Secondary battery

Abstract

The present invention relates to a secondary battery comprising: an electrode assembly; an accommodating portion accommodating the electrode assembly; and a pouch-type outer material having a sealing portion formed to surround at least a portion of the accommodating portion to seal the accommodating portion, in which the sealing portion includes: a first fold formed by folding an outer end portion of the sealing portion toward the accommodating portion along a first fold line, the first fold line is spaced apart from the outside end of the sealing portion toward the receiving portion by a first distance; and a second folding portion formed by folding the first folding portion toward the accommodating portion along a second folding line spaced apart from the first folding line toward the accommodating portion by a second distance, and when a specific line spaced apart from an outer side end portion of the sealing portion toward the accommodating portion by a specific distance is referred to as a closing line. The encapsulation portion includes a sealing portion formed by melt sealing from an outer end portion of the sealing portion to a closing line, and when a distance from the outer end portion of the sealing portion to the accommodating portion is referred to as a width of the sealing portion, a distance from the closing line to the accommodating portion may be 45% to 55% of a width of the encapsulation portion.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims the priority of Korean Patent Application No. 10 - 2022 - 0176561, filed on December 16, 2022, and Korean Patent Application No. 10 - 2023 - 0182678, filed on December 15, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The present disclosure relates to a secondary battery. Background Art

[0005] Generally, a secondary battery refers to a rechargeable battery different from a non - rechargeable primary battery, and is widely used in electronic devices (e.g., mobile phones, laptop computers, and camcorders), electric vehicles, etc. In particular, lithium secondary batteries have a larger capacity and higher energy density than nickel - cadmium batteries or nickel - metal hydride batteries, so their utilization rate is showing a rapid growth trend.

[0006] According to the shape of the battery case, secondary batteries can be classified into cylindrical or square batteries in which the electrode assembly is embedded in a cylindrical or square metal can, pouch - type batteries in which the electrode assembly is embedded in a pouch - type case made of a laminate, etc.

[0007] Figure 1 is a view showing an example of a pouch - type secondary battery. The pouch - type secondary battery 1 (pouch - type cell) includes an electrode assembly 2 in which electrodes and a separator are alternately stacked, and a pouch - type outer case 20 that houses the electrode assembly 2. Electrode terminals 15 can be respectively connected to the electrodes of the electrode assembly 2. The electrode terminals 15 can be welded to each other in a predetermined area and then connected to an electrode lead 17 by welding. The outer case 20 includes a receiving portion 21 to house the electrode assembly 2. The receiving portion 21 of the outer case 20 can be provided in one or two recess - shaped portions. Figure 1 Shows the receiving portion 21 provided in two recess - shaped portions. A sealing portion 23 (step) is formed by sealing around the outer periphery of the receiving portion 21. In order to reduce the space occupied by the secondary battery to improve the volumetric energy density of the secondary battery, the sealing portion 23 of the secondary battery can be folded toward the receiving portion 21. This folding can be applied once or more than twice.

[0008] Recently, in order to improve the safety of a pouch-type secondary battery to enhance the quality of the pouch-type secondary battery, it is necessary to greatly increase the insulation resistance of the pouch-type secondary battery (for example, increasing the resistance from the conventional level of 1 MΩ to the level of 100 MΩ). However, the folding of the sealing part 23 may cause an insulation resistance defect, resulting in a decrease in the insulation resistance. When the sealing part 23 is folded multiple times, this problem may become more significant. Summary of the Invention

[0009] Technical Problem

[0010] An object of the present invention is to provide a secondary battery having a folding structure in which, even when the sealing part is folded multiple times, a decrease in the insulation resistance does not occur, or the decrease in the insulation resistance is minimized.

[0011] Technical Solution

[0012] In one embodiment, a secondary battery may include: an electrode assembly; and a pouch-type housing including a receiving portion and a sealing portion, the receiving portion receiving the electrode assembly, the sealing portion being configured to be formed to surround at least a part of the receiving portion to seal the receiving portion, wherein the sealing portion includes: a first folding portion configured such that an outer end portion of the sealing portion folds toward the receiving portion along a first folding line, the first folding line being spaced apart from the outer end portion of the sealing portion toward the receiving portion by a first distance; and a second folding portion configured such that the first folding portion folds toward the receiving portion along a second folding line, the second folding line being spaced apart from the first folding line toward the receiving portion by a second distance, wherein, when a predetermined line spaced a predetermined distance from the outer end portion of the sealing portion toward the receiving portion is referred to as a closing line, the sealing portion includes a closed portion formed by closing, by melting, a portion from the outer end portion of the sealing portion to the closing line, and wherein, when a distance from the outer end portion of the sealing portion to the receiving portion is referred to as the width of the sealing portion, a distance from the closing line to the receiving portion is 45% to 55% of the width of the sealing portion.

