A research team has uncovered new findings regarding lithium-sulphur pouch cells at the BAMline of BESSY II, providing a fresh understanding of the factors that affect the efficiency and durability of this important battery technology.
Researchers from HZB and the Fraunhofer Institute for Material and Beam Technology (IWS) in Dresden have made significant strides in understanding lithium-sulphur pouch cells at the BAMline of BESSY II. Through complementary analyses at HZB’s imaging facility and additional measurements, they have revealed processes that hinder the performance and lifespan of this valuable battery type, as detailed in their study published in the journal Advanced Energy Materials.
Lithium-sulphur batteries offer several advantages compared to traditional lithium batteries: they utilize the widely available material sulfur, eliminate the need for critical elements like cobalt and nickel, and can achieve remarkably high specific energy densities. Prototype cells have demonstrated energy densities of up to 500 Wh/kg, nearly double that of current lithium-ion batteries.
Investigating degradation processes
Despite their advantages, lithium-sulphur batteries are notably more prone to degradation. During the charging and discharging cycles, dissolved polysulphides and sulfur compounds form on the lithium electrode, which gradually diminishes the battery’s performance and lifespan. “Our research focuses on understanding these processes to enhance the performance of this battery type,” explains HZB physicist Dr. Sebastian Risse, who leads a team at HZB dedicated to the operando analysis of batteries.
The pouch cell laboratory at HZB
Dr. Risse is concentrating on pouch cells, a battery format commonly used in the industry. To support this research, HZB’s Institute for Electrochemical Energy Storage (CE-IEES), directed by Prof. Yan Lu, has established a lab dedicated to creating lithium-sulphur batteries in the requisite pouch format. Here, researchers can manufacture and study a diverse range of lithium-sulphur pouch cells. As part of the BMBF-supported ‘SkaLiS’ project, coordinated by Sebastian Risse, a detailed study on lithium-sulphur pouch cells has been published by a team from the Fraunhofer Institute for Material and Beam Technology (IWS) in the journal Advanced Energy Materials.
Multimodal testing setup
The battery cells were examined using a setup crafted at HZB that incorporates various techniques such as impedance spectroscopy, temperature distribution analysis, force measurement, and X-ray imaging (from both synchrotron and laboratory sources) during charging and discharging phases. “For the first time, we were able to observe and document both the growth of lithium dendrites and the dissolution and reformation of sulfur crystals in a multi-layer battery operation,” states Dr. Rafael Müller, HZB chemist and the primary author of the study.
Phase-contrast radiography at BESSY II
Specifically, phase-contrast radiography utilizing coherent synchrotron light at the BAM beamline at BESSY II enabled researchers to monitor the structure of the less absorbent lithium metal and correlate it with other measurements, creating a well-rounded understanding. X-ray analyses performed at the HZB imaging lab, in collaboration with Dr. Ingo Manke’s imaging group, also provided insights into the formation of high-absorbance sulfur crystals during battery operation.
Future outlook: High-energy battery systems
“Our findings connect fundamental research to practical technology applications, offering valuable insights into the scalability of this battery method and the advancement of high-energy battery systems,” comments Risse. Among other discoveries, the team identified a promising new design from IWS Dresden: a perforated and significantly lighter cathode current collector that does not compromise the battery’s performance.
The outcomes of this research aim to enhance the functionality and lifespan of lithium-sulphur batteries, ensuring that this innovative battery type can satisfy the demands of both mobile and stationary energy storage solutions.
