Secondary battery

Abstract

A secondary battery according to one embodiment of the present specification comprises: an electrode assembly; an exterior film having an inner space for accommodating the electrode assembly, and an exterior material opening for communicating the inner space with the outside; a cover member for covering the exterior material opening of the exterior film; and a gasket member disposed between the cover member and the exterior film, wherein the gasket member has a plurality of cover sealing parts in contact with the exterior film, the exterior film has a film sealing part on any one surface of surfaces perpendicular to the exterior material opening, and IDV, which is defined as a factor of the sealing length and width of the cover sealing parts and the film sealing part, is 0.5 or more. The secondary battery can ensure safety by inducing a vent direction.

Description

secondary battery

[0001] This specification relates to a secondary battery.

[0002]

[0003] In general, secondary batteries are batteries that can be recharged, unlike primary batteries that cannot be recharged, and are widely used in electronic devices such as cell phones, laptops, camcorders, and electric vehicles.

[0004] Secondary batteries can be classified into cylindrical or square batteries in which the electrode assembly is built into a cylindrical or square metal can, and pouch-type batteries in which the electrode assembly is built into a pouch-type case of a laminate sheet, depending on the shape of the battery case.

[0005] Fig. 1 is a drawing illustrating an example of a pouch-type secondary battery. The pouch-type secondary battery (1, pouch-type cell) includes an electrode assembly (2) formed by alternately stacking electrodes and separators, and a pouch-type outer case (20) in which the electrode assembly (2) is accommodated. Electrode tabs (15) may be connected to the electrodes of the electrode assembly (2), respectively. The electrode tabs (15) may be welded to each other in a predetermined region and then connected to an electrode lead (17) by welding. The outer case (20) includes a receiving portion (21; cup portion) for accommodating the electrode assembly (2). The receiving portion (21) of the outer case (20) may be formed by one or two concave-shaped portions. Fig. 1 illustrates an example of a receiving portion (21) formed by two concave-shaped portions. Such an outer case (20) may be manufactured by forming a pouch film. A sealing portion (23, sealing portion or terrace) is formed around the periphery of the receiving portion (21) by sealing.

[0006] Meanwhile, the depth of the cup portion formed into the pouch film is limited by the material properties of the pouch film. Consequently, it is difficult to form the cup portion deep enough to increase battery capacity, and the material and thickness of the pouch film must be selected with restrictions. As the pouch film thickness decreases during cup portion forming, defects such as cracks can easily occur in the outer packaging.

[0007] Accordingly, pouch-type cases that can accommodate electrode assemblies without forming a cup portion are being developed. In such cases, four sides are wrapped with a pouch film, and the remaining two sides are sealed using a material such as a cap. In this case, the direction in which venting occurs varies, such as the side where the pouch film is sealed, the side where the material such as the cap is sealed, and the direction in which it occurs is not constant. In this case, if a venting occurs in the direction in which the electrode terminals are arranged, an electrical short may occur and rapid heat propagation may occur, which may lead to an explosion or fire. Predicting the direction of venting becomes even more difficult when the specifications of the secondary battery change, and accordingly, the safety of the secondary battery may be very vulnerable.

[0008]

[0009] Embodiments of the present specification are intended to provide a secondary battery capable of solving various problems occurring in the process of forming a cup portion for accommodating an electrode assembly.

[0010] In addition, the embodiments of the present specification are intended to provide a secondary battery with improved safety by controlling the vent direction by controlling the sealing length and sealing width of the cover sealing portion and the film sealing portion.

[0011]

[0012] [1] In one example, a secondary battery includes an electrode assembly, an outer film having an internal space for accommodating the electrode assembly, an outer film having an outer opening for communicating the internal space with the outside, a cover member covering the outer opening of the outer film, and a gasket member disposed between the cover member and the outer film, wherein the gasket member has a plurality of cover sealing portions in contact with the outer film, and the outer film has a film sealing portion on one of the surfaces perpendicular to the outer opening, and is defined by the following equation 1. DV It can be greater than 0.5.

[0013] [Formula 1]

[0014] I DV = (W c x L f ) / (P c x W f )

[0015] In the above equation 1, W c is the sealing width (mm) of the cover sealing part, and P c is the total sealing length (mm) of the above multiple cover sealing parts, and W f is the sealing width (mm) of the film sealing part, and L f is the sealing length (mm) of the film sealing part.

[0016] [2] In the secondary battery of the above [1], the I DV can be between 0.5 and 5.0.

[0017] [3] In the secondary battery of [1] and / or [2], the outer film may have a shape in which a predetermined sheet having a first end and a second end spaced apart from the first end in a predetermined direction is rolled or folded so that the first end and the second end meet each other, and the film sealing portion may be provided at a portion where the first end and the second end meet each other.

[0018] [4] In at least one of the secondary batteries of [1] to [3], the film sealing portion may be provided on a surface corresponding to the thickness of the electrode assembly among surfaces perpendicular to the outer material opening of the outer film.

[0019] [5] In at least one of the secondary batteries of [1] to [4], the W c can be from 3 mm to 30 mm.

[0020] [6] In at least one of the secondary batteries of [1] to [5], the W f can be from 5 mm to 20 mm.

[0021] [7] In at least one of the secondary batteries of [2] to [6], the inner surface of the first terminal can be combined with the inner surface or outer surface of the second terminal.

[0022] [8] In at least one of the secondary batteries of [1] to [7], the cover member includes a first member that blocks the opening of the outer material, and a second member that extends from the first member and is disposed facing the inner surface of the outer film, and the gasket member can be disposed between the second member and the inner surface of the outer film.

[0023] [9] In the secondary battery of [8], the second member is formed along the edge of the first member, and can extend in a direction facing the internal space from the first member.

[0024]

[0010] In the secondary battery of [8] and / or [9], the second member may have a length that contacts the electrode assembly within the outer film.