[0013] In another embodiment, a distance from the outer end portion of the sealing portion to the first folding line may be 60% to 80% of a distance from the outer end portion of the sealing portion to the closing line.

[0014] In yet another embodiment, a distance from the receiving portion to the second folding line may be 18% to 34% of a distance from the closing line to the receiving portion.

[0015] In yet another embodiment, the closing line may be located between the first folding line and the second folding line.

[0016] In yet another embodiment, a secondary battery includes: an electrode assembly; and a pouch-type case including a receiving portion and a sealing portion, the receiving portion receiving the electrode assembly, and the sealing portion being configured to surround at least a part of the receiving portion to seal the receiving portion. The sealing portion includes: a first folding portion configured such that an outer end portion of the sealing portion is folded toward the receiving portion along a first folding line, the first folding line being spaced apart from the outer end portion of the sealing portion by a first distance toward the receiving portion and being parallel to the outer end portion of the sealing portion; and a second folding portion configured such that the first folding portion is folded toward the receiving portion along a second folding line, the second folding line being spaced apart from the first folding line by a second distance toward the receiving portion and being parallel to the first folding line. When a distance from the outer end portion of the sealing portion to the receiving portion is referred to as a width of the sealing portion, the first distance is 34.65% to 42.35% of the width of the sealing portion, and the second distance is 43.65% to 53.35% of the width of the sealing portion.

[0017] In yet another embodiment, when a predetermined line that is spaced apart from an outer end portion of the sealing portion by a predetermined distance toward the receiving portion and is parallel to the outer end portion of the sealing portion is referred to as a closing line, in the sealing portion, a portion from the outer end portion of the sealing portion to the closing line may be closed by melting. The closing line may be located between the first folding line and the second folding line, and a distance from the second folding line to the closing line may be 20% or more of the width of the sealing portion.

[0018] In yet another embodiment, when a predetermined line that is spaced apart from an outer end portion of the sealing portion by a predetermined distance toward the receiving portion and is parallel to the outer end portion of the sealing portion is referred to as a closing line, in the sealing portion, a portion from the outer end portion of the sealing portion to the closing line may be closed by melting. The closing line may be located between the first folding line and the second folding line, and a distance from the second folding line to the closing line may be 40% or more of a distance from the outer end portion of the sealing portion to the closing line.

[0019] In yet another embodiment, when a predetermined line that is spaced apart from an outer end portion of the sealing portion by a predetermined distance toward the receiving portion and is parallel to the outer end portion of the sealing portion is referred to as a closing line, in the sealing portion, a portion from the outer end portion of the sealing portion to the closing line may be closed by melting, and a portion from the closing line to the receiving portion may not be melted. The closing line may be located between the first folding line and the second folding line, and a distance from the closing line to the receiving portion may be 40% or more of the width of the sealing portion.

[0020] In yet another embodiment, a secondary battery may include: an electrode assembly; and a pouch-type casing including a receiving portion and a sealing portion, the receiving portion receiving the electrode assembly, and the sealing portion being configured to form around at least a portion of the receiving portion to seal the receiving portion, wherein the sealing portion includes: a first folding portion configured such that an outer end portion of the sealing portion folds toward the receiving portion along a first folding line, the first folding line being spaced apart from the outer end portion of the sealing portion toward the receiving portion by a first distance and being configured to be parallel to the outer end portion of the sealing portion; and a second folding portion configured such that the first folding portion folds toward the receiving portion along a second folding line, the second folding line being spaced apart from the first folding line toward the receiving portion by a second distance and being configured to be parallel to the first folding line, wherein, when a predetermined line that is spaced apart from the outer end portion of the sealing portion toward the receiving portion by a predetermined distance and is configured to be parallel to the outer end portion of the sealing portion is referred to as a closing line, in the sealing portion, a portion from the outer end portion of the sealing portion to the closing line is closed by melting, and wherein a distance from the second folding line to the closing line is 40% or more of a distance from the outer end portion of the sealing portion to the closing line.

