Pouch-type secondary battery and manufacturing method thereof

Abstract

The pouch-type secondary battery of the present invention is a pouch-type secondary battery having a sealing portion formed by heat-sealing a double pouch-type battery case when an electrode assembly is housed therein, and includes a cover member located between the thickness surface and the pouch-type battery case on at least one of four thickness surfaces that form the thickness of the electrode assembly. As a result, the cover member separates the separator from the inner coating layer of the pouch, preventing the separator from adhering to the inner coating layer when the sealing portion is formed and preventing damage to the inner coating layer due to the movement of the electrode assembly.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0162724, filed November 23, 2021, and Korean Patent Application No. 10-2022-0157528, filed November 22, 2022.

[0002] The present invention relates to a pouch-type secondary battery and a method for manufacturing the same. [Background technology]

[0003] Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch batteries, in which the electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet.

[0004] The electrode assembly housed in the battery case is a chargeable and dischargeable power generating element having a structure of a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. It is classified into a jelly roll type in which a long sheet-like positive electrode and a negative electrode coated with an active material are wound up with a separator interposed between them, and a stack type in which a number of positive electrodes and a negative electrodes of a predetermined size are stacked sequentially with a separator interposed between them.

[0005] As shown in FIG. 1, such a pouch-type secondary battery has an electrode assembly 100 housed inside a battery case 200, and positive and negative electrode tabs are welded to two lead members 110, respectively, and exposed to the outside of the battery case 200.

[0006] 2 illustrates a series of processes for manufacturing a pouch-type secondary battery by housing an electrode assembly in a pouch-type battery case and sealing it. Referring to FIG. 2, the battery case 200 for housing the electrode assembly 100 may have a structure in which a lower case 220 and an upper case 210 covering the lower case 220 are integrated into one body, as shown in FIG. 2, and the surfaces where the lower case 220 and the upper case 210 meet may be folded. The lower case 220 and the upper case 210 each have a laminate structure including an inner coating layer, a metal layer, and an outer coating layer.

[0007] The battery case 200 is provided with an electrode assembly receiving portion 230 having a recessed interior for receiving the electrode assembly 100. The electrode assembly is received in the receiving portion, and the surface where the lower case 220 and the upper case 210 meet (dotted line) is folded. Then, a sealing member (not shown) is used to form a heat-sealed sealing portion S along the outer periphery of the electrode assembly receiving portion, thereby manufacturing a pouch-type secondary battery.

[0008] The sealing portion is formed by applying pressure to the area to be sealed at high temperature using a sealing member. When the sealing member applies high temperature and pressure, the laminated battery case is heated, melting the resin of the inner coating layer, and the double battery case is heat-sealed to form the sealing portion.

[0009] However, when a sealing member is applied to a portion of the battery case to be sealed at a high temperature to form a sealing portion, the binder component in the separator protruding from the end of the electrode assembly and the inner coating layer of the battery case may melt together due to the heat, causing the inner coating layer of the battery case to be heat-sealed to the electrode assembly. In this case, if the secondary battery flows for various reasons, such as due to an external physical impact, the internal electrode assembly may flow, and a flow force may be transmitted to the inner coating layer of the battery case bonded to the electrode assembly. This may cause damage such as cracks in the inner coating layer, as shown in FIG. 11, which may lead to insulation failure of the battery case.

[0010] Therefore, there is a need for technological development that can prevent such insulation failures. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made to solve the above problems by providing a pouch-type secondary battery and a manufacturing method thereof, in which the separator is heat-sealed to the inner coating layer of the battery case due to melting of the binder component of the separator when forming a sealing portion of the pouch-type battery, thereby preventing damage to the inner coating layer of the battery case when the electrode assembly is moved. [Means for solving the problem]

[0012] A pouch-type secondary battery according to an embodiment of the present invention is a pouch-type secondary battery having a sealing portion formed by heat-sealing a double pouch-type battery case when an electrode assembly is housed therein, and may include a cover member located between the thickness surface of the electrode assembly and the pouch-type battery case on at least one of four thickness surfaces that form the thickness of the electrode assembly.

[0013] In an embodiment of the present invention, the cover member may be positioned along the sealing portion between the thickness surface of the electrode assembly and the pouch-type battery case.

