Multiphysics Modeling of Safety and Electrolyte Stability in Sodium-Based Liquid Metal Batteries

Grid-scale long-duration energy storage requires electrochemical systems that remain safe under thermal and mechanical abuse. Liquid metal batteries promise long life, yet interfacial thinning can trigger short circuits and is rarely quantified. Here we couple electrochemistry, heat transfer, magnetohydrodynamics and phase-field interface tracking to model a 200 Ah sodium-based liquid metal battery and define safety by the minimum electrolyte thickness. At 380 °C the cell rapidly settles to a ~0.697 V plateau while temperature and circulation develop on ~10^2 s timescales. During a four-stage ambient over-temperature cycle, internal temperature peaks during external cooling with a 28.04 K rise, whereas voltage variations remain <1 mV. Effective tilt from 5° to 20° leaves the voltage unchanged but strengthens the return-flow, and 50 Hz vertical vibration for 2 s reduces the minimum electrolyte thickness from 10.0 to ~9.55 mm. These results enable disturbance-to-margin safety envelopes for design and operation.