Secondary battery and sealing device for manufacturing same

Abstract

Provided are a secondary battery having high sealing reliability and a sealing device which is for manufacturing the secondary battery and capable of reducing tact time. A secondary battery according to the present invention includes a battery case which has embedded therein an electrode assembly having electrode leads protruding therefrom and which includes a sealing portion structured to include a sealed outer periphery portion. The sealing portion includes: a first sealing portion at the electrode lead side of the battery case; and a second sealing portion at the electrode lead side of the battery case, wherein the first sealing portion and the second sealing portion each include one end and the other end in the protruding direction of the electrode leads, and the other end of the second sealing portion extends in a direction opposite to the protruding direction of the electrode leads and further than the other end of the first sealing portion.

Description

Secondary batteries and sealing devices for their manufacture

[0001] The present invention relates to a secondary battery and a sealing device for manufacturing a secondary battery. In particular, the present invention relates to a secondary battery with improved sealing reliability and a sealing device capable of reducing the tact time during the manufacture of such a secondary battery. This application claims priority to Korean Patent Application No. 10-2023-0144415, filed October 26, 2023, and Korean Patent Application No. 10-2024-0074993, filed June 10, 2024, the entire contents of which are incorporated herein by reference.

[0002] Among rechargeable and dischargeable secondary batteries, lithium secondary batteries are used as power sources for portable electronic devices, or in series-connected units for high-power hybrid and electric vehicles. Lithium secondary batteries have a three-fold higher operating voltage than nickel-cadmium or nickel-metal hydride batteries and boast superior energy density per unit weight, making them the most widely used secondary battery.

[0003] These lithium secondary batteries are classified into cylindrical and prismatic batteries, in which the electrode assembly is built into a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is built into a battery case made of an aluminum laminate sheet, depending on the shape of the battery case. Here, the electrode assembly built into the battery case is a power plant capable of charging and discharging, which is composed of a positive electrode, a negative electrode, and a separator structure interposed between the positive and negative electrodes, and is classified into a jelly-roll type in which a separator is interposed between long sheet-shaped positive and negative electrodes coated with an active material and wound, and a stack type in which a plurality of positive and negative electrodes are sequentially stacked while interposing the separator between them.

[0004] Among these, pouch-type batteries with a structure in which a stack-type or stack / folding-type electrode assembly is embedded in a battery case made of aluminum laminate sheet are in high demand due to their advantages such as low manufacturing cost, small weight, and easy deformation.

[0005] Figure 1 is a top view of a typical pouch-type secondary battery.

[0006] Referring to FIG. 1, a conventional pouch-type secondary battery (10) includes a battery case (20) in which an electrode assembly (11) is mounted in a receiving portion (21) and which includes a sealing portion (25) having a sealed outer periphery. In addition, the pouch-type secondary battery (10) includes an electrode lead (30) which is electrically connected to an electrode tab (15) included in the electrode assembly (11) and protrudes outwardly from the battery case (20) via the sealing portion (25), and a lead film (40) is positioned between the upper and lower portions of the electrode lead (30) and the sealing portion (25).

[0007] Such pouch-type secondary batteries (10) need to be manufactured to prevent electrolyte leakage and have high sealing strength, thereby ensuring excellent sealing reliability. However, with the demand for increased energy density, there is a problem in that the amount of gas generated within the pouch-type secondary battery (10) also increases. If the sealing strength of the sealing portion (25) is insufficient, the gas generation may cause a venting phenomenon in which the battery case (20) bursts. Accordingly, the sealing of the pouch-type secondary battery (10) has become an item that must be managed with even greater importance.

[0008] Figure 2 is a schematic diagram of a conventional sealing device for manufacturing such a pouch-type secondary battery.

[0009] Referring to FIG. 2, a conventional sealing device (50) is installed so as to be able to be lifted by sealing blocks (50a, 50b) positioned at the upper and lower portions of the sealing portion (25) respectively and an elevating means (60) that can move them, thereby pressurizing the sealing portion (25) by lifting. At this time, the sealing device (50) generates heat by a heating means (not shown) built into the sealing blocks (50a, 50b) to heat the sealing portion (25). The inner surface of the battery case (20) is made of a resin such as polypropylene (PP). When the sealing device (50) heats and pressurizes the sealing portion (25), the resin on the inner surface of the battery case (20) is fused and sealed.

[0010] Since the pouch-type secondary battery (10) includes sealing portions (25) at least three and at most four along the edge of the battery case (20), there are many areas to be sealed. Therefore, when manufacturing a pouch-type secondary battery, it is necessary to minimize the sealing time by taking the tact time into consideration. However, the conventional sealing device (50) has a limitation in supplying sufficient heat in a short time. As the temperature of the sealing device (50) increases, the sealing strength will improve, but since damage occurs on the surface of the battery case (20) above a certain temperature, there is a limit to the temperature increase of the sealing device (50). However, if the temperature of the sealing device (50) is limited and the sealing time is prolonged, there is a problem that it is difficult to manage the tact time.

[0011] In addition, the sealing portion (25) of the protruding side of the electrode lead (30) requires a particularly large amount of heat because it must be fused to the lead film (40) between the upper and lower battery cases (20). Therefore, in the past, in order to supplement the heat insufficient in the sealing portion (25) of the protruding side of the electrode lead (30), there was an example of sealing by introducing a lead heater system that heats the electrode lead (30) to indirectly supplement heat to the sealing portion (25) near the electrode lead (30).

[0012] However, conventional sealing devices still have limitations in providing sufficient heat in a short period of time. Furthermore, when using a thick, high-molded pouch as the outer packaging material, the ability to supply sufficient heat to the sealing area becomes even more limited. Therefore, improvements in tact time management are required for conventional sealing devices.

[0013] The problem to be solved by the present invention is to provide a secondary battery with high sealing reliability.

[0014] Another problem to be solved by the present invention is to provide a sealing device for manufacturing a secondary battery that can reduce the tact time.

[0015] In order to solve the above problem, a secondary battery according to the present invention includes a battery case having an electrode assembly having a protruding electrode lead built in and a sealing portion having a structure in which the outer periphery is sealed, wherein the sealing portion includes a first sealing portion on the electrode lead side of the battery case; and a second sealing portion on the electrode lead side of the battery case, wherein the first sealing portion and the second sealing portion each include one end and the other end in the protruding direction of the electrode lead, and the other end of the second sealing portion extends in a direction opposite to the protruding direction of the electrode lead more than the other end of the first sealing portion.

[0016] The length of the first sealing portion may be longer than the length of the second sealing portion, and the width of the second sealing portion may be greater than the width of the first sealing portion.

[0017] The first sealing portion and the second sealing portion may overlap at least partially in the protruding direction of the electrode lead.

[0018] One end of the second sealing portion and one end of the first sealing portion may be positioned on the same line.

[0019] One end of the second sealing portion may be spaced apart from one end of the first sealing portion in the opposite direction of the protrusion direction of the electrode lead.

[0020] The secondary battery further includes a lead film positioned at a portion corresponding to the first sealing portion and the second sealing portion, the lead film including one end and the other end in the protruding direction of the electrode lead, and a polymer ball is formed by a fused resin between the battery case and the lead film inside the second sealing portion, and the polymer ball may be formed so as not to protrude from the other end of the lead film.

[0021] In order to solve the above other problems, a sealing device according to the present invention is a sealing device for sealing a battery case having an electrode assembly with protruding electrode leads, the sealing device including a main sealing block including an upper sealing block that applies pressure downward from an upper portion of a first sealing portion on the electrode lead side of the battery case and a lower sealing block that applies pressure upward from a lower portion of the first sealing portion; and a post sealing block including an upper sealing block that applies pressure downward from an upper portion of a second sealing portion on the electrode lead side of the battery case and a lower sealing block that applies pressure upward from a lower portion of the second sealing portion; wherein the first sealing portion and the second sealing portion each include one end and the other end in the protruding direction of the electrode leads, and the shapes of the main sealing block and the post sealing block are different from each other such that the other end of the second sealing portion extends in a direction opposite to the protruding direction of the electrode leads more than the other end of the first sealing portion.

[0022] A lead film including one end and the other end in the protruding direction of the electrode lead is attached to the electrode lead, and the main sealing block includes a concave portion corresponding to the electrode lead side including the lead film on the lower surface of the upper sealing block and the upper surface of the lower sealing block, respectively.

[0023] The upper sealing block lower surface and the lower sealing block upper surface of the main sealing block include a peripheral pressurizing portion that pressurizes the battery case, and the concave portion can pressurize the electrode lead and the lead film.

