GB2589073A

GB2589073A - Battery pack

Info

Publication number: GB2589073A
Application number: GB1916074.6A
Authority: GB
Inventors: Andrew Hunt Ian; Madsen Alex
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2019-11-05
Filing date: 2019-11-05
Publication date: 2021-05-26
Also published as: WO2021090002A1; GB201916074D0

Abstract

A battery pack 112 comprises a housing 114 defining a cavity 116, at least one pouch cell 200a-e within the cavity, and an electrical connection 124, (324, figure 3) between the pouch cell 200a, (300a, figure 3) and at least one of a further pouch cell (300b, figure 3) of the battery pack, or another electrical component 122a. The electrical connection is configured to be severed by a movement of the pouch cell, relative to a surface of the housing within the cavity, which satisfies a predetermined condition. The electrical connection may comprise a rigid electrode which is broken under tension caused by swelling of at least one of the pouch cells. In a further example, an electrical connection (524, figure 5) may be severed by movement of the electrical connection caused by swelling of the pouch cell so that it contacts a cutting element (132, figure 5). This arrangement cuts power to or from the battery pack when a pouch cell expands to dangerous levels caused, for example, by overcharging or excessive temperatures, thereby leading to greater safety. The battery pack may include a buffer region for acceptable battery swelling before severance of the electrical connection.

Description

BATTERY PACK

Technical Field

The present invention relates to a battery pack and more particularly to a battery pack including at least one pouch cell.

Background

Pouch cell batteries such as lithium-ion batteries may include flammable materials, which may ignite or explode if the cell is faulty, overcharged or overheated.

It is desired to improve the safety of a battery park including at least one pouch cell.

Summary

According to a first aspect of the present invention, there is provided a battery pack comprising: a housing defining a cavity; a pouch cell within the cavity; and an electrical connection between the pouch cell and at least one of: a further pouch cell of the battery pack, or another electrical component. The electrical connection is configured to be severed by a movement of the pouch cell, relative to a surface of the housing within the cavity, which satisfies a predetermined condition.

As the electrical connection of the battery pack is configured to be severed by a movement of the pouch cell which satisfies a predetermined condition, the battery pack may be safer than other battery packs without such an arrangement. For example, the predetermined condition may correspond to a condition in which the safety of the battery pack would be compromised if current continued to flow (e.g if severance of the electrical connection did not occur). Hence, by severing the electrical connection, current may cease flowing within the battery pack, which may reduce the risk of the battery pack exploding or igniting.

The battery pack of the first aspect may be less complex than other battery packs, and may not include additional components that may add mass, reduce energy density and/or reduce performance of the battery pack. For example, the severance of the electrical connection may be due to the particular arrangement of the electrical connection with respect to the surface of the housing, rather than due to the inclusion of additional, current-interrupting components, which may adversely affect the efficiency and/or internal resistance of a battery pack. Performance of the battery pack may therefore be improved. Additionally or alternatively, manufacture of the battery pack may be more straightforward and/or more efficient. The battery pack may be lighter than other battery packs with additional, current-interrupting components.

The electrical connection of the first aspect may be less likely to fail across the lifetime of the battery pack, as it may be simpler than other electrical connections. For example, the electrical connection need not include perforations or frangible portions, which may hinder the performance of the battery pack and/or which may be more likely to break unexpectedly.

In examples, the movement of the pouch cell comprises movement of the pouch cell due to generation of gas within the pouch cell. Generation of gas within a pouch cell may occur when the pouch cell is faulty or is subject to an abuse condition, such as excessive temperature, charge or current. In such examples, the electrical connection may be configured to be severed by movement of the pouch cell due to a fault or abuse of the pouch cell. This may reduce the risk of the fault or abuse of the pouch cell continuing and potentially leading to ignition of the gas. The safety of the battery pack may therefore be improved.

In examples, the movement of the pouch cell comprises movement of the pouch cell due to expansion of the pouch cell. In these examples, the electrical connection may be configured to be severed by expansion of the pouch cell, for example due to generation of gas within the pouch cell. For example, the pouch cell may have a nonrigid housing, which may inflate and deflate during charging and discharging of the pouch cell. If the pouch cell suffers from a fault or is misused (e.g. overheated, overcharged or subject to excessive current), the pouch cell may continue to inflate, due to excess gas generation within the cell. In these examples, though, the expansion of the pouch cell may cause the electrical connection to be severed, which may prevent current from flowing through the pouch cell. This may therefore render the battery pack safe or relatively safer than may otherwise be the case.

In examples, the movement of the pouch cell comprises movement of the pouch cell away from the surface of the housing. The movement of the pouch cell away from the surface of the housing, for example due to gas generation within the pouch cell, may cause the electrical connection to be severed. The electrical connection may be severed by the movement of the pouch cell itself, rather than by additional components. This may render the battery pack relatively safer than may otherwise be the case, while reducing complexity of the battery pack.

In examples, movement of the pouch cell which exceeds a predetermined amount satisfies the predetermined condition. In this way, a certain amount of movement of the pouch cell may be tolerated without severing the electrical connection. For example, the electrical connection may not be severed by movement of the pouch cell which is within an expected range of movement of the pouch cell during expected or otherwise predicted charging and discharging of the pouch cell, e.g. during normal use of the battery pack. However, the electrical connection may be configured to be severed by movement of the pouch cell which exceeds this amount of movement (which may be considered to be a predetermined amount). This allows the battery pack to function under usual conditions, without unduly affecting performance of the battery pack. However, where the movement of the pouch cell exceeds the predetermined amount, this may indicate that the pouch cell is operating unsafely. The electrical connection may be configured to be severed due to such movement of the pouch cell. This may prevent current from flowing through the pouch cell, which may reduce the risk of ignition of the battery pack. The safety of the battery pack may therefore be improved.

