Organopolysiloxane composition containing ceramic microspheres

Abstract

A composition comprising a reactive polysiloxane and a hydroxyl-containing precursor, a flame retardant, and micron-sized hollow ceramic particles, the composition being useful in the preparation of an insulating, compressible, and flame resistant foam material useful for providing thermal insulation, flame resistance, and compressibility for applications such as lithium ion batteries.

Description

[Technical Field]

[0001] The present invention relates to an organopolysiloxane composition containing micron-sized ceramic particles. [Background technology]

[0002] Rechargeable lithium-ion batteries (LiBs) are commonly used in a variety of applications, including electric vehicles (EVs) and grid energy storage systems. While LiBs possess desirable characteristics such as high energy density and stability, their practical use is currently limited by safety concerns. Firstly, LiB cell failures can be caused by manufacturing defects, internal short circuits, overheating, overcharging, or mechanical shocks. Secondly, heat generated from a failed cell can propagate, potentially causing thermal runaway in adjacent cells. The rapid pressure increases resulting from these thermal events increase the risk of fire and explosion.

[0003] Thermal runaway can be mitigated by placing thermal barriers that provide insulation and flame resistance between cells in a LiB module. Commonly used thermal barriers such as aerogel, ceramic fiber, and mica board offer such properties, but aerogel and ceramic fiber have poor mechanical elasticity, while mica board has poor compressibility. On the other hand, blown silicone foam provides adequate compressibility and is suitable for low and medium energy density batteries, but it has the problem of insufficient insulation to prevent thermal runaway in very high energy density battery packs. Therefore, in the field of thermal barriers for rechargeable batteries, it is desirable to create barriers that provide insulation, flame resistance, and satisfactory compressibility. [Overview of the Initiative]

[0004] The present invention addresses the needs in the art by providing a composition comprising, based on the weight of the composition, a) 2 to 50 weight percent of a polysiloxane functionalized with at least two Si-H groups and having a degree of polymerization in the range of 5 to 1000; b) 1 to 50 weight percent of water, alcohol, diol, polyol, or a compound containing one or more silanol groups; c) 10 to 90 weight percent of a polysiloxane functionalized with at least one ethylenically unsaturated group and having a degree of polymerization in the range of 20 to 2000 (the total concentration of components a, b, and c is in the range of 35 to 95 weight percent based on the weight of the composition); d) a catalytic amount of a hydrosilylation catalyst; e) 1 to 30 weight percent of a flame retardant; and f) 1 to 35 weight percent of hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm.

[0005] The composition of the present invention is useful for providing a foamed material that can be used as a compressible, heat-insulating, and flame-resistant spacer in lithium-ion batteries. [Modes for carrying out the invention]

[0006] The present invention provides a composition comprising, based on the weight of the composition, a) 2 to 50 weight percent of a polysiloxane functionalized with at least two Si-H groups and having a degree of polymerization in the range of 5 to 1000; b) 1 to 50 weight percent of water, alcohol, diol, polyol, or a compound containing one or more silanol groups; c) 10 to 90 weight percent of a polysiloxane functionalized with at least one ethylenically unsaturated group and having a degree of polymerization in the range of 20 to 2000 (the total concentration of components a, b, and c is in the range of 35 to 95 weight percent based on the weight of the composition); d) a catalytic amount of a hydrosilylation catalyst; e) 1 to 30 weight percent of a flame retardant; and f) 1 to 35 weight percent of hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm.

[0007] Polysiloxane (a) functionalized with at least two, preferably at least three, Si-H groups has a degree of polymerization in the range of 5 to 1000 or ~500 or ~200. Hydroxyl-containing compound (b) is preferably benzyl alcohol or C2-C8 alkyldiol. Polysiloxane (c) functionalized with at least one, preferably at least two, ethylenically unsaturated groups has a degree of polymerization in the range of 20 or 100 or 200 or 300 to 2000 or 1500 or 1000. The total weight percentages of components a, b, and c range from 35 or 50 to 95 weight percent based on the weight of the composition.

