Electrode assembly for secondary battery containing separation membrane formed with notch groove and secondary battery containing the 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 filed on 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, and a secondary battery including the same. [Background technology]

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

[0004] At present, a representative 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, the demand for secondary batteries as an energy source has been increasing rapidly due to technological development and increasing demand for portable devices such as portable computers, mobile phones, and cameras. Among these secondary batteries, much research has been conducted on lithium secondary batteries, which have excellent charge / discharge characteristics and life characteristics and are environmentally friendly, and they have been commercialized and are widely used.

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

[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 and negative active materials 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 foil and negative active material are directly short-circuited, mechanical, electrical, and thermal abuse can occur, generating heat and leading to thermal runaway, which can then pose a major threat to safety.

[0009] In particular, such hard shorts occur primarily due to the contraction of the separator caused by high temperatures, which leads to deformation of the separator and electrodes, which in turn leads 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] 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 on 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 on both sides of the laminate 10.

[0012] When the laminate 10 is used after being manufactured into a secondary battery, the separator 13 shrinks at high temperatures. Specifically, the higher the temperature, the faster the shrinkage of the separator 13 accelerates. Although there is a certain difference depending on the material, the shrinkage in the MD / TD directions is about 10% to 20% at 150°C, and at 180°C, the shrinkage in the MD / TD directions exceeds 40% each. At this time, the shrinkage of the separator 13 occurs in the narrow space between the fixing members 14, and as a result, the positive electrode 11 is deformed in the stacking direction as shown in A, which causes 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 development of technology that can solve these problems, delay or prevent hard shorts between electrodes caused by 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 a high temperature shrinkage direction and path, 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 an 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, 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 separators located on both outermost surfaces of the stack, The separation membrane includes at least a pair of notched grooves, The pair of notches are formed on one surface perpendicular to a protruding direction of the electrode tab and on the other surface diagonally opposite thereto.

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

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

[0019] The planar shape of the notch 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 sides parallel to the protruding direction of the electrode tabs at positions facing each other, and one or more other pairs of fixing members may be attached to both sides 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 together with an electrolyte in a secondary battery case. [Brief description of the drawings]

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

[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 the claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept that corresponds to the technical idea of ​​the present invention, based on the principle that the inventor himself can appropriately define the concept of the term in order to explain the invention in the best possible way.

[0027] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless a different meaning is clearly indicated in the context.

[0028] In this specification, terms such as "comprise", "comprise", or "have" are intended to specify the presence of embodied features, numerals, 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, numerals, steps, components, or combinations thereof.

[0029] According to one embodiment of the present invention, An electrode assembly for a secondary battery, comprising: 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 separators located on both outermost surfaces of the stack, The separation membrane includes at least a pair of notched grooves, The pair of notched grooves are formed on one surface perpendicular to a 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 laminate 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 for fixing between the separators 113 located on the outermost surfaces of both sides of the laminate 110.

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

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

[0034] The material for such fixing member 114 can be selected from various materials used in batteries, but in particular, a material that has heat resistance and insulating properties and does not cause short circuits is preferable, and can include, for example, polyimide.

[0035] In addition, according to the present invention, the separation membrane 113 includes a pair of notches 115 formed on one surface perpendicular to the protruding direction of the electrode tabs 111a, 112a and the other surface diagonally opposite thereto, and the notches 115 may be formed at positions not subject to interference from the electrode tabs 111a, 112a so that the electrode tabs having a first polarity and the electrode active material layer having a second polarity do not come into contact with each other and cause a short circuit.

[0036] That is, for example, if the notch groove 115 is formed at a position overlapping with the electrode tabs 111a, 112b, there is a possibility that the positive electrode tab 111a and the negative electrode active material layer of the negative electrode 112 will come into contact at the notch groove 115 portion, causing a short circuit. Therefore, in order to prevent such a problem, the notch groove 115 is formed at a position where it will not be interfered with by the tabs 111a, 112a.

