Battery thermal runaway prevention sheet and battery cell assembly comprising same

Abstract

The present invention relates to a battery thermal runaway prevention sheet (100) comprising a flame-retardant composite sheet (110), wherein the flame-retardant composite sheet (110) has an upper surface and a lower surface and includes a fiber-reinforced core material and silica, and the flame-retardant composite sheet (110) is manufactured by immersing the fiber-reinforced core material in an impregnation solution containing the silica and has a compression force deflection (CFD) of 0 to 15% points under a pressure of 1.0 to 2.0 MPa, the CFD being calculated by a mathematical formula [high temperature (600 °C or higher) compression rate - room temperature (25 °C) compression rate].

Description

Sheet for preventing battery thermal runaway and battery cell assembly including same

[0001] The present invention relates to a sheet for preventing thermal runaway of a battery and a battery cell assembly including the same, and more particularly, to a sheet for preventing thermal runaway of a battery including a flame-retardant composite sheet manufactured by impregnating a fiber-reinforced core material with an impregnating liquid containing silica, and a battery cell assembly including the same.

[0002] Currently commercially available secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Recently, demand for large-capacity battery modules for use in electronic devices, automobiles, and other applications is increasing. These large-capacity battery modules contain multiple battery cells.

[0003] In these battery modules, if a thermal runaway, fire, or explosion occurs in a portion of a battery cell, fragments, flames, and gases from the electrode assembly may be released, raising the temperature of adjacent battery cells. Consequently, the thermal runaway or fire can spread to adjacent battery cells, potentially causing a secondary fire or explosion of even greater magnitude, potentially exacerbating the damage.

[0004] Korean Patent Publication No. 10-2022-0048433 (Patent Document 1) discloses a battery module including a plurality of battery cells, a module case, a polymer member, and a filler.

[0005] In the case of conventional battery modules, a configuration that uses specific materials to prevent the spread of heat or flames inside has been attempted, but in order to secure sufficient heat resistance, a large amount must be used, and there is also the problem that the cost of these specific materials is high.

[0006] Furthermore, even without considering cost, as input increases, the material loses elasticity, making it difficult to adequately compensate for cell swelling. This negatively impacts battery efficiency.

[0007] Accordingly, conventional battery modules have many difficulties in efficiently ensuring safety against heat, fire, etc.

[0008] [Prior Art Literature]

[0009] (Patent Document 1) Republic of Korea Patent Publication No. 10-2022-0048433 (April 19, 2022)

[0010] One object of the present invention is to provide a sheet for preventing battery thermal runaway, which can effectively ensure safety against heat or fire, etc.

[0011] Another object of the present invention is to provide a battery cell assembly to which a sheet for preventing battery thermal runaway is applied, which can effectively ensure safety against heat or fire, etc.

[0012] The present invention provides a sheet for preventing battery thermal runaway (100), wherein the sheet for preventing battery thermal runaway (100) includes a flame-retardant composite sheet (110), the flame-retardant composite sheet (110) has an upper surface and a lower surface and includes a fiber-reinforced core and silica, the flame-retardant composite sheet (110) is manufactured by impregnating the fiber-reinforced core with an impregnation liquid containing silica, and has a compression force deflection (CFD) of 0 to 15% at a pressure of 1.0 to 2.0 MPa, wherein the compression force deflection (CFD) is calculated by the following mathematical expression 1:

[0013] [Mathematical Formula 1]

[0014] |High temperature (600℃ or higher) compression ratio - Room temperature (25℃) compression ratio|

[0015] The battery thermal runaway prevention sheet according to the present invention reflects the battery operating environment, and the thermal runaway prevention sheet is compressed under the high pressure state generated by cell swelling, and sufficiently delays the high heat generated when cell thermal runaway occurs from being transmitted to adjacent cells, thereby securing time for vehicle occupants to escape from a fire. Specifically, the thermal runaway prevention sheet is normally subjected to the pressure generated by cell swelling, so it must have excellent compression / recovery efficiency, and is in an environment where it may be exposed to high pressure of 2.0 MPa or more due to the gas generated when thermal runaway occurs in a battery cell. When the internal temperature of a cell rises to 600°C due to cell thermal runaway, the heat is transferred to adjacent cells, and when the temperature of the adjacent cells reaches 250°C, continuous thermal runaway occurs. The thermal runaway prevention sheet according to the present invention delays the time for the internal temperature of an exploded cell of 600°C to be transferred to the opposite side under a pressure of 1.0 to 2.0 MPa or more and for the opposite side (the reverse side of the thermal runaway prevention sheet surface that has ignited) to reach 250°C by 5 minutes or more or 10 minutes or more, thereby efficiently ensuring safety against heat or fire, etc., and ensuring time for vehicle occupants to safely escape from the vehicle.

[0016] Additionally, it has a high recovery ability of 90% even in a repetitive cell swelling environment, which assists the cell swelling phenomenon and ensures that the battery's performance can be fully realized.