[0021] In yet another embodiment, the closing line may be located between the first folding line and the second folding line.

[0022] Advantageous Effects

[0023] According to the present invention, through optimization of the sealing range or folding position, even when the sealing portion has been folded multiple times, a decrease in insulation resistance does not occur, or a decrease in insulation resistance can be minimized.

[0024] In addition, according to the present invention, an unfused portion (dielectric seal gap) of the sealing portion can be sufficiently ensured to improve the insulation resistance defect rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a view showing an example of a pouch-type secondary battery.

[0026] Figure 2 is a perspective view of a secondary battery according to an embodiment of the present invention.

[0027] Figures 3 to 6 is a view sequentially showing the operations of manufacturing Figure 2 the secondary battery therein. DETAILED DESCRIPTION

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily implement the present invention. However, the present invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein.

[0029] To clearly describe the present invention, descriptions of parts irrelevant to the description or detailed descriptions of related well-known technologies that may unnecessarily obscure the subject matter of the present invention will be excluded. Throughout the specification, the same reference numerals denote the same elements.

[0030] Furthermore, terms or words used in this specification and claims should not be construed restrictively as ordinary meanings or dictionary-based meanings, but should be construed as meanings and concepts that conform to the scope of the present invention based on the principle that the inventor can appropriately define the concepts of the terms so as to best describe and illustrate his invention.

[0031] Figure 2 is a perspective view showing a secondary battery according to an embodiment of the present invention. Figures 3 to 6 is a view sequentially showing the operation of the secondary battery in Figure 2 . As shown in Figure 3 , the secondary battery according to this embodiment may include an electrode assembly 110 and a housing 120. Figure 3 is a perspective view showing the state before the sealing portions 140 (141 and 142) of the secondary battery in Figure 2 are folded.

[0032] The electrode assembly 110 may be provided by alternately laminating electrodes and separators (see reference numeral 2 in Figure 1 ). The electrodes may include a positive electrode and a negative electrode. The electrode assembly 110 may include electrode terminals connected to the electrodes (see Figure 1 ). The electrode terminals may be provided separately, or may be provided as part of a current collector constituting the electrode.

[0033] The housing 120 may be a pouch-type housing 120 formed by molding a laminate to accommodate the electrode assembly 110. The pouch-type housing 120 may include a receiving portion 130 to accommodate the electrode assembly 110. The pouch-type housing 120 may be configured such that two housings arranged to face each other are joined and sealed to each other in a state of accommodating the electrode assembly 110. Here, the edges of the two housings may be completely sealed to each other. The sealing portion 140 may be formed through such sealing. Alternatively, the pouch-type housing may be provided by folding a single housing (see Figure 1 ). Here, the edges of the remaining portion except the folded portion of the single housing may be sealed. Figure 3 etc. show the housing 120 in which the receiving portion 130 is provided with a recessed portion.

[0034] The pouch-type casing 120 can be manufactured from a laminate including a metal layer made of, for example, aluminum, a first resin layer provided on the inner surface of the metal layer, and a second resin layer provided on the outer surface of the metal layer. The first resin layer can be a layer made of polypropylene (PP). The first resin layer requires high insulation properties and corrosion resistance, and the first resin layer can be made of other resins that meet this requirement. The second resin layer can be a layer made of polyethylene terephthalate (PET). The second resin layer needs to protect the secondary battery and also electrically insulate the secondary battery, and the second resin layer can be made of other resins that meet this requirement.

[0035] As Figure 3 and Figure 4 shown, the sealing portion 140 can include a first folding portion 141 (see Figure 2 and Figure 5 ), which is arranged such that the outer end portion 140a of the sealing portion 140 is folded toward the accommodating portion 130 along a first folding line F1 that is spaced apart from the outer end portion 140a of the sealing portion 140 by a first distance L1 toward the accommodating portion 130. The first folding line F1 can be arranged parallel to the outer end portion 140a of the sealing portion 140. For reference, Figure 4 is a cross-sectional view of the secondary battery taken along Figure 3 the center line A-A. Figure 5 is a cross-sectional view of the secondary battery showing the outer end portion of the sealing portion of the secondary battery in Figure 4 folded along the first folding line to provide the first folding portion. For ease of illustration, the electrode assembly is not shown in Figure 4 and Figure 5 .

