Fraunhofer ISI has developed a roadmap for solid-state batteries that looks at a broad spectrum from the material, component and cell to the application level. In it, existing as well as the latest research findings are critically evaluated and the development potential of solid-state batteries is compared with that of established lithium-ion batteries for the period of the next 10 years. The roadmap shows: Solid-state batteries have a lot of potential, but must prove their commercialisability in the next five years.
Current lithium-ion batteries (LIB) are based on liquid electrolytes and are currently used in many mobile and stationary applications. However, their optimisation potential is diminishing as technology advances – it is expected that this technology will gradually reach its limits in the coming decade. Solid-state batteries (SSB) with solid electrolytes, which are currently under development and could come onto the market in the coming years, promise improvements in several important performance parameters. The entire battery sector could benefit from this in the long term, as well as from the parallel further development of LIB technology, which will remain dominant for the next few years.
The Fraunhofer ISI roadmap takes a closer look at the three currently most promising solid electrolyte variants – oxide electrolytes, sulphide electrolytes and polymer electrolytes – and compares them with the expected developments in lithium-ion batteries.
The results show that solid-state batteries (SSB) will have to bring significant performance improvements compared to state-of-the-art liquid electrolyte LIB in order to achieve relevant market shares. Important performance parameters are energy density, safety, lifetime, cost and fast charging capability. Solid-state batteries have the potential to surpass classic LIBs in terms of energy density, especially since they allow the use of Li-metal anodes. Moreover, their safety is considered high even at the cell level because they do not contain flammable liquids. Their lifespan could even exceed that of liquid electrolyte LIBs, but technical challenges, such as volume changes during charging or discharging, still need to be overcome to achieve this. The cost of solid-state batteries is likely to be significantly higher than current LIBs at the beginning of their market introduction, partly due to lower production volumes. The fast-charging capability of solid-state batteries is currently limited by the mostly low ionic conductivity of the solid electrolytes, but their design could be specially adapted for this. An important problem here is that improving one performance parameter often comes at the expense of another. The batteries can or must therefore be tailored accordingly to specific requirements and applications.
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The automotive market holds the greatest overall potential for solid-state batteries and is likely to become their main area of application in the medium to long term. Solid-state batteries based on sulphide electrolytes could initially be used in the consumer sector, as the requirements and test procedures are less stringent here. For solid oxide batteries, the automotive market is likely to be the first area of application – from around 2028. In view of higher initial costs, it is conceivable that solid batteries will initially be used in upper market segments. Cost reductions through scaling effects could help the technology in the long term to open up further areas of application, such as in trucks and stationary storage or, after 2035, in passenger aviation.
In terms of future market developments, solid-state battery production, which currently remains below 2 GWh globally and is based on polymer SSB, is expected to increase strongly between 2025 and 2030 – when solid-state batteries based on oxide and sulphide electrolytes enter the market. For 2030, the Fraunhofer researchers estimate the capacity at 15 to 55 GWh and for 2035 at 40 to 120 GWh, which corresponds to about 1 to 2 % of the LIB market that will have emerged by then. Liquid electrolyte LIBs will thus dominate the market for the foreseeable future.
In addition to assessments of application areas and market developments, the roadmap makes statements about which hurdles solid-state batteries will still have to overcome in the future for market penetration. Dr Thomas Schmaltz, who coordinated the research work on the roadmap at Fraunhofer ISI, names three central challenges:
“Firstly, it is currently not yet foreseeable which solid-state battery concept will ultimately have the greatest performance, which requires the parallel development of different approaches and thus higher investments. Secondly, solid-state batteries will be in constant competition with liquid electrolyte lithium-ion batteries and will have to bring significant performance improvements due to their initially higher costs, which suggests initial applications will be more in the premium sector. Thirdly, strong private and public funding beyond pure research funding is needed to catch up with Asian and US players in patenting, product development, production technologies, pilot production as well as start-up and industrial activities – if this is successful, Europe can play a leading role in the development of solid-state battery technologies in the future”.
The roadmap can be downloaded here