments of the first aspect of the present application, the thickness H3 of the positive electrode sheet is 50 μm to 300 μm. When the thickness of the positive electrode sheet is in the above range, it contributes to reducing breakage of the separator due to dendrites and can improve the cycle performance of the battery.

[0026] According to any of the above-described embodiments of the first aspect of the present application, the separator has an air permeability of 120s / 100cc to 180s / 100cc.

[0027] According to any of the above-described embodiments of the first aspect of the present application, the separator has a puncture strength of 0.05 N / μm to 0.5 N / μm.

[0028] According to any of the above embodiments of the first aspect of the present application, the separator has an elongation at break of 7% or more.

[0029] According to any of the above embodiments of the first aspect of the present application, the separator has a longitudinal tensile strength of 120 MPa or more.

[0030] According to any of the above-described embodiments of the first aspect of the present application, the separator has a transverse tensile strength of 10 MPa or more, preferably 20 MPa to 80 MPa.

[0031] According to any of the above embodiments of the first aspect of the present application, the areal density of the separator is 3 g / m 2 ~6g / m 2 is.

[0032] According to any of the above embodiments of the first aspect of the present application, the separator comprises a pore structure of a plurality of pores, and the porosity of the separator is between 20% and 50%.

[0033] A second aspect of the present application provides a battery cell including an electrode assembly according to the first aspect of the present application.

[0034] A third aspect of the present application provides a battery including a battery cell according to the second aspect of the present application.

[0035] A fourth aspect of the present application provides a power consuming device including a battery according to the third aspect of the present application.

[0036] The above description is only a summary of the technical solution of the present application, which can be implemented according to the content of the specification, in order to make the technical solution of the present application more clearly understood. In addition, in order to facilitate a clearer understanding of the above and other objectives, features and advantages of the present application, specific embodiments of the present application are listed below. [Brief explanation of the drawings]

[0037] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of alternative embodiments. The drawings are for illustrative purposes only and are not intended to limit the scope of the present application. In addition, like elements are designated by like reference numerals throughout the drawings. In the drawings: [Figure 1] 1 is a schematic structural diagram of a battery cell according to some embodiments of the present application; [Figure 2] FIG. 2 is an exploded view of the battery cell of FIG. 1. [Figure 3] 1 is a schematic structural diagram of a battery module according to some embodiments of the present application; [Figure 4] 1 is a schematic structural diagram of a battery pack according to some embodiments of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack of FIG. [Figure 6] 1 is a schematic structural diagram of a power consuming device according to some embodiments of the present application.The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, the embodiments of the technical solution of the present application will be described in detail with reference to the drawings. The following embodiments are merely provided as examples to more clearly explain the technical solution of the present application, and are not intended to limit the protection scope of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are only for describing particular embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof contained in the specification, claims, and description of the drawings of this application are intended to cover a non-exclusive inclusion.

[0040] In the description of the embodiments of the present application, technical terms such as "first" and "second" are merely used to distinguish different objects, and should not be understood to indicate or imply relative importance, or to imply the number or specific order of the indicated technical features, or their hierarchical relationship. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise clearly and specifically limited.

[0041] The term "embodiment" used herein means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The phrases appearing in various parts of the present specification do not necessarily refer to the same embodiment, nor are they mutually exclusive, independent, or alternative embodiments. Those skilled in the art may explicitly or implicitly understand that the embodiments described herein can be combined with other embodiments.

[0042] In the description of the examples of this application, the term "and / or" only describes the relationship between related objects and indicates that three types of relationships may exist. For example, A and / or B indicates that three situations may exist: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this specification generally indicates that the related objects before and after it are in an "or" relationship.

[0043] In describing the examples of the present application, the term "plurality" means two or more (including two); similarly, "multiple sets" means two or more (including two sets), and "plurality" means two or more (including two).

[0044] In describing the examples of the present application, the orientations or positional relationships indicated by technical terms such as "center," "longitudinal," "lateral," "length," "width," "wall thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are based on the orientations or positional relationships shown in the drawings, and are intended merely for the convenience and simplification of the description of the examples of the present application, and do not indicate or imply that the devices or elements shown must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be understood as limiting the examples of the present application.

[0045] In the description of the embodiments of the present application, unless otherwise clearly specified or limited, technical terms such as "attached," "coupled," "connected," and "fixed" should be understood in a broad sense, and may refer to, for example, a fixed connection, a detachable connection, or integration, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediate medium, internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application according to the specific circumstances.

[0046] In this application, a battery is primarily composed of one or more battery cells, each of which includes a case, an end cover, and an electrode assembly housed within the case. The electrode assembly is a component where an electrochemical reaction occurs within the battery cell. Specifically, the electrode assembly is primarily formed by winding or stacking a positive electrode sheet and a negative electrode sheet, and a separator is usually provided between the positive electrode sheet and the negative electrode sheet.

[0047] During the charge and discharge process of a battery, metal ions are unevenly deposited on the surface of the negative electrode sheet, and as the number of charge and discharge cycles of the battery increases, dendrites are formed. If these dendrites grow excessively and break through the separator, a short circuit will occur between the positive and negative electrode sheets, which may further pose risks such as fire or explosion, and may reduce the safety performance of the battery.

