Electrically conductive plate

Abstract

There is provided an electrically conductive plate configured to electrically connect to each of a first plurality of electrical cells. The plate comprises a venting channel formed in the plate. The venting is arranged such that when the plate is connected to the cells in use, the venting channel is configured to be in fluid communication with a vent of each cell to provide a fluid pathway between the vent of each cell and a space external to the cells.

Description

[0001] ELECTRICALLY CONDUCTIVE PLATE

[0002] FIELD

[0003] The present invention relates to an electrically conductive plate configured to electrically connect to each of a first plurality of electrical cells, and in particular but not exclusively to an electrically conductive plate for inhibiting or preventing thermal propagation within a battery pack.

[0004] BACKGROUND

[0005] Battery packs for electric vehicles are typically made using secondary chemical cells (i.e., rechargeable cells), including Lithium Ion and Lithium Iron Phosphate. The cells may be connected in series and / or parallel to accommodate the voltage, power and energy requirements of the vehicle.

[0006] When using secondary chemical cells there is a risk that the anode and cathode materials of a cell can come into contact with one another causing a thermal runaway event. This usually occurs due to mechanical failure of the membrane that separates the anode and cathode chemistries from one another. Causes of failure can include manufacturing defects, poor battery management (including over-charging and short-circuiting), and overheating.

[0007] In a thermal runaway event the temperature of the cell can rapidly exceed 1500°C and large volumes of hydrocarbon gas are released under pressure. This can cause surrounding or adjacent cells in a battery pack to overheat and also enter thermal runaway, propagating the thermal runaway across the battery pack.

[0008] The present invention has been devised with the foregoing in mind.

[0009] SUMMARY

[0010] According to a first aspect, there is provided an electrically conductive plate configured to electrically connect to each of a first plurality of electrical cells. The plate may comprise a venting channel formed in the plate. The venting channel may be arranged or located such that when the plate is connected to the cells in use, the venting channel is configured to be in fluid communication with a vent of each cell to provide a fluid pathway between the vent of each cell and a space external to the cells.

[0011] That may enable gas from a failed cell to be vented to an external environment without causing overheating of other cells, which may inhibit or prevent propagation of thermal runaway to the other cells. Inhibiting or preventing thermal runaway propagation between cells in a battery may in turn may allow a spacing between adjacent cells to be reduced. Reducing a spacing between adjacent cells may reduce both a volume and mass of a battery (e.g., for a given capacity). Mass of the battery may be reduced by reducing the amount of material required to separate the cells. Reducing or minimising a volume and / or mass of a battery pack may improve performance of a battery powered vehicle by increasing or maximising the load carrying capacity and / or range of a vehicle.

[0012] The plate may further comprise a plurality of apertures. The apertures may extend at least partially through a thickness of the plate. The apertures may be arranged or located such that when the plate is connected to the cells in use, each aperture is configured to provide a fluid pathway between the vent of a respective cell and the venting channel. That may improve isolation between the failed cell and adjacent cells by reducing direct exposure of other cells to the vented gas from the failed cell (for example, through the venting channel) during venting, which may further reduce a risk of thermal runaway propagation. The apertures may be arranged or located such that when the plate is connected to the cells in use, each aperture may substantially align with a respective cell to provide the fluid pathway between the vent of the cell and the venting channel.

[0013] The venting channel may have or comprise a larger cross-sectional area than each of the apertures. That may result in the fluid pathway between the vent of each cell and the external space increasing with increased distance from the vent, which may allow the gas to continuously expand to improve cooling during venting.

[0014] Each of the apertures and the venting channel may have a cross-sectional area equal to or larger than a cross-sectional area of the vent of each cell to which the plate is connected in use. The venting channel may be formed in a surface of the plate opposite a surface of the plate which is adjacent the cells when the plate is connected to the cells in use. A first surface of the plate may be adjacent the cells when the plate is connected to the cells in use, and the venting channel may be formed in an opposing second surface of the plate. That may increase separation or isolation between the cells and the venting channel during venting, which may further reduce a risk of thermal runaway propagation.

[0015] The plate may further comprise a plurality of recessed portions formed in a surface of the plate which is adjacent the cells when the plate is connected to the cells in use. The plate may provide a sufficient thermal mass for heat absorption adjacent a failed cell (for example, adjacent a vent of a failed cell). The recessed portions may provide an increased surface area of the plate adjacent a failed cell (for example, adjacent a vent of a failed cell) for rapid local heat transfer to the plate during venting, which may locally reduce a temperature of emitted material quickly. The recessed portions may also reduce a total mass of the plate, which may improve mechanical and electrical performance of the battery. The recessed portions may be arranged or located such that when the plate is connected to the cells in use, each recessed portion may be configured to substantially align with a respective cell. The recessed portion may have or comprise a tapered, funnelled, angled or rounded opening. That may guide material from a failed cell into the recessed portion during venting without restricting a flow of the material.

[0016] Each of the apertures may be located in a respective recessed portion.

[0017] Each recessed portion may have a substantially similar cross-sectional area to the cell with which it is substantially aligned.

