HIGHLY CONDUCTIVE BUSBARS WITH ULTRA-CONDUCTIVITY COMPOSITE MADE OF CARBON NANOTULES FOR ELECTRICAL MACHINES

Abstract

A composite conductor for a vehicle, a drive system for a vehicle, and a method for forming a composite busbar for a vehicle. The composite conductor comprises a surface and a first copper strip laminated onto the surface. The composite conductor is electrically conductive and exhibits an electrical conductivity of 1.0 × 10⁷ Siemens per meter (S / m) or greater. The first copper strip comprises a layer of carbon nanotubes sandwiched between a first copper layer and a second copper layer. The composite busbar can be connected to a variety of windings in the stator of an electric motor.

Description

INITIATIONElectric and hybrid electric vehicle technology has been enabled by the development and use of rechargeable secondary batteries that power electric traction motors, servomotors, and other electronics of the vehicle. Busbars are used to establish switching connections between the windings in the motors and connect the windings to the phase connectors that are connected to the power electronics. Bus bars may be made in a variety of flat or hollow shapes and from a variety of materials such as iron, steel, copper, aluminum, bronze, silver, or gold. The material composition and cross section of a busbar determine the maximum current that can be conducted. Moreover, the connections between the bus bars and the windings or other components may cause heating effects.Traction motors operate with alternating current (AC). However, in the alternating current (AC) current distribution, the current density tends to be larger near the surface of the bus bar and decreases toward the core. This effectively reduces the cross section of the bus bars and increases the effective resistance. This effect, which is referred to as skin effect, increases with increasing frequency of the alternating current. To counteract this effect, a single busbar may be replaced by a series of smaller current carrying composite conductors or busbars.Thus, while current traction motor bus bars serve their purpose, there is a need for new and improved traction motor bus bars.SUMMARYIn several aspects, the present disclosure relates to a composite conductor for a vehicle. The composite conductor includes a surface and a first copper tape laminated to the surface. The composite conductor is electrically conductive and has an electrical conductivity of 1.0×10 7 Siemens per meter (S / m) or more. The first copper strip contains a layer of carbon nanotubes which lies between a first copper layer and a second copper layer.According to the above embodiments, the first copper layer comprises a copper foil and the second copper layer comprises a copper coating.According to any of the preceding embodiments, the first copper band has a thickness in the range of 10 microns to 40 microns.According to any of the above embodiments, the carbon nanotube layer has a thickness in the range of 2 nanometers to 50 nanometers, including all values and ranges included therein, and the copper coating layer has a thickness in the range of 0.1 to 3 micrometers.According to one of the above embodiments, the composite conductor is formed of one or more of the following materials selected from the group consisting of copper, aluminum and iron.According to one of the preceding embodiments, the composite conductor also comprises at least one additional carbon nanotube layer arranged on the second copper layer and at least one additional second copper layer arranged on the at least one additional carbon nanotube layer.According to one of the preceding embodiments, at least one additional copper tape is bonded to the first copper tape, which is bonded to the surface.According to one of the above embodiments, no intermetallic phases are formed on the surface.According to one of the above embodiments, a plurality of composite conductors are sintered together.According to one of the preceding embodiments, the composite conductor is in the form of a busbar. In further embodiments, the bus bar is attached to a plurality of windings of a stator. In yet another embodiment, a rotor is rotatably supported in the stator. And in still further embodiments, the bus bar is attached to an inverter.In several additional aspects, the present disclosure relates to a propulsion system for a vehicle. The drive system includes an electric motor. The electric motor includes a stator having a plurality of windings, a rotor disposed in the stator, and a composite bus bar connected to the plurality of windings. The composite bus bar includes a bus bar having a surface, the bus bar being formed of at least one material selected from the group consisting of copper, aluminum, and iron. The composite bus bar also includes a first copper tape laminated to the surface. The first copper tape includes a layer of carbon nanotubes sandwiched between a first copper foil layer and a second copper coating layer. In addition, the first copper ribbon has a thickness in the range of 10 micrometers to 40 micrometers. Further, the carbon nanotube layer has a thickness in the range of 2 nanometers to 50 nanometers, including all values and ranges included therein, and the copper coating layer has a thickness in the range of 0.1 to 3 micrometers.In each of the above embodiments, at least one additional