[0025]

[0011] In at least one of the secondary batteries of [8] to

[0010] , the second member is formed along the edge of the first member, and can extend from the first member in a direction facing the outside.

[0026]

[0012] In at least one of the secondary batteries of [1] to

[0011] , the cover member may have a through hole through which an electrode lead electrically connected to the electrode assembly passes.

[0027]

[0013] In at least one of the secondary batteries of [1] to

[0012] , the gasket member may include a first layer having an inner surface that allows bonding with an outer surface of the cover member facing the inner surface of the outer film, and an outer surface that allows bonding with the inner surface of the outer film.

[0028]

[0014] In at least one of the secondary batteries of [1] to

[0013] , the gasket member may include a first layer that allows bonding with the outer surface of the cover member facing the inner surface of the outer film, and a second layer that is laminated on the outer surface of the first layer and allows bonding with the inner surface of the outer film.

[0029]

[0015] In at least one of the secondary batteries of [1] to

[0014] , the gasket member may include a first layer that allows bonding with the outer surface of the cover member facing the inner surface of the outer film, a second layer that allows bonding with the inner surface of the outer film, and a third layer disposed between the first layer and the second layer.

[0030]

[0031] According to one embodiment of the present specification, a secondary battery can be provided with an outer shell without forming a cup portion for accommodating an electrode assembly, so that the battery capacity can be easily increased by increasing the size of the outer shell, the material and thickness of the sheet for manufacturing the outer shell can be selected relatively freely, and defects such as cracks can be less likely to occur.

[0032] In addition, the secondary battery according to one embodiment of the present specification can control the direction in which a vent is generated by adjusting the sealing width and sealing length of the cover sealing portion and the film sealing portion, so that even when the specifications of the secondary battery are changed, improvement in safety can be expected.

[0033]

[0034] Figure 1 is a drawing illustrating an example of a pouch-type secondary battery.

[0035] FIG. 2 is a perspective view illustrating a secondary battery according to the first embodiment of the present specification.

[0036] Figure 3 is an exploded perspective view of the secondary battery of Figure 2.

[0037] Fig. 4 is a cross-sectional view illustrating a first modified example of an outer film of the secondary battery of Fig. 2.

[0038] Fig. 5 is a cross-sectional view illustrating a second modified example of an outer film of the secondary battery of Fig. 2.

[0039] Figure 6 is a cross-sectional view along line AA of the secondary battery of Figure 2.

[0040] Fig. 7 is a cross-sectional view illustrating a first modified example of a gasket member of the secondary battery of Fig. 2.

[0041] Fig. 8 is a cross-sectional view illustrating a second modified example of a gasket member of the secondary battery of Fig. 2.

[0042] Fig. 9 is a cross-sectional view illustrating a third modified example of a gasket member of the secondary battery of Fig. 2.

[0043] Fig. 10 is a perspective view illustrating a secondary battery according to the second embodiment of the present specification.

[0044] Figure 11 is an exploded perspective view of the secondary battery of Figure 10.

[0045] Fig. 12 is a cross-sectional view along line BB of the secondary battery of Fig. 10.

[0046]

[0047] The advantages and features of the secondary battery described in this specification, and the methods for achieving them, will become clear with reference to the embodiments described in detail below together with the accompanying drawings. However, the secondary battery described in this specification is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0048] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise.

[0049] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the invention relating to the secondary battery described herein. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0050] In this specification, when a part is described as including a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0051] In this specification, the description "A and / or B" means A, or B, or A and B.

[0052] Hereinafter, the secondary battery described in this specification will be explained in detail.

[0053] In this specification, a secondary battery comprises one or more of the technical features and / or technical configurations described below, and these technical features and / or technical configurations may be combined in various ways.

[0054]

[0055] In one aspect, an electrode assembly; an outer film having an internal space for accommodating the electrode assembly and an outer material opening for communicating the internal space with the outside; a cover member covering the outer material opening of the outer film; and a gasket member disposed between the cover member and the outer film, wherein the gasket member has a plurality of cover sealing portions in contact with the outer film, and the outer film has a film sealing portion on one of the surfaces perpendicular to the outer material opening, and I defined by the following equation 1 DV A secondary battery with a value of 0.5 or higher is provided.

[0056] [Formula 1]

[0057] I DV = (W c x L f ) / (P c x W f )

[0058] In the above equation 1, W c is the sealing width (mm) of the cover sealing part, and P c is the total sealing length (mm) of the above multiple cover sealing parts, and W f is the sealing width (mm) of the film sealing part, and L f is the sealing length (mm) of the film sealing part.

[0059] As mentioned above, conventional pouch-type secondary batteries using cup-shaped molding have numerous challenges that require resolution. To address these challenges, the present invention provides the secondary battery described herein. However, in the case of the secondary battery described herein, it is difficult to predict the direction of venting, and when the specifications change, the predictability is significantly reduced, making it difficult to ensure safety.

[0060] Therefore, in order to ensure the safety of the secondary battery, a method to induce the direction in which the vent is generated in a desired direction is proposed, and the direction in which the vent is generated can be controlled by adjusting the sealing width and sealing length of the sealed portion. In this regard, I as defined in Equation 1 is DV We aim to provide a secondary battery designed to have a capacity of 0.5 or more.

[0061]

[0062] Secondary battery vent direction control index

[0063] In one aspect, the secondary battery is defined by the following formula 1: DV It is characterized by being 0.5 or higher.

[0064] [Formula 1]

[0065] I DV = (W c x L f ) / (P c x W f )

[0066] In the above equation 1, W c is the sealing width (mm) of the cover sealing part, and P c is the total sealing length (mm) of the above multiple cover sealing parts, and W f is the sealing width (mm) of the film sealing part, and L f is the sealing length (mm) of the film sealing part.

