KR20210017557A - The Case For Secondary Battery And The Pouch Type Secondary Battery - Google Patents

Abstract

According to an embodiment of the present invention, provided is a battery case for a secondary battery, which is a pouch-type battery case for accommodating an electrode assembly formed by stacking a cathode, a separator, and an anode. The battery case comprises: a gas barrier layer formed of a metal; a surface protective layer formed of a first polymer and disposed at an outer layer of the gas barrier layer; a sealant layer formed of a second polymer and disposed at an inner layer of the gas barrier layer; and a flame retardant film layer having flame retardancy and disposed at an outer layer of the surface protective layer or at an inner layer of the sealant layer, wherein the flame retardant film layer includes: a microcapsule in which a shell formed of a third polymer surrounds a core including a flame retardant; and a polymer substrate formed of a fourth polymer and in which the microcapsule is applied to at least one surface thereof or included therein. According to the present invention, safety can be ensured by preventing the spread of a fire to other secondary batteries.

Description

The Case For Secondary Battery And The Pouch Type Secondary Battery}

The present invention relates to a battery case and a pouch-type secondary battery for a secondary battery, and more particularly, even if an explosion or fire occurs due to abnormal operations such as internal short circuit, external short circuit, overcharge, overdischarge, etc. It relates to a battery case and pouch-type secondary battery for secondary batteries that can secure safety by preventing the spread of fire.

In general, types of secondary batteries include nickel cadmium batteries, nickel hydride batteries, lithium ion batteries, and lithium ion polymer batteries. These secondary batteries are not only small products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and E-bikes, but also large-scale products requiring high output such as electric vehicles and hybrid vehicles, and surplus power generation. It is also applied and used in power storage devices for storing electric power or renewable energy and power storage devices for backup.

In order to manufacture an electrode assembly, a cathode, a separator, and an anode are manufactured, and these are stacked. Specifically, a positive electrode active material slurry is applied to a positive electrode current collector, and a negative electrode active material slurry is applied to a negative electrode current collector to prepare a cathode and a negative electrode. In addition, when a separator is interposed between the prepared anode and the cathode to be stacked, unit cells are formed, and the unit cells are stacked on top of each other to form an electrode assembly. In addition, when such an electrode assembly is accommodated in a specific case and an electrolyte is injected, a secondary battery is manufactured.

However, when the secondary battery is exposed to high temperatures or operates abnormally, such as an internal short circuit, an external short circuit, overcharge or overdischarge, the separator shrinks due to heat generated as the organic electrolyte is decomposed, and the positive electrode and the negative electrode directly contact each other, causing a short circuit Short) is more likely to occur. Due to such a short circuit, when sudden electron movement occurs inside the battery, the secondary battery explodes and a fire occurs, causing safety problems. In particular, when an electrical malfunction such as overcharge, overdischarge, or external short circuit occurs, a high current flows and heat conductivity of the current collector is low, so that heat of the current collector is higher than that of the active material layer. Therefore, when such heat is diffused, the positive electrode active material including the metal oxide is decomposed and recrystallized, and a flammable gas including oxygen is generated, which may lead to a larger explosion.

Conventionally, in order to solve this problem, a method of using an ionic liquid that does not generate flammable gas as an electrolyte or installing a protection circuit to block current has been proposed. However, when an ionic liquid is used as an electrolyte, there is a problem in that the ionic conductivity is lowered compared to the conventional organic electrolyte, and the performance of the battery is also lowered. In addition, in order to install a protection circuit that blocks current, more space must be secured inside the secondary battery, so there is a problem that the energy density relative to the volume decreases.

Korean Patent Registration No. 1471666

The problem to be solved by the present invention is that even if an explosion or fire occurs due to abnormal operations such as internal short circuit, external short circuit, overcharge, overdischarge, etc., it becomes flame retardant to prevent the spread of fire to other surrounding secondary batteries to ensure safety. It is to provide a battery case and a pouch-type secondary battery for secondary batteries that can be used.

The problems of the present invention are not limited to the problems mentioned above, and other problems that are not mentioned will be clearly understood by those skilled in the art from the following description.

A battery case for a secondary battery according to an embodiment of the present invention for solving the above problem is a pouch-type battery case that houses an electrode assembly formed by stacking a positive electrode, a separator, and a negative electrode, comprising: a gas barrier layer made of metal; A surface protective layer made of a first polymer and positioned on an outer layer of the gas barrier layer; A sealant layer made of a second polymer and positioned on the inner layer of the gas barrier layer; It has flame retardancy, and includes a flame-retardant film layer positioned on an outer layer than the surface protection layer or an inner layer than the sealant layer, and the flame-retardant film layer is formed by surrounding a core including a flame retardant in a shell made of a third polymer Microcapsules; And a polymer substrate made of a fourth polymer, wherein the microcapsules are applied to at least one surface or contained therein.

In addition, the flame retardant may include a halogen-based flame retardant, a phosphorus-based flame retardant, or an inorganic compound flame retardant.

In addition, the flame retardant may include calcium bromide (CaBr2).

In addition, the third polymer may be one or more materials selected from the group consisting of polystyrene resin, ABS resin, polyether resin, polycarbonate resin, polyacrylate resin, polymethyl methacrylate resin, and acrylonitrile resin. .

In addition, the third polymer may include polymethyl methacrylate (PMMA).

