Fire-resistant and heat-insulating compositions and methods of using same

Abstract

1. A fire and heat insulating composition comprising sodium silicate and / or lithium silicate and further or other filler or binder materials, wherein when the composition is applied to a battery cell, it acts as a thermally conductive coating at normal operating temperatures of the battery cell, and when exposed to higher temperatures, the sodium silicate and / or lithium silicate undergo hydrothermal crystallization to amorphous silica, and the coating acts as an insulating barrier for the battery cell.

Description

Detailed Description of the Invention

[0001] [Field]

[0001] The present invention relates to fire and heat insulating compositions and methods of using same. Although the invention will be described with reference to their use with battery cells, it will be recognized that the invention is not limited to this application and other applications are also contemplated.

[0002] [background] The following discussion of the background of the invention is intended solely to facilitate an understanding of the invention. It should be recognized that the discussion does not constitute an admission or acceptance that any of the material referred to was published, publicly known, or part of the common general knowledge of one of ordinary skill in the art in any jurisdiction as of the priority date of the present invention.

[0003]

[0003] Battery thermal runaway is the primary cause of explosions in electric cars and motorcycles during charging. Thermal runaway occurs when a Li-ion cell is overcharged and reaches a threshold temperature, after which the temperature rises rapidly on its own. Thermal runaway barriers are used to suppress the propagation of flames during thermal runaway.

[0004]

[0004] Thermal management materials in battery modules are essentially divided into two categories: thermal interface materials and thermal runaway barriers. Thermal interface materials serve to dissipate heat from battery cells during normal operating temperatures between 20 and 80°C. Therefore, these materials are inherently thermally conductive. However, at higher temperatures, e.g., 250°C, these materials tend to melt and / or decompose, failing to provide sufficient protection against flame propagation in the event of thermal runaway. Thermal runaway barriers, on the other hand, are inherently insulating and therefore can prevent flames from spreading from one part of the battery module to another in the event of thermal runaway. However, these barriers are unable to dissipate heat under normal battery operating conditions. Therefore, battery life tends to deteriorate due to their exposure to high temperatures over long periods of time.

[0005]

[0005] It would therefore be advantageous to have a thermal management material that can act as a thermal interface material at the normal operating temperatures of a battery cell and as a thermal runaway barrier in the event of thermal runaway.

[0006] [overview]

[0006] According to an aspect of the present disclosure, 1. A fire and heat insulating composition comprising sodium silicate and / or lithium silicate and additional or other filler or binder materials, wherein the composition, when applied to said battery cell, acts as a thermally conductive coating at the normal operating temperature of the battery cell, and the sodium silicate and / or lithium silicate undergo hydrothermal crystallization to amorphous silica when exposed to higher temperatures, and the coating acts as an insulating barrier for the battery cell. is provided.

[0007] In some embodiments, the filler material includes one or more of a pore former, a rheology modifier, a thermally insulating filler, and a thermally conductive filler.

[0008]

[0008] In some embodiments, the pore former is starch.

[0009] In some embodiments, the pore former is provided by sodium silicate and / or lithium silicate.

[0010] In some embodiments, the rheology modifier is starch, fumed silica, and / or cellulose or a cellulose derivative.

[0011]

[0011] In some embodiments, the starch is derived from corn, tapioca, wheat, or rice.

[0012] In some embodiments, the insulating filler is fumed silica and / or aerogel.

[0013] In some embodiments, the thermally conductive filler is selected from one or more of boron nitride, aluminum nitride, aluminum oxide, and magnesium oxide.

[0014] In some embodiments, the fire and heat protection composition further comprises a UV curing agent.

[0015] In some embodiments, the fire and heat insulating composition further comprises cellulose.

[0016] In some embodiments, the fire and heat protection composition further comprises a surfactant.

[0017] In some embodiments, the fire and heat protection composition further comprises gypsum.

[0018] In some embodiments, the sodium silicate and / or lithium silicate is in the range of 35 to 60 Baume.

[0019] In some embodiments, the sodium silicate and / or lithium silicate is in the form of a powder.