[0067] The above I DVIt can be defined as the ratio of the product of the sealing width of the cover sealing part and the sealing length of the film sealing part to the product of the total sealing length (sealing perimeter) of the cover sealing part and the sealing width of the film sealing part, and on the other hand, it can also be defined as the value obtained by dividing the ratio of the sealing width to the total sealing length of the cover sealing part by the ratio of the sealing width to the sealing length of the film sealing part. The above factors may be factors that enable a vent to occur at an appropriate time and in an appropriate direction when the internal pressure increases due to the occurrence of an event in the cell of a secondary battery.

[0068]

[0069] Hereinafter, with reference to FIG. 2, the I DV It explains the factors that make up it, their correlations, and their technical meaning.

[0070] The above I DV As the value increases, it can be seen that the predictability of the direction in which the vent occurs increases, and accordingly, the sealing length (L) of the film sealing portion (138) f ) is long and the sealing width (W) of the cover sealing part (158) c ) can be seen as the main thing to widen. The sealing width (W) of the film sealing part f ) is narrow and the sealing length of the cover sealing part (P c ) is long, there is a high possibility that a vent will occur in the direction of the cover member when the internal pressure increases. However, the sealing length (L) of the film sealing part and the cover sealing part f , P c ) is a factor related to the specifications of a secondary battery, it is desirable to adjust the specifications of the stack cell of the secondary battery, i.e., the length direction (L) and width direction (W) of the electrode assembly, when determining the specifications.

[0071] Here, the sealing length (P) of the cover sealing part (158) c ) corresponds to the second member (152) of the cover member (150) to be described later and means its circumference, and "2L cL + 2LcS " can be produced as I DV is affected by the circumference of the cover member (150), and the circumference can be derived by the sum of the short side and the long side of the cover member (150) as described above. However, in order to adjust the circumference, L cL When adjusting L and L, L cL It refers to the width of the electrode assembly and is not easy to adjust, but L cS The thickness of the electrode assembly, i.e. the number of stacked cells, can be easily controlled. However, L cS When increasing the number of stacked cells to increase the size, advanced welding and sealing technologies between electrode tabs may be required. Therefore, it is desirable to adjust the circumference by taking all these factors into consideration.

[0072] The above I DV As the value increases, the predictability of the vent direction increases, but controlling it to satisfy the appropriate value may be desirable in terms of the energy density of the secondary battery.

[0073] I DV The increase in the sealing width (W) of the cover sealing part c ) is increased and the sealing length of the film sealing part (L) f ) is longer, or the sealing length of the cover sealing part (P c ) is shortened and the sealing width (W) of the film sealing part f ) may mean that the size is getting smaller.

[0074] Sealing length of film sealing part (L) f ) is desirable in terms of improving energy density, but the length of the secondary battery may not be freely changed in some cases. In addition, the sealing width (W) of the film sealing part f) is desirable in terms of vent induction, and the fairness of the sealing process, which is affected by surface pressure, may be excellent. However, considering the minimum sealing force required to withstand internal pressure in a general operating situation, if it is made too narrow, the problem of lowering the vent pressure may occur.

[0075] Sealing width of cover sealing part (W) c ) and sealing length (P c ) may have a significant impact, the sealing length of the cover sealing part (P c ) can be designed to change the structure by stacking two cells in the space occupied by one cell, and the sealing width (W c ) is also easy to control. However, the sealing width (W c ) may determine the length by which the cover member (150) extends into the inner space (131) of the outer film, which may mean that the space that can accommodate the electrode assembly is reduced. The sealing width (W) of the cover sealing portion c ) can have a significant impact on the loss of internal space, considering the essential design parts that must be introduced into the internal space for sealing, and the fact that the cover member is joined on both sides to seal. This difference can have a significant impact on the energy density, and when viewed on a module or pack basis, it can be a level that is difficult to ignore. DV It is desirable to design the secondary battery in a way that it does not become too large, and preferably, it can be made to be less than 5.0.

[0076] The above I DV is characterized by being 0.5 or more, and preferably may be 0.5 to 5.0. The above I DV If it is less than 0.5, there is a problem that the vent direction cannot be controlled as described above.

[0077] The above I DVThe secondary battery can be manufactured and designed so that the value can be at least 0.5, and preferably, it can be 0.51 or more, 0.53 or more, 0.55 or more, or 0.58 or more. In addition, it can be more preferably 4.90 or less, 4.50 or less, 4.00 or less, 3.50 or less, 3.00 or less, or 2.90 or less. The above I DV When designing a secondary battery to have values ​​in this range, not only long cells with a small width (W) and a long length (L), but also cells with a short length (L) and a large width (W), safety can be ensured by securing a vent pressure above a certain level while inducing the direction when venting due to an event occurring inside the outer film.

[0078] The above I DV In terms of satisfying the above, it is desirable that the sealing width be controlled during sealing, and the above W c It can be 3 mm to 30 mm. Preferably, it can be 3.5 mm or more, 4 mm or more, and also 25 mm or less, 20 mm or less, 15 mm or less, or 10 mm or less.

[0079] Also, the above I DV In terms of satisfying the above W f It may be 5 mm to 20 mm, preferably 6 mm or more, 7 mm or more, or 8 mm or more, and may also be 18 mm or less, 15 mm or less, or 12 mm or less.

[0080]

[0081] Structure of secondary batteries

[0082] Hereinafter, with reference to the attached drawings, preferred embodiments of the present specification are described in detail so that a person having ordinary skill in the art can easily implement the present invention.