In addition, the fourth polymer is polyethylene terephthalate (PET), polyester (Polyester, PE), polytetrafluoroethylene (PTFE), polydimethylsiloxane (PDMS), Kapton, Polyimide (PI), nylon (Nylon), polyvinylalcohol (PVA), polyisobutylene, polyurethane elastic sponge, polyvinyl butyral, polychloroprene, Natural rubber, Polyacrylonitrile, Polydiphenolcarbonate, Polyetherchloride, Polyvinylidene Chloride, Polystylene (PS), Polyethylene, Polypropylene It may be one or more materials selected from the group consisting of Polypropylene, PP) and Polyvinyl Chloride (PVC).

In addition, the fourth polymer may include polydimethylsiloxane (PDMS).

A method for manufacturing a flame retardant film according to an embodiment of the present invention for solving the above problem includes the steps of liquefying a polymer substrate made of a fourth polymer; Forming a mixed solution by adding microcapsules containing a flame retardant to the liquefied polymer substrate; Stirring the mixed solution; Injecting the mixed solution into a frame in a film shape or coating a substrate; And curing the mixed solution.

In addition, in the step of forming the mixed solution, a curing agent may be further added to the mixed solution.

In addition, the microcapsules may have a ratio of 10 to 50 wt%.

In addition, the method of manufacturing the microcapsules, preparing a third polymer solution; Adding a flame retardant to the solution; Stirring the solution to emulsify the third polymer and the flame retardant; And it may include the step of evaporating the solvent solvent.

In addition, the flame retardant may include calcium bromide (CaBr2).

In addition, the third polymer may include polymethyl methacrylate (PMMA).

In addition, the fourth polymer may include polydimethylsiloxane (PDMS).

A pouch-type secondary battery according to an embodiment of the present invention for solving the above problems includes an electrode assembly formed by stacking a positive electrode, a separator, and a negative electrode; And a pouch-type battery case accommodating the electrode assembly, wherein the battery case includes: a gas barrier layer made of metal; A surface protective layer made of a first polymer and positioned on an outer layer of the gas barrier layer; A sealant layer made of a second polymer and positioned on the inner layer of the gas barrier layer; It has flame retardancy, and includes a flame-retardant film layer positioned on an outer layer than the surface protection layer or an inner layer than the sealant layer, and the flame-retardant film layer is formed by surrounding a core including a flame retardant in a shell made of a third polymer Microcapsules; And a polymer substrate made of a fourth polymer, wherein the microcapsules are applied to at least one surface or contained therein.

The present invention also provides a battery module including the pouch-type secondary battery as a unit battery.

The present invention also, a battery pack comprising the battery module.

The present invention further comprises the battery pack.

The devices include computers, notebooks, smartphones, mobile phones, tablet PCs, wearable electronic devices, power tools, electric vehicles (EV), hybrid electric vehicles (HEVs), and plug-in hybrids. An electric vehicle (Plug-in Hybrid Electric Vehicle, PHEV) or a power storage device may be mentioned, but is not limited thereto.

Since the structure of the device and a method of manufacturing them are well known in the art, detailed descriptions thereof are omitted herein.

Other specific details of the present invention are included in the detailed description and drawings.

According to the embodiments of the present invention, there are at least the following effects.

Even if explosion or fire occurs due to abnormal operations such as internal short circuit, external short circuit, overcharge, overdischarge, including flame-retardant film layer in the pouch-type battery case, it becomes flame-retardant to prevent the spread of fire to other secondary batteries in the vicinity. Safety can be secured by preventing it.

In addition, since the flame retardant included in the flame retardant film layer becomes micro-encapsulated surrounded by a shell, even if the flame retardant film layer is formed on the outermost layer of the secondary battery, it may be prevented from reacting with the atmosphere.

In addition, since the flame-retardant film has electrolyte resistance, even if the flame-retardant film layer is formed on the innermost layer of the secondary battery, damage to the flame-retardant film may be prevented.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is an assembly diagram of a pouch-type secondary battery according to an embodiment of the present invention.
2 is a cross-sectional view of a pouch film according to an embodiment of the present invention.
3 is a schematic diagram of a flame retardant film layer according to an embodiment of the present invention.
4 is a schematic diagram of a microcapsule according to an embodiment of the present invention.
5 is a flowchart illustrating a method of manufacturing a microcapsule according to an embodiment of the present invention.
6 is a flow chart showing a method of manufacturing a flame retardant film according to an embodiment of the present invention.
7 is a schematic diagram of a flame retardant film layer according to another embodiment of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, and only these embodiments make the disclosure of the present invention complete, and are common knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings that can be commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not interpreted ideally or excessively unless explicitly defined specifically.

The terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, “comprises” and/or “comprising” do not exclude the presence or addition of one or more other elements other than the mentioned elements.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is an assembly diagram of a pouch-type secondary battery 1 according to an embodiment of the present invention.

The pouch-type secondary battery 1 according to an embodiment of the present invention includes an electrode assembly 10 formed by stacking a positive electrode, a separator, and a negative electrode, and accommodating the electrode assembly 10, as shown in FIG. 1. It includes a pouch-type battery case 13.

In order to manufacture the pouch-type secondary battery 1, a slurry obtained by mixing an electrode active material, a binder, and a plasticizer is first applied to a positive electrode current collector and a negative electrode current collector to prepare electrodes such as a positive electrode and a negative electrode. The electrode assembly 10 having a predetermined shape is formed by stacking this on both sides of a separator, and then the electrode assembly 10 is inserted into the battery case 13, and the electrolyte is injected and then sealed.

