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Sixonia brings eGraphene into OCULUS, a European project on solid-state lithium-sulfur cells

Lithium-sulfur cells with a solid electrolyte could store more energy per kilogram than today's lithium-ion batteries, provided they last and can be scaled. In the European research project OCULUS, Sixonia works on that question with Fraunhofer IWS, TU Dresden, the University of Salzburg and the National Institute of Chemistry in Ljubljana.

Why lithium-sulfur, and why solid-state?

Sulfur is abundant and inexpensive, and as a cathode material it offers a very high theoretical energy density per kilogram. In cells with liquid electrolytes, however, polysulfides dissolve during cycling, the cells age quickly and the practical energy density stays far below what the chemistry promises. Solid sulfide electrolytes avoid this problem in principle. That matters wherever weight limits range and payload, above all in electric aircraft and heavy-duty trucks.


What OCULUS sets out to build

The consortium aims for a scalable high-energy all-solid-state lithium-sulfur cell that cycles reversibly and works without excess indium in the anode. The target is technology readiness level 4, a working cell stack in the lab with a lithium-metal anode, a solid separator and a cathode of sulfur, carbon and the sulfide electrolyte argyrodite. Two material developments lead there. A nano- and microstructured cathode composite is meant to put more of the sulfur to work. A lightweight lithium/carbon-fibre/graphene anode is meant to stop lithium from creeping along grain boundaries and forming dendrites, which leads to early cell failure. Operando scattering and spectroscopy on the running cell, together with cryo-electron microscopy, show which processes limit performance and guide the material design.


Where eGraphene comes in

Sixonia is the industrial partner in the consortium. We contribute eGraphene suspensions and our know-how in dispersion and coating. Graphene is part of two of the four project objectives. Sulfur barely conducts electricity, so the cathode needs a fine conductive network that reaches the active material. In the anode, graphene is part of the lightweight composite meant to keep metallic lithium in place. In both roles eGraphene stores no energy itself; it makes sure electrons get where the cell needs them. What we learn about eGraphene in a chemistry where interfaces decide over cell life feeds directly into our work on lithium-metal and solid-state cells.


What the results could mean

OCULUS ends at TRL 4. Several development steps lie between a cell stack in the lab and a battery in a truck. The decisive questions, however, are answered at this stage: how much of its sulfur a cathode can actually use, how a lithium anode survives repeated cycling, and whether the cell can be built with scalable, environmentally friendly processes and without excess indium. If those answers hold, batteries for electric aircraft and trucks could become lighter for the same stored energy, and safer, because a solid electrolyte replaces the flammable liquid.


Who makes OCULUS possible

OCULUS brings together partners from Saxony, Austria and Slovenia under the European M-ERA.NET programme, coordinated by Fraunhofer IWS in Dresden. The Saxon partners Fraunhofer IWS, TU Dresden and Sixonia are funded by the Free State of Saxony and co-funded by the European Union through the European Regional Development Fund (ERDF). FFG funds the Austrian partner, and the Slovenian Ministry of Higher Education, Science and Innovation funds the partner in Ljubljana.

We are grateful to the Free State of Saxony and the European Union for this support. It lets a young company work on a cell chemistry that is years from the market, alongside institutes whose analytical methods a start-up could not build on its own. We will report results on this page as the project progresses.



Project facts

  • Project: OCULUS – Operando Techniques for Conversion Reaction Engineering in High-Energy Lithium Sulfur Solid-State Batteries

  • Duration: 2025–2028

  • Program: M-ERA.NET Call 2024, topic “Sustainable advanced materials for energy”

  • Coordinator: Fraunhofer IWS, Dresden

  • Partners: Fraunhofer IWS (DE) · TU Dresden, Chair of Inorganic Chemistry I (DE) · Sixonia (DE) · University of Salzburg (AT) · National Institute of Chemistry, Ljubljana (SI)

  • Target: Working all-solid-state lithium-sulfur cell stack at TRL 4

  • Funding (Saxon partners): Free State of Saxony, co-funded by the European Union (ERDF 2021–2027)