Battery cell pad for secondary battery and preparation method thereof

Abstract

The invention relates to a battery cell pad for a secondary battery and a preparation method of the battery cell pad. Specifically, the present invention relates to a cell pad for a secondary battery and a method for manufacturing the same, the cell pad being disposed between cells of the secondary battery to prevent a thermal runaway phenomenon occurring in a single-axis cell from spreading to other cells.

Description

TECHNICAL FIELD

[0001] The present application relates to a battery cell pad for a secondary battery and a method of manufacturing the same. In particular, the present application relates to a battery cell pad for a secondary battery, which is disposed between battery cells and prevents a thermal runaway phenomenon occurring in one battery cell from spreading to another battery cell, and a method of manufacturing the same. BACKGROUND

[0002] In general, secondary batteries for electric vehicles are classified into three types according to the shape of an outer material. They are a cylindrical secondary battery in which an electrode assembly is accommodated in a metal can, a pouch secondary battery in which an electrode assembly is accommodated in a soft pack outer material, and a secondary battery in which battery materials are packaged in a square shape in an aluminum can housing.

[0003] Since a plurality of (12 battery cells) battery cells are closely stacked, if a thermal runaway phenomenon occurs in some battery cells, the thermal runaway phenomenon spreads to adjacent battery cells in a short time, which can cause a fire or an explosion accident in a battery unit, such as a battery module or a battery pack, which is larger than the capacity of the battery cells.

[0004] In particular, when a thermal runaway phenomenon occurs, a battery cell generates an ultra-high temperature region of about 600°C to 900°C, and due to this high temperature, a surrounding combustible (solid electrolyte interphase (SEI), decomposition → cathode electrolyte → anode decomposition → short circuit → electrolyte fire → thermal runaway) is ignited, further increasing the risk of fire. In addition, if a thermal runaway phenomenon occurs in one of the battery cells due to a manufacturing defect or misuse of the battery pack, the thermal runaway phenomenon can spread to adjacent battery cells.

[0005] In the battery pack for an electric vehicle used in the past, a buffer pad made of polyurethane foam (PU foam) or silicone foam, etc. is provided between a single-axis battery cell and an adjacent other battery cell to prevent a thermal runaway phenomenon occurring in the single-axis battery cell from spreading to the other battery cell, i.e., to delay and prevent the spread of the thermal runaway phenomenon.

[0006] However, although the above-mentioned polyurethane foam and silicone foam have a buffer function that is stretchable with pressure (face pressure), they have a problem of losing a viscoelastic body function at a high temperature state (200°C). In particular, since the above-mentioned foams exhibit a decomposition phenomenon in a temperature region (about 200°C) lower than a high temperature region in which a thermal runaway phenomenon occurs in a battery, there is a problem that the required thermal runaway delay effect cannot be provided.

[0007] To address these issues, Korean Patent Publication No. 10-2023-0132800, entitled "Insulating Multilayer Sheet Material, Preparation Method Thereof, and Article Using Thereof," proposes a multilayer sheet structure improved by adding silicone paper, glass fiber, etc., to foam. However, its cost-effectiveness and its function as a buffer pad and thermal runaway prevention pad are insufficient.

[0008] Furthermore, Korean Patent Publication No. 10-2022-0013603 discloses "a thermal runaway prevention pad and a battery cell housing structure including the thermal runaway prevention pad," wherein the thermal runaway prevention pad includes a first buffer made of elastic material, a fire extinguishing component for spraying extinguishing agent, and a second buffer. In addition, Korean Registered Patent No. 10-2425374, Korean Patent Publication No. 10-2023-0132800, Korean Registered Patent No. 10-2669747, and US Patent Publication No. US2024 / 0145843 disclose related technologies. Summary of the Invention

[0009] The present invention aims to provide a cell pad for secondary batteries and a method for preparing the same, which can delay thermal runaway that may occur due to misuse or damage to electric vehicle batteries.

[0010] Solution for solving the problem

[0011] The above objective is achieved by a cell pad for a secondary battery, which includes a polymer foam, a carbon fiber composite attached to both sides of the polymer foam, and an adhesive layer located between the polymer foam and the carbon fiber composite layer.

[0012] Preferably, the carbon fiber composite can be prepared by coating a quasi-non-combustible slurry containing an intumescent flame-retardant composition onto a carbon fiber nonwoven fabric.

[0013] Preferably, the polymer foam can be prepared by mixing an intumescent flame retardant composition, fumed silica and a foaming agent into a rubber selected from the group consisting of silicone rubber, thermoplastic elastomer and EPDM rubber and then compressing it.

