Battery module with immersion barrier to mitigate thermal runaway of pouch battery cells

Abstract

A battery module (26) comprising: a first pouch battery cell (28-1) and an adjacent second pouch battery cell (28-2); a dielectric fluid (30) in direct contact with and circulating over and around each of the first and second battery cells; a dip barrier (32) disposed between the first pouch battery cell (28-1) and the second pouch battery cell (28-2) and defining an opening (34) configured to permit the passage of the dielectric fluid (30) between the first pouch battery cell (28-1) and the second pouch battery cell (28-2) to thereby enable the localization of a thermal runaway event in the first pouch battery cell (28-1) by minimizing the transfer of high-temperature gases between the first pouch battery cell (28-1) and the second pouch battery cell (28-2) via the dielectric fluid (30), and to control the propagation of the thermal runaway event in the battery module (26); and a battery module housing (38) surrounded by an external environment and configured to that it receives and holds the first pouch battery cell (28-1), the second pouch battery cell (28-2), the dielectric fluid (30) and the immersion barrier (32), further comprising a deflector (46) extending over one of the first and second pouch battery cells (28-1, 28-2) and configured to selectively shield one of the first and second pouch battery cells (28-1, 28-2) from battery cell debris originating from the other of the first and second pouch battery cells (28-1, 28-2) and pivoting under pressure and allowing the escape of high temperature gases from the shielded pouch battery cell (28-1, 28-2).

Description

INTRODUCTION

[0001] The present invention relates to a battery module having a dip barrier for mitigating thermal runaway in a pouch battery cell module.

[0002] A battery module or battery assembly can consist of a large number of battery cells arranged relatively close together. Batteries can be broadly divided into primary and secondary batteries. Primary batteries, also known as disposable batteries, are designed to be used until they are exhausted and are then simply replaced with new batteries. Secondary batteries, commonly referred to as rechargeable batteries, use a special chemistry that allows such batteries to be repeatedly recharged and reused, offering economic, environmental, and user-friendly advantages over disposable batteries. Batteries can be designed, for example, as cylindrical cells, button cells, or pouch cells.

[0003] Rechargeable batteries can be used to power items as diverse as toys, consumer electronics, and motor vehicles. Certain chemical properties of rechargeable batteries, such as lithium-ion cells, as well as external factors, can cause internal reaction rates that generate significant amounts of heat energy. Such chemical reactions can cause the batteries to generate more heat than is effectively dissipated. When a battery cell is exposed to elevated temperatures for extended periods, thermal runaway can occur. Accordingly, thermal runaway that begins in a single cell can cause the heat to spread to neighboring cells in the module, and thermal runaway can affect the entire battery assembly.

[0004] DE 11 2020 000 386 T5 shows an electric battery comprising:- a plurality of power storage cells arranged within a sealed space,- a dielectric fluid with which the sealed space is filled,- at least one fluid guide made of low-density plastic and arranged within the sealed space, wherein the fluid guide defines at least one flow channel for the dielectric fluid in contact with the power storage cells,- a device for circulating the dielectric fluid.

[0005] DE 10 2019 129 473 A1 relates to a cell module for a high-voltage storage device, comprising: two or more cells for storing electrical energy; and one or more thermal barriers, each arranged between two adjacent cells, each containing an aerogel and exerting a thermally insulating effect between the respective adjacent cells. Furthermore, DE 10 2019 129 473 A1 relates to a high-voltage storage device containing such a cell module. DESCRIPTION

[0006] The object of the invention is to increase the safety of the battery module. This object is achieved by the subject matter of the independent claim. Further developments can be found in the subclaims.

[0007] A battery module comprises a first pouch battery cell and an adjacent second pouch battery cell. The battery module also contains a dielectric fluid in direct contact with, circulating over, and around the first battery cell and the second battery cell. The battery module additionally includes a dip barrier disposed between the first pouch battery cell and the second pouch battery cell, defining an opening configured to control the passage of the dielectric fluid between the first pouch battery cell and the second pouch battery cell.The immersion barrier thereby enables the localization of a thermal runaway event in the first pouch battery cell by minimizing the transfer of high-temperature gases between the first pouch battery cell and the second pouch battery cell via the dielectric fluid and controlling the propagation of the thermal runaway event within the battery module. The battery module further comprises a battery module housing surrounded by an external environment and configured to contain and retain the first pouch battery cell, the second pouch battery cell, the dielectric fluid, and the immersion barrier.