[0018] The plate may further comprise a plurality of one-way valves. The one-way valves may be arranged or located such that when the plate is connected to the cells in use, each one-way valve is disposed in a fluid pathway between the vent of a respective cell and the venting channel. The one-way valves may allow flow of material away from a failed cell but prevent flow of material towards adjacent cells, which may further reduce a risk of thermal runaway propagation. The one-way valves may be arranged or located such that when the plate is connected to the cells in use, each one-way valve is configured to substantially align with a respective cell. Each of the one-way valves may be disposed within a respective recessed portion. Each of the one-way valves may be or comprise a sheet or plate of material disposed within a respective recessed portion. Each sheet or plate of material may be configured to move within the recessed portion to open or close the fluid pathway between the vent of a respective cell and the venting channel.

[0019] The plate may further comprise a plurality of intumescent portions. The intumescent portions may be arranged or located such that when the plate is connected to the cells in use, each intumescent portion is disposed in a fluid pathway between the vent of a respective cell and the venting channel. That may provide an additional thermal barrier acting to reduce heat transfer from the vented gas expelled by the failed cell to adjacent cells. The intumescent portions may be arranged or located such that when the plate is connected to the cells in use, each intumescent portion is configured to substantially align with a respective cell.

[0020] Each of the intumescent portions is disposed within a respective recessed portion. Each of the intumescent portions may be or comprise a sheet or plate of material disposed within a respective recessed portion.

[0021] Each of the intumescent portions may form a part of a respective one-way valve.

[0022] The plate may further comprise a cooling channel configured to direct a flow of coolant across the plate.

[0023] The cooling channel and the venting channel may intersect one another. That may provide an additional cooling mechanism to transfer heat from the vented gas, which may further reduce a risk of thermal runaway propagation.

[0024] The plate may comprise a first plate portion in which the venting channel is formed. The first plate portion may be configured to electrically connect to a positive end or terminal of each of the first plurality of cells. The plate may comprise a second plate portion. The second plate portion may be configured to electrically to a negative end or terminal of each of a second plurality of cells. The second plate portion may have or comprise a greater mass than the first plate portion. That may enable greater heat transfer away from the negative end or terminal of each cell and also provide mechanical reinforcement to the negative end or terminal of each cell. That may reduce a likelihood of rupture or failure at the negative end or terminal of each cell in turn increasing a likelihood of failure at the positive end or terminal of a cell. That may enable location or provision of means for management of thermal runaway events primarily or fully at or adjacent the positive end or terminal of each cell. Concentrating the provision of means for managing thermal runaway events may reduce a volume and / or mass of a battery. That may be particularly beneficial for cylindrical cells, which whilst theoretically may rupture or fail at any location, are inherently more likely to eject gas during failure through vents positioned at a positive end terminal of the cell. The provision of a venting channel to enable material from a failed cell to be exhausted may also reduce a likelihood the vents at the positive end terminal of the cell become blocked in use (which may otherwise cause a cell to rupture at a different location, if the vents are unable to allow material to be emitted from the cell).

[0025] Each of the first plurality of cells and the second plurality of cells may have or comprise the same number of cells.

[0026] The second plate portion may comprise one or more structures configured to retain each of the second plurality of cells in a desired position relative to the second plate portion.

[0027] The second plate portion may be configured to structurally support each of the second plurality of cells adjacent the negative terminals of the second plurality of cells. The second plate portion may comprise one or more structures configured to at least partially surround an end of each of the second plurality of cells. That may provide further mechanical reinforcement to the negative terminal of each cell.

[0028] According to a second aspect, there is provided a battery. The battery may comprise a plurality of electrical cells. Each cell may comprise a vent. The battery may also comprise an electrically conductive plate electrically connected to each of the plurality of cells. The plate may be or comprise the electrically conductive plate of the first aspect.

[0029] Each of the cells may be or comprise a cylindrical cell. The plurality of cells may be arranged in a regular array. The battery of the second aspect may comprise one or more features and / or advantages of the electrically conductive plate of the first aspect, and vice versa.

[0030] According to a third aspect, there is provided a battery. The battery may comprise a plurality of cylindrical cells. The battery may also comprise a first electrically conductive plate electrically connected to a positive end of each cell. The battery may further comprise a second electrically conductive plate electrically connected to a negative end of each cell. The second plate may have or comprise a greater mass than the first plate.

[0031] The second electrically conductive plate may be directly coupled to the negative end of each cell. Direct coupling may comprise direct physical contact between the second plate and the negative end of each cell.

[0032] The second plate may comprise one or more structures configured to retain each cell in a desired position relative to the second plate.

[0033] The second plate may be configured to structurally support each of the cells adjacent the negative terminals of the cells. The second plate may comprise one or more structures configured to at least partially surround an end of each of the cells.

[0034] The first plate may be or comprise the electrically conductive plate of the first aspect.

[0035] According to a fourth aspect, there is provided an electrically conductive plate configured to electrically connect to each of a plurality of cells. The plate may comprise a first plate portion. The first plate portion may be configured to electrically connect to a positive terminal of each of a first subset of the plurality of cells. The plate may also comprise a second plate portion. The second plate portion may be configured to electrically connect to a negative terminal of each of a second subset of the plurality of cells. The second plate portion may comprise a greater mass than the first plate portion.

[0036] The second plate portion may comprise one or more structures configured to retain each cell of the second subset in a desired position relative to the second plate portion. The second plate portion may be configured to structurally support each cell of the second subset adjacent the negative terminals of the cells. The second plate portion may comprise one or more structures configured to at least partially surround an end of each cell of the second subset.

[0037] The plate of the fourth aspect may comprise one or more features and / or advantages of the electrically conductive plate of the first aspect, the battery of the second aspect or the third aspect, and vice versa.

