Device for mitigating the propagation of thermal events in battery systems

Abstract

A device for mitigating the propagation of thermal events between battery cells within a battery module assembly (10) is provided. The device includes one or more of several features for preventing a runaway thermal event within one battery cell (48) from triggering a fire or other thermal event within another battery cell within the battery module assembly (10). The device may include one or more of the following: (i) a compression envelope (88) applied to the battery cells (48); (ii) a layered barrier material (104) located between adjacent battery cells (48); (iii) a silicone rubber support (94) positioned adjacent to the battery terminals (62, 64), (iv) a lightweight fire-resistant enclosure composite panel, and (v) a rupturable diaphragm (36) configured to vent gases and ejecta from a battery cell experiencing a thermal event.

Description

Background of the Invention Technical Field

[0001] The present invention generally relates to devices for mitigating the propagation of thermal events between battery cells within a battery module assembly. A thermal event occurring within one of the battery cells may include the emission of flame, heat, and ejecta from the battery cell and may create a serious risk of initiating similar thermal events in adjacent battery cells within the same battery module or other battery modules within the same battery system. The mitigation device provides passive protection for the battery system and serves as a fault protection mechanism for other active protection systems that may be provided as part of the overall battery system. Background Art

[0003] The demand for alternative, environmentally friendly energy machines and equipment continues to surge. In particular, the demand for machines that rely on battery systems rather than more conventional power generation methods (such as by burning fossil fuels) to provide power for their operations has increased. Although electric vehicles and other machines that are conventionally driven by internal combustion engines are becoming more and more popular, many other types of vehicles that have used electric propulsion systems continue to rely on fossil fuel generators to provide the power required for their propulsion systems and other operating systems. These vehicles include cargo ships, ferries, airplanes, mining equipment, aviation ground service equipment, hyperloop pods, and locomotives. In addition to transportation applications, battery-powered power systems can also be used in many off-grid applications that currently rely on fossil fuel power generation, or rely on less stable clean energy sources such as solar and wind power.

[0004] Lithium-ion battery cells are preferred for many current power storage applications. However, the safety issues associated with the use of these battery cells are well known, and measures must be taken to ensure the safe operation of large battery systems using lithium-ion battery cells. A particular operational safety issue associated with the use of lithium-ion battery cells is thermal energy management. Lithium-ion battery cells release a large amount of heat during normal cell operation. The generation of this heat needs to be managed, and the system design should consider adequate cooling and / or heat dissipation so that the battery cells can operate efficiently and safely. If the battery cell overheats, it may cause a runaway chemical reaction within the battery cell, sometimes with very serious consequences. For example, a runaway battery cell may explode, catch fire, and / or eject hot gases or substances from it. The hot ejecta, gases, and flames may then spread to adjacent battery cells and cause further runaway of the battery cell, exacerbating an already serious condition.

[0005] Lithium-ion battery systems are typically equipped with multiple active monitoring and mitigation systems that continuously monitor a number of parameters relevant to the operation of the battery system and are operable to take steps to detect signs of the onset of an adverse thermal event and mitigate it before it becomes a problem. Such mitigation steps include taking the problematic unit offline, activating a fire extinguishing system and / or alerting a maintenance technician to inspect the problematic unit or module. However, some industry regulators require that passive backup or fail-safe systems be provided in the event that the active mitigation systems fail or become incapable. The Norwegian Maritime Authority is one such regulator, which requires that all battery-powered and hybrid vessels operating in its waters be equipped with passive protection systems.

[0006] Therefore, there is a need for devices that can be used with battery systems to provide protection and prevent the propagation of thermal events associated with the battery cells contained therein. Summary of the invention

[0007] According to one embodiment of the present invention, a prismatic battery cell is provided, comprising a compression sheath disposed around at least a portion of an outer cell box containing the contents of the battery cell. The compression sheath is operable to constrain hoop stresses acting on the cell box during thermal expansion of the battery. In a preferred embodiment, the outer cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing pairs of side wall segments. The compression sheath is disposed around the cell box and covers at least a portion of the planar surfaces and at least a portion of one of the pair of side wall segments. In a particularly preferred embodiment, there is at least one side wall segment of one of the pair of side wall segments that is not covered by the compression sheath and is configured to generate at least one predetermined point of failure of the cell box during a thermal event in the cell, through which ejecta and gas or flames are released from the cell.

[0008] According to another embodiment of the present invention, a method of constraining a prismatic battery cell including a cell box is provided, wherein the outer cell box contains the contents of the battery cell. In a preferred embodiment, the cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing pairs of side wall segments. The method includes applying a compression sheath to the cell box. In a specific preferred embodiment, the compression sheath is applied to cover at least a portion of one of the planes and at least a portion of one of the side wall segment pairs. Typically, the compression sheath is used to constrain hoop stresses acting on the cell box during thermal expansion of the cell. In a specific preferred embodiment, at least one side wall segment of one of the side wall segment pairs is left uncovered by the compression sheath, thereby generating at least one cell box failure predetermined point during a thermal event in the cell, through which ejecta, gas and / or flames are released from the cell.

[0009] According to another embodiment of the present invention, there is provided a prismatic battery cell comprising an outer cell box, wherein the outer cell box contains the contents of the battery cell. The cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing pairs of side wall segments. There is at least one cell flange, the at least one cell flange extending from one or more of the side wall segments. At least two terminals, the at least two terminals extending from one or more of the side wall segments. The at least two terminals are at least partially surrounded by the at least one cell flange. There is at least one strip of flexible, temperature resistant material, the at least one strip of flexible, temperature resistant material being disposed on and covering at least one side of the at least one cell flange.

[0010] According to another embodiment of the present invention, a method for protecting a battery cell from physical and thermal damage is provided. The battery cell includes an outer cell box containing the contents of the battery cell. The cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing pairs of side wall segments. At least one battery flange, the at least one battery flange extending from one or more of the side wall segments. At least two terminals, the at least two terminals extending from one or more of the side wall segments. The at least two terminals are at least partially surrounded by the at least one battery flange. The method includes placing at least one strip of flexible, temperature resistant material on at least one side of the at least one cell flange and covering the at least one cell flange.

[0011] According to another embodiment of the present invention, a battery module assembly is provided. In a preferred embodiment, the battery module assembly includes at least two battery cells and one or more of the following:

[0012] (i) a layered barrier material is disposed between two battery cells, the layered barrier material being configured to insulate and control, prevent or mitigate a thermal event occurring in at least one of the battery cells from propagating between the cells;

[0013] (ii) A battery module housing configured to accommodate a plurality of battery cells and comprising at least one composite panel including an outer metal layer, an inner layer of R4 grade sheet material, and at least one graphite carbon sheet therebetween.

[0014] (iii) one or more bus bars operable to connect a plurality of battery cells within the housing, and one or more bus bar shields configured to at least partially cover the one or more bus bars and shield electrical components located outside the one or more bus bars and within the channel from contacting the one or more bus bars during a thermal event associated with one or more of the plurality of battery cells; and

[0015] (iv) A battery module housing comprising a channel within the housing and at least one outlet interconnecting the channel with an environment outside the housing, wherein there is a rupturable membrane that generally covers the channel and blocks communication between the channel and the environment outside the housing.