[0048] In view of this, the present application provides an electrode assembly, a battery cell, a battery, and a power consuming device that can achieve excellent safety performance of the battery.

[0049] Electrode Assembly A first aspect of the present application provides an electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator provided between the positive electrode sheet and the negative electrode sheet, and an expansion layer provided between the positive electrode sheet and the negative electrode sheet that expands in response to predetermined conditions so as to interrupt electrical connection between the positive electrode sheet and the negative electrode sheet.

[0050] In the electrode assembly according to the present application, an expansion layer is provided between the positive electrode sheet and the negative electrode sheet. When the electrode assembly is applied to a battery, metal dendrites may form inside the battery during use. When these dendrites grow to a certain extent, they break through the separator, electrically connecting the positive electrode sheet and the negative electrode sheet, causing a short circuit inside the battery. When a predetermined condition is met, the expansion layer expands in accordance with the predetermined condition to spread the short circuit point between the positive electrode sheet and the negative electrode sheet and to encapsulate the dendrite at the short circuit point, thereby cutting off the electrical connection between the positive electrode sheet and the negative electrode sheet and reducing the occurrence of thermal runaway inside the battery, thereby improving the safety performance of the battery.

[0051] In some embodiments of the present application, the predetermined conditions include a predetermined temperature and / or a predetermined pressure, which allows the expansion layer to easily react and expand, quickly cutting off the electrical connection between the positive electrode sheet and the negative electrode sheet, further reducing the occurrence of thermal runaway inside the battery, and improving the safety performance of the battery.

[0052] In some embodiments of the present application, the predetermined conditions include a predetermined temperature, and the predetermined temperature is 80° C. or higher, preferably 110° C. to 150° C. When the predetermined conditions include a predetermined temperature and the predetermined temperature is in the above range, the expansion layer can more easily react and expand in accordance with the predetermined conditions, thereby further reducing the occurrence of thermal runaway inside the battery and further improving the safety performance of the battery.

[0053] In some examples, the predetermined temperature is 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, 110°C, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C , 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, 131°C, 132°C, 133°C, 134°C, 135°C, 136°C, 137°C, 138°C, 139°C, 140°C, 141°C, 142°C, 143°C, 144°C, 145°C, 146°C, 147°C, 148°C, 149°C, 150°C, or a range consisting of any two of the above values, but are not limited thereto. For example, the predetermined temperature range may be, but is not limited to, 81°C to 148°C, 85°C to 145°C, 88°C to 140°C, 92°C to 134°C, 95°C to 130°C, 99°C to 125°C, or 102°C to 120°C.

[0054] In some embodiments of the present application, the expansion layer has a thicknesswise expansion rate of 50% to 2000%, preferably 150% to 1000%, under certain conditions. When the expansion layer has an expansion rate within the above range, it can spread out many short-circuit points and encapsulate dendrites at many short-circuit points, further isolating many electrical connection points between the positive electrode sheet and the negative electrode sheet, further reducing the occurrence of thermal runaway inside the battery, and advantageously improving the safety performance of the battery.

[0055] In this application, the expansion coefficient refers to the difference between the thickness of the coating after expansion and the thickness of the coating before expansion, expressed as a percentage of the thickness of the coating before expansion. This coefficient can be measured by methods well known in the art. For example, the expansion coefficient can be measured as follows: A separator (1 cm × 1 cm) coated with an expansion layer is taken, and the remaining electrolyte solution on the surface is washed off with absolute ethanol. The separator is then placed in a vacuum drying oven at 45°C and dried for 60 minutes. The thickness Ha of the expansion layer is measured on the cross section of the separator using SEM. The separator is then placed in an environment at the trigger temperature of the expansion layer (e.g., 120°C) and allowed to stand for 30 minutes. The separator is then removed and cooled for 30 minutes. The thickness Hb of the expansion layer is then measured on the cross section of the separator using SEM. The expansion coefficient is then calculated based on the following formula: Expansion coefficient = (Hb - Ha) / Ha × 100%.

[0056] In some examples, the expansion rate through the thickness of the expansion layer under specified conditions is 50%, 100%, 150%, 200%, 250%, 300%, 350%, 400%, 450%, 500%, 550%, 600%, 650%, 700%, 750%, 800%, 850%, 900%, 950%, 1000%, 1050%, 1100%, 1150%, 1160%, 1170%, 1180%, 1190%, 1200%, 1210%, 1220%, 1230%, 1240%, 1250%, 1260%, 1270%, 1280%, 1290%, 1300%, 1310%, 1320%, 1330%, 1340%, 1350%, 1360%, 1370%, 1380%, 1390%, 1400%, 1410%, 1420%, 1430%, 1440%, 1450%, 1460%, 1470%, 1480%, 1490%, 1500%, 1510%, 1520%, 1530%, 1540%, 1550%, 1560%, 1570%, 1580%, 1590%, 1600%, 1610%, 1620%, 1630%, 1640%, 1650%, 1660%, 1670%, 1680%, 1690%, 1700%, 1710%, 1720%, 1730%, 1740%, 1750%, 1760%, 1770%, 17 The expansion rate of the expandable layer in the thickness direction under certain conditions may be, but is not limited to, 50%, 1200%, 1250%, 1300%, 1350%, 1400%, 1450%, 1500%, 1550%, 1600%, 1650%, 1700%, 1750%, 1800%, 1850%, 1900%, 1950%, 2000%, or a range consisting of any two of the above values. For example, the expansion rate of the expandable layer in the thickness direction under certain conditions may be, but is not limited to, 100% to 1950%, 150% to 1800%, 250% to 1700%, 300% to 1600%, 400% to 1550%, 550% to 1400%, 600% to 1350%, or 700% to 1250%.

