Battery pack containing polysiloxane composite material and method for manufacturing the same

Abstract

A battery pack comprising a polysiloxane composite material and a method for manufacturing the same are provided. The battery pack comprises a polysiloxane composite material which partially or completely fills the gap between two adjacent battery cells and has an average cell size of 100 μm or less, which is much smaller than silicone foam materials / pads made from similar silicone foam compositions except for the use of a chemical foaming agent. The polysiloxane composite material has a wide range of adjustable compressibility compared to common silicone syntactic foams which are not very compressible.

Description

[Technical Field]

[0001] This disclosure relates to a battery pack containing a polysiloxane composite material and a method for manufacturing the same. [Background technology]

[0002] As an agreed-upon strategy to control carbon dioxide emissions and mitigate global warming caused by greenhouse gases, electric vehicles (EVs) powered by lithium-ion secondary batteries (LiBs) are rapidly increasing in major regions of the world. To increase the driving range per charge, EV battery manufacturers are continuously increasing the energy density of the battery's cathode and anode materials, producing individual cells with increasingly larger capacities. As a result, the amount of heat generated during thermal runaway in individual cells continues to increase. To ensure the safe evacuation of passengers, insulating sheet materials should be positioned between adjacent cells to delay heat transfer, providing sufficient protection to healthy cells next to the thermally runaway cell.

[0003] A typical thermal insulation sheet used in the industry is an aerogel sheet, which is made by compressing aerogel powder into a woven mat. The aerogel powder provides thermal insulation, and the woven mat holds the powder together in the form of a sheet. However, due to its inherent low density and insufficient van der Waals forces between particles, the aerogel powder on the sheet surface can easily diffuse into the atmosphere during handling, causing contamination of the work environment. There is a strong demand in the EV battery industry for a method to develop a fireproof sheet with good thermal insulation performance and a clean work environment for the battery assembly process. Silicone rubber foam was expected to be a reasonable alternative because the rubber itself can be ceramicized at sufficiently high temperatures and therefore can still exist between a thermally runaway cell and a good cell next to it. However, inherent silicone rubber foam does not have sufficiently high thermal insulation performance after ceramicization. Thermal insulation performance is evaluated by a hot plate test, which is intended to simulate a thermal runaway scenario. At a certain hot plate temperature (e.g., 600°C), the back temperature of a silicone foam pad of a certain thickness should be sufficiently low after a certain heating time. This is to ensure that the next cell does not heat up to that temperature during the exhaust time. Developing new battery packs to provide better insulation performance remains a major challenge.

[0004] Patent Document 1 discloses a secondary battery pack comprising: 1) at least one battery module casing in which a plurality of battery cells electrically connected to each other are arranged; and 2) a silicone rubber syntactic foam comprising a silicone rubber binder and hollow glass beads. The silicone rubber syntactic foam partially or completely fills the open spaces of the battery module casing and / or partially or completely covers the battery cells and / or partially or completely covers the module casing and optionally covers a lid that covers the battery module casing. The silicone rubber syntactic foam is obtained by curing an addition-curing organopolysiloxane composition X, which comprises a) at least one organopolysiloxane A having alkenyl groups, each containing at least two alkenyl groups per molecule bonded to silicon, with each alkenyl group containing 2 to 14 carbon atoms; b) at least one silicon compound B having at least two hydrogen atoms per molecule bonded to silicon; c) hollow glass beads D; and d) a hydrosilylation catalyst C. However, the silicone rubber syntactic foam is not very compressible due to the hard walls of the hollow glass beads.

[0005] Patent Document 2 discloses a battery module comprising a plurality of battery cells, at least one insulating layer, a support member surrounding at least a portion of the insulating layer, and one or more insulating barriers including the sealing layer, the sealing layer in contact with at least a portion of the support member, wherein the sealing layer has a thermal conductivity of less than about 0.05 W / mK at 25°C and less than 0.06 W / mK at 600°C. The insulating layer may further contain aerogel. However, such a multilayer structure can increase process complexity.

[0006] Patent Document 3 discloses an insulating / protective barrier operablely adapted to be placed between adjacent battery cells in a battery pack or module, comprising a cured silicone rubber non-syntactic foam layer having at least one main surface, and at least one optional solid film, the solid film being positioned to cover at least one main surface of the silicone rubber foam layer, the silicone rubber foam layer containing a plurality of solidified particles positioned within the silicone rubber foam layer in an amount sufficient to impart additional hardness to the silicone rubber foam layer, and consequently requiring a greater compressive force to compress the foam layer to a desired compression value compared to the same silicone rubber foam layer without solidified particles. Such an insulating / protective barrier requires that the solidified particles be uniformly distributed and positioned within the silicone foam, which increases process complexity. Furthermore, while the addition of solidified particles can result in higher compressive resistance, it does not necessarily improve the insulating performance. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent Publication No. 10501597 (B2) [Patent Document 2] International Patent Publication No. 2023 / 279090(A) [Patent Document 3] International Patent Publication No. 2023 / 037270(A) [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that this invention aims to solve is how to delay or prevent the propagation of thermal runaway in an EV battery pack by improving the thermal insulation performance of protective materials positioned between cells while maintaining good mechanical performance.

