USE OF A FLAME-RETARDANT COMPOSITION FOR ENERGY STORAGE DEVICES AND BATTERIES CONTAINING THE SAME

Abstract

Use of a flame-retardant composition in a battery module, wherein the flame-retardant composition for a battery module comprises: a first composition comprising porous particles on which a first metal catalyst particle and a first flame-retardant particle are disposed, and a second composition comprising a fibrous composition comprising a fibrous substrate having disposed thereon a second metal catalyst particle and a second flame-retardant particle, wherein the first composition and the second composition are disposed on a plurality of battery cells in the battery module.

Description

[0001] This disclosure relates to the use of flame-retardant compositions for energy storage devices and to battery modules and battery packs containing the flame-retardant compositions.

[0002] A battery, which comprises a plurality of assembled battery cells (e.g., secondary batteries), is used in various applications, such as portable electronic devices, electric bicycles, hybrid vehicles, electric cars, and the like. Because secondary battery cells store electrical energy in high density, they often generate abnormally high amounts of heat and gases, which can lead to an undesirable thermal event. This phenomenon often occurs when batteries are accidentally short-circuited or damaged.

[0003] If one of the battery cells in the assembled battery module experiences an adverse thermal event, it may also trigger a corresponding adverse event in a neighboring secondary battery cell. It is desirable to prevent such adverse events from occurring consecutively. BACKGROUND

[0004] It is also desirable to provide flame-retardant materials used in energy storage devices such as batteries, capacitors, supercapacitors, etc., which can increase the flame retardancy of the energy storage device. SUMMARY

[0005] A flame-retardant composition for a battery module used according to the invention comprises a first composition and a second composition disposed on a plurality of battery cells in the battery module. The first composition comprises porous particles on which a first metal catalyst particle and a first flame-retardant particle are disposed. The second composition comprises a fibrous composition on which a second metal catalyst particle and a second flame-retardant particle are disposed.

[0006] In one aspect, the first and second compositions are intimately mixed and applied to the battery module in a single layer.

[0007] In another aspect, the first composition is disposed in a first layer and the second composition is disposed in a second layer, wherein the second layer is farther from the secondary battery cells than the first layer.

[0008] In another aspect, a first layer comprising the first composition is disposed between two second layers each comprising the second composition.

[0009] In another aspect, a second layer comprising the second composition is disposed between two first layers comprising the first composition.

[0010] In another aspect, the first metal catalyst particle has the same chemical composition as the second metal catalyst particle.

[0011] In another aspect, the first metal catalyst particle has a different chemical composition than the second metal catalyst particle.

[0012] In another aspect, the first flame-retardant particle has the same chemical composition as the second flame-retardant particle.

[0013] In another aspect, the first metal catalyst particle and the second catalyst metal particle each comprise a transition metal.

[0014] In yet another aspect, the first metal catalyst particle and the second catalyst metal particle are each selected from the group consisting of iron, nickel, cobalt, platinum, palladium, rhodium, tungsten, titanium, niobium, hafnium, vanadium, molybdenum, manganese, or a combination thereof.

[0015] In yet another aspect, the first flame-retardant particle and the second flame-retardant particle are each selected from the group consisting of metal hydroxides, metal halides, phosphorus-containing flame retardants, nitrogen-containing flame retardants, and a combination thereof.

[0016] In yet another aspect, the phosphorus-containing flame retardant is an organic phosphate ester and the nitrogen-containing flame retardant is a melamine.

[0017] In yet another aspect, the porous particles are selected from the group consisting of zeolites, aerogels, metal-organic frameworks, fumed metal oxides, or a combination thereof.

[0018] A battery module comprises a plurality of secondary battery cells arranged side by side and a flame-retardant composition disposed on the plurality of secondary battery cells, the flame-retardant composition comprising a first composition and a second composition. The first composition comprises porous particles having a first metal catalyst particle and a first flame-retardant particle disposed thereon. The second composition comprises a fibrous composition comprising a fibrous substrate having a second metal catalyst particle and a second flame-retardant particle disposed thereon.

[0019] In one aspect, the first metal catalyst particle has the same chemical composition as the second metal catalyst particle.

[0020] In another aspect, the first metal catalyst particle has a different chemical composition than the second metal catalyst particle.

[0021] In yet another aspect, the first flame-retardant particle has the same chemical composition as the second flame-retardant particle.

[0022] In yet another aspect, the first metal catalyst particle and the second catalyst metal particle comprise a transition metal particle.

[0023] In yet another aspect, the metal catalyst particles, the flame retardant particles, and the porous particles are mixed with a polymeric binder to produce a slurry that fills all of the free space in the module.

[0024] The foregoing features and advantages, as well as other features and advantages of the disclosure, will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further features, advantages and details are listed only as examples in the following detailed description, which refers to the drawings in which: Fig. 1 shows an exemplary schematic representation of a battery module comprising a plurality of secondary battery cells in a cross-sectional view and Fig. 2 shows an exemplary schematic representation of the battery module in which the flame-retardant composition is arranged on the secondary battery cells. DETAILED DESCRIPTION

[0026] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or uses.

[0027] Disclosed herein is a flame-retardant composition used in accordance with the invention disposed within a battery module to increase the overall flame retardancy of the module and minimize adverse thermal events, such as thermal runaway. The flame-retardant composition is disposed within the battery module and bears upon a plurality of battery cells contained within the battery module. In one embodiment, the flame-retardant composition is disposed within the battery module and bears upon a plurality of vertically aligned battery cells contained within the battery module.