In examples, the pouch cell is constrained to move in a predetermined direction relative to the surface of the housing. This may improve the predictability of the movement of the pouch cell. A more appropriate predetermined condition for severance of the electrical connection may therefore be set, which may allow the battery pack to continue operating under a wider range of conditions than may otherwise be the case, without compromising the safety of the battery pack. In these examples, the predetermined direction may be substantially perpendicular to a plane of the surface of the housing. This may improve severance of the electrical connection due to the movement of the pouch cell relative to the surface of the housing. For example, if the electrical connection is coupled between the surface of the housing and the pouch cell, movement of the pouch cell substantially perpendicular to the plane of the surface of the housing may break the electrical connection. This may further reduce the risk of current continuing to flow through the pouch cell after the predetermined condition is satisfied (e.g. after a fault or misuse of the pouch cell). The safety of the battery pack may therefore be improved.

In examples, the pouch cell is a first pouch cell, the battery pack comprises a second pouch cell electrically connected to the first pouch cell, and the movement of the first pouch cell comprises movement of the first pouch cell due to at least one of: generation of gas within the second pouch cell; and expansion of the second pouch cell. The second pouch cell may be the further pouch cell. In these examples, the electrical connection may be configured to be severed by a fault or misuse of a pouch cell (the second pouch cell) other than the pouch cell connected to the electrical connection (the first pouch cell). In this way, the battery pack need not include an electrical connection per pouch cell, which may reduce the complexity of the battery pack. For example, the battery pack may include a single electrical connection configured to be severed by the movement of the pouch cell, which may be severed due to movement of the pouch cell which is caused by or a result of movement of any of the other pouch cells in the battery pack.

In examples, the electrical connection comprises an electrode, wherein a first portion of the electrode is connected to the pouch cell and a second portion of the electrode is connected to the housing or the further pouch cell. With this arrangement, the electrode may be severed due to relative motion between the pouch cell and the surface of the housing or the further pouch cell. The electrode may be under increasing tension as the pouch cell moves away from the surface of the housing or the further pouch cell (for example as the pouch cell expands due to generation of gas therein). Once the tension exceeds a given tension, the electrode may break, and the electrical connection may be severed. This may prevent current from flowing through the pouch cell, which may reduce the risk of ignition of the pouch cell. The battery pack may therefore be relatively safer than may otherwise be the case. Moreover, as the electrode may be severed due to the relative motion between the pouch cell and the surface of the housing or the further pouch cell, a safer battery pack may be provided without the use of additional components that may increase the complexity and/or reduce the performance of the battery pack. For example, the electrode need not be perforated or frangible, which may hinder the performance of the battery pack.

In these examples, the electrode may be twisted. This may aid tearing of the electrode due to the relative motion between the pouch cell and the surface of the housing or the further pouch cell. This may further improve the severance of the electrical connection when the predetermined condition is satisfied, which may improve the safety of the battery pack. The electrode may be substantially rigid. This may improve breaking of the electrode due to the movement of the pouch cell, as the electrode may be severed by the movement of the pouch cell rather than undergoing a plastic deformation (such as a stretching of the electrode).

In examples, the battery pack comprises a cutting element configured to sever the electrical connection due to the movement of the pouch cell. The cutting element may improve severance of the electrical connection. In these examples, the movement of the pouch cell may cause movement of the electrical connection towards the cutting element, to sever the electrical connection. The severance of the electrical connection by the cutting element may therefore be caused by the movement of the pouch cell rather than by motion of the cutting element (or other elements). The electrical connection may therefore be severed in an efficient and straightforward manner, with reduced complexity than may otherwise be the case. The cutting element may be substantially electrically non-conductive. This may prevent current from continuing to flow through the pouch cell, via the cutting element, after the cutting element has severed the electrical connection (for example if the cutting element remains in contact with the electrical connection). This may further improve the safety of the battery pack. The cutting element may be integral to the battery pack. This may reduce the complexity of the battery pack and/or reduce the risk of failure that may occur if the cutting element is non-integral to the battery pack. The cutting element may be configured to sever the electrical connection due to the movement of the pouch cell by applying a shearing force to the electrical connection, wherein the electrical connection is non-frangible. By providing a non-frangible electrical connection, the performance of the electrical connection may be improved. The electrical connection may nevertheless be efficiently severed by the shearing force of the cutting element when the predetermined condition is satisfied.

In examples, the housing is substantially rigid. This may allow the pouch cell to be anchored or otherwise affixed or coupled relative to the surface of the housing, so that the movement of the pouch cell relative to the surface of the housing which satisfies the predetermined condition causes the electrical connection to be severed. The safety of the battery pack may therefore be improved without requiring additional components which may increase the complexity and/or mass and/or reduce the performance of the battery pack.

In examples, the electrical component is external to the battery pack. The electrical connection may therefore be used to connect the pouch cell to an external electrical component. By severing the electrical connection when the predetermined condition is satisfied in such cases, the flow of current to the external electrical component may be prevented or limited. This may further improve the safety of the battery pack.

