Electrode assembly for secondary battery including separator with cutout groove, and secondary battery including the same

Abstract

According to an embodiment of the present disclosure, there is provided an electrode assembly for a secondary battery, the electrode assembly including: a stack including a positive electrode, a negative electrode, and a separator inserted between the positive electrode and the negative electrode, the separator being disposed on the outermost surfaces on both sides of the stack; and at least two pairs of fixing members attached in the stacking direction for fixing between the separators disposed on the outermost surfaces on both sides of the stack, wherein the separator includes at least one pair of cut grooves, and wherein the at least one pair of cut grooves are formed one by one on one surface perpendicular to the protruding direction of the electrode tab and on the other surface disposed in the diagonal direction of the electrode tab.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0067468, filed with the Korean Intellectual Property Office on May 26, 2021, the entire contents of which are incorporated herein by reference.

[0003] The present disclosure relates to an electrode assembly for a secondary battery including a separator with a cut groove and a secondary battery including the electrode assembly. Background Art

[0004] Due to the rapid growth of fossil fuel use, the demand for alternative or clean energy is increasing, and as part of them, the field that is being most actively studied is the field of power generation and energy storage using electrochemistry.

[0005] Currently, secondary batteries are representative examples of electrochemical devices that utilize such electrochemical energy, and the range of use of such electrochemical energy tends to gradually expand.

[0006] In recent years, as mobile devices such as laptop computers, mobile phones, and cameras have been increasingly developed, the demand for secondary batteries as an energy source for mobile devices has also increased sharply. Among such secondary batteries, lithium secondary batteries exhibit high charge / discharge characteristics and life characteristics and are environmentally friendly, and a lot of research has been conducted on them and the lithium secondary batteries are now commercialized and widely used.

[0007] Generally, a secondary battery has the following structure: in this structure, a non-aqueous electrolyte is infiltrated into an electrode assembly including a positive electrode, a negative electrode, and a porous separator.

[0008] At this time, electrodes such as the positive electrode and the negative electrode must be completely separated, but there is a problem that due to the shrinkage of the separator, the protrusion of the electrode active material, and the like, they come into contact with each other and cause a short circuit problem.

[0009] Generally, when the positive electrode active material and the negative electrode active material are short-circuited, the battery voltage drops accompanied by a small amount of heat and the reaction terminates. In the case of a hard short circuit where the positive electrode foil and the negative electrode active material are directly short-circuited, heat generation in a mechanical, electrical, or thermal abuse situation can cause thermal runaway, which can pose a great threat to safety.

[0010] In particular, when deformation of the separator and the electrodes occurs mainly due to shrinkage of the separator at high temperatures, such hard short circuits occur in the order of short circuits, ignition, and the like between the electrodes.

[0011] Figure 1 A conventional electrode assembly is schematically shown, and Figure 2 a phenomenon in which the electrode assembly is deformed at high temperatures to cause a hard short circuit is schematically shown.

[0012] Reference Figure 1 and 2 , the stack 10 includes a positive electrode 11, a negative electrode 12, and a separator 13 inserted between the positive electrode 11 and the negative electrode 12. The separator 13 is also disposed on the outermost surfaces on both sides, and the stack is fixed by at least three pairs of fixing members 14 attached in the stacking direction. The fixing members 14 are used to fix between the separators 13 disposed on the outermost surfaces on both sides of the stack 10.

[0013] When such a stack is subsequently used after being manufactured as a secondary battery, shrinkage of the separator 13 occurs at high temperatures. In particular, as the temperature increases, the shrinkage of the separator 13 accelerates, with a predetermined difference depending on the material. However, separately, the shrinkage in the MD / TD direction is about 10% to 20% at 150 °C, while the shrinkage in the MD / TD direction exceeds 40% at 180 °C. At this time, shrinkage of the separator 13 occurs in the narrow space between the fixing members 14, whereby the positive electrode 11 is deformed together in the stacking direction, such as in the A direction, and a hard short circuit occurs between the positive electrode 11 and the negative electrode 12, which may lead to ignition.

[0014] Therefore, there is an urgent need to develop a technology that can solve such problems and delay or prevent hard short circuits between electrodes due to shrinkage of the separator at high temperatures and thus enhance safety at high temperatures.

[0015] Detailed Description of the Invention

[0016] Technical Problem

[0017] The present disclosure aims to solve the above problems and other technical problems to be solved.

[0018] In particular, an object of the present disclosure is to provide an electrode assembly for a secondary battery that can prevent hard short circuits between electrodes and improve high-temperature safety by forming notch grooves in the separator of the stack and thus guiding the high-temperature shrinkage direction and path, and to provide a secondary battery including the electrode assembly.