[0016] In a preferred embodiment of the present invention, the layered barrier material comprises at least two anisotropic material sheets. At least one of the anisotropic material sheets is in direct face-to-face contact with one of the at least two battery cells, and at least another of the anisotropic material sheets is in direct face-to-face contact with another of the at least two battery cells. At least two anisotropic material sheets have high thermal conductivity in the in-plane direction and are operable to direct heat energy away from the surface of the cell contacted by the sheet. At least two anisotropic material sheets are operable to prevent and / or delay the penetration of flames from the battery cells contacted by at least two anisotropic material sheets in the direction toward at least one other battery cell. The layered barrier material optionally comprises at least one insulating material sheet having high thermal resistance, and preferably at least two insulating material sheets. When at least two insulating material sheets are presented, one of the at least two insulating material sheets is positioned to be in direct face-to-face contact with one of the at least two anisotropic material sheets, and the other of the at least two insulating material sheets is positioned to be in direct face-to-face contact with the other of the at least two anisotropic material sheets. The at least two sheets of thermally insulating material are operable to delay and / or impede the flow of heat originating from within one of the battery cells in a direction toward at least one other battery cell. The layered barrier material further includes a compliant material in compression positioned between the at least two sheets of anisotropic material and the optional at least two sheets of thermally insulating material. The compliant material is operable to maintain the at least two sheets of anisotropic material in direct face-to-face contact with the at least two battery cells, regardless of thermally induced volume changes experienced by the at least two battery cells during operation of the cells.

[0017] In a preferred embodiment of the present invention, the outer metal layer of the battery module housing composite panel includes aluminum, FR4 grade sheet material including woven fiberglass and epoxy resin laminate material. The composite panel at least partially defines a channel configured to direct ejecta and gas flows from a thermal event associated with one or more battery cells within the battery module housing toward an outlet formed in the housing.

[0018] In a preferred embodiment of the present invention, the busbar shield comprises a FR4 grade sheet material, more preferably a woven fiberglass and epoxy resin laminate. The function of the busbar shield is to prevent the wiring distributed in the housing channel from contacting one of the busbars and causing a short circuit. The insulation layer of the housing may be damaged by a thermal event associated with one or more battery cells.

[0019] According to another embodiment of the present invention, a battery module assembly is provided. The battery module assembly includes a battery module housing configured to accommodate a plurality of prismatic battery cells. One or more of the prismatic battery cells include an outer cell box, which contains the contents of the battery cell. The cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing side wall segment pairs. The compression sheath is disposed around the cell box and covers at least a portion of the surface of the plane and at least a portion of one of the side wall segment pairs. The compression sheath is operable to constrain the hoop stress acting on the cell box during thermal expansion of the cell. There is at least one side wall segment of one of the side wall segment pairs that is not covered by the compression sheath, and is configured to generate at least one cell box failure predetermined point during a thermal event in the cell, and releases ejecta, gas and / or flame from the battery through at least one cell box failure predetermined point; the battery module assembly further includes a layered barrier material, which is disposed between at least two of the plurality of prismatic batteries. The layered barrier material is configured to insulate and control or prevent a thermal event occurring in at least one of the battery cells from propagating between cells. The layered barrier material comprises at least two anisotropic material sheets. At least one of the anisotropic material sheets is in direct face-to-face contact with one of the at least two battery cells. At least another of the anisotropic material sheets is in direct face-to-face contact with another of the at least two battery cells. The layered barrier material optionally comprises at least one insulating material layer, preferably at least two insulating material layers. When at least two insulating material sheets are used, one of the at least two insulating material sheets is positioned in direct face-to-face contact with one of the at least two anisotropic material sheets, and the other of the at least two insulating material sheets is positioned in direct face-to-face contact with the other of the at least two anisotropic material sheets. The layered barrier material further comprises a compliant material in a compressed state located between the at least two anisotropic material sheets and the optional at least two insulating material sheets. The compliant material is operable to maintain the at least two anisotropic material sheets in direct face-to-face contact with the at least two battery cells.

[0020] According to another embodiment of the present invention, a battery module assembly is provided, which includes a battery module housing configured to accommodate a plurality of prismatic battery cells. One or more of the prismatic battery cells include an outer cell box, which contains the contents of the battery cell. The cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing side wall segment pairs. The compression cladding is arranged to surround the cell box and cover at least a portion of the surface of the plane and at least a portion of one of the side wall segment pairs. The compression cladding is operable to constrain the hoop stress acting on the cell box during thermal expansion of the cell. There is at least one side wall segment of one of the side wall segment pairs that is not covered by the compression cladding, and is configured to generate at least one cell box failure predetermined point during a thermal event in the cell, and ejecta and gas are released from the cell through at least one cell box failure predetermined point. One or more battery cells include at least one cell flange extending from one or more side wall segments and at least two terminals extending from one or more side wall segments. The at least two terminals are at least partially surrounded by at least one cell flange. There is at least one strip of flexible temperature resistant material disposed on at least one side of at least one cell flange and covering the same.

[0021] According to another embodiment of the present invention, a battery module assembly is provided, which includes a battery module housing configured to accommodate a plurality of battery cells and a layered barrier material disposed between at least two battery cells of the plurality of battery cells. The layered barrier material is configured to insulate and control or prevent a thermal event occurring in at least one of the battery cells from propagating between cells. The layered barrier material is configured to insulate and control or prevent a thermal event occurring in at least one of the battery cells from propagating between cells. The layered barrier material includes at least two anisotropic material sheets. At least one of the anisotropic material sheets is in direct face-to-face contact with one of the at least two battery cells. At least another of the anisotropic material sheets is in direct face-to-face contact with another of the at least two battery cells. The layered barrier material further includes at least two thermal insulation material layers. One of the at least two thermal insulation material sheets is positioned to be in direct face-to-face contact with one of the at least two anisotropic material sheets, and the other of the at least two thermal insulation material sheets is positioned to be in direct face-to-face contact with the other of the at least two anisotropic material sheets. The layered barrier material further includes a compliant material in a compressed state located between at least two sheets of thermally insulating material. The compliant material is operable to maintain at least two sheets of anisotropic material in direct face-to-face contact with at least two battery cells. Each of the plurality of battery cells includes an outer cell box containing the contents of the battery cell. The cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing pairs of side wall segments. At least one cell flange, at least one cell flange extending from one or more of the side wall segments. At least two terminals, at least two terminals extending from one or more of the side wall segments. The at least two terminals are at least partially surrounded by at least one cell flange. There is at least one strip of flexible, temperature-resistant material, at least one strip of flexible, temperature-resistant material disposed on at least one side of at least one cell flange and covering it.

[0022] According to another embodiment of the present invention, a battery module assembly is provided, which includes a battery module housing configured to accommodate a plurality of prismatic battery cells. One or more of the prismatic battery cells include an outer cell box, which contains the contents of the battery cell. The cell box presents a pair of opposing, substantially planar surfaces interconnected by opposing pairs of side wall segments. One or more prismatic battery cells further include a compression sheath, which is arranged to surround the cell box and cover at least a portion of the surface of the plane and at least a portion of one of the side wall segment pairs. The compression sheath is operable to constrain the hoop stress acting on the cell box during thermal expansion of the battery. There is at least one side wall segment of one of the side wall segment pairs that is not covered by the compression sheath, and is configured to generate at least one predetermined point of failure of the cell box during a thermal event in the cell, and ejecta and gas are released from the battery through at least one predetermined point of failure of the cell box. The battery module housing includes at least one composite panel, the at least one composite panel including an outer metal layer, an inner layer of FR4 grade sheet material, and at least one graphite carbon sheet positioned therebetween, the composite panel at least partially defining a channel configured to direct ejecta and gas flows from a thermal event associated with one or more battery cells within the battery module housing toward an outlet formed in the housing.