[0057] In some embodiments of the present application, the expandable layer includes thermally expandable particles and a conductive agent, and the mass ratio of the thermally expandable particles to the conductive agent, based on the mass of the expandable layer, is (1 to 6): 1. When the expandable layer includes thermally expandable particles and a conductive agent, and the mass ratio of the thermally expandable particles to the conductive agent satisfies the above relationship, it contributes to reducing the occurrence of thermal runaway in the battery, reduces the resistance of the expandable layer, and improves the safety performance and cycle performance of the battery.

[0058] In some embodiments of the present application, the mass ratio of the thermally expandable particles in the expandable layer is 60% to 85%. When the mass ratio of the thermally expandable particles in the expandable layer is in the above range, it contributes to reducing thermal runaway of the battery and can improve the safety performance of the battery.

[0059] In some examples, the mass ratio of the thermally expandable particles in the expandable layer may be, but is not limited to, 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%, or a range consisting of any two of the foregoing values. For example, the mass ratio of the thermally expandable particles in the expandable layer may be in the range of 61% to 84%, 64% to 80%, or 67% to 76%.

[0060] In some embodiments of the present application, the mass ratio of the conductive agent in the expansion layer is 15% to 35%. When the mass ratio of the conductive agent in the expansion layer is in this range, it contributes to reducing the resistance of the expansion layer and can improve the cycle performance of the battery.

[0061] In some examples, the weight ratio of the conductive agent in the expandable layer may be, but is not limited to, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or a range consisting of any two of the foregoing values. For example, the weight ratio of the conductive agent in the expandable layer may be in the range of 16% to 34%, 18% to 32%, 20% to 30%, or 21% to 28%.

[0062] In some embodiments of the present application, the material of the thermally expandable particles includes one or more of polyacrylonitrile, polymethacrylonitrile.

[0063] In some embodiments of the present application, the conductive agent may include one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0064] In some embodiments of the present application, the expandable layer further comprises a predetermined temperature regulator, and the mass ratio of the predetermined temperature regulator in the expandable layer is 0.1% to 15%, preferably 0.5% to 10%. When the expandable layer comprises the predetermined temperature regulator and the mass ratio of the predetermined temperature regulator in the expandable layer is within the above range, this contributes to improving the reaction sensitivity of the expandable layer and further contributes to improving the safety performance of the battery.

[0065] In some examples, the mass ratio of the predetermined temperature regulating agent in the expandable layer may be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, or a range consisting of any two of the foregoing values. For example, the mass ratio of the predetermined temperature adjusting agent in the expandable layer may be in the range of 0.5% to 14.5%, 1% to 13.5%, 2% to 12%, 2.5% to 11.5%, 4% to 10.5%, 4.5% to 10%, or 5% to 9%, but is not limited to these.

[0066] In some embodiments of the present application, the predetermined temperature adjusting agent comprises one or more of vinylidene chloride, acrylic acid ester, methacrylonitrile, sodium chloride, citric acid, and potassium dichromate.

[0067] In some other embodiments of the present application, the expansion layer further comprises a hydrophilic polar monomer, which contributes to enhancing the puncture strength of the expansion layer, and further, after expansion, the expansion layer can encapsulate the dendrites at the short circuit point while spreading the short circuit point, thereby further improving the safety performance of the battery.

[0068] In some examples, the hydrophilic monomer may be a monomer such as, but not limited to, methacrylic acid, acrylamide, and the like.

[0069] In some embodiments of the present application, the expansion layer is provided on the separator-facing side of the negative electrode sheet, which can contribute to quickly expanding the dendrites at the short circuit point after expansion, further reducing the occurrence of thermal runaway and improving the safety performance of the battery.

[0070] In some embodiments of the present application, the expansion layer is provided on the separator-facing side of the positive electrode sheet, and such an expansion layer can help to encapsulate the dendrites at the short circuit point after expansion, further cutting off the electrical connection between the positive electrode sheet and the negative electrode sheet, reducing the occurrence of thermal runaway, and improving the safety performance of the battery.

[0071] In some embodiments of the present application, the expansion layer is provided on the separator side, and such an expansion layer can help to encapsulate the dendrites at the short circuit point after expansion, further cutting off the electrical connection between the positive electrode sheet and the negative electrode sheet, reducing the occurrence of thermal runaway, and improving the safety performance of the battery.

[0072] In some embodiments of the present application, the expansion layer includes one or more of a striped expansion layer, a mesh expansion layer, and a dotted expansion layer. When the expansion layer has the above-mentioned shape, it can contribute to improving the safety performance and cycle performance of the battery.