[0009] Furthermore, another object of the present invention is to provide a process for producing such polysiloxane composite materials. [Means for solving the problem]

[0010] As a result of persistent research, the inventors have discovered a novel battery pack containing a cured polysiloxane composite material that exhibits significantly reduced thermal conductivity at high temperatures, such as 600°C, and possesses excellent mechanical properties.

[0011] One aspect of the present invention is a battery pack comprising a polysiloxane composite material, wherein the polysiloxane composite material partially or completely fills the gap between two adjacent battery cells, and the battery pack has an average cell size of 100 μm or less.

[0012] In some embodiments, the polysiloxane composite material has a closed-cell ratio of 50% or more.

[0013] In some embodiments, the polysiloxane composite material is (A) At least one organopolysiloxane having at least two alkenyl groups bonded to silicon per molecule, (B) At least one organopolysiloxane having at least two hydrogen atoms bonded to silicon per molecule, (C) Hydrosilylation catalyst and (D) at least one flame-retardant filler, (E) Obtained by curing a curable silicone composition containing water.

[0014] In some embodiments, based on 100 parts by weight of component (A), component (B) is in the amount of 0.5 to 20 parts by weight, and / or component (D) is in the amount of 2 to 250 parts by weight.

[0015] In some embodiments, component (E) is in an amount of 5 to 1000 parts by weight, based on 100 parts by weight of component (A).

[0016] In some embodiments, the curable silicone-based composition F) further comprises at least one thickener in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of component (E).

[0017] In some embodiments, the curable silicone-based composition (G) at least one emulsifier, (H) at least one hydrosilylation catalyst inhibitor, and / or (I) at least one opacifier.

[0018] In some embodiments, the thickener (F) is selected from the group consisting of nanoclay, cellulose, polyacrylate, and mixtures thereof.

[0019] In some embodiments, the emulsifier (G) is selected from the group consisting of polysiloxane polyether, alkyl-poly(ethylene oxide), and mixtures thereof.

[0020] In some embodiments, the opacifier (I) is selected from the group consisting of carbon black, Fe3O4, and mixtures thereof.

[0021] A second aspect of the present invention is a process for manufacturing a cured polysiloxane composite material for a battery pack, which Step (I): providing a mixture comprising components (A), (B), (C), and (D); Step (II): applying component (E) into the mixture under mixing and shearing conditions to provide a water-in-oil emulsion containing water droplets having an average droplet size of 100 μm or less; Step (III): heating the water-in-oil emulsion to cure the polysiloxane matrix and form a cured wet composite material; Step (IV): assembling the cured composite material between cells in a battery pack.

[0022] In some embodiments, the process Step (I'): Further comprising applying component (F) to component (E) under mixing and shearing conditions prior to step (I) and / or (II) to provide a thickened component (E).

[0023] In some embodiments, step (II) further includes applying components (G), (H), and / or (I) into the mixture under mixing and shearing conditions.

[0024] In some embodiments, the method is Step (V): Further comprising partially or completely removing water from the wet polysiloxane composite material formed in Step (III).

[0025] Effects of the invention The present invention can provide a battery pack comprising a polysiloxane composite material that partially or completely fills the gap between two adjacent battery cells having an average cell size of 100 μm or less, which is much smaller than silicone foam materials / pads made from similar silicone foam compositions, except that chemical and / or physical foaming agents are used. Furthermore, the polysiloxane composite material has good mechanical properties, such as a wide range of adjustable compressibility, compared to common silicone syntactic foams which are not very compressible. The battery pack of the present invention can exhibit good thermal insulation performance, even if it is not designed in a multilayer laminated structure.

[0026] Please understand that both the general description above and the detailed description below are illustrative and descriptive, and do not limit the claimed invention. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic diagram of an apparatus for testing the thermal insulation performance of silicone foam materials according to this disclosure. [Figure 2] This is an SEM image of Comparative Example 1 according to the present invention. [Figure 3] This is an SEM image of Comparative Example 2 according to the present invention. [Figure 4] This is an SEM image of Example 1 according to the present invention. [Figure 5] This is an SEM image of Example 2 according to the present invention. [Figure 6] This is an SEM image of Example 3 according to the present invention. [Figure 7] This is an SEM image of Example 4 according to the present invention. [Figure 8] This is an SEM image of Example 5 according to the present invention. [Figure 9] This is an SEM image of Example 6 according to the present invention. [Modes for carrying out the invention]

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art in which the invention pertains. Where disclosed herein, “and / or” means “and, or alternatively” or “in addition, or alternatively.” All scopes include the endpoint unless otherwise indicated.

