Protective structure of battery case

Abstract

A protective structure for protecting a battery case. The protection structure comprises a functional layer and an enhancement layer. And the functional layer comprises a flame retardant and a refractory material or an expansion additive.

Description

Technical Field

[0001] Embodiments of the present invention relate to a protective structure for a battery housing, a battery housing including the protective structure, a vehicle including the battery housing, a method of forming the protective structure, and a method of protecting a battery housing. Background Art

[0002] Battery packs have a variety of applications, such as in electric vehicles, the aerospace industry, and as storage in the electrical grid. A battery pack includes a plurality of battery cells within a housing. The housing separates the battery cells from the surrounding area, which may be, for example, the chassis of an electric vehicle.

[0003] Batteries, typically lithium-ion, are susceptible to thermal runaway events. These events can be caused by overheating, short circuits, or mechanical damage to the battery. Some battery cells also have tiny manufacturing defects that can cause thermal runaway events during normal charge or discharge cycles.

[0004] Thermal runaway events typically involve the release of combustion gases at high pressure and temperatures of about 1200°C and can propagate between cells within a battery pack, causing a chain reaction. The walls of the enclosure typically do not provide adequate protection to prevent such events. As a result, the energy generated by the runaway event can escape the enclosure, posing a safety hazard and causing damage to the surrounding area. Therefore, it is desirable to provide a protective structure for protecting the battery enclosure. Summary of the invention

[0005] According to various but not necessarily all embodiments, there is provided a protective structure for protecting a battery housing, the protective structure comprising:

[0006] a functional layer comprising a cured polymer, wherein the functional layer comprises a flame retardant and a fire resistant material dispersed in the cured polymer, or wherein the functional layer comprises an intumescent additive dispersed in the cured polymer; and

[0007] Enhancement layer.

[0008] Possibly, in use, the functional layer of the protective structure is the outermost layer of the protective structure, said outermost layer defining an exposed surface. Possibly, in use, the reinforcing layer of the protective structure is the outermost layer of the protective structure, said outermost layer defining an exposed surface.

[0009] Possibly, the protective structure is used to protect the inner surface of the battery housing. Possibly, in use, the functional layer of the protective structure is the outermost layer of the protective structure and is exposed to the inner environment of the battery housing. Possibly, in use, the reinforcing layer of the protective structure is the outermost layer of the protective structure and is exposed to the inner environment of the battery housing.

[0010] Possibly, the reinforcement layer is in the form of a reinforcement sheet, the reinforcement sheet comprising a fabric or a mesh. The fabric or the mesh may be at least partially made of glass fibers, basalt fibers, mineral fibers, ceramic fibers, carbon fibers or steel.

[0011] The reinforcing sheet may comprise a fabric having a weight of 50 gsm to 1600 gsm. The reinforcing sheet may comprise a fabric having a weight of 50 gsm to 250 gsm. Alternatively, the reinforcing sheet may comprise a fabric having a weight of 200 gsm to 1600 gsm.

[0012] The cured polymer may include a siloxane polymer, an epoxy resin, a silane terminated polymer resin, an acrylic resin, an alkyd resin, a vinyl acetate copolymer, or a combination thereof.

[0013] The flame retardant may include an endothermic additive. The endothermic additive may include an inorganic salt. The inorganic salt may be aluminum hydroxide, magnesium hydroxide or ammonium polyphosphate.

[0014] Refractory materials may include mica, clay, organoclay, talc, ceramic fibers, or borates.

[0015] The expansion additive may include a phosphorus-containing compound, a gas source, and a carbon source. The phosphorus-containing compound may include ammonium polyphosphate, triphenyl phosphate, or aluminum hypophosphite; the gas source includes melamine or boric acid; and the carbon source includes pentaerythritol or tris-(2-hydroxyethyl)isocyanurate. In some embodiments, tris-(2-hydroxyethyl)isocyanurate may be used as a gas source. Thus, tris-(2-hydroxyethyl)isocyanurate may be a carbon source and / or a gas source.

[0016] The functional layer may include a vitrifiable additive dispersed in a cured polymer. The vitrifiable additive may include a glass frit or a ceramizing agent.

[0017] The functional layer may have a thickness of 50 micrometers to 1000 micrometers.

[0018] The protective structure may further include an adhesive layer for connecting the protective structure to the surface of the battery housing. The adhesive layer may include a double-sided adhesive film or a wet contact adhesive.

[0019] The protective structure may be flexible.The protective structure may have a thickness of 50 microns to 5000 microns.

[0020] According to various but not necessarily all embodiments, there is provided a battery housing comprising a protective structure according to any of the preceding paragraphs.

[0021] Possibly, the battery housing comprises at least a first wall, wherein the reinforcement layer is at least partially located between the first wall and the functional layer.

[0022] Possibly, the battery housing comprises at least a first wall, wherein the functional layer is at least partially located between the first wall and the reinforcement layer.

[0023] According to various but not necessarily all embodiments, there is provided a vehicle comprising a battery housing according to the above paragraphs.

[0024] According to various but not necessarily all embodiments, there is provided a method for protecting a battery housing, the method comprising attaching the protective structure of any of the above paragraphs to a surface of the battery housing.

[0025] Possibly, the method comprises attaching a protective structure to an inner surface of the battery housing.

[0026] According to various, but not necessarily all, embodiments are provided as claimed in the appended claims. DETAILED DESCRIPTION

[0027] In order to better understand the various embodiments that may be helpful in understanding the detailed description, reference will now be made by way of example only.

[0028] Detailed Description

[0029] The present invention provides a protection structure for protecting a battery housing. In some embodiments, the protection structure is used to protect the inner surface of the battery housing.

[0030] The protective structure includes a functional layer and a reinforcement layer. The functional layer includes a cured polymer and one or more additives (described below) dispersed in the cured polymer. The cured polymer and additives are selected based on the desired performance of the functional layer during a thermal runaway event.

