Multi-cell rechargeable energy storage system

Abstract

Multi-cell rechargeable energy storage system (RESS) (24) comprising: a plurality of battery cells (28), each battery cell (28) having a corresponding cell vent (28B) configured to expel gases (36); and a cell carrier assembly (42) with thermal runaway prevention, comprising: a cell holder (44) configured to support the plurality of battery cells (28) and having a holder body (44A) defining a plurality of openings (46) arranged in rows (48), each opening (46) configured to be aligned with and in fluid communication with the cell vent (28B) of one of the plurality of battery cells (28); a plurality of thermal barrier strips (50) secured to the cell holder (44), each thermal barrier strip (50) extending parallel to a respective row (48) of openings (46) and configured to thermally insulate corresponding battery cells (28) from gases (36) emitted by adjacent battery cells (28) during thermal runaway; and a plurality of potting elements (52), each potting element (52) being disposed in one of the plurality of openings (46) between a respective battery cell (28) and a corresponding thermal barrier strip (50) and being configured to adhere to the battery cell (28) and the corresponding thermal barrier strip (50) to maintain the position of the battery cell (28) on the cell holder (44); wherein the multi-cell RESS further comprises: a RESS housing (32) having a shell (32-1) and a mating cover (32-2) configured to receive the plurality of battery cells (28), the cell holder (44), the plurality of thermal barrier strips (50), and the plurality of potting elements (52), wherein the cell holder (44) is configured to engage and mate with the housing shell (32-1); wherein: the housing shell (32-1) comprises a plurality of channels (54) and the cell holder (44) comprises a plurality of integrated projection portions (56); each of the cell holder projection portions (56) is configured to engage one of the housing shell channels (54), thereby forming a plurality of longitudinal fluid passages (58); and each fluid passage (58) extends along at least one of the rows (48) of openings (46) to conduct the gases (36) emitted by the corresponding battery cells (28).

Description

[0001] This description relates to a battery cell carrier assembly with integrated thermal runaway mitigation for a multi-cell rechargeable energy storage system (RESS).

[0002] A battery system for generating and storing electrical energy typically comprises one or more battery cells to supply a load. Multiple battery cells can be arranged in close proximity to each other to form a battery cell array or system, e.g., a battery module, a battery pack, etc. 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 used up and then simply replaced with new batteries. Secondary batteries, commonly known 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.

[0003] Secondary batteries can be used to store electrical energy for future use and as a buffer between peak power generation and peak system loads, for example, in stationary energy storage systems and electric vehicles (EVs). Certain chemistries of rechargeable batteries, as well as external factors, can cause internal reaction rates that generate significant amounts of heat energy. When a battery cell is exposed to elevated temperatures for extended periods, thermal runaway can occur. Heat buildup in one cell can cause the heat to spread to neighboring cells, thus affecting the entire battery assembly.

[0004] DE 10 2017 212 223 A1 describes a battery of an electrically powered motor vehicle, with a number of energy storage cells, each having an electrical connection and a cell housing with a housing opening provided on a first housing side, which is closed with a bursting membrane, and with a cooling plate arranged between the cell housing and a cell degassing chamber with a passage which is aligned with the housing opening or at least partially overlaps, wherein the cooling plate for supplying a coolant into the cell housing has an inlet opening into the passage, which is blocked by means of a closure which opens in the event of triggering.

[0005] DE 10 2021 119 807 A1 describes a battery assembly including a housing having a base and battery cell frames arranged along an axis within the housing. Each of the battery cell frames includes a frame foot that projects laterally outward. An end plate is located at one axial end of the battery cell frames. The end plate includes an end plate retention flange that projects laterally outward to laterally overlap a portion of the retention element. A retention element extends axially adjacent to the battery cell frames. The retention element includes a lip that projects laterally inward over the frame feet so that the frame feet are held between the lip and the base. An axial end portion of the retention element is secured directly to the end plate retention flange.

[0006] DE 10 2021 111 119 A1 describes an electrochemical assembly comprising a housing forming an interior, an electrochemical cell, a device, and a pressure relief valve. The electrochemical cell is arranged within the interior. The device contains a manifold component. The manifold component contains a polymer matrix and an additive embedded in the polymer matrix. The additive comprises an endothermic phase-change material, a flame-retardant material, an intumescent material, or a combination thereof. The device forms a device outlet. The pressure relief valve has a valve inlet fluidically connected to the interior and a valve outlet fluidically connected to the device. The pressure relief valve is configured to direct a gas from the interior to the device when a pressure in the interior exceeds a predetermined pressure.The manifold component is configured to be in fluid communication with the gas and to direct the gas to the device outlet.

