Thermal barrier for use in a power module assembly with at least one battery cell

Abstract

A thermal barrier (10) for use in a power module assembly (12) having at least one battery cell (14), the thermal barrier (10) comprising:at least one compressible element (30) having one or more pockets (40), the at least one compressible element (30) defining a first side (32) and a second side (34);a first layer (36) and a second layer (38) disposed adjacent to the at least one compressible element (30), the first layer (36) being disposed on the first side (32) and the second layer (38) being disposed on the second side (34);one or more phase change materials (42, 342) configured to be deposited into the one or more pockets (40);andwherein the one or more phase-change materials (42, 342) are configured to undergo an endothermic phase-change reaction when a temperature of the at least one battery cell (14) is at or above an activation temperature;wherein:the first layer (36) comprises an outer first layer (233) and an inner first layer (235);at least one fluid (F) is released during the endothermic phase-change reaction;the inner first layer (233) is configured to absorb the fluid (F) generated in the endothermic phase-change reaction while simultaneously creating a cooling effect;andthe outer first layer (235) is configured to at least partially reflect radiant heat;andwherein:the one or more pockets (40) include at least one through-hole (140) extending from the first side (32) to the second side (34) of the at least one compressible element (30);orthe one or more pockets (40) comprise a first set of blind holes (239) extending along the first side (32) and a second set of blind holes (241) extending along the second side (34) of the at least one compressible element (30);

Description

Technical FieldThe present disclosure relates to a power module assembly, a thermal barrier for use in the power module assembly, and a corresponding method of forming the thermal barrier.IntroductionThe use of all-electric vehicles and hybrid vehicles, such as battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and fuel cell hybrid electric vehicles, has increased greatly in recent years. Fully and partially electric vehicles typically include a rechargeable energy storage component, such as a high voltage battery. The performance and life of the rechargeable batteries can be improved by controlling exposure to too high temperatures, such as a thermal runaway situation.DE 10 2019 103 619 A1 describes a heat transport device for transferring heat, comprising an upper housing part, a lower housing part for receiving a foam element, wherein the upper and lower housing parts are connectable to each other such that a first interior space is defined and enclosed by the upper and lower housing parts, the foam element arranged in the first interior space, and a phase change material arranged in the first interior space. The phase change material is at least partially receivable by the foam member. The heat transport device is designed to transfer heat by means of circulation of the phase transition material.US 2017 / 0 214 103 A1 describes lithium ion batteries which contain materials which have advantageous endothermic functions which contribute to the safety and stability of the batteries. The endothermic materials may include a ceramic matrix containing an inorganic gas generating endothermic material. When the temperature of the lithium ion battery rises above a certain level, the endothermic materials serve to perform one or more functions to prevent and / or minimize the risk of thermal runaway, e.g., (i) thermal insulation (especially at high temperatures); (ii) energy absorption; (iii) venting gases generated wholly or partially by endothermic reaction(s) in conjunction with the endothermic materials; (iv) increasing the total pressure within the battery structure; (v) removing the absorbed heat from the battery system by venting gases generated during the endothermic reaction(s) in conjunction with the endothermic materials; and / or (vi) diluting toxic gases (if present) and safely expelling them from the battery system.US 6 004 662 A describes a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material may be adapted to heat or cool the body or serve as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an outer thermal barrier layer and / or an inner thermal control layer to control the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for the evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) thermally conductive paths within the thermal balancing material, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for rapid regeneration of thermal storage capacity for re-use of the material. Applications of the composite materials are also described which make use of the thermal properties of the composite materials. Examples described include a diving suit, ski boot liners, thermosocks, gloves and a face mask for cold