Researchers develop lighter solid-state batteries

31.10.2025

Source: E & M powernews

A new cell chemistry is set to make lithium-sulphur batteries lighter and safer. Researchers at the Fraunhofer IWS are working on solid-state structures with a reduced electrolyte content.

Lithium-sulphur batteries are considered by researchers to be a promising alternative to established lithium-ion systems. They could theoretically store twice as much energy and would be significantly lighter. In practice, however, chemical side reactions prevent this potential from being fully exploited.

The reason for this is that the liquid electrolyte attacks the materials and causes the cells to age too quickly. Researchers at the Fraunhofer Institute for Material and Beam Technology IWS in Dresden want to eliminate these weak points - with a new solid-state chemistry that works without liquid components and is intended to extend the service life.

Their work focuses on two research projects: "AnSiLiS", funded by the German Federal Ministry of Education and Research, and "TALISSMAN", supported by the EU's Horizon Europe program. Both projects aim to develop practical cell concepts that combine high energy densities with stable cycles and increased safety. The scientists are working on a solid-state lithium-sulfur cell that is significantly lighter than current systems with the same capacity.

According to the Fraunhofer IWS, its approach differs from previous concepts. While conventional lithium-sulphur cells use liquid electrolytes, the Dresden-based institute relies on a solid cell structure. It converts sulphur directly into solid lithium sulphide. This prevents the formation of soluble polysulphides. These are considered the main cause of material losses and accelerated capacity degradation in conventional cells. According to Fraunhofer, initial laboratory tests show that energy densities of over 600 watt hours per kilogram can be achieved with the new architecture - more than twice as much as with today's lithium-ion batteries.

Details of the research projects

In the "AnSiLiS" (Anode Silicon Lithium Sulfur) project, the IWS is working with universities and research centers to develop a more stable cell structure. The aim is to match the materials so that the batteries store more energy and last longer.

The EU project "TALISSMAN" ("Towards Advanced Lithium-Sulfur batteries for Sustainable Mobility Applications") aims to transfer this basic research into industrial applications. Under the leadership of the Basque institute CIDETEC, nine partners from Spain, France, Italy and Germany are developing two generations of cells for electromobility. They should achieve energy densities of up to 550 watt hours per kilogram and work with non-flammable, gel-like electrolytes. Production costs are also expected to fall to below 75 euros/kWh. For comparison: according to an analysis by Bloomberg NEF (December 2024), today's lithium-ion batteries average around 109 euros/kWh.

Production and pilot applications

The "DRYtraec" process developed by the Fraunhofer IWS plays a key role. The name is derived from the English verb to dry and the term track (path, process path). Electrodes are coated dry and without solvents. The materials are pressed into stable films. This eliminates the need for energy-intensive drying. Until now, the active materials have been stirred into solvent-containing pastes, applied to films and then dried in an energy-intensive process.

According to the institute, the energy requirement with "DRYtraec" is reduced by up to 30 percent compared to the conventional wet process, and CO2 emissions are also noticeably lower. Fraunhofer assures that the process can be transferred to an industrial scale in roll-to-roll operation - a continuous process with coated film webs.

The prototypes are produced at the Advanced Battery Technology Center of the Fraunhofer IWS in Dresden. The electrodes are manufactured, stacked, sealed and tested there. In combination with analytics and process simulation, an end-to-end development chain from material to cell is created.

The researchers see the batteries being used primarily where weight and energy density are crucial - for example in aviation, drones or portable energy storage systems. Conventional lithium-ion batteries often reach their limits in these applications.

Author: Davina Spohn