[0038] According to a fifth aspect there is provided an electric vehicle comprising a battery. The battery may be or comprise the battery of the second aspect or the third aspect. The battery may comprise the electrically conductive plate of the first aspect or the fourth aspect.

[0039] The electric vehicle may be an automobile, for example a car, a truck, a van or a lorry.

[0040] Features which are described in the context of separate aspects and embodiments of the invention may be used together and / or be interchangeable wherever possible. Similarly, where features are described in the context of a single embodiment for brevity, those features may also be provided separately or in any suitable sub-combination.

[0041] BRIEF DESCRIPTION OF DRAWINGS

[0042] Embodiments of the present invention will now be described by way of example only with reference to the following drawings in which:

[0043] FIG. 1 shows an embodiment of a battery pack in accordance with the present invention;

[0044] FIGs. 2A and 2B show a module or battery of the battery pack shown in FIG. 1;

[0045] FIG. 3 shows an electrical cell of the module shown in FIGs. 2A and 2B; FIGs. 4A and 4B show the top and bottom surfaces of a first portion of an electrically conductive plate connected to positive terminals of the cells in the module shown in FIGS. 2 A and 2B;

[0046] FIG. 5 shows a cross-sectional view through the first plate portion shown in FIGS. 4A and 4B including a one-way valve mechanism;

[0047] FIGs. 6A and 6B show another embodiment of a first portion of an electrically conductive plate configured to be connected to positive terminals of cells in a module of a battery pack; and

[0048] FIG. 7 shows an electrically conductive plate of the module shown in FIGS. 2A and 2B comprising a first plate portion and a second plate portion.

[0049] Like reference numerals in different Figures may represent like elements.

[0050] DETAILED DESCRIPTION

[0051] Figure 1 shows an embodiment of a battery pack 100. The battery pack 100 comprises a plurality of batteries or modules 105. In the embodiment shown, the battery pack 100 comprises one hundred and ten modules 105, with eleven strings 108 each formed of ten modules 105. The battery pack 100 may alternatively comprise any suitable number of batteries or modules 105. Each string 108 is oriented to extend along a length of the battery pack 100 (substantially from left to right or right to left), with the modules 105 in each string 108 connected in series along the length of the string 108, although that is not essential. In the embodiment shown, each module 105 comprises a plurality of cylindrical cells 140 arranged in a regular, ordered array, with each cell 140 having a diameter of 21 mm and an axial length of 70 mm. However, it will be appreciated each module 105 may alternatively comprise a plurality of cells of any suitable size, shape or configuration, arranged in any suitable manner.

[0052] Each module 105 comprises a pair of electrically conductive plates (shown in greater detail in Figure 2) between which the plurality of cells 140 are located. The cells 140 are electrically connected in parallel between the electrically conductive plates. The electrically conductive plates function as busbars and may be referred to as such throughout the present disclosure. The electrically conductive plates each comprise a substantially monolithic structure formed from a conductive material such as a metal or metal alloy material, for example aluminium alloy or copper. The electrically conductive plates of each module 105 together provide a respective top surface 120 and a bottom surface 130 of the battery pack 100. The top surface 120 and the bottom surface 130 each provide a bonding surface to which a sheet or panel of material (not shown) may be secured. The respective panels of material may be secured to the top surface 120 and the bottom surface 130 in any suitable manner, for example using an adhesive, one or more fasteners, welding etc. The battery pack 100 together with the panels effectively forms a structural element having a layered or sandwich construction, with the battery pack 100 itself acting as a core material of the layered construction.

[0053] Each string 108 of modules 105 comprises a terminal 110 to allow an external electrical connection to be made to the battery pack 100, for example to connect the battery pack 100 to a load. In the embodiment shown, each string 108 comprises a terminal 110 at either end of the string 108. That may enable separation of the battery pack 100 into individual low voltage strings 108 which are safer for a user to handle. That may also enable the battery pack 100 to be configured such that the strings 108 are connected in series or parallel outside the battery pack 100. That may also enable a master disconnect to be positioned such that the battery pack 100 is electrically isolated internally (that is, no voltage is present on the terminals 110 of the battery pack 100). Alternatively, the strings 108 may be connected to one another within the battery pack 100 leaving only two terminals on the battery pack 100, for example a positive terminal and a negative terminal, or leaving four terminals 110 on the battery pack 100, for example a positive terminal, a negative terminal, and two terminals within the battery pack 100 to allow provision of a master service disconnect (which may be preferred for high voltage applications, for example above 50V).

[0054] Figures 2A and 2B show a module 105 of the battery pack 100 in more detail using an exploded view. In the embodiment shown, with the exception of the modules 105 at extreme ends of a string 108, the electrically conductive plates or busbars between which the cells 140 of the module 105 are located each comprise a first plate portion 150 and a second plate portion 155. The first plate portion 150 is arranged to connect to the positive terminals of each cell 140. The first plate portion 150 may also be referred to as the positive plate portion throughout the present disclosure. The second plate portion 155 is arranged to electrically connect to the negative terminals of each cell 140. The second plate portion 155 may also be referred to as the negative plate portion throughout the present disclosure. By providing electrically conductive plates or busbars each having a first plate portion 150 and a second plate portion 155, a series connection of the modules 105 can be achieved along the length of the string 108 by alternating the longitudinal orientation of the cells 140 in adjacent modules 105 and using the busbars to connect the positive terminals of the cells 140 of one module 105 to the negative terminals of the cells 140 of an adjacent module 105, and vice versa. It will be appreciated the electrically conductive plates at extreme ends of a string 108 may comprise only the features of a first plate portion 150 or only the features of a second plate portion 155, depending on whether the plates are connected to positive terminals of the cells 140 or negative terminals of the cells 140. It will also be appreciated a battery pack 100 comprising a single module 105, in which case the module 105 may comprise a pair of electrically conductive plates connected to the respective positive and negative terminals of the cells 140, one plate having only the features of a first plate portion 150 and the other plate having only the features of a second plate portion 155. Each module 105 comprises the same number of cells 140 to avoid some modules 105 becoming depleted sooner than others and compromising a usable capacity of the battery pack 100, although that is not essential.

