Numerical study on thermal characteristics under external short circuit for Li||Bi liquid metal batteries

Abstract

As one of the most potent battery technology, liquid metal battery (LMB) plays an important role in addressing the requirement of grid energy storage. However, up to now, few attention has been paid to the heat generation characteristics and thermal safety of LMB, including the conventional and abusive conditions. In this paper, a 2D axisymmetric multi-physics field model coupling electrochemistry, heat transfer, and laminar flow is proposed to evaluate the electro-thermal behavior of 200 Ah Li||Bi LMBs under the states of constant current (CC) cycle and external short circuit (ESC). Verified by the experimental data, the maximum fitting errors of the voltage and temperature are 4.61% and 0.42%, respectively. The reversible and irreversible electrochemical heat generation rates are calculated to assess the total heat power (9.14 W during 0.2 C discharge and −5.06 W during 0.2 C charge). The reversible heat rate is found to occupy a large proportion in the total heat generation, while the percentage of irreversible heat is shown to increase with the increasing current rate. Based on the analysis of CC cycle, the model is applied to investigate the battery electro-thermal performance in ESC failure. The results show that the ESC current and surface temperature vary with the short-circuit resistance and initial state of charge (SOC). The lower ESC resistance and initial SOC may lead to a severer temperature rise due to the unique entropic heat behavior. The maximum current and temperature reach 455.8 A and 549.3 °C in 5 min (100% SOC, 0.1 mΩ). This work provides an important opportunity to advance the understanding of heat generation and abuse phenomena induced by ESC in LMB.