[0028] The flame-retardant composition comprises a fibrous substrate in which a slurry comprising porous media, metal catalyst particles, and flame-retardant particles is disposed. The slurry may optionally contain a polymeric binder. The slurry may be poured into the module to fill the open spaces within the module. In another embodiment, the flame-retardant composition comprises a fibrous substrate infiltrated with a slurry comprising porous media, metal catalyst particles, and flame-retardant particles. In one embodiment, the flame-retardant composition may be applied to the battery module in a single layer sitting on top of the plurality of vertically aligned battery cells.

[0029] In another embodiment, the flame-retardant composition can be used in the battery module in two or more layers—a first layer comprising a first composition containing a particulate flame-retardant composition, and a second layer comprising a second composition containing a fibrous flame-retardant composition. The first composition of the first layer is a particulate composition comprising porous media, a first metal catalyst particle, and a first flame-retardant particle, while the second composition of the second layer is a fibrous composition comprising a fibrous substrate, a second metal catalyst particle, and a second flame-retardant particle.The first metal catalyst particle may be identical to or different from the second metal catalyst particle, while the first flame-retardant particle may be identical to or different from the second flame-retardant particle. In a preferred embodiment, the first metal catalyst particle is the same as the second metal catalyst particle, and the first flame-retardant particle is the same as the second flame-retardant particle. The first and second layers may be placed in the battery module in various configurations discussed herein.

[0030] In yet another embodiment, the first and second compositions may be blended into an intimate mixture and applied to the battery module as a single layer, as described in detail herein.

[0031] Fig. 1 shows an exemplary schematic representation of a battery module 100, which comprises a plurality of modules 150, 250, etc. arranged parallel to one another, in a cross-sectional view. Each module comprises a plurality of battery cells. A first module 150 comprises, for example, the battery cells 102, 104, 106, etc., while the second module 250 comprises the battery cells 102', 104', 106', etc. The first module 150 is separated from the second module 250 by a barrier 200. The plurality of battery cells 102, 104, 106, etc. are enclosed by a protective sheath 108. On the battery cells 102, 104, 106, etc., there is a space 210 into which a flame-retardant composition can be introduced as a single layer or in multiple layers.

[0032] The flame retardant composition used in a single layer

[0033] As mentioned above, the flame-retardant composition (when used in a single layer) comprises a fiber substrate infiltrated with a slurry comprising a solvent, the porous media, metal catalyst particles, and flame-retardant particles.

[0034] The fibrous substrate comprises a fibrous composition that is inherently non-flammable. The fibers in the fibrous composition preferably have an aspect ratio greater than 1, preferably greater than 5, and more preferably greater than 10. As used herein, the term "fibrous" encompasses fibers that may be in the form of whiskers, needles, rods, tubes, strands, elongated platelets, lamellar platelets, ellipsoids, microfibers, nanofibers and nanotubes, elongated fullerenes, and the like. If such fillers are in aggregate form, an aggregate with an aspect ratio greater than 1 is also sufficient.

[0035] Non-limiting examples of suitable fibrous fillers include short inorganic fibers, including processed mineral fibers such as those derived from mixtures comprising at least one of the following: aluminum silicates, aluminum oxides, magnesium oxides, and calcium sulfate hemihydrate; boron fibers; ceramic fibers such as silicon carbide; and fibers made from mixed oxides of aluminum, boron, and silicon sold under the trade name NEXTEL® by 3M Co., St. Paul, MN, USA. The fibrous substrate also includes single crystal fibers or "whiskers" such as silicon carbide, aluminum oxide, boron carbide, iron, nickel, and copper. Fiber substrates such as glass fibers, basalt fibers, including textile glass fibers, and quartz may also be included.

[0036] Such reinforcing fillers may be provided in the form of monofilament or multifilament fibers and may be used either alone or in combination with other fiber types, e.g., by co-weaving or core / sheath, side-by-side, pie-slice, or matrix and fibril construction, or by other methods known to one skilled in the art of fiber manufacturing. Typical cowoven structures are glass fiber / carbon fiber, carbon fiber / aromatic polyimide fiber (aramid fiber), and aromatic polyimide fiber / glass fiber. Fiber substrates comprising glass may be supplied, e.g., in the form of rovings, woven fiber reinforcements such as 0-90 degree wovens, nonwoven fiber reinforcements such as continuous fiber mats, chopped strand mats, fabrics, papers, and felts, as well as three-dimensional woven reinforcements, preforms, and braids.

[0037] In a preferred embodiment, glass fibers are used as the fiber substrate. Useful glass fibers can be formed from any type of glass composition suitable for fiberglass formation and include those made from glass compositions suitable for fiberglass formation commonly known as "E-glass," "A-glass," "C-glass," "D-glass," "R-glass," and "S-glass," as well as E-glass derivatives that are fluorine-free and / or boron-free. Most reinforcing mats are made from glass fibers made from E-glass.

[0038] Commercially produced glass fibers, which generally have a nominal filament diameter of about 4.0 to about 35.0 micrometers, and the most commonly produced E-glass fibers, which have a nominal filament diameter of about 9.0 to about 30.0 micrometers, can be used in the fiber substrate.