[0017] Figure 1 schematically shows the structure of a sheet for preventing battery thermal runaway according to the present invention.

[0018] Figure 2 is a scanning electron microscope (SEM) photograph of a sheet for preventing battery thermal runaway according to the present invention.

[0019] Figure 3 is a transmission electron microscope (TEM) photograph of the raw material, silica.

[0020] Fig. 4 is a transmission electron microscope (TEM) photograph of particles impregnated in a sheet for preventing battery thermal runaway of the present invention. The particles of Fig. 4 include silica, silane, and silica sol.

[0021] Figure 5 is a graph of stress versus strain (in percent (%)) representing a compression rate curve.

[0022] Various embodiments of the present invention will be described in detail with reference to the attached drawings below.

[0023] In one aspect, the present invention provides a sheet (100) for preventing battery thermal runaway, which can effectively ensure safety against heat or fire so as to prevent chain fire throughout the entire cell assembly when a fire occurs in a battery cell within the battery cell assembly.

[0024] Figure 1 schematically shows the structure of a sheet for preventing battery thermal runaway according to the present invention.

[0025] Referring to FIG. 1, the battery thermal runaway prevention sheet (100) according to the present invention includes a flame retardant composite sheet (110).

[0026] The flame-retardant composite sheet (110) of the present invention has an upper surface and a lower surface and includes a fiber-reinforced core material and silica. Here, the flame-retardant composite sheet (110) is manufactured by impregnating the fiber-reinforced core material with an impregnation solution containing silica.

[0027] The flame retardant composite sheet (110) has a cushioning function to assist in the swelling phenomenon of the battery cell and acts as an insulating layer to delay heat transfer when thermal runaway occurs.

[0028] The sheet (100) for preventing battery thermal runaway of the present invention has a compression strain of 0 to 15% points at a pressure of 1.0 to 2.0 MPa, and the compression strain is calculated by the following [Mathematical Formula 1].

[0029] [Mathematical Formula 1]

[0030] |High temperature (600℃ or higher) compression ratio - Room temperature (25℃) compression ratio|

[0031] In one specific example, the battery thermal runaway prevention sheet (100) according to the present invention further includes a flame retardant coating layer (120) coated with a flame retardant coating liquid on the upper or lower surface of the flame retardant composite sheet (110).

[0032] The flame-retardant coating layer (120) effectively blocks dust generated from the flame-retardant composite sheet (110), protects the flame-retardant composite sheet (110) from external flames when thermal runaway occurs, and also contributes to some delay in heat transfer.

[0033] Fiber-reinforced core

[0034] The fiber-reinforced core of the present invention includes, but is not limited to, discrete fibers, woven materials, nonwoven materials, batts, batting, webs, mats, felts, or combinations thereof.

[0035] Specifically, the fiber-reinforced core of the present invention comprises at least one selected from, but not limited to, polyester, polyacrylonitrile (PAN), oxidized polyacrylonitrile, non-carbonized heat-treated PAN, carbon, silica, polyaramid, polycarbonate, polyolefin, rayon, nylon, glass wool, high-density polyolefin, ceramic, acrylic, fluoropolymer, polyurethane, polyamide, and polyimide. In addition, the fiber-reinforced core of the present invention may be polyacrylonitrile (PAN), oxidized polyacrylonitrile, non-carbonized heat-treated PAN, or glass fiber.

[0036] In one specific example, the fiber-reinforced core of the present invention contains 30 to 100 wt% of oxidized polyacrylonitrile fiber (OPF) based on the total weight of the fiber-reinforced core. The fiber-reinforced core may have voids present therein.

[0037] For example, the fiber-reinforced core material may be a porous nonwoven fabric containing oxidized polyacrylonitrile fibers (OPF) and having pores therein.

[0038] The OPF of the present invention is a fiber comprising oxidized polyacrylonitrile (Oxi-PAN), and is one of the porous inorganic fiber core materials.

[0039] The fiber-reinforced core of the present invention may have a thermal conductivity of, for example, 0.1 W / m K or less. If the thermal conductivity of the fiber-reinforced core exceeds 0.1 W / m K, the heat of a thermal runaway cell is transferred to a neighboring cell within tens of seconds, rapidly reaching the temperature at which thermal runaway occurs, which makes it difficult to secure sufficient time for a person to escape from the vehicle.

[0040] The fiber-reinforced core of the present invention may also have a thickness of 10 mm or less, or 6 mm or less, or 0.1 to 4 mm. If the thickness of the fiber-reinforced core is 0.1 mm or less, it may be difficult to sufficiently exhibit insulating properties, and if the thickness exceeds 10 mm, although the insulating effect is excellent, there is a problem that the capacity of the battery is reduced due to insufficient internal space of the battery, which limits practical application.

[0041] Meanwhile, the fiber-reinforced core material has a density of 80 to 250 kg / ㎥, or 85 to 230 kg / ㎥. When the fiber-reinforced core material satisfies the above density range, the impregnating solution described below and the particles contained therein can be appropriately distributed on the surface of the fiber-reinforced core material to fill the pores.

