Patent Description:
A vehicle that uses one or more battery systems for providing all or a portion of the motive power for the vehicle can be referred to as an xEV, where the term "xEV" is defined herein to include all of the following vehicles, or any variations or combinations thereof, that use electric power for all or a portion of their vehicular motive force. For example, xEVs include electric vehicles (EVs) that utilize electric power for all motive force. As will be appreciated by those skilled in the art, hybrid electric vehicles (HEVs), also considered xEVs, combine an internal combustion engine propulsion system and a battery-powered electric propulsion system, such as <NUM> Volt (V) or 130V systems. The term HEV may include any variation of a hybrid electric vehicle. For example, full hybrid systems (FHEVs) may provide motive and other electrical power to the vehicle using one or more electric motors, using only an internal combustion engine, or using both. In contrast, mild hybrid systems (MHEVs) disable the internal combustion engine when the vehicle is idling and utilize a battery system to continue powering the air conditioning unit, radio, or other electronics, as well as to restart the engine when propulsion is desired. The mild hybrid system may also apply some level of power assist, during acceleration for example, to supplement the internal combustion engine. Mild hybrids are typically 96V to 130V and recover braking energy through a belt or crank integrated starter generator. Further, a micro-hybrid electric vehicle (mHEV) also uses a "Stop-Start" system similar to the mild hybrids, but the micro-hybrid systems of a mHEV may or may not supply power assist to the internal combustion engine and operates at a voltage below 60V. For the purposes of the present discussion, it should be noted that mHEVs typically do not technically use electric power provided directly to the crankshaft or transmission for any portion of the motive force of the vehicle, but an mHEV may still be considered an xEV since it does use electric power to supplement a vehicle's power needs when the vehicle is idling with internal combustion engine disabled and recovers braking energy through an integrated starter generator. In addition, a plug-in electric vehicle (PEV) is any vehicle that can be charged from an external source of electricity, such as wall sockets, and the energy stored in the rechargeable battery packs drives, or contributes to drive, the wheels. PEVs are a subcategory of EVs that include all-electric or battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicle conversions of hybrid electric vehicles and conventional internal combustion engine vehicles.

xEVs as described above may provide a number of advantages as compared to more traditional gas-powered vehicles using only internal combustion engines and traditional electrical systems, which are typically 12V systems powered by a lead acid battery. For example, xEVs may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to traditional internal combustion vehicles and, in some cases, such xEVs may eliminate the use of gasoline entirely, as is the case of certain types of EVs or PEVs.

As technology continues to evolve, there is a need to provide improved power sources, particularly battery modules, for such vehicles. For example, battery modules may undergo overcharge testing to determine boundaries and/or limits of the battery module and its individual battery cells. Additionally, in certain instances, for example due to changing environmental conditions or other operating conditions, battery cells may be subject to overcharging. Overcharge tests and overcharging may lead to thermal runaway (e.g., an internal short circuit) caused by overheating in the battery cells. Thermal runaway may render the battery cell and an associated battery module permanently inoperable. Therefore, devices that may prevent or block thermal runaway are desired.

The document <CIT> relates to a prismatic lithium ion battery cell includes a packaging having a cover. The cover includes: a first spiral disk feature disposed below a first terminal pad; a second spiral disk feature disposed below a second terminal pad; a first reversal disk disposed below the first spiral disk feature; and a second reversal disk disposed below the second spiral disk feature. The first and second reversal disks are configured to deflect upwards to displace the first and second spiral disk features to contact the first and second terminal pads, respectively, in response to a pressure within the packaging being greater than a predefined pressure threshold and form an external short-circuit between the first and second terminal pads via the first and second spiral disk features. A battery comprising a current interruption device being provided with a deformable diaphragm is known from <CIT>.

The present invention relates to a lithium-ion battery cell according to independent claims <NUM> and <NUM>, wherein further developments of the present invention are provided in the sub-claims, respectively.

It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments.

