Battery module having a polyorganosiloxane foam barrier

Abstract

A battery module is provided that includes an array of spatially separated battery cells and a barrier material that contacts adjacent battery cells. The barrier material, which includes a polyorganosiloxane foam, a flame retardant, and hollow ceramic particles, provides flame resistance, compressibility, and thermal insulation.

Description

Technical Field

[0001] The present invention relates to a battery module insulated by a processed polyorganosiloxane foam barrier.

[0002] Rechargeable batteries such as lithium-ion batteries (LiB) are commonly used in various applications including electric vehicles (EV) and grid energy storage systems. LiB has desirable characteristics such as high energy density and stability, but currently its practicality is limited due to safety concerns. First, the failure of a LiB cell can be caused by manufacturing defects, internal short circuits, overheating, overcharging, or mechanical shock. Second, the heat generated from a failed cell can propagate, thereby causing thermal runaway in adjacent cells. The rapid pressure increase resulting from these thermal events increases the risk of fire and explosion.

[0003] Thermal runaway can be mitigated by placing a thermal barrier that provides thermal insulation and flame resistance between the cells in a LiB module. Commonly used thermal barriers such as aerogels, ceramic fibers, and mica boards provide such characteristics, but aerogels and ceramic fibers lack mechanical elasticity, while mica boards lack compressibility. On the other hand, silicone blown foams are suitable for low and medium energy density batteries because they provide appropriate compressibility, but there is a problem that they are insufficient in thermal 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 a barrier that provides thermal insulation, flame resistance, and satisfactory compressibility.

Summary of the Invention

[0004] The present invention provides a battery module comprising a shell including an array of spatially separated battery cells and a barrier material in contact with adjacent battery cells, wherein the barrier material comprises, based on the weight of the barrier material, 35 to 95 weight percent of a polyorganosiloxane foam, 1 to 30 weight percent of a flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume average particle diameter in the range of 25 μm to 300 μm, and the barrier material has a density in the range of 0.10 to 0.90 g / cm 3 to address the needs in the art by providing a battery module having a density in the range of

[0005] The battery module of the present invention provides improved heat resistance and flame retardancy for applications such as lithium-ion batteries.

Brief Description of the Drawings

[0006]

Figure 1

Embodiments for Carrying Out the Invention

[0007] The present invention is a battery module comprising a shell including an array of spatially separated battery cells and a barrier material in contact with adjacent battery cells, wherein the barrier material comprises, based on the weight of the barrier material, 35 to 95 weight percent of a polyorganosiloxane foam, 1 to 30 weight percent of a flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume average particle diameter in the range of 25 μm to 300 μm, and the barrier material has a density in the range of 0.10 to 0.90 g / cm 3 is a battery module having a density in the range of

[0008] The barrier material, which is a foam polyorganosiloxane with heat insulation, flame resistance, and compressibility, can be prepared by modifying the method described in U.S. Patent No. 5,358,975. For example, polydimethylsiloxane (a) functionalized with at least 2, preferably at least 3 Si-H groups is advantageously contacted with one or more hydroxyl-containing compounds (b), which are water, alcohol, diol, polyol, or compounds containing at least 1 silanol group, divinyl-functionalized polydimethylsiloxane (c), a hydrosilylation catalyst, such as a platinum-based catalyst (d), a flame retardant (e), and hollow ceramic particles (f) to form a crosslinked network of a heat-insulating, compressible, and flame-resistant foam material having -Si-CH 2 -CH 2 -Si groups and -Si-O-R- groups (wherein R is H or a structural unit of alcohol, diol, polyol, or silanol, i.e., the reaction product). The total of components (a), (b), and (c) ranges from 35 or 40 weight percent to 80 or 70 weight percent of the polyorganosiloxane foam.

