Cleaning up Operando Battery X-Ray Diffraction with Total Scattering Computed Tomography

Abstract

Operando X-ray diffraction (XRD) and total scattering investigations of battery electrode materials allow us to relate structure and electrochemical properties down to the atomic level. By studying the materials under real working conditions without allowing the materials to relax or react outside the battery, we obtain the most reliable possible structural information. Unfortunately, in most operando experiments, even when we use heavily modified cells to remove barriers to our probe radiation, the signal from the material of interest is significantly obscured by contributions from other battery components. The problems are increased when we seek to study electrode materials which either are, or become, amorphous during battery cycling: removing non-sample contributions is an essential part of pre-processing total scattering data for pair distribution function (PDF) analysis, which can reveal the local structures of non-crystalline materials.To address these problems, we have developed operando total scattering computed tomography (TSCT) as a method for obtaining clean, 5-dimensional (3-D space, time, and chemical structure) information on working batteries. The method allows us to select specific areas of the active electrode and obtain XRD and PDF information without any contributions from other components of the battery. The high-quality of the resulting data has allowed us to understand the cycling mechanisms of poorly scattering, amorphous, alloying anode materials (sodium cycling in phosphorus)[1], and complex, multi component, conversion-alloying systems (lithium cycling in bismuth vanadate)[2]. While the first example mainly uses the focusing power of TSCT to obtain the best possible data, the latter case uses the spatial resolution of the data to identify signs of a longer-term deactivation mechanism based on agglomeration of the nanoclusters of active material during repeated cycling. Further studies are currently in progress to apply the method to other difficult anode systems including silicon.[1] J. Sottmann, M. Di Michiel, H. Fjellvåg, L. Malavasi, S. Margadonna, P. Vajeeston, G.B.M. Vaughan, D.S. Wragg, Chemical Structures of Specific Sodium Ion Battery Components Determined by Operando Pair Distribution Function and X-ray Diffraction Computed Tomography, Angew. Chem. Int. Ed. 56, pp. 11385-11389, 2017[2] J. Sottmann, A. Ruud, Ø.S. Fjellvåg, G.B.M. Vaughan, M. Di Michel, H. Fjellvåg, O.I. Lebedev, P. Vajeeston, D.S. Wragg, 5D total scattering computed tomography reveals the full reaction mechanism of a bismuth vanadate lithium ion battery anode, Phys. Chem. Chem. Phys. 24, pp.27075-27085, 2022 Figure 1