[0008] Polysiloxanes functionalized with at least one ethylenically unsaturated group are preferably functionalized with two C2-C8 alkenyl groups, more preferably with two vinyl or two allyl groups. The polysiloxane functionalized with at least one ethylenically unsaturated group is most preferably polydimethylsiloxane functionalized with two vinyl groups. Polydimethylsiloxane functionalized with two vinyl groups is advantageously designed to have a viscosity in the range of 10,000 to 50,000 mPa·s. This viscosity is conveniently achieved by combining divinyl-functionalized polydimethylsiloxanes of different degrees of polymerization, i.e., by divinyl-functionalized polydimethylsiloxanes with a bimodal distribution.

[0009] The hydrosilylation catalyst is preferably a platinum-based catalyst such as chloroplatinic acid, and is used in catalytic amounts, typically in the range of 0.5 ppm to 200 ppm Pt based on the weight of the composition.

[0010] The composition also contains a flame retardant ranging from 1, 2, or 3 weight percent to 30, 20, or 15 weight percent, the flame retardant being a metal hydroxide, carbonate, hydroxide-carbonate, or hydrate that releases CO2, water, or both upon heating. Examples of flame retardants include Al(OH)3, Mg(OH)2, Ca(OH)2MgCO3·3H2O (neskehonite), Mg5(CO3)4(OH)2·4H2O (hydromagnesite), MgCa(CO3)2 (huntite), AlO(OH) (boehmite), NaHCO3, and hydrated MgSO4 (epsomite).

[0011] The composition further comprises hollow, air-filled, or inert gas-filled ceramic particles ranging from 1 or 5 or 10 weight percent to 35 or 30-25 weight percent. As used herein, “ceramic” refers to crystalline or semi-crystalline inorganic oxides, nitrides, carbides, oxynitrides, or oxycarbides of metals such as aluminum (e.g., crystalline or semi-crystalline Al2O3), silicon (e.g., crystalline or semi-crystalline SiO2), or calcium (e.g., crystalline or semi-crystalline CaO), or combinations thereof. Crystallinity can be measured by X-ray powder diffraction. As used herein, the term “semi-crystalline” refers to ceramic materials having amorphous and crystalline regions. The hollow ceramic particles have average volume particle sizes ranging from 25 μm, or 50 μm, or 70 μm-300 μm, or up to 200 μm, or up to 150 μm, as measured using a dynamic light scattering analyzer such as a Beckman Coulter LS 130 Particle Size Analyzer. The resulting article has a concentration of 0.10 or 0.15 g / cm³. 3 ~0.90 or 0.50 g / cm³ 3 It has a density in the range up to [a certain value].

[0012] The composition is useful for preparing polyorganosiloxane foam articles, for example, those substantially described in U.S. Patent No. 5,358,975. Advantageously, a polysiloxane functionalized with at least three Si-H groups is contacted with a) an alcohol, diol, polyol, or silanol, and b) a divinyl-functionalized polydimethylsiloxane in the presence of a platinum-based catalyst to form a crosslinking network of organopolysiloxanes having -Si-CH2-CH2-Si- and -Si-OR groups (wherein R is a structural unit (i.e., a reaction product) of the alcohol, diol, polyol, or silanol).

[0013] It may be advantageous to prepare the foaming material using the following two-part approach. In a first container, a first portion of divinyl-functionalized polydimethylsiloxane, a first portion of a flame retardant, a platinum-based catalyst, a hydroxyl-containing compound or multiple compounds, and a first portion of hollow ceramic particles are blended to form Part A composition. In a second container, the remaining portion of divinyl-functionalized polydimethylsiloxane, a polymer resin blend which is a mixture of divinyl-functionalized polydimethylsiloxane and a crosslinked organopolysiloxane resin, the remaining portion of a flame retardant, a polysiloxane functionalized with at least three Si-H groups, and the remaining portion of hollow ceramic particles are blended to form Part B composition. Parts A and B are then combined and mixed, and then injected between two release film sheets to form the foaming material of the present invention.

[0014] Therefore, in another aspect, the present invention relates to a thermally insulating, compressible, and flame-retardant foamed material comprising, based on the weight of the foamed material, 35 to 95 weight percent of polyorganosiloxane foam, 1 to 30 weight percent of flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm, with a concentration of 0.10 to 0.90 g / cm³. 3 It is a foamed material having a density in the range of [this range].