[0073] The expansion layer may include one of a mesh expansion layer, a dot expansion layer, and a stripe expansion layer, or a combination of two or more of these, but it should be understood that the embodiments of the present application are not specifically limited thereto.

[0074] In this application, the shape of the intumescent layer may be characterized by methods known in the art, for example, a scanning electron microscope (SEM) may be used to observe the shape of the intumescent layer.

[0075] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector side and containing a positive electrode active material, and the thickness H1 of the expansion layer, the thickness H2 of the separator, and the thickness H3 of the positive electrode sheet satisfy the following formula: α*H1+(A*H3*ρ a ) / (B / ρ b )≦H2

[0076] In the formula, α represents the expansion rate of the expansion layer in the thickness direction under specified conditions, A represents the gram capacity (capacity per gram) of the positive electrode sheet, and ρ a represents the density of the positive electrode active material, B represents the gram capacity (capacity per gram) of sodium metal, and ρ b represents the density of sodium metal.

[0077] It should be understood that the sum of the expanded thickness of the expansion layer and the length of the formed dendrites is equal to or less than the thickness of the separator; in this way, the expansion layer can push out the dendrites at the short-circuit points between the positive electrode sheet and the negative electrode sheet after expansion, and can also reduce the probability of the separator being ruptured by the dendrites formed in other areas, thereby further improving the safety performance of the battery.

[0078] In this application, the thickness of the expansion layer, the thickness of the separator, and the thickness of the positive electrode sheet all have the meanings known in the art, and can be measured using a method known in the art, for example, using a micrometer (e.g., Mitutoyo 293-100 type, accuracy 0.1 μm).

[0079] In some embodiments of the present application, α is 150% to 2000%, and / or A is 90 mAh / g to 150 mAh / g. When α is within the above range, the expansion layer can contribute to spreading dendrites at the short-circuit point between the positive electrode sheet and the negative electrode sheet after expansion. When A is within the above range, it contributes to shortening the length of the dendrites, and further reduces the risk of the separator being ruptured by these dendrites coming into contact with the expansion layer after expansion, thereby further improving the safety performance of the battery.

[0080] In some embodiments of the present application, the thickness H1 of the expansion layer is 0.1 μm to 10 μm. When the thickness of the expansion layer is in this range, the expansion layer can spread the dendrites at the short-circuit point between the positive electrode sheet and the negative electrode sheet after expansion, and reduce the probability of the separator being broken by the dendrites formed in other areas, thereby further improving the safety performance of the battery.

[0081] In some examples, the thickness of the intumescent layer may be, but is not limited to, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or a range consisting of any two of the foregoing values. For example, the thickness of the intumescent layer may be, but is not limited to, 0.5 μm to 9.5 μm, 1 μm to 9 μm, 1.5 μm to 8.5 μm, 2 μm to 8 μm, 2.5 μm to 7.5 μm, or 3 μm to 6.5 μm.

[0082] In some embodiments of the present application, the thickness H2 of the separator is 9 μm to 50 μm. When the thickness of the separator is in the above range, it contributes to reducing the probability of the separator being broken by dendrites, which is advantageous for improving the safety performance of the battery.

[0083] In some examples, the thickness of the separator can be, but is not limited to, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, or a range consisting of any two of the foregoing values. For example, the thickness of the separator may be in the range of 10 μm to 48 μm, 13 μm to 45 μm, 15 μm to 41 μm, 18 μm to 38 μm, 20 μm to 36 μm, 23 μm to 33 μm, or 25 μm to 31 μm, but is not limited to these.

[0084] In some embodiments of the present application, the thickness H3 of the positive electrode sheet is 50 μm to 300 μm. When the thickness of the positive electrode sheet is in this range, it contributes to reducing separator breakage caused by dendrites and can improve the cycle performance of the battery.

[0085] In some embodiments of the present application, the separator has an air permeability of 120s / 100cc to 180s / 100cc. When the air permeability of the separator is in the above range, the separator can have excellent air permeability, which can improve ion transport properties, reduce battery resistance, and improve battery cycle performance.

[0086] In some embodiments of the present application, the separator has a puncture strength of 0.05 N / μm to 0.5 N / μm.

[0087] In some embodiments of the present application, the separator has an elongation at break of 7% or greater.

[0088] In some embodiments of the present application, the separator has a longitudinal tensile strength of 120 MPa or more.

[0089] In some embodiments of the present application, the separator has a transverse tensile strength of 10 MPa or more, preferably 20 MPa to 80 MPa.

[0090] In this application, the air permeability, puncture strength, elongation at break, and tensile strength of the separator all have meanings known in the art and can be measured by methods known in the art, for example, by testing in accordance with standard GB / T36363-2018.

[0091] In some embodiments of the present application, the areal density of the separator is 3 g / m 2 ~6g / m 2 is.

[0092] In some embodiments of the present application, the separator comprises a pore structure of a plurality of pores, and the porosity of the separator is 20% to 50%.