[0031] In some cases, the cured polymer is a resin. For the avoidance of doubt, unless otherwise specified, references herein to a resin are to a cured resin, not a resin precursor. A resin may also be considered a polymeric material.

[0032] In some embodiments, the functional layer includes a flame retardant and a refractory material dispersed in the cured polymer. In these embodiments, the flame retardant and the refractory material are additives contained in the functional layer. In other embodiments, the functional layer includes an expansion additive dispersed in the cured polymer. In these embodiments, the expansion additive is an additive contained in the functional layer.

[0033] The present invention also provides a battery housing including a protective structure, and a vehicle including a battery housing. The present invention also provides a method for protecting a battery housing, the method comprising connecting a protective structure to a surface of the battery housing.

[0034] The protective structure protects the battery housing from thermal runaway events.

[0035] The battery housing accommodates one or more battery cells. The battery housing includes a plurality of walls for encapsulating the battery cells. The walls of the battery housing define a cavity for positioning the battery cells. In some embodiments, the battery housing has six walls and forms a rectangular parallelepiped shape, that is, the battery housing includes an upper wall, a lower wall and four side walls. In other embodiments, the battery housing may have a more complex shape, for example including one or more curved walls. One or more walls of the battery housing may serve as a cover to allow access to the battery housing. Preferably, the battery housing is moisture-proof and sealed to prevent water from entering the cavity. The battery housing may also include one or more brackets for holding the battery cells in place within the housing. In some embodiments, the battery housing also includes a battery cooling device, which may be an air cooling system or a fluid cooling system.

[0036] The walls of the battery housing are preferably made of a rigid material such as steel, aluminum, a rigid polymeric material or a composite material. The composite material may be a sheet molding compound (SMC), also known as sheet molding compound. Sheet molding compound is made by dispersing chopped fibers such as glass fibers or carbon fibers in a thermosetting resin.

[0037] In some embodiments, the battery housing forms part of a vehicle (e.g., an electric car). The battery housing can be fixed to the frame of the vehicle, for example, under the floor of the vehicle, and typically between the axles.

[0038] The inner surface of the battery housing protected by the protective structure can be, for example, the inner surface of the wall of the battery housing (i.e., the surface of the wall facing the cavity of the battery housing). The protective structure can cover a portion or substantially all of the inner surface of the wall to prevent the energy of a thermal runaway event from escaping from the housing.

[0039] In some embodiments, the protective structure has a thickness of 50 micrometers to 5000 micrometers. Preferably, the protective structure has a thickness of 200 micrometers to 2000 micrometers.

[0040] In some embodiments, the cured polymer is flexible. In some embodiments, the cured polymer has a Shore A hardness of up to 80. The cured polymer can be a siloxane polymer, an epoxy resin, a silane-terminated polymer resin, an acrylic resin, an alkyd resin, a vinyl acetate copolymer, or a combination thereof. The cured polymer can be a copolymer, such as a copolymer resin.

[0041] Other components (ie additives) contained in the functional layer are dispersed in the cured polymer. Preferably, the functional layer has a thickness of 50 micrometers to 1000 micrometers.

[0042] In some embodiments, the reinforcement layer is in the form of a reinforcement sheet. The reinforcement layer can be considered as a reinforcing component. The reinforcement layer has a higher tensile strength and / or tear strength than the functional layer, thereby improving the tensile strength and / or tear strength of the protective structure.

[0043] The reinforcing sheet may include a fabric or a mesh. The fabric or mesh may be made partially or entirely of glass fiber (e.g., high silica glass), basalt fiber, mineral fiber, ceramic fiber, carbon fiber, steel, or any combination of these materials. The fabric may be woven or non-woven.

[0044] In some embodiments, the fabric has a weight of 50 gsm to 1600 gsm. Preferably, the fabric has a weight of 300 gsm to 900 gsm. In a preferred embodiment, the fabric is a glass fabric weighing 600 gsm. In some embodiments, the reinforcing sheet comprises a fabric weighing 50 gsm to 250 gsm. In other embodiments, the reinforcing sheet comprises a fabric weighing 200 gsm to 1600 gsm.

[0045] In some embodiments, the reinforcing fibers may be dispersed in the cured polymer of the functional layer. The reinforcing fibers may be basalt fibers, glass fibers, ceramic fibers, carbon fibers and / or mineral fibers.

[0046] In embodiments where the functional layer comprises a flame retardant and a fire resistant material dispersed in a cured polymer; the flame retardant inhibits combustion of the functional layer in a thermal runaway event. Preferably, the flame retardant comprises an endothermic additive, such as an inorganic salt.

[0047] The endothermic additive acts to cool the functional layer by an endothermic reaction in the presence of heat. The inorganic salt releases non-combustible gases (such as water or carbon dioxide) at high temperatures, thereby removing heat from the functional layer.

[0048] The inorganic salt can be aluminum hydroxide, magnesium hydroxide or ammonium polyphosphate. In some embodiments, the flame retardant includes an additional endothermic additive. The additional endothermic additive can be, for example, a different inorganic salt.

[0049] In these embodiments, the refractory material is removed or destroyed (e.g., by erosion or carbonization) in the presence of flame. The refractory material can block flame or heat for a limited time until the refractory material is completely exhausted. In certain embodiments, the refractory material comprises a mineral or ceramic. Preferably, the refractory material comprises mica, clay, organoclay, talc, ceramic fiber or borate. The refractory material is a kind of ablation or ablation additive.

[0050] In embodiments where the functional layer comprises an intumescent additive dispersed in a cured polymer; the intumescent additive expands when heated, thereby providing a low density, protective foam-like layer to thermally insulate the substrate.

[0051] In some embodiments, the expansion additive includes a phosphorus-containing compound, a gas source, and a carbon source. The phosphorus-containing compound can be, for example, ammonium polyphosphate, triphenyl phosphate, or aluminum hypophosphite. The gas source can be, for example, melamine or boric acid. The carbon source can be, for example, pentaerythritol or tris-(2-hydroxyethyl) isocyanurate.