[0024] The above concave portion may include an electrode lead pressurizing portion that pressurizes the electrode lead; and an intermediate pressurizing portion that connects the electrode lead pressurizing portion and the peripheral pressurizing portion in a stepwise manner.

[0025] The length of the above main sealing block may be longer than the width of the electrode lead including the lead film and may extend to the battery case around it.

[0026] The length of the above post sealing block may be shorter than the length of the above main sealing block.

[0027] The upper sealing block and the lower sealing block of the above main sealing block may have a step formed in a direction from top to bottom, and the upper sealing block and the lower sealing block of the above post sealing block may have a step formed in a direction opposite to the protrusion direction of the electrode lead.

[0028] The above post sealing block may include a first pressing portion that pressurizes a portion overlapping the first sealing portion; and a second pressing portion that pressurizes a portion opposite to the protrusion direction of the electrode lead compared to the first pressing portion.

[0029] The width of the second pressurizing portion does not exceed 50% of the width of the first pressurizing portion.

[0030] The first pressurizing portion may protrude further toward the electrode lead than the second pressurizing portion.

[0031] The height difference between the first pressurizing portion and the second pressurizing portion may be 0.1 mm to 5 mm.

[0032] For example, the second pressurizing portion protrudes in a direction perpendicular to the first pressurizing portion, the first pressurizing portion has a first pressurizing surface that is a single plane and a pressurizing surface that contacts the battery case, the second pressurizing portion has a second pressurizing surface that is a single plane and a pressurizing force of the first pressurizing surface is greater than the pressurizing force of the second pressurizing surface.

[0033] For another example, the second pressurizing portion protrudes in a direction perpendicular to the first pressurizing portion, and the first pressurizing portion includes a peripheral pressurizing portion that pressurizes the battery case; an electrode lead pressurizing portion that pressurizes the electrode lead; and an intermediate pressurizing portion that connects the electrode lead pressurizing portion and the peripheral pressurizing portion in a stepwise manner.

[0034] Preferably, when the battery case is positioned on the main sealing block, the fused resin between the battery case and the lead film is pushed into the first sealing portion by the main sealing block to form a polymer ball, and when the battery case is moved from the main sealing block and positioned on the post sealing block, the polymer ball is pressed by the post sealing block.

[0035] It is preferable that a step be formed in the post sealing block so that the pressurized polymer ball does not go beyond the other end of the lead film.

[0036] The secondary battery of the present invention has excellent sealing strength by including a first sealing portion and a second sealing portion. The other end of the second sealing portion extends in the opposite direction of the protrusion direction of the electrode lead compared to the other end of the first sealing portion, thereby ensuring sufficient sealing area of ​​the sealing portion. Such a secondary battery can effectively prevent internal electrolyte from leaking to the outside, while also sufficiently withstanding the internal gas pressure generated during use of the secondary battery, thereby resolving the venting issue of the secondary battery.

[0037] The secondary battery of the present invention can have high sealing strength by controlling the shape of the sealing portion, particularly the shape and position of the polymer balls inside the battery case, and the sealing device of the present invention is designed to be suitable for manufacturing the secondary battery while controlling the shape and position of the polymer balls in this way.

[0038] The sealing device of the present invention features an improved sealing block that enables the manufacture of secondary batteries with sufficient sealing strength even with short cycle times. Therefore, it can contribute to increasing the productivity of secondary batteries.

[0039] Using the sealing device of the present invention, sealing at temperatures high enough to damage the battery case surface is not necessary. Even when sealing at low temperatures, the dual sealing steps of main sealing and post sealing are applied, allowing secondary batteries manufactured using the device to have high sealing strength.

[0040] According to the sealing device of the present invention, the sealing portion profile can be improved, the degree of sealing portion fusion can be improved, and accordingly, the venting pressure of the secondary battery can be improved.

[0041] According to the sealing device of the present invention, the deviation between cells can be reduced during mass production of secondary batteries.

[0042] According to the sealing device of the present invention, by configuring the sealing device to include a main sealing block and a post sealing block, the sealing strength of the sealing portion can be increased. The position of the polymer ball within the sealing portion can be limited, enabling complete sealing. Therefore, the electrolyte inside the battery case can be effectively prevented from leaking to the outside, and the sealing strength and sealing reliability of the secondary battery can be improved.

[0043] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the contents of the invention described above, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0044] Figure 1 is a top view of a typical pouch-type secondary battery.

[0045] Figure 2 is a schematic diagram of a conventional sealing device.

[0046] Figure 3 is a top view of a secondary battery according to one embodiment of the present invention.

[0047] Figure 4 is a drawing showing an enlarged view of the dashed-dotted line area of ​​Figure 3.

[0048] FIG. 5 is a drawing showing an enlarged view of the dashed-dotted line area of ​​FIG. 3 according to another embodiment of the present invention.

[0049] Figure 6 is a cross-sectional view taken along line AA' of Figure 3.

[0050] Figure 7 is a photograph showing the appearance of a secondary battery according to an experimental example of the present invention.

[0051] Figure 8 is a cross-sectional photograph showing the shape of a sealing portion in a secondary battery according to an experimental example of the present invention.

[0052] Figure 9 is a schematic top view of a sealing device according to one embodiment of the present invention.

[0053] Fig. 10 is a drawing of the sealing device as viewed from direction B of Fig. 9.

[0054] Fig. 11 is a cross-sectional view taken along line C-C' of Fig. 9.

[0055] Fig. 12 is a cross-sectional view taken along line DD' of Fig. 9.

[0056] Fig. 13 is a perspective view of the main sealing block included in the sealing device of Fig. 9.

[0057] Fig. 14 is a perspective view of a post sealing block included in the sealing device of Fig. 9.

[0058] Fig. 15 is a modified example of the post sealing block illustrated in Fig. 14.

[0059] Figure 16 is a drawing of the upper post sealing block as viewed from the E direction of Figure 15.

[0060] Fig. 17 is a cross-sectional view of the sealing step by the post sealing block of Fig. 14.

[0061] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms. These embodiments are provided solely to ensure complete disclosure of the present invention and to fully inform those skilled in the art of the scope of the invention.

[0062] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will appreciate that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to facilitate understanding of various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated relative to other elements. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may often not be depicted so as not to obscure the spirit of various embodiments of the present invention.

[0063] Figure 3 is a top view of a secondary battery according to one embodiment of the present invention.

[0064] Referring to FIG. 3, a secondary battery (100) includes an electrode assembly (110) and a battery case (200). The electrode assembly (110) has an electrode lead (300) protruding therefrom. The battery case (200) includes a sealing portion (250) in which the electrode assembly (110) is built and whose outer periphery is sealed. In addition, there is a lead film (400) positioned at a portion corresponding to the sealing portion (250) on at least one of the upper and lower portions of the electrode lead (300).

[0065] And, the sealing portion (250) includes a first sealing portion (260) on the electrode lead (300) side of the battery case (200), and a second sealing portion (270) on the electrode lead (300) side of the battery case (200). In the illustrated example, the electrode leads (300) on both sides protrude in opposite directions. Meanwhile, depending on the type of secondary battery, the electrode leads (300) may protrude only in one direction parallel to each other rather than in opposite directions.

[0066] The electrode assembly (110) can be mounted in the storage portion (210) of the battery case (200). The electrode lead (300) is electrically connected to the electrode tab (150) included in the electrode assembly (110) and can protrude outwardly from the battery case (200) via the sealing portion (250).

[0067] According to one embodiment, the lead film (400) is included on both the upper and lower portions of the electrode lead (300). In the illustrated example, the lead film (400) includes one end (400_o) and the other end (400_i) in the protruding direction (X-axis direction) of the left electrode lead (300). The lead film (400) is positioned on the upper and lower portions of the electrode lead (300) to ensure sealing with the battery case (200).

[0068] In the illustrated example, the secondary battery (100) may be a roughly rectangular plate-shaped cell having a long side in the direction along the X-axis, a short side in the direction along the Y-axis, and a thickness in the Z-axis direction that is smaller than the length of the X-axis or Y-axis. An electrode lead (300) may be formed on the short side of the secondary battery (100). This secondary battery (100) has an efficient structure for increasing energy density by stacking multiple batteries face-to-face by integrating them in the Z-axis direction.

[0069] The battery case (200) may be a laminate sheet including a resin layer and a metal layer. In one embodiment, the battery case (200) may be made of a laminate sheet and may be composed of an outer resin layer forming the outermost layer, a barrier metal layer preventing penetration of materials, and an inner resin layer for sealing.