Specifically, the electrode assembly 10 is a laminated structure having two types of electrodes, an anode and a cathode, and a separator interposed between the electrodes to insulate the electrodes from each other, or disposed on the left or right side of any one electrode. Can be The laminated structure may have various shapes without limitation, such as a positive electrode and a negative electrode of a predetermined standard may be laminated with a separator interposed therebetween, or may be wound in a jelly roll form. Two types of electrodes, that is, a positive electrode and a negative electrode, have a structure in which an active material slurry is coated on an electrode current collector in the form of a metal foil or metal mesh including aluminum and copper, respectively. The slurry may be formed by stirring a particulate active material, an auxiliary conductor, a binder, a plasticizer, and the like in a state in which a solvent is added. The solvent is removed in a subsequent process.

The electrode assembly 10 includes an electrode tab 11, as shown in FIG. 1. The electrode tabs 11 are respectively connected to the anode and the cathode of the electrode assembly 10, protrude to the outside of the electrode assembly 10, and become a path through which electrons can move between the inside and the outside of the electrode assembly 10. . The current collector of the electrode assembly 10 includes a portion coated with an electrode active material and a terminal portion to which the electrode active material is not applied, that is, a non-coated portion. In addition, the electrode tab 11 may be formed by cutting the uncoated portion or by connecting a separate conductive member to the uncoated portion by ultrasonic welding or the like. As shown in FIG. 1, the electrode tabs 11 may protrude from one side of the electrode assembly 10 in the same direction, but are not limited thereto and may protrude in different directions.

An electrode lead 12 is connected to the electrode tab 11 of the electrode assembly 10 by spot welding or the like. In addition, a part of the electrode lead 12 is surrounded by an insulating portion 14. The insulating part 14 is located limited to the sealing part 134 in which the upper case 131 and the lower case 132 of the battery case 13 are thermally fused, and is adhered to the battery case 13. In addition, electricity generated from the electrode assembly 10 is prevented from flowing to the battery case 13 through the electrode lead 12 and the sealing of the battery case 13 is maintained. Accordingly, the insulating portion 14 is made of a non-conductive non-conductor that does not conduct electricity well. In general, as the insulating portion 14, an insulating tape that is easy to attach to the electrode lead 12 and has a relatively thin thickness is often used, but it is not limited thereto, and various members can be used as long as the electrode lead 12 can be insulated. have.

The electrode lead 12 has one end connected to the positive electrode tab 111, and one end connected to the positive electrode lead 121 and the negative electrode tab 112 extending in a direction in which the positive electrode tab 111 protrudes, and the negative electrode tab 112 ) Includes a cathode lead 122 extending in the protruding direction. Meanwhile, the other ends of the positive lead 121 and the negative lead 122 protrude to the outside of the battery case 13, as shown in FIG. 1. Accordingly, electricity generated inside the electrode assembly 10 can be supplied to the outside. In addition, since the anode tab 111 and the cathode tab 112 are formed to protrude in various directions, respectively, the anode lead 121 and the cathode lead 122 may also extend in various directions, respectively.

The anode lead 121 and the cathode lead 122 may have different materials from each other. That is, the positive lead 121 may be made of the same aluminum (Al) material as the positive current collector, and the negative lead 122 may be made of the same copper (Cu) material as the negative current collector or a copper material coated with nickel (Ni). In addition, a portion of the electrode lead 12 protruding to the outside of the battery case 13 becomes a terminal portion and is electrically connected to the external terminal.

The battery case 13 is a pouch made of a flexible material. In addition, the battery case 13 accommodates and seals the electrode assembly 10 so that a part of the electrode lead 12, that is, the terminal portion is exposed. The battery case 13 includes an upper case 131 and a lower case 132 as shown in FIG. 1. In the lower case 132, a cup portion 133 is formed to provide an accommodation space 1331 capable of accommodating the electrode assembly 10, and in the upper case 131, the electrode assembly 10 is a battery case 13 The accommodation space 1331 is covered from the top so as not to be separated from the outside of the unit. In this case, as shown in FIG. 1, a cup portion 133 in which an accommodation space 1331 is provided is also formed in the upper case 131, so that the electrode assembly 10 may be accommodated from the top. However, the present invention is not limited thereto, and the cup portion 133 may be formed only in the lower case 132 and may be variously formed. In addition, the upper case 131 and the lower case 132 may be manufactured by having one side connected to each other as shown in FIG. 1, but are not limited thereto and may be manufactured in various ways such as being separated from each other and manufactured separately.

When the electrode lead 12 is connected to the electrode tab 11 of the electrode assembly 10 and the insulating portion 14 is formed on a part of the electrode lead 12, the cup portion 133 of the lower case 132 The electrode assembly 10 is accommodated in the accommodation space 1331, and the upper case 131 covers the space from above. Then, an electrolyte is injected into the inside, and sealing portions 134 formed on the edges of the upper case 131 and the lower case 132 are sealed. The electrolyte is for moving lithium ions generated by the electrochemical reaction of the electrode during charging and discharging of the secondary battery 1, and is a non-aqueous organic electrolyte or a polymer using a polymer electrolyte, which is a mixture of a lithium salt and a high-purity organic solvent. It may include. Through this method, a pouch-type secondary battery 1 may be manufactured.

2 is a cross-sectional view of a pouch film 135 according to an embodiment of the present invention.