[0014] In one embodiment of the present invention, the pouch-type battery case may be formed by folding a pouch-type battery case having a pair of recessed storage sections for storing electrode assemblies along a folding line such that the pair of storage sections are symmetrically positioned, and in this case, the sealing section may be formed along the remaining outer periphery of the storage section excluding the periphery of the folding line.

[0015] In one embodiment of the present invention, the sealing portion may be formed along the outer periphery of the receiving portion.

[0016] In one embodiment of the present invention, the cover member may be made of a heat-resistant polymer material having a melting point (Tm) higher than the thermocompression temperature at which the sealing portion is formed.

[0017] In an embodiment of the present invention, the cover member may be tightly attached to a thickness surface of the electrode assembly.

[0018] In one embodiment of the present invention, the cover member may have a size that allows the cover member to completely cover the thickness surface of the electrode assembly.

[0019] In one embodiment of the present invention, the vertical length of the cover member corresponds to the thickness of the electrode assembly, and the cover member may be positioned in an I-shape between the thickness surface and the pouch-type battery case.

[0020] In one embodiment of the present invention, the vertical length of the cover member is greater than the thickness length of the electrode assembly, and the cover member may be positioned between the thickness surface and the pouch-type battery case, with both side edges in the thickness direction folded to form a U-shape that wraps around the thickness surface of the electrode assembly.

[0021] In one embodiment of the present invention, the electrode assembly may be one selected from a stack-type electrode assembly, a stack-folding type electrode assembly, a lamination-stack type electrode assembly, and a jelly roll type electrode assembly.

[0022] A method for manufacturing a pouch-type secondary battery according to one embodiment of the present invention includes a step of preparing an electrode assembly, a cover member preparation step of cutting a cover member, a storage step of storing the electrode assembly and the cover member inside a pouch-type battery case, and a sealing step of sealing a predetermined sealing portion of the pouch-type battery case by thermocompression bonding, wherein in the storage step, the cover member is stored so as to be positioned between a thickness surface of the electrode assembly corresponding to the predetermined sealing portion and the pouch-type battery case.

[0023] In an embodiment of the present invention, the step of preparing the electrode assembly may include an assembling step of assembling the positive electrode and the negative electrode so that a separator is interposed between them, a welding step of welding the positive electrode tab to the positive electrode lead and the negative electrode tab to the negative electrode lead, respectively, and a step of wrapping the welded joints with a protective film.

[0024] In an embodiment of the present invention, the step of preparing the cover member may include cutting the cover member to a size that allows the cover member to cover a thickness surface that forms a thickness of the electrode assembly in an I-shape.

[0025] In an embodiment of the present invention, the step of preparing the cover member may include cutting the cover member to a size that covers a thickness surface of the electrode assembly in a U-shape.

[0026] In an embodiment of the present invention, the placing step may include placing the cover member in close contact with a thickness surface of the electrode assembly corresponding to a portion to be sealed. [Effects of the Invention]

[0027] In the pouch-type secondary battery and manufacturing method according to the present invention, a cover member is inserted into the space between the electrode assembly and the pouch-type battery case, and the cover member separates the separator from the inner coating layer of the battery case. This prevents the separator from adhering to the inner coating layer of the battery case even if the binder component of the separator melts when forming the sealing part. This prevents poor insulation due to damage to the inner coating layer during flow of the electrode assembly, a problem with conventional pouch-type secondary batteries.

[0028] Furthermore, the cover member fills the space between the electrode assembly and the pouch, thereby reducing the impact caused by the movement of the electrode assembly. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a perspective view of a pouch-type secondary battery according to the prior art. [Figure 2]1 is a flowchart illustrating a manufacturing process of a pouch-type secondary battery according to the prior art. [Figure 3] 1 is a schematic diagram of a pouch-type secondary battery according to one embodiment of the present invention. [Figure 4] 4 is a schematic diagram of an electrode assembly housed inside the pouch-type secondary battery of FIG. 3 and a cross-sectional view taken along line BB'. FIG. [Figure 5] FIG. 4 is a cross-sectional view taken along line AA' in FIG. [Figure 6] FIG. 4 is an exploded view of the pouch-type secondary battery of FIG. 3. [Figure 7] 10 is a top view showing a state in which the cover member is in close contact with the electrode assembly; FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along CC' in FIG. 7, illustrating the cover member according to the first embodiment of the present invention. [Figure 9] FIG. 8 is a cross-sectional view taken along the line CC' in FIG. 7, illustrating a cover member according to a second embodiment of the present invention. [Figure 10] 1 is a flowchart of a method for manufacturing a pouch-type secondary battery according to an embodiment of the present invention. [Figure 11] 1A and 1B are conceptual diagrams for explaining problems with the prior art, in which (a) shows a secondary battery before flow and (b) shows a secondary battery after flow. DETAILED DESCRIPTION OF THE INVENTION