[0039] The fibrous filaments of the fiber substrate are produced by standard processes (e.g., steam or air blowing, flame blowing, and mechanical drawing). The preferred filaments for the fiber substrate can be produced by mechanical drawing. The glass fibers can be sized or unsized. Sized glass fibers are coated on at least a portion of their surface with a sizing composition that allows for the elution and wetting of the matrix material disposed on the fiber strands and helps achieve the desired physical properties of the composite.

[0040] The glass fibers are preferably sized glass strands. In manufacturing the glass fibers, a number of filaments may be formed simultaneously, sized with the coating agent, and then bundled into a strand. Alternatively, the strand itself may first be formed from filaments and then sized. The amount of size used is generally that amount sufficient to bond the glass fibers into a continuous strand and ranges from about 0.1 to about 5% by weight, typically from about 0.1 to 2% by weight, based on the weight of the glass fibers. Generally, this may be about 1.0% by weight, based on the weight of the glass filament. Glass fibers in the form of short fiber strands having a length of about one-quarter inch or less, and preferably about one-eighth of an inch, may also be used. They may also be longer than one-quarter inch if desired.

[0041] In a preferred embodiment, the fibrous composition comprises glass fibers in the form of fiberglass. Generally, the glass fibers are present in the flame-retardant composition in an amount of up to about 50% by weight, based on the total weight of the composition, and preferably from about 1 to about 20% by weight, based on the total weight of the flame-retardant composition.

[0042] Carbon fibers can also be used as a fiber substrate in the flame-retardant composition. Carbon fibers have several advantages, including high stiffness, high tensile strength, low weight-to-strength ratio, high chemical resistance, high temperature tolerance, and low thermal expansion. Precursors for carbon fibers include polyacrylonitrile (PAN), rayon, and pitch. These precursors are first woven into a fiber filament yarn, which is then drawn under tension at temperatures above 1000°C, preferably at temperatures above 1500°C, to form the carbon fibers.

[0043] The carbon fibers can also be treated with a sizing agent as described above. Fiber substrates comprising carbon fibers can also be supplied, for example, in the form of rovings, woven fiber reinforcements such as 0-90° woven fabrics, nonwoven fiber reinforcements such as continuous fiber mats, short fiber mats, fabrics, papers, and felts, as well as three-dimensional woven reinforcements, preforms, and braids.

[0044] The glass fibers are present in the flame-retardant composition in an amount of up to about 50% by weight based on the total weight of the composition, and preferably from about 1 to about 20% by weight based on the total weight of the flame-retardant composition. Porous media

[0045] The flame-retardant composition comprises a porous medium (hereinafter referred to as porous particles), which can be added to the composition alone or, alternatively, added to the composition with a first flame retardant and a first metal catalyst (hereinafter referred to as first metal catalyst particles) disposed on the porous medium. The porous particles can react with a substantial portion of the gases, such as hydrogen and hydrocarbon gases, initially generated in the battery during an adverse thermal event to terminate the branching reaction of the combustion chain and suppress the propagation of the adverse thermal event.

[0046] Furthermore, the high specific surface area of the porous particles can adsorb the combustible gases. In one embodiment, the first metal catalyst particles can convert the gases released during thermal runaway to produce carbonaceous particles, thereby solidifying the hydrocarbon gases. The porous medium (e.g., zeolite) also catalyzes the formation of carbon black. The carbon black intumesces due to a synergistic reaction between the zeolite, the polymer components, such as the binders used, and the flame-retardant chemicals, such as ammonium phosphates. Intumescence increases flame retardancy.

[0047] Intumescence is the process of expansion or swelling that dissipates some of the heat generated during an adverse thermal event, thereby mitigating the propagation of the adverse event. The particle structure of the porous medium allows it to fill spaces and crevices within the module, establishing close contact with the battery cells. This close contact can facilitate rapid decay of an adverse thermal event within the module. Suitable examples of porous particles include zeolites, aerogels, fumed metal oxides, metal-organic frameworks (MOFs), or the like, or a combination thereof. Zeolites

[0048] Zeolites are a form of molecular sieve, which are microporous crystalline solids with well-defined structures that comprise silicon, aluminum, and oxygen in their framework and may also contain cations in their pores. The zeolites (like all porous media described herein) can be added to the flame-retardant composition individually (without the metal catalyst particles or flame-retardant particles) or with a portion of the metal catalyst particles and a portion of the flame-retardant particles (from the flame-retardant composition) disposed thereon.

[0049] Zeolites have a crystalline framework of interconnected alumina and silica, particularly cross-linked alumina and silica through the sharing of oxygen atoms, and can thus be characterized by the silica-to-alumina ratio (SAR ratio). The higher the SAR ratio of a zeolite, the more stable the zeolite is to hydrothermal influences. A characteristic feature of a molecular sieve is its crystalline or pseudocrystalline structure, formed by molecular tetrahedral cells that are interconnected in a regular and / or repeating manner to form a framework.