[0008] The battery module housing may include a plurality of sidewalls, a bottom portion, and a lid portion. In such an embodiment, the dip barrier may extend to and directly contact each of the plurality of sidewalls, the bottom portion, and the lid portion, such that the passage of the dielectric fluid between the first and second battery cells is controlled exclusively through the opening.

[0009] The battery module may also contain an aerogel layer arranged parallel to the immersion barrier.

[0010] The battery module may additionally contain a compression foam element arranged parallel to the immersion barrier.

[0011] The battery module may also include a deflector extending over one of the first and second pouch battery cells and configured to selectively shield battery cell debris originating from the other of the first and second pouch battery cells. The deflector may also pivot under pressure, allowing the high-temperature gases to escape from the shielded pouch battery cell.

[0012] The deflector may comprise a first portion arranged parallel to the diving barrier and a second portion arranged at an angle of between 90 and 135 degrees to the first portion.

[0013] The deflector can be integrated into the diving barrier so that the deflector is arranged at an angle between 90 and 135 degrees relative to the diving barrier.

[0014] A battery pack using a plurality of such battery modules and a motor vehicle having a power source and the battery pack configured to supply electrical energy to the power source are also disclosed.

[0015] The above features and advantages, as well as other features and advantages of the present invention, will be readily apparent from the following detailed description of the embodiment(s) and the best mode(s) for carrying out the described disclosure, taken in conjunction with the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 is a schematic plan view of one embodiment of a motor vehicle having multiple power sources and a battery pack with pocket battery cells arranged in one or more modules configured to generate and store electrical energy. Fig. 2 is a schematic side sectional view of the Fig. 1 shown battery module with a battery module housing. Fig. 3 is a schematic sectional view of the front of the Fig. 1, showing individual pouch battery cells arranged side by side and immersion barriers arranged between adjacent pouch battery cells, according to the disclosure. Fig. Figure 4 is a schematic plan view of a typical pouch battery cell. Fig. 5 is a schematic sectional view of an embodiment of the Fig. 1, showing a particular arrangement of aerogel layers and compression foam elements according to the disclosure. Fig. 6 is a schematic sectional view of the front of an embodiment of the Fig. 1, showing a different arrangement of aerogel layers and compression foam elements according to the disclosure. Fig. 7 is a schematic sectional view of an embodiment of the Fig. 1, showing deflectors disposed near dip barriers and configured to shield individual battery cells as described in the disclosure. Fig. Figure 8 is a schematic sectional view of the front of an embodiment of the Fig. 1, showing an array of deflectors integrated with respective immersion barriers and configured to shield individual battery cells, according to the disclosure. DETAILED DESCRIPTION

[0016] Those of ordinary skill in the art will recognize that terms such as "top," "bottom," "upward," "downward," "up," "downward," "left," "right," etc., are used descriptively for the figures and do not represent limitations on the scope of the disclosure as defined by the appended claims. Furthermore, the teachings herein may be described in terms of functional and / or logical block components and / or various processing steps. It should be understood that such block components may consist of any number of hardware, software, and / or firmware components configured to perform the specified functions.

[0017] In Fig. 1, a motor vehicle 10 having a powertrain 12 is depicted. The vehicle 10 may be, but is not limited to, a commercial vehicle, an industrial vehicle, a passenger vehicle, an aircraft, a watercraft, a train, or the like. It is also contemplated that the vehicle 10 may be a mobile platform, such as an aircraft, an all-terrain vehicle (ATV), a boat, a personal mobility device, a robot, and the like, to fulfill the purposes of this disclosure. The powertrain 12 includes a power source 14 configured to produce a power source torque T (in Fig. 1) for propelling the vehicle 10 via driven wheels 16 relative to a road surface 18. The energy source 14 is shown as an electric motor-generator.