[0030] Because the present invention can be modified in various ways and can take various forms, specific embodiments are shown in the drawings and described in detail herein, but it is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

[0031] In this application, terms such as "comprise" and "have" are intended to specify the presence of a feature, numeral, step, operation, component, part, or combination thereof described in the specification, but should be understood as not excluding the possible presence or addition of one or more other features, numerals, steps, operations, components, parts, or combinations thereof. Furthermore, when a layer, film, region, plate, or other part is described as being "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part between them. Conversely, when a layer, film, region, plate, or other part is described as being "under" another part, this includes not only the case where it is "directly under" the other part, but also the case where there is another part between them. Furthermore, in this application, "over" can include not only the case where it is "on top" but also the case where it is "under" the other part.

[0032] (Pouch-type secondary battery according to the first embodiment) FIG. 3 is a schematic diagram of a pouch-type secondary battery according to one embodiment of the present invention, FIG. 4 is a schematic diagram of an electrode assembly housed inside the pouch-type secondary battery of FIG. 3 and a cross-sectional view taken along line B-B', FIG. 5 is a cross-sectional view taken along line A-A' in FIG. 3, and FIG. 6 is an exploded view of the pouch-type secondary battery of FIG. 3.

[0033] Referring to these drawings, a pouch-type secondary battery B according to an embodiment of the present invention may include a pouch-type battery case 200 and an electrode assembly 100 housed inside the pouch-type battery case.

[0034] 2 and 6, the pouch-type battery case 200 is for hermetically housing the electrode assembly 100, and has a pair of recessed housing portions 230; 231, 232 inside to house the electrode assembly 100, and may be bent along a bending line L-L' so that the pair of housing portions 230; 231, 232 are symmetrically positioned.

[0035] A pouch-type secondary battery B according to one embodiment of the present invention has a sealing portion S formed by heat sealing the double pouch-type battery case 200 when the electrode assembly 100 is housed in a housing portion provided in the pouch-type battery case 200, and includes a cover member 300 located between the thickness surface T of the electrode assembly and the pouch-type battery case 200 in at least one of four thickness surfaces T that form the thickness of the electrode assembly 100.

[0036] 2 and 6, in the pouch-type secondary battery B according to an embodiment of the present invention, a sealing portion S may be formed along the remaining outer periphery of the receiving portions 231 and 232, excluding the periphery of the folding line L-L'. Since the lower case 210 and the upper case 220 covering the lower case 210 are connected to each other around the folding line L-L' of the outer periphery of the receiving portions 231 and 232, and fusion between the lower case 210 and the upper case 220 is not required, the sealing portion S may not be formed in this area, as shown in FIG.

[0037] However, this is not limited to this, and two pouch-type battery cases each with one storage section can be prepared, with one battery case serving as the lower case and the other battery case covering the lower case, and then a sealing section can be formed along the outer periphery of the storage section.

[0038] The electrode assembly 100 of the present invention may have a structure in which at least one basic unit 10 having a structure of positive electrode 11 / separator 12 / negative electrode 13 / separator 12 is stacked, and the side surface of the electrode assembly formed along the stacking direction is the thickness surface T. Referring to FIG. 4 , the separator 12, which is cut to be relatively longer than the positive electrode 11 and the negative electrode 13, may protrude from the ends of the positive electrode 11 and the negative electrode 13 on the thickness surface T. Therefore, when the sealing portion of the battery case 200 is pressurized at a high temperature to form the sealing portion S, the binder component of the separator 12 and the inner coating layer constituting the battery case 200 may melt together, and the separator 12 may be fused to the inner coating layer of the sealing portion S of the battery case 200 at the thickness surface T.