[0083]

[0084] First embodiment

[0085] FIG. 2 is a perspective view illustrating a secondary battery (100) according to a first embodiment of the present specification, and FIG. 3 is an exploded perspective view of the secondary battery (100) of FIG. 2. The secondary battery (100) according to the first embodiment of the present specification may include an electrode assembly (110), an outer film (130), a cover member (150), and a gasket member (120), as illustrated in FIGS. 2 and 3. Hereinafter, the secondary battery (100) of the present embodiment will be described with reference to FIG. 3. For reference, the contents of the first embodiment may be equally applied to the embodiments described below, as long as they do not conflict with each other, and the technical configurations of each may be combined or changed if technically possible.

[0086]

[0087] Electrode assembly (110)

[0088] An electrode assembly (110) may be formed by alternately stacking electrodes and separators. The electrodes may include a positive electrode and a negative electrode. The electrode assembly (110) may include electrode tabs (111) connected to the electrodes. The electrode tabs (111) may be provided separately or may be provided as part of a current collector constituting the electrode. The electrode tabs (111) may be welded to each other in a predetermined area and then electrically connected to an electrode terminal (155) described below.

[0089]

[0090] Exterior film (130)

[0091] The exterior film (130) may be an exterior material that accommodates the electrode assembly (110). The exterior film (130) may include an internal space (131) that accommodates the electrode assembly (110). The exterior film (130) may include an exterior material opening (132) that communicates the internal space (131) with the outside of the exterior film (130). The exterior material opening (132) may be provided at each end in the longitudinal direction of the exterior film (130). The exterior material opening (132) may be sealed by a cover member (150) and a gasket member (120) to be described later.

[0092] The outer film (130) can be obtained from a predetermined sheet (130a). The predetermined sheet (130a) can be a sheet having a first end (135) and a second end (136) spaced apart from the first end (135) in a predetermined direction. When such a sheet (130a) is rolled or folded so that the first end (135) and the second end (136) meet, the outer film (130) can be obtained.

[0093] The first end (135) and the second end (136) can be joined together. An adhesive, an adhesive film, or heat fusion may be used for joining. In this case, the inner surface of the first end (135) may be joined to the inner surface of the second end (136), as shown in FIG. 3 and 4. Alternatively, as shown in FIG. 5, the inner surface of the first end (135') may be joined to the outer surface of the second end (136'). Thus, a film sealing portion (138) may be provided at the part where the first end (135) and the second end (136) meet.

[0094] Fig. 4 is a cross-sectional view illustrating a first modified example of the outer film (130) of the secondary battery (100) of Fig. 2. The joint portion of the first end (135') and the second end (136') may be folded in the direction of the arrow in Fig. 5. This can reduce the space occupied by the outer film (130'). In this way, when the inner surfaces of the first end (135') and the second end (136') are joined, for example, by heat-sealing, and then folded, an outer film (130) having a shape similar to that in Fig. 3 can be formed.

[0095] Fig. 5 is a cross-sectional view illustrating a second modified example of the outer film (130) of the secondary battery (100) of Fig. 2. The connection between the first end (135') and the second end (136') may be formed by the inner surface and the outer surface or the outer surface and the inner surface meeting each other, and in this case, folding to reduce the space occupied by the secondary battery after sealing may not be necessary.

[0096] Although not limited, when the first end (135') and the second end (136') form an inner-to-outer bond as in Fig. 4, sealing may be performed using heat fusion, and when the first end (135') and the second end (136') form an inner-to-outer bond as in Fig. 5, sealing may be performed using an adhesive film or adhesive. The method of forming the bond and sealing may be selectively applied, but sealing using heat fusion may be preferable in terms of sealing performance.

[0097] The above film sealing portion (138) may be formed to have a length in the longitudinal direction (L) of the electrode assembly (110) on any one of the surfaces perpendicular to the outer material opening (132) of the outer film (130). However, preferably, the film sealing portion (138) may be formed on a surface corresponding to the thickness of the electrode assembly, that is, on a surface corresponding to a short side among the four sides of the cover member (150) described later, and when the electrode assembly (110) is surrounded using the outer film (130), it may be tightly surrounded so that there is no empty space inside.

[0098] The sheet (130a; see FIG. 3) may be a sheet including a metal layer such as aluminum or stainless steel. The sheet (130a) may also be a laminate sheet further including a resin layer laminated on the metal layer. The resin layer may include a first resin layer disposed on the inner surface of the metal layer. The first resin layer may be a layer formed of polypropylene (PP) or polyphthalamide (PPA). Since the first resin layer may require high insulation and corrosion resistance, the first resin layer may be formed of another resin that satisfies such requirements. The resin layer may include a second resin layer disposed on the outer surface of the metal layer. The second resin layer may be a layer formed of polyethylene terephthalate (PET). Since the second resin layer may require protection and insulation of the secondary battery (100), the second resin layer may be formed of another resin that satisfies such requirements.

[0099]

[0100] Cover member (150)

[0101] The cover member (150) may be a member that covers the exterior material opening (132) of the exterior film (130) as shown in FIGS. 2 and 3. In order to prevent leakage of the electrolyte filled in the internal space (131) of the exterior film (130), the cover member (150) may seal the exterior material opening (132) of the exterior film (130) together with the gasket member (120) to be described later.

[0102] The cover member (150) may include a first member (151) that blocks the outer material opening (132) as illustrated in FIGS. 3 and 6. FIG. 6 is a cross-sectional view taken along line AA of the secondary battery of FIG. 2. The first member (151) may be formed to correspond to the shape of the outer material opening (132) in order to block the outer material opening (132). FIG. 3 illustrates a first member (151) formed in a square shape (the shape of the outer material opening).

[0103] The first member (151) may be obtained from a material that is not easily permeable to moisture in order to seal the internal space (131) of the outer film (130). For example, the first member (151) may be obtained from metal or resin, or from a laminate sheet including a metal layer. The same may be true for the second member (152) described below.

[0104] As shown in FIG. 5, the cover member (150) may include a second member (152) extending from the first member (151). The second member (152) may be formed integrally with the first member (151), or may be formed separately and then joined to the first member (151). The second member (152) may be positioned opposite the inner surface of the exterior film (130).