[0018] As in Fig. 1, the powertrain 12 may also include an additional power source 20, such as an internal combustion engine. The power sources 14 and 20 may cooperate to propel the vehicle 10. The vehicle 10 additionally includes an electronic control unit 22 and a battery pack 24 configured to generate and store electrical energy through heat-generating electrochemical reactions to supply the electrical energy to the power sources 14 and 20. The electronic control unit 22 may be a central processing unit (CPU) that controls various functions of the vehicle 10 or a powertrain control module (PCM) configured to control the powertrain 12 to produce a predetermined power source torque T.The battery pack 24 can be connected to the power sources 14 and 20, the electronic control unit 22, and other vehicle systems via a high-voltage bus 25. Although the battery pack 24 is described primarily with regard to a vehicle environment, nothing precludes the battery pack in question from also being used to power other, non-automotive systems.

[0019] As in Fig. 1, the battery pack 24 may include one or more sections, such as battery arrays or modules 26. As shown in the Fig. 2 and Fig. 3, the battery module 26 comprises a plurality of battery cells, such as a first battery cell 28-1, an adjacent, directly adjacent second battery cell 28-2, and a third battery cell 28-3 adjacent to the second battery cell, each battery cell extending generally upward, ie, in the Z-direction, as shown in the Fig. 2 and Fig. 3. Although one module 26 and three battery cells 28-1, 28-2, 28-3 are shown, nothing precludes the battery pack 24 from having a larger number of such modules and battery cells. A typical pouch battery cell, such as cells 28-1, 28-2, 28-3, is shown in Fig. 4. The battery module 26 also includes a dielectric fluid 30 that is in direct contact with, substantially surrounding, and circulating over and around the first battery cell 28-1, the second battery cell 28-2, and the third battery cell 28-3. In other words, the battery cells 28-1, 28-2, 28-3 are completely immersed in the dielectric fluid 30. The dielectric fluid 30 can be circulated via a pressurized source, such as an external fluid pump (not shown), to remove thermal energy from the first, second, and third pouch battery cells 28-1, 28-2, 28-3 while the battery module 26 generates / stores electrical energy.

[0020] The battery module 26 additionally includes immersion barriers 32 that serve as insulating elements. As shown, one immersion barrier 32 is arranged between the first battery cell 28-1 and the second battery cell 28-2, while another immersion barrier 32 is arranged between the second battery cell 28-2 and the third battery cell 28-3. The immersion barrier 32 is made of metal or another material that can withstand a temperature of up to 1000 degrees Celsius. In particular, the immersion barrier can be a steel plate with a thickness in the range of 0.2 to 0.4 mm, and in particular can have a thickness of 0.3 mm. The immersion barrier 32 is configured to limit the direct thermal energy transfer between the adjacent battery cells 28-1, 28-2, 28-3 during operation of the battery module 26.However, the dielectric fluid 30, which circulates freely through the battery module 26, continues to transfer thermal energy between the adjacent battery cells. The immersion barrier 32 defines one or more openings 34 configured to control the passage and communication of the dielectric fluid between the first battery cell 28-1, the second battery cell 28-2, and the third battery cell 28-3. The size of the opening(s) 34 is intended to balance the conflicting interests of adequate coolant circulation and thermal energy dissipation between the adjacent battery cells 28-1, 28-2, and 28-3.

[0021] The battery module 26 also includes a battery module housing 38 that is surrounded by an environment external to the battery module housing or the ambient environment 40. The battery module housing 38 is configured to receive and retain the first, second, and third battery cells 28-1, 28-2, and 28-3, the dielectric 30, and the immersion barrier 32. As shown in Fig. As shown in Figure 3, a battery module 26 may have more than a single pouch battery cell, such as two or more of the cells 28-1, 28-2, 28-3 between two nearest immersion barriers 32. In such an embodiment, the battery module 26 may also include spacers 37 extending along and between adjacent battery cells. The spacers 37 space the adjacent battery cells apart, thus allowing the dielectric fluid 30 to flow past the respective cells and dissipate thermal energy.