weather activities, as well as a metabolic heating or cooling blanket useful for treating supercooling patients or fever patients in a medical environment and for therapeutically heating or cooling orthopedic joint supports.US 2010 / 0 304 078 A1 describes fire-resistant systems, methods and devices. In one example, a fire resistant system includes a fire resistant panel and a protected material bonded to the fire resistant panel. The fire resistant plate comprises a passive layer and a back layer. The passive layer is made of a phyllosilicate material. The back layer is made of an inorganic material and may be bonded to the passive layer. Optionally, the refractory plate may include a secondary layer comprising a functional material, wherein the functional material comprises one of a phase change material and an endothermic material.DESCRIPTION OF THE INVENTIONThe invention is defined by the claims.Included are a power module assembly, a thermal barrier for use in the power module assembly, and a corresponding method of forming the thermal barrier. The power module assembly includes at least one battery cell. The thermal barrier according to the invention comprises at least one compressible element ("at least one" is omitted below) with one or more pockets. A first layer and a second layer are disposed adjacent the compressible member on a first side and a second side, respectively. The thermal barrier includes one or more phase change materials configured to be deposited in the one or more pockets. The phase change materials are configured to undergo an endothermic phase change reaction when a temperature is at or above an activation temperature. The first layer includes an outer first layer and an inner first layer. The inner first layer may be configured to absorb the fluid generated in the endothermic phase change reaction and simultaneously generate a cooling effect. The outer first layer is configured to at least partially reflect radiant heat. The one or more pockets include either at least one through hole extending from the first side to the second side of the at least one compressible element, or the one or more pockets include a first set of blind holes extending along the first side and a second set of blind holes extending along the second side of the at least one compressible element.In one example, the compressible member is made of foam. The first layer and the second layer may be configured to at least partially reflect radiant heat. The phase change materials may include at least one or a combination of aluminum bicarbonate, ammonium bicarbonate, beryllium bicarbonate, calcium bicarbonate, lithium bicarbonate, magnesium bicarbonate, potassium bicarbonate, and sodium bicarbonate.The phase change materials may be selected such that at least one fluid having flame extinguishing properties is released during the endothermic phase change reaction. In one example, the phase change materials include sodium bicarbonate and the released fluid includes carbon dioxide gas.If blind holes are present, the first group of blind holes may be offset relative to the second group of blind holes. In a third example, the compressible member is comprised of a polymeric base such that the one or more phase change materials are distributed within the polymeric base.In another example, the phase change materials include a first material characterized by a first activation temperature in a first range and a second material characterized by a second activation temperature in a second range. The method may include positioning the thermal barrier proximate the battery cell. The thermal barrier is configured to mitigate thermal propagation within the power module assembly in an elevated temperature situation. In addition, the thermal barrier may be configured to oppose cell expansion of the battery cell during regular operation.The above features and advantages, as well as other features and advantages of the present disclosure, will be readily apparent from the following detailed description of the preferred embodiments for carrying out the disclosure when taken in conjunction with the accompanying drawings.Brief Description of the DrawingsFIG. 1 is a schematic perspective, partially exploded, fragmentary view of a power module assembly having a thermal barrier; FIG. 2 is an exploded schematic view of the thermal barrier of FIG. 1 ; FIG. 3 is a schematic flow diagram of a method of forming the thermal barrier of FIG. 1 ; FIG. 4A is a schematic cross-section through the thermal barrier of FIG. 1, according to a first example; FIG. 4B is a schematic cross-sectional view of the thermal barrier of FIG. 1, in accordance with a second example; and FIG. 4C is a schematic cross-section through the thermal barrier of FIG. 1, in accordance with a third example.Detailed DescriptionReferring to the figures, wherein like reference numerals refer to like components, FIG. 1 schematically illustrates a thermal barrier 10 employed in a power module