[0023] According to another embodiment of the present invention, a battery system is provided. The battery system includes a plurality of any battery modules described herein.

[0024] According to another embodiment of the present invention, there is provided a vehicle, the vehicle comprising one or more prismatic battery cells or battery modules or battery systems herein. In a preferred embodiment, the vehicle is a watercraft, such as a ship or a boat.

[0025] According to one embodiment of the present invention, a method for insulating battery cells in a battery module assembly including at least two battery cells is provided. The method includes positioning a layered barrier material between at least two battery cells. The layered barrier material is configured to insulate and control or prevent a thermal event occurring in at least one of the battery cells from propagating between cells. Positioning the layered barrier material includes placing a first anisotropic material sheet in direct face-to-face contact with one of at least two battery cells. The anisotropic material has high thermal conductivity in the in-plane direction and is operable to divert heat energy from the surface of the cell contacted by the sheet. The anisotropic material is operable to prevent and / or delay the penetration of flames originating from battery cells contacted by at least two anisotropic material sheets in a direction toward at least one other battery cell. Optionally, a first thermal insulation material sheet having a high thermal resistance is placed in direct face-to-face contact with the first anisotropic material sheet. The thermal insulation material is operable to delay and / or inhibit the flow of heat energy originating from one of the battery cells in a direction toward at least one other battery cell. The second sheet of anisotropic material is placed in direct face-to-face contact with another of the at least two battery cells; optionally, the second sheet of thermally insulating material is placed in direct face-to-face contact with the second sheet of anisotropic material. The compliant material is located between the first sheet of anisotropic material and the second sheet of anisotropic material and the optional sheet of thermally insulating material and is held in compression therebetween. The compliant material maintains the at least two sheets of anisotropic material in direct face-to-face contact with the at least two battery cells, regardless of thermally induced volume changes experienced by the at least two battery cells during battery operation.

[0026] According to an embodiment of the present invention, a battery module assembly is provided, which includes a battery module housing, a plurality of battery cells located in the battery module housing, and a layered barrier material in contact with adjacent battery cells. The battery module housing has a longitudinal axis extending the length of the battery module housing and a transverse axis perpendicular to the longitudinal axis. The layered barrier material includes at least two anisotropic material sheets. At least one of the anisotropic material sheets is in direct face-to-face contact with one of the battery cells, and at least another of the anisotropic materials is in direct face-to-face contact with at least another of the battery cells. The battery module housing is configured to apply a compressive force to the plurality of battery cells in a direction parallel to the transverse axis. A compressive force is also applied to the plurality of battery cells in a direction parallel to the longitudinal axis.

[0027] According to an embodiment of the present invention, a battery module assembly is provided, which includes a battery module housing, a plurality of battery cells located in the battery module housing, and at least one channel between the battery module housing and the plurality of battery cells. The at least one channel is configured to direct jets and gas flows from thermal events associated with one or more battery cells in the battery module housing toward an outlet formed in the housing. The rupturable diaphragm generally seals the outlet and is configured to open in response to a thermal event and allow communication between the channel and the outside of the housing. The rupturable diaphragm is also configured to prevent opening due to a thermal event outside the housing.

[0028] According to one embodiment of the present invention, a prismatic battery cell assembly is provided, which includes an outer cell box, at least one cell flange, at least two terminals, and a flexible temperature-resistant material bead disposed around the periphery of the cell box. The cell box has a pair of opposing, substantially planar surfaces interconnected by opposing pairs of sidewall segments. At least one cell flange, at least one cell flange extending from one or more of the sidewall segments. The at least two terminals extend from one of the sidewall segments and are at least partially surrounded by the at least one cell flange. The flexible temperature-resistant material bead is disposed around the periphery of most of the sidewall segments and covers at least a portion of at least one cell flange. The bead is operable to apply a compressive force to the outer cell box. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is an isometric view of a battery module assembly according to the present invention illustrating an end of the assembly including a rupturable diaphragm covering an outlet of a battery module housing;

[0030] Figure 2 is an isometric view of a battery module assembly illustrating ends of the assembly including various electrical connectors;

[0031] Figure 3 is a broken-away cross-sectional view of a battery module assembly with a portion of the assembly removed for ease of illustration;

[0032] Figure 4 is an isometric cross-sectional view of a battery module assembly illustrating a stack of battery cells contained within a battery module housing;

[0033] Figure 5 is an expanded view of a battery cell unit stack contained in a battery module housing;

[0034] Figure 6 is an expanded view of a battery cell according to one embodiment of the present invention;

[0035] Figure 7 is an isometric end view of the assembled battery cell; and

[0036] Figure 8 is an expanded view of another embodiment of a battery cell unit stack included within a battery module assembly.

[0037] Although the drawings do not necessarily provide exact dimensions or tolerances of the components or structures illustrated, the drawings are to scale according to the relationship between the components of the structures illustrated in the drawings. DETAILED DESCRIPTION

[0038] definition

[0039] As used herein, the term "battery cell" refers to an electrochemical cell that can generate electrical energy from a chemical reaction. A battery cell can be an electrolytic cell in which the cathode and anode are separated by an electrolyte. An exemplary battery cell for use with the present invention is a lithium-ion battery cell. There are many types of electrolytes that can be used in lithium-ion batteries, including but not limited to mixtures of organic carbonates such as ethylene carbonate or diethyl carbonate that contain lithium ion complexes. These non-aqueous electrolytes typically use non-coordinating anion salts such as lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate monohydrate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ) and lithium trifluoride (LiCF 3 SO 3 ). It should be noted that many of the concepts of the invention described herein may also be applicable to electrochemical devices and energy storage devices other than battery cell-based electrochemical devices and energy storage devices, including lithium ion capacitors and supercapacitors. For convenience, all such non-battery devices are encompassed by the term "battery cell" as used herein.

[0040] As used herein, the term "battery module" refers to a collection of two or more battery cells. The battery cells within a battery module may be connected in series, in parallel, or there may be cells connected in series and cells connected in parallel within the same module.

[0041] As used herein, the term "battery system" refers to a collection of two or more battery modules.

[0042] As used herein, the term "FR4 grade" refers to the National Electrical Manufacturers Association (NEMA) grade designation for certain composite materials, particularly flame retardant glass-reinforced epoxy laminates.

[0043] As used herein, the term "graphitic carbon" refers to a carbon allotrope having graphene as a basic structural element, including but not limited to graphite, carbon, carbon nanotubes, and fullerenes.

[0044] As used herein, the term "runaway event" refers to an uncontrolled exothermic chemical reaction occurring within a battery cell that may result in the release of heat, flames, gases, and / or other particulate matter (i.e., ejecta) from the cell. A runaway event is generally considered to be an extremely dangerous situation that may result in a fire and may propagate to other battery cells in the vicinity of the cell in which the event occurred.

[0045] Now go to Figure 1 and Figure 2 , illustrates an exemplary battery module assembly 10 according to an embodiment of the present invention. The battery module assembly 10 generally includes a battery module housing 12, in which a plurality of battery cells and other associated components are enclosed, the battery cells and components being described in more detail below. As shown, the housing 12 is rectangular in shape (although not always), and is constructed of six assembled panels. Panels 14 and 16 are typically the largest panels and are positioned relative to each other. One or more of the panels 14, 16 may include a heat transfer surface 18, the function of which is described in more detail below.