[0055] In the embodiment shown, the first plate portion 150 of the busbar is electrically connected to the positive terminals of the cells 140 via a conductive sheet 160 comprising a plurality of fuses 160a formed in the sheet 160. The sheet 160 may also be referred to as a fusebar. The sheet 160 is formed from copper, although the sheet 160 may alternatively be formed from aluminium, nickel-plated aluminium or any suitable conductive material. Each fuse 160a is physically connected to the positive terminal of a respective cell 140. The fuse 160a is shown magnified in Figure 2B, taken from the square portion of Figure 2A marked in dashed lines. In the embodiment shown, the fuse 160a comprises a central portion 160b for connection with the positive terminal of the cell 140. The central portion 160b is held in place and secured to the sheet 160 via a fuse arm 160c. The fuse arm 160 has a generally spiral shape, although fuse arms having other shapes or configurations (for example straight fuse arms, arc-shaped fuse arms etc.) may alternatively be used. The structure of the fuse 160a allows for vertical movement (for example, to accommodate vertical tolerance) whilst restricting lateral movement of the central portion 160b. The fuse 160a also provides a cross-section which may melt if the current from a single cell 140 is too high, electrically disconnecting the cell 140 from the module 105. In the event of thermal runaway due to failure of a cell 140, the fuse 160a may be melted by hot gas escaping from the cell, electrically disconnecting the cell 140 from the module 105. The sheet 160 or the fuses 160a may be connected to the positive terminals of the cells 140 in any suitable manner, for example by welding (such as ultrasonic welding, laser welding, resistance welding), using a conductive adhesive etc. Alternatively, the module 105 may not comprise such a sheet or fusebar 160. The first plate portion 150 of the busbar may alternatively be directly electrically connected to the positive terminals of the cells 140.

[0056] The cells 140 in each module 105 are arranged in a regular array. In the embodiment shown, the cells 140 are arranged using hexagonal packing, although any alternative regular stacking structure may alternatively be used. Each busbar or electrically conductive plate comprises a contoured outer perimeter that substantially mirrors an external perimeter of the array of cells 140 in the module 105. That may maximise a surface area of each plate for electrical and / or thermal conduction, whilst inhibiting or preventing arcing between the plates of adjacent modules 105. For example, the contoured outer perimeter of each plate may provide a gap or space providing electrical and thermal isolation between the busbars of adjacent modules 105. In the embodiment shown, each module 105 comprises seven cells 140, although each module 105 may comprise any suitable number of cells 140.

[0057] The cells 140 within the module 150 are separated from one another to thermally and electrically isolate the cells 140 in the array from one another. A filler material is disposed in the space between the cells 140. With the filler material present in the space between the cells 140, the cells 140 may mutually reinforce one another under axial load without direct contact, which may improve axial strength of the module 105 by improving resistance of the cells 140 to buckling or barrelling under axial load. The filler material is electrically insulating to ensure safety of the module 105 and the battery pack 100 in short-circuit failure, although that is not essential (for example, depending on whether or not the cell 140 is provided with an insulating outer sleeve or surface). The filler material is also thermally insulating to inhibit thermal runaway propagation due to failure of a cell 140 (that is, thermal runaway causing failure of one cell 140 triggering thermal runaway of another cell 140 in the module 105), although that is not essential. In the embodiment shown, the filler material is an adhesive (for example, a structural adhesive) to secure the cells 140 to one another, which may improve a shear strength of the module 105, although that is not essential. It will be appreciated the module 105 may not comprise a filler material provided in the space between the separated cells 140.

[0058] The module 105 comprises a jig 165. The jig 165 is disposed over the ends of the cylindrical cells 140 adjacent the positive terminal of each cell 140 such that the jig 165 holds or secures each cell 140 in a desired position or location within the module 105. The jig 165 ensures the cells 140 are positioned correctly to provide the desired clearance from one another. That may enable the cells 140 to be positioned correctly in the module 105, for example whilst any filler material is provided (and, for example, whilst any adhesive filler cures). The jig 165 may also provide a physical barrier to prevent debris or foreign objects falling into the spaces between the cells 140.

[0059] A typical cylindrical cell 140 is shown in Figure 3. The cell 140 comprises a cylindrical body 142 which forms the negative terminal of the cell 140. The cell 140 also comprises a positive terminal 144 located at one end of the cell 140, which provides an end cap of the cylindrical cell 140. The positive terminal 144 is electrically insulated from the negative cylindrical body 142 by an insulating material (for example, a layer of plastic material) located between the cylindrical body 142 and the positive terminal 144. In the embodiment shown, the jig 165 is positioned over the ends of the cells 140 adjacent the positive terminals 144 in order to provide further electrical insulation between the negative terminal 142 and the positive terminal 144 of each cell. The jig 165 is made from a plastic material, although any suitable electrically insulating material may alternatively be used. It will be appreciated the module 105 may not comprise a jig. The cell 140 also comprises vents 146. The vents 146 surround and are positioned below the positive terminal 144. The vents 146 are provided to allow gas to be emitted from the cell 140 in the event of thermal runaway.