[0029] As used herein, the term “thickness” refers to the average of at least three measurements of a dry sheet (e.g., a sheet having a thickness of 0.2 to 10.0 mm) measured using an Ames Gage, Model 13C-B2600 (Ames Corporation Waltham Mass).

[0030] As used herein, the terms “polymer” or “polymeric” selectively refer to polymers made from one or more different monomers, such as copolymers, terpolymers, tetrapolymers, and pentapolymers, and may be random, block, graft, continuous, or gradient polymers.

[0031] In this invention, the singular articles “a,” “an,” and “the” include plural references unless otherwise indicated. In this invention, the terms “comprise,” “comprising,” “contain,” “containing,” “include,” and “including,” and their variations, are the language of non-restrictive claims, i.e., allow for additional elements.

[0032] According to the present invention, the battery pack may include a polysiloxane composite material that partially or completely fills the gap between two adjacent battery cells and has an average cell size of 100 μm or less, 80 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, or 5 μm or less. In alternative embodiments of this application, the average cell size of the polysiloxane composite material is 100 nm, 300 nm, 500 nm, 800 nm, or 1 μm or more.

[0033] In preferred embodiments, the polysiloxane composite material has a closed cell ratio of 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 99% or more.

[0034] In some embodiments of the present invention, polysiloxane composite materials can be obtained, for example, by curing a curable silicone-based composition via an emulsion curing process, the emulsion curing process comprising, or substantially comprising, or consisting thereof, (A) at least one organopolysiloxane having at least two alkenyl groups bonded to silicon per molecule, (B) at least one organopolysiloxane having at least two hydrogen atoms bonded to silicon per molecule, (C) a hydrosilylation catalyst, (D) at least one flame retardant filler, (E) water, (F) optionally at least one thickener, (G) optionally at least one emulsifier, (H) optionally at least one hydrosilylation catalyst inhibitor, and / or (I) optionally at least one opacifier.

[0035] Ingredient (A) In the present invention, component (A) is well known in the art, and an example thereof includes an alkenyl-terminated block polyorganosiloxane (i.e., vinyl-terminated PDMS) of the following formula:

[0036] [ka] In the formula, R 3 and R 4 R is selected from the group consisting of alkyl groups, phenyl groups, and alkenyl groups, each having 1 to 6 carbon atoms per group. 4 At least 50% of the components are methyl groups. Preferably, the viscosity of component (A) at 25°C is 100 cst to 200,000 cst, 1,000 cst to 100,000 cst, 5,000 cst to 50,000 cst, 8,000 cst to 16,000 cst, 8,000 cst to 14,000 cst, 8,000 cst to 12,000 cst, or 8,000 cst to 10,000 cst.

[0037] In some embodiments of this disclosure, the alkenyl group contained in component (A) may consist of 2 to 14 carbon atoms, 4 to 12 carbon atoms, or 6 to 10 carbon atoms, preferably the alkenyl group is selected from the group consisting of vinyl, allyl, hexenyl, decenyl, and tetradecenyl, most preferably the alkenyl group is a vinyl group.

[0038] Particularly preferably, component (A) can be incorporated into the curable silicone composition in amounts of 20% to 90% by weight, 30% to 80% by weight, 40% to 70% by weight, or 50% to 60% by weight, based on the total amount of the curable silicone composition.

[0039] Ingredient (B) In the present invention, component (B) may be used to adjust the crosslinking density and may be any silicone having at least two silicon-bonded hydrogen atoms on average per molecule. The remaining valences of the silicon atoms are filled with divalent oxygen atoms or monovalent alkyl radicals having 1 to 6 carbon atoms per radical, such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, and phenyl groups. The organohydrogen silicone may be a homopolymer, copolymer, or mixture thereof. Preferably, the organohydrogen silicone includes, but is not limited to, a copolymer of trimethylsiloxy and methylhydrogen silicone, or a copolymer of trimethylsiloxy, methylhydrogen silicone, and dimethyl silicone. In one embodiment of the present invention, the organohydrogen silicone has at least three silicon-bonded hydrogen atoms on average per molecule. In one embodiment of the present invention, the viscosity of component (B) is 1 cst to 500 cst, 2 cst to 300 cst, 5 cst to 100 cst, 10 cst to 80 cst, 10 cst to 60 cst, 10 cst to 40 cst, or 10 cst to 20 cst at 25°C. In one embodiment of the present invention, component (B) contains 0.01 to 1.67% by weight, 0.02 to 1.5% by weight, 0.05 to 1.3% by weight, 0.1 to 1.1% by weight, 0.2 to 1.0% by weight, 0.4 to 0.8% by weight, or 0.5 to 0.6% by weight of SiH. In one embodiment of the present invention, component (B) is a hydrogenated silicone oil having a viscosity of 20 cst at 25°C and about 1.6% by weight of SiH.