[0052] In some embodiments, tris-(2-hydroxyethyl)isocyanurate can be used as a gas source. Thus, tris-(2-hydroxyethyl)isocyanurate can be a carbon source and / or a gas source.

[0053] In some embodiments, the functional layer includes a vitrifiable additive dispersed in a cured polymer. When exposed to heat, the vitrifiable additive vitrifies / ceramifies to form a solid or glassy layer that resists high pressure and erosion. Preferably, the vitrifiable additive includes a glass raw material or a ceramizing agent. Exemplary glass raw materials are 14019 Glass raw materials, exemplary ceramic agents include CGB 3BAM Additive and Johnson TInorganic additives.

[0054] In some embodiments, the protective structure also includes an adhesive layer for connecting the protective structure to the battery housing surface. Preferably, the adhesive layer includes a double-sided adhesive tape, such as a double-sided acrylic adhesive tape. In other embodiments, the adhesive layer can be applied as a liquid (e.g., by spraying or using a brush), such as using a liquid polymer adhesive, such as a liquid acrylic adhesive, a liquid neoprene adhesive, a liquid silicone adhesive, a liquid polyurethane adhesive, or a liquid epoxy resin adhesive.

[0055] Alternatively, or in addition to using an adhesive to attach the protective structure to the surface of the battery housing, the protective structure can be mechanically attached to the surface of the battery housing. This can be achieved by using fasteners (such as nails or rivets), or by providing a groove on the surface of the battery housing that is configured to allow insertion of at least a portion of the protective structure.

[0056] In some embodiments, the reinforcing layer is located between the adhesive layer and the functional layer. Therefore, the reinforcing layer can act as an adhesion promoter between the functional layer and the adhesive layer.

[0057] In some embodiments, in use, the functional layer of the protective structure is the outermost layer of the protective structure. In other embodiments, in use, the reinforcing layer of the protective structure is the outermost layer of the protective structure. The outermost layer of the protective structure is the layer of the protective structure that is farthest from the surface of the battery housing to which it is connected. In use, the outermost layer of the protective structure defines an exposed surface. In these embodiments, the surface of the battery housing to which the protective structure is connected can be the inner surface or the outer surface of the battery housing.

[0058] In some embodiments, where the protective structure is used to protect the inner surface of the battery housing, in use, the functional layer of the protective structure is the outermost layer of the protective structure and is exposed to the internal environment of the battery housing. Therefore, the functional layer is an exposed surface layer on the inside of the battery housing. Therefore, the reinforcement layer is at least partially located between the first wall of the battery housing and the functional layer.

[0059] In other embodiments where the protective structure is used to protect the inner surface of the battery housing, in use, the reinforcement layer of the protective structure is the outermost layer of the protective structure and is exposed to the internal environment of the battery housing. Therefore, the reinforcement layer is an exposed surface layer on the inside of the battery housing. Therefore, the functional layer is at least partially located between the first wall of the battery housing and the reinforcement layer.

[0060] In use, the outermost layer of the protective structure provides the innermost surface of the battery housing that is protected and is therefore exposed to the internal environment of the battery housing in use.

[0061] The "in use" state of the protective structure means that the protective structure is connected to the surface of the battery housing.

[0062] Exemplary protection structures are described below.

[0063] Protection structure (Example 1)

[0064] A first embodiment of a protective structure consists of a functional layer, a reinforcing layer, and an optional adhesive layer for attaching the protective structure to the inner surface of the battery housing.

[0065] In this embodiment, the functional layer provides the outermost layer of the protective structure in use and is exposed to the internal environment of the battery housing.

[0066] If present, the adhesive layer provides the innermost layer in use and may comprise a contact adhesive film with a protective film (ie, a double-sided adhesive film) which allows easy bonding to the surface to be protected. This effect may also be achieved by mechanical fixing or application of a wet contact adhesive.

[0067] Functional layer

[0068] The functional layer is a cured reaction product of a mixture having the following components: In Example 1, the functional layer comprises a flame retardant and a fire resistant material dispersed in a cured polymer.

[0069] Components Specific examples of components Amount (wt.%) Curable siloxane polymer Vinyl terminated polydimethylsiloxane 32 Siloxane Crosslinkers and Catalysts Polydimethylhydrogensiloxane with hydrosilylation catalyst 3 Flame retardants Aluminum hydroxide 7.5 Flame retardants Ammonium Polyphosphate 16 Vitrifiable Additives Glass Raw Materials 22 Refractory Materials Organic Clay 1 Refractory Materials Mica flakes 11 Processing Aids Solvents 7.5

[0070] Enhancement Layer

[0071] The reinforcement layer is in the form of a reinforcement sheet including a fabric. In this embodiment, the fabric is made of glass fiber (usually high silica glass). The fabric has a weight of 200gsm to 1600gsm and can have a weight of 600gsm. The fabric is a high temperature fabric or felt with considerable thickness and can resist a gas jet of 1200°C without melting.

[0072] Example 1 provides penetration resistance in a thermal runaway event. As described above, it consists of an external / exposed surface functional layer. The functional layer is loaded with flame retardants and refractory materials to form a hard resistant char. This is the first line of defense against erosion. The functional layer is applied to the reinforcement layer to provide structure, resistance to gas jet pressure, and additional resistance to penetration and erosion.

[0073] Protection structure (Example 2)

[0074] A second embodiment of the protective structure consists of a functional layer, a reinforcing layer, and an optional adhesive layer for attaching the protective structure to the inner surface of the battery housing.

[0075] In this embodiment, the functional layer provides the outermost layer of the protective structure in use and is exposed to the internal environment of the battery housing.

[0076] If present, the adhesive layer provides the innermost layer in use and may comprise a contact adhesive film with a protective film (ie, a double-sided adhesive film) which allows easy bonding to the surface to be protected. This effect may also be achieved by mechanical fixing or application of a wet contact adhesive.