[0007] It can be considered a task to provide a multi-cell rechargeable energy storage system to effectively dissipate thermal energy in order to reduce heat buildup and the resulting degradation of the battery system performance.

[0008] The object is achieved by a multi-cell rechargeable energy storage system (RESS) according to claim 1. Furthermore, an exemplary vehicle is described which has the RESS according to the invention.

[0009] A rechargeable multi-cell energy storage system (RESS) according to the invention comprises a plurality of battery cells, each battery cell having a corresponding cell vent configured to expel gases. The RESS also includes a cell support assembly with thermal runaway prevention and has a cell holder configured to support the plurality of battery cells. The cell holder includes a holder body defining a plurality of openings arranged in rows. Each opening is configured to be aligned with and in fluid communication with the cell vent of one of the plurality of battery cells. The cell support assembly also includes a plurality of thermal barrier strips adhered to the cell holder.Each thermal barrier strip extends parallel to a corresponding row of openings and is configured to thermally insulate the corresponding battery cells from gases emitted by adjacent battery cells during thermal runaway. The cell carrier assembly additionally includes a plurality of encapsulating elements. Each encapsulating element is disposed in one of the plurality of openings between a respective battery cell and a corresponding thermal barrier strip and is configured to adhere to the battery cell and the corresponding thermal barrier strip to maintain the position of the battery cell on the cell carrier.

[0010] According to the invention, the multi-cell RESS also comprises a RESS housing with a shell and a matching lid. The RESS housing is configured to accommodate the plurality of battery cells, the cell holder, the plurality of thermal barrier strips, and the plurality of encapsulation elements. The cell holder is configured to engage and mate with the housing shell.

[0011] According to the invention, the housing shell comprises a plurality of channels, and the cell holder includes a plurality of integrated protrusion portions. Each of the protruding portions of the cell holder is configured to engage one of the housing shell channels, thereby forming a plurality of longitudinal fluid passages. Each fluid passage extends along at least one of the rows of openings to guide the gases emitted by the corresponding battery cells positioned on the cell holder.

[0012] In one embodiment, each of the openings, when not blocked by a corresponding potting element, is configured to direct gases emitted or vented from one of the plurality of battery cells to the longitudinal channel.

[0013] In one embodiment, the thermal barrier strip comprises a strip portion extending into a corresponding housing shell channel between the housing shell and the corresponding retainer projection portion.

[0014] In one embodiment, the multi-cell RESS also includes an adhesive disposed within the housing shell channel between the housing shell and the corresponding retainer projection portion so as to secure the cell carrier assembly to the housing shell.

[0015] In one embodiment, each of the encapsulating elements is configured to detach from the respective opening under the force of the ejected gases, thereby breaking off a portion of the corresponding barrier strip into the corresponding fluid passage.

[0016] In one embodiment, each of the potting elements comprises a flame retardant material, such as sodium bicarbonate.

[0017] In one embodiment, each of the potting elements consists of a non-self-leveling, high-viscosity paste that is introduced into the respective opening of the plurality of openings and cured there.

[0018] In one embodiment, the potting compound comprises additives designed to adapt the thermal expansion coefficient of the potting compound to the thermal expansion coefficient of the cell holder.

[0019] In one embodiment, the cell holder is made of a glass-filled nylon.

[0020] In one embodiment, each of the battery cells is a cylindrical or a prismatic cell.

[0021] A motor vehicle incorporating the multi-cell rechargeable energy storage system (RESS) described above, for example, is also described. Fig. 1 is a schematic plan view of an exemplary motor vehicle having multiple power sources and a multi-cell rechargeable energy storage system (RESS) configured to generate and store electrical energy used by vehicle systems including the power sources. Fig. 2 is a schematic side view of the Fig. 1, which shows battery cells arranged in a battery system housing with a tray and a cover. Fig. 3 is a schematic plan view in Fig. A close-up of the RESS shown in Figure 1, showing battery cells arranged in rows on a cell carrier assembly with thermal runaway prevention. Fig. 4 is a schematic plan view of the Fig. 3, showing the cell carrier assembly with a cell holder having openings aligned with the vents of the battery cells, thermal barrier strips attached to the cell holder, and a plurality of potting elements. Fig. 5 is a schematic plan view of the Fig. 4 shown in close-up, showing a battery cell experiencing thermal runaway and a corresponding response of the cell carrier assembly.

[0022] In Fig. 1, an exemplary 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 for the purposes of this description. The powertrain 12 includes a power source 14 configured to generate power source torque for propelling the vehicle 10 via driven wheels 16 relative to a road surface 18. The power source 14 is depicted as an electric motor-generator.