[0046] The housing 12 further includes a pair of opposed composite side panels 28, 30. The construction of the side panels 28, 30 will be described in further detail below. The side panels 28, 30 interconnect the panels 14, 16 along their longitudinally extending side edges. End panels 32, 34 are located transversely to the side panels 28, 30 and effectively serve as end caps for the housing 12. It can be observed that the end panel 32 can be equipped with a rupturable membrane 36, the function of which is explained below. The end panel 34 can include various electrical connectors to which power lines (not shown) and monitoring and control systems (not shown) can be attached and attached to the battery module 10.

[0047] One or more of the panels that make up the housing 12, and in particular panels 14, 16, 28, and 30, may comprise a lightweight metal such as aluminum to reduce the overall weight of the housing. However, other metals, such as steel, may also be used. In certain embodiments, panels 14, 16, 28, and 30 comprise a lightweight, high-strength material such as aluminum or carbon fiber.

[0048] In certain embodiments, it is preferred that once all panels are assembled, the housing 12 forms a substantially watertight structure that prevents or at least minimizes the ingress of moisture, dust, and / or other foreign matter into the interior of the housing. Likewise, except as explained below regarding the diaphragm 36, the housing 12 also prevents materials associated with or generated by the battery cells located within the housing from escaping in an uncontrolled manner. The housing 12 further includes a plurality of tie members 20 disposed circumferentially around the panels 14, 16, 28, and 30. The function of the tie members 20 is described in more detail below; however, in general, the tie members 20 provide a compressive force to the panels (particularly panels 14 and 16) with which they contact. The tie members 20 are preferably made of steel, but any suitable material may be used.

[0049] A plurality of battery modules 10 may be assembled together to form a battery system that is sized to meet the needs of a particular application. The battery system may include a rack or shelf unit (not shown) to which the battery modules 10 may be secured. The battery modules 10 may be connected in series and / or in parallel within the overall battery system, depending on the needs of a particular application.

[0050] Figure 3 The composite side panels 28, 30 are illustrated in greater detail. These panels are configured to provide enhanced protection from thermal events originating from within the battery cells contained within the housing 12. As explained in more detail below, the battery cells are specifically configured to discharge flames, gases, and other ejecta toward at least one of the side panels 28, 30 if a runaway thermal event occurs in the battery. Conventionally, panels exposed to such conditions are constructed of a single material sheet (such as steel) that is capable of withstanding the high temperatures associated with such thermal events. However, in certain applications, such materials are impractical because they add considerable weight to the battery module housing. Therefore, in certain embodiments of the present invention, the side panels 28, 30 are made of a composite material that is much lighter in weight but has sufficient heat-resistant properties to be used as housing panels.

[0051] The composite side panels 28, 30 include an outer metal or non-metal structural layer 38, an inner layer 40 and at least one graphite carbon sheet 42 therebetween. Preferably, the panels 28, 30 include a plurality of graphite carbon sheets 42 stacked together. In a preferred embodiment, the FR4 grade sheet material includes a woven fiberglass and epoxy resin laminate. In a particularly preferred embodiment, the FR4 grade material includes a (Garolite) material having a tensile strength of 241-345 MPa, an impact strength of 30-65.4 kg-cm / cm, a Rockwell hardness of M100 to M110, and a thickness of 0.127 mm to 2.54 cm.

[0052] The FR-4 grade sheet material is used as a flame barrier to prevent the flames ejected from the battery cells in the battery module 10 from penetrating. One or more graphite carbon sheets provide a thermal barrier to protect the outer metal layer 38 from temperatures that may cause it to melt. The graphite carbon sheet advantageously transfers heat in the in-plane direction rather than perpendicular to the plane of the sheet. Therefore, the graphite carbon sheet transfers the heat from the battery cell from the outer metal layer 38. In some embodiments, the outer metal layer 38 includes a lightweight metal or metal alloy. Preferably, the structural layer 38 includes aluminum, aluminum alloy, carbon fiber or synthetic resin material. The laminated structure of the side panels 28 and 30 allows the use of lightweight, relatively low melting point metals (such as aluminum) in the construction of the battery module housing 12 to save a lot of weight, which can be a huge advantage, especially when the battery module 10 is installed in a vehicle, weight is an important design consideration.

[0053] The composite panels 28, 30 at least partially define respective channels 44 within the enclosure 12 that are configured to direct ejections and gas flows from a thermal event associated with one or more battery cells within the enclosure 12 toward respective outlets 46 formed in the enclosure. Note that the battery module 10 illustrated in the accompanying drawings utilizes battery cells that are configured to fail in the direction of the composite side panels 28 and 30. Thus, the enclosure 12 is configured with channels 44 at each end of the battery cell stack to direct ejections and gases toward respective outlets 46. However, it is also within the scope of the present invention for the battery module 10 to utilize battery cells that are configured to fail in only one direction, thus requiring the use of only one composite side panel 28, one channel 44, and one outlet 46.

[0054] As shown, an outlet 46 is formed in the end panel 32 so that hot gases and ejecta are conducted away from the various electrical components carried by the end panel 34. The diaphragm 36 generally seals the outlet 46 and is configured to open and allow communication between the channel 44 and the outside of the housing 12 in response to a thermal event. In certain embodiments, the diaphragm 36 is formed of a synthetic resin film material such as silicone rubber, KAPTON (polyimide), TEFLON & GORE-TEX (polytetrafluoroethylene), etc. However, other materials such as thin metal foils are also within the scope of the present invention for use as the diaphragm 36. In one aspect of the present invention, the diaphragm 36 acts as a one-way valve that ruptures under the pressure of a thermal event occurring within the module 10, but has sufficient heat resistance to avoid rupture and discharge due to a thermal event occurring in an adjacent module in close proximity thereto. Therefore, the diaphragm 36 can also protect the module 10 from external dangers and help mitigate dangers within the module 10.

[0055] Reference now Figure 4 and Figure 5, the battery module 10 includes a plurality of battery cells 48. As shown, the battery cells 48 include prismatic battery cells, but other types of battery cells used with many of the features disclosed and described herein are within the scope of the present invention. However, typically, the prismatic battery cells are placed within a unit frame 50. Multiple frames 50 are stacked together and fixed by inserting screws 52 into apertures 54 formed in the corner portions 56 of each frame. The frame 50 is typically rigid and made of an inert material such as a synthetic resin or a thermoplastic material. The preferred material for constructing the frame 50 is acrylonitrile-butadiene-styrene (ABS), although any suitable thermoplastic material may be used. Once the desired number of units 48 are stacked together, the end plates 58 are attached and fixed to the screws 52 using nuts 60. However, other devices including cables and bands may be used to fix the unit stacks together.

[0056] Each battery cell 48 includes at least two terminals 62, 64 extending therefrom (see Figure 6 ). As shown, one terminal extends from the opposite end of the cell 48, although it is also within the scope of the present invention for the terminals 62, 64 to extend from the same end of the battery. The battery module assembly 10 includes one or more bus bars 66 that are operable to connect the plurality of battery cells 48 located within the housing 12. The bus bar 66 is preferably formed of any conductive material, such as copper or aluminum, and includes a slot 68 configured to receive the terminals 62, 64.