In examples, the battery pack comprises a stack of pouch cells on the surface, the stack of pouch cells comprising the pouch cell. With such an arrangement, the movement of the pouch cell may be due to a fault or misuse of one of the other pouch cells of the stack. For example, pouch cells in the stack may be arranged one on top of the other, so that an expansion of one of the pouch cells causes a pouch cell above the expanded pouch cell to move relative to the surface of the housing. The electrical connection in such cases may therefore be severed by a fault or misuse of at least one of the pouch cells in the stack, even if that pouch cell is not connected to the electrical connection itself This may improve the safety of the battery pack, while reducing the need for multiple electrical connections that are configured to be severed. The complexity of the battery pack may therefore be reduced.

According to a second aspect of the present invention, there is provided a battery pack comprising: a housing defining a cavity including a battery region and an expansion region; a battery within the battery region of the cavity, the battery including one or more pouch cells, at least one of the battery or the housing being adapted so that any expansion of the battery, in use, is towards the expansion region; and an electrical connection between at least one of the battery and an electrical contact of the battery pack, or two pouch cells of the battery. The electrical connection is arranged to break if the battery expands into the expansion region of the cavity.

As the electrical connection of the battery pack is arranged to break if the battery expands into the expansion region of the cavity, the battery pack may be safer than other battery packs without such an arrangement. For example, the expansion region may correspond to a region of the cavity into which the battery at least partly expands in situations in which the safety of the battery pack would be compromised if current continued to flow (e.g. if breaking of the electrical connection did not occur). Hence, by breaking the electrical connection, current may cease flowing within the battery pack, which may reduce the risk of the battery pack exploding or igniting.

The battery pack of the second aspect may be less complex than other battery packs, and may not include additional components that may add mass, reduce energy density and/or reduce performance of the battery pack. For example, the breaking of the electrical connection may be due to the particular arrangement of at least one of the battery or the housing rather than due to the inclusion of additional, current-interrupting, components, which may adversely affect the efficiency and/or internal resistance of a battery pack. Performance of the battery pack may therefore be improved. Additionally or alternatively, manufacture of the battery pack may be more straightforward and/or more efficient, The battery pack may be lighter than other battery packs with additional, current-interrupting, components.

The electrical connection of the second aspect may be less likely to fail across the lifetime of the battery pack, as it may be simpler than other electrical connections.

The electrical connection may be an efficient connection, which may not include perforations or frangible portions, which may hinder the performance of the battery pack and/or which may be more likely to break unexpectedly.

In examples of the second aspect, at least one of the battery or the housing are adapted so that the battery expands into the expansion region of the cavity due to the battery exceeding at least one of an overtemperature condition, an overcharge condition, or an overcurrent condition. In these examples, the electrical connection may therefore be broken by expansion of the battery due to a fault or a misuse of the battery, which may cause the battery to exceed at least one of the overtemperature, overcharge condition, or overcurrent conditions. This may reduce the risk of the fault or abuse of the battery continuing and potentially leading to ignition or explosion of the battery. The safety of the battery pack may therefore be improved In these examples, the cavity may comprise a buffer region between the battery region and the expansion region, and the least one of the battery or the housing may be adapted so that expansion of the battery which does not exceed the overtemperature, overcharge, and overcurrent condition is within the buffer region. In this way, a certain amount of expansion of the battery may be tolerated without breaking the electrical connection. For example, the electrical connection may not be broken by expansion of the battery which is within an expected range of expansion of the battery during expected or otherwise predicted charging and discharging of the battery, e.g. during normal use of the battery pack. However, the electrical connection may be broken if expansion of the battery exceeds this amount of expansion and expands beyond the buffer region and into the expansion region. This allows the battery pack to function under usual conditions, without unduly affecting performance of the battery pack, while improving the safety of the battery pack.

Further features will become apparent from the following description, given by way of example only, which is made with reference to the accompanying drawings

Brief Description of the Drawings

Figure t is a schematic diagram of a pouch cell according to examples; Figures 2a to 2d are schematic diagrams of a battery pack according to

examples;

Figure 3 is a schematic diagram of a battery pack according to further examples, Figure 4 is a schematic diagram of a battery pack according to yet further examples; and Figure 5 is a schematic diagram of a portion of a battery pack according to still

further examples.

Detailed Description

Details of examples will become apparent from the following description, with reference to the Figures. In this description, for the purpose of explanation, numerous specific details of certain examples are set forth. Reference in the specification to "an example" or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in at least that one example, but not necessarily in other examples. It should further be noted that certain examples are described schematically with certain features omitted and/or necessarily simplified for ease of explanation and understanding of the concepts underlying the examples.

Figure 1 is a schematic diagram of a pouch cell 100 according to examples. The pouch cell 100 comprises a casing 102. The casing 102 comprises a front portion 104 and a rear portion 106 which, in Figure 1, are respective panels secured together at their peripheries. The front and rear portions 104, 106 are flexible. This allows the casing 102 to deform, for example if gas is generated within the pouch cell 100. The casing 102 is formed of heat-sealable foil, such as aluminium foil between polymer layers. The casing 102 acts as a barrier, to prevent contamination of the battery components within the pouch cell 10 by external materials and/or leakage of the battery components outside the pouch.

