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Graphene-infused copper wire may be key for more efficient EVs

Electric vehicle charging. (Reference image by Open Grid Scheduler / Grid Engine, Wikimedia Commons).

Researchers at Pacific Northwest National Laboratory in the US have increased by 5% the conductivity of copper wire used in vehicle motor components.

According to the scientists – who partnered with General Motors to test out the souped-up copper wire – their invention can make a big difference in motor efficiency as less copper may be needed, which can reduce the weight and volume of various components that are expected to power future electric vehicles.

The new wire can make a big difference in motor efficiency as less copper may be needed

Using a new, patented and patent-pending manufacturing platform, the experts added graphene to copper and produced wire. The increase in conductivity compared to pure copper is made possible by a first-of-its-kind machine that combines and extrudes metal and composite materials, including copper.

The process has been dubbed ShAPE, which stands for Shear Assisted Processing and Extrusion. 

In this process, oppositional – or shear – force is applied by rotating a metal or composite as it is pushed through a die to create a new form. This approach creates internal heating by deforming the metal, which softens it and allows it to form into wires, tubes, and bars.

“ShAPE is the first process that has achieved improved conductivity in copper at the bulk scale, meaning it can produce materials in a size and format that industry currently uses,” Glenn Grant, the initiative’s principal investigator, said in a media statement. “The benefit of adding graphene to copper has been investigated before, but these efforts have primarily focused on thin films or layered structures that are extremely costly and time consuming to make. The ShAPE process is the first demonstration of considerable conductivity improvement in copper-graphene composites made by a truly scalable process.”

Researcher Keerti Kappagantula holds an ultra-high conductivity copper wire with graphene additives. (Image by Andrea Starr, courtesy of the PNNL).

According to Grant, adding graphene to copper has proved difficult because the additives do not blend uniformly, creating clumps and pore spaces within the structure. But the ShAPE process eliminates pore spaces while also distributing the additives within the metal uniformly, which may be the reason for improved electrical conductivity. 

“ShAPE’s uniform dispersion of the graphene is the reason only really tiny amounts of additive are needed — about six parts per million of graphene flakes — to get a substantial improvement of 5% in conductivity,” material scientist Keerti Kappagantula said in the brief. “Other methods require large quantities of graphene, which is very expensive to make, and still have not approached the high conductivity we’ve demonstrated at a bulk scale.”

Kappagantula said that General Motors Research and Development engineers verified the higher conductivity copper wire can be welded, brazed, and formed in exactly the same way as conventional copper wire. This indicates seamless integration with existing motor manufacturing processes. 

In the researcher’s view, the technology can apply to other industries that use copper to move electrical energy, including power transmission, electronics, wireless chargers, generators, under-sea cables, and batteries.