[0077] Functional layer

[0078] The functional layer is a cured reaction product of a mixture having the following components: In Example 2, the functional layer comprises a flame retardant and a fire resistant material dispersed in a cured polymer.

[0079]

[0080]

[0081] Enhancement Layer

[0082] The reinforcement layer is in the form of a reinforcement sheet including a fabric. In this embodiment, the fabric is made of glass fiber (usually high silica glass). The fabric has a weight of 200gsm to 1600gsm and can have a weight of 600gsm. The fabric is a high temperature fabric or felt with considerable thickness and can resist a gas jet of 1200°C without melting.

[0083] Example 2 provides penetration resistance in a thermal runaway event. As described above, it consists of an outer / exposed surface functional layer. The functional layer is loaded with flame retardants and refractory materials to form a hard anti-char. This is the first line of defense against erosion. The functional layer is applied to the reinforcement layer to provide structure, resistance to gas jet pressure, and additional resistance to penetration and erosion.

[0084] Protection structure (Example 3)

[0085] A third embodiment of a protective structure is composed of a functional layer, a reinforcing layer, and an optional adhesive layer for attaching the protective structure to the inner surface of the battery housing.

[0086] In this embodiment, the functional layer provides the outermost layer of the protective structure in use and is exposed to the internal environment of the battery housing.

[0087] If present, the adhesive layer provides the innermost layer in use and may comprise a contact adhesive film with a protective film (ie, a double-sided adhesive film) which allows easy bonding to the surface to be protected. This effect may also be achieved by mechanical fixing or application of a wet contact adhesive.

[0088] Functional layer

[0089] The functional layer is the cured reaction product of a mixture having the following components: In Example 3, the functional layer comprises an intumescent additive dispersed in a cured polymer.

[0090]

[0091]

[0092] Enhancement Layer

[0093] The reinforcement layer is in the form of a reinforcement sheet comprising a fabric. In this embodiment, the fabric is glass paper. The fabric has a weight of 50 gsm to 250 gsm.

[0094] Example 3 provides insulation and heat absorption during a thermal runaway event.

[0095] In this embodiment, the outermost layer in use of the protective structure is a functional layer containing an expansion additive. The expansion additive will expand three times or more to provide a low density char. This is very insulating, but is susceptible to erosion, so it is not very suitable for areas near the initial exhaust port where the gas velocity is high.

[0096] The reinforcement layer is less important here, as it is not used to resist permeation. Typically, the reinforcement layer is a thinner and cheaper layer (compared to Examples 1 and 2 above), such as cellophane. The function of the reinforcement layer is primarily to provide a base on which the functional layer (i.e. the expanded membrane) is laid, and also to provide a keying layer for the adhesive film (if present).

[0097] Protection structure (Example 4)

[0098] A fourth embodiment of a protective structure consists of a functional layer, a reinforcing layer, and an optional adhesive layer for attaching the protective structure to the inner surface of the battery housing.

[0099] In this embodiment, the functional layer provides the outermost layer of the protective structure in use and is exposed to the internal environment of the battery housing.

[0100] If present, the adhesive layer provides the innermost layer in use and may comprise a contact adhesive film with a protective film (ie, a double-sided adhesive film) which allows easy bonding to the surface to be protected. This effect may also be achieved by mechanical fixing or application of a wet contact adhesive.

[0101] Functional layer

[0102] The functional layer is the cured reaction product of a mixture having the following components: In Example 4, the functional layer comprises an intumescent additive dispersed in a cured polymer.

[0103]

[0104]

[0105] Enhancement Layer

[0106] The reinforcement layer is in the form of a reinforcement sheet comprising a fabric. In this embodiment, the fabric is glass paper. The fabric has a weight of 50 gsm to 250 gsm.

[0107] Example 4 provides insulation and heat absorption during a thermal runaway event.

[0108] In this embodiment, the outermost layer in use of the protective structure is a functional layer containing an expansion additive. The expansion additive will expand three times or more to provide a low density char. This is very insulating, but is susceptible to erosion, so it is not very suitable for areas near the initial exhaust port where the gas velocity is high.

[0109] The reinforcement layer is less important here as it is not used to resist permeation. Typically, the reinforcement layer is a thinner and cheaper layer (compared to Examples 1 and 2 above), such as cellophane. The function of the reinforcement layer is primarily to provide a base on which the functional layer (i.e. the expanded membrane) is laid, and also to provide a bonding layer for the adhesive film (if present).

[0110] Protection structure (Example 5)

[0111] A fifth embodiment of the protective structure consists of a functional layer, a reinforcing layer, and an optional adhesive layer for attaching the protective structure to the inner surface of the battery housing.

[0112] In this embodiment, the reinforcement layer provides the outermost layer of the protective structure in use and is exposed to the internal environment of the battery housing.

[0113] If present, the adhesive layer provides the innermost layer in use and may comprise a contact adhesive film with a protective film (ie, a double-sided adhesive film) which allows easy bonding to the surface to be protected. This effect may also be achieved by mechanical fixing or application of a wet contact adhesive.

[0114] Functional layer

[0115] The functional layer is the cured reaction product of a mixture having the following components: In Example 5, the functional layer comprises an intumescent additive dispersed in a cured polymer.

[0116]

[0117]

[0118] Enhancement Layer

[0119] The reinforcement layer is in the form of a reinforcement sheet including a fabric. In this embodiment, the fabric is made of glass fiber (usually high silica glass). The fabric has a weight of 200gsm to 1600gsm, and can have a weight of 600gsm. The fabric is a high temperature fabric or felt with considerable thickness, capable of resisting a gas jet of 1200°C without melting.

[0120] Example 5 combines the functional layers of Examples 3 and 4 with the reinforcing layers of Examples 1 and 2. However, in Example 5, the outermost layer in use of the protective structure exposed to the internal environment of the battery case is the reinforcing layer.