[0057] Note that the channel 44 may carry wiring and / or other electrical components used by the battery module assembly. Once a thermal event occurs, the flames, jets, and gases exhausted from the battery cells 48 may damage the wire insulation, thereby exposing the bare wires of these components. Since the busbars generally face the channel 44, if the bare wires and the busbars come into contact, a short circuit may be generated, thereby introducing further dangers in an already dangerous situation, such as triggering another out-of-control unit. Therefore, in certain embodiments of the present invention, one or more busbar shields 70 may be installed on the busbars 66 to at least partially cover the one or more busbars 66 and prevent the electrical components located outside the one or more busbars 66 and within the channel 44 from contacting the one or more busbars 66 during a thermal event associated with one or more battery cells 48. In certain embodiments, the busbar shield 70 is formed of a fire-resistant material (preferably such as the FR4 grade sheet material described above) and is used with the composite side panels 28, 30. The busbar shield 70 may also operate to prevent the flame escaping from one battery cell 48 from contacting an adjacent battery cell.

[0058] Figure 6 and Figure 7An exemplary battery cell 48 that may be used with embodiments of the present invention is illustrated in greater detail. However, as previously stated, other types and configurations of battery cells to be used are within the scope of the present invention, and the drawings and accompanying descriptions should not be construed as limiting the scope of the present invention in any way.

[0059] The battery cell 48 includes an outer cell box 72, which contains the contents of the battery cell, such as a cathode, an anode, and an electrolyte. In some embodiments, the cell box includes a bag formed by a membrane material (such as a polymer / aluminum composite material that is hermetically sealed on at least one side). The cell box 72 presents a pair of opposing, substantially planar surfaces 74, 76. In some embodiments, the surfaces 74, 76 constitute the vast majority of the surface area of ​​the cell box. These planar surfaces 74, 76 are interconnected by opposing side wall segments 78, 80, 82, 84. The side wall segments 78, 80 extend parallel to the longitudinal axis of the battery cell 48, and the side wall segments 82, 84 extend transversely to the longitudinal axis of the battery cell 48. Some housing materials may extend beyond one or more side wall segments 78, 80, 82, 84 in the form of a flange structure 86. The flange structure 86 is typically a byproduct of the manufacture of the cell box 72 and may be generated when the film material constituting the cell box 72 is sealed. As shown, the flange structure 86 extends circumferentially around the perimeter of the battery cell 48, although this is not always the case. In certain embodiments, the terminals 62, 64 extend through portions of the flange structure 86 and are at least partially covered thereby.

[0060] In a preferred embodiment of the present invention, a compression cladding 88 is provided around the cell box 72, covering at least a portion of the planes 74, 76 and at least a portion of one of the side wall segments 78, 80, 82, 84. In a particularly preferred embodiment, the compression cladding is composed of two overlapping plies 88 of a self-adhesive sheet material. In a particularly preferred embodiment, the sheet material is a glass fiber reinforced membrane coated with an adhesive on one side thereof. However, a compression cladding 88 composed of a single ply or multiple plies and an adhesive applied separately rather than an integral part of the membrane material constituting the cladding belong to the scope of the present invention. Regardless of the form adopted, the compression cladding 88 is operable to constrain the hoop stress acting on the cell box 72 during thermal expansion of the cell 48. As indicated, it is common to generate heat during normal operation of the lithium-ion cell. This heat will cause the contents of the cell box 72 and the cell box itself to expand. The uncontrolled expansion of the cell box 72 may cause the battery box 72 to fail unpredictably during an adverse thermal event in the cell 48. It is an object of certain embodiments of the present invention to prevent unpredictable failure of the cell box 72 so that the emission of the released flames, gases and ejecta can be effectively managed by other anti-propagation features described herein. Therefore, although in most embodiments of the present invention, most of the cell box 72 is covered by the compression envelope 88, at least a portion of the battery box 72, in particular at least a portion of one of the side wall segments 78, 80, 82 and 84, is not covered, so that at least one cell box failure predetermined point is generated, and during a thermal event in the battery 48, ejecta and gases and possible flames are released from the battery through this point. In certain embodiments, at least one cell box failure predetermined point is located in the same side wall segment (i.e., side wall segments 82 and 84) through which the terminals 62 and 64 extend. Preferably, the cell box failure predetermined point 92 is located near the intersection of adjacent side wall segments, and at least one cell box failure predetermined point is formed in each of the uncovered side wall segments 82, 84. Thus, the compression cladding 88 is configured to prevent the failure of the unit box 72 at any location on the unit box covered by the compression cladding 88 before failure occurs at at least one predetermined failure point 92. In certain embodiments, the material constituting the compression cladding 88 has a tensile strength of at least 2.5 MPa, and preferably from 2.5 to 10 MPa, from 3 to 9 MPa, from 4 to 8 MPa, or from 5 to 7 MPa. The material constituting the compression cladding must maintain these mechanical properties when exposed to a heat source in excess of 700°C, preferably at normal operating temperatures of -40°C to 60°C, and when exposed to a heat source of 60°C to 900°C.

[0061] Optionally, a protective wrap 90 may be applied atop the compression wrap 88. In certain embodiments, the protective wrap 90 comprises a heat shrinkable plastic sleeve that is placed around the battery cell 48. The sleeve is then heated to shrink the wrap 90 around the cell 48. Generally, the protective wrap 90 may provide some additional reinforcement to the cell box 72. However, the protective wrap 90, particularly when used with a battery cell box 72 that includes an aluminum composite film, provides a barrier to any exposed conductive cell box material to prevent corrosion or degradation of the conductive cell box material, thereby helping to maintain the structural integrity of the cell box and preventing the creation of unexpected weak points that could become dangerous issues.

[0062] The present invention further includes a method of constraining a prismatic battery cell 48 including a cell box 72 containing the contents of the battery cell therein. The method includes applying a compression blanket 88 to the cell box 72, covering at least a portion of the planar surfaces 74, 76 and at least a portion of one of the side wall segment pairs 78, 80, 82, 84. At least one side wall segment is not covered by the compression blanket, thereby creating at least one cell box failure predetermined point 92.

[0063] In certain embodiments of the present invention, the battery cell 48 includes at least one strip 94 of flexible, temperature-resistant material disposed on at least one side of the cell flange 86 surrounding each terminal 62, 64 and covering the cell flange 86. Preferably, the strip 94 comprises a silicone rubber material, but it may be formed of any flexible material capable of maintaining its structural integrity when exposed to high temperatures (e.g., temperatures in excess of 300° C.). The strip 94 may include a substantially uniform cross-sectional profile (i.e., exhibiting a uniform thickness), or it may be configured with a variable profile. Figure 6 As shown, preferably, the strip 94 includes a central portion 98 that at least partially covers the terminals 62, 64 and outer portions 100, 102 that are disposed transversely from the central portion. In addition, the thickness of the central portion 98 may be greater than the thickness of the outer portions 100, 102. In some embodiments, the thickness of the central portion 98 is at least 1.5 times the thickness of the outer portions 100, 102. The width of the central portion 98 also does not need to be as wide as the width of the strip 94. As shown, the width of the raised central portion 98 is less than the width of the strip 94, so that the unraised segment 99 is located next to the central portion 99 and in the middle of the outer portions 100, 102. In some embodiments, the thickness of the unraised segment 99 is substantially equal to the thickness of the outer portions 100, 102. In addition, the central portion 98 may also include a segment 101 that extends beyond the edge 103 of the outer portions 100, 102. The segment 101 provides enhanced support for the portion of the terminals 62, 64 that extends beyond the unit flange 86.

