​Lithium-sulfur batteries could provide double the energy density of the lithium-ion batteries that are widely used today. These batteries are less toxic than their lithium-ion counterparts and their active materials are less expensive. However, if lithium-sulfur technology is to reach its full potential and one day outperform lithium-ion, it will need to overcome two major hurdles: performance, which currently declines rapidly with use, and lifespan. The first step toward improving the batteries is to characterize them during operation to understand the chemical mechanisms that underpin degradation.

CEA-Liten researchers combined two X-ray tomography techniques available at ESRF with powerful data processing methods to observe the chemical and morphological changes inside the battery during cycling. The tests were done on an experimental cell tailored to the characterization technique used and representative of an actual battery design. This enabled the researchers to produce a high-resolution map of the entire battery.

These deep insights into the degradation mechanisms at work inside lithium-sulfur batteries in operation will position researchers to come up with solutions for improving the batteries. The advanced characterization techniques used will now be available for the study of other battery technologies like lithium metal and solid state.