[0121] A functional layer containing an intumescent additive is applied to the inner surface of the fabric of the reinforcement layer. Although the char formed by the functional layer is still susceptible to corrosion, it is protected by the outer reinforcement layer during the first exposure to the exhaust gas and can then safely cope with the prolonged thermal reaction and insulate the substrate.

[0122] In the above embodiments 1 to 5, the functional layer comprises a cured polymer formed by a mixture comprising one or more curable polymers and a crosslinking agent. The crosslinking agent comprises a crosslinking functional group, and the curable polymer comprises a crosslinkable functional group. In the above embodiments, the functional layer can be formed by combining the first part of the mixture with the second part of the mixture. The first part comprises a curable polymer for forming a cured polymer, and the second part comprises a crosslinking agent. The second part may also optionally comprise a catalyst. The remaining components (i.e., additives) are provided in the first and / or second parts. The first and / or second parts may also comprise conventional additional components (i.e., additives), such as a wetting agent, a dispersant, a surfactant, a solvent, or a rheology modifier.

[0123] The reaction to form the functional layer can be initiated by combining the first and second parts. The curable polymer reacts with the crosslinking agent to form a cured polymer. Thus, an exemplary functional layer includes a cured polymer with the remaining ingredients (i.e., additives) dispersed in the cured polymer.

[0124] In other embodiments, the functional layer can be formed by a single-component mixture, for example, it solidifies in response to exposure to environmental stimuli. The environmental stimulus can be UV light, or moisture and / or oxygen exposed to the atmosphere. The curable polymer and crosslinking agent can be exposed to the atmosphere after the organic solvent in the mixture evaporates, or exposed to the atmosphere by opening a container containing the mixture. Environmental stimuli activate the crosslinking agent including crosslinking functional groups and / or the curable polymer including crosslinkable functional groups to enable the curing reaction to proceed. When the functional layer is formed by a single-component mixture, in some embodiments, the crosslinking agent can be integrated into the curable polymer molecule so that the polymer is self-crosslinked (that is, the crosslinking agent including crosslinking functional groups and the curable polymer including crosslinkable functional groups are present in the same molecule). Exemplary cured polymers formed by a single-component mixture include drying oils or alkyd resins.

[0125] In some embodiments, the mixture comprises 10 wt.% to 50 wt.% of the curable polymer and the crosslinking agent. Preferably, the mixture comprises 20 wt.% to 40 wt.% of the curable polymer and the crosslinking agent.

[0126] In some embodiments, the curable polymer comprises a siloxane polymer and the crosslinking agent comprises a siloxane crosslinking agent, thereby forming a cured siloxane polymer when cured. Siloxane polymers are particularly flexible, and this property is imparted to the functional layer. The resulting flexibility of the functional layer enables the protective structure to easily conform to the curved surface within the battery housing.

[0127] A catalyst (e.g., a hydrosilylation catalyst) may also be added to the mixture to accelerate the curing process. Alternatively or additionally, the curable polymer may include an epoxy and / or silane terminated polymer with a corresponding crosslinking agent, as shown in Examples 2 and 4 above. In Examples 2 and 4, the mixture includes bisphenol A and a silane terminated polyether curable polymer, as well as isophorone diamine and aminopropyl trimethoxy silane crosslinking agents.

[0128] In some embodiments, the functional layer comprises 3 wt.% to 40 wt.% of the flame retardant. Preferably, the functional layer comprises 5 wt.% to 30 wt.% of the flame retardant. Most preferably, the functional layer comprises 15 wt.% to 25 wt.% of the flame retardant.

[0129] Preferably, the flame retardant includes an endothermic additive, such as an inorganic salt. The inorganic salt can be aluminum hydroxide, magnesium hydroxide or ammonium polyphosphate. In some embodiments, the flame retardant includes another endothermic additive. The other endothermic additive can be, for example, a different inorganic salt. In the above-mentioned embodiment 1 and embodiment 2, the flame retardant includes aluminum hydroxide and ammonium polyphosphate.

[0130] In some embodiments, the functional layer comprises 3 wt.% to 45 wt.% of the refractory material. Preferably, the functional layer comprises 5 wt.% to 22 wt.% of the refractory material.

[0131] In some embodiments, the refractory material comprises a mineral or a ceramic. Preferably, the refractory material comprises mica, clay, organoclay, talc, ceramic fiber, or borate. The functional layer may comprise 3 wt.% to 40 wt.% mica flakes. Preferably, the functional layer comprises 5 wt.% to 20 wt.% mica flakes. In some embodiments, the functional layer further comprises up to 5 wt.% organoclay, which is also a refractory material. Preferably, the functional layer comprises 0.5 wt.% to 2 wt.% organoclay. In the above-mentioned Examples 1 and 2, the organoclay is of Clay 20.

[0132] In some embodiments, the functional layer includes a vitrifiable additive dispersed in a cured polymer. Preferably, the vitrifiable additive includes a glass raw material or a ceramicizing agent. The functional layer may contain 5 wt.% to 35 wt.% of the vitrifiable additive. Preferably, the functional layer contains 15 wt.% to 25 wt.% of the vitrifiable additive.

[0133] The functional layer may contain 1 wt.% to 75 wt.% of the swelling additive. Preferably, the functional layer contains 10 wt.% to 60 wt.% of the swelling additive.

[0134] In some embodiments, the expansion additive includes a phosphorus-containing compound, a gas source, and a carbon source. The phosphorus-containing compound can be, for example, ammonium polyphosphate, triphenyl phosphate, or aluminum hypophosphite. The gas source can be, for example, melamine or boric acid. The carbon source can be, for example, pentaerythritol or tris-(2-hydroxyethyl) isocyanurate.

