A new method of thermal runaway warning for lithium-ion batteries using the swelling force

Abstract The thermal runaway process of a battery is accompanied by changes in the characteristic parameters, including the battery voltage, temperature, internal resistance, gas, smoke, and swelling force, which provide many options for the early warning of battery thermal runaway. Among the various feasible warning methods for thermal runaway, the method of swelling force may have distinct advantages in advance warning and warning reliability. In this paper, commercial lithium iron phosphate/graphite and ternary/graphite batteries were used as the research objects. The patterns of the change of the swelling force with voltage, temperature, and other parameters were compared, and the results showed that the change of the swelling force during thermal runaway was higher than that during normal charging and discharging. Moreover, the time when the change of the swelling force in the thermal runaway process exceeded the change under normal working conditions was earlier, so an earlier warning could be achieved. In addition, compared with the temperature signal, the collection of the swelling force signal was more convenient. In summary, this paper provides a feasible and fast method for the early warning of battery thermal runaway, which has high engineering significance for improving the safety of electric vehicles.