[0014] Preferably, the aforementioned quasi-non-combustible slurry may contain, for every 100 parts by weight of water-soluble epoxy resin or vinyl acetate copolymer, 80 to 150 parts by weight of an intumescent flame retardant composition, 40 to 60 parts by weight of aluminum hydroxide, 1 to 10 parts by weight of an aqueous solution of montmorillonite, and 1 to 10 parts by weight of a polyoxyethylene (propylene-ethylene) copolymer.

[0015] Preferably, the above-mentioned intumescent flame retardant composition may contain 20 to 40 parts by weight of melamine, 20 to 40 parts by weight of carbamide (urea) and 30 to 50 parts by weight of D-glucol for every 100 parts by weight of ammonium polyphosphate.

[0016] Preferably, the adhesive layer may include an epoxy oil-based flame retardant adhesive or an epoxy water-based flame retardant adhesive.

[0017] Preferably, the carbon fiber nonwoven fabric can be treated with a sizing agent comprising liquid epoxy resin and hydrophilic fumed silica.

[0018] Furthermore, the above objective is achieved through a method for preparing a cell pad for secondary batteries, which includes: a step of treating a carbon fiber nonwoven fabric with a sizing agent; a step of coating the sizing carbon fiber nonwoven fabric with a quasi-non-combustible slurry containing an intumescent flame-retardant composition, followed by drying and curing to form a carbon fiber composite; a step of mixing a rubber selected from the group consisting of silicone rubber, thermoplastic elastomer, and EPDM rubber, an intumescent flame-retardant composition, fumed silica, and a foaming agent, followed by compression molding to prepare a polymer foam; a step of coating both sides of the polymer foam with an epoxy adhesive and attaching the carbon fiber composite to both sides of the polymer foam; and a step of heat-treating the attached polymer foam and the carbon fiber composite to dry and cure them.

[0019] Invention Effects

[0020] Because the battery cell pad for secondary batteries according to the present invention has quasi-non-combustible and thermal insulation properties, it can maintain its shape even at thermal runaway temperatures, thereby preventing and delaying thermal runaway. Furthermore, due to its excellent quasi-non-combustible and thermal insulation properties, the battery cell pad for secondary batteries according to the present invention can be used as fireproof products such as fireproof tents and fireproof curtains, or as a fireproof structural material for building exterior walls, etc. Attached Figure Description

[0021] Figure 1 This is a perspective view showing the structure of the cell pad for a secondary battery according to the present invention.

[0022] Figure 2 This is a perspective view showing that the cell pad for a secondary battery according to the present invention is disposed between the cells located in the battery pack.

[0023] Figure 3 This is a graph showing the test results of the combustion performance of the cell pad for secondary batteries according to the present invention. Detailed Implementation

[0024] All technical terms used in this invention, unless otherwise defined, have the following meanings and conform to the common understanding of those skilled in the art related to this invention. Furthermore, although preferred methods or samples are described in this specification, similar or equivalent methods or samples are also included within the scope of this invention.

[0025] The term “about” means a change of about 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% in a reference quantity, level, value, number, frequency, percentage, size, quantity, weight, or length.

[0026] In this specification, unless the context otherwise requires, the words “comprising” and “including” shall be understood to include the steps or components mentioned, or groups of steps or components, but do not exclude the inclusion of any other steps or components, or groups of steps or components.

[0027] Figure 1 The structure of the cell pad according to the present invention is shown. See also Figure 1 The battery cell pad for secondary batteries according to the present invention includes a polymer foam 11, a carbon fiber composite 12 attached to both sides of the polymer foam, and an adhesive layer (not shown) located between the polymer foam and the carbon fiber composite layer.

[0028] The aforementioned polymer foam 11 can be prepared by mixing an intumescent flame retardant composition, a foaming agent, and fumed silica into a rubber selected from the group consisting of silicone rubber, thermoplastic elastomers, and EPDM rubber, and then compressing it. Preferably, for every 100 parts by weight of the rubber (selected from the group consisting of silicone rubber, thermoplastic elastomers, and EPDM rubber), it may contain 100 parts by weight of a flame retardant (FR-IFC, intumescent flame retardant composition) and 40 to 60 parts by weight of fumed silica; additionally, it may contain 1 to 10 parts by weight of a foaming agent, dispersant, crosslinking agent, etc., as additives.