carbon nanotube layer is disposed on the second copper layer, and at least one additional second copper layer is disposed on the at least one additional carbon nanotube layer.In each of the foregoing embodiments, at least one additional copper tape is laminated to the first copper tape that is bonded to the surface.In several additional aspects, the present disclosure relates to a method of forming a composite bus bar for a vehicle. The method includes heating a bus bar and a first copper ribbon. The first copper strip comprises a layer of carbon nanotubes lying between a first copper layer and a second copper layer. The method further includes laminating the first copper tape to the bus bar by applying a force to the bus bar and the first copper tape, and adhering the first copper tape to a surface of the bus bar. The method further includes heat treating the bus bar and the first copper ribbon.According to the above embodiments, the laminating comprises thermally rolling the first copper strip onto the surface, wherein the first copper strip has a first length before drawing and a second length in the range of 100 percent to less than 105 percent of the first length. Alternatively or additionally, the laminating comprises extrusion onto the first copper ribbon, wherein the first copper ribbon has a first length prior to drawing and a second length in the range of 100 percent to less than 105 percent of the first length. In further alternative embodiments of the foregoing, laminating comprises hot isostatic pressing of the first copper ribbon onto the surface of the busbar.BRIEF DESCRIPTION OF DRAWINGSThe drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. FIG. 1 illustrates a vehicle with a propulsion system using an electric traction motor according to various embodiments of the present disclosure; FIG. 2A illustrates a stator of a traction motor according to various embodiments of the present disclosure; FIG. 2B illustrates close-up of the stator of a traction motor according to various embodiments of the present disclosure; FIG. 3A illustrates a cross-sectional view of a composite bus bar according to various embodiments of the present disclosure; FIG. 3B illustrates a cross-sectional view of a copper tape according to various embodiments of the present disclosure; FIG. 4 illustrates a method of forming a conductive band according to various embodiments of the present disclosure; FIG. 5 illustrates a method of forming a composite conductive bus bar according to various embodiments of the present disclosure. FIG. 6 illustrates a schematic illustration of a lamination process according to various embodiments of the present disclosure. FIG. 7 illustrates an alternative schematic illustration of a lamination process according to various embodiments of the present disclosure. FIG. 8 illustrates yet another alternative schematic illustration of a lamination process according to various embodiments of the present disclosure; and FIG. 9 illustrates a busbar assembly in a process chamber according to various embodiments of the present disclosure.DETAILED DESCRIPTIONThe following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. Moreover, it is not intended to be limited by any explicit or implicit theory presented in the preceding introduction, summary, or the following detailed description. It should be understood that throughout the drawings, corresponding reference numerals designate like or corresponding parts and features.Reference will now be made in detail to several examples of the disclosure, which are illustrated in the accompanying drawings. Wherever possible, the same or like reference numbers will be used in the drawings and the specification to refer to the same or like parts or steps. The drawings are in simplified form and are not to scale.The present disclosure relates to a composite conductor for a vehicle having a copper tape applied on the surfaces of the composite conductor. The composite conductor is, in some embodiments, a composite bus bar that connects the windings of an electric motor in a vehicle to the battery or other components of a power electronics module, such as an inverter. Moreover, the present disclosure relates to a drive system for a vehicle including the composite bus bar. The present disclosure further relates to a method of forming a composite bus bar conductor.The term "vehicle" as used herein is not limited to automobiles. Although the present technology is described herein primarily in the context of electric vehicles, the technology is not limited to electric vehicles, but also includes hybrid electric vehicles. Moreover, the concepts may be used in a variety of applications, including components used in motor cycles, mopeds, locomotives, aircraft, watercraft and other vehicles, as well as other applications using batteries, such as portable power supplies such as those used to power remote worksites, emergency power supplies, and permanent power supplies connected to buildings and equipment all of which may be operated by, for example, solar or wind powered generator systems, power grids, and fuel based power generators such as gasoline or diesel generators, as well as Stirling engines.FIG. 1 illustrates a vehicle 100 having a propulsion system 120. The drive system 120 generally includes an electric motor 124 and a secondary battery 126 for powering the