[0064] In certain embodiments of the present invention, the cell flange 86 extends along the entire length of one of the side wall segments 82, 84 from which at least one of the terminals 62, 64 extends. The strip 94 preferably also extends along the entire length of these side wall segments. Preferably, the strip 94 does not encroach on or overlap the battery compartment planes 74, 76. Instead, the strip 94 resides completely outside the edges of these surfaces and outside the edges that define the side wall segments 82, 84, although this is not always the case.

[0065] In one aspect, Figure 5 As can be seen, when multiple battery cells 48 are assembled into the battery module assembly 10, the strips 94 and the center portion 98 in particular provide support and mechanical protection for the terminals 62, 64 and prevent physical damage thereto due to movement or vibration of the battery module assembly, such as when transported or installed in a vehicle. However, as explained below, the strips 94 can provide a secondary function, namely, directing flames, jets, and gases as they are vented through the cell box failure predetermined point 92 during an uncontrolled thermal event, and preventing these materials from spilling over onto adjacent battery cells 48 within the module 10. In addition, the strips 94 also provide protection for the battery cells 48, in particular the sidewall segments 82, 84 from which the terminals 62, 64 extend, from flames, jets, and gases originating from outside the battery cell 48 to which the strips 94 are applied. Thus, the strips 94 act in some respects as a one-way valve, allowing gases, flames, and jets originating from within the battery cell 48 to escape, but preventing the same materials emitted from different battery cells from entering. It has been discovered that the strips 94 are configured to char rather than burn when exposed to, for example, a flame (or temperature of approximately 700° C.) originating from outside the battery cell 48. This charring of the strips 94 isolates the battery cell 48 and helps prevent the propagation of a thermal event originating from outside the battery cell 48 to cause another dangerous thermal event within the battery cell 48.

[0066] In certain embodiments, the cell box failure point 92 is located inboard of the strap 94 so that flames, ejecta, and gases that may be generated by the cell 48 during an uncontrolled thermal event are vented from the cell below the strap rather than above the strap. Thus, the strap 94 serves to direct these materials in a direction coaxial with the longitudinal axis of the battery cell 48 and toward one of the composite side panels 28, 30. Lateral transmission of flames, ejecta, and gases to adjacent battery cells within the battery module 10 is minimized or avoided entirely.

[0067] Embodiments of the present invention also provide methods of protecting battery cells 48 from physical and thermal damage by placing at least one strip of flexible, temperature resistant material 94 on at least one side of at least one cell flange 86 around terminals 62, 64 and covering thereon as described above.

[0068] In certain embodiments of the present invention, a layered barrier material 104 is provided as part of the battery module assembly 10 to insulate and control or prevent a thermal event occurring within at least one of the battery cells 48 from propagating between cells. The layered barrier material 104 is preferably Figure 5 As shown, the barrier material 104 is located between the cells 48 that make up the battery module assembly 10. Preferably, the barrier material 104 includes at least two anisotropic material sheets 106, 107, which have high thermal conductivity in the in-plane direction (opposite to the direction perpendicular to the sheet). In a preferred embodiment, the anisotropic materials 106, 107 include graphite carbon, more preferably graphite.

[0069] One anisotropic material sheet 106 is in direct face-to-face contact with one battery cell 48. Preferably, the anisotropic material sheet 106 is sized to substantially cover the cell box plane surface 74 when placed in direct contact with the cell box plane surface 74 (or in contact with any coating or film fixed to the cell box as described above). Another anisotropic material sheet 107 is placed in direct face-to-face contact with another battery cell 48 adjacent to the first battery cell. Similarly, another anisotropic material sheet 107 is preferably sized to substantially cover the cell box plane surface 76 of the other battery cell 48 when placed in direct contact with the other battery cell 48. The anisotropic materials 106, 107 are operable to direct heat energy away from the cell surfaces 74, 76 in contact therewith. Preferably, the anisotropic materials 106, 107 conduct a large amount of heat energy from the cell to the peripheral edges of the sheets 106, 107, rather than conducting heat energy in a direction perpendicular to the sheets 106, 107 and toward the adjacent cells 48. Additionally, the anisotropic materials 106, 107 may also operate to prevent and / or delay the penetration of flames originating from a battery cell 48 in contact with the anisotropic materials 106, 107 in a direction toward another adjacent battery cell. This flame barrier property helps protect and maintain the functionality of the other layers that make up the layered barrier material 104, as described below. The anisotropic heat conduction and flame barrier functions may be performed by a single material or multiple materials.

[0070] As shown, the layered barrier material 104 further includes at least two insulating material sheets 108 having high thermal resistance. Note that in certain embodiments of the present invention, the insulating material 108 is optional, or only one insulating material sheet 108 may be used. Therefore, the following description should not be considered to limit the overall scope of the present invention. In certain embodiments, the insulating material 108 does not provide meaningful structural support to the layered barrier material 104 or any other part of the battery module assembly 10, and is completely flexible in response to the force applied to it by other parts of the layered barrier material. When exposed to temperatures exceeding 800°C, the insulating material 108 maintains its insulating properties. In certain embodiments, the insulating material 108 also remains dimensionally stable when exposed to heat and pressure. In particular, this means that the thickness of the insulating material does not change substantially when placed under compressive forces or during normal battery operation or during temperature fluctuations that may be experienced during thermal events. In preferred embodiments, the insulating material comprises cork, wool, or fiberglass. The thermal insulation material 108 is operable to delay and / or hinder the flow of heat energy originating within one of the battery cells 48 in a direction toward at least one other adjacent battery cell. Note that the heat energy that is hindered may originate from a cell 48 located proximal or distal to the thermal insulation material 108. The anisotropic material sheet 106 also has the same directional functionality, although its most effective thermal barrier properties will be for the cell 48 that it is in contact with.

[0071] One sheet of insulating material 108 is positioned in direct face-to-face contact with one sheet of anisotropic material 106, and the other sheet of insulating material 108 is positioned in direct face-to-face contact with the other sheet of anisotropic material 106. Preferably, the sheet of insulating material 108 is sized to correspond to the sheet of anisotropic material 106, and in particular, the sheet of anisotropic material 106 substantially covers the sheet of insulating material when in direct abutting contact with the sheet of insulating material. In certain embodiments, the sheet of anisotropic material 106 may include strips 110 extending transversely from respective longitudinal side edges of the sheet. When placed in direct face-to-face contact with the insulating material 108, the strips 110 cover the longitudinal side edges of the insulating material 108, thereby "nesting" the insulating material 108 within the sheet of anisotropic material 106.