[0093] In this application, porosity has the meaning known in the art and refers to the ratio of the pore volume within a material to the total volume of the material. It can be measured using instruments and methods known in the art. For example, see Chinese National Standard GB / T24586-2009 entitled "Determination of Apparent Density, True Density, and Porosity of Iron Ore." Porosity can be measured using an AccuPyc II 1340 fully automatic true density tester manufactured by Micromeritics, Inc., USA. Porosity = (V1 - V2) / V1 * 100%, where V1 represents the apparent volume of the material and V2 represents the true volume of the material. V1 can be measured by mercury intrusion porosimetry, and V2 can be measured by nitrogen gas adsorption.

[0094] In the embodiments of the present application, the material of the separator is not particularly limited, and any known separator with excellent chemical and mechanical stability can be used. For example, the separator can include one or more of a porous polyolefin resin film (e.g., one or more of polyethylene, polypropylene, and polyvinylidene fluoride), a porous glass fiber, and a porous nonwoven fabric. The porous separator may be a single-layer film or a multilayer composite film. When the porous separator is a multilayer composite film, the materials of the layers may be the same or different.

[0095] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector side and containing a positive electrode active material. In the embodiments of the present application, the positive electrode current collector and the positive electrode active material are not particularly limited, and any positive electrode current collector and positive electrode active material known in the art can be used.

[0096] In some embodiments of the present application, the positive electrode active material may include one or more of a sodium transition metal oxide, a polyanion-type compound, and a Prussian blue-based compound. In other embodiments of the present application, other known materials that can be used as positive electrode active materials in sodium-ion batteries may be used.

[0097] In some examples, the transition metal in the sodium transition metal oxide may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide may include Na x In the case of MO2, M may be one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 <x≦1。

[0098] In some other examples, the polyanionic compound comprises sodium ions, transition metal ions, and tetrahedral (YO4) n-and n is a group of compounds having an anionic unit, wherein the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may include one or more of P, S, and Si, and n is a group of compounds having anionic units, wherein the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and ... n- represents the valence of

[0099] Polyanionic compounds include sodium ions, transition metal ions, and tetrahedral (YO4) n- and n is a group of compounds having an anionic unit and a halogen anion, wherein the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may include one or more of P, S, and Si, and n is (YO4) n- The halogen may include one or more of F, Cl and Br.

[0100] In some specific embodiments, the polyanionic compounds are NaFePO, NaV(PO), NaM'POF (where M' comprises one or more of V, Fe, Mn, and Ni), and Na(VO)(PO)F. 3-2y (0≦y≦1) may be included.

[0101] In some examples, the Prussian blue-based compound may be a compound group having a sodium ion, a transition metal ion, and a cyanuric ion (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue-based compound may be, for example, Na a Me b Me' c (CN)6, wherein Me and Me' each independently comprise one or more of Ni, Cu, Fe, Mn, Co, and Zn; <a≦2、0<b<1、0<c<1。

[0102] In some embodiments of the present application, the positive electrode active material layer may further include a conductive agent and an adhesive. In the embodiments of the present application, the types of the conductive agent and adhesive included in the positive electrode active material layer are not particularly limited and can be selected according to actual needs.

[0103] For 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 adhesive may be, but is not limited to, one or more of styrene butadiene rubber (SBR), water-based 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).

[0104] In some embodiments of the present application, the positive electrode current collector may be made of a material such as a metal foil or a porous metal plate. For example, the positive electrode current collector may be made of a foil or a porous plate made of a metal such as copper, nickel, titanium, or silver, or an alloy thereof, but is not limited to these. Furthermore, in some specific embodiments of the present application, aluminum foil is used as the positive electrode current collector.

[0105] In an embodiment of the present application, a positive electrode sheet is produced by thoroughly mixing a positive electrode active material, a conductive agent, and an adhesive at a certain mass ratio in an appropriate amount of N-methylpyrrolidone (NMP) with stirring to form a uniform positive electrode slurry, and then applying the resulting positive electrode slurry to the surface of an aluminum foil serving as a positive electrode current collector, followed by drying, cold pressing, and die cutting.

[0106] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector. In some examples, the negative electrode current collector may be made of an electronically conductive material. For example, the negative electrode current collector may be made of copper foil, nickel foil, stainless steel foil, or the like.

[0107] In some embodiments of the present application, the negative electrode sheet may further include a negative electrode active material layer provided on the negative electrode current collector side and including a negative electrode active material. However, the type of negative electrode active material is not particularly limited and can be selected by those skilled in the art according to actual needs. For example, the negative electrode active material may include one or more of a carbon material, an alloy material, a transition metal oxide, a transition metal sulfide, a phosphorus-based material, and a titanate material. In some specific embodiments, the negative electrode active material includes a carbon material.

[0108] In some examples, the carbon material may include one or more of natural graphite, artificial graphite, mesophase carbon microspheres (MCMB), hard carbon, and soft carbon. The alloy material may include one or more of alloy materials consisting of multiple elements of Si, Ge, Sn, Pb, and Sb. The chemical formula of the transition metal oxide may be, for example, M 1 u O v where M 1 may be one or more selected from Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb and V, and au=2v, a is M 1 The chemical formula of a transition metal sulfide is, for example, M 2 i S j and M 2 may contain one or more of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb and V, where b i = 2j, b is M 2 The phosphorus-based material may include one or more of red phosphorus, white phosphorus, and black phosphorus. The titanate material may include Na2Ti3O7, Na2Ti6O 13 , Na4Ti5O 12 , Li4Ti5O 12, NaTi2(PO4)3.