[0135] The expansion additive may contain 10wt.% to 40wt.% of ammonium polyphosphate. Preferably, the expansion additive may contain 20wt.% to 35wt.% of ammonium polyphosphate. The expansion additive may contain 5wt.% to 25wt.% of melamine. Preferably, the expansion additive may contain 7wt.% to 15wt.% of melamine. The expansion additive may contain 2wt.% to 25wt.% of pentaerythritol. Preferably, the expansion additive may contain 2wt.% to 12wt.% of pentaerythritol. The expansion additive may contain 2wt.% to 25wt.% of titanium dioxide. Preferably, the expansion additive may contain 2wt.% to 12wt.% of titanium dioxide. The expansion additive may contain 0.5wt.% to 10wt.% of zinc borate. Preferably, the expansion additive may contain 0.5wt.% to 5wt.% of zinc borate.

[0136] In some embodiments, the functional layer may include reinforcing fibers dispersed in the cured polymer. The reinforcing fibers serve as reinforcing components. The reinforcing fibers may be basalt fibers, glass fibers, ceramic fibers, carbon fibers and / or mineral fibers.

[0137] In some embodiments, the mixture for forming the functional layer may include one or more processing aids. One or more processing aids may include at least one of a solvent, a rheology modifier, or a dispersant. The mixture may contain up to 20 wt.% of a solvent, and preferably the mixture contains 5 wt.% to 11 wt.% of a solvent. The mixture may contain up to 2 wt.% of a rheology modifier, and preferably the mixture contains up to 0.7 wt.% of a rheology modifier. The mixture may contain up to 5 wt.% of a dispersant, and preferably the mixture contains up to 1.5 wt.% of a dispersant. Example 1 and Example 2 each include a dimethyl carbonate solvent. Example 2 includes 7420ES rheology modifier and BS1316 dispersant.

[0138] In the above embodiment, the functional layer is formed by curing a mixture, the mixture comprising: at least one curable polymer for forming a cured polymer; a cross-linking agent for forming a cured polymer; and a flame retardant and a refractory material or an intumescent additive. The mixture may contain other components as described above with respect to Embodiments 1 to 5.

[0139] In other embodiments, the functional layer can be formed by drying a mixture comprising: solidified polymer particles dispersed in a solvent; and a flame retardant and a refractory material or an expansion additive. The mixture may contain other components as described above with respect to Embodiments 1 to 5. Once the solvent evaporates, a functional layer is formed. The solvent may be a volatile organic solvent (e.g., hexane or xylene) or water. The solidified polymer particles may be made, for example, of an acrylic resin.

[0140] Exemplary Methods

[0141] Embodiments of the present invention also provide a method for forming a protective structure according to an embodiment of the present invention. The method includes: mixing components (e.g., any mixture described herein) to form a functional layer. The mixture includes at least one curable polymer and a crosslinking agent for forming a cured polymer. The method also includes allowing the mixture to cure in the presence of a reinforcement layer to provide a protective structure. In the case where the mixture includes cured polymer particles dispersed in a solvent, the method also includes drying the mixture in the presence of a reinforcement layer to provide a protective structure.

[0142] In a first embodiment of the method, the method includes applying a mixture for forming a functional layer to a first side of a reinforcement sheet as described herein, and drying or curing the mixture. Once the mixture is applied to the reinforcement sheet, before the mixture is dried or cured, the mixture can be smoothed to ensure a uniform thickness of the mixture on the reinforcement sheet.

[0143] In some embodiments of the first embodiment, the mixture is applied to the reinforcing sheet by hand and then smoothed by hand with a casting knife. In other embodiments, the reinforcing sheet is supplied by one or more rollers, and the mixture is applied by one or more nozzles located above the reinforcing sheet passing through the roller. Once the mixture is applied, the sheet can be supplied between the roller and the blade to smooth the mixture on the sheet, which is referred to as a "knife on roller" process. The blade can be positioned at a predetermined distance from the roller to ensure uniform coating of the mixture on the sheet. The coated sheet is then optionally transferred to an oven to accelerate curing and / or drying. The temperature of the oven can be 100° C. to 200° C., for example, 160° C.

[0144] In a second embodiment of the method, the method includes adding reinforcing fibers to the mixture. In a second embodiment, the mixture for forming the functional layer can be applied to the sheet / layer, and allows the use of the same exemplary method solidification / drying as described in the above-mentioned first embodiment, except that in the second embodiment, the mixture is applied to a removable backing sheet or adhesive layer, rather than being directly applied to the reinforcing sheet described in the first embodiment. After the mixture is solidified and / or dried, the functional layer obtained can be applied to the reinforcing sheet, to provide a protective structure. In these embodiments, reinforcing components are also dispersed in the cured polymer of the functional layer.

[0145] In certain embodiments, after curable polymer has been cured and / or dried, adhesive layer can be added to protective structure.In one embodiment, double-sided adhesive tape is applied to one side of protective structure.Double-sided adhesive tape is usually provided with non-adhesive film protecting each side of adhesive tape.When adhesive tape is applied to protective structure, only the non-adhesive film on one side of adhesive tape can be removed so that the other side of adhesive tape remains non-adhesive, thereby can be easily transported.When protective structure is subsequently applied to the surface of battery housing, the non-adhesive film on the other side of adhesive tape can be removed.In another embodiment, adhesive is sprayed on protective structure, rather than on adhesive tape.In certain embodiments, adhesive is preferably applied to reinforcing layer, rather than functional layer.

[0146] In embodiments where the protective structure is used to protect the inner surface of a battery housing, the protective structure can be provided in the form of a roll and then cut to fit the inner surface of the battery housing, such as the inner surface of a wall of the battery housing. Alternatively, the protective structure can be provided as a pre-cut portion to fit onto the wall of the battery housing. The protective structure can be cut into multiple portions to cover complex shapes.

[0147] The protective structure is then connected to the inner surface of the battery housing, such as the wall of the battery housing. The protective structure can be applied to the inner surface of the wall of the battery housing, and in some embodiments, the protective structure substantially covers the entire surface of the wall. In other embodiments, the protective structure only covers a portion of the wall, which may be a fragile portion of the wall. The fragile portion of the wall can be positioned so that it will be directly affected by the exhaust gas from the thermal runaway event. The battery housing can form a part of a vehicle (e.g., an electric vehicle).