[0020] In some embodiments, the fire and heat insulating composition comprises: a) 90-95 wt% sodium silicate; b) 1-5 wt% corn starch; c) 1 to 5 wt% cellulose, and d) 1-5% surfactant Includes:

[0021] In some embodiments, the fire and heat insulating composition comprises: a) 30-50 wt% sodium silicate; b) 5-20 wt% lithium silicate; c) 30-50 wt% aluminum nitride; d) 1-5 wt% corn starch; e) 1 to 5 wt. % fumed silica, and f) 1 to 5 wt% surfactant Includes:

[0022] In some embodiments, the fire and heat insulating composition comprises: a) 50-65 wt% sodium silicate; b) 30-50 wt% boron nitride; c) 1-5 wt% Irgacure 819, d) 1 to 5 wt% cellulose, and e) 1 to 5 wt% surfactant Includes:

[0023] In some embodiments, the fire and heat insulating composition comprises: a) 50-60 wt% sodium silicate; b) 30-59 wt% boron nitride; c) 1-5 wt% fumed silica; d) 1 to 5 wt% cellulose, and e) 1 to 5 wt% surfactant Includes:

[0024] In some embodiments, the fire and heat insulating composition comprises: a) 40-60 wt% sodium silicate (SiO2:Na2O=3.22), b) 30-50 wt% boron nitride, and c) 3 to 15 wt% gypsum Includes:

[0025] In some embodiments, the sodium silicate and / or lithium silicate is in the form of sodium metasilicate hydrate and / or lithium metasilicate hydrate.

[0026]

[0026] In some embodiments, the sodium metasilicate hydrate and / or lithium metasilicate hydrate is in the form of sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, lithium metasilicate, or lithium disilicate.

[0027] In some embodiments, the sodium metasilicate hydrate and / or lithium metasilicate hydrate is in an encapsulated form.

[0028] In some embodiments, the binder material is a silicone rubber RTV.

[0029] In some embodiments, the binder material is a silane-grafted polyurethane.

[0030] In some embodiments, the binder material is a water-based acrylic.

[0031] In some embodiments, the binder material is a siloxane.

[0032] In some embodiments, the fire and heat insulating composition further comprises a thermally conductive filler.

[0033] In some embodiments, the thermally conductive filler is selected from one or more of boron nitride, aluminum nitride, aluminum oxide, and magnesium oxide.

[0034] In some embodiments, the fire and heat insulating composition comprises: a) 30 to 70 wt% silicone rubber RTV, b) 20-70% boron nitride, and c) 10 to 30 wt% acid-treated sodium metasilicate pentahydrate Includes:

[0035] In some embodiments, the fire and heat insulating composition comprises: a) 30 to 70 wt% silicone rubber RTV, b) 30-70 wt% boron nitride; c) 10 to 30 wt% acid-treated lithium metasilicate, and d) 10-30 wt% encapsulated sodium metasilicate nonahydrate Includes:

[0036] In some embodiments, the fire and heat insulating composition comprises: a) 30 to 70 wt% silicone rubber RTV, b) 30 to 70 wt% aluminum nitride, and c) 10-30 wt% encapsulated sodium metasilicate pentahydrate Includes:

[0037] In some embodiments, the fire and heat insulating composition comprises: a) 30-70% silane-grafted polyurethane; b) 20-70% boron nitride; c) 1-5% siloxane; d) 1-3% surfactant, and e) 10-30% sodium metasilicate pentahydrate Includes:

[0038] In some embodiments, the fire and heat insulating composition comprises a) 30-70% water-based acrylic, b) 20-70% boron nitride; c) 1-3% surfactant, and d) 10-30% sodium metasilicate pentahydrate Includes:

[0039] In some embodiments, the fire and heat insulating composition comprises: a) 30-70% silicone rubber RTV, b) 10-50% boron nitride; c) 20-50% siloxane; d) 1-3% surfactant, and e) 10-30% sodium metasilicate pentahydrate Includes:

[0040] In some embodiments, the fire and heat insulating composition further comprises 5-30 wt% of a reinforcing material.

[0041] In some embodiments, the reinforcing material is selected from one or more of glass / ceramic wool, chopped strands, fibers, or whiskers.

[0042] In accordance with another aspect of the present invention, there is provided a composite sheet comprising an inorganic substrate layer having applied thereto a layer of a fire and heat insulating composition.

[0043] In some embodiments, the inorganic substrate layer is in the form of a glass / ceramic mat or fabric.

[0044]

[0044] According to a further aspect of the present disclosure, there is provided a method for providing fire protection and thermal insulation to a battery cell, the method comprising the step of coating or covering at least the cathode and / or vent of the battery cell with the above-mentioned fire protection and thermal insulation coating.