[0015] In yet another aspect, the present invention provides a battery module comprising a housing containing an array of spatially separated battery cells, and a polyorganosiloxane foam material in contact with adjacent battery cells. The polyorganosiloxane foam can be brought into contact with the battery cells by filling the spaces between adjacent battery cells with the foam and / or coating the battery cells with the foam. The battery module may further comprise an end plate at an inner edge of the housing that is in direct or indirect contact with the battery cell closest to the edge. The foamed material may alternatively be inserted into cavities between adjacent battery cells and between the cells and the end plate, or a foam precursor may be applied onto the cells and into the cavities and then cured to form the foamed material.

[0016] It has been found that the foamed material of the present invention provides the desired properties of heat insulation, flame resistance and compressibility in LiB thermal barrier applications.

[0017] In the following examples, ViMe2SiO 1 / 2 / (CH3)3Si-O 1 / 2 / SiO 4 / 2 M of the resin w and M n were determined by gel permeation chromatography using a GPC column packed with 5 mm diameter divinylbenzene crosslinked polystyrene beads of pore type Mixed-C (Polymer Laboratory). THF was used as the mobile phase, and detection was performed with a refractive index detector.

[0018] Example 1 - Preparation of expanded organopolysiloxane article with ceramic particles Using a Flacktek Speed Mixer, dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 40,000 mPas (Polymer 1, 11.3 parts by weight), 1) dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 1,900 mPa·s and a Vi content of about 0.22% by weight, and 2) ViMe2SiO of 5:40:55 1 / 2 :(CH3)3Si-O 1 / 2 :SiO 4 / 2 structural unit ratio, M of 5000 n , and M of 21,400w ViMe2SiO 1 / 2 / (CH3)3Si-O 1 / 2 / SiO 4 / 2 The first component (Part A) was prepared by mixing a 64:36 w / w blend with resin (polymer-resin blend, 64.9 pbw) and Micral 855 aluminum hydroxide (15.2 pbw). The contents were stirred at 2000 rpm for 30 seconds, then a complex of Pt(0) and divinyltetramethyldisiloxane (0.93 pbw, 0.62 wt% Pt), 1,4-butanediol (2.6 pbw), and benzyl alcohol (3.3 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Finally, Elminas Spheres HCMS-W150 hollow ceramic particles (average volume particle size of 100 μm; 20 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0019] The contents were stirred at 2000 rpm for 30 seconds. Then, a complex of chloroplatinic acid and divinyltetramethyldisiloxane (0.93 pbw, 0.62 wt% Pt), 1,4-butanediol (2.6 pbw), and benzyl alcohol (3.3 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Finally, Elminas Spheres HCMS-W150 hollow ceramic particles (average volume particle size of 100 μm; 20 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0020] A second composition (Part B) was similarly prepared by mixing together Polymer 1 (8.9 parts by weight), a polymer resin blend (51 parts by weight), and Hymod M855 aluminum hydroxide (26.4 parts by weight). The contents were stirred at 2000 rpm for 30 seconds, after which linear organohydrogenpolysiloxane having a viscosity of 30 mPa·s and an SiH content of 1.6 wt% (6.7 parts by weight), and polydimethylorganohydrogensiloxane having a viscosity of 5 mPa·s and an SiH content of 0.7 wt% (5.1 parts by weight) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Then, Elminas Spheres HCMS-W150 hollow ceramic particles (20 parts by weight) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0021] Then, equal amounts of Part A and Part B were mixed, and the mixture was poured between two release film sheets (matted Mylar film). The initial (pre-foaming) thickness was controlled to 0.045 inches using a nip roller. The sample was cured at 70°C for 5 minutes, then at 100°C for 15 minutes, to prepare a foam sheet for use in further tests. (density=0.31g / cm 3 )

[0022] Example 2 - Preparation of Foamed Organopolysiloxane Article Having Ceramic Particles Substantially the same method as the process for preparing the foamed article of Example 1 was carried out, except that Elminas Spheres HCMS THERMO-W75 hollow ceramic particles (average volume particle diameter of 80 μm, 20 parts by weight) were used in Part A and Part B. (density=0.31g / cm 3 )