According to an embodiment of the present invention, including the flame retardant film layer 1354 having flame retardancy in the pouch-type battery case 13, explosions and fires occur due to abnormal operations such as internal short circuit, external short circuit, overcharge, overdischarge, etc. Even if it is flame-retardant, it is possible to secure safety by preventing the spread of fire to other secondary batteries 1 around it.

To this end, in the battery case 13 according to an embodiment of the present invention, in the pouch-type battery case 13 accommodating the electrode assembly 10 formed by stacking a positive electrode, a separator, and a negative electrode, a gas made of metal Barrier layer 1351; A surface protection layer 1352 made of a first polymer and positioned on an outer layer of the gas barrier layer 1351; A sealant layer (1353) made of a second polymer and positioned on the inner layer of the gas barrier layer (1351); It has flame retardancy and includes a flame retardant film layer 1354 positioned on an outer layer than the surface protection layer 1352 or an inner layer than the sealant layer 1352, and the flame retardant film layer 1354 is made of a third polymer. The shell 222 is a microcapsule 22 formed by surrounding the core 221 containing a flame retardant; And a polymer substrate 21 made of a fourth polymer and coated on at least one surface of the microcapsules 22 or included therein.

The battery case 13 is manufactured by drawing the pouch film 135. That is, it is manufactured by stretching the pouch film 135 to form the cup portion 133. As shown in FIG. 3, the pouch film 135 includes a gas barrier layer 1351, a surface protection layer 1352, a sealant layer 1353, and a flame retardant film layer. Flame Retardant Film Layer, 1354).

The gas barrier layer 1351 secures the mechanical strength of the battery case 13, blocks entry of gas or moisture from the outside of the secondary battery 1, and prevents leakage of an electrolyte solution. In general, the gas barrier layer 1351 includes a metal, and it is preferable that an aluminum thin film (Al Foil) is mainly used. Although aluminum can secure a mechanical strength of a predetermined level or higher, it is light in weight, and complements the electrochemical properties of the electrode assembly 10 and the electrolyte, and can secure heat dissipation. However, the present invention is not limited thereto, and various materials may be included in the gas barrier layer 1351. For example, it may be one or more materials selected from the group consisting of iron (Fe), carbon (C), chromium (Cr), manganese (Mn), nickel (Ni), and aluminum (Al). In this case, when the gas barrier layer 1351 is made of a material containing iron, mechanical strength is improved, and when a material containing aluminum is made of a material, flexibility is improved, so it may be used in consideration of each characteristic.

The surface protection layer 1352 is made of a first polymer and is located on the outer layer of the gas barrier layer 1351 to protect the secondary battery 1 from friction and collision with the outside, while protecting the electrode assembly 10 from the outside. Insulate electrically. Here, the outer layer refers to a layer located in a direction opposite to the direction in which the electrode assembly is located based on the gas barrier layer. The first polymer for preparing the surface protective layer 1352 is polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon , Polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and may be one or more materials selected from the group consisting of glass fibers. In particular, it is preferable to use a polymer such as nylon resin or polyethylene terephthalate (PET) mainly having abrasion resistance and heat resistance. In addition, the surface protection layer 1352 may have a single layer structure made of any one material, or may have a composite layer structure formed by each layer of two or more materials.

The sealant layer 1352 is made of a second polymer, and is positioned on the inner layer of the gas barrier layer 1351. Here, the inner layer refers to a layer positioned in a direction in which the electrode assembly is positioned based on the gas barrier layer. Accordingly, the gas barrier layer 1351 is stacked between the surface protection layer 1352 and the sealant layer 1352, as shown in FIG. 2. When the pouch-type battery case 13 is formed by drawing and molding the pouch film 135 of the laminated structure as described above using a punch or the like, a portion of the pouch-type battery case 13 is stretched to include a pocket-shaped receiving space 1333 ( 133). In addition, when the electrode assembly 10 is accommodated in the receiving space 1333, an electrolyte is injected. Thereafter, when the upper case 131 and the lower case 132 are brought into contact with each other and thermally compressed to the sealing portion 134, the sealant layers 1351 are adhered to each other, thereby sealing the battery case 13. At this time, since the sealant layer 1352 directly contacts the electrode assembly 10, it must have insulation, and since it contacts the electrolyte, it must have corrosion resistance. In addition, since the inside must be completely sealed to block material movement between the inside and outside, it must have high sealing properties. That is, the sealing portions 134 to which the sealant layers 1352 are bonded to each other should have excellent thermal bonding strength. In general, the second polymer for producing the sealant layer 1352 is polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, It may be one or more materials selected from the group consisting of nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and fiberglass. In particular, it is preferable that a polyolefin resin such as polypropylene (PP) or polyethylene (PE) is mainly used. Polypropylene (PP) is excellent in mechanical properties such as tensile strength, stiffness, surface hardness, abrasion resistance, heat resistance, and chemical properties such as corrosion resistance, and is mainly used to manufacture the sealant layer 1351. Further, it may be composed of non-stretched polypropylene (Cated Polypropylene) or polypropylene-butylene-ethylene terpolymer. In addition, the sealant layer 1351 may have a single layer structure made of any one material, or may have a composite layer structure formed by each of two or more materials.

3 is a schematic diagram of a flame retardant film layer 1354 according to an embodiment of the present invention.

