Soft film laminate and secondary battery

Abstract

The soft envelope laminate according to the present disclosure includes a base material layer, a gas barrier layer, a first sealant layer, and a second sealant layer stacked in this order, in which the elastic modulus of the first sealant layer is greater than the elastic modulus of the second sealant layer. Since the elastic modulus of the first sealant layer is adjusted to be greater than the elastic modulus of the second sealant layer, when a tensile stress is applied to a sealing part of a pouch type battery case prepared from the pouch film laminate, deformation caused by the tensile stress is distributed to the second sealant layer instead of being concentrated in the first sealant layer, and the sealing part of the pouch type battery case is sealed by the pouch film laminate. Therefore, the sealing strength higher than that of the conventional condition can be realized.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from Korean Patent Application No. 10-2023-0013848, filed on February 1, 2023, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a soft-pack film laminate and a soft-pack secondary battery prepared by molding the soft-pack film laminate. Background Art

[0004] Secondary batteries are used in a variety of fields, including small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable gaming devices, power tools, and electric bicycles, as well as large products requiring high output, such as electric and hybrid vehicles, energy storage devices, and backup energy storage devices for storing surplus generated electricity or renewable energy. Types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries.

[0005] A secondary battery can be prepared by housing an electrode assembly in which a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes are alternately stacked in a battery case, injecting an electrolyte, and then sealing the battery case. Depending on the material of the case housing the electrode assembly, secondary batteries are classified into soft-pack secondary batteries, can-type secondary batteries, etc.

[0006] After forming a cup portion by pressing the flexible soft-pack film laminate, the electrode assembly can be housed in the accommodation space inside the cup portion and the sealing portion is sealed to prepare a soft-pack secondary battery. The soft-pack film laminate is composed of a plurality of layers in which a polymer film such as polyethylene terephthalate is laminated on one surface of the metal gas barrier layer and a sealant layer of a thermoplastic polyolefin-based resin is laminated on the other surface. When the soft-pack battery case is sealed, the sealant layers can be thermally bonded to each other to form the sealing portion.

[0007] As the capacity of soft-pack secondary batteries has recently increased, the amount of gas generated within the soft pack during charging and discharging has also increased. If the internal pressure of the soft pack increases above a certain level due to this increase in gas generation, there is a problem of degassing of the seal of the soft-pack secondary battery, which can reduce the durability and safety of the battery. Therefore, there is a need to develop a soft-pack secondary battery with a high seal strength that can prevent degassing even under high internal pressure. Summary of the Invention

[0008] Technical issues

[0009] One aspect of the present disclosure provides a pouch film laminate capable of improving the sealing strength of a pouch by optimizing the elastic modulus of a sealant layer, and a pouch-type battery case and a pouch-type secondary battery prepared by molding the pouch film laminate.

[0010] Technical Solution

[0011] According to an embodiment of the present disclosure, a soft envelope laminate is provided, comprising: a base material layer, a gas barrier layer, a first sealant layer, and a second sealant layer stacked in sequence, wherein the elastic modulus of the first sealant layer is greater than that of the second sealant layer.

[0012] According to the present disclosure, a ratio (B / A) of the elastic modulus (B) of the second sealant layer to the elastic modulus (A) of the first sealant layer may be in a range of 0.65 or more to less than 1.0.

[0013] Furthermore, the elastic modulus of the first sealant layer may be 600 MPa or less, and the elastic modulus of the second sealant layer may be 200 MPa or more.

[0014] According to the present disclosure, the first sealant layer may be in direct contact with the gas barrier layer.

[0015] In one example, the second sealant layer may be in direct contact with the first sealant layer. In another example, the soft envelope laminate may further include at least one layer disposed between the first sealant layer and the second sealant layer.

[0016] The thickness of the first sealant layer according to the present disclosure may be 10 μm to 90 μm, and the thickness of the second sealant layer may be 10 μm to 90 μm.

[0017] The first sealant layer according to the present disclosure may include acid-modified polypropylene (PPa), and the second sealant layer may include polypropylene (PP).

[0018] The gas barrier layer according to the present disclosure may have a thickness of 30 μm to 100 μm, and the gas barrier layer may include aluminum.

[0019] According to another embodiment of the present disclosure, a soft-pack type battery case is provided, which is prepared by molding the soft-pack film laminate.

[0020] According to another embodiment of the present disclosure, a soft-pack secondary battery is provided, including: a soft-pack battery case prepared by molding the soft-pack film laminate; and an electrode assembly accommodated in the soft-pack battery case.

[0021] Beneficial effects

[0022] Because the elastic modulus of the first sealant layer is adjusted to be greater than that of the second sealant layer, when tensile stress is applied to the seal portion of a soft-pack battery case made from a soft-pack film laminate, the deformation caused by the tensile stress is distributed to the second sealant layer rather than being concentrated in the first sealant layer. Therefore, the present disclosure can achieve a higher seal strength than conventional cases. Therefore, even in an environment where internal pressure increases due to gas generation in the soft pack during charge and discharge of the soft-pack secondary battery, the durability and safety of the battery can be improved by suppressing outgassing of the soft pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following drawings attached to the specification illustrate preferred examples of the present disclosure by way of example and are used to enable the technical concept of the present disclosure to be further understood together with the detailed description of the present disclosure given below, and thus the present disclosure should not be interpreted solely by the contents in these drawings.

[0024] Figure 1 is a cross-sectional view of a soft-coat laminate according to the present disclosure.