[0050] Zeolites exhibit a three-dimensional molecular framework resulting from the alignment of their interconnected cells. The cells of these molecular sieves typically have a volume on the order of a few cubic nanometers and cell openings (also called "pores" or "apertures") on the order of a few angstroms in diameter. The cells are defined by the ring size of their pores; for example, the term "8-ring" refers to a closed loop composed of eight tetrahedrally coordinated silicon (or aluminum) atoms and eight oxygen atoms.In certain zeolites, the cell pores within the framework are oriented to create one or more channels extending through the framework, creating a mechanism that limits the penetration or passage of various molecular or ionic species through the molecular sieve based on the relative size of the channels and the molecular or ionic species.

[0051] This property is useful because the zeolites (used as substrates) can be sized to allow certain flammable gases generated during a thermal event to enter their pores (and be deprived of oxygen), while excluding certain other gases (which may not be flammable) from entering the porous substrate. This property can minimize the sequential propagation of a thermal event from one battery cell to a neighboring cell, thus improving flame retardancy. The size and shape of zeolite pores thus influence catalytic activity by exerting a steric influence on the reactants and regulating the access of reactants and products.

[0052] Molecular sieves with a small-pore framework (i.e., with a maximum ring size of eight) have proven particularly useful for SCR applications. Small-pore molecular sieves include those exhibiting the following crystal structures: CHA, LEV, ERI, and AEI. Specific exemplary molecular sieves made from aluminosilicates and silico-aluminophosphates that exhibit the CHA framework include SAPO-34, AIPO-34, and SSZ-13. Aerogels

[0053] Aerogels can also be used as porous particles, which can be used individually (as defined above, without the metal catalyst particles or without the flame-retardant particles) or alternatively with some or all of the catalyst metal particles and the flame-retardant particles arranged thereon. Aerogels are synthetic, porous, ultralight materials derived from a wet gel, where the liquid component of the wet gel has been replaced by a gas, without significant collapse of the gel structure. The result is a solid with extremely low density and extremely low thermal conductivity. Aerogels are good thermal insulators because they nearly eliminate two of the three methods of heat transfer: conduction (they consist largely of insulating gas) and convection (the microstructure prevents net gas movement). They are good conductive insulators because they consist almost entirely of gases, which are very poor conductors of heat.They are good convection inhibitors because the air cannot circulate through the grille.

[0054] Inorganic and organic aerogels can also be used as porous particles. Inorganic aerogels include silica aerogels, alumina aerogels, nickel-alumina aerogels, holmium oxide aerogels, iron oxide aerogels, erbium oxide aerogels, chromium oxide aerogels, samarium oxide aerogels, vanadium oxide aerogels, neodymium oxide aerogels, or a combination thereof. The aerogels can be provided with surface treatments such as hexamethyldisilazane, trichloromethylsilane, and the like, which prevent moisture penetration into the porous particles.

[0055] Organic aerogel particles can include those derived from biopolymers as well as those derived from synthetic organic polymers.

[0056] Examples of biopolymers that can be used in the aerogels include cellulose, cellulose with reduced crystallinity, polysaccharides, chitosan, oligochitosan, gelatin, collagen, hydroxyalkylcelluloses such as hydroxypropylcellulose, hydroxymethylcellulose and hydroxyethylcellulose, sodium carboxymethylcellulose, cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose acetate butyrate and cellulose ethers such as ethylcellulose, sugars (glucose, sucrose, lactose, galactose, fructose, mannitol, sorbitol or a combination thereof), proteins, starch, pectin, alginate, starch sodium octenylsuccinate, locust bean gum, carrageenan, agar, xanthan gum, guar gum, casein, whey protein isolate, soy protein isolate, pea protein isolate, potato protein isolate, zein, lecithin, stearic acid, beeswax, Cotton wax, carnauba wax, milk fat, palm and palm kernel oil or the like or a combination thereof.

[0057] Synthetic polymers can also be used in aerogels. The synthetic polymers are organic polymers and can be selected from a wide variety of thermoplastic polymers, blends of thermoplastic polymers, thermosetting polymers, or blends of thermoplastic polymers with thermosetting polymers. The organic polymer can also be a blend of polymers, copolymers, terpolymers, or combinations comprising at least one of the aforementioned organic polymers.The organic polymer may also be an oligomer, a homopolymer, a copolymer, a block copolymer, an alternating block copolymer, a random polymer, a random copolymer, a random block copolymer, a graft copolymer, a star block copolymer, a dendrimer, a polyelectrolyte (polymers having some repeating groups containing electrolytes), a polyampholyte (a polyelectrolyte having both cationic and anionic repeating groups), an ionomer, or the like, or a combination thereof. The organic polymers have a number-average molecular weight of greater than 10,000 grams per mole, preferably greater than 20,000 g / mol, and more preferably greater than 50,000 g / mol.

[0058] Examples of thermoplastic polymers that can be used in the polymer material include polyacetals, polyacrylics, polycarbonates, polyalkyds, polystyrenes, polyolefins, polyesters, polyamides, polyaramids, polyamideimides, polyarylates, polyurethanes, epoxies, phenols, silicones, polyarylsulfones, polyethersulfones, polyphenylene sulfides, polysulfones, polyimides, polyetherimides, polytetrafluoroethylenes, polyetherketones, polyetheretherketones, polyetherketoneketones, polybenzoxazoles, polyoxadiazoles, polybenzothiazinophenothiazines, polybenzothiazoles, polypyrazinoquinoxalines, polypyromellitimides, polyguinoxalines, polybenzimidazoles, polyoxindoles, polyoxoisoindolines, polydioxoisoindolines, polytriazines, polypyridazines, polypiperazines, polypyridines, polypiperidines, polytriazoles, Polypyrazoles, polycarboranes, polyoxabicyclononanes, polydibenzofurans, polyphthalides, polyacetals, polyanhydrides, polyvinyl ethers, polyvinyl thioethers, polyvinyl alcohols, polyvinyl ketones, polyvinyl halides,Polyvinylnitriles, polyvinyl esters, polysulfonates, polysulfides, polythioesters, polysulfones, polysulfonamides, polyureas, polyphosphazenes, polysilazanes, polypropylenes, polyethylenes, polyethylene terephthalates, polyvinylidene fluorides, polysiloxanes or the like or a combination thereof.