[0040] Particularly preferably, component (B) may be incorporated into the curable silicone composition in an amount of 4% to 20% by weight, 6% to 16% by weight, or 8% to 14% by weight, for example, 12% by weight, based on the total amount of the curable silicone composition.

[0041] In some embodiments of the present invention, component (B) may have an amount of 0.2 to 20 parts by weight, 0.5 to 18 parts by weight, 1 to 16 parts by weight, 2 to 14 parts by weight, 5 to 10 parts by weight, or 7 to 9 parts by weight, based on 100 parts by weight of component (A).

[0042] Ingredients (C) In the present invention, component (C) may be selected from the group consisting of platinum, palladium, rhodium, nickel, iridium, ruthenium catalysts, and mixtures thereof, and is preferably a platinum catalyst, which can efficiently promote the reaction of the -SiH group with the vinyl group. Particularly preferred is a two-component curable silicone composition in which the catalyst is an organic platinum compound. Particularly preferred is a two-component curable silicone composition in which the catalyst is a functional organic platinum compound selected from (η-diolefin)(α-aryl)platinum complex, (η-diolefin)(γ-aryl)platinum complex, (η-diolefin)(γ-alkyl)platinum complex, and mixtures thereof. In the present invention, commercially available products can be used.

[0043] Particularly preferably, component (C) may be incorporated into the curable silicone composition in an amount of 0.1% to 2% by weight, 0.5% to 1.5% by weight, or 0.8% to 1.3% by weight, for example, 1.2% by weight, based on the total amount of the curable silicone composition.

[0044] In some embodiments of the present invention, component (C) may have an amount of 0.1 to 2 parts by weight, 0.5 to 1.5 parts by weight, 0.8 to 1.3 parts by weight, or 0.9 to 1.1 parts by weight, based on 100 parts by weight of component (A).

[0045] Ingredients (D) In the present invention, component (D) can further improve flame retardancy. Generally, based on 100 parts by weight of component (A), flame retardant additives may be present in amounts of 2-250% by weight, 5-200% by weight, 10-150% by weight, 15-120% by weight, 15-100% by weight, 20-80% by weight, or 30-50% by weight, depending on the flame retardancy requirements of the polysiloxane composite material. The flame retardant additives may include non-combustible fibers and sulfur-free carbon black. The non-combustible fibers are thought to help retain the char formed when the composite material is exposed to flame, protecting the composite material beneath the carbonized surface. The non-combustible fibers may be selected from fibers such as carbon fibers, ceramic fibers, and aramid fibers, with ceramic fibers being preferred. The fibers must be fine fibers having an average diameter of less than 5 micrometers and a length of less than 100 millimeters so that the fibers can be uniformly and easily distributed throughout the mixture. Preferably, 1 to 5 weight percent of non-flammable fibers and 1 to 5 weight percent of sulfur-free carbon black are present. The added carbon black may be any of the ordinary sulfur-free carbon blacks used as additives in platinum-catalyzed silicone elastomers. The carbon black is sulfur-free because sulfur can interfere with curing.

[0046] In some embodiments of this disclosure, the flame retardant additive includes, but is not limited to, halogenated flame retardants and / or non-halogenated flame retardants. Examples of halogenated flame retardants include brominated polymers or oligomers, brominated styrene-butadiene-styrene copolymers, and preferably combinations of brominated flame retardants with antimony trioxide to form a Br-Sb synergy. Examples of non-halogenated flame retardants may include, but are not limited to, aluminum hydroxide, magnesium hydroxide, dolomitic hydrate, ammonium polyphosphate, melamine polyphosphate, piperazine polyphosphate, expandable graphite, and mixtures thereof. In the present invention, the flame retardant additive may be dispersed in a silicone polymer binder (i.e., polymer matrix) or distributed throughout the silicone polymer binder in a filling amount ranging from 1 to 70% by mass of the dry material. Flame retardant additives with a filling amount exceeding 70% by mass may result in insufficient mechanical performance required in battery fire protection applications.

[0047] Ingredient (E) In the present invention, component (E) is introduced into a silicone matrix under conditions of mixing, or preferably mixing and shearing, mixing and stirring, or a combination of mixing, shearing, and stirring, to give a water-in-oil emulsion, wherein the droplets have an average droplet size of 100 μm or less, 80 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, or 5 μm or less. Preferably, the average droplet size is 100 nm, 300 nm, 500 nm, 800 nm, or 1 μm or more.

[0048] According to the present invention, mixing, shearing, and / or stirring may be carried out by any conventional means or simple mixing for forming mortar. For example, component (E) may be mixed by hand or using a low-shear mixer, such as a cement mixer or static mixer, or a medium or high-shear mixer, such as a homogenizer, or other conventional foam mixing device.