The flame retardant film layer 1354 has flame retardancy, and is positioned on an outer layer of the surface protection layer 1352 or an inner layer of the sealant layer 1352. In particular, the flame retardant film layer 1354 may be located on the outermost layer or the innermost layer of the pouch film 135. If the flame retardant film layer 1354 is located on the innermost layer of the pouch film 135, the flame retardant film layer 1354 is preferably removed from the sealing portion 134. This is because, when thermal compression is performed on the sealing portion 134, the sealant layers 1351 are adhered to each other, and the battery case 13 can be sealed.

The flame retardant film layer 1354 includes a flame retardant that does not burn easily, and even if an explosion or fire occurs due to abnormal operation of the secondary battery 1, it becomes flame-retardant to prevent the spread of fire to other secondary batteries 1 in the vicinity. Thus, safety can be secured.

Specifically, as shown in FIG. 3, the flame-retardant film 2, which becomes the flame-retardant film layer 1354, has a shell 222 made of a third polymer surrounded by a core 221 including a flame retardant. Capsule 22; And a polymer substrate 21 made of a fourth polymer and in which the microcapsules 22 are included.

The polymer substrate 21 is made of a fourth polymer, and the microcapsules 22 are included therein. Such a polymer substrate 21 becomes a substrate for the flame retardant film layer 1354, and is preferably flexible in order to be easily attached to the outermost layer or the innermost layer of the pouch film 135. The fourth polymer is polyethylene terephthalate (PET), polyester (PE), polytetrafluoroethylene (PTFE), polydimethylsiloxane (PDMS), Kapton, and polyimide. , PI), nylon, polyvinylalcohol (PVA), polyisobutylene, polyurethane elastic sponge, polyvinyl butyral, polychloroprene, natural rubber, poly Acrylonitrile, Polydiphenolcarbonate, Polyetherchloride, Polyvinylidene Chloride, Polystylene (PS), Polyethylene, Polypropylene (PP) And it may be one or more materials selected from the group consisting of polyvinyl chloride (PVC). In particular, it is preferable to use polydimethylsiloxane (PDMS) having high insulation, low thermal conductivity, and flame retardancy. Since such polydimethylsiloxane (PDMS) corresponds to a thermosetting resin, it does not melt again even if a fire occurs inside the secondary battery 1.

4 is a schematic diagram of a microcapsule 22 according to an embodiment of the present invention.

As shown in FIG. 4, the microcapsule 22 is formed by enclosing a shell 222 made of a third polymer and a core 221 containing a flame retardant. In addition, when an explosion or fire occurs inside the secondary battery 1 and reaches a specific temperature, the shell 222 is melted and the core 221 is discharged to the outside. As a result, the flame retardant included in the core 221 is flame retardant, so that the spread of fire to the surrounding secondary battery 1 can be prevented.

The third polymer may be one or more materials selected from the group consisting of polystyrene resin, ABS resin, polyether resin, polycarbonate resin, polyacrylate resin, polymethyl methacrylate resin, and acrylonitrile resin. In particular, it is preferable that it is polymethyl methacrylate (PMMA).

The flame retardant is a substance that inhibits the combustion reaction, and may include various flame retardants such as a halogen-based flame retardant, a phosphorus-based flame retardant, or an inorganic compound flame retardant.

Halogen-based flame retardants generally exhibit a flame retardant effect by substantially stabilizing radicals generated in the gas phase. Halogen-based flame retardants are, for example, tribromo phenoxyethane, tetra bromo bisphenol-A (TBBA), octabromo diphenyl ether (OBDPE), calcium bromide (CaBr ₂ ), brominated epoxy oligomer, brominated polycarbonate oligomer, Chlorinated paraffin, chlorinated polyethylene, and alicyclic chlorine-based flame retardants.

Phosphorus-based flame retardants generally produce polymetaphosphoric acid by thermal decomposition, which forms a protective layer or exerts a flame retardant effect by blocking oxygen by a carbon film produced by dehydration when polymetaphosphoric acid is produced. Examples of phosphorus-based flame retardants include phosphates such as red, ammonium phosphate, phosphine oxide, phosphine oxide diols, phosphites, phosphonates, triaryl phosphate, alkyldiaryl phosphate, trialkyl phosphate, and resorcinaol bisdiphenyl phosphate (RDP).

Inorganic compound flame retardants are generally decomposed by heat to release non-combustible gases such as water, carbon dioxide, sulfur dioxide, and hydrogen chloride and cause endothermic reactions, thereby diluting the combustible gas to prevent access to oxygen, and cooling and pyrolysis by endothermic reactions. By reducing the production of products, it exerts a flame retardant effect. Inorganic compound flame retardants are, for example, aluminum hydroxide (Al(OH) ₃ ), magnesium hydroxide (Mg(OH) ₂ ), boric acid (BH ₃ O ₃ ), antimony oxide, tin hydroxide, tin oxide, molybdenum oxide, zirconium compound , Borate, calcium salt, etc.

According to an embodiment of the present invention, various flame retardants may be used, but it is preferable to use a halogen-based flame retardant among the flame retardants, and in particular, it is more preferable to use calcium bromide (CaBr ₂ ). Such calcium bromide (CaBr ₂ ) may be used as an anhydride to which water molecules are not bound, but may be used as a hydrate to which water molecules are bound. And in some cases, it may further include other additives that induce a flame retardant synergistic effect when mixed with the flame retardant illustrated above.