[0059] Examples of thermosetting polymers include epoxy polymers, unsaturated polyester polymers, polyimide polymers, bismaleimide polymers, bismaleimide triazine polymers, cyanate ester polymers, vinyl polymers, benzoxazine polymers, benzocyclobutene polymers, acrylics, alkyds, phenol-formaldehyde polymers, novolaks, resols, melamine-formaldehyde polymers, urea-formaldehyde polymers, hydroxymethylfurans, isocyanates, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, unsaturated polyesterimides, resorcinol-formaldehyde, phenol-formaldehyde, melamine-formaldehyde, cresol-formaldehyde, phenol-furfuryl alcohol, or the like, or a combination thereof. Biopolymer aerogels are preferred. Among the biopolymers, alginate-based aerogels are preferred.

[0060] The aerogels can be produced by supercritical extraction, freeze-drying or a combination thereof. Pyrogenic metal oxides

[0061] Fumed metal oxides, present in the form of porous agglomerates of nanoparticles, are effective as thermally conductive solid components and can be used as porous particles in the first composition of the flame-retardant composition. Examples of fumed metal oxides include fumed silica, fumed alumina, fumed zirconia, fumed titania, or a combination thereof.

[0062] The porous particle has a large surface area and a porosity of greater than 50 volume percent, preferably greater than 70 volume percent, and more preferably greater than 90 volume percent, based on the total volume of the porous substrate before impregnation with a transition metal precursor (see below) and the flame-retardant compound (see below).

[0063] The average pore size in the porous particle can be from 5 angstroms to 100 micrometers (µm), preferably from 100 nanometers (nm) to 50 micrometers, and more preferably from 150 nanometers to 20 micrometers. It is desirable for the porous substrate to contain a higher volume fraction of micrometer-sized pores than nanometer-sized pores. This prevents the porous substrate from collapsing due to pore collapse due to capillary pressure when exposed to liquids (e.g., moisture, battery acid, and the like).

[0064] The porous particle may have a unimodal, bimodal, or multimodal particle size distribution. Multimodal particle size distributions are preferred because they allow for better packing of the particles of the first composition. The porous particles may have an average particle size of 2 nanometers to 1000 micrometers, preferably from 10 nanometers to 100 micrometers, and more preferably from 50 to 10 micrometers. Metal-organic frameworks

[0065] Metal-organic frameworks (MOFs) are the fastest-growing class of materials in chemistry today. They consist of interchangeable metal-containing nodes and carbon-based struts. More than 15,000 MOFs are registered at the Cambridge Crystallographic Data Centre, providing a wide range of materials to choose from.

[0066] MOFs exhibit a specific surface area and micropore volume that can exceed those of conventional adsorbents such as zeolites and activated carbon. MOFs are hybrid inorganic-organic frameworks constructed by linking secondary building blocks (SBUs), typically consisting of metal ions or clusters, via rigid organic ligands. The variety of cations and molecular bridges that can be combined in the framework results in a broad range of materials with different pore sizes and functionalities.

[0067] The successful development of adsorbents requires a comprehensive understanding of the adsorbent structure, including pore size / shape, as well as the properties of the adsorbate. Adsorbates adhere to the surface through weak attractive interactions known as van der Waals forces. Adsorption occurs in pores whose diameter is approximately twice the molecular diameter of the adsorbed molecule, making the pore size distribution in the adsorbent a crucial factor. Existing MOFs can adsorb molecules with large micropores or even in the mesoporous range. According to the IU-PAC nomenclature, microporous is defined as pores with a diameter of less than 2 nm, and mesoporous as pores with a diameter between 2 and 50 nm. The pore size must be chosen so that the adsorbate molecules can be easily desorbed from the pore network and diffuse out.

[0068] Another material property that can affect the adsorption uptake of adsorbates is the presence of open metal sites and thus, to some extent, the chemistry / functionality of the MOFs.

[0069] In some MOFs, the metal centers are bound in a specific coordination environment, leaving the cation at the center open and accessible to the adsorbed gas molecules. Unsaturated metal sites have been shown to improve certain adsorbate affinities compared to non-open metals.

[0070] It should be noted that combinations of metal-organic frameworks, zeolites, aerogels, fumed metal oxides and the like can be used in combinations of two or more if desired.

[0071] The porous particles may be added to the flame-retardant composition in an amount of 1 to 20 wt%, preferably 2 to 15 wt%, based on the total weight of the flame-retardant composition. Metal catalyst particles

[0072] Metal catalyst particles are used in the flame-retardant composition and can be added separately to the flame-retardant composition (without placing them on the porous particles) or alternatively dispersed on the porous particles and then added to the flame-retardant composition.