[0022] Generally, during normal operation of the battery module 26, the dielectric fluid 30 absorbs the thermal energy released by the first, second, and third pouch battery cells 28-1, 28-2, and 28-3 and allows the transfer of thermal energy out of the battery module. Under extreme conditions, such as during a thermal runaway (in Fig. 3 by the numeral 36), the thermal energy released by the pouch cell undergoing the event is typically absorbed by the dielectric fluid 30 and transferred between the adjacent cells 28-1, 28-2, 28-3. Such transfer of energy between the cells in the battery module 26 can eventually lead to a spread of thermal energy throughout the battery module, resulting in thermal runaway. Accordingly, the term "thermal runaway" generally refers to an uncontrolled increase in temperature within a battery module.

[0023] During thermal runaway, the heat buildup within a battery module or battery cell exceeds the module's ability to dissipate heat, resulting in a further increase in temperature. Thermal runaway can be triggered by various conditions, such as a short circuit within the cell, improper use of the cell, physical abuse, manufacturing defects, or extreme external temperatures. For example, during thermal runaway 36 in the first pouch battery cell 28-1, each opening 34 of the immersion barrier 32 functions as an orifice by metering a predetermined amount of the dielectric fluid 30 between the adjacent pouch battery cells 28-1 and 28-2.The opening(s) 34 are specifically configured to facilitate the localization of the thermal runaway event 36 within the first pouch battery cell 28-1 by minimizing the transfer of high-temperature gases 36A between the first pouch battery cell 28-1 and the second pouch battery cell 28-2 via the dielectric fluid 30. Accordingly, the opening(s) 34 control the propagation rate of the thermal runaway event within the battery module 26.

[0024] With continued reference to Fig. 2-3, the battery module housing 38 includes a plurality of sidewalls 38-1, 38-2, 38-3, 38-4 and a bottom portion 38-5 secured and sealed to the sidewalls. The battery module housing 38 also includes a cover portion 38-6 disposed generally over the first, second, and third battery cells 28-1, 28-2, and 28-3 and secured to the sidewalls 38-1, 38-2, 38-3, and 38-4. The immersion barrier 32 extends to and directly contacts each of the plurality of sidewalls 38-1, 38-2, 38-3, 38-4, the bottom portion 38-5, and the cover portion 38-6, such that the passage of the dielectric fluid 30 between the first, second, and third battery cells 28-1, 28-2, and 28-3 is controlled exclusively via and through the respective openings 34. The openings 34 may be formed through each of the immersion barriers 32 near the sidewalls 38-1, 38-2, 38-3, 38-4 and / or near the bottom portion 38-5 and the cover portion 38-6 (in Fig. 3).

[0025] As in Fig. 3, the battery module 26 may also include aerogel layers 42 arranged parallel to the immersion barrier 32. Each aerogel layer may have a thickness in the range of 2 to 3 mm, in particular a thickness of 2.3 mm. The aerogel layers may be arranged on either side of, and in direct contact with, a particular immersion barrier 32. For example, as shown, an aerogel layer 42 may be arranged on either side of a particular immersion barrier 32, such that the first pouch battery cell 28-1 and the third pouch battery cell 28-3 contact an aerogel layer on one side and one of the housing sidewalls 38-1 or 38-3 on the other side. The second battery cells 28-2 may then be sandwiched between two aerogel layers 42.The amount of thermal energy trapped in each compartment between the individual immersion barriers 32 can be controlled by the size of the openings 34, thus allowing a reduction in the thickness of the aerogel layer(s) 42.

[0026] As in Fig. 5, the battery module 26 may additionally include compression foam elements 44 arranged parallel to the immersion barrier 32. The compression foam element 44 may be comprised of a high-temperature polymer foam having a stiffening substructure. Each compression foam element 44 is specifically configured to limit the amount of thermal energy transfer between adjacent battery cells, such as cells 28-1, 28-2, and 28-3, during operation of the battery module 26. Each compression foam element 44 is further configured to maintain consistent and uniform contact with the respective first pouch battery cell 28-1, second pouch battery cell 28-2, or third pouch battery cell 28-3 during the alternating expansion of the respective cells during charging and contraction of the cells during discharging.

