A step towards overcoming pressure sensitivity in solid-state batteries

Use of a solid-state electrolyte opens the door to the use of lithium metal electrodes, which offer a ten-fold increase in energy density compared to graphite electrodes. However, they currently require impractical pressures to avoid loss of contact with the solid electrolyte during discharge. As such, overcoming pressure sensitivity is a key goal on the route to commercialising solid-state batteries for EVs and other applications.

Scientists at the University of Oxford working on the SOLBAT project have developed a lithium-rich alloy that reduces the pressure requirements of solid-state batteries. Research published in Nature Communications details the change of properties of lithium metal alloys with varied magnesium content. Microstructure, mechanics, diffusion dynamics, passivation layer chemistry and electrochemical performance were all measured. The experimental results were complemented by modelling, demonstrating the broad technical capability and diverse expertise established within the project.

Researchers discovered that light (<5%) magnesium alloying of lithium metal significantly improves electrochemical performance and reduces pressure sensitivity in the industry-relevant operating conditions of ambient temperature and low stack pressure with only a small energy density penalty. A patent application has been filed and the team is collaborating with a major OEM to produce prototype pouch cells. The SOLBAT project continues to develop alloys to further increase charge/discharge rate capability in low-pressure, ambient temperature conditions.

Image: Diamond nanoindentation tip in contact with the surface of a lithiummagnesium alloy sample, measuring mechanical properties.

Case study published December 2024.