[0036] The sealing portion 140 can include a second folding portion 142 (see Figure 2 and Figure 6 ), which is arranged such that the first folding portion 141 is folded toward the accommodating portion 130 along a second folding line F2 that is spaced apart from the first folding line F1 by a second distance L2 toward the accommodating portion 130. The second folding line F2 can be arranged parallel to the first folding line F1. For reference, Figure 6 is a cross-sectional view of the secondary battery showing the first folding portion of the sealing portion of the secondary battery in Figure 5 folded along the second folding line to provide the second folding portion. For ease of illustration, the electrode assembly is not shown in Figure 6 .

[0037] As Figure 4As shown, when a predetermined line spaced a predetermined distance L3 from the outer side end 140a of the sealing portion 140 toward the accommodating portion 130 is referred to as a closed line S, the sealing portion 140 may include a closed portion 151 in which a portion from the outer side end 140a of the sealing portion 140 to the closed line S is closed by melting. The closed line S may be provided parallel to the outer side end 140a of the sealing portion 140. The closed line S may be located between the first folding line F1 and the second folding line F2. The melting may be thermal melting.

[0038] When the distance from the outer end 140 a of the sealing portion 140 to the accommodating portion 130 is referred to as the width L of the sealing portion 140 , W When the distance L4 from the closed line S to the receiving portion 130 is equal to the width L of the sealing portion 140, W Therefore, the distance L3 from the outer end 140a of the sealing portion 140 to the closed line S may be the width L of the sealing portion 140. W For example, if the distance L4 is 45% to 55% of the width LW of the sealing portion 140, the distance L3 may be 45% to 55% of the width LW of the sealing portion 140. W The sum of the distance L4 and the distance L3 may be equal to the width L of the sealing portion 140. W .

[0039] For example, the width L of the sealing portion 140 is W The width L3 of the sealing portion 140 may be 10 mm, and the distance L3 from the outer end 140a of the sealing portion 140 to the closed line S may be 5 mm (ie, the width L3 of the sealing portion 140). W Alternatively, the width L of the sealing portion 140 is W The width L4 of the sealing portion 140 may be 10 mm, and the distance L4 from the closed line S to the accommodating portion 130 may be 5 mm (ie, the width L4 of the sealing portion 140). W 50% of the total).

[0040] The sealing portion 140 may include the above-mentioned sealing portion 151, and unsealed portions 152 and 153 (from the sealing line of the sealing portion to the boundary between the sealing portion and the accommodating portion) to be described later. A portion 152 of the unsealed portions 152 and 153 is not designed to be melted, but may be temporarily bonded by heat introduced during the sealing of the sealing portion 151. When the distance L4 from the sealing line S to the accommodating portion 130 is less than the width L of the sealing portion 140, WWhen it is 45% of [the relevant value], it may be difficult to fully ensure the interval distance between the temporarily joined temporary joining region 152 and the second folding line F2 as described above. Therefore, there is a concern that the folding knife for pressing the second folding line F2 will also press the temporary joining region 152 together. When the folding knife presses the temporary joining region 152 to cause cracks in the temporary joining region 152, insulation resistance defects may occur. The unsealed portion 153 of the sealing portion 140 may have a gap due to the gas generated inside the accommodating portion 130 to serve as a space capable of accommodating gas. However, when the distance L4 is less than 45% of the width L of the sealing portion 140 W When it is 45% of [the relevant value], the space capable of accommodating gas cannot be sufficiently defined when gas is generated. This may lead to deterioration of the high-temperature storage durability of the secondary battery.

[0041] When the distance L4 from the sealing line S to the accommodating portion 130 is greater than 55% of the width L of the sealing portion 140 W When it is 55% of [the relevant value], the distance L3 from the outer end portion 140a of the sealing portion 140 to the sealing line S may be relatively reduced, thereby causing a concern about insufficient width of the sealed portion 151. When the width of the sealed portion 151 is insufficient, the sealing characteristics of the sealing portion 140 may be insufficient.

[0042] Since the sealed range or unsealed range is optimized as described above, even when the sealing portion 140 has been folded multiple times, a decrease in insulation resistance may not occur, or the decrease in insulation resistance can be minimized, and deterioration of high-temperature storage durability or sealing characteristics can also be prevented.