electric motor 124. In many embodiments of the propulsion system 120, the propulsion system 120 further includes an inverter 128 for converting direct current (DC) as provided by the battery 126 to alternating current (AC) as used by the electric motor 124. The inverter 128 may be included in a power electronics module 130, e.g., comprising transistors and diodes for switching the current from DC to AC and vice versa. In some embodiments, the battery is connected to the electric motor via the power electronics module.A controller 132 is connected to the inverter 128 and programmed to control and manage the operation of the electric motor 124 and associated hardware including the inverter 128. The electric motor 124 is connected to a transmission (drive unit) 136 and a powertrain 138 that transmits the mechanical force and rotation to the wheels 140 of the vehicle 100. The controller 132 includes one or more processors and tangible, non-transitory memory 134.Referring back to the electric motor 124, the electric motor 124 powered by the battery 126 includes a stator 142 and a rotor 144 rotatably disposed within the stator 142. The stator 142 is the stationary part of the electric motor 124. The stator 142 provides a rotating magnetic field that the stationary magnetic field of the rotor 144 attempts to align with so that the rotor 144 rotates in the so-called "motoring mode.". In applications with traction electric vehicles, the motor mode provides propulsion of the vehicle 100. In other applications, the rotating field 144 of the rotor (as caused by physical rotation) generates an electric current in the stator 142 -- this mode of operation is referred to as "generation" and the electric motor 124 thus used is used as a generator. In the generation mode, a portion of the energy recovered during braking, e.g., braking and stopping of the vehicle, is stored back into the battery 126.Reference is made to FIGS. 2A and 2B, which illustrate an example of the stator 142. The stator 142 may generally include a plurality of wire windings 148 that extend the length L of the stator 142. The wire windings 148 may be formed of, for example, copper or other conductive material. The wire windings 148 are connected to one or more composite bus bars 150 that connect the wire windings 148 to the inverter 128 in the power electronics module 130 and the battery 126.As illustrated in FIG. 3A, the composite bus bars 150 are formed of composite conductors including an electrically conductive bus bar 151 and electrically conductive copper tape 152. Electrically conductive may be understood herein as a measure of the ability of a material to conduct electrical current, and an electrically conductive material used herein has an electrical conductivity of 1.0×10 7 Siemens per meter (S / m) or more at 20 degrees Celsius, including all values and ranges from 1.0×10 7 S / m to 6.4×10 7 S / m. In some embodiments, the electrically conductive material of the busbar 151 is made of a metal or metal alloy, including copper, aluminum, iron, and alloys thereof.The copper tape 152 includes a layer of aligned carbon nanotubes 162 and is laminated to one or more surfaces 154 of a busbar 151. The copper tape 152 has an electrical conductivity greater than that of the bus bar 151 or another conductor. In some embodiments, the electrical conductivity is in the range of 5.5×10 7 S / m to 6.0×10 7 S / m at 20 degrees Celsius, including all values and ranges such as 5.80×10 7 S / m to 5.96×10 7 S / m. In additional or alternative embodiments, the electrical conductivity is in the range of 101 % to 500 % of IACS, including all values and ranges included therein. In some embodiments, the copper tape 152 may be applied to all surfaces 154 of the busbar 151, including the surfaces in the openings 156 defined by the busbar 151 (see FIG. 2B ). In other embodiments, more than one layer of copper tape 152 is applied to the surfaces 154 of the bus bar 151, e.g., in the range of two layers to 10 layers including all values and ranges included therein.FIG. 3B shows an embodiment of the copper ribbon 152. As seen in the figure, the copper tape 152 includes a first layer of copper foil 160. A first coating layer of carbon nanotubes 162 is deposited on the copper foil layer 160. The carbon nanotubes comprise single-walled nanotubes or, in alternative embodiments, may also comprise multi-walled nanotubes. Further, the carbon nanotubes may be doped with copper in an amount ranging from 0.1 volume percent to 50.0 volume percent of the total volume percent of nanotubes, including all values and ranges included therein. Carbon nanotubes 162 are generally aligned along their longitudinal axis A1, with the length of the ribbon also being aligned along A1. It should be appreciated that there may be embodiments where the orientation of the longitudinal axis A 1 of the carbon nanotubes 162 deviates from the longitudinal axis of the copper ribbon 152, depending on the application. A second coating layer of copper 164 is deposited on the carbon nanotubes 162, wherein the carbon nanotubes 162 come to lie between the two copper layers 160, 164. In further embodiments, the copper tape 152 may include additional carbon nanotube coating layers 162 interposed between additional copper coating layers 164.The copper ribbon 152 has a thickness in the range of 10 to 40 micrometers, including