[0025] Figure 2 1 is an exploded assembly diagram of a soft-pack secondary battery according to the present disclosure. DETAILED DESCRIPTION

[0026] The advantages and features of the present disclosure and their implementation methods will be explained by the following embodiments described with reference to the accompanying drawings. However, the present disclosure can be implemented in different forms and should not be construed as being limited to the embodiments described herein. However, these embodiments are provided so that the present disclosure will become thorough and complete, and will fully convey the scope of the present disclosure to those of ordinary skill in the art. In addition, the present disclosure is limited only by the scope of the claims. Throughout the specification, the same reference numerals represent the same elements.

[0027] Unless otherwise defined, all terms used herein (including technical and scientific terms) may be intended to have the meanings understood by those of ordinary skill in the art. In addition, unless otherwise specifically defined, the terms defined in commonly used dictionaries should not be interpreted abnormally or exaggeratedly.

[0028] The techniques used herein are only for describing specific example embodiments and are not intended to limit the present disclosure. In this specification, unless otherwise specified, terms in the singular may include plural forms. It will also be understood that when used in this specification, the terms "include" and / or "comprising" specify the presence of the components described, but do not exclude the presence or addition of one or more other components.

[0029] In this specification, unless specifically described to the contrary, when it is mentioned that a part includes specific components, this means that other components may also be included, and does not exclude other components.

[0030] The description "A and / or B" in this specification means A, or B, or A and B.

[0031] In this specification, "%" means wt% unless otherwise specifically stated.

[0032] Soft film laminate

[0033] The soft envelope laminate according to the present disclosure includes a base material layer, a gas barrier layer, a first sealant layer, and a second sealant layer stacked in sequence, wherein the elastic modulus of the first sealant layer is greater than that of the second sealant layer.

[0034] Figure 1 is a cross-sectional view of a soft-coated laminate 100 according to the present disclosure. Figure 1 Each configuration of the soft cover laminate 100 of the present disclosure is described in more detail.

[0035] (1) Base material layer

[0036] The base material layer 110 is formed as the outermost layer of the soft package laminate 100 to protect the secondary battery from friction and collision with the outside. The base material layer 110 is formed of a polymer so that it can electrically insulate the electrode assembly from the outside.

[0037] The base material layer 110 may be formed of at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon. It is desirable that the base material layer 110 be formed of polyethylene terephthalate (PET), nylon, or a combination thereof having wear resistance and heat resistance.

[0038] The thickness of the base material layer 110 may be 5 μm to 100 μm, particularly 7 μm to 70 μm, and more particularly 10 μm to 60 μm. When the thickness of the base material layer 110 satisfies the above range, the energy density to volume ratio of the secondary battery may be excellent because the external insulation is excellent and the entire soft pack is not thick.

[0039] The base material layer 110 may have a single layer structure formed of any one material. Alternatively, the base material layer 110 may have a composite layer structure formed by laminating two or more materials. An adhesive layer may be provided between each layer having the composite layer structure.

[0040] Specifically, the base material layer 110 according to the present disclosure may include a first base material layer (not shown) and a second base material layer (not shown). In this case, the first base material layer may be a layer provided as the outermost layer of the soft envelope laminate, and the second base material layer may be a layer provided between the first base material layer and the gas barrier layer 120. The first base material layer and the second base material layer may be formed of materials having different materials and / or physical properties, respectively. An interface may exist between the first base material layer and the second base material layer. This means that the first base material layer and the second base material layer are different layers from each other and can be formed separately.

[0041] The first base material layer can play a role in preventing moisture from penetrating from the outside of the soft bag. The first base material layer can be formed by at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyphenylene benzobisoxazole, polyarylate and Teflon. Preferably, the first base material layer may include a polyester base film having wear resistance and heat resistance. For example, the first base material layer may include at least one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, but is not limited thereto. The thickness of the first base material layer may be 10 μm to 50 μm, particularly 10 μm to 40 μm, more particularly 12 μm to 25 μm. When the thickness of the first base material layer meets the above numerical range, it is possible to effectively inhibit moisture from penetrating into the interior of the soft bag film laminate and ensure the insulation and formability of the soft bag. Furthermore, since the entire pouch is not thick, the energy density to volume ratio of the secondary battery is excellent.

[0042] The second base material layer can play a role in improving the formability of the soft package. The second base material layer may include a polyamide-based film. For example, the second base material layer may include at least one selected from the group consisting of nylon 6, nylon (6,6), nylon MXD6 (polyxylylene adipamide), nylon 4, nylon (4,6) and nylon (4,10), but is not limited thereto. Preferably, the second base material layer may include nylon 6, and in this case, due to the excellent elongation properties of nylon 6, it has the advantage of improving the formability of the soft package. The thickness of the second base material layer may be 10 μm to 50 μm, particularly 10 μm to 40 μm, more particularly 15 μm to 35 μm. When the thickness of the second base material layer meets the above-mentioned numerical range, the energy density to volume ratio of the secondary battery due to the excessive increase in the thickness of the soft package film laminate can be prevented from decreasing, and the formability of the soft package can be ensured.

[0043] The second base material layer may include metal oxide particles. The metal oxide particles may be hydroxylated by reacting with moisture introduced into the second base material layer, thereby removing moisture from the second base material layer. The metal oxide particles may include at least one material selected from the group consisting of CaO, MnO, SrO, MgO, and ZnO. Preferably, the metal oxide particles may include at least one of CaO and MgO that are favorable for hydroxylation with water.

[0044] (2) Gas barrier layer

[0045] The gas barrier layer 120 is laminated between the base material layer 110 and the sealant layer 130 to ensure mechanical strength of the pouch, block entry and exit of gas or moisture from outside the secondary battery, and prevent leakage of electrolyte from inside the pouch type battery case.

[0046] The gas barrier layer 120 may be formed of a metal. For example, the gas barrier layer may be a metal thin film including at least one metal selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and invar (INVAR), but is not limited thereto.