Calcium bromide (CaBr ₂ ) is generally very excellent in preventing flame propagation among flame retardants.

name Equation Melting point or boiling point
[℃] SET
[s] Ammonium Bromide NH ₄ Br 235 61 Ammonium Bicarbonate NH ₄ HCO ₃ 41.9 63 Mono Ammonium phosphate (NH ₄ )H ₂ PO ₄ 190 60 Ammonium Polyphosphate [NH ₄ PO ₃ ] _n (OH) ₂ - 64 Calcium Bromide CaBr ₂ 730 5 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) C ₁₂ H ₉ O ₂ P 116 52 N,N-diperfluorodiethyl-N-(2-hydroperfluoro-2-methylpentyl)amine (FC-40) C ₁₀ HF ₂₂ N 155 40 Hexabromocyclododecane (HBCD) C ₁₂ H ₁₈ Br ₆ 186 63 Melamine C ₃ H ₆ N ₆ 345 65 Melamine Phosphate C ₃ H ₉ N ₆ O ₄ P 557.5 110 NOVEC 7500 C ₉ H ₅ F ₁₅ O 128 40 Triphenyl phosphate (C ₆ H ₅ O) ₃ PO 50 45 Triphenylphosphite C ₁₈ H ₁₅ O ₃ P 360 30 Urea Phosphate CH ₇ N ₂ O ₅ P 116 80

Table 1 is a table measuring SET (Self-Extinguishing Time) of various types of flame retardants. Specifically, 0.8 g of each of the above substances is added to 2 g of an electrolytic solution of 3:7 mixture of EC (Ethylene carbonate) and EMC (Ethyl methyl carbonate), followed by combustion, and the time until combustion is completed is measured. I did it. As disclosed in Table 1, compared to other substances of calcium bromide (CaBr ₂ ), the SET is the shortest at 5 seconds. Therefore, it can be seen that the flame retardant effect is the most excellent.

On the other hand, since calcium bromide (CaBr ₂ ) has deliquescent properties, it can react with water vapor in the atmosphere when left in the atmosphere. However, according to an embodiment of the present invention, since the flame retardant is micro-encapsulated surrounded by the shell 222, even if the flame retardant film layer 1354 is formed on the outermost layer of the secondary battery 1, it may be prevented from reacting with the atmosphere. have.

In addition, calcium bromide (CaBr ₂ ) may be damaged by reacting with the electrolyte solution of the secondary battery 1. However, according to an embodiment of the present invention, since the polymer substrate 21 of the flame retardant film 2 and the shell 222 have electrolyte resistance, the flame retardant film layer 1354 is the innermost layer of the secondary battery 1 Even if it is formed in the flame retardant film 2 may be prevented from being damaged.

5 is a flowchart illustrating a method of manufacturing the microcapsule 22 according to an embodiment of the present invention.

A method of manufacturing a microcapsule 22 according to an embodiment of the present invention includes the steps of preparing a third polymer solution; Adding a flame retardant to the solution; Stirring the solution to emulsify the third polymer and the flame retardant; And evaporating the solution with a solvent.

Specifically, first, a third polymer, particularly polymethyl methacrylate (PMMA), is dissolved in dichloromethane (DCM) to prepare a solution (S501). And a flame retardant, particularly calcium bromide (CaBr ₂ ) is added to the solution (S502), and the solution is stirred using a stirring device to prepare a turbid solution (S503). Thereafter, the turbid solution and silicone oil are mixed to perform an emulsification process, and a mixed solution is prepared. Thereby, polymethyl methacrylate (PMMA) and calcium bromide (CaBr ₂ ) can be emulsified. In this case, the volume ratio of dichloromethane (DCM) and silicone oil is preferably 1:1 to 1:100.

And when the mixture is further stirred, the solvent dichloromethane (DCM) is evaporated, and the shell 222 made of polymethyl methacrylate (PMMA) surrounds the core 221 containing calcium bromide (CaBr ₂ ). One microcapsule 22 may be formed (S504). Then, the silicone oil is separated by performing a filtration process, followed by a washing process, and then dried in an oven. Thereby, such microcapsules 22 can be separated and obtained.

The microcapsules 22 manufactured as described above have a shape of a sphere or an ellipse, and the diameter changes according to the speed at which the solution is stirred using a stirring device. That is, the faster the stirring speed, the lower the diameter, and the lower the speed, the higher the diameter. Therefore, the diameter of the microcapsules 22 can also be adjusted by adjusting the stirring speed. Preferably, the diameter may be 30 to 100 μm, more preferably 40 to 70 μm.

At this time, while stirring the mixed solution, heptane may be further added. Heptane removes the solvent of the polymer solution without dissolving the polymer. Therefore, by adding heptane, more effective phase separation is induced, and residual solvent between polymer chains can be removed more effectively. However, the present invention is not limited thereto, and various aliphatic hydrocarbons other than heptane may be added.

Meanwhile, according to an embodiment of the present invention, when manufacturing the microcapsules 22, silicone oil is added. Thus, it is possible to prevent the spread of fire more effectively than when silicone oil is not added.

6 is a flowchart showing a method of manufacturing a flame retardant film 2 according to an embodiment of the present invention.

A method of manufacturing a flame-retardant film 2 according to an embodiment of the present invention includes the steps of liquefying a polymer substrate 21 made of a fourth polymer; Forming a mixed solution by adding microcapsules 22 containing a flame retardant to the liquefied polymer substrate 21; Stirring the mixed solution; Injecting the mixed solution into a frame (not shown) in a film shape or coating a substrate (not shown); And curing the mixed solution.