[0045]

[0045] Other aspects and features will become apparent to those skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying drawings.

[0046]

[0046] The drawings illustrate embodiments of the present invention, by way of example only. [Brief explanation of the drawings]

[0047] [Figure 1] The left image shows the encapsulated metasilicate particles, and the right image is a photographic image showing an optical micrograph of the sol-gel formed shell after extraction of the metasilicate core with water. [Figure 2a] 1 is a photographic image showing a battery cell coated with a fire and thermal barrier coating according to the present disclosure at the cathode terminal of the battery cell, where a battery vent is also located. [Figure 2b] 1 is a photographic image showing the test setup used to heat coated battery cells to temperatures above 160° C. [Figure 2c] 1 is a photographic image showing the formation of expansion bubbles in the coating of a battery cell after 10 minutes of heating. [Figure 2d] Photographic image showing the appearance of the coated side of the battery cell after heating to over 160°C for 90 minutes, with no onset of thermal runaway detected. [Figure 3] 1 is a photographic image showing a fire test performed on a steel substrate coated with a fire and thermal barrier coating according to the present disclosure. [Figure 4] FIG. 4 is a graph comparing substrate temperatures between coated and uncoated substrates during the test shown in FIG. 3. [Figure 5a] 1 is a photographic image showing the appearance of a highly thermally conductive PDMS compound before exposure to high temperatures. [Figure 5b] 5a is a photographic image showing foaming of the PDMS compound of [FIG. 5a] upon exposure to elevated temperatures. [Figure 5c]

[0033] Figure 5a is a photographic image showing how foaming also causes the PDMS compound to expand. [Figure 6] FIG. 1 is an enlarged view of a battery module including a top protective sheet having a composition according to the present disclosure. [Figure 7] 7 is a photographic image of the battery holder and top protective sheet of the battery module of [FIG. 6] after exposure to temperatures above 120° C.

[0048] [Detailed explanation]

[0059] Throughout this document, unless otherwise indicated to the contrary, terms such as "including," "consisting of," "having," etc. are to be construed as non-exhaustive, or in other words, as meaning "including but not limited to."

[0049]

[0060] Furthermore, throughout this specification, unless the context requires otherwise, the word "include" or variations such as "includes" or "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

[0050]

[0061] According to the present disclosure, a highly thermally conductive composition is provided that is primarily formulated to be coated or disposed on a battery cell to aid in heat dissipation during normal battery operating temperatures, e.g., between 20 and 80°C. However, should the battery cell be overheated, e.g., above 120°C, the composition will transform into an insulating barrier due to foaming caused by hydrothermal crystallization. The composition may be free of any intumescent flame retardants or foaming agents that release phosphate-nitrogen compounds. The composition can be manufactured in various forms, including, but not limited to, coatings, potting materials, pastes, or as solid sheets.

[0051]

[0062] According to one aspect of the present disclosure, the fire and heat-insulating composition, when used as a coating, may use sodium silicate and / or lithium silicate as its primary component and is itself non-combustible. Various grades of sodium / lithium silicate with varying SiO:NaO or SiO:LiO contents, e.g., 35-60 Baumé, can be used. It is also contemplated that sodium / lithium silicate may be used in the fire and heat-insulating composition according to the present disclosure in the form of sodium / lithium metasilicate, examples of which will be described subsequently.

[0052]

[0063] The viscosity and transparency of sodium silicate / lithium silicate can be adjusted based on its grade and the incorporation of fillers and surfactants. Mixtures of sodium silicate and lithium silicate can also provide coatings with varying degrees of water resistance. The fillers used consist of mixtures of starch, fumed silica, cellulose, and ceramics, each of which contributes differently but synergistically to the coating's thermal conductivity, thermal insulation, and fire resistance. Starch can be derived from corn, tapioca, wheat, or rice. Starch is used as a pore former and rheology modifier for the coating. Cellulose and its derivatives can also be used as rheology modifiers. Cellulose creates a porous but denser structure in the silicate, which forms an insulating wall when exposed to an open flame. This is particularly important for preventing thermal runaway in batteries, which will be discussed later. Sodium silicate and / or lithium silicate can also act as a pore former. Furthermore, thermal reflectivity of the coating can be achieved through char formation from starch upon contact with flame. Using fumed silica as an effective rheological modifier, silicates can be formulated into pastes or gels. It has been found that in this coating, fumed silica acts as a flame retardant additive in synergy with starch, stabilizing and strengthening char layer formation, preventing the coating from cracking after prolonged flame exposure. Aerogels can also be used as insulating fillers. Unlike conventional intumescent coatings that rely on gases such as nitrogen and phosphate to create large, open-celled, bubble-like structures, the cell structure of the fire and thermal insulation coatings disclosed herein is closed and denser. These features are important for the coating to provide good thermal insulation performance and prolong heating of the substrate when exposed to flame. In certain cases, UV curing agents such as Irgacure 819 (a registered trademark of BASF) are incorporated to achieve rapid curing of the coating and prevent sagging, especially when the coating is sprayed onto vertical surfaces.In this case, the coating stops flowing in about 1-6 minutes upon UVA exposure after spraying.

