GB2621973A - Busbar for a battery - Google Patents

Abstract

A busbar 102 for a battery 100 which comprises a plurality of cells 104 arranged side-by-side, the busbar 102 comprising a support layer 112 formed of an insulating material which has a Young’s Modulus of at least 10 GPa, a thickness of 1 mm or less and is configured to support a first end of the plurality of cells 104. The busbar 102 further comprises a plurality of conductive traces 118 disposed on the support layer 112, the plurality of conductive traces 118 comprising contact portions for contacting terminals located at the first end of the plurality of cells 104. The conductive traces 118 can be formed from a single sheet of a conductive material which is adhered to the support layer 112. The insulating material can be a fibre-reinforced composite. A plurality of apertures 114 can be formed in the support layer 112 which in use expose terminals at the first end of the cells 104 with the contact portions extending over the apertures 114. When assembled as part of a vehicle battery, each contact portion can be welded to a respective cell terminal.

Description

BUSBAR FORA BATTERY

FIELD OF THE INVENTION

The present invention relates to a busbar for a battery comprising a plurality of battery cells arranged side-by-side. The invention also relates to a battery comprising the busbar, the battery being particularly suited to use in an electric vehicle.

BACKGROUND

An electric vehicle is a vehicle that uses an electric motor for propulsion, with the electric motor being powered by one or more batteries in the vehicle. Some electric vehicles, known as hybrid electric vehicles, combine a conventional internal combustion engine with an electric motor. Typically, the batteries used for powering electric vehicles are rechargeable lithium-ion batteries, although other types of battery can also be used. In contrast to an internal combustion engine, operation of the electric motor in an electric vehicle does not produce any tailpipe emissions. Because of this, electric vehicles are promoted as a means for reducing greenhouse gas emissions caused by transportation. In particular, where renewable energy is used for recharging electric vehicle batteries, significant reductions in greenhouse gas emissions associated with transportation may be achieved.

Typically, an electric vehicle battery includes a plurality of battery cells, such as lithium-ion battery cells, which are electrically connected together to provide a required voltage and current output. The electrical connections between the battery cells are implemented using electrical connectors (e.g. busbars) connected to terminals located at ends of the battery cells, with insulating boards being used to isolate different parts of the battery from one another. The battery further includes a frame (or housing) arranged at the ends of the battery cells which provides a rigid structure that holds the battery cells in place. The frame may comprise heavy-duty materials such as layers of plastic and/or metal in order to withstand acceleration forces that the battery cells may experience during use of the vehicle, which may be particularly large for example in case of a collision. For example, in order to pass the United Nations Economic Commission for Europe (UN ECE) Regulation R100 v2, the frame must be capable of withstanding accelerations of up to 28 g on the battery cells. To pass UN 38.3, which is another battery approval standard, the battery must be able to withstand shocks up to 50 g. As a result of these requirements, the electrical connections and frame may result in a bulky and heavy battery structure.

SUMMARY OF THE INVENTION

At its most general, the present invention provides a busbar for a battery having a plurality of battery cells, wherein the busbar is configured to fulfil the dual functions of electrically connecting the battery cells together and providing a rigid structure for holding the battery cells in place. This is achieved by forming the busbar of a thin rigid layer of insulating material, on which a plurality of conductive traces is disposed. Thus, with the busbar of the invention, it is not necessary to provide separate structures for electrically connecting the battery cells together and for supporting the battery cells, as the busbar can perform both these functions. This may contribute to simplifying a construction of the battery. This may also serve to make the battery lighter and more compact, thus increasing the battery's energy density. In particular, the thickness of the busbar of the invention may be less than the combined thicknesses of the frame and the electrical connectors used in the prior art, resulting in a reduced dimension (e.g. height or width) of the battery. Increasing the battery's energy density may be particularly advantageous where the battery is used to power an electric vehicle, in view of the limited amount of space which may be available in the electric vehicle for accommodating the battery. Moreover, this may contribute to increasing a driving range of the electric vehicle.

According to a first aspect of the invention, there is provided a busbar for a battery comprising a plurality of battery cells arranged side-by-side, the busbar comprising: a support layer formed of an insulating material, wherein a Young's modulus of the support layer is equal to or greater than 10 GPa and a thickness of the support layer is equal to or less than 1 mm, the support layer being configured to support a first end of the plurality of battery cells; and a plurality of conductive traces disposed on the support layer, the plurality of conductive traces comprising contact portions for contacting terminals located at the first end of the plurality of battery cells.

Thus, the busbar is configured to be positioned at the first end of the plurality of battery cells, e.g. with the support layer abutting (contacting) the first end of the plurality of battery cells. In this manner, the support layer of the busbar may act to resist movement of the battery cells in a direction normal to the support layer. The plurality of conductive traces can then be used to connect the plurality of battery cells together, e.g. by connecting the contact portions to terminals located at the first end of the battery cells.

The support layer may be formed of any suitable electrically insulating (i.e. dielectric) material. In this manner, the support layer may act to support the plurality of conductive traces, and isolate the conductive traces from one another. This may avoid any short-circuits arising when the conductive traces are connected to the plurality of battery cells.

The Young's modulus of the support layer is equal to or greater than 10 GPa. Young's modulus may also be referred to as tensile modulus or elastic modulus. As is known in the art, the Young's modulus of a material is a mechanical property of that material that represents the material's elasticity, i.e. its resistance to deformations in response of the application of a force to that material. In the linear elastic region of the material, Young's modulus is defined as stress divided by strain.

In some materials, Young's modulus may be isotropic, i.e. it is the same for all directions in the material. However, other materials may have different mechanical properties along different directions, resulting in an anisotropic Young's modulus (i.e. where Young's modulus depends on a direction of the force applied to the material). In the case of the busbar of the invention, the busbar serves to resist motions of the battery cells in a direction normal to the support layer. Thus, the Young's modulus of the support layer may be equal to or greater than 10 GPa in a direction parallel to the support layer. In other words, regardless of whether an isotropic or anisotropic material is used for the support layer, the support layer's Young's modulus may be equal to or greater than 10 GPa in a direction normal to the support layer. Preferably, the support layer's Young's modulus may be greater than 10 GPa in all directions.

The material of the support layer may thus be selected to ensure that it has a Young's modulus falling within the claimed range. Any suitable stiff insulating material may be used, such as plastics and composite materials. Various examples of suitable materials for the support layer are provided below.

The thickness of the support layer is equal to or less than 1 mm (e.g. 1.0 mm). For example, the thickness of the support layer may be between 0.2 mm and 1.0 mm (including these values). In this manner, the support layer may have a minimal thickness, resulting in a thin busbar, e.g. with a thickness around 1.6 mm or less. Thus, when the busbar is integrated into a battery, the busbar may only contribute a small portion to a length (e.g. height or width) of the battery. For example, typical battery cells used in electric vehicle applications may have a length of 65 mm. So, if the busbar has a thickness of 1.6 mm or less, the busbar may at most represent 2.4% of a total length of the battery. This enables an energy density of the battery to be increased, e.g. compared to batteries which use thicker electrical connectors and/or support frames at the ends of the battery cells.

The thickness of the support layer may refer to a thickness in a direction normal to the support layer, e.g. normal to a plane defined by a surface of the support layer.