[0148] In an embodiment where the protective structure is used to protect the inner surface of the battery housing and the protective structure includes an adhesive layer, the protective structure can be connected to the inner surface of the battery housing using an adhesive. Alternatively or additionally, the protective structure can be mechanically connected to the inner surface. Mechanical connection can include using one or more fasteners (such as nails or rivets) to fix the protective structure to the wall. Optionally, a groove can be provided on the wall of the housing for inserting at least part of the protective structure. In other embodiments, the protective structure can be overmolded with the battery housing. In the case of overmolding, the material forming the protective structure is placed in a tool, and a liquid resin (or polymer melt, or SMC / DMC preform) constituting the structure or part of the battery housing is injected or placed. The tool is compressed, or the resin is allowed to solidify, melt to cool, etc. Then, when the structure or component associated with the battery housing is removed from the tool, the protective structure has become a permanent layer of the structure or component of the battery housing.

[0149] Thus, described herein are protective structures, battery enclosures including protective structures, vehicles including the battery enclosures, methods of forming protective structures, and methods of protecting battery enclosures that have numerous advantages as described above and in detail below.

[0150] Due to the provision of the protective structure, the battery housing is able to withstand high heat, high pressure and high mechanical stress caused by thermal runaway events within the housing. The protective structure can be easily applied to the surface of the battery housing. For example, a single user can apply the protective structure by hand without the need for complex equipment. In addition, compared with known solutions that include thermal runaway of the battery housing, the protective structure is lower in cost, smaller in size and lighter in weight. By using a functional layer, the thickness of the protective structure can be strictly controlled over its width to maintain consistent protection and avoid weak points. The functional layer of the protective structure also prevents fibers from falling off, for example, into the battery housing.

[0151] Therefore, embodiments of the present invention protect the battery pack housing (ie, battery housing) from internal thermal runaway or external fire that may cause thermal runaway. The battery pack housing is typically made of steel sheet, aluminum, SMC / DMC, composite materials, or even thermoplastics.

[0152] Thermal runaway usually starts with a single cell, but can easily develop to include most or all cells in the battery pack. When the first cell is triggered (due to heat, overcharge, internal short circuit, external short circuit, or mechanical damage), very hot gases and molten metal (approximately 1200°C) will be rapidly discharged. This jet can penetrate the internal partitions of the battery pack, thereby triggering other cells, or penetrate the outer casing and cause an uncontrollable fire. If the components of the battery pack are directly exposed to the exhaust jet, they need to be protected by a protective layer to prevent penetration or damage. Even in cases where the jet does not penetrate the steel, the thermal effect can produce very high temperatures on the other side of the partition or outer casing, so that materials on the outside of the package may ignite.

[0153] The protection against penetration must be provided by a material having good resistance to the ablative effects of the hot gas jet, typically resistance to very high temperatures, formation of a hard glassy char, wear resistance and some insulating measure to protect the substrate. This is achieved at least by Examples 1 and 2 above.

[0154] Away from the direct gas jet, there may still be very high temperatures and turbulent flames as the emitted energy and material diffuses through the open space in the package and escapes through the pressure relief device. This is known as the ventilation path. Typically, there will be vulnerable materials in the ventilation path, such as insulating busbars, wiring and circuits / electronic devices, cooling tubes, electrical insulation layers, and even materials of the battery housing or its internal partitions may be vulnerable. This application does not require the same degree of penetration resistance or erosion resistance, but since the material may be more susceptible to temperature increases, it is important to provide good thermal insulation and / or heat absorption. This is achieved at least by Examples 3 and 4 above.

[0155] Another application is the requirement for high insulation and high corrosion resistance. This may occur where vulnerable parts are very close to the initial exhaust location, and when multiple batteries are spread within the battery pack, the internal temperature rise may be very high and last for a long time. This means that the battery pack housing needs to resist initial damage caused by direct exhaust, but also isolate the battery pack housing material to prevent it from melting (in the case of aluminum), or resin burning (in the case of SMC / DMC, composite or polymer materials) or excessive heat transfer (especially in the case of steel). Although this is a slower failure mode, it can still lead to structural damage to the package and uncontrollable fires. This is achieved at least by Example 5 above.

[0156] Although embodiments of the present invention have been described with reference to various embodiments in the preceding paragraphs, it will be appreciated that the embodiments given may be modified without departing from the scope of the invention as claimed. For example, the proportions of the various components of the mixture used to form the functional layer may be changed to provide the desired degree of protection for the battery housing, or to change the flexibility of the protective structure. For example, functional layers of different numbers or thicknesses may be provided to provide different levels of protection. The protective structure may be provided in a variety of shapes. The protective structure may not be applied directly to the wall of the battery housing. For example, the protective structure may be applied to a coating on the wall, such as an anti-corrosion coating. The protective structure may also be applied to an electromagnetic compatibility shielding disposed on the inner side of the wall, rather than being applied directly to the wall. The battery housing may include lithium-ion batteries or other types of batteries. The battery housing may be used in a variety of applications, such as electric vehicles, homes, aerospace equipment, or marine equipment.

[0157] The additives described herein may each include a single component or multiple components. For example, an intumescent additive may include multiple components in the form of a phosphorus-containing compound, a gas source, and a carbon source.

[0158] The term "comprising" as used in this document has an inclusive rather than exclusive meaning. That is, any reference to X comprising Y means that X may comprise only one Y or may comprise more than one Y. If the exclusive meaning of "comprising" is intended, it will be clear from the context by reference to "comprising only one" or by use of "consisting of."

[0159] In this specification, reference is made to various embodiments. The description of features or functions associated with an embodiment indicates that those features or functions are present in the embodiment. The use of the term "embodiment" or "for example" or "can" or "may" in the text indicates that, whether explicitly stated or not, these features or functions are present in at least the described embodiment, whether described as an embodiment or not, and they may but not necessarily be present in some or all other embodiments. Therefore, "embodiment", "for example", "can" or "may" refer to a specific instance in a class of embodiments. The attributes of an instance may be attributes of the instance only, or may be attributes of a class, or may be attributes of a subclass of a class, which includes some but not all instances in the class. Therefore, it is implicitly disclosed that features described with reference to one embodiment rather than with reference to another embodiment may be used as part of a working combination in the other embodiment where possible, but not necessarily in the other embodiment.