[0070] The outer resin layer must prevent scratches and corrosion of the barrier metal layer and have excellent resistance to external environments, and therefore requires a tensile strength and weather resistance above a certain level. In this regard, the outer resin layer may include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or stretched nylon. The outer resin layer may be positioned in close proximity to the barrier metal layer, and an adhesive layer may be interposed between the outer resin layer and the barrier metal layer. The above-mentioned barrier metal layer is not particularly limited in type as long as it is a flexible metal film. In addition to the function of preventing the inflow of foreign substances such as gas and moisture or leakage of electrolyte, it can also have the function of improving the strength of the battery case (200). For example, aluminum (Al) or an aluminum alloy can be used. Examples of the aluminum alloy include alloy numbers 8079, 1N30, 8021, 3003, 3004, 3005, 3104, 3105, etc., and these can be used alone or in combination of two or more. The inner resin layer can be made of a polymer resin that has heat-sealability, low hygroscopicity with respect to the electrolyte, and does not expand or corrode due to the electrolyte, and can be made of PP, more specifically, non-stretched polypropylene (CPP). The inner resin layer is positioned close to the barrier metal layer. Considering each function, the outer resin layer, the barrier metal layer, and the inner resin layer have a thickness of several tens to several hundred μm.

[0071] The electrode assembly (110) may be configured in a jelly-roll type (rolled type), stack type (laminated type), or composite type (stack / folded type) structure. For example, the electrode assembly (110) may include a positive electrode, a negative electrode, and a separator disposed therebetween.

[0072] The electrode lead (300) is electrically connected to the electrode tabs (150) drawn out from the positive and negative electrodes included in the electrode assembly (110), and protrudes outwardly from the battery case (200) via the sealing portion (250). In addition, the lead film (400) is positioned at a portion corresponding to the sealing portion (250) on at least one of the upper and lower portions of the electrode lead (300). Accordingly, the lead film (400) can prevent a short circuit from occurring in the electrode lead (300) when heat-sealed together with the sealing portion (250), while also improving the sealing property of the sealing portion (250) and the electrode lead (300). The lead film (400) may be made of polypropylene (PP).

[0073] Referring to FIG. 3, the lead film (400) may have a wider width (length) in the Y-axis direction than the electrode lead (300). Here, the width of the lead film (400) refers to the maximum value of the distance from one end of the lead film (400) to the other end in the direction (Y-axis direction) orthogonal to the protrusion direction of the electrode lead (300), and the width of the electrode lead (300) refers to the maximum value of the distance from one end of the electrode lead (300) to the other end in the direction orthogonal to the protrusion direction of the electrode lead (300). Accordingly, since the width of the lead film (400) is greater than that of the electrode lead (300), the side surface of the electrode lead (300) can be prevented from being exposed to the outside.

[0074] The lead film (400) may have a length greater than the width of the sealing portion (250) and a length less than the length of the electrode lead (300) based on the protruding direction of the electrode lead (300). Here, the length of the lead film (400) refers to the maximum value of the distance between one end (400_o) and the other end (400_i) of the lead film (400) in the protruding direction of the electrode lead (300). The width of the sealing portion (250) refers to the maximum value of the distance from one end to the other end of the sealing portion (250) in the protruding direction of the electrode lead (300). The length of the electrode lead (300) refers to the maximum value of the distance from one end to the other end of the electrode lead (300) in the protruding direction of the electrode lead (300). Accordingly, the lead film (400) can enable sealing between the electrode lead (300) and the battery case (200) without interfering with the electrical connection of the electrode lead (300).

[0075] Figure 4 is a drawing showing an enlarged view of the dashed-dotted line area of ​​Figure 3.

[0076] Referring to Fig. 4, the sealing portion (250) includes a first sealing portion (260) and a second sealing portion (270). The lead film (400) is positioned at a portion corresponding to the first sealing portion (260) and the second sealing portion (270).

[0077] In this specification, the first sealing portion (260) and the second sealing portion (270) refer to an area to be sealed or an area that has been sealed in the secondary battery (100). In the illustrated example, the first sealing portion (260) and the second sealing portion (270) may have an area that overlaps with each other. In addition, the first sealing portion (260) and the second sealing portion (270) refer to an area that is sealed by applying heat and pressure to the overlapping area of ​​the electrode lead (300), the lead film (400), and the battery case (200) through a sealing device to melt the inner resin layer of the battery case (200) and the lead film (400), and then solidifying them. In addition, the first sealing portion (260) refers to a portion that is pressed by the main sealing block (600) of the sealing device (500) described later, and the second sealing portion (270) refers to a portion that is pressed by the post sealing block (700) of the sealing device (500) described later. When observing the secondary battery (100) from the outside, the presence of the first sealing portion (260) and the second sealing portion (270) can be visually confirmed by checking the pressed marks. However, the pressed marks do not exactly represent the shapes of the first sealing portion (260) and the second sealing portion (270). Inside the actual battery case (200), the inner resin layer of the battery case (200) and the lead film (400) are melted and sealed by the pressure of the main sealing block (600) and the post sealing block (700), but the pressed marks observed outside the secondary battery (100) may vary depending on the shape of the part where the main sealing block (600) contacts the battery case (200) and the shape of the part where the post sealing block (700) contacts the battery case (200).

[0078] The first sealing portion (260) includes one end (260_o) and the other end (260_i) in the protruding direction of the electrode lead (300), and the second sealing portion (270) includes one end (270_o) and the other end (270_i) in the protruding direction of the electrode lead (300). Here, the other end (270_i) of the second sealing portion (270) extends further in the opposite direction of the protruding direction of the electrode lead (300) than the other end (260_i) of the first sealing portion (260). Among the sealing portions (250), the first sealing portion (260) can be said to be closer to the outside of the rim of the battery case (200), and the second sealing portion (270) can be said to be closer to the receiving portion (210) of the battery case (200) than the first sealing portion (260).

[0079] The secondary battery (100) of the present invention has excellent sealing strength as it includes a first sealing portion (260) and a second sealing portion (270). The sealing strength can be evaluated by measuring the strength at the time of peeling when peeling the electrode cases (200) on both sides, located above and below the sealing portion (250).

[0080] The other end (270_i) of the second sealing portion (270) extends in the opposite direction of the protrusion direction of the electrode lead (300) compared to the other end (260_i) of the first sealing portion (260), thereby ensuring a sufficient sealing area of ​​the sealing portion (250). Such a secondary battery (100) can effectively prevent the electrolyte inside from leaking to the outside, and can also sufficiently withstand the internal gas pressure generated inside the secondary battery (100) during use, thereby solving the venting issue of the secondary battery.

[0081] The length (L1) of the first sealing portion (260) may be longer than the length (L2) of the second sealing portion (270). Here, the length (L1) of the first sealing portion (260) refers to the maximum value of the distance from one end of the first sealing portion (260) to the other end in a direction perpendicular to the protrusion direction of the electrode lead (300), and the length (L2) of the second sealing portion (270) refers to the maximum value of the distance from one end of the first sealing portion (260) to the other end in a direction perpendicular to the protrusion direction of the electrode lead (300). The first sealing portion (260) seals the outer periphery of the battery case (200) on the electrode lead (300) side. The second sealing portion (260) is positioned further toward the electrode assembly (110) than the first sealing portion (260) and additionally seals the periphery of the electrode lead (300).

[0082] The width (W1) of the first sealing portion (260) and the width (W2) of the second sealing portion (270) may be set to conditions that can prevent moisture from penetrating into the battery case (200) for a long period of time. As a non-limiting example, the width (W1) of the first sealing portion (260) and the width (W2) of the second sealing portion (270) may each be 2 mm to 10 mm. The width of the portion where the first sealing portion (260) and the second sealing portion (270) overlap may be 1 mm to 9 mm.

[0083] According to one embodiment, the width (W2) of the second sealing portion (270) may be greater than the width (W1) of the first sealing portion (260). The width (W2) of the second sealing portion (270) refers to the maximum value of the distance between one end (270_o) and the other end (270_i) of the second sealing portion (270) in the protruding direction of the electrode lead (300). The width (W1) of the first sealing portion (260) refers to the maximum value of the distance between one end (260_o) and the other end (260_i) of the first sealing portion (260) in the protruding direction of the electrode lead (300).

[0084] The first sealing portion (260) and the second sealing portion (270) overlap at least partially in the protruding direction of the electrode lead (300). As the number of sealing times for the same portion increases, the sealing strength may increase. When the first sealing portion (260) and the second sealing portion (270) overlap, the sealing strength of the sealing portion (250) of the overlapping portion may increase. Accordingly, the resistance to venting pressure when gas generated within the secondary battery (100) is discharged to the outside may also be increased, and safety may also be further improved.