The inventors have found that providing the support layer with a Young's modulus equal to or greater than 10 GPa and a thickness equal to or less than 1 mm may ensure that the support layer has sufficient rigidity to resist acceleration forces that may be experienced by the battery cells, e.g. when the battery is used in a vehicle. For example, the inventors have found that when the support layer has a thickness in the range of 0.2 mm to 1 mm, a Young's modulus equal to or greater than 10 GPa may ensure sufficient rigidity of the support layer for resisting the acceleration forces. Thus, when the busbar is mounted at the first end of the plurality of battery cells, the busbar may act to support the plurality of battery cells and maintain them in place, by resisting motion of the battery cells in a direction normal to the support layer. Additionally, the support layer may act to absorb shocks experienced by the battery, which may reduce stresses experienced by the plurality of conductive traces and connections between the contact portions and the terminals on the battery cells. Accordingly an integrity and reliability of electrical connections between the plurality of battery cells may be improved.

Additionally, the inventors have found that using a support layer with the claimed properties may facilitate assembly of the battery. In particular, assembly of the battery may involve a step of compressing the battery during curing of adhesives which are used to hold the battery together. During compression of the battery, the support layer of the busbar may serve to transmit the compression force to battery cells whilst substantially keeping its shape. This may ensure that the support layer is not significantly deformed during the compression, so that the battery cells experience a substantially equal compression force and are maintained in a correct position whilst the adhesive is cured.

The plurality of conductive traces is disposed on the support layer. The support layer may comprise a first surface which is configured to face towards the first end of the plurality of battery cells, and a second, opposite surface which is configured to face away from the first end of the plurality of battery cells. The plurality of conductive traces may be disposed on the second surface. Therefore, when the busbar is mounted at the first end of the plurality of battery cells, the plurality of conductive traces may be on an opposite side of the support layer compared to the plurality of battery cells. In this manner, the support layer may act to isolate the plurality of conductive traces from the plurality of battery cells. The first surface of the support layer may be arranged to abut (e.g. contact) the first end of the plurality of battery cells, such that the support layer can hold the plurality of battery cells in place.

The plurality of conductive traces may be configured to connect the plurality of battery cells in series and/or parallel, in order to provide a required output current and voltage. Thus, when the contact portions of the conductive traces are connected to the plurality of battery cells, the battery cells may be connected in series and/or parallel. In other words, the plurality of conductive traces may define a series of conductive paths which connect the plurality of battery cells in series and/or parallel when the contact portions are connected to the terminals on the plurality of battery cells.

The plurality of conductive traces may be formed of a conductive material (e.g. metal) which is deposited on and/or bonded to the support layer.

The contact portions of the conductive traces may be adapted (e.g. shaped, positioned) for connection to the terminals at the first end of the plurality of battery cells. More generally, the plurality of conductive traces may be specifically adapted (e.g. shaped, positioned) to the arrangement of the plurality of battery cells, to enable effective connection of the contact portions to the terminals at the first end of the plurality of battery cells. For example, the contact portions may be arranged to match a spatial arrangement of the terminals of the plurality of battery cells.

The contact portions may be arranged to contact the terminals at the first end of the plurality of battery cells through the support layer. For example, as discussed in more detail below, apertures may be formed in the support layer to enable the contact portions to be connected to the terminals at the first end of the plurality of battery cells.

The contact portions may be connectable to the terminals at the first end of the plurality of battery cells using any suitable means, such as welding, soldering or other electrical connection methods.

The battery with which the busbar of the invention can be used may be any suitable battery having a plurality of battery cells arranged side-by-side. The battery cells in the battery may be of any suitable type, such as lithium-ion battery cells or other known types of battery cells.

Each battery cell in the plurality of battery cells may have a pair of terminals (e.g. a positive terminal and a negative terminal) which is accessible (e.g. positioned, located) at the first end of the battery cell. The battery cells in the plurality of battery cells may all be of a same type, e.g. they may all have a same voltage, shape and terminal arrangement.

Preferably, each battery cell in the plurality of battery cells may be a cylindrical battery cell The plurality of battery cells being arranged side-by-side may mean that the battery cells are adjacent to one another, and that ends of the battery cells are aligned (i.e. level) with one another. In particular, the first ends of the battery cells may be aligned (i.e. level) with one another, such that that the first ends of the plurality of battery cells are arranged substantially in a same plane. In this manner, the support layer of the busbar can abut the first end of each battery cell in the plurality of battery cell.

The battery cells may be arranged in a regular array, such as in a grid pattern, or in any other suitable arrangement. The battery cells may be in an arrangement which maximises packing efficiency. For example, where cylindrical battery cells are used, the battery cells may be in a closest packing arrangement.

The insulating material may comprise a composite material. Composite materials may have a high degree of rigidity whilst being relatively lightweight. Thus, a thin layer of composite material can provide a support layer with good rigidity for resisting motion of the plurality of battery cells in the direction normal to the support layer, without adding much weight to the battery. Advantageously, using a composite material for the support layer may enable the support layer to be formed of a single continuous layer of material, which may improve a rigidity and integrity of the support layer. In contrast to plastic materials formed by injection moulding and/or 3D printing, much thinner layers of composite materials can be used whilst still achieving high levels of rigidity for the support layer.

Herein a composite material may refer to a material comprising at least two components. For example, a composite material may comprise a matrix material (e.g. a binder) and a reinforcing material.

The composite material may comprise a fibre-reinforced polymer material. The inventors have found that fibre-reinforced polymer materials are particularly suited to use as the support layer, as they can provide high levels of rigidity with a relatively small thickness. The fibre-reinforced polymer material may comprise a polymer matrix that is reinforced with fibres. Examples of suitable fibres include aramid fibres and glass fibres. Preferably, the fibres do not include carbon fibres, as these are conductive and so would risk causing shorts between the conductive traces.

As a specific example, the composite material may comprise FR-4 fibreglass (FR-4 being a National Electrical Manufacturers Association (NEMA) designation of glass fibre-reinforced polymer materials.

A plurality of apertures may be formed in the support layer for exposing terminals at the first end of the plurality of battery cells, with the contact portions extending over the apertures.

In this manner, the contact portions can be connected to the terminals at the first end of the plurality of battery cells via the apertures in the support layer. As the contact portions extend over the apertures, when the support layer is arranged at the first end of the plurality of battery cells, the contact portions may be disposed over the terminals of the battery cells, thus facilitating connection of the contact portions to the terminals of the battery cells. For example, the contact portions can be welded, soldered or otherwise electrically connected to the terminals of the battery cells.

The plurality of apertures may be arranged in a regular pattern or array. In particular, the plurality of apertures may be arranged in a pattern that matches an arrangement of the plurality of battery cells, so that the apertures can expose the terminals at the first end of the plurality of battery cells when the support layer is disposed at the first end of the plurality of battery cells Each aperture in the plurality of apertures may have a shape that is adapted to expose the terminals at the first end of one of the battery cells.

The support layer may comprise, for each aperture in the plurality of apertures, one or more support elements at an edge of the aperture for engaging the first end of one of the plurality of battery cells. In this manner, the support elements may abut the first end of the plurality of battery cells, in order to support the battery cells and maintain the battery cells in place. In other words, the support elements may act as points of contact between the support layer and the plurality of battery cells. The support elements may further serve to locate the first end of each battery cell with respect to an associated one of the plurality of apertures, to ensure proper alignment between the busbar and the plurality of battery cells.