[0023] Example 3 - Preparation of Foamed Organopolysiloxane Article Having Ceramic Particles Substantially the same method as the process for preparing the foamed article of Example 1 was carried out, except that Elminas Spheres-W300 hollow ceramic particles (average volume particle diameter of 180 μm, 20 parts by weight) were used in Part A and Part B. (density=0.34g / cm 3 )

[0024] Thermal insulation and resistance to infection The foam prepared as described in the examples was tested for thermal insulation and flammability using a hot plate mounted on a hydraulic press. The hot plate was set to 600°C and an insulator was placed on its surface. Four K-type thermocouples were secured to an aluminum heat sink (4 inches × 4 inches × 0.47 inches) using Kapton tape. The sample (4 inches × 4 inches) was then placed and secured to the heat sink using Kapton tape. Additional K-type thermocouples were attached to the sample surface using Kapton tape. The insulator was removed from the hot surface, and the sample attached to the heat sink was quickly placed on the hot surface with the sample surface facing the hot plate surface and the Al heat sink facing the opposite side. The pressure was rapidly increased to 355 kPa. The interface temperature between the hot plate surface and the sample surface, and the interface temperature between the sample surface and the heat sink were recorded using a data logger. When 300 seconds had passed, the pressure was released and the test was terminated. A sample surface temperature below 300°C was considered acceptable. If no flames are observed throughout the entire test, the flame resistance is considered acceptable.

[0025] hardness Hardness was measured using a Shore 00 durometer. The test specimen was placed on a hard, flat surface. The indenter of the Shore 00 durometer was then pressed against the specimen, ensuring that it was parallel to the surface. The hardness was read while the indenter was firmly in contact with the specimen. A hardness of less than 80 was considered acceptable.

[0026] Compression force Compressive force was measured using a TA.HDplus texture analyzer equipped with a 100 kg load cell, a 40 mm diameter aluminum probe, and a flat heavy-duty aluminum substrate. A silicone foam sample was cut into a circle using a 1-inch diameter die cutter and placed between the substrate and the probe. The probe was initially set to the same height as the sample thickness and lowered at a rate of 1 mm / second until the pressure reached its peak. The sample thickness and pressure were recorded as a compressive force curve. The pressure at 30% of the original sample thickness was recorded. Compressive forces below 500 kPa were considered acceptable.

[0027] density of foam The foam density was calculated based on the average thickness and weight of two 1-inch diameter foam samples.

[0028] The properties of the ceramic-filled organopolysiloxane article were compared with a commercially available organopolysiloxane article (COHRlastic Silicone Foam, available from Stockwell Elastomerics) that is structurally similar to the foam in the example, except that it does not contain hollow ceramic particles.

[0029] Table 1 summarizes the performance characteristics of the foams from Examples 1-3 and a commercially available comparative foam. Density is g / cm³. 3 The measurements were taken using the following method. Hardness was measured in Shore 00 units. Compressive force (force) was measured in kPa at 30% compression. The temperature at 600°C (T after 300 seconds) refers to the surface temperature of the sample after 300 seconds, and flammability refers to the observability of the flame during the adiabatic test.

[0030] [Table 1]