[0019] Technical Solution

[0020] According to one aspect of the present disclosure, there is provided an electrode assembly for a secondary battery, the electrode assembly including:

[0021] A stack including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, the separator being disposed on the outermost surfaces on both sides of the stack; and

[0022] At least two pairs of fixing members attached in the stacking direction, the fixing members being configured to fix between the separators disposed on the outermost surfaces on both sides of the stack,

[0023] Wherein the separator includes at least one pair of cut grooves, and

[0024] Wherein the at least one pair of cut grooves are formed one by one on one surface perpendicular to the protruding direction of the electrode tab and on the other surface disposed in the diagonal direction of the electrode tab.

[0025] At this time, at least two pairs of the cut grooves are formed, and the cut grooves may be formed in the diagonal direction and the linear direction of each surface perpendicular to the protruding direction of the electrode tab.

[0026] Furthermore, the cut grooves may be formed at positions that do not interfere with the electrode tab.

[0027] The planar shape of the cut groove may be a slit-like shape, a polygonal shape, a circular shape, or an elliptical shape.

[0028] Meanwhile, the planar shape of the cut groove may be a slit-like shape or a triangular shape.

[0029] The fixing member may include polyimide.

[0030] The fixing member may be configured such that a pair of fixing members are attached to positions facing each other on both sides parallel to the protruding direction of the electrode tab, and at least one other pair of fixing members are attached to positions facing each other on both sides parallel to the protruding direction of the electrode tab at positions spaced apart from the pair of fixing members.

[0031] Meanwhile, the electrode assembly may be a laminated and stacked type electrode assembly or a stacked and folded type electrode assembly.

[0032] According to another aspect of the present disclosure, there is provided a secondary battery, wherein the electrode assembly according to the present disclosure is constructed together with an electrolyte in a secondary battery case. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematically shows a conventional electrode assembly;

[0034] Figure 2is a schematic diagram of a form in which a conventional electrode assembly for a secondary battery is deformed at high temperature, causing the separator to shrink;

[0035] Figure 3 is a schematic diagram of an electrode assembly for a secondary battery according to an embodiment of the present disclosure;

[0036] Figure 4 is a schematic diagram of a form in which Figure 3 the electrode assembly is deformed at high temperature, causing the separator to shrink;

[0037] Figure 5 is a schematic diagram of an electrode assembly for a secondary battery according to another embodiment of the present disclosure;

[0038] Figure 6 is a schematic diagram of a form in which Figure 5 the electrode assembly is deformed at high temperature, causing the separator to shrink; and

[0039] Figure 7 is a schematic diagram showing the planar shape of the cutout groove. DETAILED DESCRIPTION

[0040] For a better understanding of the present disclosure, the present disclosure will be described in more detail hereinafter.

[0041] The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary terms, and based on the principle that the inventors can appropriately define the terms to best describe their own disclosure, the present disclosure should be construed as having meanings and concepts consistent with the technical concept of the present disclosure.

[0042] The technical terms provided herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0043] It should be understood that the terms "comprising", "including", "having", etc. are used herein to specify the presence of the described features, integers, steps, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0044] According to an embodiment of the present disclosure, there is provided an electrode assembly for a secondary battery, the electrode assembly including:

[0045] a stacked body including a positive electrode, a negative electrode, and a separator inserted between the positive electrode and the negative electrode, the separator being disposed on the outermost surfaces on both sides; and

[0046] At least two pairs of fixing members attached in the stacking direction, the fixing members being configured to fix between separators on the outermost surfaces disposed on both sides of the stacked body.

[0047] Wherein the separator includes at least one pair of cut grooves, and

[0048] Wherein the one pair of cut grooves are formed one by one on one surface perpendicular to the protruding direction of the electrode tab and on the other surface disposed in the diagonal direction of the electrode tab.

[0049] Figure 3 FIG. schematically shows an electrode assembly 100 for a secondary battery according to an embodiment of the present disclosure.

[0050] Reference Figure 3 , the electrode assembly 100 according to the present disclosure includes: a stacked body 110 including a positive electrode 111, a negative electrode 112, and a separator 113 inserted between the positive electrode 111 and the negative electrode 112, and the separator 113 is also on the outermost surfaces on both sides; and at least three pairs of fixing members 114 attached in the stacking direction, the fixing members 114 being configured to fix between separators 113 on the outermost surfaces disposed on both sides of the stacked body 110.

[0051] The fixing members 114 are provided to fix the stacked body 110, and the fixing members 114 may include at least two pairs of fixing members to firmly fix the stacked body 110.