[0072] The layered barrier material 104 further includes a compliant material 112 positioned between at least two sheets of insulating material 108. Preferably, when the compliant material 112 is positioned between the sheets of insulating material 108, the compliant material 112 is in a compressed state, meaning that it is compressed and / or reduced in volume from its natural or unconstrained state, such that internal forces acting within the compliant material 112 bias the material toward the unconstrained state. For example, when the battery cell stack 49 is assembled and the end plate 58 is secured to the end of the stack by the screw 52 and the nut 60, the compliant material 112 may be compressed. As previously described, other devices (such as belts or cables) may be used to provide the compressive force. In a preferred embodiment, the compliant material comprises polyurethane, EPDM, PVC, or silicone foam. The compliant material 112 must have high compressibility (down to 25% of its original thickness) without being permanently deformed by compression. When exposed to heat sources in excess of 700°C, preferably at normal operating temperatures of -40°C to 60°C and when exposed to heat sources in the range of 60°C to 900°C, forces must continue to be applied to the insulating material and the anisotropic material. In certain aspects of the invention, the compliant material 112 is operable to maintain the anisotropic materials 106, 107 in direct facing contact with the battery cells 48, regardless of the thermally induced volume changes that the battery cells may experience during normal cell operation. In addition, by assembling in a compressed state, if the compliant material 112 itself undergoes a volume change due to temperature changes within the battery module assembly 10, the internal forces acting in the outward direction within the compliant material are sufficient to eliminate any gaps or air pockets that may form between the battery cells 48 and the sheets 106, 107. The strips of anisotropic material 106 may also be configured to extend over and cover the longitudinal side edges of the compliant material 112, such that the compliant material is also nested within the sheet 106.

[0073] The anisotropic material sheet 107 may also be provided with a slat 113 extending transversely from the respective longitudinal side edges of the sheet. In certain embodiments, the slat 113 is larger than the slat 110 and is configured to extend at least partially over and cover the side wall segments 78, 80 of the battery cell 48. The side wall segments 78, 80 may also have an elongated spacer 114 applied to at least a portion thereof. When the battery cells 48 are stacked and assembled, the spacer 114 is located between the side wall segments 78, 80 and the slat 113.

[0074] refer to Figure 2, noting that the battery module housing 12 has a longitudinal axis XX extending the length of the battery module housing and a transverse axis YY perpendicular to the longitudinal axis. In certain embodiments of the present invention, the battery module assembly 10 is configured so that the battery cells residing therein are subjected to compressive forces in directions parallel to the axes XX and YY. As discussed above, the compressive force in the direction parallel to the axis XX can be provided by a layer of compliant material 112 dispersed between the individual battery cells. This compressive force can also be applied by other means, including bundling the cell stack 49 together. The compressive force maintains the anisotropic material sheets 106, 107 in direct facing contact with the battery cells 48 to ensure that thermal energy can be conducted away from the battery cells 48 through the sheets 106, 107. The strap 20 is located around the battery module housing 12 and is configured to apply a compressive force to at least the panels 14 and 16 in a direction parallel to the axis YY. It is noted that other structures can be used instead of the strap 20 to provide compressive forces to the panels 14, 16, and the illustrated embodiments should not be considered limiting.

[0075] like Figure 3 As shown, the compressive force keeps the panels 14 and 16 in contact with the slats 110 and / or 113 of the anisotropic material sheets 106, 107. The panels 14, 16, and possibly the entire battery module housing, can be configured to act as a heat sink to conduct heat energy transmitted to the battery cells 48 away from the battery cells 48 via the anisotropic material sheets 106, 107. In order to effectively achieve this, the slats 110 and / or 113 should remain in continuous direct contact with the panels 14, 16. Therefore, features of certain embodiments of the present invention compress the battery cell stack in at least two planes so that the anisotropic material sheets remain in continuous contact with the battery cells 48 and the panels 14, 16 of the housing 12. Therefore, the anisotropic material sheets 106, 107 can be considered as devices for conducting heat energy away from the battery cells 48 and transferring the heat energy to the battery module housing 12.

[0076] The layered barrier material 104 need not be located between all adjacent battery cells 48. In some embodiments, there may be two, three, four, or any number of cells located between each layer of the layered barrier material 104. Figure 5 As shown, the battery cell stack 49 can be composed of a plurality of repeating battery cell units 116. Each unit includes at least two unit frames 50, at least two battery cells 48, and at least one layered barrier material 104. Note that, as shown in FIG. Figure 5 As shown, the unit frames 50 are oriented in a mirrored format, rather than facing the same direction. Between adjacent unit units 116, one or more anisotropic material sheets 107 may be placed. In a preferred embodiment, the anisotropic material sheets 106, 107 are oriented so that the slats 110, 113 all extend away from their respective sheets in the same direction.

[0077] Figure 8 Another embodiment of the present invention is illustrated. In this embodiment, a stack 118 of battery cells 120 is assembled. The stack 118 is similar to the stack 49 described above in many respects, and for convenience, these commonalities are not repeated in detail below, but can be clearly seen from the accompanying drawings. Similar to the stack 49, the stack 118 is suitable for being placed in a battery module housing 12 having housing panels 14, 16 as described above. The battery cell 120 is a prismatic battery cell having a pair of terminals 121 extending from the same side wall segment and at least partially surrounded by a flange 86. The battery cell 120 is placed in a battery cell frame 50, which is fixed together in the form of a plurality of repeating battery cell units 122. The battery cell unit 122 includes at least two battery cells 120 with a layered barrier material 104 located therebetween. The layered barrier material 104 can be configured as described above and includes anisotropic material sheets 106, 107, an optional thermal insulation material sheet 108, and at least one layer of compliant material 112.

[0078] Each battery cell 120 further includes a bead 124 of a flexible, temperature resistant material disposed around the periphery of a majority of the battery cell sidewall segments. The bead 124 may include the same material used to construct the flexible strip 94 described above. The bead 124 covers at least a portion of the battery flange 86 and is operable to apply a compressive force to the outer cell box, particularly the sidewall segments, to constrain the sidewall segments and prevent the cell box from rupturing at unintended points along the individual sidewall segments. The bead 124 may be continuous (i.e., as described above). Figure 8 The bead 124 may be one piece (as shown) or discontinuous (i.e., composed of discrete segments) and are placed around the unit 120. In certain embodiments, the bead 124 may have one or more recessed areas 126 or areas of reduced thickness. The recessed area 126 represents a controlled battery case rupture corresponding to the battery case failure predetermined point 92 during a thermal event. Therefore, preferably, the bead 124 provides support and reinforcement for most of the circumference of the sidewall segment, except for the portion corresponding to the recessed area 126. Note that in the case of a discontinuous bead, the recessed area 126 may actually be free of any bead material.

[0079] In some embodiments, the battery cell 120 is not reinforced with a compression wrap 88 as the battery cell 48 is. Thus, in addition to performing a vibration protection function for the terminal 121 and a flame barrier for preventing the ingress of flames originating from outside the cell 120, the bead 124 is also configured to constrain the cell sidewalls by providing a compressive force to the cell sidewalls. The compressive force provided by the bead 124 strengthens the cell box and prevents the cell box from failing at locations other than the predetermined point 92.

[0080] Generally speaking, the battery cell stack 118 replaces the cell stack 49 and is placed within a battery module housing 12 configured as described above, and except as described above, the operation of such a battery module 10 remains the same as previously described.

[0081] Embodiments of the present invention also provide a method of thermally insulating battery cells 48 within a battery module assembly 10. The method includes positioning a layered barrier material 104 between at least two adjacent battery cells 48. Positioning the layered barrier material 104 includes placing a first anisotropic material sheet 106 in direct face-to-face contact with the first battery cell 46, placing a first thermally insulating material sheet 108 in direct face-to-face contact with the first anisotropic material sheet 106, placing a second anisotropic material sheet 106 in direct face-to-face contact with the second battery cell, placing a second thermally insulating material sheet 108 in direct face-to-face contact with the second anisotropic material sheet 106, and positioning a compliant material 112 between the first and second thermally insulating material sheets 108. The compliant material 112 is held under compression between the first and second thermally insulating material sheets 108.

