Researchers from Helmholtz-Zentrum Berlin have found a real-time method to observe lithium ions’ movement in solid-state batteries, using varying transparency and isotopes.
Lithium-based solid-state batteries offer certain benefits, including a reduced risk of flammability. However, they tend to be less potent. The reason for this diminished power is that the lithium ions must traverse through a solid electrolyte, a process that can be slow and unwieldy.
A research team from Helmholtz-Zentrum Berlin, Germany and several collaborators have witnessed lithium ions’ movement through the electrolyte in real-time for the inaugural time. They leveraged the knowledge that lithium typically presents as a blend of two isotopes: approximately 90% being lithium7, which doesn’t affect neutron beams, and the residual 10% being lithium6, which has a high neutron absorption rate.
The researchers believe they could utilize the varying transparency of the lithium ions to track their journey through the electrolyte. The approach proved highly effective with operando neutron radiography and in situ neutron tomography. For the study, a lithium-sulfur battery was constructed with an anode composed entirely of lithium6, while the solid electrolyte was made up of the customary combination of Li6 and Li7. During the initial discharge, this enabled the team to differentiate between the mobile lithium ions that were diffusing through the cell from the anode and those that were initially present in the solid electrolyte.
The researchers have utilized operando neutron radiography to observe the diffusion of lithium ions through the cell. Concurrently, in situ neutron tomography furnished a three-dimensional perspective of the distribution of the confined lithium ions within the cell, both in charged and discharged states. The most significant finding is that the diffusion of Li is neither homogeneous nor uniform. Furthermore, this method enables the testing of new electrolytes with the Li isotope Li6, accelerating the discovery of electrolytes that facilitate particularly effective lithium diffusion.
The researchers say that understanding the transport pathways of lithium ions through a solid electrolyte separator is a vital step towards developing reliable and functional solid-state batteries.
Reference: Robert Bradbury et al, Visualizing Lithium Ion Transport in Solid‐State Li–S Batteries Using 6Li Contrast Enhanced Neutron Imaging, Advanced Functional Materials (2023). DOI: 10.1002/adfm.202302619