[0060] The first and second plate portions 150, 155 of the busbar are each configured to provide cooling and / or manage thermal runaway events (for example, causing failure of a cell 140). Figures 4A and 4B show a first plate portion 150 of a busbar. The busbar shown is configured to be used at an extreme end of a string 108 and so only comprises a first plate portion 150, although it will be appreciated the features described may be equally applicable to a busbar comprising both a first plate portion 150 and a second plate portion 155.

[0061] The first plate portion 150 comprises a plurality of venting channels 170. In the embodiment shown, the venting channels 170 are formed in a top or outer surface 120a of the first plate portion 150 (the top surface 120a forming part of the top surface 120 of the module 105 or battery pack 100). The top surface 120a is opposite a bottom or inner surface 120b of the first plate portion 150 that faces and electrically connects to the cells 140 (for example, via the fusebar or conductive sheet 160). The bottom surface 120b provides a greater surface area for electrical and thermal conduction from the cells through the first plate portion 150. The venting channels 170 are in fluid communication with the vents 146 of each cell 140. When a cell 140 fails during a thermal runaway event, a volume of high temperature gas (for example, hydrocarbon gas) is emitted by the failed cell 140. As such, when a cell 140 fails during a thermal runaway event, high temperature gas emitted from the failed cell 140 can travel along the venting channels 170 and be exhausted from the module 105 or battery pack 100 via an outlet to an external space. For example, the venting channels 170 may lead to a vent in an external casing of the battery pack 100 such as at a side of the battery pack 100. In the embodiment shown, the venting channels 170 form substantially closed channels when a plate of material is secured to the top surface 120a (as describe above with respect to Figure 1). However, it will be appreciated the venting channels 170 may alternatively be formed in the lower surface 120b of the first plate portion 150, or within the first plate portion 150 (for example, between the top surface 120a and the bottom surface 120b). The first plate portion 150 may comprise any suitable number of venting channels 170 (for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 etc.). The venting channels 170 in the first plate portion 150 are arranged such that in a battery pack 100 comprising multiple modules 105, the venting channels 170 formed in the busbars of adjacent modules 105 are configured to align with one another to provide a continuous fluid pathway across multiple modules 105 of the battery pack 100 to enable exhaustion of the hot gas from a failed cell 140 to an external space outside the battery pack 100, as shown in Figure 1. However, that is not essential. For example, the venting channels 170 may have sufficient volume to accommodate the emitted material from a failed cell 140 without requiring the emitted material to be exhausted from the battery back 100. Alternatively, the venting channels 170 formed in the busbars of adjacent modules 105 may each provide a separate fluid pathway to a separate vent in the battery pack 100, and may not require coordination between venting channels 170 of busbars of adjacent modules 105 to allow exhaustion of material from the battery pack 100.

[0062] The venting channels 170 on the top surface 120a are in fluid communication with the vents 146 of the cells 140 via a plurality of apertures 172 formed in the bottom surface 120b. The extent to which the apertures 172 extend through the thickness of the first plate portion 150 may depend on the location of the venting channels 170 (for example, whether the venting channels 170 are formed in the top surface 120a, the bottom surface 120b or between the top and bottom surfaces 120a, 120b of the first plate portion 150. It will be appreciated the first plate portion 150 may not comprise apertures if the venting channels 170 are formed in the bottom surface 120b. The apertures 172 are arranged such that they substantially align with the vents 46 of the respective cells 140 to provide a fluid pathway between the vent 146 of the cell 140 and the venting channels 170. In the embodiment shown, the apertures 172 each have a substantially circular cross-section, although that is not essential and the apertures 172 may have any suitable shape or configuration.

[0063] The apertures 172 each have a cross-sectional area that is equal to or larger than the cross-sectional area of the vents 146 of the cells 140. The venting channels 170 have a larger cross-sectional area than the apertures 172. The increase in cross-sectional area of the fluid pathway from the vents 146 through the apertures 172 and into the venting channels 170 may allow the hot gas emitted from the failed cell 140 to expand (and therefore cool) as it is exhausted from the module 105, although that is not essential.