First and second electrodes and a separator (not shown) are sealed within the casing 102. The separator is interposed between the first and second electrodes to electrically insulate the first electrode from the second electrode. The first electrode, the second electrode and the separator may be spirally wound about a longitudinal axis to form a so-called "jelly roll", or they may be stacked as a series of layers. The pouch cell 100 is a lithium-ion cell, although this is merely an example. The first and second electrodes may be formed of any suitable material. For example, the first electrode, which may form a cathode during discharge of the pouch cell 100, may comprise a metal oxide such as a layered oxide (e.g. lithium cobalt oxide), a polyanion (e.g. lithium iron phosphate) or a spinel (e.g. lithium manganese oxide). The second electrode, which may form an anode during discharge of the pouch cell 100, may comprise carbon, for example in the form of graphite or graphene. The separator may comprise organic carbonates such as ethylene carbonate or diethyl carbonate comprising complexes of lithium ions.

The first and second electrodes are connected to first and second terminals 108, 110 which protmde from the casing 102. The first and second terminals 108, 110 may be referred to as cell tabs, and may be used to connect the pouch cell 100 to other electrical components, such as other pouch cells.

Figures 2a to 2d are schematic diagrams of a battery pack 112 according to examples. Figure 2a illustrates the position of pouch cells 200 within the battery pack 112. The pouch cells 200 are omitted from Figure 2b, to more clearly show various regions of the battery pack 112. In Figure 2a, the pouch cells 200 are unexpanded, and occupy a battery region as shown in Figure 2b. Figure 2c and 2d illustrate the battery pack 112 at various stages during expansion of a first pouch cell 200a of the pouch cells 200.

Referring to Figure 2a, the battery pack 112 may be a battery pack for an electric vehicle. However, this is merely an example, and the battery pack 112 may instead be used to provide and store electrical energy for any kind of industrial, commercial, or domestic application, such as for energy storage and delivery, for example, in smart grids, home energy storage and/or electricity grid load balancing.

The battery pack 112 includes a housing 114 defining a cavity 116. In Figure 2a, the battery pack 112 is cuboid in shape, with a hollow interior corresponding to the cavity 116. This this is merely an example, though, and in other cases, the battery pack may take any suitable shape.

The housing 114 of the battery pack 112 of Figure 2a is substantially rigid. The housing 114 is for example rigid, inflexible or otherwise unbending to the extent that the housing does not deform or does not appreciably deform during use of the battery pack. The housing 114 in this case may withstand external or internal pressure up to an expected operational limit without bending to a degree which affects performance of the battery pack 112. In other cases, though, the battery pack may have a housing which is not substantially rigid.

In Figure 2a, the cavity 116 may be considered to be a chamber or space within the housing 114 of the battery pack 112 for containing batteries, in this case pouch cells 200. In Figure 2a, the battery pack 112 includes a plurality of pouch cells 200a-200e (collectively referred to with the reference numeral 200) within the cavity 116. The pouch cells 200 are the same as the pouch cell 100 of Figure 1, except that the first terminals 208b-208e (collectively referred to with the reference numeral 208) and the second terminals 210a-210e (collectively referred to with reference numeral 210) are at opposite ends of the pouch cells 200 of Figure 2, rather than at the same end. The pouch cells 200 are connected in series via the first and second terminals 208, 210. The suffix of the first and second terminals 208, 210 indicates the pouch cell 200 to which the first and second terminals 208, 210 belong. In this example, the first terminal of the first pouch cell 200a acts as an electrical connection 124 between the first pouch cell 200a and a first electrical component 122a, which the electrical connection 124 is configured to be severed due to movement of the first pouch cell 200a that satisfies a predetermined condition, as discussed further below. The first terminal of the first pouch cell 200a is labelled as the electrical connection 124 for ease of reference. The electrical connection 124 is indicated in bold in Figure 2a, to highlight the position of the electrical connection 124 In Figure 2a, the electrical connection 124 is for connection between the first pouch cell 200a and the first electrical component 122a. In this case, the first electrical component 122a is a suitable connector for the connecting the battery pack 112 to a further electrical component, such as an electrode, lead or tab. In other cases, though, the electrical connection 124 may connect the first pouch cell 200a to an electrical component that is external to the battery pack 112. Such an electrical component may be any electrical component to which electrical energy stored in the battery pack 112 is to be supplied or which may be used to recharge the battery pack 112. As explained above, the electrical connection 124 in Figure 2a is the cell tab of the first pouch cell 200a but in other cases the electrical connection may be a further electrically conductive element connected to the cell tab of the first pouch cell 200a. In some cases, the electrical connection 124 may indirectly connect a pouch cell 200 and an electrical component, for example via at least one further electrical element.

The battery pack 112 may be further connected to a further electrical component, which may be external to the battery pack 112, via a second electrical component 122b, which in this case is connected to a fifth pouch cell 200e via a second terminal 210e of the fifth pouch cell 200e. In Figure 2a, the second electrical component 122b in this case is an electrically conductive element arranged on the surface 118 of the housing 114, but this is merely an example.

The battery pack 112 can be a safety hazard if a pouch cell 200 suffers from a fault or is misused or otherwise abused. This can lead to increasing quantities of gas being generated within the pouch cell 200, which can cause high pressure and/or high temperature within the pouch cell 200. This may lead to thermal runaway if current continues to flow through the pouch cell 200, which can result in ignition of the gas or an explosion of the pouch cell 200.