[0109] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent and an adhesive. In embodiments of the present application, the types of the conductive agent and adhesive in the negative electrode active material layer are not particularly limited and can be selected according to actual needs.

[0110] For example, the conductive agent may be one or more of, but is not limited to, graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The adhesive may be one or more of, but is not limited to, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0111] In an embodiment of the present application, a negative electrode sheet is produced by mixing a negative electrode active material, a conductive agent, and an adhesive at a certain mass ratio, thoroughly stirring the mixture with an appropriate amount of deionized water to form a uniform negative electrode slurry, and then applying the obtained negative electrode slurry to the surface of a negative electrode current collector, followed by drying, cold pressing, and diamond cutting.

[0112] In an embodiment of the present application, the electrode assembly can be manufactured using a method well known in the art, for example, by performing a winding process and / or a stacking process on a positive electrode sheet, a separator, and a negative electrode sheet, and an expansion layer is applied to at least one of the positive electrode sheet, the separator, and the negative electrode sheet.

[0113] Battery cell A second aspect of the present application provides a battery cell including an electrode assembly according to the first aspect of the present application.

[0114] In some embodiments of the present application, the battery cell further includes an electrolyte, and the electrolyte includes an organic solvent and an electrolyte sodium salt. The types of the electrolyte sodium salt and the organic solvent are not particularly limited and can be selected according to actual needs. The electrolyte may include an organic solvent and an electrolyte sodium salt.

[0115] In some embodiments of the present application, the organic solvent comprises an ethereal organic solvent, for example, the ethereal organic solvent comprises one or more of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether, tetrahydrofuran.

[0116] In some embodiments of the present application, the molar concentration of the electrolyte sodium salt in the electrolyte solution is 0.5 mol / L to 3 mol / L, and the electrolyte sodium salt may include one or more of sodium hexafluorophosphate, sodium fluoroborate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, and sodium disoxalate borate.

[0117] In some embodiments of the present application, the electrolyte solution may further contain additives as needed. For example, the additives may include a film-forming additive for the negative electrode, a film-forming additive for the positive electrode, or an additive capable of improving some performance of the battery cell, such as the overcharge performance, high-temperature performance, or low-temperature output performance of the battery cell.

[0118] In some embodiments of the present application, the battery cell may further include an exterior structure, which may be used to package the electrode assembly and the electrolyte.

[0119] In some embodiments of the present application, the exterior structure of the battery cell may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior structure of the battery cell may be a soft pack, for example, a bag-shaped soft pack. The material of the soft pack may be plastic, for example, at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0120] In the present application, the shape of the battery cell is not particularly limited, and it may be cylindrical, rectangular, or any other shape. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0121] In some embodiments of the present application, as shown in FIG. 2 , the exterior structure may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and a side plate connected to the bottom plate, and a storage cavity is formed by the bottom plate and the side plate. The case 51 has an opening communicating with the storage cavity, and the cover plate 53 covers the opening to seal the storage cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be wound and / or stacked to form an electrode assembly 52. ​​The electrode assembly 52 is packaged in the storage cavity. The electrode assembly 52 is impregnated with an electrolyte. The number of electrode assemblies 52 included in the battery cell 5 may be one or more, and may be increased or decreased according to needs.

[0122] The method for manufacturing the battery cell of the present application is a known method. In some embodiments of the present application, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. For example, the battery cell can be manufactured by forming the positive electrode sheet, the separator, the expansion layer, and the negative electrode sheet into an electrode assembly through a winding process and / or a lamination process, placing the formed electrode assembly in an exterior structure, injecting an electrolyte after drying, and performing processes such as vacuum packaging, standing, chemical conversion, and shaping.

[0123] battery A third aspect of the present application provides a battery including a battery cell according to the second aspect of the present application.

[0124] In embodiments of the present application, a battery may include multiple battery cells to meet different power usage requirements. A battery cell refers to the smallest unit constituting a battery module or a battery pack. Multiple battery cells are connected in series and / or parallel via electrode terminals and can be used for various applications. A battery according to embodiments of the present application includes a battery module or a battery pack. Here, multiple battery cells can be connected in series, parallel, or series-parallel, and a series-parallel connection refers to a combination of series and parallel connections. In embodiments of the present application, multiple battery cells may directly constitute a battery pack, or may first constitute a battery module and then constitute the battery pack using the battery module.

[0125] In some embodiments of the present application, the battery cells according to the second aspect of the present application may be assembled into a battery module, and the number of battery cells included in the battery module may be multiple, and the specific number may be increased or decreased depending on the application and capacity of the battery module.

[0126] Fig. 3 is a schematic diagram of an example battery module. As shown in Fig. 3, in a battery module 4, a plurality of battery cells 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, the battery cells 5 may be arranged in any other manner. Furthermore, the plurality of battery cells 5 may be fixed with fasteners.

[0127] Preferably, the battery module 4 may further include a housing having an accommodation space in which the plurality of battery cells 5 are accommodated.

[0128] In some embodiments of the present application, the above battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be increased or decreased depending on the application and capacity of the battery pack.