[0064] The first plate portion 150 also comprises a plurality of recessed portions 175. The recessed portions 175 are formed in the bottom surface 120b of the first plate portion 120 facing or adjacent the cells 140. The recessed portions 175 are substantially circular, although that is not essential and the recessed portions 175 may have any suitable shape. The recessed portions 175 each substantially align with a respective cell 140 such that each recessed portion 175 is substantially opposite an end of the cell 140, although that is not essential. When a cell 140 fails due to thermal runaway, hot gas emitted from the vents 146 of the cell 140 is directed towards and into the recessed portion 175. The recessed portion 175 may provide a larger surface area of the first plate portion 150 (for example, compared to a flat surface) for the hot gas to contact as it is vented from the cell 140, which may enable rapid local heat transfer from the gas soon after emission, quickly cooling the gas. Providing recessed portions 175 in the first plate portion 150 may also enable the cross-sectional area of the first plate portion 175 to be increased whilst reducing or minimising a mass of the first plate portion 150. The cross-sectional area of the first plate portion 150 determines its electrical and thermal conductivity. A thicker busbar may reduce both electrical and thermal losses, and allow the busbar to be used to cool the cells (for example, via conduction to a cooler surface such as an outer surface of the module 105 or battery pack 100). The greater the mass of material present in the busbar, the more heat energy the busbar can absorb for a given temperature rise (the busbar provides a greater thermal mass for heat absorption). During thermal runaway or failure of a cell 140 it may be critical to ensure the adjacent cells 140 are not exposed to temperatures which may induce thermal runaway (which may propagate cell failure across the module 105). Providing a busbar in the form of a first plate portion 150 may therefore provide a sufficient thermal mass for heat absorption adjacent a failed cell 140 to maintain a low temperature locally. Providing recessed portions 175 in the first plate portion 150 may simultaneously provide a greater surface area for rapid local heat transfer from the gas into the first plate portion 150 to locally reduce a temperature of the emitted gas quickly. In the embodiment shown, the apertures 172 are provided in the recessed portions 175, although that is not essential. It will also be appreciated the first plate portion 150 may not comprise recessed portions.

[0065] The first plate portion 150 also comprises connection apertures 178. The connection apertures 178 are configured to receive a bolt or other fastener (not shown) to secure the first plate portion 150 to the sheet 160 and the jig 165. Alternatively, those components may be secured to one another using alternative means (for example, adhesive, heat staking). That may allow the connection apertures 178 to receive a fastener to secure the first plate portion 150 to a second plate portion 155 located at an opposing end of the cells 140 (for example, the fastener may pass through substantially a whole thickness of the module 105). The terminal 110 of the first plate portion 150 comprises a threaded aperture 112. The threaded aperture 112 allows connection of an isolated electrical connection between two strings 108, the connection of a master service disconnect, or a connection to a load external of the battery pack 100. It is not essential the terminal 110 comprises a threaded aperture.

[0066] The first plate portion 150 further comprises a cooling channel 180. The cooling channel 180 is configured to direct a flow of coolant across the first plate portion 150 to provide active cooling of the module 105. In the embodiment shown, the cooling channel 180 is provided in the top surface 120a of the first plate portion 150, although that is not essential. The cooling channels 180 are arranged or located such that in a battery pack 100 comprising multiple modules 105, the cooling channels 180 formed in the busbars of adjacent modules 105 are configured to align with one another to provide a continuous pathway across multiple modules 105 of the battery pack 100 to enable coolant flow throughout the battery pack 100 across multiple modules 105, as shown in Figure 1.

[0067] The cooling channel 180 intersects with the venting channels 170. The cooling channel 180 has a smaller depth than the venting channels 170. That may allow a pipe or tube (not shown) containing coolant to be placed into the cooling channel 180 without obstructing the venting channels 170. The venting channels 170 may effectively pass under the cooling channel 180 to allow exhaustion of vented gas to an external space. The intersection of the cooling channel 180 with the venting channels 170 may also enable the coolant to provide additional direct cooling to the vented gas from any failed cell 140. However, that is not essential and the cooling channel 180 may be provided spatially separately from the venting channels 170. It will also be appreciated the first plate portion 150 may be provided without a cooling channel.

[0068] Figure 5 shows a cross-sectional view of the first plate portion 150 in situ connected to the cells 140. A one-way valve mechanism 185 is provided in the recessed portion 175. In the embodiment shown, the one-way valve 185 comprises a sheet or plate of material 185a housed in the recessed portion 175. The recessed portion 175 comprises an opening 175a formed in the bottom surface 120b of the first plate portion 150, and a lip, shelf or shoulder 175b set back from the opening 175a. The lip 175b increases a width of the recessed portion 175 compared to a width of the opening 175a. The lip 175b provides a surface for the plate 185a to rest against, the plate 185a having a greater width or diameter than that of the opening 175a but not spanning a full width or diameter of the recessed portion 175 beyond the lip 175b (to leave space for emitted gas to reach the apertures 172 and the venting channels 170.

[0069] When a cell 140 fails due to thermal runaway, hot gas emitted from the vents 146 of the cell 140 is directed towards and into the recessed portion 175. The flow F of hot gas from the failed cell 140 acts to urge the plate 185a within the recessed portion 175 “up” or away from the opening 175a and against an innermost surface of the recessed portion 175. The plate 185a has a width or diameter such that the plate 185a does not obstruct the apertures 172 formed in the recessed portion 175 when the plate 185a is forced upwards by the flow F, allowing the hot gas to reach the venting channels 170. However, if the hot gas flows through the venting channels 170 and into apertures 172 aligned with an adjacent cell 140, the flow F acts to urge the plate 185a “down” or towards the opening 175a of the adjacent recessed portion 175. The plate 185a therefore effectively seals the opening 175a and protects the adjacent cell 140 from exposure to hot gas emitted from the failed cell 140. The plate 185a may be made from or comprise an intumescent material. An intumescent material may absorb heat from the hot gas resulting in swelling and charring. The activated intumescent material may then provide a thermal barrier reducing heat transfer to the adjacent cells 140. The swelling of the intumescent material of the plate 185a may not inhibit the flow F away from the failed cell 140, but may help to seal the opening 175a aligned with adjacent cells 140 to protect those adjacent cells from the flow F. The plate 185a may alternatively comprise any suitable material, for example aluminium, copper to absorb heat from the flow F of hot gas. However, it will be appreciated any suitable one-way valve mechanism may alternatively be provided in the fluid pathway between each cell 140 and the venting channels 170 to provide a similar function. Alternatively, the first plate portion 150 may not comprise a one-way valve mechanism.