[0047] According to an embodiment of the present disclosure, the gas barrier layer 120 can be formed of an aluminum alloy film. When the gas barrier layer 120 is formed by using an aluminum alloy film, the gas barrier layer 120 is lightweight and ensures mechanical strength higher than a predetermined level, electrochemical performance can be compensated by the electrode assembly and the electrolyte, and heat dissipation performance can be ensured. The aluminum alloy film may contain elements other than aluminum (Al). For example, the aluminum alloy film may contain at least one selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si) and zinc (Zn).

[0048] In another example, the gas barrier layer 120 may be formed of a stainless steel film. Specifically, the gas barrier layer 120 may be prepared by molding and / or processing a stainless steel film. Since the gas barrier layer 120 formed of stainless steel has a relatively low thermal conductivity, it effectively prevents or delays the diffusion of heat to other battery cells during thermal runaway, and since it has a relatively high toughness, it can inhibit the generation of cracks in the soft pack during the use of the soft pack type battery. Stainless steel may contain elements other than iron (Fe), for example, at least one selected from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si) and zinc (Zn).

[0049] The thickness of the gas barrier layer 120 may be 30 to 100 μm, specifically 30 to 90 μm, and more specifically 40 to 80 μm. When the thickness of the gas barrier layer 120 satisfies the above range, gas barrier properties and moldability are excellent when the cup portion is molded.

[0050] (3) Sealant layer

[0051] When sealing the pouch-type battery case housing the electrode assembly, the sealant layer 130 is used to completely seal the interior of the pouch-type battery case by thermally bonding each other at the sealing portion. To this end, the sealant layer 130 may be formed of a material having excellent thermal bonding strength.

[0052] The sealant layer 130 can be formed of a material having insulation, corrosion resistance and sealing properties. Specifically, since the sealant layer 130 is in direct contact with the electrode assembly and / or the electrolyte inside the soft-pack battery case, the sealant layer 130 can be formed of a material having insulation and corrosion resistance. In addition, since the sealant layer 130 completely seals the interior of the soft-pack battery case to prevent the material from moving between the inside / outside, the sealant layer 130 can be formed of a material having high sealing properties (e.g., excellent thermal bonding strength). In order to ensure such insulation, corrosion resistance and sealing properties, the sealant layer 130 can be formed of a polymer material.

[0053] The sealant layer 130 may be formed of at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyphenylene benzobisoxazole, polyarylate, and Teflon, and may preferably be formed of a polyolefin-based resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene (PP) may be composed of cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer.

[0054] The thickness of the sealant layer 130 may be 30 to 130 μm, particularly 50 to 120 μm, and more particularly 70 to 100 μm. When the thickness of the sealant layer satisfies the above range, the formability of the soft film laminate and the sealing strength of the sealing portion are ensured.

[0055] The sealant layer 130 according to the present disclosure may have a composite layer structure formed by laminating two or more materials separately. For example, the sealant layer 130 may have a multilayer structure. An adhesive layer and / or a surface layer may be provided between the layers of the sealant layer 130 having the composite layer structure. Since the adhesive layer and / or the surface layer have thermal adhesive properties, the adhesive layer and / or the surface layer may play a role in assisting the adhesion between the layers of the sealant layer 130. For example, the adhesive layer and / or the surface layer may contain a polypropylene-based resin, but is not limited thereto. In addition, the adhesive layer and / or the surface layer may be provided between the sealant layer 130 and the gas barrier layer 120.

[0056] Specifically, the sealant layer 130 according to the present disclosure includes a first sealant layer 132 and a second sealant layer 134. For example, the sealant layer 130 can be composed of the first sealant layer 132 and the second sealant layer 134. As another example, in addition to the first sealant layer 132 and the second sealant layer 134, the sealant layer 130 can also include a third sealant layer and / or a fourth sealant layer. The individual layers of the sealant layer 130, including the first sealant layer 132 and the second sealant layer 134, can be formed of materials having different materials and / or physical properties. There may be an interface between the various layers included in the sealant layer 130. This means that the various layers are different layers from each other and can be formed separately.

[0057] According to the present disclosure, the elastic modulus of the first sealant layer 132 is greater than the elastic modulus of the second sealant layer 134. When the elastic modulus of the first sealant layer 132 is smaller than the elastic modulus of the second sealant layer 134, when tensile stress is applied to the seal portion of the soft-pack-type battery case made of the soft-pack film laminate, deformation may be concentrated in the first sealant layer 132 adjacent to the gas barrier layer 120. Therefore, due to delamination at the interface between the gas barrier layer 120 and the first sealant layer 132 before the sealant layer 130 is ruptured, there is a problem of reduced sealing strength of the soft-pack-type battery case.

[0058] The ratio (B / A) of the elastic modulus (B) of the second sealant layer 134 to the elastic modulus (A) of the first sealant layer 132 is in the range of 0.65 or more and less than 1.0, particularly 0.8 or more and less than 1.0, and more particularly 0.9 or more and less than 1.0. When the elastic modulus ratio (B / A) between the sealant layers satisfies the above numerical range, the possibility of interlayer delamination at the interface between the first sealant layer 132 and the second sealant layer 134 during the application of tensile stress is reduced, and the deformation caused by the tensile stress is not concentrated in the first sealant layer 132 but is distributed to the second sealant layer 134 having a mechanical strength above a certain level. Therefore, a higher soft package sealing strength than conventional cases can be achieved.

[0059] In order to adjust the physical properties of first sealant layer 132 and / or second sealant layer 134 to desired values, an additive may be added to the polymer material constituting first sealant layer 132. Specifically, a flexibility additive may be added as an additive for reducing the elastic modulus of first sealant layer 132. The flexibility additive may be at least one selected from the group consisting of linear low-density polyethylene (LLDPE), polybutylene, and polyethylene (PE)-polypropylene (PP)-polybutylene (PB) terpolymer, but is not limited thereto. As an additive for increasing the elastic modulus of first sealant layer 132, for example, at least one material selected from carbon fiber, glass fiber, and aramid fiber may be added.