[0037] Specifically, the pair of cutout grooves 115 are formed at positions that are symmetrical to each other in the left-right and up-down directions.

[0038] FIG. 4 is a schematic diagram showing a phenomenon in which the separator shrinks and deforms when the electrode assembly 100 is exposed to high temperatures.

[0039] Referring to FIG. 4, in the case where a pair of notch grooves 115 is formed in the separator 113 as in the present invention, when the electrode assembly 100 is exposed to high temperatures, the separator shrinks in the same manner. However, the separator breaks in a manner that connects the pair of notch grooves 115 due to the pair of notch grooves 115 that have already been formed. As a result, no shrinkage occurs between the fixing member 114, and the positive electrode 111 and the separator 114 are not deformed in the stacking direction, which prevents a hard short and reduces the possibility of fire, thereby improving the safety of the battery.

[0040] That is, the pair of notched grooves 115 guide the path along which the separator 113 contracts, 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, although a pair of notch grooves can be formed as shown in Figs. 3 and 4, two or more pairs of notch grooves can also be formed.

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

[0043] 5, the electrode assembly 200 includes three pairs of fixing members 214 attached in the stacking direction for fixing between the laminate 210 and the separation membranes 213 located on the outermost surfaces of both sides of the laminate 210. The separation membrane 213 includes two pairs of notches 215 formed in a diagonal direction and in a straight line direction 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 are not interfered with by the electrode tabs 211a and 212a. In detail, the two pairs of notches 215 are formed in a shape that is symmetrical to each other in the left-right and top-bottom directions.

[0044] 6, when the electrode assembly 200 having the two pairs of notch grooves 215 formed therein is exposed to high temperatures, the separator 213 shrinks and breaks and shrinks in the vertical or diagonal direction due to the two pairs of notch grooves 215. Therefore, as with the electrode assembly 100 having a pair of notch grooves, no shrinkage occurs between the fixing members 214 and the positive or negative electrode and the separator 214 are not deformed in the stacking direction, which prevents hard shorts and reduces 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 more reliably guided.

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

[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 a plan view to induce the shrinkage and tearing direction of the separation membrane 313 in a diagonal direction (a), or may be formed in a slit shape in a plan view to induce the shrinkage and tearing direction of the separation membrane 313 in the direction in which the slit is formed, i.e., in a straight line (b), or may be formed in a rectangular shape in a plan view to induce the shrinkage and tearing direction of the separation membrane 313 in the direction extending from the lower edges on both sides (c), or may be formed in a circular or elliptical shape in a plan view to induce the shrinkage and tearing direction of the separation membrane 313 in multiple directions.

[0049] However, in detail, the planar shape of the notch 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] In addition, the size of such a notch groove is preferably a size that does not cause a short circuit between the positive electrode and the negative electrode due to the formation of the notch groove, i.e., a size that does not expose the positive electrode active material layer and the negative electrode active material layer, 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, so a 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 the present invention can be applied in various ways and modified within the scope of the present invention 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, thereby delaying and preventing hard shorts between electrodes that may occur at high temperatures, thereby preventing fire 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 both outermost surfaces; The separation membrane includes at least one pair of notches that guide a contraction direction and path when the separation membrane is contracted, The pair of notches are formed on one surface perpendicular to a protruding direction of the electrode tab and on the other surface diagonally opposite thereto, the pair of notches are formed to have a size such that the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode are not exposed.

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

3. 3. The electrode assembly for a secondary battery according to claim 1, wherein the notch 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 cutout groove has a planar shape of a slit, a polygon, a circle, or an ellipse.

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

6. The laminate further includes two or more pairs of fixing members attached in the stacking direction for fixing the separation membranes located on both outermost surfaces of the laminate, The electrode assembly for a secondary battery according to claim 1 , wherein the fixing member comprises 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 a 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. 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-folding type electrode assembly.

9. 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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