[0070] The first plate portion 150 may alternatively comprise an intumescent material that does not form part of a one-way valve mechanism. For example, a portion of intumescent material may be provided in a fixed position within the recessed portion 175, or at any suitable location along a fluid pathway between the vent of a cell 140 and the venting channels 170, or within the venting channels 170 themselves. Figures 6A and 6B show another embodiment of a first plate portion 250. The first plate portion 250 is substantially similar to the first plate portion 150 described with respect to Figures 1 to 5, with like reference numerals indicating like elements.

[0071] The apertures 272 are substantially arc-shaped and are disposed along a circumference or perimeter of the recessed portion 275. The recessed portion 275 comprises a first lip or shoulder 275b used to locate the plate 285a. The plate 285a seats against the first lip 275b to prevent a flow F of hot gas from a different failed cell 140 (not shown) from reaching the cell 140 located beneath the plate 285a. The recessed portion 275 further comprises a second lip or shoulder 275c which increases the width or diameter of the recessed portion 275 to allow a flow F of vented gas to flow past the plate 285a to reach the apertures 272 should the cell 140 (not shown) located beneath the plate 285a fail. In the embodiment shown, the opening 275a of the recessed portion 275 is tapered. That may act to guide a flow F of hot gas from a failed cell 140 into the recessed portion 275 without the flow F being restricted (for example, due to encountering a stepped, sharp perpendicular edge at of the recessed portion 275 that would be present without a tapered opening 275a). However, that is not essential. The first plate portion 250 also comprises a voltage tap location 290, although that is not essential.

[0072] Returning to Figure 2 (and shown in isolation in Figure 7), each electrically conductive plate comprises a first plate portion 150 electrically connected (or connectable) to the positive terminals of the cells 140. The electrically conductive plates also each comprise a second plate portion 155 electrically connected (or connectable) to the negative terminals of each cell 140. The second plate portion 155 is also directly coupled to the negative terminals of each cell 140, to provide direct electrical and thermal conduction between the second plate portion 155 and the negative terminals of each cell 140.

[0073] Returning to Figure 3, the internal chemistry of a typical cylindrical cell 140 is arranged such that thermal conductivity in an axial or longitudinal direction is significantly greater than in a radial direction (for example, up to 100 times greater). In addition, an air gap is typically provided beneath the positive terminal 144 located at one end of the cell 140, providing thermal insulation. As such, the opposing axial end of the cylindrical cell 140 is typically where the greatest amount of heat can be removed from the cell 140 most rapidly. The second plate portion 155 of the plate or busbar comprises a greater mass than the first plate portion 150. A greater mass of material adjacent the axial end of the negative terminal of the cell 140 enables a greater amount of heat to be removed from the cell 140 at that location than from other parts of the cell 140. That heat removal may also be achieved more rapidly by making use of the increased thermal conductivity of the cell 140 in an axial direction. Directly coupling the second plate portion 155 to the cells 140 further improves cooling of the cells 140.

[0074] In the embodiment shown, as described above with respect to Figure 2, each busbar or electrically conductive plate comprises a contoured outer perimeter that substantially mirrors an external perimeter of the array of cells 140 in the module 105. The surface area of the second plate portion 155 is therefore substantially fixed. A mass of the second plate portion 155 is increased relative to the mass of the first plate portion 150 by maintaining a full thickness of the second plate portion 155 across a greater portion of the surface, rather than removing material, for example to provide venting channels and / or cooling channels 170. However, it will be appreciated the second plate portion 155 may also comprise cooling channels (for example, similar to cooling channels 180 of the first plate portion 155) and still have a greater mass than the first plate portion 150.

[0075] The greater mass of the second plate portion 155 may also provide mechanical reinforcement to the cells 140 adjacent that axial end. That may reduce a likelihood of the cell 140 rupturing or failing at the negative terminal end. In turn, that increases the likelihood that any failure of the cell 140 takes place at the positive terminal, adjacent a first plate portion 150 comprising features intended to manage the emission of hot gas from cell 140 that has failed due to thermal runaway. The first plate portion 150 and the second plate portion 155 disposed at opposing ends or sides of each module 105 may therefore work in conjunction with one another to both mitigate the risk of thermal runaway, and manage cell failure events to prevent thermal runaway propagation throughout the module 105.

[0076] The second plate portion 155 also comprises a plurality of structures 195 to retain the cells 140 in a desired position relative to the second plate portion 155. In the embodiment shown, the structures 195 each comprise a raised area that at least partially surrounds an outer surface of one or more cells 140 (for example, the outer cylindrical surface of the cells 140). The raised areas 195 are positioned in the spaces provided between the cells 140 in the array. The raised areas 195 may also provide further mechanical reinforcement to the cells 140 adjacent that axial end of the cells 140. In the embodiment shown, each raised area 195 comprises a substantially triangular shape having concave or curved sides to more closely engage the outer surface of the cells 140. However, the structures 195 may have any suitable shape or configuration, for example a substantial ring or arc shape that at least partially surrounds an end of the cells 140.

[0077] From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art of electrical batteries, and which may be used instead of, or in addition to, features already described herein.

[0078] Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.