[0060] In order to adjust the physical properties of the first sealant layer 132 and / or the second sealant layer 134 to desired values, an additive may be added to the polymer material constituting the first sealant layer 132 and / or the second sealant layer 134. Specifically, a flexibility additive may be added as an additive for reducing the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134. The flexibility additive may be at least one material selected from the group consisting of linear low-density polyethylene (LLDPE), polybutylene, and polyethylene (PE)-polypropylene (PP)-polybutylene (PB) terpolymer, but is not limited thereto. As an additive for increasing the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134, for example, at least one material selected from carbon fiber, glass fiber, and aramid fiber may be added.

[0061] Furthermore, in order to control the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134, the molecular weight and / or melt flow rate (MFR) of the polymer included in the first sealant layer 132 and / or the second sealant layer 134 may be changed. For example, if the molecular weight of the polymer included in the first sealant layer 132 and / or the second sealant layer 134 is increased or the melt flow rate is decreased, the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134 may be increased. Furthermore, if the molecular weight of the polymer included in the first sealant layer 132 and / or the second sealant layer 134 is decreased or the melt flow rate is increased, the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134 may be decreased.

[0062] Hereinafter, each of the above-mentioned first sealant layer 132 and second sealant layer 134 will be described in more detail.

[0063] 1) First sealant layer

[0064] The first sealant layer 132 may be formed of a polymer material. Specifically, the first sealant layer 132 may be formed of at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyphenylene benzobisoxazole, polyarylate, and Teflon, and may preferably be formed of a polyolefin-based resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene (PP) may be composed of cast polypropylene (CPP), acid-modified polypropylene (PPa), or polypropylene-butylene-ethylene terpolymer.

[0065] In order to ensure long-term adhesion between the gas barrier layer 120 and the first sealant layer 132, it is particularly desirable that the first sealant layer 132 is formed of acid-modified polypropylene (PPa). Herein, the acid-modified polypropylene may be maleic anhydride polypropylene (MAH PP).

[0066] The elastic modulus of the first sealant layer 132 may be 600 MPa or less, particularly 200 MPa to 500 MPa, and more particularly 250 MPa to 480 MPa. When the elastic modulus of the first sealant layer 132 satisfies the above numerical range, since the first sealant layer 132 is not easily deformed, the interface delamination between the gas barrier layer 120 and the first sealant layer 132 is suppressed, and since the first sealant layer 132 is easily attached to the gas barrier layer 120, the adhesion between the gas barrier layer 120 and the first sealant layer 132 can be maintained high. In addition, since the first sealant layer 132 has appropriate flexibility and impact resistance, the insulation of the soft-pack battery case can be maintained.

[0067] The thickness of the first sealant layer 132 may be 10 μm to 90 μm, particularly 10 μm to 60 μm, more particularly 10 μm to 40 μm. In the case where the thickness of the first sealant layer 132 is less than 10 μm, since the sealing durability and insulation of the soft-pack type battery case prepared by the soft-pack film laminate are reduced and the yield strength of the first sealant layer 132 is reduced, there is a problem of reduced sealing strength of the soft-pack type battery case. In addition, there is a problem that it is difficult to extrude the first sealant layer into a uniform thickness through an extrusion process. In the case where the thickness of the first sealant layer 132 is greater than 90 μm, since the thickness of the soft-pack film laminate is increased relative to the total thickness of the soft-pack type secondary battery, there is a problem of reduced energy density of the soft-pack type secondary battery.

[0068] According to an embodiment of the present disclosure, the first sealant layer 132 may be a layer that is in direct contact with the gas barrier layer 120. In this case, if the soft envelope laminate 100 is coextruded, the first sealant layer 132 may be directly bonded to the gas barrier layer 120. In another example, an adhesive layer and / or a skin layer may be provided between the first sealant layer 132 and the gas barrier layer 120 to improve adhesion therebetween.

[0069] 2) Second sealant layer

[0070] The second sealant layer 134 may be formed of a material having insulation, corrosion resistance, and sealing properties. Figure 2 The electrode assembly (224) inside Figure 2 260) and / or electrolyte are in direct contact, so the second sealant layer 134 can be formed of a material with insulation and corrosion resistance. In addition, since the second sealant layer 134 completely seals the interior of the battery housing to prevent material from moving between the inside / outside, the second sealant layer 134 can be formed of a material with high sealing. In order to ensure such insulation, corrosion resistance and sealing, the second sealant layer 134 can be formed of at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyphenylene benzobisoxazole, polyarylate and Teflon. Preferably, the second sealant layer 134 can be formed of a polyolefin-based resin such as polypropylene (PP) and / or polyethylene (PE). In this case, polypropylene can be made of cast polypropylene, acid-modified polypropylene, polypropylene ethylene copolymer and / or polypropylene-butene-ethylene terpolymer. Herein, the acid-modified polypropylene may be maleic anhydride polypropylene (MAH PP). More preferably, the second sealant layer may include cast polypropylene (CPP) having high tensile strength and heat sealability.

[0071] The elastic modulus of the second sealant layer 134 may be 200 MPa or more, particularly 200 MPa to 400 MPa, more particularly 250 MPa to 380 MPa. When the elastic modulus of the second sealant layer 134 satisfies the above numerical range, the interface delamination between the first sealant layer 132 and the second sealant layer 134 is suppressed, and the sealing durability of the soft-pack battery case can be ensured by reducing the possibility of rupture along a pair of second sealant layers 134 sealed in a soft-pack battery case prepared by a soft-pack film laminate. In addition, since the mechanical strength of the second sealant layer 134 is sufficiently ensured to fully withstand stress, the sealing durability of the soft-pack battery case can be ensured.