Each support element may be in the form of a protrusion that extends from an edge of one of the apertures towards an inside (e.g. centre) of the aperture. For example, the support elements may be in the form of tabs extending from edges of the apertures, which are arranged to contact the first end of the plurality of battery cells when the support layer is arranged at the first end of the plurality of battery cells.

The plurality of conductive traces may comprise a plurality of substantially parallel conductive strips, and the contact portions may extend laterally from the conductive strips. Thus, the conductive strips may extend along the support layer in a first direction, and the contact portions may extend from the conductive strips in a second direction, the second direction intersecting the first direction. Such a structure of the conductive traces may enable efficient electrical connection of the plurality of battery cells. This may also facilitate construction of the plurality of conductive traces, as such a shape of the conductive traces may facilitate cutting the conductive traces from a sheet of conductive material.

Where the support layer comprises a plurality of apertures, the plurality of apertures may be arranged in parallel rows. The conductive strips may then be positioned between the rows of apertures, with the contact portions extending laterally from the conductive strips so that they extend over the apertures.

The contact portions of the plurality of conductive traces may comprise a first set of contact portions arranged to contact positive terminals at the first end of the plurality of battery cells, and a second set of contact portions arranged to contact negative terminals at the first end of the plurality of battery cells. Where the plurality of conductive traces comprise a plurality of substantially parallel conductive strips, the first set of contact portions may extend laterally from a first side of the conductive strips, and the second set of contact portions may extend laterally from a second (opposite) side of the conductive strips. This may enable battery cells in adjacent rows to be connected in series, whilst connecting battery cells within a same row in parallel.

The support layer may be arranged to cover parts of the negative terminals at the first end of the plurality of battery cells. In this manner, the support layer may isolate the first set of contact portions from the negative terminals. For example, each contact portion in the first set of contact portions may be configured to extend over a respective part of the support layer which is arranged to cover part of the negative terminal at the first end of a respective one of the plurality of battery cells. In some cases, the support elements mentioned above may be arranged to cover parts of the negative terminals at the first ends of the plurality of battery cells, and so may act to isolate the first set of contact portions from the negative terminals.

The plurality of conductive traces may be bonded to the support layer with an adhesive. This may ensure effective bonding between the support layer and the conductive traces, whilst minimising a thickness of the busbar. In particular, this may avoid having to use bulky fasteners such as bolts or clamps, which might increase a thickness of the busbar. This may also facilitate fabrication of the busbar, as the plurality of conductive traces can be formed separately from the busbar (e.g. by cutting out the conductive traces from a conductive sheet) and then applying them to the busbar. Any suitable type of adhesive may be used for bonding the plurality of conductive traces to the busbar. As an example, the adhesive may be an epoxy (e.g. two-part epoxy) or a spray contact adhesive. The adhesive may be a non-conducting adhesive, which may serve to isolate the conductive traces from the support layer. In a specific example, the adhesive may be a two-part methacrylate adhesive.

The Young's modulus of the support layer may be equal to or greater than 20 GPa. This may provide the support layer with enhanced rigidity, improving its ability to resist deformations and absorb shocks. As a result, a reliability of the electrical connections between the busbar and the plurality of battery cells, as well as an integrity of the battery, may be improved.

Materials such as those discussed above, e.g. composite materials, may be chosen to provide the support layer with a Young's modulus equal to or greater than 20 GPa. Other types of material having a Young's modulus equal to or greater than 20 GPa may also be used.

The thickness of the support layer may be between 0.2 mm and 0.8 rum. This may serve to further reduce a thickness of the busbar, to minimise its contribution to a size of the battery as well as reduce a weight of the battery. The inventors have found that, when the thickness of the support layer is in the range of 0.2 mm to 0.8 mm, it is possible to obtain a sufficiently rigid support layer by selecting a material for the support layer having its Young's modulus in the claimed range.

The plurality of conductive traces may have a thickness of 0.6 mm or less. This may serve to reduce a thickness of the busbar, to minimise its contribution to a size of the battery as well as reduce a weight of the battery. In some cases, the plurality of conductive traces may have a thickness of 0.5 mm or less, or even 0.4 mm or less.

Herein, the thickness of the plurality of conductive traces may refer to a thickness of the plurality of conductive traces in a direction normal to the support layer, e.g. normal to a plane defined by a surface of the support layer.

The thickness of the plurality of conductive traces may be at least 0.1 mm, e.g. the thickness of the plurality of conductive traces may be between 0.1 mm and 0.6 mm. This may serve to ensure that the conductive traces are capable of supporting required currents.

The plurality of conductive traces may be configured, for example, to support currents in a range of 0-100 A. This may ensure that the conductive plurality of conductive traces can support currents typically used with the battery. The plurality of conductive traces may heat up during use. The battery may therefore include a cooling system for removing heat from the plurality of conductive traces. For example, the cooling system may be configured to pass a fluid (e.g. air, nitrogen, oil) through the battery. The fluid can be cooled by passing it through a heat exchanger (e.g. radiator), or where air is used it can be vented to atmosphere.

The support layer may be formed of a continuous sheet of the insulating material. Using a continuous sheet of insulating material for the support layer may improve a rigidity and integrity of the support layer, thus improving its ability to support the plurality of battery cells. This may also facilitate manufacture of the busbar, as a single continuous sheet can easily be processed to form the support layer. For example, the sheet of insulating material can be cut using techniques such as laser cutting, waterjet cutting or router cutting, in order to form the plurality of apertures discussed above.

The sheet may be a sheet of a composite material, such as one of the composite materials mentioned above. The inventors have found that using a continuous sheet of composite material for the support layer, it is possible to make the support layer thinner than with polymer materials formed via moulding and/or 3D printing processes.

The plurality of conductive traces may be formed from a single sheet of conductive material. For example, the plurality of conductive traces may be cut from a same sheet of conductive material. This may facilitate manufacture of the busbar, and ensure that all of the conductive traces have a uniform thickness and material characteristics. This may also serve to ensure uniform conductivity across the plurality of conductive traces, thus ensuring a good electrical performance of the busbar. Furthermore, as discussed below in more detail, forming the plurality of conductive traces from a single sheet of conductive material may facilitate positioning of the plurality of conductive traces on the support layer. In particular, this may facilitate maintaining a desired alignment between the plurality of conductive traces, thus improving a quality of the busbar. In line with the above, the sheet of conductive material may have a thickness of less than 0.6 mm.

Other techniques may also be used for forming the plurality of conductive traces. For example, in some cases, the plurality of conductive traces can be formed using additive manufacturing techniques, such as laser sintering or metal deposition techniques. Such techniques may involve 3D printing, such as direct metal laser sintering. This may enable a thickness of the plurality of conductive traces to be reduced. As another example, the plurality of conductive traces may be formed using a metal casting process.

The plurality of conductive traces may include a first set of termination ends that extend beyond a boundary of the support layer. This may facilitate electrical connections between the plurality of conductive traces and other parts of the battery. For example, the first set of termination ends may be used for connection to a battery management system, and/or to another set of battery cells. In this manner, the plurality of battery cells may be connected, via the plurality of conductive traces on the busbar, to a battery management system, and/or to another set of battery cells.