[0079] Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. The applicant hereby gives notice that new claims may be formulated to such features and / or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

[0080] For the sake of completeness, it is also stated that the term “comprising” does not exclude other elements or steps, the term “a” or “an” does not exclude a plurality, and any reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

CLAIMS1. An electrically conductive plate configured to electrically connect to each of a first plurality of electrical cells, the plate comprising: a venting channel formed in the plate; wherein the venting channel is arranged such that when the plate is connected to the cells in use, the venting channel is configured to be in fluid communication with a vent of each of cell to provide a fluid pathway between the vent of each cell and a space external to the cells.

2. The plate of claim 1, wherein the plate further comprises: a plurality of apertures extending at least partially through a thickness of the plate; wherein the apertures are arranged or located such that when the plate is connected to the cells in use, each aperture is configured to provide a fluid pathway between the vent of a respective cell and the venting channel.

3. The plate of claim 2, wherein the venting channel has a larger cross-sectional area than each of the apertures.

4. The plate of claim 2 or of claim 3, wherein each of the apertures and the venting channel have a cross-sectional area equal to or larger than a cross-sectional area of the vent of each cell to which the plate is connected in use.

5. The plate of any of claims 2 to 4, wherein: a first surface of the plate is adjacent the cells when the plate is connected to the cells in use, and the venting channel is formed in an opposing second surface of the plate.

6. The plate of any preceding claim, wherein the plate further comprises: a plurality of recessed portions formed in a surface of the plate which is adjacent the cells when the plate is connected to the cells in use; and optionally wherein the recessed portions are arranged such that when the plate is connected to the cells in use, each recessed portion is configured to substantially align with a respective cell.

7. The plate of claim 6 dependent from any of claims 2 to 5, wherein each of the apertures is located in a respective recessed portion.

8. The plate of claim 6 or of claim 7, wherein each recessed portion has a substantially similar cross-sectional area to the cell with which it is substantially aligned.

9. The plate of any preceding claim, wherein the plate further comprises: a plurality of one-way valves; wherein the one-way valves are arranged such that when the plate is connected to the cells in use, each one-way valve is disposed in a fluid pathway between the vent of a respective cell and the venting channel.

10. The plate of claim 9 dependent from any of claims 6 to 8, wherein each of the one-way valves is disposed within a respective recessed portion.

11. The plate of any preceding claim, wherein the plate further comprises: a plurality of intumescent portions; and optionally wherein the intumescent portions are arranged such that when the plate is connected to the cells in use, each intumescent portion is disposed in a fluid pathway between the vent of a respective cell and the venting channel.

12. The plate of claim 11 dependent from any of claims 6 to 8, wherein each of the intumescent portions is disposed within a respective recessed portion.

13. The plate of claim 11 or claim 12 dependent from claim 9 or claim 10, wherein each of the intumescent portions forms a part of a respective one-way valve.

14. The plate of any preceding claim, wherein the plate further comprises: a cooling channel configured to direct a flow of coolant across the plate.

15. The plate of claim 14, wherein the cooling channel and the venting channel intersect one another.

16. The plate of any preceding claim, wherein the plate comprises: a first plate portion in which the venting channel is formed; wherein the first plate portion is configured to electrically connect to a positive terminal of each of the first plurality of cells; and a second plate portion; wherein the second plate portion is configured to electrically to a negative terminal of each of a second plurality of cells; and wherein the second plate portion comprises a greater mass than the first plate portion.

17. The plate of claim 16, wherein the second plate portion comprises one or more structures configured to retain each of the second plurality of cells in a desired position relative to the second plate portion.

18. The plate of claim 16 or of claim 17, wherein the second plate portion is configured to structurally support each of the second plurality of cells adjacent the second terminals of the second plurality of cells, and optionally wherein the second plate comprises one or more structures configured to at least partially surround an end of each of the second plurality of cells.

19. A battery comprising: a plurality of electrical cells, each cell comprising a vent; and the plate of any preceding claim electrically connected to the cells.

20. A battery comprising: a plurality of cylindrical cells; a first electrically conductive plate electrically connected to a positive terminal of each cell; and a second electrically conductive plate electrically connected to a negative terminal of each cell; wherein the second plate comprises a greater mass than the first plate.

21. The battery of claim 20, wherein the second electrically conductive plate is directly coupled to the negative terminal of each cell.

22. The battery of claim 20 or of claim 21, wherein the second plate: i) comprises one or more structures configured to retain each cell in a desired position relative to the second plate; and / or ii) is configured to structurally support each of the cells adjacent the negative terminals of the cells, and optionally wherein the second plated comprises one or more structures configured to at least partially surround an end of each of the cells.

23. The battery of any of claims 20 to 22, wherein the first electrically conductive plate comprises the electrically conductive plate of any of claims 1 to 18.

24. An electrically conductive plate configured to electrically connect to each of a plurality of cells, comprising: a first plate portion configured to electrically connect to a positive terminal of each of a first subset of the plurality of cells; and a second plate portion configured to electrically connect to a negative terminal of each of a second subset of the plurality of cells; wherein the second plate portion comprises a greater mass than the first plate portion.

25. The plate of claim 24, wherein the second plate portion: i) comprises one or more structures configured to retain each cell of the second subset in a desired position relative to the second plate portion; and / or ii) is configured to structurally support each cell of the second subset adjacent the negative terminals of the cells, and optionally wherein the second plate portion comprises one or more structures configured to at least partially surround an end of each cell of the second subset.

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