[0072] The thickness of the second sealant layer 134 may be 10 μm to 90 μm, particularly 10 μm to 60 μm, and more particularly 10 μm to 50 μm. In the case where the thickness of the second sealant layer 134 is less than 10 μm, there is a problem of reduced sealing strength of the soft-pack battery case due to reduced sealing durability and insulation of the soft-pack battery case prepared by the soft-pack film laminate and reduced yield strength of the second sealant layer 134. In the case where the thickness of the second sealant layer 134 is greater than 90 μm, there is a problem of reduced energy density of the soft-pack secondary battery due to the increase in the thickness of the soft-pack film laminate relative to the total thickness of the soft-pack secondary battery.

[0073] The second sealant layer 134 may be arranged to be in direct contact with the first sealant layer 132, or may be arranged not to be in direct contact with the first sealant layer 132. In the case where the second sealant layer 134 and the first sealant layer 132 are not in direct contact with each other, the soft envelope laminate may further include at least one layer arranged between the first sealant layer 132 and the second sealant layer 134. For example, an intermediate layer (not shown) may be provided between the first sealant layer 132 and the second sealant layer 134 to improve the insulation properties of the soft envelope laminate. The intermediate layer may include at least one of polypropylene and homopolypropylene. The thickness of the intermediate layer may be less than 80 μm, particularly 10 μm to 60 μm, more particularly 30 μm to 50 μm. When the thickness of the intermediate layer meets the above-mentioned numerical range, excellent sealing strength can be ensured and the co-extrusion moldability of the sealant layer can be improved.

[0074] Soft-pack secondary batteries

[0075] Next, a pouch-type secondary battery according to the present disclosure will be described.

[0076] The soft-pack secondary battery according to the present disclosure includes a soft-pack battery case prepared by molding the soft-pack film laminate and an electrode assembly housed in the soft-pack battery case. Specifically, the soft-pack secondary battery according to the present disclosure includes a soft-pack battery case housing an electrode assembly, the soft-pack battery case being prepared by molding the soft-pack film laminate, and the soft-pack film laminate including a base material layer, a gas barrier layer, a first sealant layer, and a second sealant layer stacked in sequence, wherein the elastic modulus of the first sealant layer is greater than the elastic modulus of the second sealant layer.

[0077] In the following, reference will be made to Figure 2 Each configuration of the pouch-type secondary battery of the present disclosure is described in more detail.

[0078] Figure 2 FIG is an exploded assembly diagram of a soft-pack type secondary battery 200 according to the present disclosure. Figure 2As shown, the pouch-type secondary battery 200 of the present disclosure may include a pouch-type battery case 210 , an electrode assembly 260 , an electrode lead 280 , an insulating portion 290 , and an electrolyte (not shown).

[0079] (1) Soft-pack battery case

[0080] The soft-pack type battery case 210 can be prepared by molding the soft-pack film laminate of the present disclosure. The inside of the soft-pack type battery case 210 can accommodate the electrode assembly 260. Since the detailed configuration and physical properties of the soft-pack film laminate are the same as above, detailed description is omitted.

[0081] The soft-pack film laminate can be pulled out and stretched by a punch or the like to prepare a soft-pack type battery case 210. Therefore, the soft-pack type battery case 210 may include a cup portion 222 and a receiving portion 224. The receiving portion 224 is a location for receiving the electrode assembly, wherein it may refer to a receiving space formed in the shape of a pocket inside the cup portion 222 as the cup portion 222 is formed.

[0082] According to an embodiment of the present disclosure, the soft pack type battery case 210 may include a first case 220 and a second case 230. Figure 2 As shown. The first shell 220 includes a receiving portion 224 capable of receiving the electrode assembly 260, and the second shell 230 can cover the receiving portion 224 from the top so that the electrode assembly 260 will not be separated from the outside of the battery shell 210. Figure 2 As shown, the first shell 220 and the second shell 230 can be prepared by connecting one side thereof to each other, but the present disclosure is not limited thereto, and the first shell 220 and the second shell 230 can be prepared in various ways, for example, the first shell 220 and the second shell 230 are separated from each other and manufactured separately.

[0083] According to another embodiment of the present disclosure, in the case where a cup portion is formed on a soft film laminate, two symmetrical cup portions 222 and 232 can be drawn out adjacent to each other on one soft film laminate. Figure 2As shown, cup portions 222 and 223 can be formed in the first shell 220 and the second shell 230, respectively. After the electrode assembly 260 is accommodated in the accommodating portion 224 provided in the cup portion 222 of the first shell 220, the bridge portion 240 formed between the two cup portions 222 and 232 can be folded so that the two cup portions 222 and 232 face each other. In this case, the cup portion 232 of the second shell 230 can accommodate the electrode assembly 260 from above. Therefore, since the two cup portions 222 and 232 accommodate one electrode assembly 260, an electrode assembly 260 with a greater thickness than that of a single cup portion 222 can be accommodated. In addition, since one edge of the secondary battery 200 is formed by folding the soft-pack battery case 210, the number of edges to be sealed can be reduced when the sealing process is performed later. Therefore, the process speed of the soft-pack secondary battery 200 can be increased, and the number of sealing processes can be reduced.

[0084] The soft pack type battery case 210 can be sealed in a state where it accommodates the electrode assembly 260, so that a portion of the electrode lead 280, that is, the terminal portion, which will be described later, is exposed. Specifically, when the electrode lead 280 is connected to the electrode tab 270 of the electrode assembly 260 and the insulating portion 290 is formed at a portion of the electrode lead 280, the electrode assembly 260 is accommodated in the accommodation portion 224 provided in the cup portion 222 of the first case 220, and the second case 230 can cover the accommodation portion 224 from the top. Subsequently, the electrolyte is injected into the accommodation portion 224, and the sealing portion 250 formed at the edge of the first case 220 and the second case 230 can be sealed.

