The Future of Advanced Air Mobility

Solithor Joins Forces with Aerostructures Group Sonaca to Develop Pouch-cell Batteries

Battery developer Solithor is partnering with aerospace group Sonaca to engineer solid-state lithium batteries for regional aircraft and eVTOL vehicles. Under a memorandum of understanding signed last week, the Belgium-based companies said they intend to bring to market high-density rechargeable technology that will meet the power and safety needs of the emerging electric aviation sector and also potentially satellite and defense systems.

Solithor, which was formed in January 2022 with just over $10 million in seed funding, will be responsible for research and development, testing, format design, and the production of 10Ah- to 40-Ah cells. Sonaca, which last year earned EASA design organization approval, will develop the battery packaging, including all related management systems, and will also certify the new pouch-cell batteries. The first test cells are expected to be delivered to Sonaca later this year so that systems integration work can begin.

According to Solithor co-founder and CEO Huw Hampson-Jones, the company is targeting breakthroughs in volumetric energy density­—the measure of a battery’s energy in relation to its volume—to soon reach 800 watt-hours per liter, rising to 1,000 Wh/l, compared with what he says are current norms of around 600 Wh/l. The company believes that it could drive up gravimetric energy density–defined as available energy per unit mass of a substance–from current norms of between 220 and 260 Wh/kg up to around 350 Wh/kg.

Apart from Solithor’s proprietary technology, based on patents covering nano-solid composite electrolytes and nano-anodes, the company is differentiating itself by focusing entirely on a pouch-cell architecture. It takes the view that cylindrical batteries come with too high a weight penalty from the aluminum casing.

The Solithor batteries will use lithium metal, which the company says is a key element in improving energy density. By taking a cathode-agnostic approach to the formulas used, it can work with Lithium-Nickel-Manganese-Cobalt-Oxide or Lithium-Ion Phosphate.

Reflecting on the limitations of batteries currently available to electric aircraft manufacturers, Hampson-Jones told FutureFlight that his team is taking a phased approach to improve battery performance and seeking to establish long-term relationships with partners over the next 10 to 15 years. He has been in talks with several aircraft developers, with a view to demonstrating how Solithor’s new batteries could result in more competitive mission profiles for their products.

Improving Battery Integration With Aircraft

The alliance with Sonaca is expected to provide the airframing and aerostructures expertise needed to help aircraft designers optimize the architecture for battery integration. One objective, for instance, might be to eliminate the need for casing and install the pouch cells directly into aircraft wings.

According to Hampson-Jones, Solithor and Sonaca aim to have a technology demonstrator aircraft ready to start flight testing with a partner between 2027 and 2029. It expects to have preproduction examples of the new batteries ready to conduct ground testing between 2025 and 2027.

Charleroi-based Sonaca develops and produces aerospace components for aircraft manufacturers including Airbus, Boeing, Embraer, Bombardier, Dassault, Gulfstream, Honda Jet, and Pilatus. It has 3,500 employees in four countries besides Belgium, including Romania, Canada, the U.S., and Brazil. The company’s strategy is focused on being able to contribute to the production of low-carbon aircraft by 2035 and achieve carbon neutrality by 2050.

Solithor is based around 60 miles away at Sint-Truiden in the Flanders region of Belgium, where a 3,000-sq-m test facility is available at the site of a former automotive plant. Hampson-Jones, who was previously CEO of UK-based battery technology group Oxis Energy, said that these facilities will available to partners and customers to assess the performance and production integrity of the batteries. The nearby Limburg Regional Airport could be used for flight testing of new electric aircraft.

The company, which has a 25-member engineering team, is a spinoff from the Imec group, from which it derives significant intellectual property. Product development is being led by co-founder and chief technology officer Fanny Bardé, who is an expert in battery technology.