Operando investigation of the lithium/sulfur battery system by coupled X-ray absorption tomography and X-ray diffraction computed tomography

High capacity sulfur electrodes are expected to be used in the next-generation of high energy density and low cost rechargeable lithium batteries. The positive sulfur electrode undergoes complex electrochemical reactions, which cause morphological changes of the composite electrode while cycling. In the course to deeper understand the failures of this rather complex, but promising technology, the operando technics are in the heart of the advanced characterizations. In this study, a new electrochemical cell was designed which allows, for the first time, the combination operando of multimodal X-ray characterizations: the absorption tomography to study the morphological evolution of electrodes, and the X-ray diffraction computed tomography to probe locally the structural modification of the crystalline active materials S-8 and Li2S. The combination of these two techniques simultaneously with the electrochemical cycling, allows the production of correlated 3D-maps of quantitative phase distributions and morphology in the electrode, with time resolution on the scale of battery kinetics. It was thus possible to show the heterogeneous behavior in the bulk of the electrode and to propose kinetics law.