[0085] The sealing portion 250 may be used to seal the accommodating portion 224. Specifically, the sealing portion 250 may be formed along the edge of the accommodating portion 224 and seal the accommodating portion 224. The temperature at which the sealing portion 250 is sealed may be in the range of 180°C to 250°C, particularly 200°C to 250°C, and more particularly 210°C to 240°C. When the sealing temperature satisfies the above numerical range, the soft pack type battery case 210 may ensure sufficient sealing strength through thermal bonding.

[0086] (2) Electrode assembly

[0087] The electrode assembly 260 may be inserted into the pouch type battery case 210 and may be sealed by the pouch type battery case 210 after injecting an electrolyte.

[0088] The electrode assembly 260 may be formed by sequentially stacking a positive electrode, a separator, and a negative electrode. Specifically, the electrode assembly 260 may include two types of electrodes, such as a positive electrode and a negative electrode, and a separator disposed between the electrodes to insulate the electrodes from each other.

[0089] The positive and negative electrodes may each be constructed by applying an active material slurry to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper. Typically, the slurry is formed by stirring particulate active material, an auxiliary conductor, a binder, and a conductive agent in the presence of a solvent. The solvent may be removed in a subsequent step.

[0090] A slurry in which an electrode active material, a binder, and / or a conductive agent are mixed is applied to a positive electrode collector and a negative electrode collector to prepare a positive electrode and a negative electrode, and the positive electrode and the negative electrode can be stacked on both sides of a separator to prepare an electrode assembly 260 in a predetermined shape. Types of the electrode assembly 260 may include a stacking type, a winding type, and a stacking folding type, but are not limited thereto.

[0091] The electrode assembly 260 may include an electrode tab 270 .

[0092] The electrode terminal tab 270 is connected to each of the positive electrode and the negative electrode of the electrode assembly 260 and protrudes from the electrode assembly 260 to the outside, so that it can be a path through which electrons can move between the inside and the outside of the electrode assembly 260. The electrode current collector included in the electrode assembly 260 may be composed of a portion coated with an electrode active material and an end portion (i.e., a non-coating portion) that is not coated with the electrode active material. The electrode terminal tab 270 may be formed by cutting the non-coating portion, or may be formed by connecting a separate conductive member to the non-coating portion by ultrasonic welding or the like. As Figure 2 As shown, the electrode tabs 270 may protrude in different directions of the electrode assembly 260, respectively, but are not limited thereto, and may be formed to protrude in various directions, for example, the electrode tabs 270 protrude side by side from one side of the electrode assembly 260 in the same direction.

[0093] (3) Electrode leads

[0094] The electrode lead 280 may supply power to the outside of the secondary battery 200. The electrode lead 280 may be connected to the electrode tab 270 of the electrode assembly 260 by spot welding or the like.

[0095] The electrode lead 280 is connected to the electrode assembly 260 and may protrude to the outside of the soft-pack type battery case 210 via the sealing portion 250. Specifically, one end of the electrode lead 280 is connected to the electrode assembly 260, particularly the electrode tab 270, and the other end of the electrode lead 280 may protrude to the outside of the soft-pack type battery case 210.

[0096] Electrode lead 280 may include a positive electrode lead 282, one end of which is connected to positive electrode tab 272 and extends in the direction in which positive electrode tab 272 protrudes; and a negative electrode lead 284, one end of which is connected to negative electrode tab 271 and extends in the direction in which negative electrode tab 271 protrudes. The other ends of both positive electrode lead 282 and negative electrode lead 284 may protrude outside of battery case 210. Thus, electricity generated within electrode assembly 260 can be supplied to the outside. Furthermore, since positive electrode tab 272 and negative electrode tab 271 are formed to protrude in various directions, positive electrode lead 282 and negative electrode lead 284 may also extend in various directions. The materials of positive electrode lead 282 and negative electrode lead 284 may be different from each other. That is, the positive electrode lead 282 can be formed of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead 284 can be formed of the same copper (Cu) material or nickel (Ni) coated copper material as the negative electrode current collector. Since a portion of the electrode lead 280 protruding to the outside of the battery case 210 becomes a terminal portion, it can be electrically connected to an external terminal.

[0097] (4) Insulation

[0098] The insulating portion 290 prevents the electricity generated from the electrode assembly 260 from flowing to the battery case 210 through the electrode lead 280 and can maintain the sealing of the battery case 210. To this end, the insulating portion 290 can be formed of an insulator having non-conductivity that does not conduct electricity well. Generally, as the insulating portion 290, an insulating tape or film that is easily attached to the electrode lead 280 and is relatively thin is widely used, but the present disclosure is not limited thereto, and any member that can insulate the electrode lead 280 can be used.

[0099] The insulating portion 290 may be provided to surround the outer peripheral surface of the electrode lead 280. Specifically, at least a portion of the electrode lead 280 may be surrounded by the insulating portion 290. In this case, the insulating portion 290 may be provided between the electrode lead 280 and the soft-pack type battery case 210. The insulating portion 290 may be limitedly located at the sealing portion 250, and the first shell 220 and the second shell 230 of the soft-pack type battery case 210 are heat-welded to the sealing portion 250, and the electrode lead 280 may be bonded to the battery case 210.