[0029] Polymer foams can be made from various types of rubber, thermoplastic elastomers, polyolefin polymers, etc., and preferably from a rubber selected from the group consisting of silicone rubber, thermoplastic elastomers, and EPDM rubber. Specifically, considering the temperature dependence of the compression set properties (creep, stress relaxation) of one of the main specifications of the battery cell pad, silicone rubber, which has the best heat resistance among rubbers, can be used.

[0030] The aforementioned polymer foam can be prepared by mixing an intumescent flame retardant composition, fumed silica, and a foaming agent into a rubber selected from the group consisting of silicone rubber, thermoplastic elastomer, and EPDM rubber, and then by compression molding or continuous foaming.

[0031] The compression molding method described above involves loading the mixture (compound) into a mold, compressing it using a compression press under specific temperature, pressure, and time conditions, and then decompressing (removing pressure) to produce foam. This is known as compression molded foam. According to one embodiment of the invention, it can be prepared by mixing an intumescent flame-retardant composition (FR-IFC), fumed silica, and a foaming agent into the rubber, followed by applying a peroxide crosslinking system and compression molding.

[0032] The above-mentioned continuous foaming method is a continuous process in which the above-mentioned mixture (compound) is fed to an extruder, discharged from the extruder die to form an extruded sheet, and then passed through hot air vulcanization (HAV; curing tunnel) to form foam.

[0033] The aforementioned carbon fiber composite 12 can be prepared by coating a quasi-non-combustible slurry containing an intumescent flame-retardant composition onto a carbon fiber nonwoven fabric. The aforementioned carbon fiber nonwoven fabric is not particularly limited and can be a recycled carbon fiber nonwoven fabric.

[0034] According to embodiments of the present invention, the carbon fiber nonwoven fabric can be treated with a sizing agent before the coating step described above. The sizing agent comprises a liquid epoxy resin and hydrophilic fumed silica. There are no particular limitations on the liquid epoxy resin; known products can be used. The sizing agent can be applied to the surface of the carbon fiber nonwoven fabric using methods such as spraying, blade coating, or slot coating, and then dried and cured. Treating the carbon fiber nonwoven fabric with the sizing agent can improve the adhesion to the quasi-non-combustible sizing agent.

[0035] The above-mentioned coating steps for quasi-non-combustible slurry can be achieved through continuous or discontinuous processes.

[0036] In continuous processes, any of the following methods can be used: roller coating, slot coating, or blade coating, to coat both sides of the sized carbon fiber nonwoven fabric with a quasi-non-combustible slurry, followed by heat treatment to cure it. Another method is to use a rotocure machine to coat the carbon fiber nonwoven fabric with the quasi-non-combustible slurry and then cure it through heat treatment.

[0037] In the above curing step, a drying curing machine can be used. For example, an air-based dryer, such as a hot air curing tunnel (HACT) or an ultra-high frequency-hot air curing tunnel (UHF-HACT), can be used to bond and cure the carbon fiber nonwoven fabric with the quasi-non-combustible slurry as a matrix resin. The preferred curing temperature is 150°C to 200°C, and the curing time is 2 to 10 minutes. The curing time is a factor that determines the length of the drying curing machine.

[0038] Discontinuous processes can be used for both mass production and small-batch production.

[0039] Specifically, the quasi-non-combustible slurry is coated onto sized carbon fiber nonwoven fabric and dried. Then, it is die-cut according to the dimensions of the battery cell pad and cured using a compression press. This process requires a pre-forming (die-cutting) machine and molds for compression curing.

[0040] Regarding the aforementioned quasi-non-combustible slurry, for every 100 parts by weight of water-soluble epoxy resin or vinyl acetate copolymer, it may contain 80 to 150 parts by weight of an intumescent flame retardant composition (FR-IFC), 40 to 60 parts by weight of aluminum hydroxide, 1 to 10 parts by weight of an aqueous solution of montmorillonite (G5 clay (MMT)-nanocomposite), and 1 to 10 parts by weight of a polyoxyethylene (propylene-ethylene) copolymer. The quasi-non-combustible slurry can be prepared using various types of mixers. Dissolvers, ribbon mixers, batch mixers, and planetary mixers can be used; for large-scale production, in-line mixers can also be used. The viscosity of the quasi-non-combustible slurry is a medium viscosity of approximately 50,000 to 100,000 cps, thus allowing for selection based on production volume. The aforementioned montmorillonite aqueous solution is a nanocomposite in which montmorillonite (MMT) is dispersed in deionized water in an exfoliated state. The exfoliated MMT nanocomposite exhibits excellent barrier and flame retardant properties and can provide a flame retardant enhancement effect (synergistic effect). In preparing the G5 clay nanocomposite, an inline mixer or an ultrasonic mixer can be used.

