Electrode assembly for secondary battery including separator with notched groove and secondary battery including same

Abstract

To provide an electrode assembly for a secondary battery capable of preventing a hard short circuit between electrodes by introducing a high-temperature contraction direction and a path by forming a notch groove to a separation membrane of a lamination body and improving a high-temperature safety, and provide a secondary battery including the same.SOLUTION: The present invention provides an electrode assembly for a secondary battery and a secondary battery including the same. The electrode assembly for the secondary battery, comprises: a lamination body including a positive electrode 111, a negative electrode 112, and a separation membrane 113 interposed between the positive electrode and the negative electrode, in which the separation membranes are positioned on both outermost surfaces; and two or more pairs of fixing members 114a, 114b, and 114c adhering in a lamination direction for fixing the separation membranes positioned on both outermost surfaces of the lamination body. The separation membrane contains at least a pair of notch grooves 115. The pair of notch grooves are formed on one surface vertical to a projection direction of electrode tubs 111a and 112a and the other surface positioned in their diagonal direction one by one.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0067468 dated May 26, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly for a secondary battery including a separator having a notched groove formed therein, and a secondary battery including the same. [Background technology]

[0003] The rapid increase in fossil fuel use has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields as part of this is the field of electrochemical power generation and storage.

[0004] Currently, a typical example of an electrochemical element that uses such electrochemical energy is a secondary battery, and the range of its use is tending to expand more and more.

[0005] Recently, technological development and increased demand for portable devices such as portable computers, mobile phones, and cameras have led to a rapid increase in demand for secondary batteries as energy sources. Among these secondary batteries, much research has been conducted on environmentally friendly lithium secondary batteries, which exhibit excellent charge / discharge characteristics and lifespan characteristics, and they have been commercialized and widely used.

[0006] Generally, a lithium secondary battery is manufactured by impregnating a lithium non-aqueous electrolyte into an electrode assembly consisting of a positive electrode, a negative electrode, and a porous separator.

[0007] In this case, the electrodes such as the positive electrode and the negative electrode must be completely separated, but there is a problem that they may come into contact with each other due to shrinkage of the separator or protrusion of the electrode active material, resulting in a short circuit.

[0008] Generally, when the positive electrode active material and negative electrode active material short circuit, the cell voltage drops along with a small amount of heat and the reaction ends. However, in the case of a hard short, where the positive electrode foil and negative electrode active material are directly shorted, mechanical, electrical, and thermal abuse occurs, which can generate heat and lead to thermal runaway, posing a serious threat to safety.

[0009] In particular, such hard shorts occur primarily due to the shrinkage of the separator caused by high temperatures, which causes deformation of the separator and electrodes, leading to short circuits between electrodes and fire.

[0010] FIG. 1 is a schematic diagram of a conventional electrode assembly, and FIG. 2 is a schematic diagram of a phenomenon in which a hard short occurs due to deformation of the electrode assembly at high temperatures.

[0011] Referring to FIGS. 1 and 2, a laminate 10 including a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, with the separator 13 also located on the outermost surfaces of both sides, is fixed by three or more pairs of fixing members 14 attached in the stacking direction to fix the separators 13 located on the outermost surfaces of both sides of the laminate 10.

[0012] When this laminate 10 is subsequently manufactured into a secondary battery and used, the separator 13 shrinks at high temperatures. Specifically, the higher the temperature, the faster the separator 13 shrinks. Although this shrinkage varies depending on the material, it is approximately 10% to 20% in both MD and TD directions at 150°C, and exceeds 40% in both MD and TD directions at 180°C. The shrinkage of the separator 13 occurs in the narrow space between the fixing members 14, which causes the positive electrode 11 to deform in the stacking direction as shown in A, resulting in a hard short circuit between the positive electrode 11 and the negative electrode 12, which can lead to fire.

[0013] Therefore, there is a pressing need for technological development that can solve this problem, delay or prevent hard shorts between electrodes due to separator shrinkage at high temperatures, and enhance safety at high temperatures. Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention aims to solve the above-mentioned problems of the prior art and the technical problems that have been required in the past.