[0100] (5) Electrolyte

[0101] The soft-pack secondary battery 200 according to the present disclosure may further include an electrolyte (not shown) injected into the soft-pack battery case 210. The electrolyte is used to move lithium ions generated by the electrochemical reaction of the electrodes during the charge and discharge of the secondary battery 200, wherein the electrolyte may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and an organic solvent or a polymer electrolyte. In addition, the electrolyte may include a sulfide-based, oxide-based, or polymer-based solid electrolyte, and the solid electrolyte may have flexibility that is easily deformed by external forces.

[0102] Hereinafter, the present disclosure will be described in detail based on specific examples. However, the following examples are only used to illustrate the present disclosure, and the scope of the present disclosure is not limited thereto. It is obvious to those skilled in the art that various modifications and variations can be made within the scope and technical spirit of the present disclosure. Such modifications and variations fall within the scope of the claims included herein.

[0103] Examples and Comparative Examples

[0104] Example 1: Preparation of soft film laminate

[0105] A first adhesive film having a thickness of 3 μm, a nylon film having a thickness of 25 μm, a second adhesive film having a thickness of 3 μm, and a polyethylene terephthalate (PET) film having a thickness of 12 μm were sequentially laminated on one surface of a 60 μm thick aluminum alloy film. A 40 μm thick acid-modified polypropylene (PPa) film and a 40 μm thick polypropylene (PP) film were coextruded on the other surface of the aluminum alloy film. Thus, a soft envelope film laminate having a structure in which polypropylene film / acid-modified polypropylene film / aluminum alloy film / first adhesive film / nylon film / second adhesive film / polyethylene terephthalate film were sequentially laminated was prepared.

[0106] Herein, the polypropylene film (second sealant layer) and the acid-modified polypropylene film (first sealant layer) are sealant layers, the aluminum alloy film is a gas barrier layer, and the first adhesive film, nylon film, second adhesive film and polyethylene terephthalate film are base material layers.

[0107] In order to control the elastic modulus of the polypropylene film and the acid-modified polypropylene film, linear low-density polyethylene (LLDPE) was added as a flexibility additive during the preparation of each film.

[0108] Example 2: Preparation of soft film laminate

[0109] A soft package laminate was prepared in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to lower the elastic modulus of the acid-modified polypropylene film (first sealant layer).

[0110] Example 3: Preparation of soft film laminate

[0111] The amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). A soft coating laminate was prepared in the same manner as in Example 1, except that a 30 μm thick acid-modified polypropylene film, a 30 μm thick polypropylene film (intermediate layer), and a 20 μm thick polypropylene film were co-extruded on the other surface of the aluminum alloy film.

[0112] Example 4: Preparation of soft film laminate

[0113] The amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). A soft coating laminate was prepared in the same manner as in Example 1, except that an acid-modified polypropylene film having a thickness of 20 μm, a polypropylene film having a thickness of 50 μm (intermediate layer), and a polypropylene film having a thickness of 10 μm were co-extruded on the other surface of the aluminum alloy film.

[0114] Example 5: Preparation of soft film laminate

[0115] The amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). A soft coating laminate was prepared in the same manner as in Example 1, except that an acid-modified polypropylene film having a thickness of 20 μm, a polypropylene film having a thickness of 50 μm (intermediate layer), and a polypropylene film having a thickness of 10 μm were co-extruded on the other surface of the aluminum alloy film.

[0116] Example 6: Preparation of soft film laminate

[0117] A soft package laminate was prepared in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to lower the elastic modulus of the acid-modified polypropylene film (first sealant layer).

[0118] Example 7: Preparation of soft film laminate

[0119] The amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). A soft coating laminate was prepared in the same manner as in Example 1, except that an acid-modified polypropylene film having a thickness of 20 μm, a polypropylene film having a thickness of 50 μm (intermediate layer), and a polypropylene film having a thickness of 10 μm were co-extruded on the other surface of the aluminum alloy film.

[0120] Example 8: Preparation of soft film laminate

[0121] A polypropylene film having a high melt flow rate (MFR) and an acid-modified polypropylene film were used to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer) and the polypropylene film (second sealant layer). A soft coating laminate was prepared in the same manner as in Example 1, except that an acid-modified polypropylene film having a thickness of 30 μm and a polypropylene film having a thickness of 50 μm were coextruded on the other surface of the aluminum alloy film.

[0122] Example 9: Preparation of soft film laminate

[0123] An acid-modified polypropylene film with a high melt flow rate (MFR) was used to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). A soft-coat laminate was prepared in the same manner as in Example 1, except that an acid-modified polypropylene film with a thickness of 30 μm and a polypropylene film with a thickness of 50 μm were coextruded on the other surface of the aluminum alloy film.

[0124] Comparative Example 1: Preparation of soft film laminate

[0125] An acid-modified polypropylene film having a high melt flow rate (MFR) was used to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer), and a soft coating laminate was prepared in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased.

[0126] Comparative Example 2: Preparation of soft film laminate

[0127] The amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). The amount of linear low-density polyethylene (LLDPE) added to the polypropylene film was reduced to increase the elastic modulus of the polypropylene film (intermediate layer). A soft film laminate was prepared in the same manner as in Example 3, except that a polypropylene film with a low melt flow rate (MFR) was used to increase the elastic modulus of the polypropylene film (second sealant layer).

[0128] Comparative Example 3: Preparation of soft film laminate

[0129] A soft coat laminate was prepared in the same manner as in Example 1, except that an acid-modified polypropylene film having a high melt flow rate (MFR) was used to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer).

[0130] Comparative Example 4: Preparation of soft film laminate

[0131] The amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). A soft film laminate was prepared in the same manner as in Example 1, except that a polypropylene film with a low melt flow rate (MFR) was used to increase the elastic modulus of the polypropylene film (second sealant layer).

[0132] Comparative Example 5: Preparation of soft film laminate

[0133] A soft package laminate was prepared in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to lower the elastic modulus of the acid-modified polypropylene film (first sealant layer).