[0041] In addition, the above-mentioned intumescent flame retardant composition may contain 20 to 40 parts by weight of melamine, 20 to 40 parts by weight of carbamide (urea), and 30 to 50 parts by weight of D-glucol for every 100 parts by weight of ammonium polyphosphate. The intumescent flame retardant composition (FR-IFC) is an intumescent flame retardant system that forms a carbon barrier on the substrate surface, effectively blocking the supply of oxygen and providing nitrogen, thereby achieving an excellent flame retardant layer.

[0042] The polymer foam and carbon fiber composite prepared by the method described above can be interfacially bonded with an adhesive to prepare a battery cell pad.

[0043] The adhesives mentioned above can be epoxy oil-based flame retardant adhesives or epoxy water-based flame retardant adhesives.

[0044] The aforementioned epoxy-based oil-based flame-retardant adhesives may include one or more epoxy resins, aluminum hydroxide, ammonium polyphosphate, melamine, dicyandiamide, and a latent curing agent. The aforementioned epoxy resins may be BGE modified epoxy resin, CTBN modified epoxy resin, or mixtures thereof. The aforementioned ammonium polyphosphate may be used for intumescent barrier applications, and a latent curing agent (dicyandiamide) may be used to extend the pot life.

[0045] The aforementioned epoxy-based waterborne flame-retardant adhesive contains an equal weight of water-soluble epoxy resin and the aforementioned intumescent flame-retardant composition (FR-IFC), and may also contain a latent curing agent (imidazolium-based, EH5019S) and other additives. The aforementioned waterborne flame-retardant adhesive can improve the flame retardancy of the battery cell pad by including the intumescent flame-retardant composition (FR-IFC).

[0046] The interface-bonded cell pads can be heat-treated using a drying and curing machine to ultimately produce cell pads for secondary batteries. For example, drying and curing can be performed using a hot air curing tunnel (HACT) or an ultra-high frequency-hot air curing tunnel (UHF-HACT) machine, or continuously using a drum vulcanizing machine.

[0047] According to one embodiment of the present invention, a method for preparing a cell pad for a secondary battery is provided, comprising: a step of treating a carbon fiber nonwoven fabric with a sizing agent; a step of coating the sizing carbon fiber nonwoven fabric with a quasi-non-combustible slurry containing an intumescent flame-retardant composition, followed by drying and curing to form a carbon fiber composite; a step of preparing a polymer foam by mixing a rubber selected from the group consisting of silicone rubber, thermoplastic elastomer, and EPDM rubber with an intumescent flame-retardant composition, fumed silica, and a foaming agent to form a compound, followed by compression molding; a step of coating both sides of the polymer foam with an epoxy adhesive and attaching the carbon fiber composite to both sides of the polymer foam; and a step of heat-treating the attached polymer foam and carbon fiber composite to dry and cure them.

[0048] The battery cell pad prepared according to the present invention exhibits quasi-non-combustible flame retardant properties that meet KSF ISO 5660-1 (combustion performance test) and KSF 2271 (gas toxicity test for building decoration materials).

[0049] The present invention will be described in detail through the following embodiments, but the scope of the invention is not limited to these embodiments.

[0050] Example

[0051] Prepare a sizing agent with the composition shown in Table 1 below, apply it to both sides of the recycled carbon fiber nonwoven fabric by spraying, and then dry and cure it. Prepare a quasi-non-combustible sizing coating solution with the composition shown in Table 3 below, and apply it to both sides of the sizing-treated carbon fiber nonwoven fabric. After heat treatment, a carbon fiber composite is formed. Prepare an epoxy adhesive with the compositions shown in Tables 7 and 8 below. Apply the water-based epoxy adhesive from Table 8 to both sides of the polymer foam prepared with the composition from Table 9, and then interfacially bond the carbon fiber nonwoven fabric to the polymer foam. After drying and curing, a battery cell pad is formed.

[0052] Table 1

[0053]

[0054] The above-mentioned IL (ionic liquid) silica has the composition shown in Table 2 below.

[0055] Table 2

[0056]

[0057]

[0058] The quasi-non-combustible slurry coating solution can be prepared using the compositions shown in Tables 3 and 4 below. The composition in Table 4 was used in this embodiment.

[0059] Table 3

[0060]

[0061]

[0062] Table 4

[0063]

[0064]

[0065] The above-mentioned G5 clay (MMT)-nanocompoiste has the composition shown in Table 5 below.