[0049] Unlike the prior art in which water is used as a chemical foaming agent in relatively small amounts, for example, 0.1% to 5% by weight based on the total amount of the curable silicone composition, component (E) in the present invention is present in a much larger amount based on the total amount of the silicone matrix. In some embodiments of the present invention, the amount of component (E) is 5 to 1000 parts by weight, 10 to 800 parts by weight, 10 to 500 parts by weight, 10 to 300 parts by weight, 10 to 150 parts by weight, 20 to 130 parts by weight, 30 to 110 parts by weight, 40 to 100 parts by weight, 50 to 90 parts by weight, or 60 to 70 parts by weight, based on 100 parts by weight of component (A).

[0050] Ingredients (F) To facilitate the dispersion of water droplets at a relatively small average cell size and to apply a much larger amount of component (E) into the polysiloxane composite material, thereby maintaining the viscosity and homogeneity of the water-in-oil emulsion, one or more thickeners may be included. The thickeners are components that thicken the water of the present invention to improve viscosity, homogeneity, workability, and storage stability. The thickeners according to the present invention comprise one or more types selected from water-soluble organic polymers, clay minerals, or mixtures thereof.

[0051] Examples of water-soluble organic polymers include high molecular weight polysaccharides and water-soluble acrylic resins. Specifically, the use of water-soluble organic polymers containing carboxylate groups is preferred, and preferred examples include polyacrylates, which are carboxyl-containing adhesive polymers such as sodium polyacrylate and polysodium methacrylate.

[0052] The clay mineral may be natural or synthetic, and examples include natural or synthetic smectite clays such as bentonite, montmorillonite, hectorite, saponite, souconite, bydelite, and nontronite, with magnesium aluminum silicate being an example. Smectite clays such as bentonite and montmorillonite are preferred. Such smectite clays are available, for example, as SUMECTON SA (manufactured by Kunimine Industries Co., Ltd.), a hydrothermally synthesized product, and BEN-GEL (manufactured by Hojun., Co., Ltd.), a naturally refined product. These clay minerals may also be synthetic smectite clays, and it should be noted that synthetic smectite clays generally have smaller particle sizes than natural smectite clays. For example, the average particle size is only 5 or 10% of the average particle size of natural smectite. Because synthetic smectite clay has such a small particle size, it can be added in smaller amounts than natural smectite clay to produce a highly viscous aqueous gel composition. The pH of these clay minerals, such as smectite clay, is preferably in the pH range of 5.0 to 9.0.

[0053] Water-soluble organic polymers are components that can be modified by mixing with clay minerals to form hydrophilic composite materials with the clay minerals. In the present invention, only one type selected from water-soluble organic polymers or clay minerals may be used, but both may and preferably be used in a mixture.

[0054] Clay minerals such as bentonite or montmorillonite may be modified by pre-mixing with a water-soluble organic polymer. For example, the clay mineral and the water-soluble organic polymer may be uniformly mixed in water, and the mixture may then be dried, for example, by spray drying. The resulting dry mixture may be pulverized to a desired particle size, which may be in the range of 1 to 20 μm, if necessary. The amount of water-soluble polymer in such a mixture may be in the range of, for example, 0.1% to 40% by weight.

[0055] Examples of thickeners of the present invention include, but are not limited to, nanoclay, cellulose, polyacrylate, hydrophobically modified anionic thickeners, hydrophobically modified alkali swellable emulsions (HASE), and hydrophobically modified acrylic acid copolymers such as ACRYSOL® TT935 (Dow). The hydrophobically modified acrylic acid copolymer contains two or more hydrophobic groups, such as aryl or phenyl groups, or C4 or higher alkyl groups.

[0056] The total amount of one or more thickeners may be in the range of 0.2 to 5 parts by weight, 0.5 to 5 parts by weight, 1 to 4 parts by weight, or 2 to 3 parts by weight, based on 100 parts by weight of component (E). If the amount of thickener exceeds the above upper limit, the viscosity of the thickening water (M) may become excessively high, potentially reducing workability.

[0057] In some embodiments of the present invention, a thickening agent is first added to component (E) to produce thickened water (M). The thickening performance of the thickening agent is not particularly limited, but from the viewpoint of the technical effects of the present invention, the thickened water (M) is such that at 25°C and 0.1s -1 Viscosities in the ranges of 5,000-1,000,000 cst, 20,000-800,000 cst, 50,000-500,000 cst, 100,000-300,000 cst, or 150,000-250,000 cst, and 25°C and 10s -1 Preferably, a viscosity-enhancing characteristic having a viscosity in the range of 1,000 to 10,000 cst, 3,000 to 9,000 cst, 5,000 to 8,000 cst, or 6,000 to 7,000 cst is provided.