all values and ranges included therein. In some embodiments, the carbon nanotube layer 162 has a thickness in the range of 2 nanometers to 50 nanometers, including all values and ranges included therein, the copper coating layers 164 have a thickness in the range of 0.1 to 3 micrometers, including all values and ranges included therein, and the copper foil 160 has a thickness sufficient to achieve the thickness of the copper ribbon 152 of 10 micrometers to 40 micrometers, including all values and ranges included therein.In embodiments, as illustrated in the method 400 of FIG. 4 and with reference to FIGS. 3A and 3B, the copper tape 152 may be formed by depositing a layer of carbon nanotubes in a dispersion in block 402 onto a copper foil 160. The dispersion of carbon nanotubes (CNTs) may include carbon nanotubes dispersed in a solvent having a boiling point of above 100 degrees Celsius at standard atmospheric pressure, such as dimethylformamide (DMF) or n-methyl-2-pyrrolidone. The dispersion may also contain a binder such as polyvinylpyrrolidone. The carbon nanotube dispersion may be deposited by a process such as electro-spinning, electro-spraying, or by an air blade. After the solvent has evaporated, the copper (Cu) coating 164 is deposited on the carbon nanotube layer 162 in block 404. If multiple layers of carbon nanotubes and copper coatings are present, the method 400 may be repeated by depositing a layer of carbon nanotubes over the previously deposited copper coating layer.Referring now to FIG. 5, which further illustrates with reference to FIGS. 3A and 3B, a method 500 of forming a composite conductor, such as a composite bus bar 150, having a copper ribbon 152 laminated to a bus bar 151. In block 502, the copper ribbon 152 and the bus bar 151 may be heated to a temperature in the range of 50 degrees Celsius to 300 degrees Celsius, including all values and ranges included therein, such as in the range of 100 degrees Celsius to 200 degrees Celsius, below the solidus temperature of the copper, for a period in the range of 30 minutes to 240 minutes, including all values and ranges included therein. The solidus temperature is understood here as the temperature at which the metal or the metal alloy starts melting or liquifying. The solidus temperature of cast iron is, for example, in the range of 1141 degrees Celsius to 1157 degrees Celsius at standard pressure (101.325 kiloPascals) and in the range of 1535 degrees Celsius to 1545 degrees Celsius at standard pressure for iron. After heating or during heating, a force is applied to the bus bar 151 and the copper tape 152 in block 504 to thermally bond and laminate the copper tape 152 to the bus bar 151.Optionally, in block 506, a stress is applied to a surface 154 of the bus bar 151 by bonding. When a load is present, the copper ribbon 152 may be subjected to a load of up to 5% of the total initial length of the copper ribbon 152. That is, in some embodiments, the copper ribbon 152 may be stretched by up to 5% of the total starting length of the copper ribbon 152, including all values and ranges from 0.01% to 5% of the total length of the ribbon. Load is understood here to mean the length change, i.e. the difference between the final length and the original length divided by the original length.Thermal bonding and lamination can be accomplished by a number of processes, such as thermal rolling, extrusion, or hot isostatic pressing, discussed further below. The processes described herein can all take place at atmospheric pressure in air or an inert atmosphere, as well as in some cases under vacuum. Inert atmospheres may be, for example, argon or nitrogen gas.Thermal rolling, one embodiment of which is illustrated in FIG. 6, includes a process for rolling the bus bar 151 or other composite conductor, with copper ribbon 152 disposed on one or more surfaces 154, between two rotating rolls 172, 174 that apply a force F 1 to the bus bar 151 and the copper ribbon 152. In some embodiments, the applied force F 1 is in the range of 0.5 to 0.9 times the yield strength of the material of the bus bar at a particular temperature. The force F 1 used for, e.g., copper or iron may be in the range of 100 megapascals (MPa) to 120 MPa including all values and ranges included therein, and the force F 1 used for, e.g., aluminum may be in the range of 20 MPa to 30 MPa including all values and ranges included therein. In some embodiments, the force F1is about 10 to 20 percent of the yield strength of pure copper at room temperature, in the range of about 200 to 250 megaPascals, including all values and ranges included therein.In an alternative or additional embodiment, an example of which is illustrated in FIG. 7, for conductive materials such as aluminum, iron, steel, copper, or magnesium, an extrusion process may be used in which the material is extruded into an extrudate 702 having a desired shape from an extruder 704 and the copper ribbon 152 is applied to the extrudate 702 after exiting the die 710 of the extruder 704. During the extrusion process, the conductive material may be heated at a temperature in the range of 50 degrees Celsius to 300 degrees Celsius, including all values and ranges included therein, such as in the range of 100 degrees Celsius to 200 degrees Celsius, below the solidus temperature of the bus bar, for a period of time in the range of 30 minutes