[0129] 4 and 5 are schematic diagrams of an example battery pack. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is provided to cover the lower housing 3, forming an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in any manner within the battery box.

[0130] power consumption equipment A fourth aspect of the present application provides a power consuming device including one or more of the battery cells, battery modules, or battery packs according to the second aspect of the present application, which may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device.

[0131] In the present application, the power consuming devices may be, but are not limited to, mobile phones, tablet computers, laptops, electric toys, power tools, electric bicycles, electric vehicles, boats, aircraft, energy storage systems, etc. However, the electric toys may include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric boat toys, and electric plane toys, and the aircraft may include airplanes, rockets, space shuttles, spaceships, etc.

[0132] Furthermore, the power consuming device may select a battery cell, a battery module, or a battery pack according to its usage needs.

[0133] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or battery module can be used to meet the high power and high energy density requirements of the power consuming device.

[0134] The following examples are provided to more fully describe the contents disclosed in the present application, and are merely illustrative, as it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the contents disclosed in the present application. All reagents used in the examples may be commercially available or may be synthesized according to conventional methods and may be used as is without further treatment. All equipment used in the examples is commercially available.

[0135] Example 1 Positive electrode sheet manufacturing A mixture of NaMnKFe(CN)6, a positive electrode active material, acetylene black, a conductive agent, and carboxymethyl cellulose, an adhesive, in a mass ratio of 95:2:3 was thoroughly stirred in an appropriate amount of N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry. The formed positive electrode slurry was then applied to the surface of aluminum foil, a positive electrode current collector, followed by drying, cold pressing, and die cutting to produce a positive electrode sheet with a thickness of 175 μm.

[0136] Manufacture of negative electrode sheets A mixture of artificial graphite as the negative electrode active material, acetylene black as the conductive agent, and carboxymethyl cellulose as the adhesive in a mass ratio of 94:5:1 was thoroughly stirred with an appropriate amount of deionized water to form a uniform negative electrode slurry. The formed negative electrode slurry was then applied to the surface of copper foil as the negative electrode current collector, followed by drying, cold pressing, and die cutting to produce a negative electrode sheet.

[0137] Separator A polyethylene film with a thickness of 9 μm was used.

[0138] Expanded layer manufacturing Thermally expandable particles containing polymethacrylonitrile and carboxymethyl cellulose as an adhesive were mixed and stirred at a mass ratio of 1.86:1 to form a slurry, which was then applied to the side of the separator facing the negative electrode sheet and dried to form an expansion layer with a thickness of 1 μm.

[0139] Electrolyte production Ethylene carbonate, sodium hexafluorophosphate, and a boron-containing additive were mixed with stirring in a mass ratio of 85:10:5 to prepare a sodium salt electrolyte solution.

[0140] Manufacture of sodium-ion secondary batteries A sodium ion secondary battery was manufactured by forming a positive electrode sheet, a separator coated with an expansion layer, and a negative electrode sheet into an electrode assembly by a winding process and / or a lamination process, placing the formed electrode assembly in an exterior structure, injecting an electrolyte after drying, and then carrying out processes such as vacuum packaging, leaving it to stand, chemical formation, and shaping.

[0141] Examples 2 to 10 The manufacturing method is similar to that of Example 1 except that the components and contents of the expansion layer are changed.

[0142] Comparative Example 1 The manufacturing method was similar to that of Example 1, except that the electrode assembly did not include an expansion layer.

[0143] Test part (1) Expansion rate test A separator (1 cm × 1 cm) coated with the expansion layer was taken, and the remaining electrolyte on the surface was washed off with absolute ethanol. After that, it was placed in a vacuum drying oven at 45°C and dried for 60 minutes. Then, the thickness Ha of the expansion layer was measured on the cross section of the separator using SEM. Next, the separator was placed in an environment at the trigger temperature of the expansion layer (e.g., 120°C) and left to stand for 30 minutes. Then, it was removed and cooled for 30 minutes. Then, the thickness Hb of the expansion layer was measured on the cross section of the separator using SEM. Finally, the expansion coefficient was calculated based on the equation: Expansion coefficient = (Hb - Ha) / Ha × 100%.

[0144] (2) Overcharge failure test Forty batteries from the same lot were left at 25°C for 2 hours, then discharged at a rate of 0.33C to the rated voltage of 1.5V, and left to rest for another 2 hours. They were then charged at a constant current of 1C to the rated voltage of 4.2V, at which point the battery's electrical charge was 100% SOC and the charge capacity was C1. They were then continuously charged at 1C to a capacity of 0.4C1, at which point the battery's electrical charge was overcharged to 140% SOC. The percentage of batteries that emitted smoke or caught fire during the charging process from 100% SOC to 140% SOC, i.e., the failure rate, was calculated.

[0145] Table 1 shows the relevant parameters and test results of the expandable layers in Examples 1 to 10 and Comparative Example 1, respectively.