[0058] Ingredients (G) In the present invention, the curable silicone-based composition can be in the form of a water-in-oil emulsion. For good dispersibility, the curable silicone-based composition can further contain at least one component (G), namely, an emulsifier. In a preferred embodiment, the emulsifier is a nonionic emulsifier. In a more preferred embodiment, the emulsifier can be selected from the group consisting of polysiloxane polyethers, alkyl-poly(ethylene oxide), polyoxyethylene-polyoxypropylene copolymers, and mixtures thereof.

[0059] For example, the polyoxyethylene-polyoxypropylene copolymer nonionic emulsifier is usually a compound represented by the following general formula (1) or general formula (2). HO(CH2CH2O) a (CH(CH3)CH2O) b (CH2CH2O) c H (1) HO(CH(CH3)CH2O) d (CH2CH2O) e (CH(CH3)CH2O) f H (2)

[0060] In general formulas (1) and (2), a, b, c, d, e, and f are the average molar numbers of ethylene oxide or propylene oxide added, and are each independently a number from 1 to 350. The weight average molecular weight of the polyoxyethylene-polyoxypropylene copolymer is preferably 1,000 to 18,000, more preferably 1,500 to 10,000. Component (G) can be used in an aqueous solution when in solid form.

[0061] More specific examples of compounds that function as component (G) include the Pluronic® L series, Pluronic® P series, Pluronic® F series, and Pluronic® TR series from ADEKA CORPORATION, Emulgen PP-290 from Kao Corporation, and Newcol 3240 from Nippon Nyukazai Co., Ltd., all of which are commercially available.

[0062] In some embodiments of the present invention, emulsifier (G) does not contain an ionic emulsifier. Generally, anionic surfactants, cationic surfactants, and / or amphoteric surfactants can be used as ionic emulsifiers. Therefore, in the present invention, the curable silicone composition may be substantially free of any surfactant. Examples of anionic surfactants include alkylbenzene sulfonates, alkyl ether sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, alkyl naphthyl sulfonates, unsaturated aliphatic sulfonates, and aliphatic hydroxylated sulfonates. Examples of cationic surfactants include quaternary ammonium type salt surfactants, such as octadecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and other alkyltrimethylammonium salts; dioctadecyldimethylammonium chloride, dihexadecyldimethylammonium chloride, didecyldimethylammonium chloride, and other dialkyldimethylammonium salts. Examples of amphoteric surfactants include alkyl betaines and alkylimidazolines.

[0063] In the present invention, the emulsifier may be initially added to the silicone oil composite mixture (N). In some embodiments of the present invention, the amount of component (G) may be in the range of 0.2 to 5 parts by weight, 0.5 to 5 parts by weight, 1 to 4 parts by weight, or 2 to 3 parts by weight, based on 100 parts by weight of component (A). If the amount of emulsifier exceeds the above upper limit, the mechanical strength of the final polysiloxane composite material will decrease.

[0064] Ingredients (H) In the present invention, the hydrosilylation catalyst inhibitor is an optional component that can slow down the reaction rate by inhibiting the hydrosilylation catalyst as needed, thereby allowing the mixing to be completed before the mixture begins the curing reaction. Therefore, it should be understood that if rapid curing cannot occur during or immediately after mixing, it may be necessary to add component (H), but if immediate curing can occur immediately after mixing, it may not be necessary to add component (H). The determination of whether or not it is necessary to add component (H) to the polysiloxane composite material is within the capabilities of those skilled in the art.

[0065] Examples of hydrosilylation catalyst inhibitors include methylvinylcyclosiloxane, tetravinyltetramethyl-cyclotetrasiloxane (vinyl D4), ethinylcyclohexanol (ECH), and mixtures thereof. Particularly preferably, the hydrosilylation catalyst inhibitor may be incorporated into the curable silicone composition in an amount of 0% to 2% by weight, 0.05% to 1.5% by weight, or 0.5% to 1.2% by weight, for example, 0.1% by weight, based on the total amount of the curable silicone composition, and this depends on the desired curing rate.

[0066] In some embodiments of the present invention, the amount of component (H) is 0.05 to 2 parts by weight, 0.1 to 1.5 parts by weight, 0.5 to 1.0 parts by weight, or 0.7 to 0.9 parts by weight, based on 100 parts by weight of component (A).

[0067] Component (I) In the present invention, component (I) is one or more opacifying agents capable of absorbing, scattering, and reflecting thermal radiation. The particle sizes of these opacifying agents may be in the range of 0.2 to 50 μm, 0.5 to 20 μm, 1 to 10 μm, or 2 to 5 μm. Examples of opacifying agents include titanium dioxide, zirconium oxide, ilmenite, iron titanate, iron oxide, zirconium silicate, silicon carbide, manganese oxide, and carbon black, or any combination thereof. In one embodiment, carbon black or Fe3O4 may be used as the opacifying agent. Component (I) is typically present in an amount of 0.2 to 20% by weight, or 1 to 15% by weight, or 2 to 12% by weight, based on the total amount of the curable silicone composition. Component (I) is commercially available.