[0042] impregnating solution

[0043] In one specific example, the impregnating liquid of the present invention contains silica.

[0044] Silica is distributed and attached to the surface of the fiber-reinforced core yarn, filling the pores. In the present invention, the fiber-reinforced core is impregnated with a silica-containing impregnation solution, allowing the silica to fill the pores of the fiber-reinforced core to a predetermined level. This allows the thermal conductivity of the fiber-reinforced core to be adjusted to a predetermined level, thereby achieving a desirable heat transfer delay effect.

[0045] In one specific example, the impregnating liquid comprises 100 parts by weight of solvent and 3 to 20 parts by weight of silica.

[0046] The solvent is water, preferably distilled water or deionized water. The solvent is included in the impregnating liquid in an amount of 100 parts by weight.

[0047] In addition, the above solvent may be partially mixed with an organic solvent such as alcohol for the purpose of compatibility and storage stability of the additive.

[0048] In the present invention, the silica may be inorganic silica. The inorganic silica may include, for example, one or more selected from fumed silica, precipitated silica, silica glass, and silicon ester, and in one specific example, the inorganic silica may be fumed silica or precipitated silica, and may be fumed silica.

[0049] The above fumed silica is manufactured by hydrolyzing tetrachlorosilane in a flame at a high temperature of 1000℃ or higher, and has a low powder density of approximately 0.05 g / mL and very high silica purity. Fumed silica has a large space between particles, which minimizes heat transfer by gas, and because it has low thermal conductivity, its own heat transfer is also small. In addition, fumed silica is stable and flame-retardant even at high temperatures, so it has an excellent heat retardation effect.

[0050] Figure 3 is a transmission electron microscope (TEM) image of the raw material, silica. Specifically, Figure 3a shows the particle size and distribution of fumed silica. The particles in Figure 3b contain silica, silane, and silica sol. Figure 3b shows that mesopore structures are formed between the fumed silica particles. The distribution of mesopores can effectively block heat transfer by convection, thereby enhancing the heat transfer delay effect.

[0051] Silica is included in the impregnating solution in an amount of 3 to 20 parts by weight, or 5 to 15 parts by weight, based on 100 parts by weight of the solvent. If the silica content exceeds the above range, the heat retardation effect may be reduced.

[0052] In one embodiment, the impregnating liquid may further include one or more of a silane compound, an organic resin, and a silica sol.

[0053] Based on 100 parts by weight of the solvent, the impregnating solution may contain at least one of 0.1 to 15 parts by weight of a silane compound, 0.01 to 10 parts by weight of an organic resin, or more than 0 to 15 parts by weight of silica sol.

[0054] In the present invention, the silane compound reacts with the hydroxyl group of the fiber-reinforced core to further bind the fiber-reinforced core and attaches silica to the surface of the fiber-reinforced core yarn.

[0055] In the present invention, the silane compound may include a difunctional or higher, trifunctional or tetrafunctional alkoxy silane, or a silicone resin in which the number of oxygen atoms bonded per silicon atom is 1 to 4.

[0056] The silane compound of the present invention has the chemical formula (R a SiO 3 / 2 ) a (R b 2SiO 2 / 2 ) b (R c 3SiO1 / 2 ) c It may include a branched chain organopolysiloxane having an average unit of R. Here, R a , R b , and R c are each the same or different and substituted or unsubstituted monovalent hydrocarbon groups, a is a positive number, b is 0 or a positive number, and c is 0 or a positive number.

[0057] Specifically, the silane compounds are tetramethoxy silane, tetraethoxy silane, tetra-n-propoxy silane, tetraisopropoxy silane, tetra-n-butoxy silane, tetraisobutoxy silane, methyltrimethoxy silane, methyltriethoxy silane, ethyltrimethoxy silane, isobutyltrimethoxy silane, vinyltrimethoxy silane, vinyltriethoxy silane, γ-methacryloxypropyltrimethoxy silane, γ-methacryloxypropyltriethoxy silane, γ-acryloxypropyltrimethoxy silane, γ-acryloxypropyltriethoxy silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxy silane, γ-glycidoxypropyltrimethoxy silane, γ-aminopropyltrimethoxy silane, It may be at least one selected from the group consisting of N-β-(aminoethyl)-γ-aminopropyltriethoxy silane, dimethyldimethoxy silane, vinylmethyldimethoxy silane, γ-methacryloxypropylmethyldimethoxy silane, γ-acryloxypropylmethyldimethoxy silane, γ-glycidoxypropylmethyldimethoxy silane, γ-glycidoxypropylmethyldiethoxy silane, γ-aminopropylmethyldimethoxy silane, γ-isocyanatopropyltrimethoxy silane, γ-isocyanatopropyltriethoxy silane, phenyltriethoxy silane, and phenyltrimethoxy silane.