In Figure 2a, the electrical connection 124 is configured to be severed by a movement 120 of the pouch cell (in this case, the first pouch cell 200a) relative to the surface 118 of the housing 114 within the cavity 116 which satisfies a predetermined condition. Movement 120 of the first pouch cell 200a may occur during normal or otherwise expected use of the battery pack 112. For example, the movement of the first pouch cell 200a may be due to generation of gas within the first pouch cell 200a or within at least one other pouch cell 200, which may cause the first or other pouch cell 200 to expand. A relatively small amount of gas generation may be expected to occur during charging of a pouch cell 200. The pouch cell 200 may subsequently deflate during discharge of the pouch cell 200. However, the generation of a quantity of gas larger than this amount may indicate that the pouch cell 200 is faulty or has been subject to an abuse condition such as overcharging, excessive temperature and/or excessive current.

To avoid unduly interrupting current flow through the battery pack 112 during usual or otherwise expected operation of the battery pack 112, the electrical connection 124 may not be severed due to movement 120 of the first pouch cell 200a which is less than or equal to a predetermined amount. However, movement 120 of the first pouch cell 200a which exceeds the predetermined amount may cause severance of the electrical connection 124. The predetermined amount of movement may correspond to an expected amount of movement during normal use of the battery pack 112, which may be exceeded where the first pouch cell 200a or another pouch cell 200 is faulty or abused (e.g. due to excessive gas generation within the first pouch cell 200a or another pouch cell 200). In this way, current may be prevented from flowing through the first pouch cell 200a, and through the battery pack 112, where the movement 120 of the first pouch cell 200a indicates failure of the at least one of the pouch cells 200 (either due to a fault or misuse). This may improve the safety of the battery pack 112, by reducing the risk of gas generated within the pouch cells 200 from igniting or exploding, which may otherwise occur if current continues to flow through the battery pack 112.

The movement 120 in this case is away from the surface 118 of the housing 114. In Figure 2a, the first electrical component 122a to which the electrical connection 124 is connected is an electrically conductive post within the cavity 116. The first electrical component 122a in this case allows the battery pack 112 to be connected to an external electrical component, which is outside the battery pack 112. The first electrical component 122a is coupled to the surface 118 of the housing 114 and is rigid such that the electrical component 122a does not deform or stretch due to movement 120 of the electrical connection 124 away from the surface 118 of the housing 114 and away from the support element 112. This is merely an example, though, and in other examples, the first electrical component may instead be a conductive portion of the surface 118 of the housing 114 or a conductive element with a different form and/or structure than a post.

In this case, as the electrical connection 124 moves away from the surface 118 of the housing 114 due to movement of the first pouch cell 200a, the electrical connection 124 is placed under increasing tension. The electrical connection 124 is severed when the tension applied to the electrical connection 124 exceeds a given tension. This for example corresponds to a predetermined condition for severance of the electrical connection 124, which may be satisfied when the movement 120 of the first pouch cell 200a exceeds the predetermined amount of movement.

With this arrangement, the electrical connection 124 is severed by the movement of the first pouch cell 200a itself. This therefore obviates the need for a more complex arrangement for interrupting current through the battery pack 112 when the first pouch cell 200a is faulty or misused. The mass of the battery pack 112 may therefore be reduced. This arrangement is simple and straightforward to manufacture and may therefore be less likely to fail than more complex arrangements. The battery pack 112 may be more robust and have a longer lifetime than otherwise.

In Figure 2a, the first pouch cell 200a is constrained to move in a predetermined direction relative to the surface 118 of the housing 114. In this case, the predetermined direction is substantially perpendicular to a plane of the surface 118 of the housing 114, although this is merely an example. A direction may be considered substantially perpendicular where it is for example perpendicular, perpendicular within manufacturing or measurement tolerances, or approximately perpendicular, such as within 5 or 10 degrees of being perpendicular. The first pouch cell 200a is constrained to move away from the surface 118 of the housing 114 in Figure 2a by virtue of the direction of expansion of the casing of the first pouch cell 200a. As the front and rear portions of the casing of the first pouch cell 200a are connected at their peripheries, the expansion of the casing of the first pouch cell 200a, e.g. due to generation of gas within the first pouch cell 200a, is predominantly towards the front or rear of the first pouch cell 200a (which is in an upwards and downwards direction in Figure 2a). However, as the housing 114 of the battery pack 112 is substantially rigid in this example, this limits movement of the first pouch cell 200a in the downwards direction. The expansion of the first pouch cell 200a therefore causes the first pouch cell 200a to move mainly away from the surface 118 of the housing 114. The movement 120 of the first pouch cell 200a is more predictable than otherwise. Various properties of the electrical connection 124, such as its width and/or length, may be selected appropriately so that movement 120 of the first pouch cell 200a within expected bounds does not cause severance of the electrical connection 124, but that movement 120 beyond these bounds causes the electrical connection 124 to be severed.