[0031] Table 1 shows that the foam of the present invention passes all tests, while commercially available examples fail the thermal insulation test. Surprisingly, hollow ceramic particles were found to reduce the surface temperature in 300 seconds without adversely affecting other important properties of the foam. Furthermore, hollow ceramic particle sizes in the range of 50 μm to 150 μm were found to be particularly effective in reducing the surface temperature. The present invention encompasses the following aspects. [1] A composition, wherein based on the weight of the composition, a) A polysiloxane functionalized with at least two Si-H groups in an amount of 2 to 50 weight percent and having a degree of polymerization in the range of 5 to 1000, b) 1 to 50 weight percent of water, alcohol, diol, polyol, or a compound containing one or more silanol groups, c) A polysiloxane functionalized with at least one ethylenically unsaturated group in an amount of 10-90% by weight, and having a degree of polymerization in the range of 20-2000, (the total concentration of components a, b, and c is in the range of 35-95% by weight based on the weight of the composition) d) A catalytic amount of hydrosilylation catalyst, e) 1 to 30 weight percent of flame retardant, f) Hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm, in an amount of 1 to 35 weight percent, A composition containing the following: [2] The composition according to Invention 1, wherein the polysiloxane functionalized with at least two Si-H groups is functionalized with at least three Si-H groups, the total concentration of components a, b, and c is in the range of 50 to 80 percent based on the weight of the composition, and the concentration of the flame retardant is in the range of 2 to 20 percent by weight based on the weight of the composition. [3] The composition according to Invention 2, wherein the polysiloxane functionalized with at least one ethylenically unsaturated group is a divinyl-functionalized polydimethylsiloxane having a degree of polymerization in the range of 100 to 1000. [4] The aforementioned flame retardant is Al(OH) 3 Mg(OH) 2 MgCO 3 ·3H 2 O, Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O, MgCa(CO) 3 ) 2 AlO(OH), NaHCO 3 , and hydrated MgSO 4 The composition according to Invention 3, wherein the composition is one or more flame retardants selected from the group consisting of the following. [5] The composition according to any one of Inventions 1 to 4, wherein the hollow ceramic particles have an average volume particle size in the range of 25 μm to 200 μm due to dynamic light scattering. [6] The composition according to any one of Inventions 1 to 4, wherein the hollow ceramic particles have an average volume particle size in the range of 50 μm to 150 μm due to dynamic light scattering. [7] The hollow ceramic particles are crystalline or semicrystalline Al 2 O 3 Particles, crystalline or semi-crystalline SiO 2 The composition according to invention 5 or 6, which is a particle, or a crystalline or semi-crystalline CaO particle. [8] The composition according to Invention 3, wherein the divinyl-functionalized polydimethylsiloxane is a divinyl-functionalized polydimethylsiloxane having a bimodal distribution with a composite viscosity in the range of 10,000 to 50,000 mPa·s.

Claims

1. A composition for use as a spacer in a lithium-ion battery, wherein, based on the weight of the composition, a) A polysiloxane functionalized with at least two Si-H groups in an amount of 2 to 50 weight percent and having a degree of polymerization in the range of 5 to 1000, b) 1 to 50 weight percent of water, alcohol, diol, polyol, or a compound containing one or more silanol groups, c) A polysiloxane functionalized with at least one ethylenically unsaturated group in an amount of 10 to 90 percent by weight, and having a degree of polymerization in the range of 20 to 2000 (the total concentration of components a, b, and c is in the range of 35 to 95 percent by weight based on the weight of the composition). d) A catalytic amount of hydrosilylation catalyst, e) 1 to 30 weight percent of flame retardant, f) Hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm, in an amount of 1 to 35 weight percent, A composition containing the following:

2. The composition according to claim 1, wherein the polysiloxane functionalized with at least two Si-H groups is functionalized with at least three Si-H groups, the total concentration of components a, b, and c is in the range of 50 to 80 weight percent based on the weight of the composition, and the concentration of the flame retardant is in the range of 2 to 20 weight percent based on the weight of the composition.

3. The composition according to claim 2, wherein the polysiloxane functionalized with at least one ethylenically unsaturated group is a divinyl-functionalized polydimethylsiloxane having a degree of polymerization in the range of 100 to 1000.

4. The flame retardant is Al(OH) ３ , Mg(OH) ２ , MgCO ３ ·3H ２ O, Mg ５ (CO ３ ) ４ (OH) ２ ·4H ２ O, MgCa(CO ３ ) ２ , AlO(OH), NaHCO ３ , and hydrated MgSO ４ The composition according to claim 3, which is one or more flame retardants selected from the group consisting of:

5. The composition according to claim 1, wherein the hollow ceramic particles have a volume-average particle size in the range of 25 μm to 200 μm due to dynamic light scattering.

6. The composition according to claim 1, wherein the hollow ceramic particles have a volume-average particle size in the range of 50 μm to 150 μm due to dynamic light scattering.

7. The hollow ceramic particles are crystalline or semicrystalline Al ２ O ３ Particles, crystalline or semi-crystalline SiO ２ The composition according to claim 5 or 6, wherein the composition is particles, or crystalline or semicrystalline CaO particles.

8. The composition according to claim 3, wherein the divinyl-functionalized polydimethylsiloxane is a divinyl-functionalized polydimethylsiloxane having a bimodal distribution with a composite viscosity in the range of 10,000 to 50,000 mPa·s.

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