[0105] Conventionally, a pouch-shaped outer packaging material was manufactured by forming a cup portion on a pouch film and sealing the cup portion with another pouch film. However, the molding depth of the cup portion was limited by the material properties of the pouch film, making it difficult to form the cup portion deeply enough to increase battery capacity. Furthermore, the material and thickness of the pouch film had to be selected within certain limits. Furthermore, as the thickness of the pouch film decreased during the molding process, defects such as cracks were likely to occur in the pouch-shaped outer packaging material.

[0106] In contrast, in the case of the secondary battery (100) of the present embodiment, since the outer film (130) is prepared without forming the cup portion, and the electrode assembly (110) can be inserted into the outer film (130) through the outer material opening (132), the above limitations or defects do not occur, so the battery capacity can be easily increased by increasing the size of the outer film (130), the material and thickness of the sheet (130a) can be selected relatively freely, and defects such as cracks can not easily occur. For reference, in the case where the outer film (130) is prepared by rolling or folding the sheet (130a), the sheet (130a) can be rolled or folded while the electrode assembly (110) is positioned on the upper surface of the sheet (130a) in the unfolded state, and even in this case, the outer film (130) can be prepared without forming the cup portion.

[0107] In addition, the secondary battery (100) of the present embodiment is superior not only to conventional pouch-type batteries but also to square batteries. In the case of square batteries, if the volume expansion of the electrode assembly occurs during charging and discharging, the electrode assembly may be damaged due to the square metal can that hardly experiences shape change. In contrast, in the case of the secondary battery of the present embodiment, if the volume expansion of the electrode assembly occurs during charging and discharging, the shape of the outer film may change accordingly, i.e., the outer film may be stretched, so that damage to the electrode assembly may not occur.

[0108]

[0109] Gasket absence (120)

[0110] The gasket member (120) may be a member disposed between the cover member (150) and the outer film (130), as illustrated in FIGS. 2 and 3. The gasket member (120) may be disposed between the second member (152) of the cover member (150) and the inner surface of the outer film (130), as illustrated in FIG. 6.

[0111] The gasket member (120) may be formed to entirely surround the cover member (150), as illustrated in FIG. 3. For example, the gasket member (120) may be formed in a frame shape to surround the second member (152) of the cover member (150). Alternatively, the gasket member (120') may be formed to entirely surround not only the second member (152), but also the inner sides of the first member (151) and the second member (152), i.e., the inner side of the cover member (150), as illustrated in FIG. 7. FIG. 7 is a cross-sectional view illustrating a first modified example of the gasket member (120) of the secondary battery of FIG. 2.

[0112] The gasket member (120) can prevent the electrolyte inside from leaking through the space between the cover member (150) and the outer film (130).

[0113] Referring to FIG. 2, the cover sealing portion (158) can be formed by combining a gasket member (120) that surrounds the second member (152) of the cover member (150) and an outer film (130) that comes into contact therewith.

[0114] The gasket member (120) can be placed between the cover member (150) and the outer film (130) to improve the bonding strength therebetween. For example, the gasket member (120) can include a first layer (121) having an inner surface that allows bonding with the outer surface of the cover member (150) facing the inner surface of the outer film (130), and an outer surface that allows bonding with the inner surface of the outer film (130), as illustrated in FIG. 6. FIG. 6 illustrates the first layer (121) laminated on the outer surface of the second member (152) of the cover member (150). For reference, the outer surface can be defined along the direction from the inner side to the outer side of the outer film (130) based on the up-down direction of FIG. 6, and the inner surface can be defined along the direction from the outer side to the inner side of the outer film (130).

[0115] The gasket member (120) may include a first layer (121) as described above, and as a material applied to the first layer (121), a material that facilitates bonding of the cover member (150) and the outer film (130) may be applied, and for example, the first resin may be selected from a resin having a melting point (Tm) of 135°C to 150°C, a resin having a melt flow rate (MFR) of 4 g / 10 min to 10 g / min at 230°C, and a resin having a melting point (Tm) of 135°C to 150°C and a melt flow rate (MFR) of 4 g / 10 min to 10 g / min. When the first resin having the above properties is applied to the first layer, it has excellent heat resistance, so it can withstand heat fusion at high temperatures without change in appearance, thereby ensuring sufficient sealing strength and excellent durability against pressure increase caused by gas generated inside the case.

[0116] For example, the first resin may be a modified polyolefin-based resin, and may be included in the first layer in an amount exceeding 50 wt%, preferably 70 wt% or more, 80 wt% or more, or 90 wt% or more, and may be applied as the first resin alone, and when mixed, the remainder may be an appropriate resin such as another polyolefin-based resin. The modified polyolefin-based resin may be modified by an acid or a siloxane, preferably modified by an acid, and more preferably may be a polyolefin copolymerized or post-treated with a monomer containing acrylic acid, and may be, for example, acid-modified polypropylene or acid-modified polyethylene, and plasma-treated polypropylene or polyethylene may be applied, and more preferably may include acid-modified polypropylene. In the case of applying a polyolefin modified in this way, since the functional group introduced by modification improves the bonding strength with the surface of the metal, it may be more advantageous for the adhesion between the metal and the resin, and considering that the cover member (150) may be applied with a metal as the material, it may be preferable to apply a resin such as that described above to the gasket member (120).

[0117] The gasket member (120'') may include, as illustrated in FIG. 8, a first layer (121'') that allows bonding with the outer surface of the cover member (150) facing the inner surface of the outer film (130), and a second layer (122'') that is laminated on the outer surface of the first layer (121'') and allows bonding with the inner surface of the outer film (130). FIG. 8 is a cross-sectional view illustrating a second modified example of the gasket member (120) of the secondary battery of FIG. 2. FIG. 8 illustrates the first layer (121'') that is laminated on the outer surface of the second member (152) of the cover member (150).