[0023] As in Fig. 1, the powertrain 12 may also include an additional power source 20, e.g., an internal combustion engine. The power sources 14 and 20 may cooperate to propel the vehicle 10. The vehicle 10 further includes an electronic control unit 22 and a rechargeable multi-cell energy storage system (RESS) 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 torque from the power source.The RESS 24 can be connected to the energy sources 14 and 20, the electronic control unit 22 and other vehicle systems via a high-voltage BUS 25.

[0024] The RESS 24 includes a plurality of battery cells 28, which may be divided into battery groups or modules (shown as modules 26-1 and 26-2) and / or organized as a battery pack 27. As shown in Fig. 2, the battery cells 28 in each module of the RESS 24, such as the illustrated module 26-1 and module 26-2, are arranged in individual adjacent rows, such as a first row 30-1, an adjacent, directly adjacent second row 30-2, and third and fourth rows 30-3 and 30-4. As illustrated, each battery cell 28 in the rows 30-1, 30-2, 30-3, 30-4 may be formed as a cylindrical or prismatic cell extending generally upward in an XZ plane. Although two modules, 26-1 and 26-2, are shown with four rows 30-1, 30-2, 30-3, 30-4 of battery cells 28 in each module, nothing precludes the RESS 24 from having a greater or fewer number of such modules and rows.The remainder of this description focuses on the module construction with four rows 30-1, 30-2, 30-3, 30-4 of battery cells 28, which can be adapted to a particular battery module with a desired total number of cells.

[0025] As in Fig. 2, the RESS 24 also includes a battery pack or RESS housing 32 surrounded by an environment 34, i.e., an environment outside the RESS housing. The battery pack housing 32 is configured to accommodate each row 30-1, 30-2, 30-3, 30-4 of the battery cells 28 in the respective modules 26-1, 26-2, and includes a lower housing portion with a housing shell 32-1 and an upper portion with a matching housing cover 32-2 (in Fig. 2). The housing cover 32-2 is configured to engage the housing shell 32-1 to substantially seal the RESS housing 32 and its contents from the external environment 34. As shown, the RESS housing 32 is arranged in a horizontal XY plane such that the housing cover 32-2 is positioned above the housing shell 32-1 when viewed along a Z-axis.

[0026] As in the Fig. 3 and Fig. 4, each battery cell 28 generally includes electrical terminal(s) 28A and corresponding cell vent(s) 28B configured to expel or vent high pressure gases 36 (in Fig. 5). Such gases 36 may be generated within the battery cell 28 as a byproduct of thermal runaway of the cell. As shown in the Fig. 2 and Fig. 3, the RESS 24 may also include a heat sink 38. The heat sink 38 is generally positioned between or below the battery cells 28 and in direct contact with them to thereby absorb thermal energy from the respective battery cells. The heat sink 38 may be configured as a coolant plate with a plurality of coolant channels to circulate a coolant and thereby dissipate thermal energy from the battery cells 28 while the RESS 24 generates / stores electrical energy.

[0027] In general, during normal operation of the RESS 24, the heat sink 38 is capable of absorbing the thermal energy released by the battery cells 28. Under extreme conditions, such as during a thermal runaway event (in Fig. 5 by the numeral 40), the amount of thermal energy released by the cell subjected to the event may saturate the heat sink 38 and exceed the capacity of the RESS 24 to efficiently transfer heat, e.g., from the RESS casing 32 to the ambient 34. As a result, excess thermal energy is typically transferred between adjacent battery cells 28 and between adjacent cell modules 26, resulting in thermal runaway propagation through the RESS 24. The term “thermal runaway” generally refers to an uncontrolled temperature increase in a battery system. In thermal runaway, heat generation within a battery system or battery cell exceeds heat dissipation, resulting in a further temperature increase. Thermal runaway can be triggered by various conditions, e.g.,due to a short circuit in the cell, improper use of the cell, physical abuse, manufacturing defects or extreme external temperatures of the cell.

[0028] For example, if one or more battery cells 28 in a cell module 26 experience thermal runaway 40, the excess gases 36 generated during such an event would result in greatly increased internal cell pressure, tending to rupture the respective cell vent 28B. In the event of such a gas escape, the expelled high-temperature gases 36 (with temperatures up to 1,500 degrees Celsius) may additionally propel cell debris through the enclosure 32 and trigger thermal runaway of other adjacent battery cells 28 and cell modules 26. Accordingly, such transfer of high-temperature gases 36 typically increases the likelihood of a chain reaction affecting a significant portion of the RESS 24.

