Convection-Diffusion Model of Lithium-Bismuth Liquid Metal Batteries

Abstract

The liquid metal battery is composed of two liquid metals with different electronegativity separated by molten salt. The three layers self-segregate based on density allowing for easy manufacturing and scaling. Lithium (Li) is one of the most widely researched anode materials, and when coupled with bismuth (Bi) cathodes, it gives a liquid metal battery that has an open circuit voltage of 0.9 V. Such a system has demonstrated impressive rate capabilities, ultra-long life cycle, and low energy cost. Here we present a two-dimensional physics-based model for Lithium-Bismuth liquid metal batteries. The model takes into account dynamical changes in the battery, including surface concentration and fluid flow. By solving the convection-diffusion equation in Bi electrodes, we are able to investigate the effect fluid flow on kinetic losses and concentration profiles in real time. The outcome of this work allows us to link electrochemistry and fluid dynamics in liquid metal batteries. Moreover, the model can also be used to guide future development of battery management systems.