[0015] Specifically, an object of the present invention is to provide an electrode assembly for a secondary battery, which can prevent hard shorts between electrodes and improve high-temperature safety by forming a notch groove in a separator of a laminate to guide the direction and path of high-temperature shrinkage, and a secondary battery including the same. [Means for solving the problem]

[0016] To achieve this object, an electrode assembly for a secondary battery according to one embodiment of the present invention comprises: a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, with the separator located on the outermost surfaces of both sides; and two or more pairs of fixing members attached in the stacking direction for fixing the separators located on both outermost surfaces of the stack, The separation membrane includes at least one pair of notched grooves, The pair of notched grooves are formed on one surface perpendicular to the protruding direction of the electrode tab and on the other surface diagonally opposite thereto.

[0017] At this time, two or more pairs of notched grooves may be formed, and the notched grooves may be formed in diagonal and linear directions on each surface perpendicular to the protruding direction of the electrode tabs.

[0018] The notched groove may be formed at a position where it is not interfered with by the electrode tab.

[0019] The planar shape of the notched groove may be slit-shaped, polygonal, circular, or elliptical, and more particularly, may be slit-shaped or triangular.

[0020] Meanwhile, the fixing member may include polyimide.

[0021] The fixing members may include a pair of fixing members attached to both side surfaces parallel to the protruding direction of the electrode tabs at positions facing each other, and one or more other pairs of fixing members attached to both side surfaces parallel to the protruding direction of the electrode tabs at positions spaced apart from the pair of fixing members at positions facing each other.

[0022] Meanwhile, the electrode assembly may be a lamination-and-stack type electrode assembly or a stack-and-fold type electrode assembly.

[0023] Furthermore, according to one embodiment of the present invention, there is provided a secondary battery in which the electrode assembly according to the present invention is housed in a secondary battery case together with an electrolyte. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram of a conventional electrode assembly for a secondary battery. [Figure 2] 1 is a schematic view showing a state in which a separator shrinks due to deformation of an electrode assembly for a conventional secondary battery at high temperature. [Figure 3] 1 is a schematic diagram of an electrode assembly of a secondary battery according to an embodiment of the present invention; [Figure 4] 4 is a schematic view showing a state in which the separator is shrunk due to deformation of the electrode assembly of FIG. 3 at high temperature. [Figure 5] 4 is a schematic view of an electrode assembly of a secondary battery according to another embodiment of the present invention; [Figure 6] 6 is a schematic view showing a state in which the separator is shrunk due to deformation of the electrode assembly of FIG. 5 at high temperature. [Figure 7] FIG. 4 is a schematic diagram showing the planar shape of a notched groove. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will now be described in more detail to aid in understanding the invention.

[0026] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best explain the invention.

[0027] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0028] In this specification, the terms "comprises," "includes," "comprises," or "has" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0029] According to one embodiment of the present invention, An electrode assembly for a secondary battery, a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, with the separator located on the outermost surfaces of both sides; and two or more pairs of fixing members attached in the stacking direction for fixing the separators located on both outermost surfaces of the stack, The separation membrane includes at least one pair of notched grooves, The pair of notched grooves may be formed on one surface perpendicular to the protruding direction of the electrode tab and on the other surface diagonally opposite thereto, thereby providing an electrode assembly for a secondary battery.

[0030] FIG. 3 is a schematic diagram illustrating an electrode assembly 100 for a secondary battery according to one embodiment of the present invention.

[0031] Referring to FIG. 3, the electrode assembly 100 according to the present invention includes a stack 110 including a positive electrode 111, a negative electrode 112, and a separator 113 disposed between the positive electrode 111 and the negative electrode 112 and located on the outermost surfaces of both sides, and three pairs of fixing members 114 attached in the stacking direction to fix the separators 113 located on the outermost surfaces of both sides of the stack 110.

[0032] The fixing members 114 are provided to fix the stack 110, and may include at least two pairs of fixing members to firmly fix the stack 110.

[0033] At this time, the fixing members 114 are attached in positions facing each other on both sides parallel to the protruding direction of the electrode tabs 111a and 112a, with a pair of fixing members 114a, and another pair of fixing members 114b and 114c attached in positions facing each other on both sides parallel to the protruding direction of the electrode tabs 111a and 112a, spaced apart from the pair of fixing members 114a.

[0034] The material for the fixing member 114 can be selected from a variety of materials used in batteries, but in particular, a material that is heat resistant and insulating and does not cause short circuits is preferred, and may include, for example, polyimide.