[0085] If the entire edge portion of the battery case (200) is fused in the width direction to form the sealing portion (250), a problem may occur in which the resin layer inside the battery case (200) melts due to heat and the melted resin layer leaks out along the contact surface of the battery case (200). To prevent this problem, an unsealed portion (250') with a width of approximately 2 mm or less may be left on the outermost edge portion of the battery case (200), and the sealing portion (250) may be formed only on the edge portion of the battery case (200) located more inward than this.

[0086] In Fig. 4, one end (270_o) of the second sealing portion (270) and one end (260_o) of the first sealing portion (260) are positioned on the same line. In this case, the overlap between the first sealing portion (260) and the second sealing portion (270) can be maximized, so that the sealing strength of the sealing portion (250) can be further increased.

[0087] In the modified example of FIG. 5, one end (270_o) of the second sealing portion (270) is spaced apart from one end (260_o) of the first sealing portion (260) in the opposite direction of the protrusion of the electrode lead (300). In this case, when forming the second sealing portion (270) after forming the first sealing portion (260), there is no need to align one end (270_o) of the second sealing portion (270) and one end (260_o) of the first sealing portion (260), so that a process margin can be secured in a method of forming the first sealing portion (260) first and then sequentially forming the second sealing portion (270), and, if the resin layer inside the battery case (200) is melted by heat during the formation of the second sealing portion (260), it can be prevented from leaking to the outside along the contact surface of the battery case (200) beyond one end (260_o) of the first sealing portion (260).

[0088] The first sealing portion (260) and the second sealing portion (270) may overlap. The width (W2) of the second sealing portion (270) may be larger than the width (W1) of the first sealing portion (260), so that the other end (270_i) of the second sealing portion (270) may extend in the opposite direction of the protrusion direction of the electrode lead (300) than the other end (260_i) of the first sealing portion (260). According to one embodiment, the width (W1) of the first sealing portion (260) and the width (W2) of the second sealing portion (270) are the same, or the width (W1) of the first sealing portion (260) is greater than the width (W2) of the second sealing portion (270), and the degree of overlap between the first sealing portion (260) and the second sealing portion (270) can be adjusted so that the other end (270_i) of the second sealing portion (270) extends in the opposite direction of the protrusion direction of the electrode lead (300) than the other end (260_i) of the first sealing portion (260).

[0089] Figure 6 is a cross-sectional view taken along line AA' of Figure 3.

[0090] Referring to FIG. 6, a polymer ball (PB) is formed by the fused resin between the battery case (200) and the lead film (400) inside the second sealing portion (270), and is formed so that the polymer ball (PB) does not go beyond the other end (400_i) of the lead film (400). The polymer ball (PB) is described below. Here, the inside of the second sealing portion (270) refers to the direction from the outer resin layer of the battery case (200) toward the inner resin layer, and refers to a portion adjacent to the inner resin layer.

[0091] As mentioned above, the battery case (200) may be composed of an outer resin layer forming the outermost shell, a barrier metal layer preventing penetration of materials, and an inner resin layer for sealing. When the battery case (200) includes the inner resin layer in this way, when the sealing portion (250) is formed by heat-sealing the edge of the battery case (200), when the battery case (200) is heated and pressurized, the inner resin layer of the battery case (200) and the resin of the lead film (400) melt, and a portion where the resin melts and clumps is formed between the inner surfaces of the battery case (200) and the lead film (400), which is called a polymer ball (PB). When the polymer ball (PB) is formed appropriately, the sealing strength increases, the sealing power increases, and venting does not occur even at high internal pressure.

[0092] In particular, in the present invention, the polymer ball (PB) is formed so as not to go beyond the other end (400_i) of the lead film (400), so that the sealing force can be improved so that venting or explosion is not caused even under high pressure. If the polymer ball (PB) goes beyond the other end (400_i) of the lead film (400) and flows further into the interior of the secondary battery (100), a venting issue may occur. If the polymer ball (PB) is positioned beyond the other end (400_i) of the lead film (400), there is a concern that high-pressure gas may concentrate in the space between the polymer ball (PB) and the battery case (200) during venting. If the polymer ball (PB) is torn because it cannot withstand the high-pressure gas, the lead film (400) will also be torn together with the polymer ball (PB), and the sealing portion of the lead film (400) will be permanently damaged. According to the present invention, the venting pressure can be improved by ensuring that the polymer ball (PB) is better fused and is not positioned beyond the other end (400_i) of the lead film (400), thereby preventing the polymer ball (PB) from being torn.

[0093] According to the present invention, a secondary battery (100) having high sealing strength can be provided by controlling the shape of the sealing portion (250), particularly the shape and position of the polymer ball (PB) inside the battery case (200). According to the present invention, the profile of the sealing portion (250) can be improved by controlling the shape of the polymer ball (PB), and the degree of fusion of the sealing portion (250) can be improved by including the first sealing portion (260) and the second sealing portion (270), and the venting internal pressure can be improved.

[0094] As a non-limiting example, the sealing thickness (d1) of the first sealing portion (260) may be 800 µm to 1300 µm. The sealing thickness (d2) of the overlapping portion of the first sealing portion (260) and the second sealing portion (270) may be 700 µm to 1250 µm. Here, the sealing thickness is the total thickness in the cross-section of the sealing portion (along the Z-axis direction) after sealing. For example, the sealing thickness is the combined thickness of the battery case (200), the lead film (400), and the electrode lead (300). By forming the second sealing portion (270) that at least partially overlaps the first sealing portion (260), the sealing thickness can be further reduced, which can lead to an increase in sealing strength.

[0095] Fig. 7 is a photograph showing the appearance of a secondary battery according to an experimental example of the present invention. It is a photograph taken from the top of a portion of the secondary battery (100) where the electrode lead (300) and the lead film (400) are located, and is, for example, a photograph of a portion corresponding to the dashed-dotted line area of ​​Fig. 3. Referring to Fig. 7, in the battery (100) according to one embodiment, a pressed mark (260a) is visible in a portion corresponding to the first sealing portion (260) and a pressed mark (260b) is visible in a portion corresponding to the second sealing portion (270), and it can be confirmed that the first sealing portion (260) and the second sealing portion (270) overlap. A pressed mark (260b) of the battery case (200) is confirmed in the overlapping portion of the first sealing portion (260) and the second sealing portion (270). As described below, the post sealing block (700) forming the second sealing portion (270) has a structure in which the first pressing portion (710) and the second pressing portion (720) form a step with respect to each other. Accordingly, as a result of the battery case (200) being pressed more by the first pressing portion (710) than by the second pressing portion (720), a mark (260b) remains due to the difference in the degree of pressing in a portion corresponding to the step between the first pressing portion (710) and the second pressing portion (720). The pressed marks (260a, 260b) do not directly represent the shapes of the first sealing portion (260) and the second sealing portion (270). For reference, the position of the polymer ball (PB) is shown in FIG. 7. The polymer ball (PB) is formed so as not to exceed the right boundary portion (400_i) of the lead film (400).

[0096] Fig. 8 is a cross-sectional photograph showing the shape of a sealing portion in a secondary battery according to an experimental example of the present invention. It is a photograph of a cross-section cut in the Z-axis direction through a portion of a secondary battery (100) where an electrode lead (300) and a lead film (400) are present, and is a photograph of a portion corresponding to an area including cross-sections of the first sealing portion (260) and the second sealing portion (270) in Fig. 6, for example. Referring to Fig. 8, it can be confirmed that the polymer ball (PB) is not only properly formed, but also formed so as not to protrude from the other end (400_i) of the lead film (400). The polymer ball (PB) is formed so as not to protrude from the other end (400_i) of the lead film (400). If the sealing is performed with excessively strong pressure, the electrode lead (300) may protrude convexly in the opposite direction of the protrusion, and the polymer ball (PB) may protrude beyond the other end (400_i) of the lead film (400) and into the sealing portion (250). Then, as described above, there is a risk that the polymer ball (PB) may be peeled off together with the lead film (400) when the internal gas pressure increases. In the present invention, when the second sealing portion (270) is formed, the polymer ball (PB) may be formed without being excessively pressed and without protruding from the other end (400_i) of the lead film (400).

