Swedish car-battery maker Northvolt is expanding into aviation, as it targets the nascent field of decarbonising commercial flight.

Lower-weight, higher-density lithium metal batteries developed by Northvolt’s Cuberg subsidiary improve upon lithium ion, which is suitable only for test flights and demonstrations, said Richard Wang, the California unit’s chief executive officer.

Cuberg has signed up several major customers for both ground testing and flight testing, and hopes to announce some in the next quarter, Wang said in an interview. The company aims to tackle emerging markets for fixed-wing electric planes, hybrids and electric vertical takeoff and landing aircraft, or eVTOLs.

Cuberg was already working on aviation battery systems when it was acquired by Northvolt two years ago. The deal gave the startup access to its Swedish parent’s experience with battery systems and packs, opening opportunities in a developing market for electric-powered air travel that could reach tens of billions of dollars by 2030, Wang said.

“Between our battery cell and battery systems people, we probably have perhaps the largest and best resourced aviation battery strategy in the world,” Wang said.

While lithium-ion batteries have pushed the range of all-electric passenger cars beyond 300 miles, they’re too heavy for all but the smallest of aircraft, limiting their commercial use. Even the smallest passenger jetliners are out of reach for battery propulsion. European planemaker Airbus is betting on hydrogen as an alternative to fossil-derived jet fuel.

Hybrid-electric startup Heart Aerospace and a handful of others are working on small, battery-powered planes and hybrids. The Swedish manufacturer’s ES-30, in development, would seat up to 30 passengers and have a range of 200 km in all-electric mode, according to its website.

So far, Cuberg has built an aviation module based on its 20 amp-hour lithium metal cells, with specific energy of 280 watt-hours per kilogram and energy density of 320 watt-hours per liter, according to a statement Tuesday.

It’s also built and shipped next-generation 20 Ah cells with specific energy of 405 Wh/kg.

In practice, each 30% improvement in a battery’s energy per weight might improve its effective range by 40% or 50%, Wang said.

Northvolt, a rare European company doing battle with Asian car-battery manufacturers, has so far secured more than $55-billion of contracts from electric-car makers including BMW, Volkswagen, Volvo Car and Polestar. Last week, the company announced it had developed a battery cell with truck-maker Scania for heavy electric vehicles that lasts for the entire lifetime of a truck.