assembly 12. The power module assembly 12 may include a plurality of the thermal barriers 10, such as a first thermal barrier 10A, a second thermal barrier 10B, and a third thermal barrier 10C, illustrated in FIG. 1. The power module assembly 12 may be used as an energy storage unit for a fully electric or partially electric mobile platform, such as, but not limited to, a passenger car, a sport utility vehicle, a light truck, a heavy truck, an ATV, a minivan, a bus, a transit vehicle, a bicycle, a robot, an agricultural implement, sports equipment, a boat, an aircraft, a train, or other transport device. The power module assembly 12 may take many different forms and may include multiple and / or alternative components and devices.Referring to FIG. 1, the power module assembly 12 includes at least one battery cell 14 ("at least one" is omitted below). The battery cell 14 may be a can-type lithium ion battery cell or a pouch-type cell, including, but not limited to, lithium manganese, lithium ion phosphate, lithium cobalt, and lithium nickel-based cells. Each battery cell 14 may include one or more corresponding cell tabs 16 extending from their respective edges. Referring to FIG. 1, multiple cells of the battery cell 14 may be stacked or arranged in corresponding modules 18 and connected in series or in parallel. The power module assembly 12 may be supported or supported with a support member 20, which may be a frame and / or a cover plate.The thermal barrier 10 is configured to mitigate heat spread within the power module assembly 12 in a situation where elevated temperatures may have arisen from one or more of the battery cells 14. In addition, the thermal barrier 10 is configured to resist cell expansion of the battery cell 14 during regular operation. The thermal barrier 10 is configured to interface with the battery cell 14 and to be positioned between individual cells of the battery cell 14 and / or between stacks of the battery cell 14 disposed in the respective modules 18. Referring to FIG. 1, the first thermal barrier 10A is positioned between a first battery cell 14A and a second battery cell 14B. The second thermal barrier 10B is disposed between a first module 18A and a second module 18B.Referring now to FIG. 2, a schematic exploded view of the thermal barrier 10 is shown. The thermal barrier 10 includes at least one compressible member 30 defining a first side 32 and a second side 34. The compressible member 30 is configured to absorb the cell expansion of the battery cell 14 as desired and at the same time serve as a thermal insulator. In one example, the compressible member 30 is made of a foam material. In another example, the compressible member 30 is made of a polymer containing at least one of, or a combination of, polysiloxane, polyurethane, and polyacrylate. The compressible member 30 may be selected from an inert material so that it does not react with the phase change materials 42. A method 100 of forming the thermal barrier 10 is described below with reference to FIG. 3.Referring to FIG. 2, a first layer 36 and a second layer 38 are disposed adjacent the first side 32 and the second side 34 of the compressible member 30, respectively. The first layer 36 and the second layer 38 may be configured to at least partially or fully encapsulate the compressible element 30. The first layer 36 and the second layer 38 may be coextensive with the compressible member 30. The first layer 36 and the second layer 38 may be configured as heat reflective layers configured to at least partially reflect radiant heat energy and convective heat energy emanating from the battery cell 14. In one example, the first layer 36 and the second layer 38 are made of aluminum or an aluminum alloy.Referring to FIG. 2, the thermal barrier 10 includes one or more pockets 40 in which one or more phase change materials 42 ("one or more" omitted hereafter) are configured to be deposited or deposited therein. The pockets 40 filled with the phase change materials 42 may be configured to remain in place and prevent undesirable secondary reactions. The phase change materials 42 may be uniformly dispersed by the compressible member 30. The phase change materials 42 are configured to undergo an endothermic phase change reaction when the temperature of the battery cell 14 is at or above an activation temperature. In other words, the endothermic phase change reaction enables heat absorption from the power module assembly 12 when the temperature is at or above the activation temperature.The phase change materials 42 may be used in solid form, as powders, and / or as shaped compacts, with the shape being varied depending on the application. Referring to FIG. 2, the endothermic phase change reaction may produce a fluid F, which may contain a liquid and / or a gas. The phase change materials 42 may be selected such that the released fluid F has flame extinguishing properties. In one example, the phase change materials 42 include a bicarbonate