[0058] The silane compound is included in the impregnating solution in an amount of 0.1 to 15 parts by weight, or 0.1 to 10 parts by weight. If the amount of the silane compound is less than the above range, it is difficult to secure physical properties such as strength and water resistance of the manufactured product. If the amount exceeds the above range, the stability of the impregnating solution may be reduced and the strength of the manufactured product may be reduced.

[0059] In the present invention, the organic resin serves as an elastic resin for battery cell swelling. The organic resin may include, for example, an acrylic resin.

[0060] The organic resin is included in the impregnating solution in an amount of 0.01 to 10 parts by weight, or 0.1 to 5 parts by weight, or 0.1 to 3 parts by weight, based on 100 parts by weight of the solvent. If the amount of the organic resin is less than the above range, the elastic effect may be reduced, and if it exceeds the above range, the heat retardation effect may be reduced.

[0061] In the present invention, the silica sol, together with the silane compound, further binds the fiber-reinforced core material and attaches silica to the surface of the fiber-reinforced core material yarn.

[0062] Silica sol is included in the impregnating solution in an amount of 0 to 15 parts by weight, or 0.1 to 10 parts by weight, based on 100 parts by weight of the solvent. If the amount of silica sol exceeds the above range, the strength of the manufactured product may be reduced.

[0063] Flame retardant coating layer (120)

[0064] In one specific example, the battery thermal runaway prevention sheet (100) of the present invention further includes a flame-retardant coating layer (120; 121, 122) coated with a flame-retardant coating liquid on the upper or lower surface of the flame-retardant composite sheet (110). The flame-retardant coating layer (120; 121, 122) protects the flame-retardant composite sheet (110) from fire or heat and enhances the heat delay effect, and can effectively block dust generated from the flame-retardant composite sheet (110).

[0065] In one specific example, the flame retardant coating solution of the present invention comprises 15 to 45 parts by weight of a water-soluble resin, 35 to 85 parts by weight of a flame retardant, 0.1 to 12 parts by weight of an additive, and 0.1 to 15 parts by weight of a solvent.

[0066] The water-soluble resin includes at least one selected from the group consisting of ethylene vinyl acetate (EVA) resin, polyvinylchloride resin, water-soluble acrylic resin, polyvinylacetate (PVAC) resin, polybutadiene resin, polyvinylidene chloride resin, and polyurethane (PU) resin. When ethylene vinyl acetate resin is applied as the water-soluble resin, it is effective because it has strong cohesiveness and can maintain the strength of the flame-retardant coating solution at a certain level or higher.

[0067] The water-soluble resin is included in the flame-retardant coating liquid in an amount of 15 to 45 parts by weight or 18 to 32 parts by weight.

[0068] The flame-retardant coating solution of the present invention may further include a thermoplastic resin to enhance the bonding strength, tensile strength, flexibility, and toughness of the fiber-reinforced core material, and to enhance weather resistance and durability through water resistance, heat resistance, and UV stability. The thermoplastic resin may be, for example, polyvinyl butyral (PVB) resin.

[0069] The flame retardant includes at least one of a phosphorus flame retardant and an inorganic flame retardant.

[0070] The phosphorus-based flame retardant includes at least one selected from the group consisting of ammonium polyphosphate (APP), triphenyl phosphate (TPP), tricresyl phosphate (TCP), triethyl phosphate (TEP), isopropyl phenyl diphenyl phosphate, red phosphorus (CG-P), tris(2-chloroethyl)phosphate (TCEP), phosphorus oxide, tetraphenyl resorcinol bis(diphenylphosphate) (TR), and resorcinol di phosphate (RDP). The phosphorus-based flame retardant of the present invention is a polymer that forms carbonaceous char when thermally decomposed. This char formation reduces combustible fuel and blocks heat by forming a thick barrier on the surface of the burning molecules, thus extinguishing the fire. This process occurs in the condensed phase, and phosphorus is an important condensed phase flame retardant. Phosphorus decomposes thermally to form phosphoric acid, which acts as a dehydration catalyst in the combustible material, increasing the amount of char. The mechanism of char formation is very complex, but phosphorus compounds contain oxygen atoms in their polymer structures, such as PC (Poly Carbonate) and PPO (Poly Phenylene Oxide), and are very effective flame retardants for polymers that form char during combustion. In particular, phosphorus (P)-based flame retardants are environmentally friendly materials that do not generate dioxins, a carcinogen.

[0071] The inorganic flame retardant may be at least one selected from the group consisting of aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), calcium carbonate (CaCO3), magnesium carbonate (MgHCO3), zinc borate, and silica. The inorganic flame retardant may be included for a synergistic effect with the phosphorus-based flame retardant. For example, zinc borate and aluminum hydroxide may be more effective in removing smoke.

[0072] The flame retardant is included in the flame retardant coating liquid in an amount of 35 to 85 parts by weight, or 40 to 75 parts by weight, or 48 to 70 parts by weight. Specifically, the flame retardant may include 10 to 79 parts by weight of an inorganic flame retardant and 1 to 25 parts by weight of a phosphorus flame retardant.

