Simulations of mass transport in liquid metal batteries
Liquid metal batteries (LMBs) are a promising candidate for storing electrical energy at the grid scale. An LMB is a fully molten electrochemical cell in which two liquid metal electrodes are separated by a molten salt electrolyte. With its simple chemistry and geometry, fully liquid state, and the occurrence of multi-physics phenomena, the LMB has become an intriguing candidate for continuum mechanics studies. This presentation primarily focuses on mass transfer within a liquid metal electrode. There, concentration inhomogeneities degrade cell efficiency, and most significantly, the alloying and de-alloying processes are the ones responsible for energy storage. The geometry of these electrodes is simple : a liquid alloy is confined by a flat electrochemically active interface and inert walls. During operation, a mass flux is established across the interface. The liquid alloy experiences either an enrichment or depletion of the electroactive species. This alters the local density distribution and can either cause or inhibit convective flows. We demonstrate how this explains the disparity in cell efficiency seen during charge and discharge experiments. We then delve into the study of the solutal convective flow. We use spectral-element simulations to explore the dynamics over an extensive parameter space. We identify and map two regimes of convection, analyse their time evolution, and present robust scaling laws for onset time, steady-state velocity, and concentration differences. We conclude by examining the role of mechanical coupling with the molten salt layer.
Contact Nathanaël Machicoane for more information or to schedule a discussion with the seminar speaker.