[0053]

[0064] The sodium silicate and / or lithium silicate can act as a binder material if they are already in aqueous solution, or as a filler material if they are in an encapsulated form as will be described subsequently. Alternatively, the sodium silicate and / or lithium silicate can be in powder form.

[0054]

[0065] The composition of a first example embodiment of a fire and heat insulating composition according to the present disclosure is shown in the table below, entitled Example 1. The composition according to Example 1 can provide a coating that will convert to a thermal overrun insulating layer at a trigger temperature of, for example, 120°C.

[0055] [Table 1]

[0056]

[0066] The composition of a second example embodiment of a fire and heat insulating composition according to the present disclosure is shown in the table below, entitled Example 2. The composition according to Example 2 will convert to a thermal overheat insulator at a trigger temperature of, for example, 120°C, while providing a high thermal conductivity coating with better water resistance.

[0057] [Table 2]

[0058]

[0067] The composition of a third example embodiment of a fire and heat insulating composition according to the present disclosure is shown in the table below, entitled Example 3. The composition according to Example 3 can provide a UV-curable, high thermal conductivity coating that will convert to a thermal insulator at a trigger temperature of, for example, 120°C.

[0059] [Table 3]

[0060]

[0068] The composition of a fourth example embodiment of a fire and heat insulating composition according to the present disclosure is shown in the table below, entitled Example 4. The composition according to Example 4 can provide a highly thermally conductive paste that will convert to a thermal insulator at a trigger temperature of, for example, 120°C.

[0061] [Table 4]

[0062]

[0069] The composition of a fifth example embodiment of a fire protection and thermal insulation composition according to the present disclosure is shown in the table below, entitled Example 5. The composition according to Example 5 can provide a highly thermally conductive putty that will convert to thermal insulation at a trigger temperature of, for example, 120°C.

[0063] [Table 5]

[0064]

[0070] All components described in Examples 1-5 can be mixed at room temperature using a standard propeller mixer set at 1200 rpm. The mixing time varies between 20 and 40 minutes, and the resulting solution should be completely dispersed without clumping. In some cases, phase separation may occur between the solid and liquid components. However, these can be easily dispersed by stirring at 1200 rpm.

[0065]

[0071] According to another aspect of the present invention, the fire and heat protection composition may use as its main component sodium / lithium silicate in the form of sodium metasilicate hydrate (SMS) or lithium metasilicate hydrate (LMS). The sodium metasilicate hydrate and / or lithium metasilicate hydrate may be, for example, in the form of sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, lithium metasilicate, or lithium disilicate.

[0066]

[0072] Sodium silicate and lithium silicate are highly alkaline compounds that can react or corrode certain materials, such as aluminum, zinc, and polycarbonate, when they come into direct contact with them. To prevent such corrosion and reaction, sodium metasilicate hydrate (SMS) or lithium metasilicate hydrate (LMS) can be incorporated as a filler into other neutral binders, such as polydimethylsiloxane (silicone rubber), silane-grafted polyurethane, water-based acrylics, and siloxanes. These metasilicates may be incorporated in their native form as long as they do not leach out of the binder. In certain instances, where their concentration in the binder is high (e.g., >20 wt%), leaching of the metasilicate can occur. In such instances, metasilicate particles can be surface-treated or encapsulated to significantly reduce the surface pH and prevent the particles from reacting with their surrounding environment if they leach out of the binder. Surface treatment of the metasilicate can be achieved by exposing the particles to acid. During this process, a thin layer of cross-linked silica gel is eventually formed by the neutralized porous silicic acid layer. To further stabilize the metasilicate particle surface, the particles can be encapsulated using sol-gel techniques and related materials. The process can be carried out in a solvent in which the metasilicate remains insoluble or shows very limited solubility. The solubility of the acid and the sol-gel precursor used in the same solvent can be tolerated.