[0097] According to one embodiment, the cross-section of the polymer ball (PB) may be formed concavely in the protruding direction of the electrode lead (300). Since the polymer ball (PB) is formed from a resin mainly supplied from the inner resin layer of the battery case (200), if sealed under appropriate sealing conditions, it may have a concave cross-sectional shape between the battery case (200) and the lead film (400), as illustrated in FIG. 8. If the sealing is performed with excessively strong pressure, the polymer ball may come out convexly in the opposite direction of the protruding direction of the electrode lead (300), and if excessive, it may come out beyond the other end (400_i) of the lead film (400) and into the sealing portion (250), which is not preferable.

[0098] According to one embodiment of the present invention, a plurality of secondary batteries (100) may be integrated to form a battery module or battery pack. Such battery modules or battery packs may be applied to various devices. These devices may include means of transportation such as electric bicycles, electric vehicles, and hybrid vehicles. However, the present invention is not limited thereto and may be applied to various devices that utilize battery modules or battery packs.

[0099] The secondary battery (100) of the present invention can have high sealing strength by controlling the shape of the sealing portion (250), particularly the shape and position of the polymer ball (PB) inside the battery case (200), and the sealing device proposed in the present invention is designed to be suitable for manufacturing the secondary battery (100) while controlling the shape and position of the polymer ball (PB) in this way. Hereinafter, a sealing device according to one embodiment of the present invention will be described.

[0100] Fig. 9 is a schematic top view of a sealing device according to one embodiment of the present invention. Fig. 10 is a drawing of the sealing device as seen from direction B of Fig. 9. Fig. 11 is a cross-sectional view taken along line C-C' of Fig. 9. Fig. 12 is a cross-sectional view taken along line DD' of Fig. 9. Fig. 13 is a perspective view of a main sealing block included in the sealing device of Fig. 9. Fig. 14 is a perspective view of a post sealing block included in the sealing device of Fig. 9.

[0101] Referring to FIGS. 9 to 14, a sealing device (500) according to one embodiment of the present invention is a sealing device capable of manufacturing a secondary battery (100) according to one embodiment of the present invention described with reference to FIGS. 3 to 6. In other words, the sealing device (500) is a sealing device for a secondary battery (100) for sealing a battery case (200) in which an electrode assembly (110) with a protruding electrode lead (300) is built.

[0102] The sealing device (500) includes a main sealing block (600) and a post sealing block (700). Since it is difficult to supply sufficient heat at once in a short period of time when sealing a battery case (200), the sealing method is improved so that additional secondary sealing can be performed in the form of a post sealing after sealing by the main sealing block (600), and the sealing device (500) is configured to further include a post sealing block (700) for this additional secondary sealing.

[0103] First, the main sealing block (600) is configured so that two bar-type bars can thermally compress the upper and lower portions of the battery case (200). The main sealing block (600) includes an upper sealing block (600a) and a lower sealing block (600b), and the upper sealing block (600a) and the lower sealing block (600b) can be arranged to face each other. The upper sealing block (600a) can apply pressure from the upper portion to the lower portion of the first sealing portion (260) on the electrode lead (300) side of the battery case (200). The lower sealing block (600b) can apply pressure from the lower portion to the upper portion of the first sealing portion (260). This main sealing block (600) can generate heat by a heating means (not shown) built in therein to heat and pressurize the first sealing portion (260). The main sealing block (600) is installed so as to be able to be raised and lowered. Here, the raising and lowering means may be provided by a cylinder or the like, which is generally widely used, but is not necessarily limited thereto, and includes all means that enable the upper sealing block (600a) and the lower sealing block (600b) to be raised and lowered.

[0104] The post sealing block (700) is also configured so that two bar-shaped bars can thermally compress the upper and lower portions of the battery case (200). The post sealing block (700) includes an upper sealing block (700a) that applies pressure downward from the upper portion of the second sealing portion (270) on the electrode lead (300) side of the battery case (200) and a lower sealing block (700b) that applies pressure upward from the lower portion of the second sealing portion (270). The post sealing block (700) generates heat by a heating means (not shown) built into it to heat the second sealing portion (270). The upper sealing block (700a) and the lower sealing block (700b) of the post sealing block (700) can also be arranged so as to face each other. The post sealing block (700) is also installed so as to be able to rise and fall. Here, the lifting means may be provided as a cylinder or the like, which is generally widely used, and is not necessarily limited thereto, and includes all means that enable the upper sealing block (700a) and the lower sealing block (700b) to be raised and lowered.

[0105] Here, the heating means is configured to heat the first sealing portion (260) of the battery case (200) when sealing by the main sealing block (600) and to heat the second sealing portion (270) of the battery case (200) when sealing by the post sealing block (700) to heat and melt the resin layer on the inner surface of the battery case (200), and various configurations are possible. For example, the heating means may be a method of injecting high-temperature fluid into the internal space of the main sealing block (600) and the post sealing block (700). Another example may be a method of generating heat by a heating wire embedded in the main sealing block (600) and the post sealing block (700).

[0106] The post sealing block (700) may be arranged on one side of the main sealing block (600). That is, the upper sealing block (700a) of the post sealing block (700) may be arranged on one side of the upper sealing block (600a) of the main sealing block (600), and the lower sealing block (700b) of the post sealing block (700) may be arranged on one side of the lower sealing block (600b) of the main sealing block (600). The main sealing block (600) and the post sealing block (700) may be arranged along the working direction (MD).

[0107] The main sealing block (600) and the post sealing block (700) may be made of, for example, a metal material. The metal material has excellent thermal conductivity and is advantageous for heating the battery case (200). The main sealing block (600) and the post sealing block (700) have a geometric structure corresponding to the width and length of the desired sealing portion, and the material may be made of copper, stainless steel, steel, or the like, which have excellent thermal conductivity.

[0108] Here, as described above, the shapes of the main sealing block (600) and the post sealing block (700) are configured differently so that the other end (270_i) of the second sealing portion (270) of the secondary battery (100) extends in the opposite direction of the protrusion direction of the electrode lead (300) than the other end (260_i) of the first sealing portion (260).

[0109] The secondary battery (100) as an example has electrode leads (300) protruding in both directions. In order to further reduce the tact time, the main sealing block (600) and the post sealing block (700) may be arranged in two rows as shown in Fig. 9, so that they may approach the electrode leads (300) protruding in both directions, respectively, so that sealing can be performed simultaneously on both sides. If the electrode leads (300) protrude in only one direction, the main sealing block (600) and the post sealing block (700) may be arranged in only one row.

[0110] Meanwhile, referring to FIG. 10 and FIG. 13, the main sealing block (600) may include a concave portion (620) corresponding to the electrode lead (300) side including the lead film (400) on the lower surface of the upper sealing block (600a) and the upper surface of the lower sealing block (600b), respectively.

[0111] The lower surface of the upper sealing block (600a) of the main sealing block (600) and the upper surface of the lower sealing block (600b) include a peripheral pressing portion (610) that pressurizes the battery case (200), and the concave portion (620) can pressurize the electrode lead (300) and the lead film (400).

[0112] The concave portion (620) corresponds to the sealing portion on the electrode lead (300) side. The concave portion (620) may include an electrode lead pressing portion (640) that pressurizes the electrode lead (300) and an intermediate pressing portion (630) that connects the electrode lead pressing portion (640) and the peripheral pressing portion (610) in a step-like manner. The intermediate pressing portion (630) may be rectangular or diagonal.

[0113] According to one embodiment, in the main sealing block (600), the peripheral pressing portion (610) is a portion for sealing a portion of the battery case (200) where the lead film (400) and the electrode lead (300) do not exist. The intermediate pressing portion (630) is a portion for sealing a portion of the battery case (200) where only the lead film (400) exists. The electrode lead pressing portion (640) is a portion for sealing a portion of the battery case (200) where the electrode lead (300) exists, i.e., an overlapping portion of the electrode lead (300), the lead film (400), and the battery case (200). In this way, the main sealing block (600) may have three steps. By providing such steps, the degree of pressing can be adjusted for each position. Accordingly, the sealing pressure and the sealing strength accordingly can be adjusted for each position. Accordingly, the sealing can be securely performed without any empty space between the lead film (400) and the electrode lead (300).

[0114] In one embodiment, the upper sealing block (600a) and the lower sealing block (600b) of the main sealing block (600) are not a combination of separate structures with steps, but rather an integral structure, i.e., a single mass. Accordingly, the main sealing block (600) is easy to manufacture and process, and is easy to maintain.

[0115] As in the present embodiment, if the concave portion (620) is formed, the precision of the positioning of the electrode lead (300) and the lead film (400) within the concave portion (620) can be increased, and the gap between the lead film (400) and the concave portion (620) can be made almost non-existent, thereby further increasing the sealing reliability. Accordingly, the sealing property of the battery case (200) around the electrode lead (300) can be significantly improved. The sealing property of the secondary battery (100) can be increased by ensuring that the electrode lead (300), the lead film (400), and the battery case (200) are in closer contact, and at this time, the unsealed area can be significantly reduced.