[0009] It may be advantageous to prepare the barrier material using a two-part approach as follows. In a first container, a first portion of divinyl-functionalized polydimethylsiloxane, a first portion of a flame retardant, a hydrosilylation catalyst, a hydroxyl-containing compound or compounds, and a first portion of hollow ceramic particles are blended to form a 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 the flame retardant, polydimethylsiloxane functionalized with at least 3 Si-H groups, and the remaining portion of hollow ceramic particles are blended to form a Part B composition. Then, Part A and B are combined, mixed, and then injected between two release film sheets to form the foam material of the present invention.

[0010] The flame retardant produces CO upon heating 2It is a metal hydroxide, carbonate, hydroxide-carbonate, or hydrate that releases water or both. Examples of flame retardants include Al(OH) 3 , Mg(OH) 2 , Ca(OH) 2 MgCO 3 ·3H 2 O (nesquehonite), Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O (hydromagnesite), MgCa(CO 3 ) 2 (huntite), AlO(OH) (boehmite), NaHCO 3 , and hydrated MgSO 4 (epsomite). The polyorganosiloxane foam material contains a flame retardant from 1 or 2 or 3 weight percent to 30 or 20 or 15 weight percent based on the weight of the foam material.

[0011] The barrier material further comprises hollow, air-filled, or inert gas-filled ceramic particles 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 Al 2 O 3 ), silicon (e.g., crystalline or semi-crystalline SiO 2 ), or calcium (e.g., crystalline or semi-crystalline CaO), or combinations thereof. The crystallinity can be measured by X-ray powder diffraction. As used herein, the term "semi-crystalline" refers to a ceramic material having both amorphous and crystalline regions. The hollow ceramic particles have an average volume particle size from 25μm, or 50μm, or 70μm to 300μm, or 200μm, or 150μm when measured using a dynamic light scattering analyzer such as a Beckman Coulter LS 130 Particle Size Analyzer. The resulting barrier material has a density of 0.10 or 0.15 g / cm 3from 0.90 or 0.50 g / cm 3 to have a density in the range of.

[0012] In another aspect, the present invention provides, based on the weight of the composition, a) 2 to 50 wt% 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 wt% of water, alcohol, diol, polyol, or a compound containing one or more silanol groups, c) 10 to 90 wt% 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 wt% based on the weight of the composition) d) a catalytic amount of a hydrosilylation catalyst, e) 1 to 30 wt% of a flame retardant, f) 1 to 35 wt% of hollow ceramic particles having a volume average particle size in the range of 25 μm to 300 μm.

[0013] FIG. 1 shows an embodiment of the present invention. The battery module includes a shell (20) that houses an array of spatially separated battery cells (30 and 30a), and a barrier material (40) that contacts adjacent battery cells and thereby forms an insulating barrier between the battery cells (30). In this embodiment, the barrier material is disposed between adjacent battery cells (30), and in another embodiment, the barrier material covers the battery cells. The battery module may further include an end plate (50) at the inner edge of the shell that is in direct contact with the battery cells (not shown) or indirectly in contact with the battery cells via a barrier foam (30a). The barrier material can also be inserted into the space between adjacent battery cells and between the cells and the end plate, or a foam precursor can be applied onto the cells and into the space between the battery cells and then cured to form the barrier material.

[0014] Examples of suitable battery cell designs include cylindrical cells, pouch cells, and prismatic cells. Particularly advantageous modules include pouch cells or prismatic cells having a pre-manufactured barrier material in the form of a foam sheet disposed between the cells during assembly. In the case of a cylindrical design, the precursor foam material is typically dispensed into the space separating the cylindrical cells and then cured to form a barrier material surrounding the cylindrical cells.

[0015] The battery modules having the barrier materials described herein have been found to provide the desired properties of heat insulation, flame resistance, and compressibility in the thermal barrier applications of rechargeable batteries.