[0118] As described above, the gasket member (120'') may include a first layer (121'') and a second layer (122''). In this case, the material that can be applied to the first layer (121'') may be a material that can improve the bonding strength with the cover member (150), and the material that can be applied to the second layer (122'') may be a material that can improve the bonding strength with the exterior film (130).

[0119] For example, the first layer has a melting point (T m A resin having a temperature of 135°C to 150°C, a resin having a melt flow rate (MFR) at 230°C of 4 g / 10 min to 10 g / 10 min, and a melting point (T m ) comprises a first resin selected from the group consisting of resins having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C and a melting point (T m A resin having a temperature of 120°C to 145°C, a resin having a melt flow rate (MFR) at 230°C of 5 g / 10 min to 18 g / 10 min, and a melting point (T m It may include a second resin selected from the group consisting of resins having a temperature of 120°C to 145°C and a melt flow rate (MFR) at 230°C of 5 g / 10 min to 18 g / 10 min.

[0120] When the gasket member (120'') is composed of a double layer, there is an advantage that the bonding strength with the cover member (150) and the bonding strength with the exterior film (130) can be further improved compared to when it is composed of a single layer, and the sealing strength can be further improved. In particular, if a resin with a lower melting point or lower melt flow rate than the first resin applied to the first layer is included as the second resin in the second layer, the physical properties can be more similar to those of the exterior film (130), and as a result, not only can the sealing processability be improved, but the bonding strength by thermal fusion can also be expected, so that the sealing strength increases and the durability due to the resulting increase in internal pressure can be greatly improved.

[0121] The first resin included in the first layer may be as described above, and the second resin included in the second layer may be, for example, a polyolefin-based resin. In this case, the difference from the first resin may lie in the introduction of a modification group, and the second resin may be an unmodified polyolefin-based resin, and may include, for example, polypropylene or polyethylene, and may be a homopolymer thereof, or may be a block copolymer or random copolymer copolymerized with a small amount of comonomer. In addition, when the second resin is included in the second layer, the content thereof may be the same as when the first resin is included in the first layer.

[0122] The gasket member (120''') may include, as illustrated in FIG. 9, a first layer (121''') that allows bonding with the outer surface of the cover member (150) facing the inner surface of the outer film (130), a second layer (122''') that allows bonding with the inner surface of the outer film (130), and a third layer (133''') that is disposed between the first layer (121''') and the second layer (122'''). FIG. 9 is a cross-sectional view illustrating a third modified example of the gasket member in the secondary battery of FIG. 2.

[0123] The gasket member (120''') may include a first layer (121''') and a second layer (122''') as described above, and may further include a third layer (123''') therebetween. In the case of the third layer (123'''), it may be arranged between the first layer (121''') and the second layer (122''') to maintain its shape, and may contribute to improving sealing properties by maintaining the sealing thickness between the cover member (150) and the outer film (130) during sealing or battery operation.

[0124] For example, the first layer included in the gasket member has a melting point (T mA resin having a temperature of 135°C to 150°C, a resin having a melt flow rate (MFR) at 230°C of 4 g / 10 min to 10 g / 10 min, and a melting point (T m ) comprises a first resin selected from the group consisting of resins having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C and a melting point (T m A resin having a temperature of 120°C to 145°C, a resin having a melt flow rate (MFR) at 230°C of 5 g / 10 min to 18 g / 10 min, and a melting point (T m ) comprises a second resin selected from the group consisting of resins having a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C and a melting point (T m ) resin having a melting point (T ) of 145°C to 170°C, a melt flow rate (MFR) of 2 g / 10 min to 4 g / 10 min at 230°C, and a melting point (T ) of m ) may include a third resin selected from the group consisting of resins having a melt flow rate (MFR) of 2 g / 10 min to 4 g / 10 min at 230°C and a melting point of 145°C to 170°C.

[0125] The third resin that can be applied to the third layer (123''') can be, for example, a resin that satisfies the above-mentioned melting point and melt flow rate range within the same type of resin range as the second resin.

[0126]

[0127] Specific structure of cover member (150)

[0128] The cover member (150) may include an electrode terminal (155) as illustrated in FIG. 6. The electrode terminal (155) may be an electrically conductive member provided in the first member (151). The electrode terminal (155) may be a member that is exposed to the internal space (131) of the outer film (130) to be electrically connected to the electrode tab (111) of the electrode assembly (110), and also exposed to the outside of the first member (151). FIG. 6 illustrates an electrode terminal having an I-shaped cross-section. For example, the electrode tabs (111) of the electrode assembly (110) are welded to the inner surface of the electrode terminal (155), and another device (not shown) is electrically connected to the outer surface of the electrode terminal (155), thereby electrically connecting the other device to the electrode assembly (110).

[0129] The first member (151) may include an electrolyte injection hole (not shown) for injecting an electrolyte into the internal space (131) of the outer film (130). Through this, the electrolyte injection process and the degassing process after activation can be performed. For example, the electrolyte can be injected into the internal space (131) of the outer film (130) through the electrolyte injection hole while the secondary battery (100) is positioned so that the first member (151) having the electrolyte injection hole faces upward. During the degassing process, the discharge of internal gas can be induced through the open electrolyte injection hole. After the electrolyte injection and degassing, the electrolyte injection hole can be closed by sealing or welding. Alternatively, it is also possible to install a valve that can be opened and closed in the electrolyte injection hole so that the electrolyte injection hole is opened only when necessary.

[0130] Conventionally, a pouch-type outer casing was provided with a storage portion that accommodates an electrode assembly and a pocket portion that accommodates gas generated during activation, and after the gas in the pocket portion was discharged through a degassing process, the pocket portion was removed. As a result, there was a problem where some of the pouch-type outer casing was always discarded. However, the secondary battery (100) of the present embodiment can perform electrolyte injection and degassing through an electrolyte injection hole, so such disposal of the outer casing may not occur.