[0116] In the case of high-capacity, high-output, medium-to-large-sized secondary batteries, the demand for which has been rapidly increasing recently, the thickness of the electrode lead (300) is increasing according to the size of the unit cell and capacity included. Therefore, even if the size of the electrode lead (300) increases, the non-sealing area that is not pressed by the main sealing block (600) does not increase, and sealing can be performed smoothly. In addition, since the positioning is accurate regardless of the thickness of the electrode lead (300), sealing reliability can be guaranteed.

[0117] The length (L3) of the main sealing block (600) may be longer than the width of the electrode lead (300) including the lead film (400) and may extend to the surrounding battery case (200). Here, the length (L3) of the main sealing block (600) means the maximum value of the distance from one end of the main sealing block (600) to the other end in a direction perpendicular to the protrusion direction of the electrode lead (300), and may correspond to the dimension L1 in the longitudinal direction of the first sealing portion (260) of FIG. 4.

[0118] Referring to FIG. 10, the length (L4) of the post sealing block (700) may be shorter than the length (L3) of the main sealing block (600). Here, the length (L4) of the post sealing block (700) means the maximum value of the distance from one end of the post sealing block (700) to the other end in a direction perpendicular to the protrusion direction of the electrode lead (300), and may correspond to the dimension L2 in the longitudinal direction of the second sealing portion (270) of FIG. 4.

[0119] According to one embodiment, the length (L4) of the post sealing block (700) may be flexible depending on the length (L2) of the second sealing portion (270), but may be, for example, 30 mm to 100 mm.

[0120] As shown in FIGS. 10 and 12 to 14, the upper sealing block (600a) and the lower sealing block (600b) of the main sealing block (600) have steps formed from the top to the bottom. On the other hand, the upper sealing block (700a) and the lower sealing block (700b) of the post sealing block (700) have steps formed in opposite directions of the protrusion of the electrode lead (300). Here, the steps can be formed so that the pressing surfaces do not form a parallel plane with each other but have a height difference. By providing a step, the degree of pressing can be adjusted for each position.

[0121] Referring to FIGS. 12 and 14, the post sealing block (700) may include a first pressing portion (710) that presses the battery case (200) in a portion overlapping the first sealing portion (260) and a second pressing portion (720) that presses the battery case (200) in a portion opposite to the protrusion direction of the electrode lead (300) from the first pressing portion (710).

[0122] According to one embodiment, the width (W-710) of the first pressurizing portion (710) may be flexible, for example, from 2 mm to 6 mm, depending on the width of the sealing portion (250), for example, the width (W2) of the second sealing portion (270).

[0123] As will be described later, the post sealing block (700) additionally presses the polymer ball (PB) generated when forming the first sealing portion (260) with the main sealing block (600). The width (W-720) of the second pressurizing portion (720) can be flexibly determined depending on the degree of spreading of the polymer ball (PB). For example, the width (W-720) of the second pressurizing portion (720) can be 1 mm to 4 mm.

[0124] As another example, the width (W-720) of the second pressurizing portion (720) may not exceed 50% of the width (W-710) of the first pressurizing portion (710). For example, the width (W-710) of the first pressurizing portion (710) may be 4 mm and the width (W-720) of the second pressurizing portion (720) may be 2 mm. Here, the width (W-720) of the second pressurizing portion (720) and the width (W-710) of the first pressurizing portion (710) indicate the dimensions in the protruding direction of the electrode lead (300). When these conditions are satisfied between the width (W-720) of the second pressurizing portion (720) and the width (W-710) of the first pressurizing portion (710), the shape and position of the polymer ball (PB) can be effectively controlled.

[0125] According to one embodiment, the second pressurizing portion (720) protrudes in a direction opposite to the protrusion direction of the electrode lead (300) in a direction perpendicular to the first pressurizing portion (710). In the present embodiment, the first pressurizing portion (710) has a first pressurizing surface (710a) whose pressurizing surface in contact with the battery case (200) is a single plane. The second pressurizing portion (720) has a second pressurizing surface (720a) whose pressurizing surface in contact with the battery case (200) is a single plane.

[0126] The first pressurizing portion (710) may protrude further toward the electrode lead (300) than the second pressurizing portion (720). In other words, the first pressurizing surface (710a) may be positioned closer to the electrode lead (300) than the second pressurizing surface (720a). The height difference (H) between the first pressurizing portion (710) and the second pressurizing portion (720) may be 0.1 mm to 5 mm. Here, the height difference (H) may be the distance between the first pressurizing surface (710a) and the second pressurizing surface (720a). This height difference (H) may be determined depending on the thickness and pressing force of the polymer ball (PB).

[0127] In this way, by the first pressing portion (710) and the second pressing portion (720) having a height difference (H), the post sealing block (700) forms a step in the opposite direction of the protrusion direction of the electrode lead (300). In particular, by this step, the pressing force of the first pressing surface (710a) is greater than the pressing force of the second pressing surface (720a). By providing a step like this, the degree of pressing can be adjusted for each position.

[0128] Since the first pressurizing portion (710) and the second pressurizing portion (720) have a structure in which they form a step with respect to each other, the gap between the first pressurizing surface (710a) of the upper sealing block (700a) of the post sealing block (700) and the first pressurizing surface (710a) of the lower sealing block (700b) can be smaller than the gap between the second pressurizing surface (720a) of the upper sealing block (700a) of the post sealing block (700) and the second pressurizing surface (720a) of the lower sealing block (700b). When the upper sealing block (700a) and the lower sealing block (700b) press the edge of the battery case (200) in both the up and down directions, a greater pressure is applied to the portion between the first pressing surface (710a) of the upper sealing block (700a) and the first pressing surface (710a) of the lower sealing block (700b), which have a smaller gap. That is, even if the upper sealing block (700a) and the lower sealing block (700b) are pressed against the battery case (200) with the same pressure, a difference occurs in the pressure actually applied through the first pressing portion (710) and the second pressing portion (720).

[0129] In the present embodiment, a relatively relaxed pressure can be applied to the second pressurizing portion (720) compared to the first pressurizing portion (710). Accordingly, the sealing portion by the first pressurizing portion (710) can be firmly thermally sealed, thereby strongly sealing the battery case (200). On the other hand, the sealing portion by the second pressurizing portion (720) can be sealed with a relatively relaxed thermal seal.

[0130] When the first sealing portion (260) is formed with the main sealing block (600), a polymer ball (PB) can be formed inside the battery case (200). The post sealing block (700) presses the previously formed polymer ball (PB) while additionally applying heat, so that when the second sealing portion (270) is formed with the post sealing block (700), a stronger seal can be achieved.

[0131] The second pressurizing portion (720) can press the polymer ball (PB) relatively weakly compared to the first pressurizing portion (710). In this way, if the post sealing block (700) is configured with a step structure, the polymer ball (PB) can be additionally pressed to help the fusion between the resin of the battery case (200) and the resin of the lead film (400) to be better, thereby increasing the sealing strength. At the same time, the polymer ball (PB) is not pressed too hard, so that the polymer ball (PB) can be formed so that it does not come off the other end (400_i) of the lead film (400), as described with reference to FIG. 6.

[0132] The upper sealing block (700a) and the lower sealing block (700b) of the post sealing block (700) are not separate components with steps, but rather are an integral structure, i.e., a single mass. Accordingly, the post sealing block (700) is easy to manufacture and process, and is easy to maintain.

[0133] Fig. 15 is a modified example of the post sealing block illustrated in Fig. 14. Fig. 16 is a drawing of the upper post sealing block as viewed from the E direction of Fig. 15.

[0134] Referring to FIGS. 15 and 16, unlike the post sealing block (700) illustrated in FIG. 14, the post sealing block (700) according to the present embodiment has a structure in which the first pressurizing portion (710) also forms a step.