to 240 minutes, including all values and ranges included therein, such as at a temperature of 300 degrees Celsius to 500 degrees Celsius or 900 degrees Celsius to 950 degrees Celsius, including all values and ranges included therein. The force F 1 may be applied to the extrudate 702 and the copper strip 152 by rollers 706, 708. In some embodiments, the applied force F 1 is in the range of 0.5 to 0.9 times the yield strength of the material of the bus bar at a particular temperature. For example, in the extrusion of aluminum, the force may be in the range of 20 MPa to 30 MPa, including all values and ranges included therein, in some embodiments.In yet another embodiment, the copper strip 152 may be sintered with the bus bar 151 by hot isostatic pressing (HIP) or hot pressing. During the hot isostatic process, an example of which is illustrated in FIG. 8, a mold 800 may be used to apply a force F 1 around the bus bar 151 and the copper strip 152 illustrated as being provided on all sides of the bus bar 151. For copper and iron, the bus bar 151 and the copper strip 152 are heated to a temperature in the range of, for example, 800 degrees Celsius to 900 degrees Celsius, including all values and ranges included therein. Further, a pressure in the range of 100 MPa to 120 MPa including all the values and ranges contained therein is applied, and the pressure is maintained for one half hour or longer, for example, in the range of 30 minutes to 240 minutes including all the values and ranges contained therein. For aluminum, the bus bar 151 and the copper strip 152 are heated to a temperature in the range of, for example, 150 degrees Celsius to 250 degrees Celsius, including all values and ranges included therein. Further, a pressure in the range of 20 MPa to 30 MPa including all the values and ranges contained therein is applied, and the pressure is maintained for one half hour or longer, for example, in the range of 30 minutes to 240 minutes including all the values and ranges contained therein.After the thermal bonding, the laminated copper tape 152 and the bus bar 151, i.e., the composite bus bar 150, may be subjected to a further heat treatment in block 508. As illustrated in FIG. 9, the composite bus bars 150 are placed in a process chamber 900. In some embodiments, the process chamber 900 may be a furnace or an oil bath. For example, in some embodiments, the composite bus bar 150 may be quenched and cooled at a rate sufficient to prevent or achieve a reduction in applied stress. The heat treatment for aluminum bus bars including the laminated copper tape includes, for example, heating the aluminum bus bars including the laminated copper tape to a temperature in the range of 200 degrees Celsius to 300 degrees Celsius including all values and ranges included therein for a period of 1 hour to 3 hours including all values and ranges included therein. The heat treatment for copper bus bars including the laminated copper tape includes, for example, heating the copper bus bars including the laminated copper tape to a temperature in the range of 400 degrees Celsius to 600 degrees Celsius including all values and ranges included therein for a period of 1 hour to 3 hours including all values and ranges included therein.In additional or alternative embodiments of the foregoing, the copper tape 152 is applied during the process of forming the bus bar 151, e.g., when stamping the bus bars 151 from sheet metal material. For example, the copper tape 152 may be placed on the bus bar 151 and stamped with the bus bar 151. Alternatively, the copper tape 152 may be formed and cut during or after performing the above lamination processes, e.g., by punching, to correspond to the dimensions of the bus bar 151. For example, the copper ribbon 152 may be provided over the bus bar 151 and span the openings 156 that may be defined in the bus bar 151. After laminating the copper tape 152 to the bus bar 151, the copper tape 152 may be removed at the opening 156 to provide access to the opening 156 defined in the bus bar 151.Further, in embodiments, complete metallurgical bonds are made between the copper foil layer 160 of the copper strip 152 and the bus bar 151. That is, at least 99 percent and up to 100 percent of the interface between the copper strip 152 and the surface 154 of the bus bar 151 are metallurgically bonded together. Moreover, in some embodiments, there are no intermetallic phases present, which in some embodiments is facilitated by performing the foregoing processes in an inert environment, including a process chamber under vacuum. In alternative embodiments, the processes may take place in a reactive atmosphere to achieve the desired intermediate metallization at the interface between the copper ribbon 152 and the bus bar 151.While the composite conductors are described in terms of the composite bus bars 150 used herein, in some embodiments, the composite conductors may alternatively include wires, cables, hollow tubes, or plates formed from one or more conductive materials such as aluminum, copper, or iron. Moreover, in some embodiments, composite conductors forming bus bars may take any number of geometries, and not just those indicated and illustrated herein. Moreover, in some embodiments, a plurality of composite conductors are sintered together to form an array 904 of composite conductors, as illustrated in FIG. 