[0160] In addition to the combinations explicitly described above, the features described above can be used in combination. For example, the layers can be provided in a different order. A single protective structure can be applied to a single wall of the housing. Multiple protective structures can be applied to a single wall, or a single protective structure can be applied to multiple walls. One, some or all of the inner surfaces of the walls of the battery housing can be covered with protective structures.

[0161] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0162] Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

[0163] The terms "a" or "the" as used in this document have an inclusive rather than exclusive meaning. That is, any reference to X including one / the Y means that X may include only one Y or may include more than one Y, unless the context clearly indicates the contrary. If the exclusive meaning of "a" or "the" is intended, it will be clearly stated in the context. In some cases, the use of "at least one" or "one or more" can be used to emphasize the inclusive meaning, but the lack of these terms should not be understood to infer any exclusive meaning.

[0164] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself, and also to features that achieve substantially the same technical effect (equivalent features). Equivalent features include, for example, features that are modified and achieve substantially the same result in substantially the same way. Equivalent features include, for example, features that perform substantially the same function in substantially the same way to achieve substantially the same result.

[0165] In this specification, reference is made to various embodiments where adjectives or adjective phrases are used to describe features of the embodiments. Such description of features in relation to an embodiment indicates that the feature exists in some embodiments exactly as described, and in other embodiments substantially as described.

[0166] While an effort has been made in the foregoing description to focus attention on those features regarded as essential, it should be understood that the applicant may seek protection by way of claims for any patentable feature or combination of features mentioned above and / or shown in the drawings, whether or not such features are emphasized.

Claims

1. A protective structure for protecting a battery housing, the protective structure comprising: a functional layer comprising a cured polymer, wherein the functional layer comprises a flame retardant and a fire resistant material dispersed in the cured polymer, or wherein the functional layer comprises an intumescent additive dispersed in the cured polymer; and Enhancement layer. 2 . The protection structure according to claim 1 , wherein the protection structure is used to protect the inner surface of a battery housing.

3. The protective structure according to claim 2, wherein: In use, the functional layer of the protective structure is the outermost layer of the protective structure and is exposed to the internal environment of the battery housing.

4. The protective structure according to claim 2, wherein: In use, the reinforcement layer of the protective structure is the outermost layer of the protective structure and is exposed to the internal environment of the battery housing.

5. A protective structure according to any one of the preceding claims, wherein the reinforcement layer is in the form of a reinforcement sheet comprising a fabric or a mesh.

6. A protective structure according to claim 5, wherein the fabric or mesh is at least partially made of glass fibers, basalt fibers, mineral fibers, ceramic fibers, carbon fibers or steel.

7. The protective structure according to claim 5 or 6, wherein the reinforcement sheet comprises a fabric having a weight of 50 gsm to 1600 gsm.

8. A protective structure according to any one of claims 5 to 7, wherein the reinforcement sheet comprises a fabric having a weight of 50 gsm to 250 gsm.

9. The protective structure according to any one of claims 5 to 7, wherein the reinforcement sheet comprises a fabric having a weight of 200 gsm to 1600 gsm.

10. The protective structure of any one of the preceding claims, wherein the cured polymer comprises a siloxane polymer, an epoxy resin, a silane terminated polymer resin, an acrylic resin, an alkyd resin, a vinyl acetate copolymer, or a combination thereof.

11. The protective structure of any one of the preceding claims, wherein the flame retardant comprises an endothermic additive.

12. The protective structure of claim 11, wherein the endothermic additive comprises an inorganic salt.

13. The protective structure according to claim 12, wherein the inorganic salt is aluminum hydroxide, magnesium hydroxide or ammonium polyphosphate.

14. The protective structure of any one of the preceding claims, wherein the refractory material comprises mica, clay, organoclay, talc, ceramic fibers or borates.

15. The protective structure of any one of claims 1 to 10, wherein the intumescent additive comprises a phosphorus-containing compound, a gas source, and a carbon source.

16. The protective structure according to claim 15, wherein the phosphorus-containing compound comprises ammonium polyphosphate, triphenyl phosphate or aluminum hypophosphite; the gas source comprises melamine or boric acid; and the carbon source comprises pentaerythritol or tris-(2-hydroxyethyl)isocyanurate.

17. The protective structure of any one of the preceding claims, wherein the functional layer comprises a vitrifiable additive dispersed in a cured polymer, wherein the vitrifiable additive comprises a glass frit or a ceramizing agent.

18. The protective structure according to any one of the preceding claims, wherein the functional layer has a thickness of 50 to 1000 microns.

19. The protective structure of any one of the preceding claims, wherein the protective structure further comprises an adhesive layer for attaching the protective structure to a surface of a battery housing.

20. The protective structure of claim 19, wherein the adhesive layer comprises a double-sided adhesive film.

21. The protective structure according to any one of the preceding claims, wherein the protective structure is flexible.

22. The protective structure of any one of the preceding claims, wherein the protective structure has a thickness of 50 to 5000 microns.

23. A battery housing comprising a protective structure according to any one of the preceding claims.

24. The battery housing of claim 23, wherein the battery housing comprises at least a first wall, wherein the reinforcement layer is at least partially located between the first wall and the functional layer.

25. The battery housing of claim 23, wherein the battery housing comprises at least a first wall, wherein the functional layer is at least partially located between the first wall and the reinforcement layer.

26. A vehicle comprising a battery housing according to any one of claims 23 to 25.

27. A method for protecting a battery housing, the method comprising attaching the protection structure of any one of claims 1 to 22 to a surface of the battery housing.

28. The method of claim 27, wherein the method comprises attaching a protective structure to an inner surface of the battery housing.

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