[0043] The distance from the outer end portion 140a of the sealing portion 140 to the first folding line F1 (i.e., the first distance L1) can be 60% to 80% of the distance L3 from the outer end portion 140a of the sealing portion 140 to the sealing line S. For example, the distance L3 from the outer end portion 140a of the sealing portion 140 to the sealing line S can be 5 mm, and the distance L1 from the outer end portion 140a of the sealing portion 140 to the first folding line F1 can be 3.85 mm (i.e., 77% of the distance L3).

[0044] As Figure 5 shown, the outer end portion 140a of the sealing portion 140 can be folded along the first folding line F1 to provide the first folded portion 141, and when the distance L1 (see Figure 4 ) is less than 60% of the distance L3 (see Figure 4 ), the portion folded onto the upper side of the unfolded portion of the sealing portion 140 can be reduced (see Figure 5The length of the upper sealing portion of the sealing portion having a two-layer structure in []. When the length of the folding portion decreases, it may be difficult to stably maintain the folded shape of the sealing portion. When the distance L1 is greater than 80% of the distance L3, it may be difficult to sufficiently ensure the spacing distance between the temporary bonding region 152 and the first folding line F1. Therefore, there is a concern that the folding knife for pressing the first folding line F1 will also press the temporary bonding region 152 together. When the folding knife presses the temporary bonding region 152 to cause cracks in the temporary bonding region 152, insulation resistance defects may occur.

[0045] The distance L6 from the accommodating portion 130 to the second folding line F2 can be 18% to 34% of the distance L4 from the closing line S to the accommodating portion 130. For example, the distance L4 from the closing line S to the accommodating portion 130 can be 5 mm, and the distance L6 from the accommodating portion 130 to the second folding line F2 can be 1.3 mm (i.e., 26% of the distance L4).

[0046] When the distance L6 is less than 18% of the distance L4, the spacing distance between the second folding line F2 and the accommodating portion 130 decreases too much. Therefore, it may be difficult for the folding knife for pressing the second folding line F2 to smoothly press the second folding line F2 without interfering with the accommodating portion 130. When the distance L6 is greater than 34% of the distance L4, the length of the portion of the sealing portion 140 that is adjacent to the accommodating portion 130 and not folded (see Figure 6 the portion to the left of F2 in []) can be increased, resulting in an increase in the overall volume occupied by the secondary battery. The increase in the overall volume may lead to a decrease in the volumetric energy density.

[0047] Regarding the first distance L1 which is the distance from the outer end portion 140a of the sealing portion 140 to the first folding line F1 and the second distance L2 which is the distance from the first folding line F1 to the second folding line F2, the ratio of the first distance L1 to the width L of the sealing portion 140 W can be 34.65% to 42.35%, and the ratio of the second distance L2 to the width L of the sealing portion 140 W can be 43.65% to 53.35%. In the secondary battery according to this embodiment, through the optimization of the folding position, even when the sealing portion 140 has been folded multiple times, a decrease in insulation resistance does not occur or the decrease in insulation resistance can be minimized. In the secondary battery according to this embodiment, it was confirmed that the insulation resistance defect rate is 0.6% at 100 MΩ.

[0048] For example, the first distance L1 can be 3.85 mm, the second distance L2 can be 4.85 mm, and the width L of the sealing portion 140 W can be 10 mm. Here, the ratio of the first distance L1 to the width L of the sealing portion 140W The ratio can be 38.5%, and the ratio of the second distance L2 to the width L of the sealing portion 140 W can be 48.5%.

[0049] The distance L5 from the second folding line F2 to the closing line S and the width L of the sealing portion 140 W The ratio can be 20% or more. For example, the distance L5 from the second folding line F2 to the closing line S can be 3.7 mm, and here, the ratio of the distance L5 to the width L of the sealing portion 140 W can be 37%.

[0050] The distance L5 from the second folding line F2 to the closing line S can be 40% or more of the distance L3 from the outer end portion 140a of the sealing portion 140 to the closing line S.