[0039] Therefore, in the present invention, by interposing the cover member 300 between the thickness surface T of the electrode assembly 100 and the pouch-type battery case 200, the separator 12 is prevented from being melted and bonded to the inner coating layer of the battery case 200 when the sealing portion S is formed. As a result, even if the electrode assembly flows, the inner coating layer of the battery case 200 is not damaged, and the risk of poor insulation can be prevented.

[0040] The cover member 300 serves to separate the separator 12 from the inner coating layer of the pouch-type battery case 200. As shown in FIG. 4, the separator 12 protrudes to the outside of the electrode at a thickness plane T that forms the thickness of the electrode assembly 100, and therefore the cover member 300 is located in the space between the thickness plane T of the electrode assembly 100 and the pouch-type battery case 200.

[0041] In addition, the cover member 300 must prevent the binder of the separator 12 from melting and adhering to the inner coating layer around the sealing portion during the sealing process for forming the sealing portion S. Therefore, it is preferable that the cover member 300 be positioned between the thickness surface T of the electrode assembly 100 and the pouch-type battery case 200 along the sealing portion S.

[0042] Here, the reason why the cover member 300 is positioned between the thickness surface T of the electrode assembly 100 and the pouch-type battery case 200 along the sealing portion S will be described with reference to FIGS.

[0043] Referring to these drawings, the sealing portion S may be formed along the remaining outer periphery, excluding the folding line L-L', of the outer periphery of the housing that houses the electrode assembly 100. The cover member 300 is interposed to prevent the separator binder and the inner coating layer of the battery case from being heat-sealed together during the sealing process of heat-sealing the double battery case, and therefore, it is preferable that the cover member be interposed along the entire sealing portion S.

[0044] 5 and 6, the cover member 300 is inserted into the space between the thickness surface T of the electrode assembly 100 and the pouch-type battery case 200, and can prevent direct contact between the separator 12 at the end of the electrode assembly 100 and the pouch-type battery case 200. This can to some extent suppress a temperature rise in the separator 12 that accompanies a temperature rise in the sealing portion S when the sealing portion S is formed, and even if the binder component contained in the separator 12 melts, the cover member 300 separates the separator 12 from the inner coating layer of the battery case 200, thereby preventing the separator 12 from adhering to the inner coating layer of the battery case 200.

[0045] In addition, since the cover member 300 is inserted into the space between the electrode assembly 100 and the pouch-type battery case 200, it can also fill the space and thereby reduce the impact caused by the movement of the electrode assembly.

[0046] The cover member is preferably a heat-resistant material that does not melt during the sealing process to form the sealing portion. That is, the cover member is preferably a heat-resistant polymer material whose melting point (Tm) is higher than the thermocompression temperature when the sealing portion is formed. The cover member is also preferably an insulating polymer material and may be in the form of a film.

[0047] If the cover member is melted together with the inner coating layer of the pouch-type battery case during the sealing process, the separator-cover member-inner coating layer of the electrode assembly may be melt-bonded, and the flow impact may be transmitted to the inner coating layer during flow of the electrode assembly, damaging the inner coating layer.

[0048] Meanwhile, since the thermocompression temperature for forming the sealing portion during the sealing process is typically 100° C. to 200° C., the melting point of the cover member is preferably, but not limited to, a polymer material with a melting point of 180° C. to 300° C. Heat-resistant polymer materials with melting points within the above temperature range include polyimide, polytetrafluoroethylene, polyethylene terephthalate, polycarbonate, polyphenyl sulfide, Teflon (registered trademark), acrylonitrile butadiene styrene, polyacrylate, etc., and the cover member of the present invention may contain one or more selected from the group consisting of the above polymer resins.

[0049] 6, the cover member 300 is disposed at a position where it can come into contact with the electrode lead 110, and is therefore preferably made of an insulating material because it must not be electrically connected to the electrode lead 110 and conduct electricity. That is, although conductive materials such as metals do not melt at high temperatures and can prevent the inner coating layer of the battery case from being thermally fused to the electrode assembly, they are not suitable as materials for the cover member 300 of the present invention because they may cause an internal short circuit if they come into contact with the electrode lead 110.

[0050] 7, the cover member 300 may be closely attached to the thickness surface T of the electrode assembly 100. That is, the cover member 300 is positioned close to the thickness surface T so that no gap is formed between the cover member 300 and the electrode assembly 100. If there is a gap between the cover member and the thickness surface, the separator may protrude through the gap and invade the separation space between the cover member and the pouch case, which is undesirable.

