Flexible membranes of synthetic diamond could boost the performance of electric vehicles (EVs) while significantly reducing battery charging time, their creators have said.

Developed at Fraunhofer USA in Michigan, an international affiliate of the German research institute, the ‘wafer-thin’ nanomembranes of synthetic diamond can be integrated into electronic components, reducing the local heat load by up to 10-times.

Diamond is known for its high thermal conductivity, which is four- to five-times higher than copper. “For this reason, it is a particularly interesting material when it comes to cooling power electronics in electric transportation, photovoltaics or storage systems,” a Fraunhofer announcement said.

The flexible membranes could replace oxide or nitride layers between components and heat-dissipating copper layers, which are electrically insulating but have poor thermal conductivity, the team said. “We want to replace this intermediate layer with our diamond nanomembrane, which is extremely effective at transferring heat to the copper, as diamond can be processed into conductive paths,” said Dr Matthias Mühle, head of the diamond technologies group at Fraunhofer USA Centre Midwest.

The flexible and electrically insulating nanomembranes are thinner than a human hair, and can be integrated directly to cool EV power electronics, which transfer traction energy from the battery to the electric motor and convert direct current to alternating current. “The energy efficiency, service life and road performance of electric cars are improved significantly as a result,” the announcement said. The diamond membranes also reportedly enable charging speeds that are five-times higher. “As our membrane is flexible and free-standing, it can be positioned anywhere on the component or the copper, or integrated directly into the cooling circuit.”

Mühle and his team achieved this by growing the polycrystalline diamond nanomembrane on a separate silicon wafer, then detaching it, turning it over and etching away the back of the diamond layer. Heat treatment bonds the micron-thick membranes to electronic components. The nanomembrane can be produced on a wafer scale (4 inches and larger), making it well suited for industrial applications, the announcement said.

Tests with inverters and transformers are due to start this year. A patent has been filed for the development.