In Figure 2a, the pouch cells 200 are arranged as a stack of pouch cells 200 on a surface 118 of the housing 114. In this way, movement of one of the pouch cells 200 may cause movement of at least one other pouch cell 200 within the stack. For example, if a second pouch cell 200b expands, the first pouch cell 200a will move away from the surface 118 of the housing 114. In this way, the expansion of the second pouch cell 200b may cause severance of the electrical connection 124 between the first pouch cell 200a and the electrical component 122a. This is due to the consequential movement of the first pouch cell 200a due to the expansion of the second pouch cell 200b (which is beneath the first pouch cell 200a in Figure 2a). For example, the first pouch cell 200a may move due to at least one of generation of gas within the second pouch cell 200b and expansion of the second pouch cell 200b (or any of the other pouch cells beneath the first pouch cell 200a). This may reduce the complexity of the battery pack 112, by obviating the need for suitable configured electrical connection for each pouch cell 200. In Figure 2a, the electrical connection 124 is in the form of an electrode, although in other cases the electrical connection may comprise an electrode in addition to at least one further electrically conductive element. In Figure 2a, a first portion of the electrode is connected to the first pouch cell 200a and a second portion of the electrode is connected to the housing 114. Two elements may be considered to be connected to each other where they are directly connected, without intervening elements, or whether they are indirectly connected, via one or more intervening elements. In the example of Figure 2a, the second portion of the electrode is indirectly connected to the housing 114 via the first electrical component 122a. in other cases, though, the second portion of the electrode may be directly connected to the housing 114. This may be the case where the electrical component is integral to or arranged on a surface of the housing 114, such as the surface 118 on which the stack of pouch cells 200 is arranged.

In Figure 2a, the electrode which forms the electrical connection 124 is substantially rigid. The electrode may be sufficiently rigid to facilitate severance of the electrode due to the movement 120 of the first pouch cell 200a which satisfies the predetermined condition. Hence, in Figure 2a, the electrode is sufficiently brittle that the electrode breaks rather than stretching when the predetermined condition is satisfied. This improves severance of the electrical connection, and improves the safety of the battery pack 112, without increasing complexity.

Figure 2b shows schematically the battery pack 112 of Figure 2a with the pouch cells 200 omitted in order to more clearly illustrate various regions of the battery pack 112. In Figure 2b, the cavity 116 includes a battery region 126 and an expansion region 128. A battery is within the battery region 126, which in this case includes the pouch cells 200. In this case, at least one of the battery or the housing 114 are adapted so that any expansion of the battery, in use, is towards the expansion region 128.

In Figure 2b, the cavity 116 includes a buffer region HO which is between the battery region 126 and the expansion region 128. Expansion of the battery occurs into the buffer region 130 during usual or otherwise expected operation of the battery pack 112, for example during charging and discharging the battery pack 112. The battery is therefore located in the battery region 126 and/or within a combination of the battery region 126 and the buffer region 130 where the battery is not faulty or misused. For example, expansion of the buffer beyond the battery region 126 but which does not exceed an overtemperature, overcharge and overcurrent condition is within the buffer region 130 in this case. This therefore allows expansion of the battery under expected operating conditions to continue uninterrupted.

If, however, the battery is faulty and/or misused, for example if at least one of an overtemperature condition, an overcharge condition or an overcurrent condition is exceeded, the battery and/or the housing 114 are adapted so that the battery expands into the expansion region 128. The electrical connection 124 is arranged to break if the battery expands into the expansion region 128, as described with reference to Figure 2a. For example, expansion of the battery into the expansion region 128 may be considered to correspond to movement 120 of the battery (such as at least one of the pouch cells 120) that satisfies a predetermined condition.

Referring now to Figure 2c, Figure 2c shows schematically the battery pack 112 of Figures 2a and 2b after the first pouch cell 200a has undergone movement which does not satisfy the predetermined condition to cause severance of the electrical connection 124. The first pouch cell 200a has moved in Figure 2c compared to a position of the first pouch cell 200a in Figure 2a due to expansion of the first pouch cell 200a, e.g. due to generation of gas within the first pouch cell 200a. The electrical connection 124 is under tension in Figure 2c. However, the tension applied to the electrical connection 124 is not sufficient to cause severance of the electrical connection 124. In this case, the first pouch cell 200a has expanded into the buffer region 130 of the battery pack 112, but has not yet expanded into the expansion region 128.

Figure 2d shows schematically the battery pack 112 after the first pouch cell 200a has expanded into the expansion region 128. The movement of the first pouch cell 200a relative to the surface 118 of the housing 114 satisfies the predetermined condition for severance of the electrical connection 124. The electrical connection 124 has therefore been severed, and current has therefore ceased to flow through the battery pack 112. The configuration of Figure 2d may be obtained if the first pouch cell 200a is faulty and/or has been subjected to an abuse condition such as an overtemperature, overcurrent and/or overcharge condition. The electrical connection 124 may be severed similarly due to movement of the first pouch cell 200a due to expansion of a pouch cell beneath the first pouch cell 200a, such as the second pouch cell 200b.

In the examples of Figures 2c and 2d, the second terminals 210a, 210b of the first and second pouch cells 200a, 200b is illustrated as being stretched rather than breaking when the first pouch cell 200a expands. This may be the case if the second terminals 210a, 2106 are sufficiently elastic. In other examples, though, at least one of the second terminals 210a, 210b may also or alternatively break due to movement of the first pouch cell 200a that satisfies the predetermined condition. In such cases, the at least one of the second terminals 210a, 210b may be considered to correspond to an electrical connection as described herein.

Figure 3 shows schematically a battery pack 312 according to further examples. The battery pack 312 of Figure 3 is the same as the battery pack 112 of Figures 2a and 2b except for the location of the electrical connection 324. Features of Figure 3 that are similar to corresponding features of Figures 2a and 2b are labelled with the same reference numeral but prefixed by a 3. Corresponding descriptions are to be taken to apply.