[0073] The additive may include at least one selected from an aqueous dispersant and a pigment. The additive may be included in the flame retardant coating solution in an amount of 0.1 to 12 parts by weight, or 0.1 to 10 parts by weight.

[0074] The solvent comprises water. The solvent may preferably be water and may be included in the flame retardant coating solution in an amount of 0.1 to 15 parts by weight.

[0075] Battery thermal runaway prevention sheet (100)

[0076] In one specific example, the battery thermal runaway prevention sheet (100) of the present invention includes a flame retardant composite sheet (110). Here, the battery thermal runaway prevention sheet (100) may be composed solely of the flame retardant composite sheet (110).

[0077] In another specific example, the battery thermal runaway prevention sheet (100) of the present invention includes a flame retardant composite sheet (110) and a flame retardant coating layer (120; 121, 122).

[0078] The flame retardant composite sheet (110) of the present invention is manufactured by impregnating a fiber-reinforced core material with an impregnation solution containing silica.

[0079] In the flame retardant composite sheet (110), the fiber reinforcing core and the impregnating agent may have a weight ratio of 1:0.3 to 1:3, or 1:0.6 to 1:2, or 1:0.8 to 1:1.5, based on the solid content of the impregnating agent.

[0080] If the core material impregnation ratio (ratio of core material to solids of impregnating solution) is less than 1:0.3, the pressure-resistant properties are reduced, which can significantly reduce the insulation effect under high pressure conditions that occur during thermal runaway. If the core material impregnation ratio exceeds 1:3, the sheet becomes hard and cannot support cell swelling, and its brittleness increases, putting it at risk of breaking.

[0081] In one specific example, the fiber-reinforced core has a density of 80 to 250 kg / m3. Meanwhile, the flame-retardant composite sheet (110) manufactured by impregnating the fiber-reinforced core with the impregnating solution has a density of 100 to 1,100 kg / m2. Specifically, the density of the flame-retardant composite sheet (110) manufactured by impregnating the fiber-reinforced core with a density of 80 to 250 kg / m3 with the impregnating solution is 100 to 1,100 kg / m2.

[0082] In one specific example, the battery thermal runaway prevention sheet (100) of the present invention is exposed to a pressure of 1.0 to 2.0 MPa and a high temperature of 600°C, and the time for the temperature of the opposite side to reach 250°C is 5 minutes or more, or 7 minutes or more, or 9 minutes or more, or 10 minutes or more.

[0083] In one specific example, the sheet (100) for preventing battery thermal runaway of the present invention has a high-temperature compression ratio of 40 to 85% at a pressure of 1.0 to 2.0 MPa and a temperature of 600°C. A lower high-temperature compression ratio is advantageous for insulation in the event of thermal runaway, and the minimum value of the high-temperature compression ratio can be determined according to the swelling characteristics of the battery cell.

[0084] Accordingly, the sheet (100) for preventing battery thermal runaway of the present invention, which includes a fiber-reinforced core and silica, has a compression strain (Compression Force Deflection, CFD), which is the difference between the compression ratio at room temperature (25°C) and the compression ratio at high temperature (600°C or higher), of 0 to 15% points, or 0 to 10% points, or 0 to 7% points, at a pressure of 1.0 to 2.0 MPa. When the compression strain of the sheet (100) for preventing battery thermal runaway is outside the above range, there is a problem in that the thermal delay time is reduced.

[0085] The compressive strain (CFD) is calculated by the following [Mathematical Formula 1] at a pressure of 1.0 to 2.0 MPa, and the insulation properties of the sheet (100) for preventing battery thermal runaway decrease as the difference between the room temperature compression ratio value and the high temperature compression ratio value increases.

[0086] [Mathematical Formula 1]

[0087] |High temperature (600℃ or higher) compression ratio - Room temperature (25℃) compression ratio|

[0088] Here, the sheet (100) for preventing battery thermal runaway of the present invention has a room temperature compression ratio of 40 to 75% at 25°C, and a high temperature compression ratio of 600°C or higher (e.g., 600 to 1,200°C, or 600 to 800°C) of 40 to 85%.

[0089] Accordingly, the sheet (100) for preventing battery thermal runaway of the present invention, as shown in FIG. 5, has a small compressive strain (CFD) value and thus maintains its shape or thickness at room temperature even when exposed to a high temperature of 600°C or higher and a high pressure of 1.0 MPa or higher, thereby being effective in thermal delay.

[0090] In the present invention, the compression ratio of the sheet (100) for preventing battery thermal runaway is measured according to the ISO3386 standard and calculated by [Mathematical Formula 2] below.

[0091] [Equation 2]

[0092]

[0093] Fig. 2 is a scanning electron microscope (SEM) photograph of a sheet for preventing battery thermal runaway according to the present invention. Specifically, Fig. 2 is an SEM photograph of a flame-retardant composite sheet (110) of the present invention, and the distribution of the impregnated material between actual fibers can be confirmed.