[0067]

[0073] According to one possible method of the present disclosure, a predetermined amount of acid (e.g., maleic acid or hydrochloric acid) is dissolved in a solvent (e.g., ethanol, methanol, isopropanol). Subsequently, a predetermined amount of metasilicate is added, and the resulting slurry is stirred until the acid in the solvent is consumed (final pH of about 7). In the next step, a sol-gel precursor is added. The precursor selection may include trimethoxymethylmethylsilane (MTMS), triethoxyethylsilane (ETES), and tetraethylorthosilicate (TEOS). The molar ratio of the trifunctional silane to TEOS may vary widely, ranging from 1:10 to 10:1. The mixture is stirred for at least 60 minutes. The encapsulated metasilicate is then washed with an excess of the previously used solvent, isolated using vacuum-assisted filtration, and dried in a vacuum oven at a temperature not exceeding 70°C.

[0068]

[0074] Referring to Figure 1, the image on the left shows the encapsulated metasilicate particles, while the image on the right shows an optical micrograph of the sol-gel formed shell after extraction of the metasilicate core with water.

[0069]

[0075] The composition of a sixth example embodiment of a fire protection and thermal insulation composition according to the present disclosure is shown in the table below entitled Example 6. The composition according to Example 6 can provide a high thermal conductivity silicone rubber that will convert to thermal insulation at a trigger temperature of, for example, 120°C.

[0070] [Table 6]

[0071]

[0076] The composition of a seventh example embodiment of a fire protection and thermal insulation composition according to the present disclosure is shown in the table below entitled Example 7. The composition according to Example 7 can provide a high thermal conductivity silicone rubber that will convert to thermal insulation at a trigger temperature of, for example, 120°C.

[0072] [Table 7]

[0073]

[0077] The composition of an eighth example embodiment of a fire protection and thermal insulation composition according to the present disclosure is shown in the table below, entitled Example 8. The composition according to Example 8 can provide a high thermal conductivity silicone rubber that will convert to thermal insulation at a trigger temperature of, for example, 120°C.

[0074] [Table 8]

[0075]

[0078] It is also contemplated that reinforcing materials may be included within the fire protection and thermal insulation compositions of the present disclosure. For example, 5-30 wt. % of short inorganic reinforcing materials, such as glass / ceramic wool, chopped strands, fibers, or whiskers, may be incorporated into the composition to provide additional structural properties, if desired. Alternatively, the fire protection and thermal insulation compositions of the present disclosure may also be coated onto continuous inorganic reinforcing materials, for example, in the form of glass / ceramic mats or fabrics, to obtain composite sheets that may contain more than 50 wt. % of such reinforcing materials.

[0076]

[0079] Thermal runaway in batteries is primarily caused by overheating, which occurs either when the battery is overcharged or when there is an electrical short circuit. If the temperature reaches the breakdown point of the battery's separator, an internal short circuit occurs between the cathode and anode, causing the highly flammable electrolyte to vaporize and escape through the opening in the battery cell. This can initiate spontaneous combustion if a spark occurs. If the separator completely decomposes and punctures, the electrolyte allows a mass flow of electrons, resulting in a redox reaction between the anode and cathode. This reaction contributes most of the heat and is the primary cause of thermal runaway, which can lead to massive expansion, rupture, eruptions, sparks, smoke, fire, and explosions. If gases escaping from the battery chamber come into contact with sparks generated by the electrodes, they can ignite due to combustion. The temperature at which the gases escape from the battery casing depends on the type of solvent used: DMC (90°C), EMC (108°C), and DEC (128°C). It is worth noting that if there is an insufficient amount of oxygen, combustion will not occur inside the battery cell.

[0077]

[0080] Applicant conducted testing of hard-cased 18650 battery cells by heating the battery cells to over 160°C. It was found that thermal runaway of the battery cells occurred within four minutes when heated above 160°C. Furthermore, after heating the battery cells to over 160°C for an extended period of time, a large amount of components were ejected from the cell, followed by sparks from electrode meltdown and ultimately an explosion of the battery cell.