[0035] Furthermore, according to the present invention, the separator 113 includes a pair of notches 115 formed on one surface perpendicular to the protruding direction of the electrode tabs 111 a and 112 a and the other surface diagonally opposite the one surface. The notches 115 may be formed at positions that are not subject to interference from the electrode tabs 111 a and 112 a so as to prevent the electrode tabs having a first polarity from contacting the electrode active material layer having a second polarity and causing a short circuit.

[0036] That is, for example, if the notch groove 115 is formed at a position overlapping with the electrode tabs 111a and 112b, the positive electrode tab 111a and the negative electrode active material layer of the negative electrode 112 may come into contact at the notch groove 115, causing a short circuit. To prevent such a problem, the notch groove 115 is formed at a position where it is not interfered with by the tabs 111a and 112a.

[0037] In addition, the pair of notched grooves 115 are specifically formed at positions that are symmetrical to each other in the left-right and top-bottom directions.

[0038] FIG. 4 schematically illustrates the phenomenon in which the separator shrinks and deforms when the electrode assembly 100 is exposed to high temperatures.

[0039] Referring to FIG. 4, when a pair of notch grooves 115 is formed in the separator 113 as in the present invention, if the electrode assembly 100 is exposed to high temperatures, the separator will shrink in the same manner. However, the pair of notch grooves 115 that were already formed will cause the separator to tear in a manner that connects the pair of notch grooves 115. As a result, no shrinkage will occur between the fixing member 114, and the positive electrode 111 and the separator 114 will not be deformed in the stacking direction. This prevents hard shorts, reduces the possibility of fire, and improves battery safety.

[0040] That is, the pair of notched grooves 115 guides the path of the separator 113 contraction, causing the separator 113 to break, thereby preventing deformation of the positive electrode 111 or the negative electrode 112 in the stacking direction.

[0041] Meanwhile, as shown in FIGS. 3 and 4, a pair of notched grooves can be formed, but two or more pairs can also be formed.

[0042] FIG. 5 is a schematic illustration of an electrode assembly 200 having two pairs of notched grooves according to another embodiment of the present invention, and FIG. 6 is a schematic illustration of the phenomenon in which the separator shrinks and deforms when the electrode assembly is exposed to high temperatures.

[0043] 5, the electrode assembly 200, as shown in FIG. 3, includes three pairs of fixing members 214 attached in the stacking direction to fix the laminate 210 and the separators 213 located on the outermost surfaces of both sides of the laminate 210. The separator 213 includes two pairs of notches 215 formed in diagonal and linear directions on each surface perpendicular to the protruding direction of the electrode tabs 211a and 212a, and both pairs of notches 215 are formed at positions that do not interfere with the electrode tabs 211a and 212a. In particular, the two pairs of notches 215 are formed in a shape that is symmetrical with each other left and right and up and down.

[0044] 6, when the electrode assembly 200 having two pairs of notch grooves 215 formed therein is exposed to high temperatures, the separator 213 contracts, and the separator 213 is torn and contracted in the vertical or diagonal direction by the two pairs of notch grooves 215. Therefore, similar to the electrode assembly 100 having a pair of notch grooves formed therein, no contraction occurs between the fixing members 214, and the positive or negative electrode and the separator 214 are not deformed in the stacking direction, preventing hard shorts and reducing the possibility of fire, thereby improving battery safety.

[0045] By forming two or more pairs of notched grooves in this manner, the path of contraction and tearing of the separation membrane can be guided more reliably.

[0046] Meanwhile, the planar shape of the notch groove is not limited and may be formed in various shapes, for example, a slit shape, a polygonal shape, a circle shape, or an oval shape.

[0047] FIG. 7 shows a schematic plan view of such a notched groove 315.

[0048] Referring to FIG. 7, the notch groove 315 may be formed in a triangular shape in plan view to induce the separation membrane 313 to contract and tear in a diagonal direction (a), or may be formed in a slit shape in plan view to induce the separation membrane 313 to contract and tear in the direction of the slit, i.e., a straight line (b), or may be formed in a rectangular shape in plan view to induce the separation membrane 313 to contract and tear in the direction extending from the lower edges on both sides (c), or may be formed in a circular or elliptical shape in plan view to induce the separation membrane 313 to contract and tear in multiple directions.