The first set of termination ends may comprise an end of each of the plurality of conductive traces which extends beyond the boundary (i.e. an edge) of the support layer. For example, where the plurality of conductive traces includes a plurality of substantially parallel conductive strips as discussed above, the first set of termination ends may correspond to ends of the conductive strips which extend beyond the boundary of the support layer. Additionally or alternatively, the first set of termination ends may correspond to side portions of one or more conductive strips located adjacent to the boundary of the support layer and which extend beyond the boundary of the support layer. For example, part of a width of a conductive strip may overhang the edge of the support layer to form a termination end.

The plurality of conductive traces may comprise a second set of termination ends that lies within a boundary of the support layer. This may serve to provide clearance between the plurality of conductive traces and other parts of the battery. Thus, the support layer may act as a buffer between the second set of termination ends and other parts of the battery, which may reduce a risk of short circuit to the second set of termination ends.

The first set of termination ends and the second set of termination ends may be located at opposite ends of the plurality of conductive traces. For example, the first set of termination ends may be located at a first end of the plurality of conductive strips, and the second set of termination ends may be located at a second end of the plurality of conductive strips.

The busbar of the first aspect of the invention may be incorporated into a battery. Thus, according to a second aspect of the invention, there is provided a battery comprising: a plurality of battery cells arranged side-by-side, each battery cell having a positive terminal and a negative terminal at a first end of the battery cell; a busbar according to the first aspect of the invention; wherein the busbar is arranged at the first end of the plurality of battery cells; and wherein the plurality of conductive traces is electrically connected to the plurality of battery cells via the contact portions, such that the plurality of conductive traces connects the plurality of battery cells in series and/or parallel.

Any of the features discussed above in relation to the first aspect of the invention may be shared with the second aspect of the invention. In particular, details discussed above relating to the battery cells and their arrangement may be shared with the second aspect of the invention.

With the busbar arranged at the first end of the plurality of battery cells, the busbar acts to support the plurality of battery cells and resist motion of the plurality of battery cells in a direction normal to the support layer. The support layer may abut the first end of the plurality of battery cells, as discussed above in relation to the first aspect.

The battery cells may be cylindrical battery cells, with a longitudinal axis of each battery cell arranged substantially normal to the support layer.

Each contact portion may be welded to a respective terminal on one of the plurality of battery cells. This may serve to ensure a reliable and effective electrical connection between each contact portion and a corresponding terminal on one of the battery cells.

The battery may form part of a battery system (or battery unit), where the battery system includes other components such as a battery management system. In some cases, the battery may correspond to a battery module in the battery system, where the battery system includes multiple battery modules that are electrically connected together (e.g. in series and/or parallel). In other words, the battery system may comprise multiple battery modules, where each battery module is a battery according to the second aspect of the invention.

According to a third aspect of the invention, there is provided an electric vehicle comprising a battery according to the second aspect of the invention. Any of the features discussed above in relation to the first and second aspects of the invention may be shared with the third aspect of the invention.

Herein, an electric vehicle may refer to a vehicle comprising an electrically powered drive system. In particular, the electric vehicle may comprise an electric motor, and the battery may be arranged to power the electric motor. In some cases the electric vehicle may include multiple electric motors, e.g. a first electric motor for driving the front wheels and a second electric motor for driving the rear wheels. In such a case, the battery may be arranged to power the multiple electric motors. The electric vehicle may be a hybrid electric vehicle, e.g. it may comprise an internal combustion engine and an electric motor which are arranged to power the vehicle.

The electric vehicle of the invention may be a road vehicle, e.g. a road car. In other words, the vehicle may be designed to be driven on roads. Accordingly, the vehicle of the invention may include any safety features as required by safety regulations for road vehicles. For example, the vehicle may include headlights, taillights, indicator lights, mirrors, airbags and other safety features. The vehicle may have a seat-belt (e.g. a three-point seat-belt) for securing an occupant in a seat of the vehicle.

Where the battery cells are cylindrical, the battery may be arranged in the vehicle such that a longitudinal direction of the plurality of battery cells is substantially parallel to a ground surface on which the vehicle is disposed. In other words, the longitudinal axis of the plurality of battery cells may be arranged substantially horizontally in the vehicle. Arranging the battery cells in this orientation may increase a number of battery cells which can be stacked vertically in the vehicle. In particular, this may increase a number of battery cells which can be arranged in the vehicle for a given amount of vertical space in the vehicle, as cylindrical battery cells have a smaller width than length. Accordingly, this orientation of the battery cells may serve to increase an energy capacity of the battery, thus increasing a travel range of the vehicle.

With the battery cells in this orientation, a thickness of the busbar is in the horizontal direction. Due to the thinness of the busbar, the busbar will not contribute significantly to a horizontal dimension (e.g. width) of the battery. As a result, a horizontal dimension of the battery and vehicle may be reduced, e.g. compared to vehicles using batteries with thicker busbars and/or support frames. Thus, the busbar of the invention, combined with a horizontal orientation of the battery cells may enable a horizontal dimension of the vehicle and battery to be minimised.

According to a fourth aspect of the invention, there is provided a method of manufacturing a busbar for a battery comprising a plurality of battery cells arranged side-by-side, the method comprising: forming a support layer from a sheet of insulating material, wherein a Young's modulus of the support layer is equal to or greater than 10 GPa and a thickness of the support layer is equal to or less than 1 mm, the support layer being configured to support a first end of the plurality of battery cells; forming a plurality of conductive traces from a sheet of conductive material, the plurality of conductive traces comprising contact portions for contacting terminals located at the first end of the plurality of battery cells; and securing the plurality of conductive traces to a surface of the support layer.

The method of the fourth aspect of the invention may be used for manufacturing the busbar of the first aspect of the invention. Accordingly, any features discussed above in relation to the first aspect of the invention may be shared with the fourth aspect of the invention. Forming the support layer may comprise cutting a plurality of apertures in the sheet of insulating material, the plurality of apertures being for exposing terminals at the first end of the plurality of battery cells, the plurality of conductive traces being arranged such that the contact portions extend over the apertures. Any suitable technique may be used for cutting the apertures, such as laser cutting, waterjet cutting or router cutting.

Forming the plurality of conductive traces may comprise cutting the sheet of conductive material to form the plurality of conductive traces. Any suitable technique may be used for cutting the sheet of conductive material, such as laser cutting, waterjet cutting or router cutting.

The sheet of conductive material may be cut such that the plurality of conductive traces are connected together via a connecting portion of the sheet of conductive material; and after securing the plurality of conductive traces to the surface of the support layer, the connecting portion may be disconnected from the plurality of conductive traces. Keeping the plurality of conductive traces connected together while securing the plurality of conductive traces to the support layer may facilitate positioning the plurality of conductive traces on the support layer, as the plurality of conductive traces may be handled as a single component. This may also ensure that correct alignment and relative positioning of the plurality of conductive traces is maintained while the plurality of conductive traces is secured to support layer. The connecting portion may correspond to part of the sheet of conductive material that is left in place during the cutting procedure. For example, the sheet of conductive material may be cut so as to leave a strip or tab of the sheet of conductive material that connects all of the plurality of conductive traces together. In some cases, the connecting portion may be a frame that connects the plurality of conductive traces together. Disconnecting the connecting portion from the plurality of conductive traces after securing the plurality of conductive traces to the support layer serves to ensure that the plurality of conductive traces are not shorted together. This may be achieved by cutting or breaking off the connecting portion from the plurality of conductive traces.

