Berlin 2024 – scientific programme
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 24: Focus Session: Battery Materials – Ion Transport, Impurity Effects and Modelling (joint session KFM/MM)
KFM 24.2: Talk
Thursday, March 21, 2024, 10:00–10:20, EMH 225
NASICON as solid electrolyte for Mg- and Ca-ion batteries — •Katharina Helmrecht1 and Axel Groß1,2 — 1Institute of Theoretical Chemistry, Ulm University, Ulm, Germany — 2Helmholtz-Institute Ulm (HIU) for Electrochemical Energy Storage, Ulm, Germany
In Na-ion batteries, NASICON has been used as a solid-electrolyte material. Here we present a density functional theory study in which we investigate whether NASICON can also be a suitable solid electrolyte for bivalent charge carriers such as Mg and Ca. We have in particular chosen Ca0.5Ti2(PO4)3, Ca0.5Zr2(PO4)3, Mg0.5Sn2(PO4)3, and Mg0.5Zr2(PO4)3 for our investigation. We find that these phases indeed show promise as solid electrolytes.
Unlike the classic NASICON phase, which often undergoes a phase transition from rhombohedral to monoclinic within the battery’s operating range, this issue does not arise with Ca and Mg. However, only half of the sites occupied by Na (specifically, the Na1 sites) become occupied by the bivalent carriers. We investigate the energetic ordering of the occupied positions inside and the diffusion mechanism inside the phase as well as bottleneck sizes and compare this to the classic NASICON phase.
Keywords: Density functional theory; Mg-ion battery; solid electrolyte