salt. For example, the phase change materials 42 may contain sodium bicarbonate, wherein the endothermic phase change reaction is represented as follows: 2NaHCO 3 →Na 2 CO 3+ H 2 O+CO 2In the case of sodium bicarbonate, the products of thermal decomposition are solid sodium carbonate, H 2 O (which may be liquid or gaseous depending on temperature) and carbon dioxide gas. The carbon dioxide produced has flame extinguishing properties. In another example, the phase change materials 42 include at least one or a combination of: aluminum bicarbonate, ammonium bicarbonate, beryllium bicarbonate, calcium bicarbonate, lithium bicarbonate, magnesium bicarbonate, potassium bicarbonate, and sodium bicarbonate. The phase change materials 42 may include carbonates, such as calcium carbonate, that decomposes at about 840 Celsius. The phase change materials 42 may include chemicals with hydrates that release the water of hydration at certain temperatures.The phase change materials 42 may include a first material characterized by a first activation temperature in a first range and a second material characterized by a second activation temperature in a second range, the first range being different than the second range. This provides a technical advantage for increasing the dynamic response range. In one example, the first material and the second material may be selected such that the first activation temperature is between about 80 and 90 Celsius and the second activation temperature is between about 130 and 140 Celsius. The first region may at least partially overlap with the second region.In the example shown in FIG. 2, the pockets 40 are configured unitarily and define a plurality of evenly spaced circles. However, it should be understood that the size, individual shape, and spacings of the pockets 40 may be varied depending on the application. Three example structures for the thermal barrier 10 are illustrated in FIGS. 4A, 4B, and 4C. Referring to FIG. 4A, the pockets 40 may include at least one through hole 140 extending from the first side 32 to the second side 34 of the compressible member 30, in accordance with a first example. Alternatively, the pockets 40 may be formed to a certain depth without breaking through to the other side. Referring to FIG. 4B, the pockets 40 according to a second example include a first set of blind holes 239 extending along the first side 32 and a second set of blind holes 241 extending along the second side 34 of the compressible member 30. The distance within and the respective depths of the first set of blind holes 239 and the second set of blind holes 241 may be varied. As shown in FIG. 4B, the first set of blind holes 239 may be offset from the second set of blind holes 241, i.e., arranged alternately in a direction parallel to the first layer 36.Referring to FIG. 4C, in accordance with a third example, the compressible member 30 is comprised of a polymeric base 330. The phase change materials 342 may be impregnated in the pockets 40 and distributed or interspersed internally within the polymeric base330. The polymeric base 330 may include at least one of or a combination of polysiloxane, polyurethane, and polyacrylate. It is understood that the features described in each example may be combined with one or more other features from other examples. For example, the outer first layer 233 and the inner first layer 235 shown in FIG. 4B may be combined with the through hole 140 shown in FIG. 4A.The first layer 36 and the second layer 38 may each be formed as a composite of multiple layers. Referring to FIG. 4B, the first layer 36 may be comprised of an outer first layer 233 and an inner first layer 235. The second layer 38 may include an outer second layer 237 and an inner second layer 238. The inner first layer 235 (and / or the inner second layer 238) may be configured as a fluid absorption layer configured to absorb the fluid F generated in the endothermic phase change reaction. The inner first layer 235 (and / or the inner second layer 238) may be made of a corresponding material having endothermic heat of dissolution, i.e., a material that absorbs heat upon dissolution, such as sodium acetate. In other words, the inner first layer 235 (and / or the inner second layer 238) may be configured to receive the fluid F from the endothermic phase change reaction and at the same time have a cooling effect.Referring now to FIG. 3, a schematic flow diagram for a method 100 of forming the thermal barrier 10 is shown. The method 100 need not be applied in the order given herein. Moreover, it should be understood that some steps may be omitted. The method 100 may begin with block 110, which includes recovering the compressible element 30 and depositing the phase change materials 42 into the pockets 40. In one example, block 110 includes sub-blocks 112 and 114. Per sub-block 112, the pockets 40 are created in the compressible member 30, e.g., by cutting out portions of the compressible member 30. per sub-block 