[0016] In the following examples, ViMe 2 SiO 1 / 2 / (CH 3 ) 3 Si-O 1 / 2 / SiO 4 / 2 The M w and M n of the resin were determined by GPC using a gel permeation chromatography (GPC) column packed with divinylbenzene cross-linked polystyrene beads pore type Mixed-C (Polymer Laboratory) of a size of 5 mm in diameter. THF was used as the mobile phase and detection was performed with a refractive index detector.

[0017] Example 1 - Preparation of a Foamed Organopolysiloxane Article with Ceramic Particles Using a Flacktek Speed Mixer, dimethylvinylsiloxy endblocked polydimethylsiloxane (Polymer 1, 11.3 pbw) having a viscosity of about 40,000 mPas, 1) dimethylvinylsiloxy terminated polydimethylsiloxane having a viscosity of about 1,900 mPa·s and about 0.22 wt% of Vi and 2) 5:40:55 ViMe 2 SiO 1 / 2 :(CH 3 ) 3 Si-O 1 / 2 :SiO 4 / 2 structural unit ratio, M n of 5000, and M wViMe having 2 SiO 1 / 2 / (CH 3 ) 3 Si - O 1 / 2 / SiO 4 / 2 The first component (Part A) was prepared by mixing together a 64:36 w / w blend of a 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, and 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.

[0018] The second composition (Part B) was similarly prepared by mixing together Polymer 1 (8.9 pbw), a polymer resin blend (51 pbw), and Hymod M855 aluminum hydroxide (26.4 pbw). The contents were stirred at 2000 rpm for 30 seconds, and then a linear organohydrogenpolysiloxane having a viscosity of 30 mPa·s and an SiH content of 1.6 wt% (6.7 pbw), and a polydimethyloorganohydrogensiloxane having a viscosity of 5 mPa·s and an SiH content of 0.7 wt% (5.1 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Then, Elminas Spherers HCMS - W150 hollow ceramic particles (20 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0019] Next, equal amounts of Part A and B were mixed, and the mixture was poured between two release film sheets (matte Mylar film). The initial (pre-foam) thickness was controlled to 0.045 inches using a nip roller. The sample was cured at 70 °C for 5 minutes and then at 100 °C for 15 minutes to produce a foam sheet for further testing. (Density = 0.31 g / cm 3 )

[0020] Example 2 - Preparation of a Foamed Organopolysiloxane Article with Ceramic Particles The process for preparing the foamed article of Example 1 was carried out in substantially the same manner, except that Elminas Spheres HCMS THERMO-W75 hollow ceramic particles (average volume particle size of 80 μm, 20 pbw) were used in Parts A and B. (Density = 0.31 g / cm 3 )

[0021] Example 3 - Preparation of a Foamed Organopolysiloxane Article with Ceramic Particles The process for preparing the foamed article of Example 1 was carried out in substantially the same manner, except that Elminas Spheres-W300 hollow ceramic particles (average volume particle size of 180 μm, 20 pbw) were used in Parts A and B. (Density = 0.34 g / cm 3 )

[0022] Thermal Insulation and Combustibility The foam prepared as described in the examples was tested for heat insulation and flammability using a hot plate installed on a hydraulic press. The hot plate was set to 600 °C, and an insulator was placed on the surface. Four thermocouples (Type K) were fixed on an aluminum heat sink (4 inches × 4 inches × 0.47 inches) using Kapton tape. Next, the sample (4 inches × 4 inches) was placed and fixed on the heat sink using Kapton tape. An additional thermocouple (Type K) was 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 the time reached 300 seconds, the pressure was released and the test was terminated. If the temperature of the sample surface was less than 300 °C, it was considered acceptable. If there was no observable flame throughout the test, it was considered to have acceptable flame resistance.

[0023] Hardness The hardness was measured using a Shore 00 durometer. The test specimen was placed on a hard, flat surface. Next, the indenter of the Shore 00 durometer was pressed against the specimen to ensure that the indenter was parallel to the surface. The hardness was read while in firm contact with the specimen. A hardness less than 80 was considered acceptable.