[0029] As in the Fig. 3 to 5, the RESS 24 also includes a cell support assembly 42 with a thermal runaway barrier disposed within the housing 32. Although not shown, the housing 32 may additionally include a cell support structure disposed proximate the electrical battery terminals 28A to ensure the overall stability of the individual battery cells 28. The cell support assembly 42 includes a cell holder 44 configured to support, e.g., position and retain the battery cells 28. The cell holder 44 may be made of a glass-filled nylon or other temperature-resistant and tough material that enables a rigid and stable cell holder structure. The cell holder 44 includes a holder body 44A (in the Fig. 4 and Fig. 5) having a plurality of openings 46 arranged in rows 48. When the battery cells 28 are installed in the cell holder 44, the battery cell rows 30-1, 30-2, 30-3, 30-4 are arranged in and registered with the corresponding cell holder rows 48 such that each opening 46 is aligned with and in fluid communication with the cell vent 28B of one of the individual battery cells.

[0030] With continued reference to the Fig. 4 and Fig. 5, the cell support assembly 42 also includes a plurality of thermal barrier strips 50 (which may be made of FRB paper), one side of which is coated with an adhesive 51. As shown, the thermal barrier strips 50 are in physical contact with the cell holder 44 and are bonded thereto. Each thermal barrier strip 50 extends parallel to a corresponding row 48 of openings 46 (shown in Fig. 5) and is designed to thermally insulate the corresponding battery cells 28 from gases 36 emitted by adjacent battery cells 28 during thermal runaway 40. The cell carrier assembly 42 further includes potting elements 52 that are mounted in the openings 46 of the cell holder 44 (in Fig. 4).

[0031] Each of the encapsulants 52 may be formed from a non-self-leveling, high-viscosity paste that is introduced into the respective one of the plurality of openings 46 and cured. The use of a non-self-leveling material for the encapsulants 52 serves to maintain the general shape of the encapsulants, rather than allowing the material to flow or run before reaching a cured state. During a manufacturing process described in detail below, such a paste may be introduced into the respective openings 46 and compacted using a suitable tool. Alternatively, each encapsulant 52 may have the preformed shape of a disc that is subsequently inserted into a corresponding opening 46. The encapsulants 52 may be manufactured or molded from a 3M TB5000 material. Additionally, each encapsulant 52 may contain a flame-retardant material such as sodium bicarbonate.

[0032] As in Fig. 4, viewed in the XZ plane, each potting element 52 is disposed in one of the openings 46 between an individual battery cell 28 and a corresponding thermal barrier strip 50 proximate the corresponding cell opening 28B.

[0033] Each encapsulant 52 is configured to be attached or adhered to the respective battery cell 28 and the corresponding thermal barrier strip 50 to maintain the position of the respective battery cell on the cell holder 44. Accordingly, the thermal barrier strips 50, with the adhesive 51, also serve as a holding film for the respective encapsulants 52. To retain the encapsulants 52 within the cell holder 44 during regular operation of the RESS 24, the material of the encapsulants may contain additives configured to adapt the thermal expansion coefficient of the encapsulants to the thermal expansion coefficient of the cell holder 44. Thus positioned, the battery cells 28, the cell holder 44, the thermal barrier strips 50, and the encapsulants 52 are housed in and held by the RESS housing 32.

[0034] As in the Fig. 3-5, the cell holder 44 may be configured to engage and mate with the housing shell 32-1, e.g., by plugging. In particular, as shown, the housing shell 32-1 may include a plurality of channels 54 and the cell holder 44 may include a plurality of integral protrusion or partition wall portions 56. Each cell holder protrusion 56 may be configured to engage one of the housing shell channels 54, thereby forming a plurality of longitudinal fluid passages 58. Each fluid passage 58 so formed may extend along and below at least one of the rows 48 of openings 46 to direct the gases 36 exhausted from the corresponding battery cell(s) 28 positioned on the cell holder 44. With particular reference to the Fig.4 to 5, each of the thermal barrier strips 50 may include a strip main body 50A and lateral strip portions 50B that are folded and arranged substantially perpendicularly, i.e., orthogonally, relative to the strip main body and the respective row 48 of openings 46. Each of the strip portions 50B is arranged parallel to the integrated projections 56 and extends into a corresponding housing shell channel 54 between the housing shell 32-1 and the corresponding retainer projection portion.