The present disclosure relates to a lithium-ion battery cell including a casing; a first terminal pad having a first polarity and positioned proximate the casing; a second terminal pad having a second polarity opposite to the first polarity and positioned proximate the casing; a reversal device formed into the casing and responsive to an increase in internal pressure within the casing so as to cause a short circuit between the first terminal pad and the second terminal pad when the internal pressure reaches a threshold. A perimeter portion of the reversal device extends outwardly away from an interior of the lithium-ion battery cell, and a movable central portion of the reversal device is contiguous with and surrounded by the perimeter portion and has a center and a frustum surrounding the center. The frustum and the perimeter portion are oriented crosswise relative to one another, and the frustum extends from the perimeter portion toward the interior of the lithium-ion battery cell.

The present disclosure also relates to a lithium-ion battery module having a housing and a plurality of lithium-ion battery cells positioned within the housing. Each lithium-ion battery cell of the plurality of lithium-ion battery cells includes a casing, a first terminal pad having a first polarity and positioned proximate the casing, a second terminal pad having a second polarity opposite to the first polarity and positioned proximate the casing, and a reversal device formed into the casing and responsive to an increase in internal pressure within the casing so as to cause a short circuit between the first terminal pad and the second terminal pad when the internal pressure reaches a threshold. A perimeter portion of the reversal device extends outwardly away from an interior of the lithium-ion battery cell, and a movable central portion of the reversal device is contiguous with and surrounded by the perimeter portion and has a center and a frustum surrounding the center. The frustum and the perimeter portion are oriented crosswise relative to one another, and the frustum extends from the perimeter portion toward the interior of the lithium-ion battery cell.

The present disclosure also relates to a lithium-ion battery cell includes a casing, a first terminal pad having a first polarity and positioned proximate the casing, a second terminal pad having a second polarity opposite to the first polarity and positioned proximate the casing, and a reversal device formed into the casing and responsive to an increase in internal pressure within the casing so as to cause a short circuit between the first terminal pad and the second terminal pad when the internal pressure reaches a threshold. The reversal device has a folded configuration and an unfolded configuration, and is configured to transition from the folded configuration to the unfolded configuration in response to an increase in the internal pressure from below the threshold to the threshold.

The battery systems described herein may be used to provide power to various types of electric vehicles (xEVs) and other high voltage energy storage/expending applications (e.g., electrical grid power storage systems). Such battery systems may include one or more battery modules, each battery module having a number of battery cells (e.g., Lithium-ion (Li-ion) electrochemical cells) arranged to provide particular voltages and/or currents useful to power, for example, one or more components of an xEV. As another example, battery modules in accordance with present embodiments may be incorporated with or provide power to stationary power systems (e.g., non-automotive systems).

During the design and manufacturing process of a battery module, various tests may be performed upon the battery module and its individual battery cells to determine optimal performance parameters. For example, overcharge tests may provide excess electrical current to an individual battery cell of a battery module using a power supply with a voltage that exceeds a voltage of the individual battery cell. Overcharge testing may provide data related to temperature, heat output, and/or voltage of the overcharged battery cell, which may enable designers or manufacturers to modify various components of the battery cell to enhance performance (e.g., minimize damage to an overcharged battery cell). Therefore, such tests may be desirable for providing information that may enable manufacturers to optimize a battery module. In addition to overcharge testing, battery cells may be overcharged as a result of environmental conditions or abnormal operating parameters.

In certain cases, overcharging a battery cell may lead to thermal runaway (e.g., an internal short circuit) or another event causing permanent damage to the battery cell. For instance, charging a battery cell may generate dendrites as a result of intercalation of positive ions in the anode. Thermal runaway may result due to an excess buildup of dendrites on a separator of a battery cell (e.g., the dendrites may penetrate the separator enabling mixing of the positive electrode and the negative electrode) when the battery cell is overcharged (e.g., from an overcharge test or under abnormal operating conditions). Thermal runaway may be undesirable because it generates excessive heat, which may cause permanent damage to the battery cell and/or render the battery cell permanently inoperable.