[0051] A part 151 of the sealing portion (from the outer end of the sealing portion to the closing line of the sealing portion) can be sealed by melting between the first resin layers (e.g., PP) of the housing. A part 152 of the remaining part (152 and 153) of the sealing portion (from the closing line of the sealing portion to the boundary between the sealing portion and the accommodating portion) can be temporarily bonded by heat or the like introduced during the melting of the melting region 151 (closing portion). The temporarily bonded region 152 thus produced can be about 20% of the melting region 151 (for example, for a 5-mm melting region 151, a 1-mm temporarily bonded region 152 can be produced). Here, when interference occurs between the folding knife for forming the second folding portion 142 (see Figure 6 ) and the temporarily bonded region 152, cracks may occur in the first resin layer, resulting in insulation resistance defects. To suppress the occurrence of such defects, the distance L5 can be set to be twice or more the temporarily bonded region 152 (20% of L3).

[0052] For example, the distance L5 from the second folding line F2 to the closing line S can be 3.7 mm, and the distance L3 can be 5 mm, and here, the distance L5 can be 74% of the first distance L1.

[0053] In the sealing portion 140, when the portion from the outer end portion 140a of the sealing portion 140 to the closing line S is closed by melting and the portion from the closing line S to the accommodating portion 130 is not melted (since the temporarily bonded region is not the region that was planned to be melted as it is considered different from the planned melting region, the temporarily bonded region is regarded as an unmelted region in this specification), the distance L4 from the closing line S to the accommodating portion 130 and the width L of the sealing portion 140 WThe ratio can be 40% or more. In the secondary battery according to this embodiment, in addition to the molten region 151 and the temporary bonding region 152, the unfused portion 153 (die bond gap) of the sealing portion 140 can be sufficiently ensured to improve the insulation resistance defect rate.

[0054] For example, the distance L4 from the closing line S to the accommodating portion 130 can be 5 mm, and here, the ratio of the distance L4 to the width L of the sealing portion 140 W can be 50%.

[0055] As a reference, as described above, the distance L4 can more preferably be 45% to 55% of the width L of the sealing portion 140. W of the width L of the sealing portion 140.

[0056] The insulation resistance (R = V / I) of the secondary battery can be calculated from the current value that can be measured by applying a voltage (e.g., 25 V) between the negative electrode and the metal layer (e.g., aluminum layer) of the outer case. For example, no current consumption is confirmed in the normal state (the state where the electrolyte and the metal layer do not contact each other), while current consumption is confirmed in the defective state (the state where the electrolyte and the metal layer contact each other to cause current consumption through a chemical reaction on the surface of the metal layer). In addition, the insulation voltage of the secondary battery can be obtained by measuring the voltage value between the positive electrode and the metal layer (e.g., aluminum layer) of the outer case. For example, no voltage difference is measured in the normal state (the state where the electrolyte and the metal layer do not contact each other), and the potential difference between the positive electrode and the metal layer is measured in the defective state (the state where the electrolyte and the metal layer contact each other).

[0057] As a reference, Figure 4 T in can represent the thickness of the accommodating portion 130 and is 8.55 mm.

[0058] The description of the present invention is illustrative, and various changes and modifications can be made by those of ordinary skill in the art to which the present invention pertains without departing from the spirit and scope of the present invention defined by the appended claims.

[0059] Therefore, the embodiments described herein are for describing the technical spirit of the present invention rather than for limiting it. The scope of the technical spirit of the present invention is not limited by the embodiments.

[0060] The protection scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all technical concepts within the equivalent scope of this application should be construed as falling within the scope of the claims of this application.

Claims

1. A secondary battery, the secondary battery comprising: An electrode assembly; And A pouch-type casing, the pouch-type casing including a receiving portion and a sealing portion, the receiving portion being configured to receive the electrode assembly, and the sealing portion being configured to be formed to surround at least a part of the receiving portion to seal the receiving portion, Wherein, the sealing portion includes: A first folding portion, the first folding portion being arranged such that an outer end portion of the sealing portion is folded toward the receiving portion along a first folding line, the first folding line being spaced apart from the outer end portion of the sealing portion toward the receiving portion by a first distance; and A second folding portion, the second folding portion being arranged such that the first folding portion is folded toward the receiving portion along a second folding line, the second folding line being spaced apart from the first folding line toward the receiving portion by a second distance, Wherein, when a predetermined line spaced apart from the outer end portion of the sealing portion toward the receiving portion by a predetermined distance is referred to as a closing line, the sealing portion includes a closed portion formed by melting and closing a portion from the outer end portion of the sealing portion to the closing line, Wherein, when the distance from the outer end portion of the sealing portion to the receiving portion is referred to as the width of the sealing portion, the distance from the closing line to the receiving portion is 45% to 55% of the width of the sealing portion.