[0135] Referring to FIGS. 15 and 16, the first pressurizing portion (710) may include a peripheral pressurizing portion (712) that pressurizes the battery case (200), an electrode lead pressurizing portion (716) that pressurizes the electrode lead (300), and an intermediate pressurizing portion (714) that connects the electrode lead pressurizing portion (716) and the peripheral pressurizing portion (712) in a step-like manner. A step may be formed between the peripheral pressurizing portion (712), the intermediate pressurizing portion (714), and the electrode lead pressurizing portion (716) to make the sealing pressure different. In the secondary battery (100) described above, the second sealing portion (270) overlaps the first sealing portion (260), and the other end (270_i) of the second sealing portion (270) extends in the opposite direction of the protrusion direction of the electrode lead (300) than the other end (260_i) of the first sealing portion (260). The shapes of the main sealing block (600) and the post sealing block (700) of the sealing device (500) are designed so as to form the first sealing portion (260) and the second sealing portion (270). The second sealing portion (270) can be said to extend further inward of the battery case (200) (opposite to the protrusion direction of the electrode lead (300)) than the first sealing portion (260). Therefore, the post sealing block (700) can be said to be formed so as to seal by pressurizing and heating a portion of the inside of the battery case (200) more than the main sealing block (600).

[0136] Referring back to FIG. 9, a conveyor belt (800) may be configured between the upper sealing block (600a) and the lower sealing block (600b) of the main sealing block (600) and between the upper sealing block (700a) and the lower sealing block (700b) of the post sealing block (700) so that the secondary battery (100) can be transported along the MD direction. The secondary battery (100) is supported on the conveyor belt (800) such that the electrode lead (300) portion is positioned outside the conveyor belt (800), and can be transported from the main sealing block (600) to the post sealing block (700) according to the movement of the conveyor belt (800). Since the primary sealing by the main sealing block (600) and the secondary sealing by the post sealing block (700) are performed within one sealing device (500), the tact time can be significantly reduced.

[0137] A sealing method using such a sealing device (500) may be as follows.

[0138] A secondary battery (100) for sealing is placed on a moving conveyor belt (800). When the secondary battery (100) is positioned between the upper sealing block (600a) and the lower sealing block (600b) of the main sealing block (600) by the movement of the conveyor belt (800), the upper sealing block (600a) descends and the lower sealing block (600b) rises, thereby sealing the secondary battery (100) by contacting the battery case (200), and thereby the first sealing portion (260) of the secondary battery (100) can be formed first.

[0139] The secondary battery (100) illustrated as positioned in the main sealing block (600) portion of Fig. 9 represents a state after the first sealing, and is briefly illustrated as a shape including the first sealing portion (260). At this time, the fused resin between the battery case (200) and the lead film (400) is pushed into the first sealing portion (260) by the main sealing block (600), so that a polymer ball (PB) can be initially formed.

[0140] After the first sealing portion (260) is formed, the upper sealing block (600a) rises and the lower sealing block (600b) descends, moving away from the secondary battery (100). The secondary battery (100) loaded on the conveyor belt (800) is positioned between the upper sealing block (700a) and the lower sealing block (700b) of the post sealing block (700) located next to it due to the moving conveyor belt (800). Then, the upper sealing block (700a) descends and the lower sealing block (700b) rises, thereby making contact with the battery case (200) to perform a second sealing of the secondary battery (100), through which the second sealing portion (270) of the secondary battery (100) can be additionally formed.

[0141] The secondary battery (100) shown positioned in the post-sealing block (700) portion of Fig. 9 shows a state after the first sealing and the second sealing, and is briefly illustrated as a shape including the second sealing portion (760). At this time, the polymer ball (PB) between the battery case (200) and the lead film (400) can be formed in a position-controlled manner.

[0142] Fig. 17 is a cross-sectional view of the sealing step by the post-sealing block of Fig. 14. That is, it shows the function of the post-sealing block (700) during the secondary sealing. By introducing a step in the post-sealing block (700), the polymer ball can be pressed, while ultimately preventing the polymer ball (PB) from flowing out beyond the other end (400_i) of the lead film (400) toward the inside of the secondary battery (100).

[0143] The sealing device of the present invention is characterized by achieving additional sealing by a post-sealing block (700), as illustrated in FIG. 17. When performing secondary sealing by the post-sealing block (700), the polymer ball (PB) previously formed by the primary sealing can be pressed while additionally applying heat. Accordingly, the shape and position of the polymer ball (PB) can be ultimately controlled, and the sealing strength can be further improved by performing the second sealing.

[0144] A sealing method using such a sealing device (500) includes a step of performing primary sealing using a main sealing block (600); and a step of performing secondary sealing using a post sealing block (700). The shapes of the first sealing portion (260) by the primary sealing and the second sealing portion (270) by the secondary sealing are different, and in particular, in the secondary sealing, a step of additionally pressing a polymer ball (PB) formed in the primary sealing is performed.

[0145] In the first sealing, the upper sealing block (600a) and the lower sealing block (600b) of the main sealing block (600) are positioned above and below the rim of the battery case (200), and the area to be sealed is pressed from above and below to apply a certain pressure and temperature, thereby forming the first sealing portion (260). According to one embodiment, the pressure applied to the first sealing portion (260) may be in the range of 0.1 MPa to 5 MPa. In addition, the pressure applied to the first sealing portion (260) may be such that the same pressure is continuously applied while sealing is performed by attaching a pressure gauge to the upper sealing block (600a) and the lower sealing block (600b). Heat in the temperature range of 150°C to 300°C may be applied to the first sealing portion (260). There is a risk that sealing may not occur properly at temperatures below 150°C, and there is a risk that the battery case (200) may be damaged by heat at temperatures exceeding 300°C.

[0146] In the secondary sealing, the upper sealing block (700a) and the lower sealing block (700b) of the post sealing block (700) are positioned above and below the rim of the battery case (200), and the area to be sealed is pressed from above and below to apply a certain pressure and temperature, thereby forming the second sealing portion (270). According to one embodiment, the pressure applied to the second sealing portion (270) may be in the range of 0.1 MPa to 5 MPa. In addition, the pressure applied to the second sealing portion (270) may be such that the same pressure is continuously applied while sealing is performed by attaching a pressure gauge to the upper sealing block (700a) and the lower sealing block (700b). Heat in the temperature range of 150°C to 300°C may be applied to the second sealing portion (270). There is a risk that sealing may not occur properly at temperatures below 150°C, and there is a risk that the battery case (200) may be damaged by heat at temperatures exceeding 300°C.

[0147] The pressure applied during the first sealing may be different from the pressure applied during the second sealing. For example, the pressure applied during the first sealing may be 1 MPa to 3 MPa, and the pressure applied during the second sealing may be 0.5 MPa to 2 MPa.

[0148] The sealing temperature during the first sealing may be the same as or different from the sealing temperature during the second sealing. For example, the sealing temperature during the first sealing may be 130°C to 250°C, and the sealing temperature during the second sealing may be 50°C to 200°C.

[0149] The sealing time for the first sealing can be the same as or different from the sealing time for the second sealing. While having the same sealing time is desirable from a tact time perspective, different sealing times are also possible. For example, the sealing time for the first sealing can be 1 to 4 seconds, while the sealing time for the second sealing can be 5 seconds or more.

[0150] The thickness of the polymer ball (PB) after the second sealing may be 60% to 90% of the thickness of the polymer ball (PB) after only the first sealing. As another example, the thickness of the polymer ball (PB) after only the first sealing may be 220 ㎛ to 290 ㎛, and the thickness of the polymer ball (PB) after the second sealing may be 150 ㎛ to 170 ㎛.

[0151] The sealing strength of the battery case (200) after performing the second sealing may be greater than the sealing strength of the battery case (200) after performing the first sealing. This is because not only is a second sealing portion (270) formed in addition to the first sealing portion (260), but also the first sealing portion (260) and the second sealing portion (270) overlap.

[0152] As seen in FIGS. 12 and 14, the first pressurizing portion (710) protrudes further toward the electrode lead (300) than the second pressurizing portion (720), and the second pressurizing portion (720) can press the polymer ball (PB) formed during the first sealing during the second sealing.

[0153] In addition, as seen in FIGS. 15 and 16, the first pressurizing portion (710) can sequentially form steps in the peripheral pressurizing portion (712), the intermediate pressurizing portion (714), and the electrode lead pressurizing portion (716). In other words, the second pressurizing portion (720) has a shorter height than the step of the electrode lead pressurizing portion (716), and this portion presses the polymer ball (PB).

[0154] In this way, if the first pressurizing portion (710) is also configured with a stepped structure, the area previously sealed with the main sealing block (600) can be positioned within the stepped structure of the first pressurizing portion (710), thereby reducing positional errors during secondary sealing, and the sealed area around the electrode lead (300) can always be aligned with the post sealing block (700), so that sealing can always be performed accurately and uniformly.

[0155] In the above embodiment, the step of the post sealing block (700) is formed so that the pressurized polymer ball (PB) does not go beyond the other end (400_i) of the lead film (400), as shown in FIGS. 6 and 17.