Various features may be included as part of the battery cell that prevent or block thermal runaway when the battery cell is overcharged. Some battery cells may include a mechanism that completely breaks (e.g., disrupts a flow of electrical current) an electrical connection to at least one terminal of the battery cell when a pressure in the battery cell reaches a certain level. Such a mechanism thereby disrupts current flow to at least one terminal of the battery cell, which may ultimately lead to decreased current capacity of the battery cell. Such configurations may be referred to as including a current interrupt device (CID).

Other configurations may maintain the electrical connection to one or both terminals of the battery cell while preventing thermal runaway during overcharge. Such configurations may be referred to as including a complete current discharge device (CCD). For example, in such configurations, when a pressure in the battery cell exceeds a threshold level, an external short circuit may be triggered by electrically coupling the positive terminal and the negative terminal of the battery cell via a casing of the battery cell, for example. Accordingly, thermal runaway may be prevented and an electrical current capacity of the battery cell terminals is not reduced because the electrical pathway (e.g., connection) from an external load to the terminals remains intact.

In accordance with present embodiments, a battery cell includes an overcharge protection assembly that has a reversal device, the reversal device having a folded configuration that unfolds in response to an increase in internal cell pressure. The unfolded configuration that results causes a conductor associated with the reversal device to contact positive and negative terminal pads of the battery cell, thereby forming a short circuit. The current spike resulting from the short circuit may cause a current load on one of the current collectors of the battery cell to be greater than the current collector can handle. This may cause melting of the current collector and an interrupt in current flow and, therefore, overcharge.

To help illustrate, <FIG> is a perspective view of an embodiment of a vehicle <NUM>, which may utilize a regenerative braking system. Although the following discussion is presented in relation to vehicles with regenerative braking systems, the techniques described herein are adaptable to other vehicles that capture/store electrical energy with a battery, which may include electric-powered and gas-powered vehicles.

As discussed above, it would be desirable for a battery system <NUM> to be largely compatible with traditional vehicle designs. Accordingly, the battery system <NUM> may be placed in a location in the vehicle <NUM> that would have housed a traditional battery system. For example, as illustrated, the vehicle <NUM> may include the battery system <NUM> positioned similarly to a lead-acid battery of a typical combustion-engine vehicle (e.g., under the hood of the vehicle <NUM>). Furthermore, as will be described in more detail below, the battery system <NUM> may be positioned to facilitate managing temperature of the battery system <NUM>. For example, in some embodiments, positioning a battery system <NUM> under the hood of the vehicle <NUM> may enable an air duct to channel airflow over the battery system <NUM> and cool the battery system <NUM>.

In other words, the battery system <NUM> may supply power to components of the vehicle's electrical system, which may include radiator cooling fans, climate control systems, electric power steering systems, active suspension systems, auto park systems, electric oil pumps, electric super/turbochargers, electric water pumps, heated windscreen/defrosters, window lift motors, vanity lights, tire pressure monitoring systems, sunroof motor controls, power seats, alarm systems, infotainment systems, navigation features, lane departure warning systems, electric parking brakes, external lights, or any combination thereof. Illustratively, in the depicted embodiment, the energy storage component <NUM> supplies power to the vehicle console <NUM> and the ignition system <NUM>, which may be used to start (e.g., crank) an internal combustion engine <NUM>.

Additionally, the energy storage component <NUM> may capture electrical energy generated by the alternator <NUM> and/or the electric motor <NUM>. In some embodiments, the alternator <NUM> may generate electrical energy while the internal combustion engine <NUM> is running. More specifically, the alternator <NUM> may convert the mechanical energy produced by the rotation of the internal combustion engine <NUM> into electrical energy. Additionally or alternatively, when the vehicle <NUM> includes an electric motor <NUM>, the electric motor <NUM> may generate electrical energy by converting mechanical energy produced by the movement of the vehicle <NUM> (e.g., rotation of the wheels) into electrical energy. Thus, in some embodiments, the energy storage component <NUM> may capture electrical energy generated by the alternator <NUM> and/or the electric motor <NUM> during regenerative braking. As such, the alternator <NUM> and/or the electric motor <NUM> are generally referred to herein as a regenerative braking system.