[0066] Table 5

[0067]

[0068] The above-mentioned intumescent flame-retardant composition (FR-IFC) has the composition shown in Table 6 below.

[0069] Table 6

[0070]

[0071]

[0072] The composition of oil-based flame-retardant adhesives is shown in Table 7 below.

[0073] Table 7

[0074]

[0075] The composition of water-based flame retardant adhesives is as follows.

[0076] Table 8

[0077]

[0078] The composition of the polymer foam is shown in Table 9 below. The following compositions were mixed and then compressed to prepare the polymer foam.

[0079] Table 9

[0080]

[0081]

[0082] Experimental Example

[0083] After preparing three test specimens according to the method described in the examples, combustion performance tests were conducted according to KSF ISO 5660-1, and gas toxicity tests of building decoration materials were conducted according to KSF 2271. The results are shown in Table 10 and... Figure 3 As shown in the image.

[0084] Table 10

[0085]

[0086]

[0087] As shown in Table 10 and Figure 3 As shown, the battery cell pad according to the present invention meets the KSF ISO 5660-1 and KSF 2271 test standards. This confirms that the above-mentioned battery cell pad has quasi-non-flammable properties.

Claims

1. A cell pad for secondary batteries, characterized in that, comprising: a polymer foam, carbon fiber composites attached to both sides of the polymer foam, and an adhesive layer between the polymer foam and the fiber composite layer.

2. The battery cell pad according to claim 1, characterized by The carbon fiber composite is prepared by applying a quasi-incombustible sizing containing an intumescent flame-retardant composition to a carbon fiber nonwoven fabric.

3. The battery cell pad of claim 1, wherein The polymer foam is prepared by mixing an intumescent flame-retardant composition, fumed silica, and a blowing agent into a rubber selected from the group consisting of silicone rubber, thermoplastic elastomer, and EPDM rubber, and compression molding.

4. The battery cell pad according to claim 2, wherein In the quasi-incombustible sizing, 80 to 150 parts by weight of the intumescent flame-retardant composition, 40 to 60 parts by weight of aluminum hydroxide, 1 to 10 parts by weight of a montmorillonite aqueous solution, and 1 to 10 parts by weight of a polyoxy(propylene-ethylene) copolymer are contained per 100 parts by weight of a water-soluble epoxy resin or a vinyl acetate ethylene copolymer.

5. The battery cell pad according to claim 2 or 3, characterized by In the intumescent flame-retardant composition, 20 to 40 parts by weight of melamine, 20 to 40 parts by weight of carbamide, and 30 to 50 parts by weight of D-glucitol are contained per 100 parts by weight of ammonium polyphosphate.

6. The battery cell pad of claim 1, wherein The adhesive layer includes an epoxy-based oil-based flame-retardant adhesive or an epoxy-based water-based flame-retardant adhesive.

7. The battery cell pad of claim 2, wherein The carbon fiber nonwoven fabric is treated with a sizing agent including a liquid epoxy resin and a hydrophilic fumed silica.

8. A method for producing an electrode pad for a secondary battery, characterized by, comprising: a step of treating a carbon fiber nonwoven fabric with a sizing agent; a step of applying a quasi-incombustible sizing containing an intumescent flame-retardant composition to the sized carbon fiber nonwoven fabric, drying, and curing to produce a carbon fiber composite; a step of mixing an intumescent flame-retardant composition, fumed silica, and a blowing agent into a rubber selected from the group consisting of silicone rubber, thermoplastic elastomer, and EPDM rubber, and compression molding to produce a polymer foam; a step of applying an epoxy-based adhesive to both sides of the polymer foam and attaching the carbon fiber composite to both sides of the polymer foam; and, a step of heat-treating the attached polymer foam and carbon fiber composite to dry and cure.

9. The method of producing the electrode sheet for a secondary battery according to claim 8, characterized by, In the quasi-incombustible sizing, 80 to 150 parts by weight of the intumescent flame-retardant composition, 40 to 60 parts by weight of aluminum hydroxide, 1 to 10 parts by weight of a montmorillonite aqueous solution, and 1 to 10 parts by weight of a polyoxy(propylene-ethylene) copolymer are contained per 100 parts by weight of a water-soluble epoxy resin or a vinyl acetate ethylene copolymer.

10. The method of producing the electrode sheet for a secondary battery according to claim 8, characterized by, In the intumescent flame-retardant composition, 20 to 40 parts by weight of melamine, 20 to 40 parts by weight of carbamide, and 30 to 50 parts by weight of D-glucitol are contained per 100 parts by weight of ammonium polyphosphate.

Images