2. The secondary battery according to claim 1, wherein, The distance from the outer end portion of the sealing portion to the first folding line is 60% to 80% of the distance from the outer end portion of the sealing portion to the closing line.

3. The secondary battery according to claim 1, wherein, The distance from the receiving portion to the second folding line is 18% to 34% of the distance from the closing line to the receiving portion.

4. The secondary battery according to claim 1, wherein, The closing line is located between the first folding line and the second folding line.

5. A secondary battery, the secondary battery comprising: An electrode assembly; And A pouch-type casing, the pouch-type casing including a receiving portion and a sealing portion, the receiving portion being configured to receive the electrode assembly, and the sealing portion being configured to be formed to surround at least a part of the receiving portion to seal the receiving portion, Wherein, the sealing portion includes: A first folding portion, the first folding portion being arranged such that an outer end portion of the sealing portion is folded toward the receiving portion along a first folding line, the first folding line being spaced apart from the outer end portion of the sealing portion toward the receiving portion by a first distance and being arranged parallel to the outer end portion of the sealing portion; and A second folding portion, the second folding portion being arranged such that the first folding portion is folded toward the receiving portion along a second folding line, the second folding line being spaced apart from the first folding line toward the receiving portion by a second distance and being arranged parallel to the first folding line, Wherein, when the distance from the outer end portion of the sealing portion to the receiving portion is referred to as the width of the sealing portion, the first distance is 34.65% to 42.35% of the width of the sealing portion, and the second distance is 43.65% to 53.35% of the width of the sealing portion.

6. The secondary battery according to claim 5, wherein, When a predetermined line that is spaced a predetermined distance from the outer end of the sealing portion toward the accommodating portion and is parallel to the outer end of the sealing portion is called a closing line, in the sealing portion, the portion from the outer end of the sealing portion to the closing line is closed by melting, wherein the closing line is located between the first folding line and the second folding line, wherein the distance from the second folding line to the closing line is more than 20% of the width of the sealing portion.

7. The secondary battery according to claim 5, wherein, When a predetermined line that is spaced a predetermined distance from the outer end of the sealing portion toward the accommodating portion and is parallel to the outer end of the sealing portion is called a closing line, in the sealing portion, the portion from the outer end of the sealing portion to the closing line is closed by melting, wherein the closing line is located between the first folding line and the second folding line, wherein the distance from the second folding line to the closing line is more than 40% of the distance from the outer end of the sealing portion to the closing line.

8. The secondary battery according to claim 5, wherein When a predetermined line that is spaced a predetermined distance from the outer end of the sealing portion toward the accommodating portion and is parallel to the outer end of the sealing portion is called a closing line, in the sealing portion, the portion from the outer end of the sealing portion to the closing line is closed by melting, and the portion from the closing line to the accommodating portion is not melted, wherein the closing line is located between the first folding line and the second folding line, wherein the distance from the closing line to the accommodating portion is more than 40% of the width of the sealing portion.

9. A secondary battery, the secondary battery comprising: an electrode assembly; and a pouch-type casing, the pouch-type casing including an accommodating portion and a sealing portion, the accommodating portion being configured to accommodate the electrode assembly, the sealing portion being configured to be formed to surround at least a part of the accommodating portion to seal the accommodating portion, wherein the sealing portion includes: a first folding portion, the first folding portion being arranged such that the outer end of the sealing portion folds toward the accommodating portion along a first folding line, the first folding line being spaced a first distance from the outer end of the sealing portion toward the accommodating portion and being parallel to the outer end of the sealing portion; and a second folding portion, the second folding portion being arranged such that the first folding portion folds toward the accommodating portion along a second folding line, the second folding line being spaced a second distance from the first folding line toward the accommodating portion and being parallel to the first folding line, wherein when a predetermined line that is spaced a predetermined distance from the outer end of the sealing portion toward the accommodating portion and is parallel to the outer end of the sealing portion is called a closing line, in the sealing portion, the portion from the outer end of the sealing portion to the closing line is closed by melting, wherein the distance from the second folding line to the closing line is more than 40% of the distance from the outer end of the sealing portion to the closing line.

10. The secondary battery according to claim 9, wherein, The closed line is located between the first folding line and the second folding line.

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