The method may further comprise introducing weak points at connections between the plurality of conductive traces and the connecting portion, the connecting portion being disconnected from the plurality of conductive traces at the weak points. This may facilitate disconnecting the connecting portion from the plurality of conductive traces, as the conductive material may be easily broken or cut at the weak points to remove the connecting portion. The weak points may also act to guide the disconnecting of the connecting portion from the plurality of conductive traces, which may avoid accidentally damaging the plurality of conductive traces during this procedure.

The weak points may be introduced using any suitable technique. For example, the weak points may be introduced by reducing a thickness of the conductive material at connection points between the plurality of conductive traces and the connecting portion. This may be achieved, for example, by chemical etching, scoring or any other method for removing conductive material from the connection points between the plurality of conductive traces and the connecting portion. As another example, the weak points may be introduced by stretching the conductive material at the connection points. Weak points may also be introduced by weakening the conductive material at the connection points, e.g. through fatigue induced by bending or impacting the conductive material at the connection points. The weak points may be introduced during or after the cutting of the sheet of conductive material to form the plurality conductive traces.

Securing the plurality of conductive traces to the surface of the support layer may comprise bonding the plurality of conductive traces to the surface of the support layer with an adhesive. This may provide effective bonding between the support layer and the plurality of conductive traces, whilst minimising a thickness of the busbar. In particular, this may avoid having to use mechanical fasteners such bolts or clamps, which might increase a thickness of the busbar. The adhesive may be applied to the support layer prior to arranging the plurality of conductive traces on the support layer. For example, the adhesive may be coated (e.g. sprayed) onto the support layer. Additionally or alternatively, the adhesive may be applied to the plurality of conductive traces, prior to arranging the plurality of conductive traces on the support layer.

According to a fifth aspect of the invention, there is provided a method of manufacturing a battery, the method comprising: arranging a plurality of battery cells side-by-side, each battery cell having a positive terminal and a negative terminal at a first end of the battery cell; manufacturing a busbar according to the method of the fourth aspect of the invention; arranging the busbar at the first end of the plurality of battery cells; and electrically connecting the plurality of conductive traces to the plurality of battery cells via the contact portions, such that the plurality of conductive traces connects the plurality of battery cells in series and/or parallel.

The method of the fifth aspect of the invention may be used to manufacture a battery according to the second aspect of the invention. The method of manufacturing the battery includes the method of the fourth aspect of the invention for manufacturing the busbar. Accordingly, features discussed above in relation to any preceding aspect of the invention may be shared with the fifth aspect of the invention.

Electrically connecting the plurality of conductive traces to the plurality of battery cells may comprise connecting the contact portions to the terminals at the first end of the plurality of battery cells. Any suitable technique for connecting the contact portions to the terminals on the battery cells may be used, such as welding, soldering or other techniques for forming electrical connections.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are discussed below with reference to the accompanying drawings, in which: Fig. la is a schematic diagram showing a perspective view of a battery according to an embodiment of the invention; Fig. lb is a schematic diagram showing a perspective view of the battery of Fig. la, where a busbar of the battery is omitted for illustration purposes; Fig. 2 is a schematic diagram showing a plan view of a support layer that may form part of a busbar according to an embodiment of the invention; Fig. 3 is a schematic diagram showing a plan view of a plurality of conductive traces that may form part of a busbar according to an embodiment of the invention, prior to removal of connecting portions; Fig. 4a is a schematic diagram showing a top view of an assembly including the support layer of Fig. 2 and the plurality of conductive traces of Fig. 3; Fig. 4b is a schematic diagram showing a bottom view of the assembly of Fig. 4a; Fig. 5a is a schematic diagram showing a top view of a busbar according to an embodiment of the invention; Fig. 5b is a schematic diagram showing a bottom view of the busbar of Fig. 5a; Fig. 6 is a schematic diagram showing a top view of a busbar according to an embodiment of the invention; Fig. 7 is a schematic diagram showing a top view of a busbar according to an embodiment of the invention; and Fig. 8 is a schematic cross-sectional front view of an electric vehicle according to an embodiment of the invention.

DETAILED DESCRIPTION; FURTHER OPTIONAL FEATURES

Figs. la and lb are schematic diagrams showing perspective views of a battery 100 according to an embodiment of the invention. The battery 100 includes a busbar 102 and a plurality of battery cells 104. For illustration purposes, the busbar 102 is omitted from Fig. lb, although the dashed lines indicate the position of the busbar 102. The busbar 102 on its own also constitutes an embodiment of the invention.

The battery cells 104 are cylindrical battery cells such as lithium-ion battery cells, although other types of battery cells may be used. A positive terminal 106 and a negative terminal 108 are exposed at a first end of each battery cell 104. As shown, the positive terminal 106 is located in a centre of the first end of each battery cell 104, whilst the negative terminal 108 surrounds the positive terminal 106. The negative terminal 108 of each battery cell 104 may be formed by a casing of the battery cell 104, such that the negative terminal 108 may extend along sides and/or a second end of the battery cell 104. The battery cells 104 are arranged side-by-side in multiple rows, such that the first ends of the plurality of battery cells 104 are aligned in a direction normal to a longitudinal direction of the plurality of battery cells 104. In other words, the first ends of the plurality of battery cells 104 may be substantially aligned in a plane that is normal to the longitudinal direction of the plurality of battery cells 104. The longitudinal direction of the plurality of battery cells 104 is indicated by a dashed line 110, which corresponds to a central axis of one of the cylindrical battery cells 104.

The busbar 102 is arranged at the first end of the plurality of battery cells 104. The busbar 102 comprises a support layer 112 which is formed of an insulating material having a Young's modulus equal to or greater than 10 GPa. Additionally, the support layer 112 has a thickness of at most 1 mm. For example, the support layer 112 may be formed of a composite material, such as a fibre-reinforced polymer material. A particular example of a material that is suitable for the support layer 112 is an FR-4 fibreglass material, as FR-4 materials have a Young's modulus greater than 20 GPa.

A first surface of the support layer 112 faces towards and abuts the first end of the plurality of battery cells 104. A plurality of apertures 114 is formed in the support layer 112, to expose the positive terminal 106 and negative terminal 108 at the first end of each battery cell 104. In particular, each aperture 114 is aligned with the first end of a corresponding battery cell 104, in order to expose the positive and negative terminals 106, 108 at the first end of that battery cell 104. Thus, the apertures 114 are arranged in rows matching the side-by-side arrangement of battery cells 104. In this manner, as shown in Fig. la, the positive and negative terminals 106, 108 at the first ends of the battery cells 104 are accessible via the apertures 114.

Multiple support elements in the form of tabs 116 are arranged around edges of the apertures 114, in order to engage the first end of the plurality of battery cells 104. In the example shown in Fig. la, three tabs 116 extend from the edge of each aperture 114 towards a centre of the aperture 114. The tabs 116 around each aperture 114 are arranged to abut the first end of the corresponding battery cell 104, in order to support the support layer 112 at the first end of the battery cell 104. In particular, the tabs 116 are arranged to extend over part of the first end of the corresponding battery cell 104, whilst leaving at least part of the positive terminal 106 and the negative terminal 108 exposed. In Fig. la, the tabs 116 leave the positive terminals 106 completely exposed, whilst the tabs 116 partially cover the negative terminals 108. Accordingly, the support layer 112 is supported against the first end of the plurality of battery cells 104 via the tabs 116 around each aperture 114. Additionally, the apertures 116 may be arranged to leave vents located at the first ends of the battery cells 104 exposed. In particular, the battery cells 104 may include vents located at their first ends for venting gasses in case of overheating. Arranging the apertures 114 at the first ends of the battery cells 104 may ensure that the support layer 112 does not block venting of the battery cells 104.