[0134] Comparative Example 6: Preparation of soft film laminate

[0135] The amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer). The amount of linear low-density polyethylene (LLDPE) added to the polypropylene film was reduced to increase the elastic modulus of the polypropylene film (intermediate layer). A soft film laminate was prepared in the same manner as in Example 3, except that a polypropylene film with a low melt flow rate (MFR) was used to increase the elastic modulus of the polypropylene film (second sealant layer).

[0136] Comparative Example 7: Preparation of soft film laminate

[0137] A soft package laminate was prepared in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was reduced to increase the elastic modulus of the acid-modified polypropylene film (first sealant layer).

[0138] Comparative Example 8: Preparation of soft film laminate

[0139] A soft envelope laminate was prepared in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film and the polypropylene film was increased to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer) and the polypropylene film (second sealant layer), respectively.

[0140] Experimental Example 1: Measurement of the elastic modulus of the sealant layer included in the soft film laminate

[0141] In the soft-coat film laminates prepared in Examples 1 to 9 and Comparative Examples 1 to 8, the elastic modulus of each sealant layer in the thickness direction was measured using a compressive elastic modulus tester (microindenter). Specifically, one surface of each sealant layer was indented to a depth of 10 μm using the microindenter's probe at an indentation loading rate of 0.1 N / min. The elastic modulus was calculated from the stress-strain curves obtained in this manner and is presented in Table 1 below.

[0142] [Table 1]

[0143]

[0144]

[0145] Experimental Example 2: Measuring the sealing strength of soft-pack battery cases

[0146] The soft-coat film laminates prepared in Examples 1 to 9 and Comparative Examples 1 to 8, respectively, were prepared. Thereafter, each soft-coat film laminate was cut into a size of 266 mm in width and 200 mm in length, and then folded in half into a size of 133 mm × 200 mm so that the sealant layers were in contact with each other. Then, a soft-pack type battery case was prepared by sealing the end of the long side (200 mm) at a sealing strip area of 200 mm × 8 mm, 210°C, and a surface pressure of 1.0 MPa to 0.2 MPa for 1.6 seconds.

[0147] Next, the prepared soft-pack type battery case is cut into a width of 15 mm to include the sealing portion. One end of each soft-pack film laminate stacked vertically in the cut sample is bent and fastened to the upper clamp / lower clamp of the measuring equipment (UTM, Zwick), and then stretched at a speed of 5 mm / min in the vertical direction (180° direction) at a temperature of 25°C to measure the maximum value of the tensile strength when the seal is broken. The measurement results are shown in Table 2 below.

[0148] [Table 2]

[0149]

[0150]

[0151] According to Tables 1 and 2, based on Examples 1 to 9 in which the elastic modulus of the first sealant layer is larger than that of the second sealant layer, it can be confirmed that the sealing strength measured at 25° C. is significantly higher than that in Comparative Examples 1 to 8.

[0152] (Explanation of Reference Numerals)

[0153] 100: Soft film laminate

[0154] 110: Base material layer

[0155] 120: Gas barrier layer

[0156] 130: Sealant layer

[0157] 132: First sealant layer

[0158] 134: Second sealant layer

[0159] 200: Soft pack secondary battery

[0160] 210: Soft pack battery case

[0161] 220: First shell

[0162] 222: Cup Department

[0163] 224: Accommodation

[0164] 230: Second shell

[0165] 232: Cup Department

[0166] 240: Bridge

[0167] 250: Sealing part

[0168] 260: Electrode assembly

[0169] 270: Electrode terminal

[0170] 271: Negative terminal lug

[0171] 272: Positive terminal lug

[0172] 280: Electrode lead

[0173] 282: Positive lead

[0174] 284: Negative lead

[0175] 290: Insulation

Claims

1. A soft film laminate comprising: A base material layer, a gas barrier layer, a first sealant layer, and a second sealant layer are sequentially stacked, wherein the elastic modulus of the first sealant layer is greater than the elastic modulus of the second sealant layer.

2. The soft-coated laminate according to claim 1, wherein A ratio (B / A) of the elastic modulus (B) of the second sealant layer to the elastic modulus (A) of the first sealant layer is in a range of 0.65 or more and less than 1.

0.

3. The soft-coated laminate according to claim 1, wherein The elastic modulus of the first sealant layer is 600 MPa or less.

4. The soft-coated laminate according to claim 1, wherein The elastic modulus of the second sealant layer is 200 MPa or more.

5. The soft-coated laminate according to claim 1, wherein The first sealant layer is in direct contact with the gas barrier layer. The soft-coated laminate according to claim 1 , wherein: The second sealant layer is in direct contact with the first sealant layer. 7 . The soft cover laminate according to claim 1 , further comprising at least one layer provided between the first sealant layer and the second sealant layer.

8. The soft-coated laminate according to claim 1, wherein The first sealant layer has a thickness of 10 μm to 90 μm.

9. The soft-coated laminate according to claim 1, wherein The second sealant layer has a thickness of 10 μm to 90 μm.

10. The soft-coated laminate according to claim 1, wherein The first sealant layer includes acid-modified polypropylene (PPa).

11. The soft-coated laminate according to claim 1, wherein The second sealant layer comprises polypropylene (PP).

12. The soft-coated laminate according to claim 1, wherein The gas barrier layer has a thickness of 30 μm to 100 μm.

13. The soft-coated laminate according to claim 1, wherein The gas barrier layer comprises aluminum. 14 . A soft-pack battery case, produced by molding the soft-pack film laminate according to claim 1 .

15. A soft-pack secondary battery comprising: A soft-pack battery case, prepared by molding the soft-pack film laminate according to any one of claims 1 to 13; as well as An electrode assembly is housed in the pouch-type battery case.

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