SoLi2S

Motivation

Lithium-sulfur batteries (Li-S) have significant potential as next-generation energy storage systems due to their high specific energy and low material costs. However, substantial improvements in cycle life and performance are still required for successful commercialization. Results from the BMBF-funded SoLiS project have demonstrated that sulfide-based solid electrolytes offer considerable advantages over liquid electrolytes and can be regarded as a game changer for solid-state lithium-sulfur batteries (Li-S SSBs) with with energy densities at prototype cell level exceeding 500 Wh/kg. Key advantages include the complete suppression of polysulfide formation, near-complete utilization of the active material, a low electrolyte content, scalable dry-coating processes, and high cycling stability. National and international research findings from recent years have highlighted the strong innovation and application potential of this technology and provide the foundation for the SoLi²S project.

Objectives and Approach

The objective of the SoLi²S project is to develop a new generation of solid-state lithium-sulfur battery cells with high energy and power density. The project targets a specific energy of more than 500 Wh/kg, discharge rates exceeding 1C, and a cycle life of more than 200 cycles in multilayer pouch cells at Technology Readiness Level (TRL) 5–6. Building directly on the results of the predecessor project SoLiS, the project follows an interdisciplinary approach involving partners from academia, applied research, and industry.

Implementation is structured around three key objectives:

1. Material innovations to enhance performance
2. Development of components and cells
3. Scale-up, manufacturing concepts, and technology assessment

In addition, the project aims to establish an R&D platform up to TRL 6, develop concepts for technology transfer into pilot-scale and industrial production environments, and create a comprehensive patent portfolio to support the future commercialization of the technology.

Innovation and Perspectives

Solid-state lithium-sulfur batteries offer significant innovation and commercialization potential for the Fraunhofer IWS and the Fraunhofer FFB. As the underlying scientific insights have only emerged in recent years and the research field is evolving rapidly, the SoLi²S project provides an opportunity to establish new scientific and technological benchmarks. In addition to building expertise and training highly qualified personnel, a key objective is to create a strong patent portfolio that will support the industrial exploitation of the technology in Germany.

Potential application areas for the technology will be identified through benchmarking using application-relevant load profiles. The establishment of an industrial advisory board and the development of a commercialization roadmap will facilitate the early preparation of technology transfer activities. In the short term, the project results are intended to be transferred to research production lines, accompanied by the further scale-up of materials and manufacturing processes. In the medium term, small-scale production runs of solid-state lithium-sulfur cells will be manufactured and extensively tested. Through close collaboration with industrial partners across the entire value chain, combined with a clear patent and commercialization strategy, the project aims to establish a sustainable technological advantage for the production of next-generation Li-S battery cells in Germany and Europe.