[0027] Each of the first, second and third pouch battery cells 28-1, 28-2 and 28-3 may be arranged between two compression foam elements 44 such that each of the compression foam elements 44 is in direct contact with the nearest pouch battery cell 28-1, 28-2 or 28-3 (shown in Fig. 5). Alternatively, each individual compression foam element 44 may be positioned between a corresponding aerogel layer 42 and one of the first, second, or third battery cells 28-1, 28-2, or 28-3, and another compression foam element 44 may be positioned between one of the side walls 38-2 or 38-4 and the nearest battery cell 28-1 or 28-3 (shown in Fig. 6). In the embodiment of the battery module 26 having both the compression foam elements 44 and the aerogel layers 42, each aerogel layer 42 may be disposed between a corresponding dip barrier 32 and a specific compression foam element 44.

[0028] For example, if the first battery cell 28-1 experiences a thermal breakdown 36 (as in Fig. 3), the excess gases generated by such an event would result in greatly increased internal pressure, which tends to deform and rupture the structure of the affected first pouch battery cell. Rupture of the affected first pouch battery cell 28-1 would allow the gases to escape the pouch, carrying with them various internal parts of the battery cell, which become hot debris 48. Such debris 48 may be ejected from the affected first pouch battery cell 28-1 in the Z-direction and travel over or around the immersion barrier 32 to the adjacent second pouch battery cell 28-2. The escape of high-temperature gases 36A and debris 48 would increase the likelihood of thermal runaway within the battery module 26 from the first battery cell 28-1 to the second battery cell 28-2, thereby triggering a chain reaction and compromising the entire battery module 26.Although both the first and second pouch battery cells 28-1, 28-2 may generate high-temperature gases 36A and debris 48 due to thermal runaway 36, the present disclosure focuses specifically on an exemplary case where the first pouch battery cell 28-1 experiences thermal runaway.

[0029] To protect each opening 34 from such escape of hot gases and debris through the adjacent cell, the battery module 26 may further include baffles 46, as shown in Fig. 7. Each baffle 46 extends over one of the first, second, and third pouch battery cells 28-1, 28-2, 28-3 and is configured to selectively shield it from battery cell debris 48. In particular, the baffle 46 is disposed above the first battery cell 28-2 to protect that cell from debris originating from the other, adjacent first battery cell 28-1. Each baffle 46 is also configured to pivot away from the shielded battery cell 28-1, 28-2, or 28-3 under the pressure of the high-temperature gases 36A emitted by the respective cell, allowing the gases and debris 48 to escape from the shielded battery cell. The pivoting movement of the deflector 46 is enabled by the deflector being anchored at point 46A and extending beyond the shielded battery cell.

[0030] With further reference to Fig. 7, each deflector 46 may include a first portion 46-1 disposed parallel to the immersion barrier 32, and a second portion 46-2. As illustrated, the second portion 46-2 may be disposed at an angle θ that may range from 90 to 135 degrees relative to the first portion 46-1. Each deflector 46 may be a separate component disposed proximate a single immersion barrier 32 (as shown in Fig. 7). Alternatively, each deflector 46 may be integrated into a single diving barrier 32 (in Fig. 8). In other words, the deflector 46 and the corresponding diving barrier 32 of Fig.8 can be constructed as a single, unitary component. The deflector 46 can be arranged at an angle θ in the range of 90 to 135 degrees relative to the immersion barrier 32, which in turn is parallel to the battery cells 28-1, 28-2, 28-3 of the bag. The deflectors 46 are configured to minimize the transfer of high-temperature gases and debris from one of the first, second, and third battery cells 28-1, 28-2, 28-3 to one or more of the other adjacent cells and to control the propagation of a thermal runaway event 36 within the battery module 26.