[0094] Fig. 4 is a transmission electron microscope (TEM) photograph of particles impregnated in a sheet for preventing battery thermal runaway of the present invention. Fig. 4 shows the shape of particles formed when fumed silica and silica sol are cured with a silane compound.

[0095] Battery cell assembly

[0096] In another aspect, the present invention provides a battery cell assembly to which a sheet (100) for preventing battery thermal runaway according to the present invention is applied.

[0097] Specifically, the battery cell assembly of the present invention comprises a plurality of battery cells each wrapped by a battery thermal runaway prevention sheet (100) according to the present invention. Due to this configuration, the battery cell assembly of the present invention can prevent a chain reaction of fires across the entire plurality of battery cells when a fire occurs in at least one battery cell.

[0098] [Example]

[0099] 1. Preparation of fiber-reinforced core material

[0100] As a fiber-reinforced core material of an example, commercially available OPF (oxidized polyacrylonitrile fiber) was prepared, and as a fiber-reinforced core material of a comparative example, commercially available ceramic paper was prepared.

[0101] The OPF used is a product of TFJ Company, and the ceramic paper is Bio Cerakwool Paper of KCC Company.

[0102] 2. Preparation of impregnating solution

[0103] Each component was placed in a reaction vessel and mixed to prepare an impregnation solution. The composition of each component is presented in [Table 1].

[0104]

[0105] - MTMS: Methyltrimethoxysilane

[0106] 3. Manufacturing of flame retardant coating solution

[0107] Each component was placed in a reaction vessel and mixed to prepare a flame-retardant coating solution. The composition of each component is presented in [Table 2].

[0108]

[0109] - TR: Tetraphenyl resorcinol bis(disphenyl phosphate)

[0110] 4. Manufacturing of sheet (100) to prevent battery thermal runaway

[0111] 4-1. Manufacturing of flame retardant composite sheet (110)

[0112] A flame-retardant composite sheet was manufactured by impregnating the prepared fiber-reinforced core material with the manufactured impregnation solution.

[0113] Specifically, the fiber-reinforced core material was cut into a size of 300 mm x 300 mm x 4 mm, immersed in a bath containing an impregnating solution for 5 seconds, and then dried in an oven at 150°C for 60 minutes to harden. The amount of impregnating solution impregnated in the fiber-reinforced core material is the ratio of the increased weight of the fiber-reinforced core material after impregnation, drying, and hardening to the weight of the fiber-reinforced core material before impregnation.

[0114] 4-2. Manufacturing of a sheet (100) to prevent battery thermal runaway

[0115] A flame-retardant coating layer was formed by coating the manufactured flame-retardant coating solution on both sides of the manufactured flame-retardant composite sheet.

[0116] An experimental example flame retardant composite sheet (110) and a battery thermal runaway prevention sheet (100) were manufactured by changing the impregnation content of the impregnating liquid, and these are presented in Table 3.

[0117]

[0118] [Performance Evaluation of Sheets to Prevent Battery Thermal Runaway]

[0119] The thermal transfer delay time and compression ratio of the battery thermal runaway prevention sheet manufactured in the experimental example were measured and presented in Table 4 below.

[0120] (i) Heat transfer delay time

[0121] The manufactured battery thermal runaway prevention sheet was inserted into a measuring device, and the entire electric furnace inlet heated to 600°C was shielded after applying a pressure of 1.5 MPa. The time it took for the temperature of the opposite side to reach 250°C was measured, and the value obtained by subtracting the time it took to reach 250°C when there was no battery thermal runaway prevention sheet was recorded.

[0122] For example, if it takes 5 minutes for the temperature on the opposite side of the measuring device to reach 250°C without a battery thermal runaway prevention sheet, and 10 minutes for the temperature on the opposite side of the measuring device to reach 250°C with a battery thermal runaway prevention sheet inserted, the delay time is calculated to be 5 minutes (300 seconds). The evaluation criterion is that a thermal transfer delay time of 5 minutes or longer is judged to be excellent.

[0123] (ii) Whether or not a flame occurs

[0124] The occurrence of flames was visually confirmed.

[0125] (iii) Compression ratio

[0126] The compression ratio of the manufactured battery thermal runaway prevention sheet was measured according to mathematical formula 1.

[0127] The evaluation criteria were judged to be excellent if the room temperature compressibility was 40 to 75% under 1.5 MPa conditions and the high temperature compressibility at 600°C or higher was 40 to 85%.