[0051] The size of the cover member is preferably such that the cover member can completely cover the thickness surface of the electrode assembly so as to prevent the separator from contacting the inner coating layer of the pouch-type battery case. Therefore, the vertical length of the cover member may be 100% to 150%, 100% to 130%, or 100% to 120% of the thickness of the electrode assembly. Here, the vertical direction of the cover member refers to the thickness direction of the electrode assembly.

[0052] Fig. 8 is a cross-sectional view taken along line CC' in Fig. 7, illustrating the shape of a cover member according to an embodiment of the present invention. Referring to Fig. 8, the cover member according to an embodiment of the present invention has a longitudinal length corresponding to the thickness of the electrode assembly, and can be positioned between the thickness surface of the electrode assembly and the pouch-type battery case in an I-shaped manner.

[0053] In an embodiment of the present invention, the electrode assembly 100 housed in the battery case 200 may be one selected from the group consisting of a jelly-roll type electrode assembly in which a separator is interposed between long sheet-like positive and negative electrodes and then wound up; a stack type electrode assembly in which rectangular positive and negative electrodes are stacked with a separator interposed therebetween; a stack-folding type electrode assembly in which the unit cells are wound up with a long separator film; and a lamination-stack type electrode assembly in which the unit cells are stacked with a separator interposed therebetween and then attached to each other.

[0054] 1, the electrode assembly 100 may include an electrode lead 110 composed of a positive electrode lead and a negative electrode lead. The positive electrode lead is welded to a positive electrode tab, and the negative electrode lead is welded to a negative electrode tab, and the positive electrode lead and the negative electrode lead may be exposed to the outside of the battery case 200. The positive electrode lead and the negative electrode lead may be drawn out in the same direction or may face each other.

[0055] Since the positive electrode lead and the negative electrode lead are made of a metallic material, in order to ensure insulation and sealing properties, a pair of insulating films (not shown) facing each other may be positioned in the sealing portion 230 where the positive electrode lead and the negative electrode lead are positioned, and each of the positive electrode lead and the negative electrode lead may be arranged to pass between the pair of insulating films (not shown).

[0056] The pouch-type battery case 200 may have a laminate structure including an inner coating layer, a metal layer, and an outer coating layer. The inner coating layer must have insulating and electrolytic resistance because it is in direct contact with the electrode assembly, and must have excellent sealing properties to seal the case from the outside, i.e., the sealing portions where the inner layers are thermally bonded must have excellent thermal adhesive strength.

[0057] The material for such an inner coating layer may be selected from polyolefin resins such as polypropylene, polyethylene, polyethylene acrylic acid, and polybutylene, which have excellent chemical resistance and sealing properties, polyurethane resins, and polyimide resins, but is not limited to these. Polypropylene (PP), which has excellent mechanical properties such as tensile strength, rigidity, surface hardness, and impact resistance, and excellent chemical resistance, is the most preferred.

[0058] The metal layer in contact with the inner coating layer corresponds to a barrier layer that prevents moisture and various gases from penetrating into the interior of the battery from the outside, and a preferred material for such a metal layer is an aluminum thin film, which is lightweight yet has excellent formability.

[0059] An outer coating layer is provided on the other side of the metal layer. This outer coating layer may be made of a heat-resistant polymer having excellent tensile strength, moisture-proof properties, and air-proof properties to protect the electrode assembly and ensure heat resistance and chemical resistance. Examples of the outer coating layer include, but are not limited to, nylon or polyethylene terephthalate.

[0060] (Pouch-type secondary battery according to the second embodiment) Fig. 9 is a cross-sectional view taken along the line CC' in Fig. 7, illustrating the shape of a cover member according to a second embodiment of the present invention. Referring to Fig. 9, in the cover member 300 according to the second embodiment of the present invention, the longitudinal length of the cover member is greater than the thickness of the electrode assembly, and the cover member has both thickness-wise end portions E and E' that are bent to form a U-shape that envelops the thickness surface of the electrode assembly, and can be positioned between the thickness surface of the electrode assembly and the pouch-type battery case.