A plurality of conductive traces 118 is disposed on a second surface of the support layer 112, opposite to the first surface that faces towards the plurality of battery cells 104. In this manner, the support layer 112 is disposed between the first end of the plurality of battery cells 104 and the plurality of conductive traces 118. Thus, the support layer 112 electrically isolates the plurality of conductive traces 118 from the plurality of battery cells 104. The thickness of the support layer 112 referred to above corresponds to a distance between the opposing first surface and second surface of the support layer 112.

The plurality of conductive traces 118 includes multiple parallel conductive strips 120, with each conductive strip 120 arranged on the support layer 112 such that it extends between adjacent rows of apertures 114. In this manner, each conductive strip 120 is located between adjacent rows of battery cells 104. The conductive strips 120 extend in a first direction, parallel to the rows of apertures 114 and battery cells 104. The plurality of conductive traces 118 further includes contact portions which extend laterally from the conductive strips 120, such that they extend over the apertures 114 in order to electrically connect the plurality of conductive traces 118 to the positive and negative terminals 106, 108 at the first ends of the battery cells 104. In more detail, each conductive strip 120 includes a first set of contact portions 122 extending laterally from a first side of the conductive strip 120 and a second set of contact portions 124 extending laterally from a second side of the conductive strip 120. Each contact portion in the first set of contact portions 122 is arranged to contact a corresponding positive terminal 106 of the plurality of battery cells 104, whilst each contact portion in the second set of contact portions 124 is arranged to contact a corresponding negative terminal 108 of the plurality of battery cells 104. Each contact portion is electrically connected to its corresponding terminal, e.g. via welding or other suitable technique.

As each conductive strip 120 is located between adjacent rows of battery cells 104, the first set of contact portions 122 of a given conductive strip 120 is electrically connected to the positive terminals 106 of battery cells 104 located in a first row (on a first side of the conductive strip 120), and the second set of contact portions 124 of that conductive strip 120 is electrically connected to the negative terminals 108 of battery cells located in a second row (on a second, opposite side of the conductive strip 120). In this manner, the plurality of conductive traces 118 acts to connect battery cells 104 in adjacent rows in series, whilst connecting battery cells 104 within a same row in parallel.

With the busbar 102 arranged at the first end of the plurality of battery cells 104, the support layer 112 may act to restrain (e.g. resist) motion of the battery cells 104 along the longitudinal direction 110. In particular, due to the high Young's modulus of the support layer 112, the support layer 112 may absorb shocks experienced by the battery 100 and help maintain the battery cells 104 in place. Thus, the busbar 102 acts to both electrically connect the plurality of battery cells 104 together, as well as to restrain motion of the battery cells 104 and absorb shocks experienced by the battery cells 104. Therefore, no additional support frame may be needed at the first end of the plurality of battery cells 104 to strengthen the battery 100, meaning that a total size (e.g. height) of the battery 100 can be reduced.

The battery 100 may also comprise features for restraining (e.g. resisting) motion of the battery cells 104 in other directions (e.g. in directions normal to the longitudinal direction 110).

For example, the battery 100 may comprise a frame or framework (not shown) that extends around sides of the plurality of battery cells, in order to prevent lateral motion of the plurality of battery cells 104. The frame may include a plurality of holes which match the arrangement of the plurality of battery cells 104, such that each battery cell 104 is received in a respective hole in the frame. In this manner, lateral motion of each battery cell 104 is constrained by the frame.

The frame may be positioned at any suitable position along a length of the battery cells 104, so as not to add to a total height of the battery 100. For example, the frame may be located towards a middle or towards an end of the battery cells 104.

In one example, a first frame may be located around the first end of the plurality of battery cells 104, such that the first frame abuts the first surface of the support layer 112 (i.e. the surface of the support layer 112 that faces towards the first end of the plurality of battery cells 104). The support layer 112 may be secured to the first frame, in order to hold the busbar 102 at the first end of the plurality of battery cells 104. For instance, the support layer 112 may be bonded to the first frame using an adhesive, and/or secured to the first frame using a mechanical fastener such as a bolt or screw. Where a bolt or screw is used, the bolt or screw may be countersunk so that it does not protrude above the second surface of the support layer 112. Optionally, a second frame may be located around a second (opposite) end of the plurality of battery cells 104. Thus, the first frame and the second frame may be located at opposite ends of the plurality of battery cells 104, which may serve to constrain the ends of the battery cells 104 and minimise lateral motion of the battery cells 104.

Additionally or alternatively to the frame(s) mentioned above, the plurality of battery cells 104 may be held together with an adhesive. In one example, the plurality of battery cells 104 may be partially or fully encased in adhesive, e.g. in a potting medium. Where a frame is used, adhesive (e.g. potting medium) may be applied to the battery cells 104 around the frame, so that only parts of the battery cells 104 are encased in adhesive. This may result in the battery 100 being lighter than when the battery cells 104 are fully encased in adhesive, and may facilitate dissipating heat from the battery cells 104 whilst still providing structural support for dealing with stresses experienced by the battery 100.

A method for manufacturing a busbar according to an embodiment of the invention will now be described with reference to Figs. 2, 3, 4a and 4b. The method may be used, for example, to make the busbar 102 described above.

In a first step, a support layer 200 is formed from an insulating material. In particular, the support layer 200 is formed of a planar sheet of insulating material having a Young's modulus of at least 10 GPa, the sheet having a thickness of at most 1 mm. The sheet of insulating material may be a sheet of composite material such as glass fibre reinforced material or an aramid fibre reinforced material. A plurality of apertures 202 is cut into the sheet of insulating material, as shown in Fig. 2. The apertures 202 are arranged in multiple rows, and fulfil the function discussed above in relation to the apertures 114, namely exposing terminals at a first end of a plurality of battery cells. Thus, the arrangement of the apertures 202 may match an arrangement of a plurality of battery cells with which the busbar is to be used. In line with the discussion above relating to the battery 100, the apertures include support elements in the form of tabs 204 which extend from the edges of the apertures 202. The tabs 204 are arranged to abut the first end of the plurality of battery cells to support the support layer 200 against the plurality of battery cells. The apertures 202 may be cut in the sheet of insulating material using any suitable cutting technique, such as waterjet cutting, laser cutting, or router cutting. Advantageously, fibre-reinforced composite materials are well suited to such cutting techniques, thus enabling high precision cutting of the apertures 202 whilst providing a highly rigid support layer 200.

Next, in a second step, a plurality of conductive traces 300 is formed, as shown in Fig. 3.

