Experimental and numerical study on penetration-induced internal short-circuit of lithium-ion cell

•The mechanism of penetration-induced internal short-circuit of LIB is analyzed.•Penetration experiments, simulation, and separator thermal analysis are involved.•Two types of temperature rise modes are observed for thermal runaway case.•The Joule heat generated at short spot constitutes the most to the total heat. Nail penetration test is an abuse test method to evaluate the thermal hazard of lithium-ion battery. The internal short-circuit is a direct cause of battery thermal runaway, while its mechanism has not been fully understood yet. In this work, the penetration-induced internal short-circuit of lithium-ion cell is studied through nail penetration experiments, numerical simulation, and cell separator thermal analysis. The results show that the nail plays a dual role in the penetration process for thermal runaway or non-thermal runaway cases, which determines the short-circuit current and heat dissipation. In addition, there are two types of temperature rise modes for thermal runaway case, the time intervals from the beginning of penetration to thermal runaway of these two modes are less than 5 s and 60 s, respectively. It can also be concluded that the cell terminal voltage is found to decay exponentially with time after penetration, while the fluctuations and rebound of terminal voltage during the nail penetration process are attributed to the partially interrupted internal short-circuit path. The results indicate that the Joule heat generated at short spot dominates the total heat generation inside lithium-ion cell with non-thermal runaway nail penetration cases.