[0061] In the second embodiment, when both ends E and E' of the cover member are folded, the thickness of the cover member is covered by the cover member in a larger area than in the first embodiment, making it more difficult for the separator of the electrode assembly to come into contact with the inner coating layer of the pouch-type battery case. This further reduces the possibility of the separator being melt-bonded to the inner coating layer when forming the sealing part.

[0062] The second embodiment differs from the first embodiment only in the shape of the cover member, and therefore further detailed description will be omitted.

[0063] <Manufacturing method of pouch-type secondary battery> 10 is a flowchart of a method for manufacturing a pouch-type secondary battery according to one embodiment of the present invention. Referring to FIG. 10, the method for manufacturing a pouch-type secondary battery according to the present invention may include (S10) preparing an electrode assembly, (S20) cutting a cover member, (S30) placing the electrode assembly and the cover member inside a pouch-type battery case, and (S40) sealing a portion of the pouch-type battery case to be sealed by thermocompression bonding.

[0064] The step of (S10) preparing an electrode assembly may be a step of preparing an electrode assembly 100 in which an electrode lead 110 is coupled to an electrode tab (not shown), as shown in FIG. 4. Such an electrode assembly has a structure in which a plurality of electrodes 11 and 13 and a plurality of separators 12 are alternately stacked, and the plurality of electrodes 11 and 13 are each provided with an electrode tab (not shown), to which an electrode lead 110 is coupled. Here, the plurality of electrodes may be positive and negative electrodes, and the electrode tabs may be a positive electrode tab provided on the positive electrode and a negative electrode tab provided on the negative electrode. The electrode lead 110 may be a positive electrode lead coupled to the positive electrode tab and a negative electrode lead coupled to the negative electrode tab.

[0065] The electrode leads are used to connect an external device to the electrode assembly, and in the subsequent storage step (S30), the ends of the electrode leads are drawn out of the pouch-type battery case.

[0066] In one specific example, the step of (S10) preparing an electrode assembly may include (S11) assembling a positive electrode and a negative electrode so that a separator is interposed between them, (S12) welding a positive electrode tab to a positive electrode lead and a negative electrode tab to a negative electrode lead, respectively, and (S13) wrapping the welded portion with a protective film.

[0067] The cover member preparation step (S20) is a step of preparing the cover member by cutting it to a suitable size. The cover member is preferably a heat-resistant polymer material having a melting point (Tm) higher than the thermocompression temperature when forming the sealing part, and may be in the form of a film having insulating properties.

[0068] The vertical length of the cover member may be 100 to 150% of the thickness of the electrode assembly. In one specific example, the cover member preparation step may involve cutting the cover member to a size that covers the thickness surface of the electrode assembly in an I-shape. In another specific example, the cover member preparation step may involve cutting the cover member to a size that covers the thickness surface of the electrode assembly in a U-shape.

[0069] The placing step (S30) is a step of placing the electrode assembly and the cover member inside a pouch-type battery case. At this time, as shown in Fig. 7, the cover member 300 may be placed in close contact with the thickness surface of the electrode assembly 100 so that the cover member 300 is positioned between the thickness surface corresponding to the sealing portion and the pouch-type battery case, and the cover member and the electrode assembly may be placed inside the pouch-type battery case.

[0070] The sealing step (S40) is a step of forming a sealing portion by thermocompression bonding a sealing portion on the edge of the electrode assembly receiving portion. With the electrode assembly housed in the pouch-type battery case, the sealing portion of the upper case and the sealing portion of the lower case are brought into close contact with each other, and then, using a pair of sealing bars positioned above the sealing portion of the upper case and below the sealing portion of the lower case, the upper and lower cases are hot-pressed with a predetermined force so that they can be tightly sealed together. As a result, the inner coating layer of the hot-pressed sealing portion is melted, forming a sealing portion.

[0071] Although the preferred embodiments of the present invention have been described above with reference to the drawings, it will be understood that those skilled in the art or those with ordinary knowledge in the art can make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as set forth in the claims.

