MS18-02 - Order-Disorder Transitions in Battery Electrodes Studied by Operando X-ray Scattering


Dorthe Bomholdt Ravnsbæk (University of Southern Denmark, Denmark)

Development of novel electrode materials for intercalation type batteries have in the past focused on highly crystalline materials with the capability to retain long-range order during cycling. However, recent years have seen an increased interest for disordered materials, e.g. with the discovery of multiple high capacity electrodes based on disordered rock-salt structures or even completely amorphous materials exhibiting higher capacities than their crystalline counterparts.[1] Furthermore, it was recently showed by Ceder et al that long-range order is not a prerequisite for maintaining percolating intercalation pathways.[2] Still very little is known about the structural mechanisms behind order-disorder transitions induced by ion-intercalation or about ion-storage mechanisms in disordered materials.  

Using a combination of operando synchrotron X-ray diffraction and total scattering (with pair distribution function analysis), we have studied a series of disordered and amorphous electrode materials such as nano-rutile TiO2, V2O5, and various MnOx-polymorphs.[4] This allows us to map out the structural evolution during battery charge and discharge at the atomic- and nano-scale, and begin to understand the ion-storage mechanisms in such materials. In this presentation, we will focus on results which demonstrate the different types of order-disorder phenomena (e.g. topotactic, reconstructive, domain size reduction) and ion-storage mechanisms (e.g. solid solution, two-phase transition) we have encountered.

1. J. Lee et al., Nature 2018, 556, 185-190.; E. Uchaker et al., J. Mater. Chem. A 2014, 2, 18208-18214.
2. J. Lee et al., Science 2014, 343, 519-522.
3. C. K. Christensen et al., Chem. Mater. (2019) DOI: 10.1021/acs.chemmater.8b04558.