Compositional convection in liquid metal electrodes


Compositional convection in liquid metal electrodes

Personnettaz, P.; Klopper, T. S.; Benard, S.; Kubeil, C.; Landgraf, S.; Weber, N.; Weier, T.

Liquid metal electrodes are a crucial element of innovative electrochemical cells such as
liquid metal batteries (LMBs) and solutal - alkali metal thermal electric converters (S-AMTECs).
The liquid phase is a key to guarantee scalability, extended life time and high cyclability; at the same
time fluid mechanics plays a pivotal role in terms of cell capacity and efficiency. The geometry
of these electrodes is simple: a liquid metal alloy is confined by an electrochemically active interface
and inert walls. The active interface can be fluid (molten salt electrolyte) or solid (fast ionic
conductor). During operation of the cell a mass flux is established across the interface. The liquid
metal alloy experiences an enrichment or depletion of the electroactive species. This changes the
local density distribution and either induces or suppresses convective flows. Here, we focus
on the positive electrode of a liquid metal battery during the charging step. The electroactive species
(e.g. Li) is extracted from the alloy (e.g. Li(in Bi)), and the heavy alloy generated at the top interface
sinks down leading to strong compositional convection. The evolution of the concentration and
velocity fields are studied with numerical methods; the results of a finite volume code (OpenFOAM)
are compared with the ones of a spectral element code (SEMTEX). The effects of Schmidt number,
current density magnitude and distribution and electrode geometry are investigated. Furthermore,
the impact of a non-uniform temperature distribution and the mechanical coupling with a molten
salt layer are discussed.

Keywords: LMB; S-AMTEC; mass transport; solutal convection

  • Lecture (Conference) (Online presentation)
    IV Russian Conference on Magnetohydrodynamics, 20.-22.09.2021, Perm, Russia

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Publ.-Id: 33042