The plurality of conductive traces 300 is formed from a sheet of conductive material, such as aluminium, copper, nickel plated copper, or any other suitable conductive material. The sheet of conductive material may preferably have a thickness of at most 0.6 mm. For example, the sheet of conductive material may have a thickness between 0.1 mm and 0.5 mm. The plurality of conductive traces 300 is formed by cutting the sheet of conductive material, e.g. using waterjet cutting, laser cutting, or chemical etching. As shown, the plurality of conductive traces 300 includes multiple parallel conductive strips 302 which extend in a first direction. Each conductive strip 302 (except for the outermost conductive strips 302) includes a first set of contact portions 304 that extends laterally from a first side of the conductive strip 302, and a second set of contact portions 306 that extends laterally from a second side of the conductive strip 302. A first outermost conductive strip 302a defines a first outer edge of the plurality of conductive traces 300, and only has a first set of contact portions 304. A second outermost conductive strip 302b defines a second outer edge of the plurality of conductive traces 300, and only has a second set of contact portions 306.

The sheet of conductive material is cut so as to leave connecting portions 308 located at ends of the conductive strips 302, and which connect the conductive strips 302 together. In this manner, the plurality of conductive traces 300 can be handled as a single component. Weak points 310 are introduced at connections between the conductive strips 302 and the connecting portions 308. In particular, as shown in Fig. 3, the weak points 310 are introduced at ends of the conductive strips 302. The weak points 310 correspond to areas where the thickness of the conductive material is reduced compared to other parts of the plurality of conductive traces 300 (i.e. compared to the original sheet of conductive material). The weak points 310 may be introduced using various suitable techniques, such as scoring or etching, in order to remove part of the thickness of the conductive material.

Next, to form the busbar, the plurality of conductive traces 300 is bonded to the support layer 200 using an adhesive. This can be achieved by coating or spraying the adhesive onto a surface of the support layer 200 and/or a surface of the plurality of conductive traces 300, and then pressing the surface of the plurality of conductive traces 300 and the surface of the support layer 200 together. Figs. 4a and 4b show views of an assembly of the plurality of conductive traces 300 and the support layer 200, after the plurality of conductive traces 300 have been bonded to the surface of the support layer 200. Fig. 4a shows a top view of the assembly, i.e. looking down towards the surface of the support layer 200 to which the plurality of conductive traces 300 is bonded. Fig. 4b shows a bottom view of the assembly, i.e. looking up towards an opposite surface of the support layer 200 which is arranged to abut the first end of the plurality of battery cells when in use. As can be seen in the top view of Fig. 4a, the plurality of conductive traces 300 is arranged such that the conductive strips 302 extend between adjacent rows of apertures 202 in the support layer 200. Moreover the plurality of conductive traces 300 is arranged such that the contact portions 304, 306 extend over the apertures 202 in the support layer 200. Additionally, the plurality of conductive traces 300 is arranged such that the weak points 310 are located at edges of the support layer 200. The plurality of conductive traces 300 can be positioned relative to the support layer using a mounting jig or other suitable alignment apparatus. The plurality of conductive traces 300 may be compressed onto the support layer during curing of the adhesive, in order to ensure effective bonding between the plurality of conductive traces 300 and the support layer 200.

Once the plurality of conductive traces 300 has been bonded to the support layer 200, the connecting portions 308 are disconnected from the plurality of conductive traces 300 at the weak points 310. For example, the connecting portions 308 may be broken and/or cut off at the weak points 310. The weak points 310 may facilitate disconnecting the connecting portions 308 from the plurality of conductive traces 300, and serve to guide breaking and/or cutting off of the connecting portions 308. Figs. 5a and 5b show top and bottom views, respectively, of a completed busbar 500, following the disconnecting of the connecting portions 308 from the plurality of conductive traces 300. The busbar 500 may then be connected in a battery, e.g. as discussed above in relation to the busbar 102 of the battery 100.

Fig. 6 shows a top view of a busbar 600 according to an embodiment of the invention. The busbar 600 has a similar structure to the busbar 500 described above. Therefore, features of the busbar 600 which correspond to features of the busbar 500 are indicated in Fig. 6 using the same reference numerals as in Figs. 5a and 5b, and are not described again.

Whereas the conductive strips 302 of the busbar 500 terminate at edges of the support layer 200, the conductive strips 302 of the busbar 600 have a first set of termination ends 602 located at a first end of the conductive strips 302, the first set of termination ends 602 extending beyond a boundary (i.e. an edge) of the support layer 200. Additionally, the conductive strips 302 of the busbar 600 have a second set of termination ends 604 located at a second, opposite end of the conductive strips 302, the second set of termination ends 604 lying within the boundary of the support layer 200. In other words, the conductive strips 302 may terminate at their second end before reaching an edge of the support layer 200. The first set of termination ends 602 may facilitate making electrical connections to the busbar 600. For example, where the busbar 600 is used in a battery with a plurality of battery cells (e.g. like battery 100), the first set of termination ends 602 may be used to connect the plurality of battery cells to other parts of the battery (such as to a battery management system) or to another battery. On the other hand, locating the second set of termination ends 604 within the boundary of the support layer 200 may serve to avoid unwanted electrical connections, e.g. shorts, to the plurality of conductive traces 300, as the support layer 200 may act as a buffer between the second set of termination ends 604 and other components.

Fig. 7 shows a top view of a busbar 700 according to an embodiment of the invention. The busbar 700 has a similar structure to the busbar 500 described above. Therefore, features of the busbar 700 which correspond to features of the busbar 500 are indicated in Fig. 7 using the same reference numerals as in Figs. 5a and 5b, and are not described again.

The conductive strips 302 of the busbar 500 all have a same width. In contrast, in the busbar 700, the first and second outermost conductive strips 302a, 302b have a width which is larger than the width of the other (i.e. inner) conductive strips 302. In particular, the width of the first outermost conductive strip 302a is arranged such that part of the width of the first outermost conductive strip 302a overhangs a first side edge 702 of the support layer 200 (the position of the first side edge 702 is indicated by dashed lines in Fig. 7). Likewise, the width of the second outermost conductive strip 302b is arranged such that part of the width of the second outermost conductive strip 302b overhangs a second side edge 704 of the support layer 200 (the position of the second side edge 704 is indicated by dashed lines in Fig. 7). The overhanging portions of the first and second outermost conductive strips 302a, 302b may act as termination ends which serve as terminals or connectors for electrically connecting the busbar 700 to other parts. For example, where the busbar 700 is used in a battery with a plurality of battery cells (e.g. like battery 100), the overhanging portions of the first and second outermost conductive strips 302a, 302b may be used to connect the plurality of battery cells to other parts of the battery (such as to a battery management system) or to another battery.

Where the busbar 700 is used in the battery 100 discussed above, and where the battery 100 includes the first frame positioned around the first end of the plurality of battery cells 104, the overhanging portions of the first and second outermost conductive strips 302a, 302b may be folded or bent, e.g. at an angle of 90 degrees relative to a plane defined by the support layer 200. In this manner, the overhanging portions of the first and second outermost conductive strips 302a, 302b may be bonded to a side surface of the first frame, using an adhesive and/or a mechanical fastener such as a bolt or screw (which may be countersunk).

It will be appreciated that a busbar according to the invention may include various combinations of the arrangements of conductive strips, termination ends, and overhanging portions described above in relation to busbars 500, 600 and 700.