[0052] At this time, the fixing members 114 are configured such that a pair of fixing members 114a are attached at positions facing each other on both sides parallel to the protruding direction of the electrode tabs 111a and 112a, and at least one other pair of fixing members 114b and 114c are attached at positions spaced apart from the pair of fixing members 114a at positions facing each other on both sides parallel to the protruding direction of the electrode tabs 111a and 112a.

[0053] As a material constituting such fixing members 114, various materials for batteries can be selected, but in particular, a material having both heat resistance and insulation and thus having no short-circuit problem is preferably used. For example, the material may include polyimide.

[0054] Further, according to the present disclosure, the separator 113 includes a pair of cut grooves 115, and the pair of cut grooves 115 are formed one by one on one surface perpendicular to the protruding direction of the electrode tabs 111a and 112a and on the other surface disposed in the diagonal direction of the electrode tabs 111a and 112a, and the cut grooves 115 can be formed at positions that do not interfere with the electrode tabs 111a and 112a to prevent the electrode tab having the first polarity and the electrode active material layer having the second polarity from contacting each other and causing a short circuit.

[0055] That is, for example, when the cut grooves 115 are formed at positions overlapping with the electrode tabs 111a and 112a, it is possible that the positive electrode tab 111a and the negative electrode active material layer of the negative electrode 112 contact each other at the cut groove 115 portion, thereby causing a short circuit. Therefore, in order to prevent these problems, the electrode tabs 111a and 112a are formed at positions that do not interfere with each other.

[0056] In addition, the pair of cut grooves 115 are particularly formed at positions that are horizontally and vertically symmetric with respect to each other.

[0057] Figure 4 Schematically shows the phenomenon of shrinkage and deformation of the separator when such an electrode assembly 100 is exposed to high temperature.

[0058] Reference Figure 4 , if a pair of cut grooves 115 are formed in the separator 113 as in the present disclosure, then the separator also shrinks when the electrode assembly 100 is exposed to high temperature. However, the previously formed pair of cut grooves 115 cause the separator to tear in the form of connecting the pair of cut grooves 115, whereby no shrinkage occurs between the fixing members 114, and the positive electrode 111 and the separator 113 do not deform in the stacking direction, thereby being able to prevent hard short circuits, reduce the possibility of ignition, and thus improve the safety of the battery.

[0059] That is, the pair of cut grooves 115 cause tearing of the separator 113 while guiding the shrinkage path of the separator 113, thereby preventing deformation of the positive electrode 111 or the negative electrode 112 in the stacking direction.

[0060] At the same time, a pair of cut grooves can be formed as Figures 3 to 4 shown, but at least two pairs can be formed.

[0061] Figure 5 Schematically shows an electrode assembly 200 in which two pairs of cut grooves are formed according to another embodiment of the present disclosure, and Figure 6 schematically shows the phenomenon of shrinkage and deformation of the separator when such an electrode assembly is exposed to high temperature.

[0062] First, reference Figure 5, the electrode assembly 200 includes a stack 210 and three pairs of fixing members 214 attached in the stacking direction, and the fixing members 214 are used for fixing between the separators 213 disposed on the outermost surfaces on both sides of the stack 210, and are similar to those shown in Figure 3 . However, the separator 213 includes two pairs of cut grooves 215 formed in a diagonal direction and a linear direction on each surface perpendicular to the protruding direction of the electrode tabs 211a and 212a, and the two pairs of cut grooves 215 are formed at positions that do not interfere with the electrode tabs 211a and 212a. Further, the two pairs of cut grooves 215 are particularly formed in a shape that is horizontally and vertically symmetric with respect to each other.

[0063] Refer to Figure 6 , when the electrode assembly 200 in which two pairs of cut grooves 215 are formed in this way is also exposed to high temperature, the separator 213 shrinks, and the separator 213 is torn and shrunk in the vertical direction or the diagonal direction through the two pairs of cut grooves 215. Therefore, similar to the electrode assembly 100 in which one pair of cut grooves is formed, no shrinkage occurs between the fixing members 214, and thus, the positive electrode or the negative electrode and the separator 213 do not deform in the stacking direction, thereby being able to prevent hard short circuit, reduce the possibility of ignition and thus improve the safety of the battery.

[0064] If at least two pairs of cut grooves are formed in this way, it is possible to more reliably guide the shrinkage path and tearing of the separator.

[0065] At the same time, the planar shape of the cut groove is not limited and can be formed in various ways. For example, it can be a slit-like shape, a polygonal shape, a circular shape or an oval shape.

[0066] Figure 7 Schematically shows the planar shape of the cut groove 315.