[0072] Therefore, the technical scope of the present invention should not be limited to the content described in the Summary of the Invention of the specification, but should be defined by the claims. [Explanation of symbols]

[0073] 100: Electrode assembly 110: Electrode lead 200: Pouch-type battery case 210: Upper case 220: Lower case 230: Storage area S: Sealing part T: Thickness plane 300: Cover material

Claims

1. A pouch-type secondary battery having a sealing part formed by heat-sealing a double pouch-type battery case with an electrode assembly housed therein, a cover member positioned between the thickness surface of the electrode assembly and the pouch-type battery case on at least one of four thickness surfaces that form the thickness of the electrode assembly; The cover member is a sealing portion disposed between the thickness surface of the electrode assembly and the pouch-type battery case along the sealing portion; The length of the cover member in the vertical direction is 100% to 150% of the thickness of the electrode assembly, the cover member has a size to cover a thickness surface of the electrode assembly in an I-shape or a size to cover a thickness surface of the electrode assembly in a U-shape, When the cover member has a size that covers the thickness surface in an I-shape, the length in the vertical direction corresponds to the thickness of the electrode assembly; When the cover member has a size that covers the thickness surface in a U-shape, the length in the vertical direction is greater than the length of the electrode assembly; The cover member is It is a heat-resistant polymer material whose melting point is higher than the heat-compression temperature when forming the sealing part. The cover member is disposed to prevent direct contact between a separator at an end of the electrode assembly and the pouch-type battery case.

2. The pouch-type battery case includes: The pouch-type battery case has a pair of recessed storage sections for storing an electrode assembly, and is folded along a folding line so that the pair of storage sections are symmetrically positioned, The pouch-type secondary battery according to claim 1 , wherein the sealing portion is formed along the remaining outer periphery of the housing portion excluding the periphery of the folding line.

3. The sealing portion is The pouch-type secondary battery according to claim 2 , wherein the pouch-type secondary battery is formed along the outer periphery of the storage portion.

4. The cover member is The pouch-type secondary battery according to claim 1 , wherein the electrode assembly is in close contact with the thickness surface of the electrode assembly.

5. The cover member is The pouch-type secondary battery according to claim 1 , wherein the cover member has a size capable of completely covering the thickness surface of the electrode assembly.

6. The cover member has a length in a vertical direction corresponding to a thickness of the electrode assembly, The pouch-type secondary battery according to claim 5 , wherein the cover member is I-shaped and positioned between the thickness surface and the pouch-type battery case.

7. The length of the cover member in the vertical direction is greater than the thickness of the electrode assembly, 6. The pouch-type secondary battery according to claim 5, wherein the cover member is bent at both ends in a thickness direction to form a U-shape that wraps around the thickness surface of the electrode assembly and is positioned between the thickness surface and the pouch-type battery case.

8. 8. The pouch-type secondary battery according to claim 1, wherein the electrode assembly is one selected from the group consisting of a stack-type electrode assembly, a stack-folding type electrode assembly, a lamination-stack type electrode assembly, and a jelly-roll type electrode assembly.

9. a cover member preparation step of cutting the cover member; a housing step of housing the electrode assembly and the cover member inside a pouch-type battery case; a sealing step of sealing a predetermined sealing portion of the pouch-type battery case by heat compression, In the housing step, the cover member is housed between a thickness surface of the electrode assembly corresponding to the intended sealing portion and the pouch-type battery case, The cover member is a heat-resistant polymer material having a melting point higher than the heat-compression temperature in the sealing step; The method for manufacturing a pouch-type secondary battery, wherein the cover member is arranged to prevent direct contact between a separator at an end of the electrode assembly and the pouch-type battery case.

10. The method further includes providing an electrode assembly; The step of preparing an electrode assembly includes: an assembling step in which a separator is interposed between the positive electrode and the negative electrode; a welding step of welding the positive electrode tab to the positive electrode lead and the negative electrode tab to the negative electrode lead, respectively; The method for manufacturing a pouch-type secondary battery according to claim 9, further comprising the step of wrapping the welded portion with a protective film.

11. The cover member preparation step includes: The method for manufacturing a pouch-type secondary battery according to claim 9 , further comprising cutting the cover member to a size that covers the thickness surface that forms a thickness of the electrode assembly in an I-shape.

12. The cover member preparation step includes: The method for manufacturing a pouch-type secondary battery according to claim 9 , further comprising cutting the cover member into a size that covers the thickness surface that forms a thickness of the electrode assembly in a U-shape.

13. The storing step includes:

13. The method for manufacturing a pouch-type secondary battery according to claim 9, wherein the cover member is housed in a state of being in close contact with the thickness surface that forms the thickness of the electrode assembly corresponding to a predetermined sealing portion.

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