To facilitate capturing and supplying electric energy, the energy storage component <NUM> may be electrically coupled to the vehicle's electric system via a bus <NUM>. For example, the bus <NUM> may enable the energy storage component <NUM> to receive electrical energy generated by the alternator <NUM> and/or the electric motor <NUM>. Additionally, the bus <NUM> may enable the energy storage component <NUM> to output electrical energy to the ignition system <NUM> and/or the vehicle console <NUM>. Accordingly, when a <NUM> volt battery system <NUM> is used, the bus <NUM> may carry electrical power typically between <NUM>-<NUM> volts.

Additionally, as depicted, the energy storage component <NUM> may include multiple battery modules. For example, in the depicted embodiment, the energy storage component <NUM> includes a lithium ion (e.g., a first) battery module <NUM> and a lead-acid (e.g., a second) battery module <NUM>, which each includes one or more battery cells. In other embodiments, the energy storage component <NUM> may include any number of battery modules. Additionally, although the lithium ion battery module <NUM> and lead-acid battery module <NUM> are depicted adjacent to one another, they may be positioned in different areas around the vehicle. For example, the lead-acid battery module <NUM> may be positioned in or about the interior of the vehicle <NUM> while the lithium ion battery module <NUM> may be positioned under the hood of the vehicle <NUM>.

In some embodiments, the energy storage component <NUM> may include multiple battery modules to utilize multiple different battery chemistries. For example, when the lithium ion battery module <NUM> is used, performance of the battery system <NUM> may be improved since the lithium ion battery chemistry generally has a higher coulombic efficiency and/or a higher power charge acceptance rate (e.g., higher maximum charge current or charge voltage) than the lead-acid battery chemistry. As such, the capture, storage, and/or distribution efficiency of the battery system <NUM> may be improved.

To facilitate controlling the capturing and storing of electrical energy, the battery system <NUM> may additionally include a control module <NUM>. More specifically, the control module <NUM> may control operations of components in the battery system <NUM>, such as relays (e.g., switches) within energy storage component <NUM>, the alternator <NUM>, and/or the electric motor <NUM>. For example, the control module <NUM> may regulate an amount of electrical energy captured/supplied by each battery module <NUM> or <NUM> (e.g., to de-rate and re-rate the battery system <NUM>), perform load balancing between the battery modules <NUM> and <NUM>, determine a state of charge of each battery module <NUM> or <NUM>, determine temperature of each battery module <NUM> or <NUM>, control voltage output by the alternator <NUM> and/or the electric motor <NUM>, and the like.

Accordingly, the control module <NUM> may include one or more processors <NUM> and one or more memory components <NUM>. More specifically, the one or more processors <NUM> may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof. Additionally, the one or more memory components <NUM> may include volatile memory, such as random access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, or solid-state drives. In some embodiments, the control module <NUM> may include portions of a vehicle control unit (VCU) and/or a separate battery control module.

As discussed above, before a battery module may be used to supply power to an xEV, various tests may be conducted upon the battery module and its individual battery cells to optimize operating parameters of the battery module. One such test may be an overcharge test that determines how much electrical current a battery cell may receive, or how long a battery cell may receive an electrical current, before damage occurs to the battery cell. However, in certain instances, overcharge tests may result in thermal runaway (e.g., an internal short circuit within the battery cell), which may cause permanent damage to the battery cell because of excess heat generated from the overcharge. It is now recognized that it may be desirable to prevent thermal runaway (e.g., an internal short circuit) by triggering an external short circuit (e.g., electrically coupling the positive terminal and the negative terminal of the battery cell) before thermal runaway occurs. In certain embodiments, the external short circuit may be triggered by establishing an electrical connection between terminals of the battery cell, or between a terminal of the battery cell and the cell casing (e.g., can) in embodiments where the can is polarized.