[0128]

[0129] According to Table 4, for Experimental Examples 20 to 23, the heat transfer times were 145 seconds, 150 seconds, 130 seconds, and 240 seconds, respectively, which were less than the standard time of 5 minutes, and the high-temperature compressibility was also 91%, 94%, 97%, and 90%, respectively, which was less than the standard compressibility of 85% or less. Moreover, it was confirmed that the compressive strain was not effective for heat delay, as it was 16% points, 16% points, and 17% points, which is more than 15 percentage points in Experimental Examples 20 to 22. That is, when an impregnation solution that did not contain silica was applied to the fiber-reinforced core, or when only the fiber-reinforced core was applied without an impregnation solution, it was confirmed that the heat delay effect was reduced because the compressive strain exceeded 15 percentage points.

[0130] Hereinafter, various embodiments of the present invention will be described.

[0131] Specific example 1. In a sheet (100) for preventing battery thermal runaway, the sheet (100) for preventing battery thermal runaway includes a flame retardant composite sheet (110), the flame retardant composite sheet (110) has an upper surface and a lower surface and includes a fiber-reinforced core and silica, the flame retardant composite sheet (110) is manufactured by impregnating the fiber-reinforced core with an impregnation solution containing the silica, and has a compression force deflection (CFD) of 0 to 15% points at a pressure of 1.0 to 2.0 MPa, wherein the compression force deflection (CFD) is calculated by the following mathematical expression 1:

[0132] [Mathematical Formula 1]

[0133] |High temperature (600℃ or higher) compression ratio - Room temperature (25℃) compression ratio|

[0134] Specific example 2. In specific example 1, the sheet (100) for preventing battery thermal runaway has a room temperature compression ratio of 40 to 75% at 25°C and a high temperature compression ratio of 40 to 85% at 600°C or higher.

[0135] Specific example 3. In Specific example 1, the fiber-reinforced core material is a sheet for preventing battery thermal runaway, wherein the fibers of the fiber-reinforced core material include at least one selected from polyester, polyacrylonitrile (PAN), oxidized polyacrylonitrile, non-carbonized heat-treated PAN, carbon, silica, polyaramid, polycarbonate, polyolefin, rayon, nylon, glass wool, high-density polyolefin, ceramic, acrylic, fluoropolymer, polyurethane, polyamide, and polyimide.

[0136] Specific example 4. In specific example 3, the fiber-reinforced core contains 30 to 100 wt% of oxidized polyacrylonitrile fiber (OPF) based on the total weight of the fiber-reinforced core, and a sheet for preventing battery thermal runaway having voids inside.

[0137] Specific example 5. A sheet for preventing battery thermal runaway, wherein in Specific example 1, the fiber-reinforced core material and the impregnating liquid have a weight ratio of 1:0.3 to 1:3 based on the solid content of the impregnating liquid.

[0138] Specific example 6. A sheet for preventing battery thermal runaway, wherein in Specific example 1, the fiber-reinforced core has a density of 80 to 250 kg / ㎥, and the flame-retardant composite sheet (110) has a density of 100 to 1,100 kg / ㎡.

[0139] Specific example 7. A sheet for preventing battery thermal runaway, wherein the impregnating liquid according to Specific example 1 contains 100 parts by weight of a solvent and 3 to 20 parts by weight of the silica.

[0140] Specific example 8. A sheet for preventing battery thermal runaway, wherein in Specific example 7, the impregnating liquid further comprises at least one of 0.1 to 15 parts by weight of a silane compound, 0.01 to 10 parts by weight of an organic resin, and more than 0 to 15 parts by weight of silica sol.

[0141] Specific example 9. A sheet for preventing thermal runaway of a battery, wherein in Specific example 7, the solvent is water, and the silica includes at least one selected from fumed silica, precipitated silica, silica glass, and silicon ester.

[0142] Specific example 10. A sheet for preventing battery thermal runaway, further comprising a flame-retardant coating layer (120) coated with a flame-retardant coating liquid on the upper or lower surface of the flame-retardant composite sheet (110) in Specific example 1.

[0143] Specific example 11. A sheet for preventing battery thermal runaway, wherein the flame retardant coating liquid of Specific example 9 comprises 15 to 45 parts by weight of a water-soluble resin, 35 to 85 parts by weight of a flame retardant, 0.1 to 12 parts by weight of an additive, and 0.1 to 15 parts by weight of a solvent.

[0144] Specific example 12. In specific example 11, the water-soluble resin includes at least one selected from the group consisting of ethylene vinylacetate (EVA) resin, polyvinylchloride resin, water-soluble acrylic resin, polyvinylacetate (PVAC) resin, polybutadiene resin, polyvinylidene chloride resin, and polyurethane (PU) resin, the flame retardant includes at least one of a phosphorus flame retardant and an inorganic flame retardant, the additive includes at least one of an aqueous dispersant and a pigment, and the solvent includes water. A sheet for preventing battery thermal runaway.

[0145] Specific example 13. In Specific example 1, the sheet for preventing battery thermal runaway is a sheet for preventing battery thermal runaway, wherein the time for the temperature of the opposite side to reach 250°C is 5 minutes or more when exposed to a pressure of 1.0 to 2.0 MPa and a high temperature of 600°C.