[0067] Refer to Figure 7 , the cut groove 315 forms the planar shape into a triangular shape so that the shrinkage and tearing direction of the separator 313 can be guided along the diagonal direction ( Figure 7 (a)), or forms the planar shape into a slit-like shape so that the shrinkage and tearing direction of the separator 113 can be guided along the direction in which the slit is formed ( Figure 7 (b)), or forms the planar shape into a square shape so that the shrinkage and tearing direction of the separator 113 can be guided along the direction extending from the lower corners on both sides ( Figure 7 (c)), or forms the planar shape into a circular or oval shape so that the shrinkage and tearing direction of the separator 313 can be guided along various directions.

[0068] However, particularly, the planar shape of the cut groove 315 may be a slit-like shape or a triangular shape, such that the shrinking and tearing directions of the separator are invariant and thus the influence on the fixing member can be minimized.

[0069] Furthermore, the size of the cut groove is preferably formed to be a size that does not cause a short circuit between the positive electrode and the negative electrode due to the formation of the cut groove, that is, a size at which the positive electrode active material layer and the negative electrode active material layer are not exposed. Within this range, the size is not limited.

[0070] Meanwhile, as long as the electrode assembly has a shape including a stacked body, the electrode assembly is not limited and may be a stacked type electrode assembly, a laminated and stacked type electrode assembly, or a stacked and folded type electrode assembly. Particularly, it may be a laminated and stacked type electrode assembly or a stacked and folded type electrode assembly.

[0071] Since the detailed manufacturing method and structure of such an electrode assembly are known in the art, a detailed description thereof will be omitted herein.

[0072] Meanwhile, according to another embodiment of the present disclosure, a secondary battery is provided, in which such an electrode assembly is constructed together with an electrolyte in a secondary battery case.

[0073] At this time, the electrolyte may be a lithium salt non-aqueous electrolyte, and the secondary battery may be a lithium secondary battery.

[0074] Since the above structure is well known in the art, a detailed description thereof will be omitted herein.

[0075] Based on the above disclosure, various applications and improvements can be implemented by those of ordinary skill in the art without departing from the spirit and scope of the present disclosure.

[0076] Industrial Applicability

[0077] As described above, the electrode assembly for a secondary battery according to an embodiment of the present disclosure forms a cut groove in the separator and gives the separator artificial defects, which thus guides the shrinking direction and path during the shrinking of the separator at high temperatures, thereby showing the effect of delaying and preventing hard short circuits that may occur between electrodes at high temperatures, and thus, preventing ignition at high temperatures and enhancing the safety of the secondary battery.

Claims

1. An electrode assembly for a secondary battery, comprising: A stacked body, including a positive electrode, a negative electrode, and a separator inserted between the positive electrode and the negative electrode, the separator being disposed on the outermost surfaces on both sides of the stacked body; and At least two pairs of fixing members attached in the stacking direction, the fixing members being configured to fix between the separators disposed on the outermost surfaces on both sides of the stacked body, wherein the separator includes at least one pair of cut grooves, and wherein the at least one pair of cut grooves are formed one by one on one surface perpendicular to the protruding direction of the electrode tab and on the other surface disposed in the diagonal direction of the electrode tab.

2. The electrode assembly for a secondary battery according to claim 1, wherein: At least two pairs of the cut grooves are formed, and the cut grooves are formed in the diagonal direction and the linear direction of each surface perpendicular to the protruding direction of the electrode tab.

3. The electrode assembly for a secondary battery according to claim 1, wherein: The cut grooves are formed at positions that do not interfere with the electrode tab.

4. The electrode assembly for a secondary battery according to claim 1, wherein: The planar shape of the cut groove is a slit-like shape, a polygonal shape, a circular shape, or an elliptical shape.

5. The electrode assembly for a secondary battery according to claim 4, wherein: The planar shape of the cut groove is a slit-like shape or a triangular shape.

6. The electrode assembly for a secondary battery according to claim 1, wherein: The fixing member contains polyimide.

7. The electrode assembly for a secondary battery according to claim 1, wherein: The fixing member is configured such that a pair of fixing members are attached at positions facing each other on both sides parallel to the protruding direction of the electrode tab, and at least one other pair of fixing members are attached at positions facing each other on both sides parallel to the protruding direction of the electrode tab at positions spaced apart from the pair of fixing members.

8. The electrode assembly for a secondary battery according to claim 1, wherein: The electrode assembly is a laminated and stacked type electrode assembly, or a stacked and folded type electrode assembly.

9. A secondary battery, wherein the electrode assembly according to claim 1 is constructed together with an electrolyte in a secondary battery case.

Images