Specifically, first, a fourth polymer, particularly polydimethylsiloxane (PDMS), is liquefied (S601), and a microcapsule 22 containing a flame retardant is added to form a mixed solution (S602). At this time, the proportion of the microcapsules 22 is 0 to 80 wt%, preferably 10 to 50 wt%. If the microcapsules 22 are excessively small, the flame retardant effect is not sufficiently exhibited, and if the microcapsules 22 are excessively large, the microcapsules 22 may not be fixed to and included in the polymer substrate 21.

Further, in order to cure the mixed solution later, a curing agent may be further added. Such a curing agent is not limited, such as an amine compound, an imidazole compound, a phenol compound, a phosphorus compound, or an acid anhydride compound, and various curing agents may be used. Then, the mixed solution is stirred using a stirring device. Thereby, the microcapsules 22 can be uniformly dispersed in the polydimethylsiloxane (PDMS).

After sufficiently stirring this mixed solution (S603), it is injected into a frame or a substrate (not shown) is thinly and widely coated to form a film (S604). And by drying and curing the mixed solution in an oven, the flame retardant film 2 may be manufactured (S605). And when injected into a frame or coated on a substrate, the thickness of the flame-retardant film 2 may be adjusted by adjusting the thickness of the mixed solution. Heat may be applied at a temperature ranging from 20 to 120° C. to cure the mixed solution.

7 is a schematic diagram of a flame retardant film layer 1354 according to another embodiment of the present invention.

According to an embodiment of the present invention, a microcapsule 22 is included in the polymer substrate 21 made of a fourth polymer to be formed. However, according to another embodiment of the present invention, the microcapsules 22 may be applied to at least one surface of the polymer substrate 21. Thereby, when the shell 222 is melted by reaching a certain temperature, the core 221 is more leaked to the outside and the flame retardant covers the polymer substrate 21 with a higher density, so that the spread of fire can be more effectively prevented. I can.

Manufacturing example

Polymethyl methacrylate (PMMA) 400 mg is dissolved in dichloromethane (DCM) 12 mL to prepare a 2.5 wt% solution of polymethyl methacrylate (PMMA). Then, 1 g of calcium bromide (CaBr2) powder was added to the polymethyl methacrylate (PMMA) solution, and the above was performed at a speed of 1500 RPM for about 0.5 hours using a stirring device (manufacturer: Miseong Science Equipment, model name: HSD180). The solution was stirred to prepare a turbid solution.

Thereafter, while stirring 12 mL of silicone oil at 500 RPM, the turbid liquid was added to prepare a mixed solution. Then, the mixed solution is further stirred for about 0.5 hours to evaporate solvent evaporation, that is, dichloromethane (DCM). Then, 50 mL of heptane is added to completely remove the solvent in the polymer monomer.

After stirring for about 4 hours at a speed of 1500 RPM, a filtration process is performed to separate silicone oil and heptane, and washing and drying processes are performed. Thereby, a shell made of polymethyl methacrylate (PMMA), a microcapsule containing 1 g of a core containing calcium bromide (CaBr ₂ ) is formed.

Meanwhile, 3.2 g of liquefied polydimethylsiloxane (PDMS) and 0.32 g of a curing solution are mixed, and 0.88 g (about 20 wt%) of microcapsules containing the flame retardant are added to form a mixed solution. After stirring the mixed solution, it is poured into a circular mold having a diameter of 5 cm, dried in an oven at 80° C. for about 5 hours, and cured.

And when the contents are separated from the circular frame after curing, a flame retardant film having a diameter of 5 cm and a thickness of 1.5 mm is produced.

Comparative example One

It was prepared in the same manner as in Preparation Example, except that only polydimethylsiloxane (PDMS) was cured without including any microcapsules.

Comparative example 2

It was prepared in the same manner as in Preparation Example, except that calcium bromide (CaBr ₂ ) was added as it is without microencapsulation.

Method of measuring physical properties- Flame retardant

The flame-retardant films according to Preparation Example, Comparative Example 1, and Comparative Example 2 were fixed with tongs, respectively, and then fire-protected using a torch.

Physical property measurement result- Flame retardant

Flame-retardant films according to Preparation Example and Comparative Example 2 only left a scorched mark on the edge. However, in the flame retardant film according to Comparative Example 1, the flame spread as a whole after 5 seconds, and then burned out.

Method of measuring physical properties-atmospheric stability

The flame-retardant films according to Preparation Example, Comparative Example 1 and Comparative Example 2 were left in the air and maintained at 25°C and 65°C for 2 weeks, and the weight was measured every day.

Physical property measurement result-atmospheric stability

Manufacturing example Comparative Example 1 1 day 14 day Rate of change 1 day 14 day Rate of change 25 ℃ 2.53 2.57 1.58% 2.53 2.66 5.13% 65 ℃ 2.50 2.48 -0.8% 2.50 2.63 5.20%

As shown in Table 2, when comparing Preparation Example and Comparative Example 1 of the present invention, the weight of the flame retardant film according to the preparation example increased to 2.57 g after 2 weeks at 25° C. at 25°C, resulting in a 1.58% change in weight I did. However, in the flame retardant film according to the comparative example, the weight of 2.53 g increased to 2.66 g after 2 weeks at 25° C., and the weight changed by 5.13%.

In addition, the flame retardant film according to the manufacturing example decreased the weight of 2.50 g to 2.48 g after 2 weeks at 65° C., and the weight changed -0.8%. However, in the flame retardant film according to the comparative example, the weight of 2.50 g increased to 2.63 g after 2 weeks at 25° C., and the weight changed by 5.20%.