<FIG> is a cross-sectional elevation view of an embodiment of an overcharge protection assembly <NUM> configured in accordance with the present disclosure. In one or more embodiments, the assembly <NUM> includes a reversal device <NUM> formed into a casing <NUM> (e.g., a lid) of a lithium ion battery cell, the reversal device <NUM> having a folded configuration, which is shown in <FIG>, and an unfolded configuration, which is shown in <FIG>. The reversal device <NUM> is responsive to a change in the internal pressure of the battery cell on which it is integrated, and transforms from the configuration in <FIG> to the configuration shown in <FIG> in response to the internal pressure of the battery cell reaching a threshold.

In one or more embodiments, the reversal device <NUM> is circular in shape. Other shapes can be used, as long as they operate in accordance with the principles as described herein. The reversal device <NUM> includes a perimeter portion <NUM>, a folding portion <NUM> and a movable central portion <NUM>. As shown, the perimeter portion <NUM> and the movable central portion <NUM> are joined at a ridge, which corresponds to the folding portion <NUM>. The illustrated movable central portion <NUM> includes a center portion 38a, such as a disk, and a frustum 38b that surrounds the center portion 38a and that is directly joined (e.g., integrally formed) with the perimeter portion <NUM>. In the illustrated embodiment, the frustum 38b is a conical frustum. The frustum 38b and the perimeter portion <NUM> are oriented crosswise relative to one another, and the frustum 38b extends from the perimeter portion <NUM> toward the interior of the lithium-ion battery cell.

The reversal device <NUM> intersects one or more planes such as an expansion plane <NUM>, a base plane <NUM> and a non-expansion plane <NUM> that are described in detail herein. The folding portion <NUM> is configured to allow the movable central portion <NUM> to intersect the base plane <NUM> before pressure activation. In particular, the folding portion <NUM> corresponds to a portion of the reversal device <NUM> where the movable central portion <NUM> meets the perimeter portion <NUM>.

The reversal device <NUM> is configured such that the perimeter portion <NUM> of the reversal device <NUM> angles away from the base plane <NUM> while the folding portion <NUM> angle the movable central portion <NUM> of the reversal device <NUM> back towards the base plane <NUM>, thereby creating an indent or cup shape. In one or more embodiments, the perimeter portion <NUM> extends upward and inward from the base plane <NUM>. In one or more embodiments, the movable central portion <NUM> is contiguous with and surrounded by the perimeter portion <NUM>, and the movable central portion <NUM> allows expansion of the reversal device <NUM> when activated to intersect the expansion plane <NUM>. In one or more embodiments, the movable central portion <NUM> and the perimeter portion <NUM> meet at the folding portion <NUM> of the reversal device <NUM>.

The distance from the base plane <NUM> to the folding portion <NUM> is denoted as D1 while the distance from the folding portion <NUM> to a base <NUM> or lower part of the movable central portion <NUM> is denoted as D2. The base <NUM> of the movable central portion <NUM> intersects the non-expansion plane <NUM> if the reversal device <NUM> is not activated or if the reversal device <NUM> is in a first position. In other words, before pressure activation, in one or more embodiments, the reversal device <NUM> includes the perimeter portion <NUM> to one side of the base plane <NUM> and the movable central portion <NUM> on both sides of the base plane <NUM>. The configuration of the reversal device <NUM> increases the top-to-top deflection (e.g., overall movement of the base <NUM>) of the reversal device <NUM> as compared with other devices, thereby reducing faulty triggering due to, for example, vibrations of an automobile or failure to make good contact with short circuit pads.

