Bristling to work
In tests with a number of unnamed battery companies, Dr Boulanger says VACNT electrodes achieved an energy density of 500wh/kg in one battery and up to 1,400 watt-hours per litre in another. This is roughly double what a typical Li-ion battery can manage in terms of weight and volume respectively. "We have done that very easily," he adds, "so we believe there is more room for improvement."
One firm that NAWA does admit to working with is Saft, a large batterymaker owned by Total, a French oil giant keen to diversify from fossil fuels. Among Saft's customers are several Formula 1 teams which use some electric power in their racing cars. Saft has also teamed up with PSA group, a big European carmaker, to manufacture batteries for electric vehicles.
Naturally, the new device's success will depend on the cost of manufacturing it. NAWA is already constructing a mass-production line to make VACNT plates for its latest supercapacitors. The process used, which grows nanotubes on both sides of a roll of aluminium foil, would, says Ulrik Grape, NAWA's chief executive, transfer easily to an existing battery-production line and might even reduce battery-making costs. He expects the first versions of the supercapacitor-battery hybrids to be in production by 2023.
Whether such hybrid storage will be able to compete with conventional Li-ions remains to be seen. Li-ion batteries have the advantage of incumbency, and batterymakers have invested billions of dollars in huge "gigafactories" to turn them out in droves. Yet, for all the hype surrounding electric cars, doubts about Li-ions linger in many customers' minds. Range-anxiety, recharge rate and cost all combine to induce a hesitation to reach for the credit card. Mixing the spice of a supercapacitor with the stamina of a battery might overcome at least the first two of these objections, and thus, at last, truly launch an era of carefree electric motoring.