[0049] However, in detail, the planar shape of the notched groove 315 may be a slit or a triangle so that the direction of contraction and tearing of the separation membrane is constant and the influence on the fixing member is minimized.

[0050] Furthermore, the size of such a notch groove is preferably such that the formation of the notch groove does not cause a short circuit between the positive electrode and the negative electrode, i.e., such that the positive electrode active material layer and the negative electrode active material layer are not exposed, and the size is not limited as long as it is within this range.

[0051] Meanwhile, the electrode assembly is not limited as long as it has a form including a laminate, and may be a stack-type electrode assembly, a lamination-and-stack-type electrode assembly, or a stack-and-folding-type electrode assembly, and more particularly, may be a lamination-and-stack-type electrode assembly or a stack-and-folding-type electrode assembly.

[0052] The detailed manufacturing method and structure of such an electrode assembly are well known in the art, and therefore, detailed description thereof will be omitted in this specification.

[0053] Meanwhile, according to another embodiment of the present invention, there is provided a secondary battery in which the electrode assembly is housed in a secondary battery case together with an electrolyte.

[0054] In this case, the electrolyte may be a lithium salt non-aqueous electrolyte, and the secondary battery may be a lithium secondary battery.

[0055] The above-mentioned configuration is well known in the art, and therefore a detailed description thereof will be omitted in this specification.

[0056] Those skilled in the art will appreciate that various applications and modifications within the scope of the present invention can be made based on the above content. [Industrial Applicability]

[0057] As described above, the electrode assembly for a secondary battery according to one embodiment of the present invention has an artificial defect in the separator by forming a notch groove in the separator, thereby guiding the direction and path of contraction when the separator contracts at high temperatures. This delays and prevents hard shorts between electrodes that may occur at high temperatures, thereby preventing fires at high temperatures and enhancing the safety of the secondary battery.

Claims

1. a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, the separator being located on the outermost surfaces of both sides; and two or more pairs of fixing members attached in a stacking direction for fixing the separation membranes located on both outermost surfaces of the stack, The separation membrane includes at least one pair of notched grooves that guide the contraction direction and tear path when contracted, The electrode assembly for a secondary battery, wherein the pair of notched grooves are formed on one surface perpendicular to the protruding direction of the electrode tab and on the other surface diagonally opposite the one surface.

2. 2. The electrode assembly for a secondary battery according to claim 1, wherein two or more pairs of the notched grooves are formed, and the notched grooves are formed in diagonal and linear directions on each surface perpendicular to the protruding direction of the electrode tab.

3. 3. The electrode assembly for a secondary battery according to claim 1, wherein the notched groove is formed at a position where it is not interfered with by the electrode tab.

4. The electrode assembly for a secondary battery according to claim 1 , wherein the planar shape of the notched groove is a slit shape, a polygonal shape, a circle shape, or an ellipse shape.

5. 5. The electrode assembly for a secondary battery according to claim 4, wherein the planar shape of the notched groove is a slit shape or a triangle shape.

6. An electrode assembly for a secondary battery described in any one of claims 1 to 5, wherein the fixing member includes polyimide.

7. 7. The electrode assembly for a secondary battery according to claim 6, wherein the fixing members include a pair of fixing members attached to both side surfaces parallel to the protruding direction of the electrode tab at positions facing each other, and one or more other pairs of fixing members attached to both side surfaces parallel to the protruding direction of the electrode tab at positions spaced apart from the pair of fixing members at positions facing each other.

8. An electrode assembly for a secondary battery as described in claim 1, wherein the pair of cutout grooves are formed to a size that does not expose the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode.

9. When the electrode assembly is exposed to high temperatures, the two or more pairs of notched grooves guide the shrinkage direction and the tear path in the diagonal direction, the linear direction, or multiple directions. The electrode assembly for a secondary battery according to claim 2 .

10. The electrode assembly for a secondary battery according to claim 1 , wherein the electrode assembly for a secondary battery is a lamination-and-stack type electrode assembly or a stack-and-fold type electrode assembly.

11. A secondary battery comprising the electrode assembly for a secondary battery according to claim 1 housed in a secondary battery case together with an electrolyte.

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