[0131] The second member (152) of the cover member (150) may be formed along the edge of the first member (151) as shown in FIG. 6. In order to be firmly bonded with the exterior film (130), the second member (152) may be formed over the entire edge of the first member (151), but it may also be considered to be formed on a part of the edge. FIG. 3 illustrates the second member (152) formed over the entire edge of the first member (151).

[0132] The second member (152) may extend from the first member (151) in a direction facing the internal space (131) (rightward in FIG. 5). The second member (152) may be set to a length that contacts the electrode assembly (110). This may prevent the electrode assembly (110) from moving within the outer film (130).

[0133]

[0134] Second embodiment

[0135] Fig. 10 is a perspective view illustrating a secondary battery (200) according to a second embodiment of the present specification, Fig. 11 is an exploded perspective view of the secondary battery (200) of Fig. 10, and Fig. 12 is a cross-sectional view along line BB of the secondary battery (200) of Fig. 10. Since the secondary battery (200) according to the present embodiment has a difference in the cover member compared to the secondary battery (100) of the first embodiment, the following description will focus on this. For reference, the contents of the second embodiment can be equally applied to the aforementioned embodiments as long as they do not conflict with each other.

[0136] The cover member (250) of the present embodiment may include a first member (251) and a second member (252), as illustrated in FIG. 10. The first member (251) may be a member that blocks a space between the internal space (131) of the outer film (130) and the outer material opening (132). The second member (252) may be formed along the edge of the first member (251), and may extend from the first member (251) in a direction facing the outside of the outer film (130) (left direction in FIG. 11).

[0137] The first member (251) may include a through hole (253) through which an electrode lead (112) electrically connected to the electrode assembly (110) passes. This allows the electrode lead (112) to be easily exposed to the outside when the outer film (130) and the cover member (250) are joined. For example, in a process of joining the cover member (250) to the outer material opening (132) of the outer film (130) while the electrode assembly (110) is accommodated in the inner space (131) of the outer film (130), the electrode lead (112) can be easily exposed to the outside by inserting it into the through hole (253) of the first member (251). For reference, to prevent leakage of the electrolyte through the through hole (253), a sealant layer (not shown) may be provided between the outer surface of the electrode lead (112) and the inner surface of the through hole (253).

[0138] Meanwhile, in order to bond the inner surface of the outer film (130) to the outer surface of the second member (252) via the gasket member (220), it may be necessary to press the outer film (130) toward the second member (252). It may be necessary to support the second member (252) during this pressing. In the case of the secondary battery (200) of the present embodiment, the inner surface of the second member (252) is exposed to the outside of the cover member (250), so that a member for supporting the second member (252) can be easily positioned on the inner surface of the second member (252).

[0139] The contents described in the gasket member (120) of the above-described embodiment can be equally applied to the gasket member (220) of the present embodiment.

[0140]

[0141] Examples and Comparative Examples

[0142] Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are merely illustrative and serve to aid understanding of the present invention and do not limit its scope. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope and technical spirit of this disclosure, and such modifications and variations are naturally within the scope of the appended claims.

[0143]

[0144] Example 1

[0145] A polyethylene terephthalate (PET) film measuring 266 mm wide, 50 m long, and 12 ㎛ thick and a nylon film measuring 266 mm wide, 50 m long, and 25 ㎛ thick were laminated on one side of an aluminum alloy film measuring 266 mm wide, 50 m long, and 60 ㎛ thick, and a polypropylene film measuring 266 mm wide, 50 m long, and 80 ㎛ thick was laminated on the other side, thereby preparing an outer film having a polyethylene terephthalate / nylon / aluminum alloy film / polypropylene film structure. Here, the polyethylene terephthalate film and the nylon film are substrate layers, the aluminum alloy film is a gas barrier layer, and the polypropylene film is a sealant layer.

[0146] Next, a cover member and a gasket member having the same shape as in Fig. 7 were prepared to meet the short-side and long-side specifications of the cover sealing portion described in Table 1 below, and a cover member having a thickness of 1 mm inserted into the inner side of the outer film was used. In addition, a cover member and a gasket member were prepared by insert injection using an aluminum metal plate and polypropylene resin.

[0147] An electrode assembly was prepared by simulating the stacking method of assembling a cathode and anode and a porous polyethylene separator, and after wrapping this with the outer film, a secondary battery having the shape shown in Fig. 2 was manufactured using an assembly of a cover member and a gasket member. At this time, the sealing of the film sealing portion and the cover sealing portion was performed for 5 seconds under the conditions of 240°C and 0.6 MPa, and the sealing length and width were applied as described in Table 1 below.

[0148]

[0149] Examples 2 to 14 and Comparative Examples 1 to 5

[0150] A secondary battery was manufactured in the same manner as in Example 1, except for the secondary battery specifications and sealing specifications listed in Table 1.

[0151]

[0152] Cover sealing part (mm)Film sealing part (mm)Short side L cS Long side L cL Ceiling perimeter P c Ceiling width W c Sealing length L f Ceiling width W f Example 13010026082008 Example 230100260102008 Example 330100260820012 Example 4301002601020012 Example 51550130520012 Example 6305016082008 Example 73010026055008 Example 83010026085008 Example 930100260105008 Example 1030100260550012 Example 1130100260850012 Example 12301002601050012 Example 131550130142004Example 143050130165008Comparative Example 13010026052008Comparative Example 230100260320012Comparative Example 330100260520012Comparative Example 43010026032006Comparative Example 530100260350012

[0153]

[0154] Experimental Example 1: Vent Direction Control and Vent Pressure Evaluation

[0155] For the secondary battery manufactured above, carbon dioxide (CO2) gas was injected into the case at a rate of 50 sccm at 60°C, and the pressure at the time of venting (the pressure here is a measured value that does not take into account the atmospheric pressure of 1 atm) was measured. If the venting occurred in the direction of the film sealing part, it was evaluated as O, and if the venting occurred in the direction of the cover sealing part, it was evaluated as X.