[0146] [Table 1]

[0147] According to Table 1, comparing the test results of Examples 1 to 10 and Comparative Example 1, it can be seen that when an expansion layer is provided on the separator side of an electrode assembly according to the present application and the electrode assembly is applied to a battery, metal dendrites may form inside the battery during use. When these dendrites grow to a certain extent, they break through the separator, electrically connecting the positive electrode sheet and the negative electrode sheet, causing a short circuit inside the battery. This satisfies a predetermined condition, and the expansion layer expands in accordance with this predetermined condition to spread the short circuit between the positive electrode sheet and the negative electrode sheet and to envelop the dendrite at the short circuit. This breaks the electrical connection between the positive electrode sheet and the negative electrode sheet, reducing the occurrence of thermal runaway inside the battery, thereby improving the safety performance of the battery.

[0148] It should be noted that the above embodiments are merely illustrative rather than limiting the technical solutions of the present application. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications to the technical solutions described in the above embodiments, or equivalent substitutions for some or all of the technical features therein, are possible, and as long as the essence of the corresponding technical solutions deviates from the scope of the technical solutions of the embodiments of the present application, they should all be included in the scope of the claims and description of the present application. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural contradiction. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions included in the scope of the claims. [Explanation of symbols]

[0149] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 case, 52 electrode assembly, 53 cover plate.

Claims

1. A positive electrode sheet; A negative electrode sheet; a separator provided between the positive electrode sheet and the negative electrode sheet; an expansion layer provided between the positive electrode sheet and the negative electrode sheet, which expands in response to a predetermined condition to cut off electrical connection between the positive electrode sheet and the negative electrode sheet.

2. The electrode assembly of claim 1 , wherein the predetermined conditions include a predetermined temperature and / or a predetermined pressure.

3. The electrode assembly of claim 1 , wherein the predetermined condition includes a predetermined temperature, and the predetermined temperature is 80° C. or higher.

4. The electrode assembly according to claim 1 , wherein the expansion rate of the expansion layer in the thickness direction under the predetermined conditions is 50% to 2000%.

5. 2. The electrode assembly of claim 1, wherein the expansion layer comprises thermally expandable particles and a conductive agent, and a mass ratio of the thermally expandable particles to the conductive agent is (1-6):1 based on the mass of the expansion layer.

6. The mass ratio of the thermally expandable particles in the expandable layer is 60% to 85%; The electrode assembly according to claim 5 , wherein the mass ratio of the conductive agent in the expansion layer is 15% to 35%.

7. 6. The electrode assembly of claim 5, wherein the material of the thermally expandable particles comprises one or more of polyacrylonitrile, polymethacrylonitrile, N,N'-dimethyl-N,N'-dinitrosoterephthalamide, barium azodicarboxylate, and diisopropyl azodicarboxylate.

8. 6. The electrode assembly according to claim 5, wherein the expandable layer further comprises a predetermined temperature adjusting agent, and the mass ratio of the predetermined temperature adjusting agent in the expandable layer is 0.1% to 15%.

9. 9. The electrode assembly of claim 8, wherein the predetermined temperature regulator comprises one or more of vinylidene chloride, acrylic ester, methacrylonitrile, sodium chloride, citric acid, and potassium dichromate.

10. the expansion layer is provided on the side of the negative electrode sheet facing the separator, and / or the expansion layer is provided on the side of the positive electrode sheet facing the separator, The electrode assembly according to claim 1 , wherein the expansion layer is provided on the separator side.

11. The electrode assembly of claim 1 , wherein the expansion layer comprises one or more of a striped expansion layer, a mesh expansion layer, and a dotted expansion layer.

12. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector side and containing a positive electrode active material, and the thickness H1 of the expansion layer, the thickness H2 of the separator, and the thickness H3 of the positive electrode sheet are expressed as α*H1+(A*H3*ρ ａ ) / (B / ρ ｂ )≦H2 is satisfied, Here, α represents the expansion coefficient in the thickness direction of the expansion layer under the predetermined conditions, A represents the gram capacity of the positive electrode sheet, and ρ ａ represents the density of the positive electrode active material, B represents the gram capacity of sodium metal, and ρ ｂ 10. The electrode assembly of claim 1, wherein σ represents the density of sodium metal.

13. α is 150% to 2000%; and / or A is 90 mAh / g to 150 mAh / g.

14. The thickness H1 of the expansion layer is 0.1 μm to 10 μm, and / or the thickness H2 of the separator is 9 μm to 50 μm; And / or the thickness H3 of the positive electrode sheet is 50 μm to 300 μm, The electrode assembly according to claim 12.

15. The separator satisfies at least one of the following characteristics (I) to (VII): (I) the separator has an air permeability of 120 s / 100 cc to 180 s / 100 cc; (II) the separator has a puncture strength of 0.05 N / μm to 0.5 N / μm; (III) the separator has a breaking elongation of 7% or more; (IV) the separator has a longitudinal tensile strength of 120 MPa or more; (V) the separator has a transverse tensile strength of 10 MPa or more, preferably 20 MPa to 80 MPa; (VI) The areal density of the separator is 3 g / m ２ ~6g / m ２ and (VII) The electrode assembly according to claim 1, wherein the separator comprises a pore structure of a plurality of pores, and the porosity of the separator is 20% to 50%.

16. A battery cell comprising the electrode assembly according to any one of claims 1 to 15.

17. A battery comprising the battery cell of claim 16.

18. 20. A power consuming device comprising the battery of claim 17.

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