Interaction of fluid flow with heat and mass transfer in Liquid Metal Batteries

Liquid metal batteries (LMBs) are suggested as a possible solution of the energy storage problem. An LMB consists of three stably stratified layers, two liquid metals are separated by a molten salt electrolyte.
Operation was so far demonstrated for small prototypes only. In order to upscale cells to a viable commercial scale a deep knowledge of the physics involved is required.
The relatively simple chemistry and geometry, the presence of multiple and multi-physics phenomena and the completely fluid nature of the active materials have made the LMB an intriguing candidate for continuum mechanics studies.
The cell is in fact subject to a coexistent transport of mass, heat, charge and momentum together with chemical and electrochemical reactions.
The fluid flow that naturally occur can be beneficial if it is able to improve the mass transport, delaying the formation of solid intermetallic phases.
In our work the attention is focused on heat and mass transfer. The continuum balances are defined in general terms, taking into account the electrochemical nature of the system. The corresponding scalar fields (e.g. temperature and solute concentration) are then computed with pure diffusive models. In a second step the interaction with the induced fluid flow is taken into account. Thermal convection in Li||Bi LMBs is studied with an improved version of the multiphase VOF solver multiphaseInterFOAM. Advection-diffusion mass transfer is investigated in the positive electrode with single-phase CFD solvers.
The first results of thermo-solutal convection are presented, the modeling limits and the future development are discussed.