[0068] Process for manufacturing battery packs In the present invention, a battery pack can be manufactured by curing, for example, emulsion curing, a curable silicone-based composition that partially or completely fills the gap between two adjacent cells. The cured polysiloxane composite material has cells having an average cell size of 100 μm or less. The components of the curable silicone-based composition before curing are as described above.

[0069] In the present invention, the process for manufacturing a battery pack consists of the following steps: Step (I): To provide a mixture containing components (A), (B), (C), and (D), Step (II): Applying component (E) to a mixture under mixing and shearing conditions to provide a water-in-oil emulsion containing water droplets having an average droplet size of 100 μm or less, Step (III): Heating the water-in-oil emulsion to cure the polysiloxane matrix and form a cured wet composite material, Step (IV) includes assembling the cured composite material between the cells in the battery pack.

[0070] In some embodiments, component (F), i.e., a thickener, may be optionally added to component (E) before applying component (E), which allows for sufficient shearing and time to achieve a sufficient thickening effect. In step (II), the thickened component (E) may be applied to the mixture obtained in step (I).

[0071] In step (I), component (A) is mixed with the other components except components (E) and (F) to obtain a silicone-based mixture (N). Then, component (E) or thickened component (E) (i.e., thickened water (M)) can be added to mixture (N). By applying sufficient shear and time, water droplets can be dispersed in the silicone-based mixture, with an average droplet size of 100 μm or less, 80 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, or 5 μm or less. Preferably, the average droplet size is 100 nm, 300 nm, 500 nm, 800 nm, or 1 μm or more. Optionally, any other component may be added to the mixture at this point under mixing conditions. By introducing water, the silicone-based mixture forms a water-in-oil emulsion.

[0072] The water-in-oil emulsion may be heated at a temperature in the range of 60°C to 200°C for a period of time, for example, 5 minutes to 24 hours. In this invention, the temperature and time are not particularly limited, as long as they are sufficient to cure the water-in-oil emulsion through the reaction between the alkylene groups and the Si-H groups. By curing, the water-in-oil emulsion forms a cured wet composite material having water droplets dispersed inside. During curing, any technique to avoid significant water evaporation, such as a high-pressure and / or sealed reactor, may be used.

[0073] When curing is complete, water can be partially or completely removed from the cured wet composite by raising the operating temperature to a level higher than the boiling point of water, allowing sufficient time for partial or complete removal of water from the cured wet emulsion. Partially or completely dried polysiloxane composites with an average cell size of 100 μm or less can be obtained.

[0074] In the present invention, the battery pack or polysiloxane composite material is prepared solely by component (E) without intentionally adding or using physical or chemical foaming agents.

[0075] Furthermore, since the dried polysiloxane composite material of the present invention is manufactured by an emulsification, curing, and drying process rather than a chemical foaming process, its manufacturing process has the advantages of being odorless, operator-friendly, and safe to operate as it does not generate hydrogen gas. [Examples]

[0076] The following is a more detailed description of the present invention with reference to examples. However, the present invention is not limited to these examples. All parts and percentages are by weight unless otherwise indicated.

[0077] [Tensile strength] The tensile strength of the polysiloxane composite material was measured according to CTM 0137A.

[0078] [density] The density of the polysiloxane composite material was measured according to ASTM D792.

[0079] [Thermal insulation test] Figure 1 shows the experimental setup for the thermal insulation performance test. A 10cm × 10cm × 0.35cm sample was placed on a heater at 600°C. Two thermocouples were placed on the back of the sample to monitor the temperature. An aluminum plate was placed on top of the sample to simulate adjacent battery cells in a battery module. Several loads were applied to the aluminum plate to simulate the pressure during a thermal runaway process.

[0080] [Average cell size] A deep learning-based segmentation method was employed to segment SEM images of silicone foam or composite materials. Figures 2-9 show SEM images of CE1-2 and IE1-6 according to the present invention. This technique can accurately segment pores from a diverse range of image formats without requiring model retraining or parameter adjustment. The neural network used in this process is based on the U-Net architecture, and the model is trained on a dataset of over 70,000 segmented objects from a wide variety of microscopic images. The resulting model can generate masks featuring multiple labeled image regions. The scikit-image toolkit is used to analyze the masks and generate characteristics of the labeled image regions. The toolbox is built using Python 3.8 and depends on dependencies such as pytorch, numpy, scipy, and scikit-image. Further details can be found on the website titled "U-Net: Convolutional Networks for Biomedical Image Segmentation" at "https: / / arxiv.org / abs / 1505.04597v1".