[0035] The RESS 24 may additionally include an adhesive 60 disposed within the housing shell channel 54 of the housing carrier between the housing carrier 32-1 and the corresponding retainer projection portion 56, thereby securing the cell retainer assembly 42 to the housing carrier. During thermal runaway 40, each of the encapsulants 52 may be configured to detach and separate from the respective opening 46 under the force of the expelled gases 36. As a result of such venting of a particular battery cell 28, the detachable encapsulant 52 is also expected to break away a portion 50A-1 of the corresponding barrier strip main body 50A. As a result, the corresponding opening 46 becomes free to direct expelled gases 36 into the elongated fluid passage 58. Each fluid passage 58, in turn, may carry the expelled gases 36 and contaminants, such asthe interior of the battery cells, the encapsulation element(s) 52 and the barrier strip section(s) 50A-1, from the RESS housing 32 into the external environment 34.

[0036] Overall, the cell support assembly provides thermal runaway protection for a multi-cell rechargeable energy storage system, such as the RESS 24. The described cell support assembly includes potting elements disposed within openings defined by a battery cell holder and supporting thermal barrier strips disposed beneath the openings such that the potting elements are sandwiched between the battery cells and individual thermal barrier strips. The potting elements are designed to adhere to the respective battery cells, adjacent to or directly opposite the corresponding cell gas vents. The thermal barrier strips are coated with an adhesive to maintain the position of the strips relative to the cell holder and to secure the potting elements in place.The thermal barrier strips may also have folded sides to isolate the longitudinal fluid outlet channels in the RESS housing and prevent thermal runaway energy from impacting adjacent rows of battery cells. Consequently, the structure described above channels thermal runaway energy away from the affected battery cell(s) and out of the RESS housing without triggering thermal runaway in neighboring cells.

Claims

[1] Multi-cell rechargeable energy storage system (RESS) (24) comprising: a plurality of battery cells (28), each battery cell (28) having a corresponding cell vent (28B) configured to expel gases (36); and a cell carrier assembly (42) with thermal runaway prevention, comprising: a cell holder (44) configured to support the plurality of battery cells (28) and having a holder body (44A) defining a plurality of openings (46) arranged in rows (48), each opening (46) configured to be aligned with and in fluid communication with the cell vent (28B) of one of the plurality of battery cells (28); a plurality of thermal barrier strips (50) secured to the cell holder (44), each thermal barrier strip (50) extending parallel to a respective row (48) of openings (46) and configured to thermally insulate corresponding battery cells (28) from gases (36) emitted by adjacent battery cells (28) during thermal runaway; and a plurality of potting elements (52), each potting element (52) being disposed in one of the plurality of openings (46) between a respective battery cell (28) and a corresponding thermal barrier strip (50) and being configured to adhere to the battery cell (28) and the corresponding thermal barrier strip (50) to maintain the position of the battery cell (28) on the cell holder (44); wherein the multi-cell RESS further comprises: a RESS housing (32) having a shell (32-1) and a mating cover (32-2) configured to receive the plurality of battery cells (28), the cell holder (44), the plurality of thermal barrier strips (50), and the plurality of potting elements (52), wherein the cell holder (44) is configured to engage and mate with the housing shell (32-1); wherein: the housing shell (32-1) comprises a plurality of channels (54) and the cell holder (44) comprises a plurality of integrated projection portions (56); each of the cell holder projection portions (56) is configured to engage one of the housing shell channels (54), thereby forming a plurality of longitudinal fluid passages (58); and each fluid passage (58) extends along at least one of the rows (48) of openings (46) to conduct the gases (36) emitted by the corresponding battery cells (28). [2] The multi-cell RESS (24) of claim 1, wherein each of the thermal barrier strips (50) includes a strip portion (50B) extending into a corresponding housing shell channel (54) between the housing shell (32-1) and the corresponding retainer projection portion (56). [3] The multi-cell RESS (24) of claim 1 further comprising an adhesive (60) disposed internally within the housing shell channel (54) between the housing shell (32-1) and the corresponding retainer projection portion (56) to thereby secure the cell support assembly (42) to the housing shell (32-1). [4] The multi-cell RESS (24) of claim 1, wherein each of the encapsulating elements (52) is configured to separate from the respective opening (46) under the force of the expelled gases (36), thereby breaking away a portion of the respective barrier strip (50) into the respective fluid passage (58). [5] The multi-cell RESS (24) of claim 1, wherein each of the potting elements (52) contains a flame-retardant material. [6] The multi-cell RESS (24) of claim 1, wherein each of the encapsulating elements (52) is formed from a non-self-leveling paste that is introduced into the respective opening (46) of the plurality of openings (46) and cured therein. [7] Multi-cell RESS (24) according to claim 6, wherein the potting compound contains additives designed to adapt a thermal expansion coefficient of the potting elements (52) to a thermal expansion coefficient of the cell holder (44). [8] The multi-cell RESS (24) of claim 7, wherein the cell holder (44) is made of a glass-filled nylon.

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