9.The methods and systems described herein provide a number of advantages. These advantages include, for example, at least a five percent decrease in electrical resistance, at least a ten percent increase in current carrying capacity, and at least a ten percent improvement in strength as compared to pure copper, for example. Advantages also include enhancing the skin effect by adding the copper tape, thereby improving performance in relatively high frequency applications, such as electric motors running at 10,000 revolutions per minute or more at a frequency greater than 1,000 hertz, as well as overall conductivity in low speed applications, such as induction-type electric motors running at less than 10,000 revolutions per minute or less at a frequency less than 1,000 hertz, to improve system drive cycle efficiency. Yet another advantage is the increase of the power density. The further advantages include the possibility of applying adhesive tape even where coatings may be difficult to apply.The term "controller" and related terms, such as microcontroller, control module, module, controller, controller, processor, and similar terms, refer to one or various combinations of application specific integrated circuit(s) (ASIC), field programmable gate array (FPGA), electronic circuit(s), central processing unit(s), e.g., microprocessor(s), and associated non-transitory memory component(s) in the form of read-only memories and random access memories (read-only memories, programmable read-only memories, random access memories, hard disk drives, etc.). The controller 132 may also be comprised of a plurality of controllers that electrically communicate with each other. The controller 132 may be connected to other systems and / or controllers of the vehicle 100 such that the controller 132 may access data such as speed, acceleration, braking, and steering angle of the vehicle 100.A processor may be a custom or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor among multiple processors coupled to the controller 132, a semi-compound conductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, a combination thereof, or generally any device for executing instructions.The tangible, non-transitory memory 134 may include volatile and non-volatile storage in, for example, read only memory (ROM), random access memory (RAM), and keep alive memory (KAM). A KAM is a persistent or non-volatile memory that can be used to store various operating variables while the processor is off. Tangible, non-transitory memory 134 may be implemented using a variety of storage devices, such as programmable read-only memories (PROMs), erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), flash memory, or other electrical, magnetic, optical, or combined storage devices capable of storing data, some of which represent executable instructions, used by controller 132 to control various systems of vehicle 100.The description of the present disclosure is merely exemplary, and variations that do not depart from the gist of the present disclosure are intended to fall within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.

Claims

A composite conductor for a vehicle, comprising: a composite conductor having a surface, wherein the composite conductor is electrically conductive and has an electrical conductivity of 1.0×10 7 Siemens per meter (S / m) or more; and a first copper tape laminated to the surface, wherein the first copper tape includes a layer of carbon nanotubes interposed between a first copper layer and a second copper layer.The composite conductor of claim 1, wherein the first copper layer comprises a copper foil and the second copper layer comprises a copper coating.The composite conductor of claim 2, wherein the first copper ribbon has a thickness in the range of 10 microns to 40 microns.The composite conductor of claim 3, wherein the carbon nanotube layer has a thickness in the range of 2 nanometers to 50 nanometers, including all values and ranges included therein, and the copper coating layers have a thickness in the range of 0.1 to 3 micrometers.The composite conductor of claim 2, wherein the composite conductor is formed of one or more of the following materials selected from the group consisting of copper, aluminum, and iron.The composite conductor of claim 2, further comprising at least one additional carbon nanotube layer disposed on the second copper layer and at least one additional second copper layer disposed on the at least one additional carbon nanotube layer.The composite conductor of claim 2, wherein at least one additional copper tape is bonded to the first copper tape bonded to the surface.The composite conductor according to claim 2, wherein no intermetallic phases are formed on the surface.The composite conductor of claim 1, wherein a plurality of composite conductors are sintered together.A method of manufacturing a composite bus bar for a vehicle, comprising: heating a bus bar and a first copper tape, the first copper tape including a layer of carbon nanotubes sandwiched between a first copper layer and a second copper layer; laminating the first copper tape to the bus bar by applying a force to the bus bar and the first copper tape and adhering the first copper tape to a surface of the bus bar; and heat treating the bus bar and the first copper tape.

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