[0081] The raw materials used in the examples are listed in Table 1 below.

[0082] [Table 1]

[0083] Examples 1-6 (Inventive Examples, IE1-6) and Comparative Examples 1-2 (Comparative Examples, CE1-2) In Examples 1 to 6 of this disclosure, polysiloxane composite materials were produced using the raw materials and their quantities listed in Table 2. Comparative Examples 1 and 2 are provided as controls.

[0084] Table 2: Formulations used in the examples and comparative examples [Table 2]

[0085] [Table 3]

[0086] [Table 4]

[0087] Preparation of silicone-based compositions / formulations: Part A: All components listed in Part A of Table 2 were mixed in a SpeedMixer at 1500 rpm for 2 minutes under vacuum.

[0088] Part B: All components listed in Part B of Table 2 were mixed under vacuum in a SpeedMixer at 1500 rpm for 2 minutes.

[0089] Part C: All components listed in Part C of Table 2 were mixed using a stirrer at 1500 rpm for 10 minutes.

[0090] Manufacturing of polysiloxane composite materials: 1. In CE1 using H2 foam Parts A and B were mixed using a Speedmixer at 1500 rpm for 30 seconds. The mixture was then molded into a sheet of the desired thickness between two PET films. The sheet was cured and foamed in a 70°C oven for 10 minutes, the foamed silicone sheet was peeled from the PET film, and post-cured in a 170°C oven for 30 minutes. After post-curing, the properties and performance of the silicone foam sheet were measured.

[0091] 2. In CE2 and IE1-6 using water-in-oil emulsions Parts A and B were mixed using a Speedmixer at 1500 rpm for 30 seconds. Part C was mixed into the mixture by hand, and then rapidly mixed under vacuum at 1500 rpm for 30 seconds. The mixture was then molded into a sheet of the desired thickness between two PET films. The sheet was cured in an 80°C oven for 10 minutes. The cured silicone sheet was peeled from the PET film and placed in a 180°C oven for 60 minutes to remove water. After water removal, the properties and performance of the silicone composite material were measured.

[0092] [Table 5]

[0093] As shown in Table 3, CE1 was a conventional H2 foamed silicone foam with an average cell size of 300 μm. It exhibited higher thermal conductivity and worse thermal insulation performance when measured at 600°C. IE1-6 all showed very small average cell sizes. CE2 was a microcellular silicone composite material without flame-retardant fillers, which exhibited insufficient thermal insulation performance.

[0094] In IE1-6, they all exhibited lower thermal conductivity and better thermal insulation performance. On the other hand, due to their microcell structure, their tensile strength and elongation are far better than those of CE1.

Claims

1. A battery pack comprising a polysiloxane composite material, wherein the polysiloxane composite material partially or completely fills the gap between two adjacent battery cells, and having an average cell size of 100 μm or less.

2. The battery pack according to claim 1, wherein the polysiloxane composite material has a closed-cell ratio of 50% or more.

3. The aforementioned polysiloxane composite material (A) At least one organopolysiloxane having at least two alkenyl groups bonded to silicon per molecule, (B) At least one organopolysiloxane having at least two hydrogen atoms bonded to silicon per molecule, (C) Hydrosilylation catalyst and (D) at least one flame-retardant filler, (E) The battery pack according to claim 1, obtained by curing a curable silicone composition containing water.

4. The battery pack according to claim 3, wherein, based on 100 parts by weight of component (A), component (B) is in an amount of 0.5 to 20 parts by weight, and / or component (D) is in an amount of 2 to 250 parts by weight.

5. The battery pack according to claim 3, wherein component (E) is in an amount of 5 to 1000 parts by weight based on 100 parts by weight of component (A).

6. The curable silicone composition is F) The battery pack according to claim 3, further comprising 0.2 to 5 parts by weight of at least one thickener based on 100 parts by weight of component (E).

7. The battery pack according to claim 6, wherein component (F) is selected from the group consisting of nanoclay, cellulose, polyacrylate, and mixtures thereof.

8. A process for manufacturing a battery pack according to any one of claims 1 to 7, Step (I): To provide a mixture containing components (A), (B), (C), and (D), Step (II): Applying component (E) to a mixture under mixing and shearing conditions to provide a water-in-oil emulsion containing water droplets having an average droplet size of 100 μm or less, Step (III): Heat the water-in-oil emulsion to cure the polysiloxane matrix and form a cured wet composite material. Step (IV): A process comprising assembling the cured wet composite material between cells in a battery pack.

9. The method is A process for manufacturing a battery pack according to claim 8, further comprising: step (I'): applying component (F) to component (E) under mixing and shearing conditions prior to step (II) to provide a thickened component (E).

10. The method is A process for manufacturing the battery pack according to claim 8, further comprising step (V): partially or completely removing water from the wet polysiloxane composite material formed in step (III).

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