[0156] According to the present invention, by configuring a sealing device (500) including a main sealing block (600) and a post sealing block (700), the sealing strength of the sealing portion (250) can be increased. The electrolyte inside the battery case (200) can be prevented from leaking to the outside, and the sealing strength and sealing reliability of the secondary battery (100) can be improved.

[0157] By using the sealing device (500) of the present invention, the overlapping portion of the first sealing portion (260) and the second sealing portion (270) has the effect of sealing twice, so even if sealing is performed at a low temperature, a secondary battery (100) manufactured using the same can have high sealing strength.

[0158] By using the sealing device (500) of the present invention, there is no need to seal at a temperature so high as to damage the surface of the battery case (200). Even if sealing is performed at a low temperature, since the double sealing step of main sealing and post sealing is applied, the secondary battery (100) manufactured through this can have a high sealing strength.

[0159] According to the present invention, the polymer ball (PB) formed in the internal space of the battery case (200) during the first sealing can be further pressed during the second sealing to further improve the sealing strength. At this time, the sealing device (500) is characterized in that it includes a post sealing block (700) having a step so that the polymer ball (PB) does not come out of the other end (400_i) of the lead film (400) due to excessive pressurization. Accordingly, even if the thickness of the polymer ball (PB) decreases and the length increases while the polymer ball (PB) is additionally pressed, the venting issue of the secondary battery can be solved by limiting the length.

[0160] In this way, according to the present invention, the shape and position of the polymer ball (PB) within the sealing portion (250) can be restricted, and complete sealing is enabled. This prevents the electrolyte inside the battery case (200) from leaking to the outside, and improves the sealing strength and sealing reliability of the secondary battery (100).

[0161] According to the present invention, sealing can be performed by transporting the secondary battery while running a conveyor belt between the main sealing block (600) and the post sealing block (700), so that the sealing device (500) is improved to have sufficient sealing strength even in a short takt time. This can contribute to resolving the venting issue and productivity of the secondary battery (100). In addition, since the primary sealing and secondary sealing can be performed in a fully automated process, the deviation between cells can be reduced during mass production of the secondary battery (100).

[0162] While the preferred embodiments of the present invention have been illustrated and described, the present invention is not limited to the specific preferred embodiments described above, and anyone having ordinary skill in the art to which the invention pertains can make various modifications without departing from the gist of the present invention as claimed in the claims, and such modifications are within the scope of the claims.

[0163] [Explanation of symbols]

[0164] 100: Secondary battery 110: Electrode assembly

[0165] 200: Battery case 250: Sealing part

[0166] 260: First sealing section 270: Second sealing section

[0167] 300: Electrode lead 400: Lead film

[0168] 500: Sealing device 600: Main sealing block

[0169] 610, 712: Pressurized part 620: Concave part

[0170] 630, 714: Middle pressurized section 640, 716: Electrode lead pressurized section

[0171] 700: Post sealing block 710: First pressurizing section

[0172] 720: Second pressurized section 800: Conveyor belt

Claims

1. A secondary battery including a battery case having an electrode assembly with protruding electrode leads and a sealing portion having a sealed outer periphery, The above sealing portion is a first sealing portion on the electrode lead side of the battery case; and Includes a second sealing portion on the electrode lead side of the battery case, A secondary battery characterized in that the first sealing portion and the second sealing portion each include one end and the other end in the protruding direction of the electrode lead, and the other end of the second sealing portion extends in a direction opposite to the protruding direction of the electrode lead more than the other end of the first sealing portion.

2. A secondary battery characterized in that in the first paragraph, the length of the first sealing portion is longer than the length of the second sealing portion, and the width of the second sealing portion is larger than the width of the first sealing portion.

3. A secondary battery, characterized in that in the first paragraph, the first sealing portion and the second sealing portion overlap at least partially in the protruding direction of the electrode lead.

4. A secondary battery characterized in that one end of the second sealing portion and one end of the first sealing portion are positioned on the same line in the first paragraph.

5. A secondary battery characterized in that, in the first paragraph, one end of the second sealing portion is spaced apart from one end of the first sealing portion in a direction opposite to the protrusion direction of the electrode lead.

6. In the first paragraph, a lead film is further included located at a portion corresponding to the first sealing portion and the second sealing portion, The above lead film includes one end and the other end in the protruding direction of the electrode lead, A secondary battery characterized in that a polymer ball is formed by a fused resin between the battery case and the lead film inside the second sealing portion, and the polymer ball is formed so as not to protrude from the other end of the lead film.

7. A sealing device for a secondary battery for sealing a battery case having an electrode assembly with protruding electrode leads. A main sealing block including an upper sealing block that applies pressure downward from the upper portion of the first sealing portion on the electrode lead side of the battery case and a lower sealing block that applies pressure upward from the lower portion of the first sealing portion; and A post sealing block including an upper sealing block that applies pressure downward from the upper portion of the second sealing portion on the electrode lead side of the battery case and a lower sealing block that applies pressure upward from the lower portion of the second sealing portion; A sealing device characterized in that the first sealing portion and the second sealing portion each include one end and the other end in the protruding direction of the electrode lead, and the shapes of the main sealing block and the post sealing block are different from each other so that the other end of the second sealing portion extends in a direction opposite to the protruding direction of the electrode lead than the other end of the first sealing portion.

8. In the 7th paragraph, a sealing device characterized in that a lead film including one end and the other end in the protruding direction of the electrode lead is attached to the electrode lead, and the main sealing block includes a concave portion corresponding to the electrode lead side including the lead film on the lower surface of the upper sealing block and the upper surface of the lower sealing block, respectively.

9. A sealing device according to claim 8, wherein the upper sealing block lower surface and the lower sealing block upper surface of the main sealing block include a peripheral pressurizing portion that pressurizes the battery case, and the concave portion pressurizes the electrode lead and the lead film.

10. A sealing device according to claim 9, characterized in that the concave portion includes an electrode lead pressing portion that presses the electrode lead and an intermediate pressing portion that connects the electrode lead pressing portion and the peripheral pressing portion in a stepwise manner.

11. A sealing device according to claim 8, characterized in that the length of the main sealing block is longer than the width of the electrode lead including the lead film and extends to the surrounding battery case.

12. A sealing device according to claim 11, characterized in that the length of the post sealing block is shorter than the length of the main sealing block.

13. A sealing device characterized in that, in the 7th paragraph, the upper sealing block and the lower sealing block of the main sealing block have a step formed from top to bottom, and the upper sealing block and the lower sealing block of the post sealing block have a step formed opposite to the protrusion direction of the electrode lead.

14. In the 7th paragraph, the post sealing block comprises a first pressurizing portion that pressurizes a portion overlapping the first sealing portion; and A sealing device characterized by including a second pressurizing portion that pressurizes a portion opposite to the protruding direction of the electrode lead compared to the first pressurizing portion.

15. A sealing device according to claim 14, characterized in that the width of the second pressurizing portion does not exceed 50% of the width of the first pressurizing portion.

16. A sealing device according to claim 14, characterized in that the first pressurizing portion protrudes further toward the electrode lead than the second pressurizing portion.

17. A sealing device according to claim 16, characterized in that the height difference between the first pressurizing portion and the second pressurizing portion is 0.1 mm to 5 mm.

18. In paragraph 14, The second pressurizing portion protrudes in a direction perpendicular to the first pressurizing portion, The first pressurizing portion has a first pressurizing surface that is a single plane and is in contact with the battery case, The second pressurizing portion has a second pressurizing surface that is a single plane and is in contact with the battery case, A sealing device characterized in that the pressing force of the first pressing surface is greater than the pressing force of the second pressing surface.

19. In paragraph 14, The second pressurizing portion protrudes in a direction perpendicular to the first pressurizing portion, The above first pressurizing portion is a peripheral pressurizing portion that pressurizes the battery case; An electrode lead pressurizing unit for pressing the electrode lead; and A sealing device characterized by including an intermediate pressurizing portion that connects the electrode lead pressurizing portion and the peripheral pressurizing portion in a stepwise manner.

20. In the 8th paragraph, when the battery case is positioned on the main sealing block, the fused resin between the battery case and the lead film is pushed into the first sealing portion by the main sealing block to form a polymer ball. A sealing device characterized in that when the battery case moves from the main sealing block and is positioned on the post sealing block, the polymer ball is pressed by the post sealing block.

21. A sealing device characterized in that, in the 20th paragraph, a step is formed in the post sealing block so that the pressurized polymer ball does not go beyond the other end of the lead film.

Images