Simulations of Transport Phenomena in Liquid Metal Batteries


Simulations of Transport Phenomena in Liquid Metal Batteries

Personnettaz, P.

Liquid metal electrodes are an essential component of liquid metal batteries. The use of a liquid phase is critical for scalability, long lifetime, and high cyclability. These electrodes have a simple geometry: a liquid metal alloy is confined by an electrochemically active interface and inert walls. A mass flux is enforced at the active interface during cell operation. The liquid metal alloy experiences a local enrichment or depletion of the electroactive species. This alters the buoyancy distribution and either induces or suppresses convective flows. The quantitative analysis of an amperostatic experiment allows us to highlight the influence of this phenomenon on the cell voltage during charge and discharge. The charging step of a liquid metal battery's positive electrode is then discussed. The electroactive species (e.g., Li) is electro-refined from the alloy (e.g., Li(in Pb)), and the heavy alloy obtained at the top interface sinks down, resulting in a powerful solutal flow. The evolution of the concentration and velocity fields in 2D-axisymmetric
and 3D-cylindrical electrodes is investigated using numerical methods. Two regimes of solutal convection are recognized as a function of the Rayleigh number. We establish robust scalings for velocity and concentration differences as a function of the current density and the electrode properties. Finally, the effects of solutal convection on heat transport and mechanical coupling with the molten salt layer are highlighted.

Keywords: liquid metal battery; solutal convection; liquid metal electrode; mass transport

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Publ.-Id: 35342