Fig. 8 shows a schematic front cross-sectional view of part of an electric vehicle 800 according to an embodiment of the invention. The vehicle 800 is a road car, and may include four wheels (not shown) that are coupled to a chassis of the vehicle 800. The vehicle 800 comprises a cockpit 802 in which a seat 804 is located, the seat 804 being configured to receive an occupant of the vehicle 800. In addition to the seat 804, the cockpit 802 contains any controls and displays necessary for controlling the vehicle 800, e.g. steering wheel, accelerator pedal, brake pedal, dashboard.

The vehicle 800 further includes a battery system for powering the vehicle 800. The battery system is disposed in sides of the vehicle 800, with a first portion 806 of the battery system being located on a left-hand side of the cockpit 802 and a second portion 808 of the battery system being located on a right-hand side of the cockpit 802. The first and second portions 806, 808 of the battery system may be housed in respective compartments defined between the cockpit 802 and an external body 810 of the vehicle 800. Each of the first and second portions 806, 808 of the battery system includes at least one respective battery module 812, where each battery module 812 corresponds to a battery according to the invention. For example, each battery module 812 may correspond to the battery 100 described above.

As can be seen in Fig. 8, the battery modules 812 are arranged such that a longitudinal direction of a plurality of battery cells in each battery module 812 is substantially parallel to a ground surface on which the vehicle 800 is disposed. In other words, the longitudinal direction of the plurality of battery cells in each battery module 812 is substantially horizontal. For example, where the battery 100 is used for the battery modules 812, the longitudinal direction 110 of the cylindrical battery cells 104 may be arranged substantially horizontally. Moreover, the longitudinal axis of the plurality of battery cells in each battery module 812 is substantially parallel to a longitudinal axis of the vehicle 800. In other words, the longitudinal direction of the plurality of battery cells is substantially aligned with a direction of travel of the vehicle 800. As a result, a busbar (e.g. busbar 102) in each battery module 812 extends in a substantially vertical direction. Thus, the busbar may act to resist longitudinal motions of the battery cells, e.g. when the vehicle 800 goes around a bend. Moreover, due to the small thickness of the busbar of the invention, a length of the vehicle 800 may be reduced, e.g. compared to where a battery system using larger electrical connectors and support frames is used.

Claims (25)

1. CLAIMS1. A busbar for a battery comprising a plurality of battery cells arranged side-by-side, the busbar comprising: a support layer formed of an insulating material, wherein a Young's modulus of the support layer is equal to or greater than 10 GPa and a thickness of the support layer is equal to or less than 1 mm, the support layer being configured to support a first end of the plurality of battery cells; and a plurality of conductive traces disposed on the support layer, the plurality of conductive traces comprising contact portions for contacting terminals located at the first end of the plurality of battery cells.
2. 2. A busbar according to claim 1, wherein the insulating material comprises a composite material.
3. 3. A busbar according to claim 2, wherein the composite material is a fibre-reinforced polymer material.
4. 4. A busbar according to any preceding claim, wherein a plurality of apertures is formed in the support layer for exposing terminals at the first end of the plurality of battery cells, and wherein the contact portions extend over the apertures.
5. 5. A busbar according to claim 4, wherein the support layer comprises, for each aperture in the plurality of apertures, one or more support elements at an edge of the aperture for engaging the first end of one of the plurality of battery cells.
6. 6. A busbar according to any preceding claim, wherein the plurality of conductive traces comprises a plurality of substantially parallel conductive strips, and wherein the contact portions extend laterally from the conductive strips.
7. 7. A busbar according to any preceding claim, wherein the plurality of conductive traces is bonded to the support layer with an adhesive
8. 8. A busbar according to any preceding claim, wherein the Young's modulus of the support layer is equal to or greater than 20 GPa
9. 9. A busbar according to any preceding claim, wherein the thickness of the support layer is between 0.2 mm and 0.8 mm.
10. 10. A busbar according to any preceding claim, wherein the plurality of conductive traces has a thickness of 0.6 mm or less.
11. 11. A busbar according to any preceding claim, wherein the support layer is formed of a continuous sheet of the insulating material.
12. 12. A busbar according to any preceding claim, wherein the plurality of conductive traces are formed from a single sheet of conductive material.
13. 13. A busbar according to any preceding claim, wherein the plurality of conductive traces includes a first set of termination ends that extend beyond a boundary of the support layer.
14. 14. A busbar according to any preceding claim, wherein the plurality of conductive traces includes a second set of termination ends that lies within a boundary of the support layer. 15
15. 15. A battery comprising: a plurality of battery cells arranged side-by-side, each battery cell having a positive terminal and a negative terminal at a first end of the battery cell; a busbar according to any preceding claim; wherein the busbar is arranged at the first end of the plurality of battery cells; and wherein the plurality of conductive traces is electrically connected to the plurality of battery cells via the contact portions, such that the plurality of conductive traces connects the plurality of battery cells in series and/or parallel.
16. 16. A battery according to claim 15, wherein each contact portion is welded to a respective terminal on one of the plurality of battery cells.
17. 17. An electric vehicle comprising a battery according to claim 15 or 16.
18. 18. An electric vehicle according to claim 17, wherein the battery cells in the plurality of battery cells are cylindrical, and the battery is arranged such that a longitudinal direction of the plurality of battery cells is substantially parallel to a ground surface on which the vehicle is disposed.
19. 19. A method of manufacturing a busbar for a battery comprising a plurality of cylindrical battery cells arranged side-by-side, the method comprising: forming a support layer from a sheet of insulating material, wherein a Young's modulus of the support layer is equal to or greater than 10 GPa and a thickness of the support layer is equal to or less than 1 mm, the support layer being configured to support a first end of the plurality of battery cells; forming a plurality of conductive traces from a sheet of conductive material, the plurality of conductive traces comprising contact portions for contacting terminals located at the first end of the plurality of battery cells; and securing the plurality of conductive traces to a surface of the support layer.
20. 20. A method according to claim 19, wherein forming the support layer comprises cutting a plurality of apertures in the sheet of insulating material, the plurality of apertures being for exposing terminals at the first end of the plurality of battery cells, and wherein the plurality of conductive traces are arranged such that the contact portions extend over the apertures.
21. 21. A method according to claim 19 or 20, wherein forming the plurality of conductive traces comprises cutting the sheet of conductive material to form the plurality of conductive traces. 15
22. 22. A method according claim 21 wherein: the sheet of conductive material is cut such that the plurality of conductive traces are connected together via a connecting portion of the sheet of conductive material; and after securing the plurality of conductive traces to the surface of the support layer, the connecting portion is disconnected from the plurality of conductive traces.
23. 23. A method according to claim 22, further comprising introducing weak points at connections between the plurality of conductive traces and the connecting portion, wherein the connecting portion is disconnected from the plurality of conductive traces at the weak points. 25
24. 24. A method according to any one of claims 19 to 23, wherein securing the plurality of conductive traces to the surface of the support layer comprises bonding the plurality of conductive traces to the surface of the support layer with an adhesive.
25. 25. A method of manufacturing a battery, the method comprising: arranging a plurality of battery cells side-by-side, each battery cell having a positive terminal and a negative terminal at a first end of the battery cell; manufacturing a busbar according to the method of one of claims 19 to 24; arranging the busbar at the first end of the plurality of battery cells; and electrically connecting the plurality of conductive traces to the plurality of battery cells via the contact portions, such that the plurality of conductive traces connects the plurality of battery cells in series and/or parallel.