[0078]

[0081] When a battery cell was coated with one of the coatings having the compositions presented in Examples 1-5 at the cathode terminal where the battery vent valve was located, thermal runaway did not begin even when the cell was heated above 160°C for more than 90 minutes. The coating thickness in the cathode region was approximately 0.5-2 mm, as shown in Figure 2a. Figure 2b shows a coated battery heated above 160°C, at which point the coating began to form a bubble-like structure via hydrothermal crystallization at the top of the battery cell, as shown in Figure 2c. The foaming indicates that the coating was able to absorb heat and form a barrier around the cathode. After heating the battery for approximately 90 minutes, a brown stain was observed at the coating-cathode interface due to electrolyte blowout (Figure 2d), while there was no evidence of sparks, spark initiation, or combustion. Applicants demonstrate that when the components inside the cell are heated and reach their respective decomposition / boiling points, the coating forms a porous barrier to release these components but prevent the formation of sparks. Effective spark prevention is believed to be a key factor in preventing significant spontaneous redox reactions between the electrodes and therefore mitigating the occurrence of full thermal runaway.

[0079]

[0082] These coatings can also be applied to metals or plastics such as battery casings and thermal runaway barriers to provide good thermal insulation and fire protection. These coatings exhibit high thermal conductivity (>1 W / mK) but low electrical conductivity (>10 6 It is noteworthy that the resistance is ohms.

[0080]

[0083] [Figure 3] shows fire tests conducted on steel substrates coated with fire and thermal barrier coatings according to Examples 1-5 of the present disclosure. [Figure 4] is a graph comparing substrate temperatures during the fire tests shown in [Figure 3] between coated and uncoated steel substrates with the coating compositions described in Examples 1-5.

[0081]

[0084] Solid metasilicates, either in their native or encapsulated form, were incorporated into neutral binders, such as (but not limited to) polydimethylsiloxane (PDMS), listed in Examples 6-8, and the resulting compounds exhibited at least a 10-fold increase in thermal conductivity compared to untreated PDMS. However, when these compounds were exposed to temperatures above 500°C, foaming occurred, and the compounds exhibited at least 30% better thermal insulation and a 20% expansion in volume compared to untreated PDMS. These compounds are therefore ideal for use as thermal interface materials in battery modules to dissipate heat and as thermal runaway barriers to prevent the spread of flames in the event of a thermal runaway. The expansion of the compounds upon heating allows them to seal existing crevices and prevent further flame propagation.

[0082]

[0085] [Figure 5a] shows the appearance of a highly thermally conductive PDMS compound before exposure to high temperatures. [Figure 5b] shows the PDMS compound foaming upon exposure to high temperatures (e.g., 200°C). [Figure 5c] shows how foaming also causes the PDMS compound to expand, e.g., by approximately 20% in the example shown.

[0083]

[0086] [Fig. 6] shows an example of a battery module 1 including a battery casing 3 having a battery casing cover 11. A plurality of batteries (e.g., 18650 batteries) are positioned within the battery casing 3, and each battery 7 is supported within a battery holder 5 made of a highly thermally conductive compound. An upper protective sheet 9 having a composition according to Examples 6 to 8 of the present disclosure is positioned on the batteries 7.

[0084]

[0087] [Figure 7] shows the battery holder 5 and top protective sheet 9 of the battery module 1 of [Figure 6], which are composed of a fire-resistant and heat-insulating composition according to the present disclosure, after exposure to temperatures above 120°C. [Figure 7] particularly shows the hydrothermal crystallization that occurs within the composition of the battery holder 5 and top protective sheet 9 after exposure to high temperatures.

[0085]

[0088] Fire and heat insulating compositions according to the present disclosure may provide the following features and advantages: i) A halogen-free, water-based coating that can function as both a thermal interface material and a thermal runaway barrier in a battery module. ii) A compound consisting of a pH-neutral binder (e.g., PDMS), sodium metasilicate / lithium metasilicate powder, and a ceramic filler (e.g., boron nitride) that is highly thermally conductive at normal operating temperatures (e.g., 20-80 °C), and that will foam at high temperatures (e.g., above 120 °C) and turn into a fire-resistant, insulating barrier. iii) An encapsulation method that results in a pH-neutral shell surrounding the sodium metasilicate / lithium metasilicate particles. iv) An encapsulation method in which the shell thickness is adjusted so that the trigger temperature (the temperature at which the metasilicate begins to foam) can be adjusted. v) Coating the battery cell at the cathode terminal where the vent is located to prevent the onset of thermal runaway. vi) Coating the entire battery module with a highly thermally conductive coating to allow heat dissipation from the battery cells to the battery casing during normal battery operating temperatures, the same coating also transforms into an insulating barrier that prevents flame propagation in the event of thermal runaway.