The overcharge protection assembly <NUM> includes a conductor <NUM>, a positive terminal pad <NUM> and a negative terminal pad <NUM>. In the embodiment of <FIG>, the conductor <NUM> is positioned at least partially within an indent or cup defined by the movable central portion <NUM>. The positive terminal pad <NUM> and the negative terminal pad <NUM> are positioned proximate the conductor <NUM>, and are configured to provide power to one or more loads such as an automobile or car. In particular, the reversal device <NUM>, in this embodiment, may be used for overcharge protection of a lithium ion battery module (e.g., module <NUM>) with one or more lithium ion cells where activation of the reversal device <NUM> places the conductor <NUM> in electrical communication with the positive terminal pad <NUM> and the negative terminal pad <NUM>, thereby creating a short circuit as illustrated in <FIG>.

In the illustrated embodiment of <FIG>, the perimeter portion <NUM> extends from a casing of the battery cell toward the general direction of the positive and negative terminal pads <NUM>, <NUM>, while the frustum 38b of the movable center portion <NUM> extends away from the positive and negative terminal pads <NUM>, <NUM>. Such a configuration creates a fold in the reversal device <NUM>, which, as described in further detail herein, provides for a greater overall distance of deflection by the center 38b and, therefore, greater axial movement of the conductor <NUM>. This greater distance of deflection allows for, among other things, the prevention of accidental triggering of a short circuit.

In transitioning the configuration of the reversal device <NUM> from the configuration of <FIG> to the configuration of <FIG>, the movable central portion <NUM> of the reversal device <NUM> is moved from a first position (before activation) to a second position (after activation) such that the conductor <NUM> is moved into the shorting position. Activation in this embodiment may be caused, for example, by overcharging where internal pressure of the battery increases such as to cause the reversal device <NUM> to unfold and thereby reposition the movable central portion <NUM> from a first position to a second position. In some embodiments, this external short generates a high current spike that causes an internal current collector of the battery to fail (e.g., melt), thereby stopping the overcharge of the battery. In other embodiments, the short triggers an overcurrent protection mechanism in the charging device used to charge the battery, thereby discontinuing the charging.

<FIG> is a side-by-side cross-sectional view of reversal device <NUM> and a reverse buckling device <NUM>, which does not include folding portion <NUM> or perimeter portion <NUM>. In one or more embodiments, distance D2 from the folding portion <NUM> of the reversal device <NUM> to the base plane <NUM> is equal to a distance D3 from a central portion <NUM> of reverse buckling device <NUM> to a plane <NUM>. However, for top-to-top deflection, i.e., activation, the base <NUM> of the central portion <NUM> traverses distances D1 and D2 to reach the same plane <NUM> as the folding portion <NUM>, and then traverses distances D1 and D2 (height of movable central portion <NUM>) to reach full deflection as illustrated in <FIG>.

<FIG> is a side-by-side cross sectional view of the reversal device <NUM> and the reverse buckling device <NUM>, where both the reversal device <NUM> and the reverse buckling device <NUM> have been activated. The central portion <NUM> of the reverse buckling device <NUM> traverses distances D3 and D4 to reach full top-to-top deflection. The shortened distance of top-to-top deflection for the central portion <NUM> makes this configuration susceptible to faulty activation, while the reversal device <NUM> cures at least some of the deficiencies of the reverse buckling device <NUM> by increasing top-to-top deflection distance.

The arrangement of the reversal device <NUM> allows for a larger separation between the reversal device <NUM> and the short circuit pads when in a deactivated state as compared with other devices. This arrangement therefore avoids unintended activation resulting from vibration and allows for a more positive connection with the short circuiting pads when activated. In one or more embodiments, at least a portion of the movable central portion <NUM> intersects the base plane <NUM> if the reversal device <NUM> is not activated, i.e., if the reversal device <NUM> is in the first position. In one or more embodiments, the movable central portion <NUM> does not intersect the base plane <NUM> and/or the expansion plane <NUM> if the reversal device <NUM> is activated, i.e., if the reversal device <NUM> is in the second position. In one or more embodiments, the movable central portion <NUM> forms an indent or first cup facing a first direction if the reversal device <NUM> is not activated (e.g., in the first position). In one or more embodiments, the movable central portion <NUM> forms an indent or second cup facing a second direction opposite a first direction if the reversal device <NUM> is activated (e.g., is in the second position). In one or more embodiments, the movable central portion <NUM> is pivoted about the folding portion <NUM> if the reversal device <NUM> is activated.