[0024] Compressive force The compressive force was measured using a TA.HDplus texture analyzer equipped with a 100 kg load cell, an aluminum probe with a diameter of 40 mm, and a flat heavy-duty aluminum substrate. A silicone foam sample was circularly cut using a 1-inch diameter die cut and placed between the substrate and the probe. First, the probe was set at the same height as the sample thickness and lowered at a rate of 1 mm / second until the pressure reached the peak point. The sample thickness and pressure were recorded as a compressive force curve. The pressure at 30% of the original sample thickness was recorded. A compressive force less than 500 kPa was considered acceptable.

[0025] Density of the foam The foam density was calculated based on the average thickness and weight of two 1-inch diameter foam samples.

[0026] The properties of the ceramic-filled organopolysiloxane article were compared with a commercially available organopolysiloxane article (COHRlastic Silicone Foam, available from Stockwell Elastomerics) that has a structure similar to the foam of the examples except that it does not contain hollow ceramic particles.

[0027] Table 1 is an overview of the performance characteristics of the foams of Examples 1 to 3 and the commercially available comparative foams. The density was measured in g / cm 3 . The hardness was measured in Shore 00 units. The compression force (force) was measured in kPa at 30% compression. The temperature at 600 °C (T after 300 seconds) refers to the sample surface temperature after 300 seconds, and the flammability refers to the observability of the flame during the heat insulation test.

[0028]

Table 1

[0029] Table 1 shows that all the barrier materials used in the battery modules of the present invention passed all the tests, while the commercially available examples failed the heat insulation test. Surprisingly, it was found that the barrier material having hollow ceramic particles can lower the surface temperature in 300 seconds without adversely affecting other important properties of the foam. Furthermore, it was found that a hollow ceramic particle size in the range of 50 μm to 150 μm is particularly effective in lowering the surface temperature.

Claims

1. A battery module comprising a shell containing an array of spatially separated battery cells and a barrier material in contact with adjacent battery cells, wherein the barrier material comprises, based on the weight of the barrier material, 35 to 95 weight percent of a polyorganosiloxane foam, 1 to 30 weight percent of a flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume average particle diameter in the range of 25 μm to 300 μm, and the barrier material has a density in the range of 0.10 to 0.90 g / cm ３ of the battery module.

2. The battery module according to claim 1, wherein the barrier material contains 50 to 80% by weight of the polyorganosiloxane foam and 2 to 20% by weight of the flame retardant.

3. The flame retardant is Al(OH) ３ , Mg(OH) ２ , MgCO ３ ·3H ２ O, or Mg ５ (CO ３ ) ４ (OH) ２ ·4H ２ O, MgCa(CO ３ ) ２ , AlO(OH), NaHCO ３ , or hydrated MgSO ４ , or a combination thereof, the battery module according to claim 2.

4. The battery module according to any one of claims 1 to 3, wherein the barrier material has a density in the range of 0.15 to 0.50 g / cm ３ .

5. The battery module according to claim 4, wherein the hollow ceramic particles have an average volume particle diameter by dynamic light scattering in the range of 25 μm to 200 μm.

6. The battery module according to claim 4, wherein the hollow ceramic particles have an average volume particle diameter by dynamic light scattering in the range of 50 μm to 150 μm.

7. The hollow ceramic particles are crystalline or semi-crystalline Al ２ O ３ particles, crystalline or semi-crystalline SiO ２ particles, or crystalline or semi-crystalline CaO particles, or crystalline or semi-crystalline Al / Mg / Ca silicate, the battery module according to any one of claims 5 or 6.

8. The battery module according to claim 1, comprising a pouch or prismatic battery cell and a sheet of the barrier material disposed between adjacent battery cells.

9. The battery module according to claim 1, comprising a cylindrical battery cell, wherein the barrier material surrounds the cylindrical battery cell.

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