Nano-Based Ultracap Tech Boosts EV Power Density
French nanomaterials specialist NAWA Technologies is aiming to bring a new dimension to the automotive industry’s use of the word “hybrid.” It is aiming to link high efficiency new technology carbon nano-based ultracapacitors with lithium-ion batteries, to create a dual energy source for high volume electric vehicles.
NAWA claims its Ultra Fast Carbon Battery technology now in pilot production, can deliver between three and five times higher power and energy density than existing ultracapacitors.
The company has stated that in the “long term” its technology will enable it to develop hybrid ultracapacitor cells with performance levels approaching or surpassing current (or even advanced) lithium batteries in terms of fast charging and lifecycle.
The result of its R&D work, said CEO Ulrik Grape, is confidence that high volume manufacture of a radical energy storage system will help overcome many of the frustrations that continue to dog the wholesale public acceptance of automotive electric motive power.
“The unique aspect of the technology of our Ultra Fast Carbon Battery is our successful development of vertically aligned specially coated nanotubes, allowing us to increase the energy density of the carbon nanotubes or basic capacitor," he told Automotive Engineering.
“We can accept the charge and release it exceptionally fast," he explained. "This is a high power technology that can assist the automotive sector’s requirement to achieve ever greater energy density.” Grape joined NAWA in 2017, having been part of the management team at California solid-state lithium-ion battery start-up SEEO, recently acquired by Bosch.
NAWA’s claim is that its new generation of energy-recouping batteries could be recharged “in seconds for up to a million cycles,” ideal for autonomous vehicles, notably shared cars. Carbon-based, the new Ultra Fast Battery configuration is said by the company not to suffer the thermal issues of conventional storage systems. It could also fit technologically with hydrogen fuel cells.
Regen braking benefits
NAWA (NAno technology to fight against global WArming) Technologies, a 2013 spin-out business from the French Atomic and Alternative Energies’ Organization (CEA), states that the battery is capable of storing up to five times more energy than existing capacitors, would play a key part in electrified vehicle development.
A significant aspect of the NAWA battery involves the use of the uniformly applied polymer coating of the nanotubes. But why is vertical alignment of nanotubes so important? Said Grape: “It’s about regimenting electrons and ions, smoothing their path instead of their taking a random route. It’s rather like the perfectly ordered bristles of a toothbrush!”
Benefits of the Ultra Fast Carbon Battery include the capability of very high speed delivery of a charge (compared to conventional batteries, typically in a few seconds or milliseconds for very small cell sizes and with less dependence on temperature) to meet sudden acceleration requirements. Also, and possibly more importantly, to harvest as much braking energy as possible. Grape believes the industry has not paid sufficient attention to this, although he accepts that OEMs and suppliers are becoming ever less conservative in adopting new technology.
“European companies in particular are showing strong interest in our new battery," he stated. "In a 48V or larger system we could perhaps recoup up to 90%-plus of available braking energy.”
NAWA development work has included the simulation of a Formula E hybrid battery featuring lithium-ion batteries and its own ultracapacitors. This may be regarded as the exotic end of the auto industry but Grape believes it is a relevant program. “We looked at performance on several race circuits and received information from drive cycles which showed only about 20% of energy recovery when braking for turns using only lithium-ion batteries,” he noted.
Mass reduction, cost
Grape believes very significant overall weight reduction could be achieved using the hybrid ultracapacitor and lithium-ion system. “Initially it could typically be reduced from 300 kg to 200 kg," he said. "Further savings of another 100 kg could be possible through optimization of the overall electrical system. But we are not storing as much energy as lithium-ion batteries and are not professing to replace them. Our system would work in conjunction with lithium-ion; storage would need to involve the performance of the whole system not just our technology."
Significantly, the overall system is expected to have a longer in-service life than stand-alone lithium-ion batteries, as the ultracapacitors handle the heavy loads and the lithium-ion address the autonomy.
Grape is cautious on the emotional subject of range enhancement potential via the use of its more efficient ultracapacitor technology and resultant energy harvesting.
“Depending on the outcome of discussions with the auto industry regarding all aspects of a production system, it could be as high as 40% to 50%, but it is too early to be specific,” he said.
Likely cost is inevitably the major issue when new technology looms on the automotive horizon. Grape sees this as being “orders of magnitude less" than that of super- or ultracapacitors currently available,” adding that precise figures are still to be refined.
Core technology and manufacture of the Ultra Fast Carbon Battery are claimed to be “very comparable” to those of the photovoltaic industry in general, although for application to high volume automotive production, a unique process would be applied.
Instead of coating a mixture of dozens of powders, additives and binders—very fragile when charging and discharging, NAWA's approach is different. A liquid containing a high content of carbon atoms is injected then vaporized, which allows the growth of a uniform, robust and flexible "carpet" of the vertically aligned nanotubes.
NAWA’s pilot production unit is at its French R&D facility at Rousset, Aix-en-Provence. The second generation of the pilot line is scheduled to be up and running in 2019. Initial applications are likely to be for power tools. The automotive qualification process— working together with the industry—is expected to follow. Grape said the aim is for initial production for automotive to begin in four to five years, then ramping up to high volumes.
NAWA founder and COO, Pascal Boulanger, added: “What is really exciting is the sheer potential of ultracapacitors. With the Ultra Fast Carbon Battery, we have combined the best nanotechnology with the best clean technology.”