[0031] During operation of the battery module 26, the aerogel layers 42 and / or the compression foam elements 44 mitigate the propagation of thermal runaway directly between the individual battery cells and enable the transfer of energy to the dielectric 30. Furthermore, the immersion barrier 32 with the openings 34 absorbs excess thermal energy from the respective pouch battery cell 28-1, 28-2, or 28-3 experiencing a thermal event, while regulating or metering the amount of that thermal energy transferred via the dielectric fluid 30 to the adjacent pouch cell(s). Thus, the design of the immersion barrier 32 enables the excess thermal energy generated by thermal runaway in a particular battery cell to be dissipated from the battery module 26 to the environment 40 via the circulating dielectric fluid 30 with minimal impact on the adjacent cell(s).Furthermore, the deflectors 46 direct high-temperature gases 36A and debris 48 emitted by the affected pouch cell away from the adjacent cell(s), thus minimizing the possibility of the thermal event affecting other cells in the battery module 26. Therefore, the design of the disclosed battery module 26 is particularly effective in mitigating the propagation of thermal runaway between the individual cells of the pouch battery without the need for additional external hardware or controls.

[0032] The detailed description and the drawings or illustrations support and describe the disclosure, but the scope of the disclosure is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed disclosure have been described in detail, various alternative designs and embodiments exist for carrying out the disclosure defined in the appended claims. Moreover, the embodiments illustrated in the drawings or the features of various embodiments recited in this description are not necessarily intended to be independent embodiments.Rather, it is possible that each of the features described in one of the embodiments may be combined with one or more other desired features of other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the scope of the appended claims.

Claims

[1] A battery module (26) comprising: a first pouch battery cell (28-1) and an adjacent second pouch battery cell (28-2); a dielectric fluid (30) in direct contact with and circulating over and around each of the first and second battery cells; a dip barrier (32) disposed between the first pouch battery cell (28-1) and the second pouch battery cell (28-2) and defining an opening (34) configured to permit the passage of the dielectric fluid (30) between the first pouch battery cell (28-1) and the second pouch battery cell (28-2) to thereby enable the localization of a thermal runaway event in the first pouch battery cell (28-1) by minimizing the transfer of high-temperature gases between the first pouch battery cell (28-1) and the second pouch battery cell (28-2) via the dielectric fluid (30), and to control the propagation of the thermal runaway event in the battery module (26); and a battery module housing (38) surrounded by an external environment and configured to that it receives and holds the first pouch battery cell (28-1), the second pouch battery cell (28-2), the dielectric fluid (30) and the immersion barrier (32), further comprising a deflector (46) extending over one of the first and second pouch battery cells (28-1, 28-2) and configured to selectively shield one of the first and second pouch battery cells (28-1, 28-2) from battery cell debris originating from the other of the first and second pouch battery cells (28-1, 28-2) and pivoting under pressure and allowing the escape of high temperature gases from the shielded pouch battery cell (28-1, 28-2). [2] The battery module (26) of claim 1, wherein the battery module housing (38) includes a plurality of side walls (38-1, 38-2, 38-3, 38-4), a bottom portion (38-5), and a cover portion (38-6), and wherein the immersion barrier (32) extends to and directly contacts each of the plurality of side walls (38-1, 38-2, 38-3, 38-4), the bottom portion (38-5), and the cover portion (38-6), such that the passage of the dielectric fluid (30) between the first and second pouch battery cells (28-1, 28-2) is controlled exclusively via the opening (34). [3] The battery module (26) of claim 1, further comprising an aerogel layer (42) arranged parallel to the immersion barrier (32). [4] The battery module (26) of claim 1, further comprising a compression foam element (44) arranged parallel to the immersion barrier (32). [5] The battery module (26) of claim 1, wherein the deflector (46) has a first portion disposed parallel to the immersion barrier (32) and a second portion disposed at an angle of between 90 and 135 degrees relative to the first portion. [6] The battery module (26) of claim 1, wherein the deflector (46) is integrated into the immersion barrier (32) such that the deflector (46) is disposed at an angle of between 90 and 135 degrees relative to the immersion barrier (32).

Images