[0082] The battery module assembly 10 may have a variety of applications. In a preferred application, a plurality of battery module assemblies 10 may be provided in a stack or cabinet, or even a plurality of battery module assembly cabinets may be provided to form a battery system. The battery module assembly 10 or a battery system comprising a plurality of battery module assemblies may be used to power a vehicle such as a car, truck, ship, airplane, hyperloop pod, mining equipment, aviation ground service equipment, or locomotive. A preferred application of the battery module assembly 10 is for use in a battery system installed in a ship. The ship may be a cargo ship, a passenger ship, a ferry, a hovercraft, a warship, or the like. In addition, a battery system including a battery module assembly 10 may be the only power source provided on a ship, or may be provided as a component of a hybrid power system. A battery system including a battery module assembly 10 may be used to provide propulsion for a vehicle, or to power other onboard vehicle systems, or both.

[0083] It should be understood that the present invention may be practiced using one or more of the various features and elements described herein. The embodiments shown in the drawings and described above show combinations of elements assembled in a particular manner, and this fact should not be considered to limit the scope of the present invention, nor should it be considered to require that all of the features or elements be present in order to successfully practice the present invention.

Claims

1. A battery module assembly, comprising: A plurality of prismatic battery cells, each prismatic battery cell comprising: cathode; anode; Electrolytes; an outer cell box, wherein the cathode, the anode, and the electrolyte are contained within the outer cell box, the cell box presenting a pair of opposing, substantially planar surfaces interconnected by a pair of opposing sidewall segments; and a compression sheath disposed around the cell box and covering at least a portion of the surface of the planar surface and at least a portion of one of the pair of sidewall segments, the compression sheath being operable to constrain hoop stresses acting on the cell box during thermal expansion of the battery cell, There is at least one side wall segment of one of the pair of side wall segments not covered by the compression envelope and configured to generate at least one predetermined point of cell box failure during a thermal event in the battery cell through which ejecta and gas are released from the battery cell; a battery module housing configured to house the plurality of prismatic battery cells; and a layered barrier material disposed between at least two of the plurality of prismatic battery cells, the layered barrier material being configured to insulate and control or prevent a thermal event occurring within at least one of the battery cells from propagating between cells, the layered barrier material comprising: (i) at least two anisotropic material sheets, at least one of the anisotropic material sheets is in direct face-to-face contact with one of the at least two battery cells, and at least another of the anisotropic material sheets is in direct face-to-face contact with another of the at least two battery cells, (ii) at least two sheets of thermally insulating material, one of the at least two sheets of thermally insulating material being positioned in direct face-to-face contact with one of the at least two sheets of anisotropic material, and the other of the at least two sheets of thermally insulating material being positioned in direct face-to-face contact with the other of the at least two sheets of anisotropic material; and (iii) a compliant material positioned in a compressed state between the at least two sheets of thermally insulating material, the compliant material being operable to maintain the at least two sheets of anisotropic material in direct face-to-face contact with the at least two battery cells.

2. The battery module assembly according to claim 1, characterized in that: The compression blanket prevents the unit box from failing at any location on the unit box covered by the compression blanket before the unit box fails at the at least one unit box failure predetermined point.

3. The battery module assembly according to claim 1, characterized in that: The compression envelope comprises a tensile strength of 2.5 MPa.

4. The battery module assembly according to claim 1, characterized in that: The compression blanket comprises a self-adhesive fiberglass reinforced membrane.

5. The battery module assembly according to claim 1, wherein: The at least one predetermined point of unit box failure is located at the intersection of two adjacent side wall segments.

6. The battery module assembly according to claim 1, wherein: There are two side wall segments of one of the side wall segment pair that are not covered by the compressed envelope, and at least one unit box failure predetermined point is formed in each of the side wall segments of one of the side wall segment pair.

7. The battery module assembly according to claim 1, wherein: The battery cells are lithium-ion battery cells.

8. The battery module assembly according to claim 1, wherein: The battery module housing includes at least one composite side panel, which includes an outer metal or non-metallic structural layer, an inner layer of FR4 grade sheet material, and at least one graphite carbon sheet located therebetween, wherein the composite panel at least partially defines a channel, which is configured to direct ejecta and gas flows from thermal events associated with one or more battery cells within the battery module housing toward an outlet formed in the battery module housing.

9. The battery module assembly according to claim 8, wherein: The battery module housing further includes at least one end panel positioned laterally relative to the composite side panel, the outlet being formed in the at least one end panel, and wherein the outlet is covered by a rupturable membrane configured to open in response to the thermal event and allow communication between the channel and the exterior of the housing.

10. The battery module assembly according to claim 8, characterized in that: The battery module assembly further includes one or more bus bars operable to connect the plurality of battery cells within the housing, and The battery module assembly further includes one or more busbar shields configured to at least partially cover the one or more busbars and shield electrical components located outside the one or more busbars and within the channel from contacting the one or more busbars during a thermal event associated with one or more of the plurality of battery cells.

11. The battery module assembly according to claim 8, characterized in that: Each of the plurality of battery cells comprises at least one cell flange extending from one or more of the side wall segments, and at least two terminals extending from one or more of the side wall segments, wherein the at least two terminals are at least partially surrounded by the at least one cell flange, and there is at least one flexible, temperature-resistant material strip disposed on at least one side of the at least one cell flange and covering at least one side of the at least one cell flange.

12. A method of thermally insulating a battery cell in a battery module assembly comprising at least two battery cells, the method comprising: positioning a layered barrier material between the two battery cells, the layered barrier material being configured to thermally insulate and control or prevent a thermal event occurring within at least one of the battery cells from propagating between the cells, Wherein positioning the layered barrier material comprises: (i) placing a first sheet of anisotropic material in direct face-to-face contact with one of the at least two battery cells, the anisotropic material having a high thermal conductivity in an in-plane direction and operable to direct thermal energy away from a surface of the battery cell contacted by the first sheet of anisotropic material, the anisotropic material operable to prevent and / or delay the penetration of a flame originating from the battery cell contacted by the anisotropic material sheet in a direction toward at least one other battery cell; (ii) placing a first sheet of thermally insulating material having a high thermal resistance in direct face-to-face contact with the first sheet of anisotropic material, the thermally insulating material being operable to delay and / or impede the flow of heat originating within one of the battery cells in a direction toward the at least one other battery cell; (iii) placing a second anisotropic material sheet in direct face-to-face contact with another of the at least two battery cells; (iv) placing a second sheet of thermally insulating material in direct face-to-face contact with the second sheet of anisotropic material; and (v) positioning a compliant material between the first sheet of thermally insulating material and the second sheet of thermally insulating material and maintaining the compliant material under compression between the first sheet of thermally insulating material and the second sheet of thermally insulating material, the compliant material maintaining the first sheet of thermally insulating material and the second sheet of thermally insulating material in direct facing contact with the at least two battery cells regardless of thermally induced volume changes experienced by the at least two battery cells during normal cell operation.

13. The method according to claim 12, characterized in that The compliant material includes polyurethane, EPDM, PVC or silicone foam. 14 . A vehicle, comprising the battery module assembly according to claim 1 .

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