Figure 3 shows an example in which the electrical connection 324 is between two pouch cells 300 of the battery pack 312. In Figure 3, the electrical connection 324 is between the first pouch cell 300a and the second pouch cell 300b and therefore replaces the second terminals of the first and second pouch cells 300a, 300b. In other cases, though, a similar electrical connection may be between other pouch cells of the battery pack in addition to or instead of being between the first and second pouch cells 300a, 300b. Furthermore, an electrical connection between pouch cells may be used in addition to or instead of an electrical connection between a pouch cell and an electrical component. This may further improve the safety of the battery pack 312.

The electrical connection 324 of Figure 3 otherwise operates similarly to the electrical connection 124 of Figures 2a to 2d. The electrical connection 324 is configured to be severed by a movement of the pouch cell (in this case either the first pouch cell 300a or the second pouch cell 300b) relative to the surface 314 of the housing 318 within the cavity 316, which satisfies the predetermined condition discussed above. Current may therefore be prevented from flowing through the battery pack 312 by breaking the connection between two pouch cells 300 (e.g. pouch cells connected in series) rather than or in addition to breaking the connection between a pouch cell and a further electrical component. For example, the electrical connection 324 may be severed if the battery, such as the pouch cells 300, expand into an expansion region of the cavity 316, e.g. as described with reference to Figure 2b. In these cases, the other connections between the pouch cells, the first pouch cell 300a and the first electrical component 322a and/or the fifth pouch cell 300e and the second electrical component 322b need not be severed if the predetermined condition is satisfied (although they may be in some cases). Instead, these connections may be sufficiently elastic and/or long that these connections stretch and/or not placed under tension when the predetermined condition is satisfied. For example, it may be sufficient if the battery pack 312 includes at least one electrical connection that is configured to be severed due to the movement that satisfies the predetermined condition. The number of electrical connections that are configured to be severed in this way may be selected appropriately depending on an intended use of the battery pack 312 and/or to minimise complexity of the battery pack 312.

Figure 4 shows schematically a battery pack 412 according to further examples. The battery pack 412 of Figure 4 is the same as the battery pack 112 of Figures 2a and 2b except for the electrical connection 424. Features of Figure 4 that are similar to corresponding features of Figures 2a and 2b are labelled with the same reference numeral but prefixed by a 4. Corresponding descriptions are to be taken to apply. In Figure 2a, the electrical connection 124 is a straight electrode, which connects the first pouch cell 200a to the first electrical component 122a. A straight electrode may provide an efficient connection between the first pouch cell 200a and the first electrical component 122a. In the example of Figure 4, though, the electrical connection is formed by an electrode 424 which is twisted. A twisted electrode for example has at least one bend or other turn along a length of the electrode. For example, the electrode 424 may have a helical form. In Figure 4, the electrode 424 has a plurality of twists. A twisted electrode may aid severance of the electrical connection 424 due to the movement 420 of the first pouch cell 400a. For example, the twists in the electrode 424 may weaken the electrode, so that it breaks more easily if the movement 420 satisfies the predetermined condition.

Figure 5 shows schematically a portion of battery pack 512 according to further examples. The battery pack 512 of Figure 5 includes similar features to those of the battery pack 112 of Figures 2a and 2b. Features of Figure 5 that are similar to corresponding features of Figures 2a and 2b are labelled with the same reference numeral but prefixed by a 5. Corresponding descriptions are to be taken to apply.

The battery pack 512 of Figure 5 includes a pouch cell 500 arranged within a cavity of the battery pack which is defined by a housing 514. The battery pack 512 of Figure 5 may include further pouch cells (not shown). The pouch cell 500 is connected to an electrical component 522 by an electrical connection 524, which may have features similar to or the same as those of the electrical connections described with reference to the other examples. The electrical connection 524 is configured to be severed by movement 520 of the pouch cell 500 that satisfies a predetermined condition, as described with reference to the examples above. In this case, the electrical connection 524 is in the form of an electrode which is loosely connected between the pouch cell 500 and the electrical component 522, but this is merely an example.

In Figure 5, the battery pack 512 comprises a cutting element 132 configured to sever the electrical connection 524 due to the movement 520 of the pouch cell 500. The cutting element 132 is for example a bladed or otherwise sharp element that is sufficiently sharp to break the electrical connection 524 when the predetermined condition is satisfied.

In this case, the movement 520 of the pouch cell 500 causes movement of the electrical connection 524 towards the cutting element 132, to sever the electrical connection 524. The electrical connection 524 may therefore be severed by the movement of the electrical connection 524 itself, rather than by motion of the cutting element. This arrangement may be less complex and/or less likely to fail than other arrangements in which the cutting element is configured to move to sever the electrical connection 524. For example, the cutting element 132 may remain static or otherwise stationary during breaking of the electrical connection 524.

The cutting element 132 in Figure 5 is configured to sever the electrical connection 524 due to the movement of the pouch cell 500 by applying a shearing force to the electrical connection 524. In other words, the electrical connection 524 may be sheared to break the electrical connection 524, rather than tearing or breaking a weakened material or a material that is designed to easily yield on impact. For example, the electrical connection 524 may be non-frangible, and may therefore be resistant to breaking into fragments. Such an electrical connection 524 may be more robust and less likely to fail than a frangible electrical connection. The lifetime of the battery 512 may therefore be increased. Furthermore, this may obviate the need to provide an electrical connection that is specifically adapted to easily break into fragments. This may simplify manufacture of the battery pack 512. For example, an existing electrical connection may be used as the electrical connection configured to be severed when the predetermined condition is satisfied by suitable arrangement of the electrical connection with respect to other elements of the battery pack 512.