114, the phase change materials 42 are inserted into the pockets 40.In another example, block 110 includes sub-blocks 116 and 118. Per sub-block 116, the compressible element 30 is made of a polymeric base 330 (see FIG. 4C ). While the polymeric base 330 is in liquid form, the phase change materials 42 are blended into the polymeric base 330. Subsequently, in sub-block 118, the polymeric base 330 is solidified.From block 110, the method 100 proceeds to block 120. In block 120 of FIG. 3, the method 100 includes positioning the first layer 36 and the second layer 38 on the first side 32 and the second side 34 of the compressible member 30, respectively. the first layer 36 and the second layer 38 may be a coating that is physically coated or bonded to the compressible member 30. The first layer 36 and the second layer 38 may be configured to be electrically insulating and thermally conductive.From block 120, the method 100 proceeds to block 130. In block 130 of FIG. 3, the thermal barrier 10 may be positioned in the power module assembly 12. As noted above with respect to FIG. 1, the thermal barrier 10 may be positioned between individual cells of the battery cell 14 and / or between stacks of the battery cell 14 disposed in the respective modules 18. In summary, the thermal barrier 10 may be configured to serve a variety of purposes including, but not limited to, absorbing heat, extinguishing flames, reflecting radiant heat, and responding to expansion of the battery cell 14.As used in this specification and in the claims, the terms "for example," "e.g., "like," and "similar," and the verbs "comprise," "have," "include," and their other verb forms, when used in connection with a listing of one or more components or other items, are each to be construed as unlimited, meaning that the listing is not to be understood as excluding other, additional components or items.

Claims

A thermal barrier (10) for use in a power module assembly (12) having at least one battery cell (14), the thermal barrier (10) comprising: at least one compressible element (30) having one or more pockets (40), the at least one compressible element (30) defining a first side (32) and a second side (34); a first layer (36) and a second layer (38) disposed adjacent the at least one compressible element (30), the first layer (36) disposed on the first side (32) and the second layer (38) disposed on the second side (34); one or more phase change materials (42, 342) configured to be deposited into the one or more pockets (40); and wherein the one or more phase change materials (42, 342) are configured to undergo an endothermic phase change reaction when a temperature of the at least one battery cell (14) is at or above an activation temperature; wherein: the first layer (36) comprises an outer first layer (233) and an inner first layer (235); at the endothermic phase change reaction, at least one fluid (F) is released; the inner first layer (233) is configured to absorb the fluid (F) generated in the endothermic phase change reaction and simultaneously generate a cooling effect; and the outer first layer (235) is configured to at least partially reflect radiant heat; and wherein: the one or more pockets (40) include at least one through hole (140) extending from the first side (32) to the second side (34) of the at least one compressible element (30); or the one or more pockets (40) comprise a first set of blind holes (239) extending along the first side (32) and a second set of blind holes (241) extending along the second side (34) of the at least one compressible element (30).The thermal barrier (10) of claim 1, wherein: the endothermic phase change reaction releases at least one fluid (F) having flame extinguishing properties.The thermal barrier (10) of claim 2, wherein: the one or more phase change materials (42, 342) include sodium bicarbonate; and the at least one fluid (F) includes carbon dioxide gas.The thermal barrier (10) of claim 1, wherein: the one or more phase change materials (42, 342) include at least one or a combination of aluminum bicarbonate, ammonium bicarbonate, beryllium bicarbonate, calcium bicarbonate, lithium bicarbonate, magnesium bicarbonate, potassium bicarbonate, and sodium bicarbonate.The thermal barrier (10) of claim 1, wherein: the first group of blind holes (239) is offset relative to the second group of blind holes (241).The thermal barrier (10) of claim 1, wherein: the at least one compressible element (30) includes a polymeric base (330) such that the one or more phase change materials (342) are distributed within the polymeric base (330).The thermal barrier (10) of claim 1, wherein: the one or more phase change materials (42, 342) include a first material characterized by a first activation temperature in a first region and a second material characterized by a second activation temperature in a second region, the first region being different than the second region.

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