[0156] I DVVent direction controlVent pressure (atm)Example 10.77O3.8Example 20.96O3.8Example 30.51O4.0Example 40.64O4.0Example 50.64O4.0Example 61.25O3.8Example 71.20O3.8Example 81.92O3.8Example 92.40O3.8Example 100.80O4.0Example 111.28O4.0Example 121.60O4.0Example 135.38O3.6Example 147.69O3.8Comparative example 10.48X3.5Comparative example 20.19X3.0Comparative example 30.32X3.5Comparative example 40.38X3.0 Comparative Example 50.48X3.0

[0157] Referring to Table 2 above, in the case of Examples 1 to 14, I DV The vent direction was controlled toward the film sealing part in that the design was controlled to a value of 0.5 or more, but in the case of comparative examples 1 to 5, the vent occurred in the direction of the cover sealing part, and I DV It can be confirmed that the vent direction was not controlled due to the failure to control the value. It can be confirmed that the pressure at which the vent occurs is also relatively low in the case of the comparative examples, and it can be confirmed that the vent pressure can also be controlled by adjusting the IDV. Meanwhile, in the case of Examples 13 and 14, when the sealing width of the film sealing part was minimized to maximize the sealing process, the minimum sealing width of the cover sealing part for vent direction control was applied. In this case, it can be expected that the volume of the cell that can be occupied by the cell in the same space will decrease due to the increase in the sealing width, and it can be confirmed that the vent pressure was also relatively lowered compared to other examples, and therefore, as much as possible, I DV It can be confirmed that controlling the value to 5.0 or less is desirable in terms of energy density.

[0158]

[0159] [Explanation of symbols]

[0160] 100, 200: Secondary battery

[0161] 110: Electrode assembly

[0162] 111: Electrode tab

[0163] 112: Electrode lead

[0164] 120: Gasket absence

[0165] 121: 1st floor

[0166] 122: 2nd floor

[0167] 123: Third floor

[0168] 130: Exterior film

[0169] 130a: Sheet

[0170] 131: Interior space

[0171] 132: Exterior opening

[0172] 135: First terminal

[0173] 136: Second terminal

[0174] 138: Film sealing section

[0175] 150, 250: Cover missing

[0176] 151, 251: First Absence

[0177] 152. 252: Second Absence

[0178] 155: Electrode terminal

[0179] 158: Cover sealing part

Claims

1. Electrode assembly; An outer film having an inner space accommodating the electrode assembly and an outer material opening communicating the inner space with the outside; A cover member covering the opening of the exterior material of the exterior film; and It includes a gasket member disposed between the cover member and the exterior film, and The above gasket member has a plurality of cover sealing portions that come into contact with the exterior film, and The above exterior film is provided with a film sealing portion on one of the surfaces perpendicular to the opening of the exterior material, and I defined by the following Equation 1 DV Secondary battery with a value of 0.5 or higher: [Formula 1] I DV = (W c x L f ) / (P c x W f ) In the above equation 1, W c is the sealing width (mm) of the cover sealing part, and P c is the total sealing length (mm) of the above multiple cover sealing parts, and W f is the sealing width (mm) of the film sealing part, and L f is the sealing length (mm) of the film sealing part.

2. In claim 1, The above I DV A secondary battery with a value of 0.5 to 5.

0.

3. In claim 1, The above outer film, A predetermined sheet having a first end and a second end spaced apart from the first end in a predetermined direction has a rolled or folded shape such that the first end and the second end meet each other. The above film sealing portion is provided at the portion where the first end and the second end meet each other, in a secondary battery.

4. In Claim 1, A secondary battery, wherein the above film sealing portion is provided on a surface corresponding to the thickness of the electrode assembly among the surfaces perpendicular to the opening of the outer material of the outer film.

5. In claim 1, The above W c A secondary battery with a length of 3 mm to 30 mm.

6. In claim 1, The above W f A secondary battery with a length of 5 mm to 20 mm.

7. In claim 3, The inner surface of the first terminal above is, A secondary battery coupled to the inner or outer surface of the second end.

8. In claim 1, The above cover member, A first member blocking the opening of the exterior material; and It includes a second member extending from the first member and positioned opposite to the inner surface of the exterior film, and The above gasket member, A secondary battery disposed between the second member and the inner surface of the outer film.

9. In claim 8, The second member above is, A secondary battery formed along the edge of the first member, extending from the first member in a direction toward the internal space.

10. In claim 8, The second member above is, A secondary battery having a length in contact with the electrode assembly within the outer film.

11. In claim 8, The second member above is, A secondary battery formed along the edge of the first member, extending from the first member in a direction facing the outside.

12. In claim 1, The above cover member, A secondary battery having a through hole through which an electrode lead electrically connected to the above electrode assembly passes.

13. In claim 1, The above gasket member, A secondary battery comprising a first layer having an inner surface that allows coupling with the outer surface of the cover member facing the inner surface of the outer film, and an outer surface that allows coupling with the inner surface of the outer film.

14. In claim 1, The above gasket member, A secondary battery comprising: a first layer that allows bonding with the outer surface of the cover member facing the inner surface of the exterior film; and a second layer laminated on the outer surface of the first layer and allowing bonding with the inner surface of the exterior film.

15. In claim 1, The above gasket member, A secondary battery comprising a first layer allowing bonding with the outer surface of the cover member facing the inner surface of the exterior film, a second layer allowing bonding with the inner surface of the exterior film, and a third layer disposed between the first layer and the second layer.

Images