<FIG> is a cross-sectional elevation view of another example of the reversal device <NUM> in accordance with certain embodiments of the disclosure. The illustrated reversal device <NUM> of <FIG> includes one or more notches <NUM> formed in the folding portion <NUM>. The strain hardening around fold portion <NUM> introduced by a forming process of creating the reversal device <NUM> may, in some instances, make the reversal device <NUM> harder to fully unfold, i.e., harder to achieve top-to-top deflection. The notch <NUM> helps alleviate at least some of the drawbacks to the manufacturing process by thinning a section of the folding portion <NUM> to facilitate unfolding to a higher degree, which increases top-to-top deflection as illustrated in <FIG>, where top-to-top deflection reduces faulty activations. In one or more embodiments, the movable central portion <NUM> and the perimeter portion <NUM> define the notch <NUM> proximate a point of contact between the movable central portion <NUM> and the perimeter portion <NUM>. In one or more embodiments, the notch <NUM> is a region of reduced thickness of a portion of the movable central portion <NUM> and a thickness of a portion of the perimeter portion <NUM>. In one or more embodiments, the movable central portion <NUM> and the perimeter portion <NUM> define a groove surrounding the movable central portion <NUM>, the groove corresponding to the notch <NUM>.

As set forth above, the overcharge protection assembly <NUM> may be integrated into a lithium-ion battery cell. <FIG> is a perspective view of an embodiment of a prismatic lithium ion battery cell <NUM> having the overcharge protection assembly <NUM> - specifically, the reversal device <NUM> is formed into a packaging <NUM> of the cell <NUM>. As used herein, "prismatic" refers to the generally box-like (e.g., polygonal) shape of the substantially rigid packaging <NUM> of the battery cell <NUM>, where the packaging <NUM> corresponds to or includes the casing <NUM>. As such, it should be appreciated that the disclosed prismatic cells <NUM> are distinct from pouch battery cells, which have a substantially flexible laminate packaging. Further, it should be appreciated that the disclosed prismatic cells <NUM> are also distinct from cylindrical battery cells, which have a substantially rigid cylindrical packaging. Those skilled in the art will appreciate that these different cell shapes and packaging materials present different limitations and modes of failure, and issues or solutions that are effective for one type of battery cell may not be applicable to others. The packaging <NUM> may be metallic or polymeric, or a combination. In one embodiment, the packaging <NUM>, including the casing <NUM>, is aluminum and the reversal device <NUM> is aluminum. In certain embodiments of the battery cell <NUM>, the reversal device <NUM> may act as a vent mechanism for the battery cell <NUM>, such that at a first pressure threshold, the reversal device causes the short circuit discussed above. At a second pressure threshold higher than the first, the reversal device <NUM> may rupture from the casing <NUM>, and allow for cell effluent to be controllably released from the interior of the battery cell <NUM>.

The packaging <NUM> of the illustrated prismatic lithium ion battery cell <NUM> may be generally described as having a first and a second substantially flat side portion, <NUM> and <NUM>, disposed opposite one another. Additionally, the packaging <NUM> includes a first and a second end portion <NUM> and <NUM>, disposed opposite one another. In certain embodiments, the end portions <NUM> and <NUM> may be substantially flat, rounded, or substantially flat will slight rounded corners <NUM>, as illustrated.

The positive and negative terminal pads <NUM>, <NUM> are shown as positioned at a terminal end <NUM> of the battery cell <NUM>, which is situated at an opposite end from the base <NUM> of the battery cell <NUM>. In this way, referring to <FIG> and <FIG> in combination, it should be appreciated that the perimeter portion <NUM> extends generally along an angled direction from the base <NUM> toward the terminal end <NUM>, and the frustum 38b extends generally along an angled direction from the terminal end <NUM> to the base <NUM>. Activation of the reversal device <NUM> results in movement of the center 38a in a direction from the base <NUM> toward the terminal end <NUM>.