[0086]

[0089] Although the fire and thermal barrier coating has been specifically described with reference to its use in preventing thermal runaway in batteries, the coating can also be used in other applications such as: i) A coating on the battery that dissipates heat during operating temperatures and prevents thermal runaway if the battery temperature gets too high. The coating may also insulate the battery against external heating / flame. ii) Coatings on fire door panels and other combustible materials (e.g., wood, polymer foam, honeycomb core) that provide additional insulation. iii) As a flame retardant coating on furniture or panels made of combustible materials (e.g. polyurethane foam, wood, plastic and fabric). iv) As a fire retardant coating in electrical panels / PCBs. v) As fire and thermal insulation coatings on building materials.

[0087]

[0090] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter herein belongs.

[0088]

[0091] Those skilled in the art should realize that the above invention is not limited to the described embodiments and that variations and modifications can be made without departing from the scope of the invention.

[0089]

[0092] Furthermore, those skilled in the art should recognize that one or more of the above variations or modifications are not mutually exclusive and can further be combined to form still further embodiments of the present invention.

Claims

1. 1. A fire and heat insulating composition comprising encapsulated sodium silicate and / or encapsulated lithium silicate and other filler or binder materials, the filler or binder materials comprising a thermally conductive filler, wherein the composition, when applied to a battery cell, acts as a thermally conductive coating at normal operating temperatures of the battery cell, and the sodium silicate and / or lithium silicate undergo hydrothermal crystallization to amorphous silica when exposed to higher temperatures, and the coating acts as an insulating barrier for the battery cell.

2. 10. The fire and heat insulating composition of claim 1, wherein the filler material comprises one or more of a pore former, a rheology modifier, a thermally insulating filler, and the thermally conductive filler.

3. 3. The fire and heat insulating composition of claim 2, wherein said pore former is starch.

4. 4. The fire and heat protection composition according to claim 2 or 3, wherein the pore former is provided by the sodium silicate and / or lithium silicate.

5. 3. The fire and heat insulating composition of claim 2, wherein the rheology modifier is starch, fumed silica, and / or cellulose or a cellulose derivative.

6. 6. The fire and heat insulating composition of claim 3 or 5, wherein the starch is derived from corn, tapioca, wheat or rice.

7. 3. The fire and heat insulating composition according to claim 2, wherein the insulating filler is fumed silica and / or aerogel.

8. 3. The fire and heat insulating composition of claim 2, wherein the thermally conductive filler is selected from one or more of boron nitride, aluminum nitride, aluminum oxide, and magnesium oxide.

9. 10. The fire and heat insulating composition of claim 1, further comprising a UV curing agent.

10. 10. The fire and heat insulating composition of claim 1 further comprising cellulose.

11. 10. The fire and heat insulating composition of claim 1, further comprising a surfactant.

12. 10. The fire and heat insulating composition of claim 1 further comprising gypsum.

13. 2. The fire and heat insulating composition of claim 1, wherein the sodium silicate and / or lithium silicate has a viscosity in the range of 35 to 60 Baume.

14. 2. The fire and heat insulating composition of claim 1, wherein the sodium silicate and / or lithium silicate is in the form of a powder.

15. a) 90-95 wt. % sodium silicate; b) 1 to 5 wt % corn starch; c) 1 to 5 wt % cellulose, and d) 1-5% surfactant 3. The fire and heat insulating composition of claim 2, comprising:

16. a) 30 to 50 wt. % sodium silicate; b) 5 to 20 wt % lithium silicate; c) 30 to 50 wt % aluminum nitride; d) 1 to 5 wt. % corn starch; e) 1 to 5 wt % fumed silica, and f) 1 to 5 wt % of a surfactant 3. The fire and heat insulating composition of claim 2, comprising:

17. a) 50 to 65 wt. % sodium silicate; b) 30-50 wt % boron nitride; c) 1-5 wt% Irgacure 819; d) 1 to 5 wt % cellulose, and e) 1 to 5 wt % of a surfactant 3. The fire and heat insulating composition of claim 2, comprising:

18. a) 50 to 60 wt. % sodium silicate; b) 30-59 wt % boron nitride; c) 1 to 5 wt % fumed silica; d) 1 to 5 wt % cellulose, and e) 1 to 5 wt % of a surfactant 3. The fire and heat insulating composition of claim 2, comprising:

19. a) 40 to 60 wt % sodium silicate (SiO2:Na2O=3.22); b) 30-50 wt % boron nitride, and c) 3 to 15 wt% gypsum 3. The fire and heat insulating composition of claim 2, comprising:

20. 2. The fire and heat insulating composition of claim 1, wherein the sodium silicate and / or lithium silicate is in the form of sodium metasilicate hydrate and / or lithium metasilicate hydrate.

21. 21. The fire and heat insulating composition of claim 20, wherein the sodium metasilicate hydrate and / or lithium metasilicate hydrate is in the form of sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, lithium metasilicate, or lithium disilicate.

22. 22. The fire and heat insulating composition of claim 20 or 21, wherein the binder material is a silicone rubber RTV.

23. 22. The fire and heat insulating composition of claim 20 or 21, wherein the binder material is a silane-grafted polyurethane.

24. 22. The fire and heat insulating composition of claim 20 or 21, wherein the binder material is a water-based acrylic.

25. 22. The fire and heat insulating composition according to claim 20 or 21, wherein the binder material is a siloxane.

26. 21. The fire and heat insulating composition of claim 20, further comprising a thermally conductive filler.

27. 27. The fire and heat insulating composition of claim 26, wherein the thermally conductive filler is selected from one or more of boron nitride, aluminum nitride, aluminum oxide, and magnesium oxide.

28. a) 30 to 70 wt % silicone rubber RTV; b) 20-70% boron nitride, and c) 10 to 30 wt % acid-treated sodium metasilicate pentahydrate 23. The fire and heat insulating composition of claim 22, comprising:

29. a) 30 to 70 wt % silicone rubber RTV; b) 30-70 wt % boron nitride; c) 10 to 30 wt % acid-treated lithium metasilicate, and d) 10-30 wt % encapsulated sodium metasilicate nonahydrate Including, 23. The fire and heat insulating composition of claim 22, wherein the components of the composition are combined to total 100 wt%.

30. a) 30 to 70 wt % silicone rubber RTV; b) 30 to 70 wt % aluminum nitride, and c) 10-30 wt % encapsulated sodium metasilicate pentahydrate Including, 23. The fire and heat insulating composition of claim 22, wherein the components of the composition are combined to total 100 wt%.

31. a) 30-70% silane-grafted polyurethane; b) 20-70% boron nitride; c) 1-5% siloxane; d) 1-3% surfactant, and e) 10-30% sodium metasilicate pentahydrate Including, 24. The fire and heat insulating composition of claim 23, wherein the components of the composition are combined to total 100 wt%.

32. a) 30-70% water-based acrylic; b) 20-70% boron nitride; c) 1-3% surfactant, and d) 10-30% sodium metasilicate pentahydrate Including, 25. The fire and heat insulating composition of claim 24, wherein the components of the composition are combined to total 100 wt%.

33. a) 30-70% silicone rubber RTV; b) 10-50% boron nitride; c) 20-50% siloxane; d) 1-3% surfactant, and e) 10-30% sodium metasilicate pentahydrate Including, 23. The fire and heat insulating composition of claim 22, wherein the components of the composition are combined to total 100 wt%.

34. 10. The fire and heat insulating composition of claim 1, further comprising 5 to 30 wt. % of a reinforcing material.

35. 35. The fire and heat insulating composition of claim 34, wherein the reinforcing material is selected from one or more of glass / ceramic wool, chopped strands, fibers, or whiskers.

36. A composite sheet comprising an inorganically reinforced layer having applied thereto a layer of the fire and heat insulating composition of claim 1.

37. 37. The composite sheet of claim 36, wherein the inorganic reinforcement layer is in the form of a glass / ceramic mat or fabric.

38. 10. A method of providing fire and thermal protection to a battery cell, comprising coating or covering at least a cathode and / or a vent of the battery cell with the fire and thermal protection coating of claim 1.

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