[0073] If the flame-retardant composition is added to the battery module in two layers, the metal catalyst particles can be added in a first composition to the first layer and in a second composition to the second layer. The metal catalyst particles in the first composition can be identical to or "different" from those in the second composition. The term "different" implies a chemical difference: the chemistry of the metal particles in the first composition differs from the chemistry of the metal particles in the second composition.

[0074] The metal catalyst particles catalyze the carbon-containing gases generated in the battery module during thermal runaway. When the battery heats up to undesirably high temperatures, gases are generated. These gases are typically carbon-containing gases (i.e., they contain hydrocarbons, carbon dioxide, carbon monoxide, or combinations thereof) originating from the electrolytes used in the battery. These gases are flammable and toxic.

[0075] Metal particles can act as catalysts to convert these carbonaceous gases into carbonaceous solids such as carbon nanotubes, graphene, graphite particles, polyacetylene, or combinations thereof. In other words, they solidify the gases and reduce their undesirable effects. Furthermore, some of the formed solids can intumesce (sometimes referred to as exfoliation, particularly in the case of graphites), promoting flame retardancy and allowing the suppression or delay of adverse thermal events. It should be noted that some of these carbonaceous gases penetrate the pores of the porous particles, where they are sequestered, and their combustion is prevented due to the lack of oxygen.

[0076] Suitable metal particles include transition metal particles such as iron, nickel, cobalt, gold, silver, platinum, palladium, rhodium, aluminum, magnesium, lead, copper, tungsten, titanium, niobium, hafnium, vanadium, copper, molybdenum, manganese, or the like, or a combination thereof. Preferred metal particles include iron, nickel, cobalt, or a combination thereof.

[0077] The metal particles can be deposited on the fiber substrates or on the porous media by reducing salts such as chlorides, chlorates, sulfates, sulfides, nitrates, phosphates of the aforementioned metals, or the like. The metal salts are dissolved in suitable solvents, which are then mixed with the porous particles to form a slurry. The slurry is then dried, causing the metal salt to deposit on the porous particles. The porous particles with the metal salt deposited thereon are then exposed to a reducing gas stream (e.g., hydrogen, helium, or the like) at elevated temperatures to reduce the salt to a metal.

[0078] The metal catalyst particles have an average particle size of 2 nanometers to 50 micrometers, 10 nanometers to 25 micrometers, and 50 nanometers to 15 micrometers. The size of the metal particles depends on the concentration of salt relative to the porous particles in the slurry. A higher salt concentration relative to the porous particles results in larger metal catalyst particles after reduction.

[0079] The metal catalyst particles are generally present on the porous particles in an amount of from 0.5 to 10 wt.%, preferably from 1 to 5 wt.%, and more preferably from 1.5 to 4 wt.%, based on the total weight of the first composition. Flame-retardant particles

[0080] The flame-retardant particles are present in the flame-retardant composition (or alternatively, in the first composition and the second composition if the flame-retardant composition is added in two or more layers). The flame-retardant particles in the first composition may be identical to or "different" from those in the second composition. The term "different" implies a chemical difference: the chemistry of the flame-retardant particles in the first composition is different from the chemistry of the flame-retardant particles in the second composition.

[0081] Suitable flame retardant particles are, for example, metal hydroxides, halogenated flame retardants, phosphorus-containing flame retardants, nitrogen-containing flame retardants or the like or a combination thereof.

[0082] Metal hydroxides act as flame retardants by reacting (with themselves or with a metal oxide) in the presence of heat to form water. The water can extinguish the flame or, alternatively, surround the combustible material, preventing oxygen from coming into contact with the material and igniting it. In one embodiment, metal oxides can be used in conjunction with the metal hydroxides as flame retardants. Examples of metal hydroxides include magnesium hydroxide, aluminum hydroxide, or a combination thereof. Examples of metal oxides include magnesium oxide, aluminum oxide, or a combination thereof.

[0083] In some embodiments, the phosphorus-containing flame retardant comprises an organic phosphate ester. Exemplary flame retardants comprising organic phosphate esters are phosphate esters with phenyl groups, substituted phenyl groups, or a combination of phenyl groups and substituted phenyl groups, resorcinol-based bis-aryl phosphate esters, such as resorcinol bis(diphenyl phosphate), and bisphenol-based bis-aryl phosphate esters, such as bisphenol A bis(diphenyl phosphate). In some embodiments, the organic phosphate ester is selected from tris(alkylphenyl)phosphates (e.g., CAS No. 89492-23-9 or CAS No. 78-33-1), resorcinol bis(diphenyl phosphate) (CAS No. 57583-54-7), bisphenol A bis(diphenyl phosphate) (CAS No. 181028-79-5), triphenyl phosphate (CAS No. 115-86-6), tris(isopropylphenyl)phosphates (e.g., CAS No. 68937-41-7), t-butylphenyl diphenyl phosphates (CAS No. 56803-37-3), bis(t-butylphenyl)phenyl phosphates (CAS No.65652-41-7), tris(t-butylphenyl)phosphates (CAS No. 78-33-1) or the like or a combination thereof.