As such, the flame retardant film according to the manufacturing example of the present invention had less change in weight than the flame retardant film according to Comparative Example 1. Therefore, it can be seen that the flame retardant film according to the preparation example of the present invention has low reactivity with components such as water vapor in the atmosphere, and thus has excellent atmospheric stability.

Those of ordinary skill in the art to which the present invention pertains will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting. The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and various embodiments derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

1: secondary battery 2: flame retardant film
10: electrode assembly 11: electrode tab
12: electrode lead 13: battery case
14: insulation 21: polymer base
22: microcapsule 111: anode tab
112: negative tab 121: positive lead
122: negative lead 131: upper case
132: lower case 133: cup portion
134: sealing part 135: pouch film
221: core 222: shell
1331: accommodation space 1351: gas barrier layer
1352: surface protective layer 1353: sealant layer
1354: flame retardant film layer

Claims (19)

In a pouch-type battery case housing an electrode assembly formed by stacking a positive electrode, a separator, and a negative electrode,
A gas barrier layer made of metal;
A surface protective layer made of a first polymer and positioned on an outer layer of the gas barrier layer;
A sealant layer made of a second polymer and positioned on the inner layer of the gas barrier layer;
It has flame retardancy, and includes a flame retardant film layer positioned on an outer layer than the surface protective layer or an inner layer than the sealant layer,
The flame retardant film layer,
The shell made of a third polymer is formed by surrounding the core containing the flame retardant microcapsules; And
A battery case for a secondary battery made of a fourth polymer and including a polymer substrate on which the microcapsules are applied or included in at least one surface. The method of claim 1,
The flame retardant,
Battery case for secondary batteries containing a halogen-based flame retardant, a phosphorus-based flame retardant, or an inorganic compound flame retardant. The method of claim 2,
The flame retardant,
Battery case for secondary batteries containing calcium bromide (CaBr2). The method of claim 1,
The third polymer,
A battery case for a secondary battery comprising at least one material selected from the group consisting of polystyrene resin, ABS resin, polyether resin, polycarbonate resin, polyacrylate resin, polymethyl methacrylate resin, and acrylonitrile resin. The method of claim 4,
The third polymer,
Battery case for secondary batteries containing polymethyl methacrylate (PMMA). The method of claim 1,
The fourth polymer,
Polyethyleneterephthalate (PET), polyester (PE), polytetrafluoroethylene (PTFE), polydimethylsiloxane (PDMS), Kapton, polyimide (PI), Nylon, polyvinylalcohol (PVA), polyisobutylene, polyurethane elastic sponge, polyvinyl butyral, polychloroprene, natural rubber, polyacrylonitrile ( Polyacrylonitrile), Polydiphenolcarbonate, Polyetherchloride, Polyvinylidene Chloride, Polystylene (PS), Polyethylene, Polypropylene (PP) and Polyvinyl Chloride (Polyvinyl Chloride, PVC) one or more materials selected from the group consisting of a secondary battery battery case. The method of claim 6,
The fourth polymer,
Battery case for secondary batteries containing polydimethylsiloxane (PDMS). Liquefying a polymer substrate made of a fourth polymer;
Forming a mixed solution by adding microcapsules containing a flame retardant to the liquefied polymer substrate;
Stirring the mixed solution;
Injecting the mixed solution into a frame in a film shape or coating a substrate; And
Flame retardant film manufacturing method comprising the step of curing the mixed solution. The method of claim 8,
In the step of forming the mixed solution,
Flame retardant film manufacturing method further adding a curing agent to the mixed solution. The method of claim 8,
The microcapsules,
Flame-retardant film production method having a ratio of 10 to 50 wt%. The method of claim 8,
The method of manufacturing the microcapsules,
Preparing a third polymer solution;
Adding a flame retardant to the solution;
Stirring the solution to emulsify the third polymer and the flame retardant; And
Flame-retardant film manufacturing method comprising the step of evaporating the solvent solvent. The method of claim 11,
The flame retardant,
Method for producing a flame-retardant film containing calcium bromide (CaBr2). The method of claim 11,
The third polymer,
Flame retardant film manufacturing method comprising polymethyl methacrylate (PMMA). The method of claim 8,
The fourth polymer,
Method for producing a flame retardant film comprising polydimethylsiloxane (PDMS). An electrode assembly formed by stacking an anode, a separator, and a cathode; And
It includes a pouch-type battery case accommodating the electrode assembly,
The battery case,
A gas barrier layer made of metal;
A surface protective layer made of a first polymer and positioned on an outer layer of the gas barrier layer;
A sealant layer made of a second polymer and positioned on the inner layer of the gas barrier layer;
It has flame retardancy, and includes a flame retardant film layer positioned on an outer layer than the surface protective layer or an inner layer than the sealant layer,
The flame retardant film layer,
The shell made of a third polymer is formed by surrounding the core containing the flame retardant microcapsules; And
A pouch-type secondary battery made of a fourth polymer and including a polymer substrate coated on at least one surface of the microcapsules or included therein. A battery module comprising the pouch-type secondary battery according to claim 13 as a unit battery. A battery pack comprising the battery module according to claim 16. A device comprising the battery pack according to claim 17. The method of claim 18,
The device,
Computers, notebooks, smartphones, mobile phones, tablet PCs, wearable electronic devices, power tools, electric vehicles (EV), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles ( Plug-in Hybrid Electric Vehicle, PHEV) or power storage device.

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