As set forth above, a lithium-ion battery module, such as the lithium-ion battery module <NUM> may include multiple of the lithium-ion battery cells <NUM>. <FIG> is a perspective view of an example embodiment of the lithium-ion battery module <NUM> having a housing <NUM> containing a plurality of lithium-ion battery cells <NUM>. Specifically, <FIG> is an exploded perspective view of an embodiment of the battery module <NUM>, which may be used in the xEV <NUM> of <FIG>, or another system, such as a stationary storage system. As illustrated, certain embodiments of the battery module <NUM> include a plurality of the prismatic lithium ion battery cells <NUM>, which may be arranged in various configurations (e.g., orientations, orders of stacking). However, the cells <NUM> will generally be provided in an amount and configuration so as to have a sufficient energy density, voltage, current, capacity, and so forth, for a particular stationary application. As discussed in greater detail below, in different embodiments, the cells <NUM> may have a polymeric casing, or a metallic casing, or a combination, enclosing the electrochemically active components of the battery cells <NUM>.

The battery module <NUM> of <FIG> includes a stack or lineup of the battery cells <NUM>, with a bus bar carrier <NUM> being positioned over terminals (e.g., terminal pads <NUM>, <NUM>) so as to enable electrical interconnection of the battery cells <NUM> using the bus bar assembly <NUM>. The bus bar assembly <NUM> generally electrically connects the battery cells <NUM> as an electrical assembly. In certain embodiments, the bus bar assembly <NUM> may be integrated onto the bus bar carrier <NUM>, in some instances along with other suitable features (e.g., voltage sense connectors).

For the illustrated embodiment, a traceboard <NUM> is positioned over the bus bar assembly <NUM> such that the bus bar assembly <NUM> is positioned between the traceboard <NUM> and the bus bar carrier <NUM>. A battery management system (BMS) <NUM> is integrated onto the traceboard <NUM> to connect the BMS <NUM> to any sense features (e.g., temperature and/or voltage sense features) and to enable control of the cells <NUM> and the overall operation of the battery module <NUM>.

The housing <NUM> of the illustrated embodiment completely encloses the cells <NUM>. As illustrated, the module housing <NUM> takes the shape of its constituent battery cells <NUM>; in this instance a prismatic form. However, the housing <NUM> may be formed to have any appropriate shape for a particular application. A cover <NUM> is provided above the BMS <NUM>, traceboard <NUM>, and bus bar assembly <NUM> and attaches to an upper portion of the battery module housing <NUM>. The cover <NUM> is configured to substantially enclose the BMS <NUM>, traceboard <NUM>, and bus bar assembly <NUM> to prevent inadvertent contact with electrical and control components.

Claim 1:
A lithium-ion battery cell (<NUM>), comprising:
- a casing (<NUM>);
- a first terminal pad (<NUM>) having a first polarity and positioned proximate the casing (<NUM>);
- a second terminal pad (<NUM>) having a second polarity opposite to the first polarity and positioned proximate the casing (<NUM>);
- a reversal device (<NUM>) formed into the casing (<NUM>) and responsive to an increase in internal pressure within the casing (<NUM>) so as to cause a short circuit between the first terminal pad (<NUM>) and the second terminal pad (<NUM>) when the internal pressure reaches a threshold;
- a perimeter portion (<NUM>) of the reversal device (<NUM>), the perimeter portion (<NUM>) extending outwardly away from an interior of the lithium-ion battery cell (<NUM>); and
- a movable central portion (<NUM>) of the reversal device (<NUM>) contiguous with and surrounded by the perimeter portion (<NUM>) and comprising a center (38a) and a frustum (38b) surrounding the center (38a), wherein the frustum (38b) and the perimeter portion (<NUM>) are oriented crosswise relative to one another, and the frustum (38b) extends from the perimeter portion (<NUM>) toward the interior of the lithium-ion battery cell (<NUM>).