[0084] In some embodiments, the organic phosphate ester comprises a bis-aryl phosphate having the formula: where R, at each occurrence, is a C1-C 12 -alkylene group, R 5 and R 6 are each a C1-C5 alkyl group at each occurrence, R 1 , R 2 , and R 4 one C1-C each 12 -hydrocarbyl group, R 3 each time a C1-C occurs 12 -hydrocarbyl group, n is 1 to 25, and s1 and s2 are each an integer equal to 0, 1, or 2. In some embodiments, OR 1 , OR 2 , OR 3 and OR 4 each derived from phenol, a monoalkylphenol, a dialkylphenol or a trialkylphenol.

[0085] The bis-aryl phosphate is derived from a bisphenol, as one of ordinary skill in the art can readily determine. Examples of bisphenols include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxy-3-methylphenyl)propane, bis(4-hydroxyphenyl)methane, bis(4-hydroxy-3,5-dimethylphenyl)methane, and 1,1-bis(4-hydroxyphenyl)ethane. In some embodiments, the bisphenol comprises bisphenol A.

[0086] In some embodiments, the flame retardant comprises a metal dialkylphosphinate. As used herein, the term "metal dialkylphosphinate" refers to a salt comprising at least one metal cation and at least one dialkylphosphinate anion. In some embodiments, the metal dialkylphosphinate has the formula: where R a and R b are each C1-C6 alkyl, M is calcium, magnesium, aluminum or zinc and d is 2 or 3. Examples of R a and R binclude methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, and n-pentyl. In some embodiments, R a and R b Ethyl, M is aluminum and d is 3 (that is, the metal dialkylphosphinate is aluminum tris(diethylphosphinate)).

[0087] In some embodiments, the flame retardant comprises a nitrogen-containing flame retardant. Nitrogen-containing flame retardants include those comprising a nitrogen-containing heterocyclic base and a phosphate or pyrophosphate or a polyphosphate acid. In some embodiments, the nitrogen-containing flame retardant has the formula where g is 1 to 10,000 and the ratio of f to g is 0.5:1 to 1.7:1, particularly 0.7:1 to 1.3:1, more particularly 0.9:1 to 1.1:1. It is understood that this formula includes species in which one or more protons are transferred from the phosphate group(s) to the melamine group(s). When g is 1, the nitrogen-containing flame retardant is melamine phosphate (CAS No. 20208-95-1). If g is equal to 2, the nitrogen-containing flame retardant is melamine pyrophosphate (CAS No. 15541 60-3). If g is greater than 2 on average, the nitrogen-containing flame retardant is melamine polyphosphate (CAS No. 56386-64-2).In some embodiments, the nitrogen-containing flame retardant is melamine pyrophosphate, melamine polyphosphate, or a mixture thereof. In some embodiments where the nitrogen-containing flame retardant is melamine polyphosphate, g has an average value of greater than 2 to 10,000, more specifically 5 to 1,000, more specifically 10 to 500. In some embodiments where the nitrogen-containing flame retardant is melamine polyphosphate, g has an average value of greater than 2 to 500. Methods for making melamine phosphate, melamine pyrophosphate, and melamine polyphosphate are known in the art and are all commercially available. Melamine polyphosphates can be prepared, for example, by the reaction of polyphosphoric acid and melamine, as described in U.S. Patent No. 6,025,419 to Kasowski et al., or by heating melamine pyrophosphate under nitrogen at 290°C to constant weight, as in U.S. Patent No. 6,025,419 to Jacobson et al. granted US Patent No.6,015,510. In some embodiments, the nitrogen-containing flame retardant comprises melamine cyanurate.

[0088] The nitrogen-containing flame retardant may exhibit low volatility. For example, in some embodiments, the nitrogen-containing flame retardant exhibits a weight loss of less than 1 percent, as determined by thermogravimetric analysis, when heated at a rate of 20°C per minute from 25 to 280°C, particularly from 25 to 300°C, and even more specifically from 25 to 320°C.

[0089] In some embodiments, the flame-retardant particles have an average particle size of 10 nanometers to 1000 micrometers, preferably 100 nanometers to 500 micrometers, and more preferably 200 to 20 micrometers.

[0090] The flame-retardant particles are generally present in the flame-retardant composition in an amount of from 0.5 to 20% by weight, preferably from 1 to 10% by weight, and more preferably from 1.5 to 8% by weight, based on the total weight of the flame-retardant composition. Production of the flame-retardant composition as a single layer

[0091] To prepare the flame-retardant composition, the porous particles, the metal catalyst particles, and the flame-retardant particles are first mixed with a solvent to form a slurry. The slurry may contain a polymeric binder (where the polymers are selected from the list above). The fiber substrate is then immersed in the slurry to allow the slurry to infiltrate the substrate. Once the desired amount of slurry has infiltrated the fibers, the fiber substrate is dried to remove the solvent and any byproducts. The flame-retardant composition, which contains the fiber substrate, the porous medium, the metal catalyst particles, and the flame-retardant particles, is then applied in a single layer to the battery module and arranged on the battery cells, as shown in Fig. 1 (see first layer 202 in Fig. 1).

[0092] Optionally, the slurry, after mixing with the fiber substrate (and still in slurry form), can be poured into the module to fill any unoccupied spaces (in the module).

