Abstract
Despite considerable worldwide efforts, safety issues due to thermal runaway (TR) still raise concerns for lithium-ion batteries (LIBs). Substantial efforts have been devoted to address TR due to thermal or mechanical abuse, relatively less investigations have been conducted for TR induced by slight overcharging cycling. This is partly due to the complexity and vast amount of interrelated information involved. Indeed, TR can be induced by slight overcharging due to inadequate design of battery management system (BMS) or unexpected malfunction of charger. The occurrence of TR from slight overcharge takes a lengthy incubation period, posing challenge for experimental investigations of either a single cell or cell clusters. Numerical study with validated models can potentially serve as a viable tool. In the present study, a coupled electrochemical and thermal model has been developed within the frame of open-source computational fluid dynamics (CFD) code OpenFOAM to capture the thermal runaway propagation (TRP) behavior induced by slight overcharging cycling in the cell cluster. Following validation with published single cell slight overcharge tests and TRP tests in a cell cluster, the model was used to simulate TRP in a 5 x 9 LIB cluster. Parametric studies were conducted to investigate the effect of different insulating materials between the cells and their thicknesses on mitigating TRP. This was followed by further numerical simulations to examine the effect of environment temperatures. The results will be analyzed to formulate recommendations to improve safety of LIB modules and packs.