[0146] Specific example 14. A battery cell assembly comprising a plurality of battery cells each wrapped by a battery thermal runaway prevention sheet (100) according to any one of Specific examples 1 to 13, characterized in that when a fire occurs in at least one battery cell, a chain fire of the plurality of battery cells is prevented.

[0147] [Explanation of symbols]

[0148] 100: Sheet to prevent battery thermal runaway

[0149] 110: Flame retardant composite sheet

[0150] 120, 121, 122: Flame retardant coating layer

Claims

1. In the sheet (100) for preventing battery thermal runaway, The above battery thermal runaway prevention sheet (100) includes a flame retardant composite sheet (110), and has a compression force deflection (CFD) of 0 to 15% points at a pressure of 1.0 to 2.0 MPa. The above flame retardant composite sheet (110) has an upper surface and a lower surface and includes a fiber-reinforced core material and silica, Here, the compressive strain (CFD) is calculated by the following mathematical formula 1: Sheet for preventing battery thermal runaway: [Mathematical Formula 1] |High temperature (600℃ or higher) compression ratio - Room temperature (25℃) compression ratio|.

2. In claim 1, The above flame retardant composite sheet (110) is a sheet for preventing battery thermal runaway, manufactured by impregnating the fiber-reinforced core material with an impregnation liquid containing the silica.

3. In claim 1, The above battery thermal runaway prevention sheet (100) is a battery thermal runaway prevention sheet having a room temperature compression ratio of 40 to 75% at 25°C and a high temperature compression ratio of 40 to 85% at 600°C or higher.

4. In claim 1, The above fiber-reinforced core material is a sheet for preventing battery thermal runaway, wherein the fibers of the fiber-reinforced core material include at least one selected from polyester, polyacrylonitrile (PAN), oxidized polyacrylonitrile, non-carbonized heat-treated PAN, carbon, silica, polyaramid, polycarbonate, polyolefin, rayon, nylon, glass wool, high-density polyolefin, ceramic, acrylic, fluoropolymer, polyurethane, polyamide, and polyimide.

5. In claim 4, A sheet for preventing battery thermal runaway, wherein the fiber-reinforced core contains oxidized polyacrylonitrile fiber (OPF) in an amount of 30 to 100 wt% based on the total weight of the fiber-reinforced core and has voids inside.

6. In claim 1, A sheet for preventing battery thermal runaway, wherein the fiber-reinforced core and the impregnating liquid have a weight ratio of 1:0.3 to 1:3 based on the solid content of the impregnating liquid.

7. In claim 1, The above fiber-reinforced core material has a density of 80 to 250 kg / ㎥, The above flame retardant composite sheet (110) is a sheet for preventing battery thermal runaway, having a density of 100 to 1,100 Kg / ㎡.

8. In claim 1, A sheet for preventing battery thermal runaway, wherein the impregnating liquid comprises 100 parts by weight of a solvent and 3 to 20 parts by weight of the silica.

9. In claim 8, A sheet for preventing thermal runaway of a battery, wherein the impregnating liquid further comprises at least one of 0.1 to 15 parts by weight of a silane compound, 0.01 to 10 parts by weight of an organic resin, and more than 0 to 15 parts by weight of silica sol.

10. In claim 8, The above solvent is water, A sheet for preventing thermal runaway of a battery, wherein the silica comprises at least one selected from fumed silica, precipitated silica, silica glass, and silicon ester.

11. In claim 1, A sheet for preventing battery thermal runaway, further comprising a flame-retardant coating layer (120) coated with a flame-retardant coating liquid on the upper or lower surface of the flame-retardant composite sheet (110).

12. In claim 11, A sheet for preventing battery thermal runaway, wherein the flame retardant coating liquid comprises 15 to 45 parts by weight of a water-soluble resin, 35 to 85 parts by weight of a flame retardant, 0.1 to 12 parts by weight of an additive, and 0.1 to 15 parts by weight of a solvent.

13. In claim 12, The water-soluble resin includes at least one selected from the group consisting of ethylene vinylacetate (EVA) resin, polyvinylchloride resin, water-soluble acrylic resin, polyvinylacetate (PVAC) resin, polybutadiene resin, polyvinylidene chloride resin, and polyurethane (PU) resin. The above flame retardant includes at least one of a phosphorus flame retardant and an inorganic flame retardant, The above additive comprises at least one of a water-based dispersant and a pigment, A sheet for preventing battery thermal runaway, wherein the solvent comprises water.

14. In claim 1, The above battery thermal runaway prevention sheet (100) is a battery thermal runaway prevention sheet in which the temperature of the opposite side reaches 250°C in 5 minutes or more when exposed to a pressure of 1.0 to 2.0 MPa and a high temperature of 600°C.

15. A battery comprising a plurality of battery cells each wrapped by a sheet (100) for preventing battery thermal runaway according to any one of claims 1 to 14, A battery cell assembly characterized in that, when a fire occurs in at least one battery cell, a chain reaction of fire to all of the battery cells is prevented.

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