[0093] It should be noted that the metal catalyst particles can be added in the form of a metal salt precursor to form the slurry. The metal catalyst particles are recovered by reducing the metal salt to leave the metal catalyst particles. An exemplary reducing agent is hydrogen. Production of the flame-retardant composition in two layers

[0094] When the flame-retardant composition is added in two layers, the slurry contains only the metal catalyst particles and the flame-retardant particles. The slurry is added to the fibrous substrate to form the first composition and then separately added to the porous particles to form the second composition. The respective compositions are then each dried to remove solvents and any reaction precursors and byproducts. The compositions can be blended together and added as a single layer, as detailed above, or alternatively in two separate layers, as detailed below.

[0095] The first composition is added to the battery module as the first layer, while the second composition is placed on top of the first layer in the battery module. Both the first layer and the second layer are placed between the battery case and the battery cells, as shown in Fig. 2. In one embodiment, there may be multiple layers containing the first composition and the second composition, each alternating.

[0096] Fig.Figure 2 shows the battery module 100 with a first layer 202 (comprising a first composition) and a second layer 204 (comprising a second composition). The second layer 204, comprising the fibrous substrate, is disposed on top of the first layer 202 containing the porous particles. In one embodiment, the order of these layers may be reversed, with the first layer containing the porous particles being disposed above the second layer comprising the fibrous substrate.

[0097] In another embodiment (not shown), the flame-retardant composition may comprise a plurality of layers of the first composition and the second composition. In other words, the second layer comprising the fibrous substrate is disposed between two first layers containing the porous particles. Alternatively, the first layer comprising the porous particles may be disposed between two layers comprising the fibrous substrate.

[0098] The solvent (used to prepare the slurry) can be water, an aqueous solvent (i.e., a water-compatible solvent), a water-immiscible solvent, or a combination thereof. Supercritical and / or superheated fluids can also be used as solvents in some compositions. Aqueous solvents are preferred. Liquid carbon dioxide is also preferred. Desirable are solvents that can be combined with water to form a co-solvent capable of dissolving the salts.

[0099] The solvents can be liquid aprotic polar solvents, polar protic solvents, nonpolar solvents, or combinations thereof. Liquid aprotic polar solvents such as propylene carbonate, ethylene carbonate, butyrolactone, acetonitrile, benzonitrile, nitromethane, nitrobenzene, sulfolane, dimethylformamide, N-methylpyrrolidone, or the like, or combinations thereof, are generally desirable for dissolving or slurrying the salts and flame retardants. Polar protic solvents such as water, methanol, acetonitrile, nitromethane, ethanol, propanol, isopropanol, butanol, or the like, or combinations thereof, can be used. Other nonpolar solvents such as benzene, toluene, methylene chloride, carbon tetrachloride, hexane, diethyl ether, tetrahydrofuran, or the like, or combinations thereof, can also be used for dissolving or slurrying the salts and flame retardants.Examples of preferred solvents are water, alcohols, tetrahydrofuran, acetone or combinations thereof.

[0100] In yet another embodiment (not shown), the first composition 202 may be mixed with the second composition 204 after drying and the mixture (of the first and second compositions) may be applied in a single layer to the top of the secondary battery cells.

[0101] The flame-retardant composition has several advantages. It absorbs flammable gases in the pores of the porous substrate. It converts some of the flammable gases into intumescent carbons, which absorb heat during the intumescence process and slow heat transfer. The flame retardants prevent flammable materials from igniting.

Claims

[1] Use of a flame-retardant composition in a battery module, wherein the flame-retardant composition for a battery module comprises: a first composition comprising porous particles on which a first metal catalyst particle and a first flame-retardant particle are disposed, and a second composition comprising a fibrous composition comprising a fibrous substrate having disposed thereon a second metal catalyst particle and a second flame-retardant particle, wherein the first composition and the second composition are disposed on a plurality of battery cells in the battery module. [2] Use of the flame-retardant composition according to claim 1, wherein the first composition and the second composition are mixed in an intimate mixture and arranged in the battery module in a single layer. [3] Use of the flame-retardant composition according to claim 1, wherein the first composition is arranged in a first layer and the second composition is arranged in a second layer, the second layer being farther away from the plurality of battery cells than the first layer. [4] Use of the flame-retardant composition according to claim 1, wherein at least one layer comprising the first composition is arranged between two layers comprising the second composition. [5] Use of the flame-retardant composition according to claim 1, wherein at least one layer comprising the second composition is arranged between two layers comprising the first composition. [6] Use of the flame-retardant composition according to claim 1, wherein the first metal catalyst particle has the same chemical composition as the second metal catalyst particle. [7] Use of the flame-retardant composition according to claim 1, wherein the first metal catalyst particle has a different chemical composition than the second metal catalyst particle. [8] Use of the flame-retardant composition according to claim 1, wherein the first flame-retardant particle has the same chemical composition as the second flame-retardant particle. [9] Battery module, comprising: a plurality of secondary battery cells arranged side by side and a flame-retardant composition disposed on the plurality of secondary battery cells, the flame-retardant composition comprising a first layer having a second layer disposed thereon, the first layer comprising a first composition and the second layer comprising a second composition, the first composition comprising porous particles having a first metal catalyst particle and a first flame-retardant particle disposed thereon, and the second composition comprising a fibrous composition comprising a fibrous substrate having a second metal catalyst particle and a second flame-retardant particle disposed thereon. [10] The battery module of claim 9, wherein the porous particle is selected from the group consisting of an aerogel, fumed metal oxides, zeolites, metal-organic frameworks, or a combination thereof.

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