The cutting element 132 of Figure 5 is substantially electrically non-conductive. In this way, the cutting element 132 maybe sufficiently non-conductive, such as sufficiently electrically insulating, to prevent or limit flow of electrical current through the pouch cell 500 via the cutting element 132 (for example if the electrical connection 524 remains in contact with the cutting element 132 after severance of the electrical connection 524). This improves the safety of the battery pack 512.

The cutting element 132 may be integral to the battery pack 512, such as formed as part of the battery pack 512 rather than a separate or other element. In Figure 5, the cutting element 132 protrudes from an upper inner surface of the housing 514 (not shown) and protrudes downwards, towards the electrical connection 524. In other examples, the cutting element 132 may protrude from a different surface of the battery pack 512. For example, the cutting element 132 may be a sharp notch sticking out or otherwise extending from an inner surface within the cavity of the battery pack 512. In other cases, the cutting element 132 may be plate, which may be between pouch cells to sever an electrical connection between the pouch cells if the predetermined condition is met.

It is to be appreciated that a cutting element such as that of Figure 5 may be used with any of the examples herein.

The above examples are to be understood as illustrative examples. Further examples are envisaged It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the accompanying claims

Claims

CLAIMSI. A battery pack comprising: a housing defining a cavity a pouch cell within the cavity; and an electrical connection between the pouch cell and at least one of: a further pouch cell of the battery pack, or another electrical component; wherein the electrical connection is configured to be severed by a movement of the pouch cell, relative to a surface of the housing within the cavity, which satisfies a predetermined condition.
2. The battery pack according to claim 1, wherein the movement of the pouch cell comprises movement of the pouch cell due to generation of gas within the pouch cell.
3. The battery pack according to claim 1 or claim 2, wherein the movement of the pouch cell comprises movement of the pouch cell due to expansion of the pouch cell.
4. The battery pack according to any one of claims 1 to 3, wherein the movement of the pouch cell comprises movement of the pouch cell away from the surface of the housing.
The battery pack according to any one of claims 1 to 4, wherein movement of the pouch cell which exceeds a predetermined amount satisfies the predetermined condition.
6. The battery pack according to any one of claims 1 to 5, wherein the pouch cell is constrained to move in a predetermined direction relative to the surface of the housing
7. The battery pack according to claim 6, wherein the predetermined direction is substantially perpendicular to a plane of the surface of the housing.
8. The battery pack according to any one of claims 1 to 7, wherein the pouch cell is a first pouch cell, the battery pack comprises a second pouch cell electrically connected to the first pouch cell, and the movement of the first pouch cell comprises movement of the first pouch cell due to at least one of generation of gas within the second pouch cell; and expansion of the second pouch cell, wherein optionally the second pouch cell is the further pouch cell.
9. The battery pack according to any one of claims 1 to 8, wherein the electrical connection comprises an electrode, wherein a first portion of the electrode is connected to the pouch cell and a second portion of the electrode is connected to the housing or the further pouch cell.
10. The battery pack according to claim 9, wherein the electrode is twisted.
11 The battery pack according to claim 9 or claim 10, wherein the electrode is substantially rigid
12 The battery pack according to any one of claims 1 to 11, wherein the battery pack comprises a cutting element configured to sever the electrical connection due to the movement of the pouch cell.
13 The battery pack according to claim 12, wherein the movement of the pouch cell causes movement of the electrical connection towards the cutting element, to sever the electrical connection.
14. The battery pack according to claim 12 or claim 13, wherein the cutting element is substantially electrically non-conductive.
15. The battery pack according to any one of claims 12 to 14, wherein the cutting element is integral to the battery pack.
16. The battery pack according to any one of claims 12 to 15, wherein the cutting element is configured to sever the electrical connection due to the movement of the pouch cell by applying a shearing force to the electrical connection, wherein the electrical connection is non-frangibleS
17. The battery pack according to any one of claims 1 to 16, wherein the housing is substantially rigid.
18. The battery pack according to any one of claims Ito 17, wherein the electrical component is external to the battery pack.
19. The battery pack according to any one of claims 1 to 18, wherein the battery pack comprises a stack of pouch cells on the surface, the stack of pouch cells comprising the pouch cell.
20. A battery pack comprising: a housing defining a cavity including a battery region and an expansion region; a battery within the battery region of the cavity, the battery including one or more pouch cells, at least one of the battery or the housing being adapted so that any expansion of the battery, in use, is towards the expansion region; and an electrical connection between at least one of: the battery and an electrical contact of the battery pack, or two pouch cells of the battery, wherein the electrical connection is arranged to break if the battery expands into the expansion region of the cavity.
21. The battery pack according to claim 20, wherein at least one of the battery or the housing are adapted so that the battery expands into the expansion region of the cavity due to the battery exceeding at least one of an overtemperature condition, an overcharge condition, or an overcurrent condition
22. The battery pack according to claim 21, wherein the cavity comprises a buffer region between the battery region and the expansion region, and the least one of the battery or the housing are adapted so that expansion of the battery which does not exceed the overtemperature, overcharge, and overcurrent condition is within the buffer region.