An automatic identification method of thermal physical parameter for lithium-ion batteries suffering from thermal runaway

The thermal physical parameters change largely after a battery undergoes failure. The battery venting during thermal runaway causes the loss of battery materials, resulting in changes of thermal physical parameters such as density, heat capacity and thermal conductivity, thereby affecting the safety modelling and design for an energy storage battery system. This paper proposes a method for automatically identifying the thermal physical parameters of battery materials before and after thermal runaway exposure. A scheme of automatic parameter identification for lithium-ion batteries was established relying on model based optimization algorithm. Specific experiments were designed to match the data input requirement of automatic parameter identification scheme. The cell and its wreckage after thermal runaway were heated in a calorimetry chamber with temperature measured. The thermal physical parameters of the cell wreckage were identified by the proposed model-based optimization scheme. The results demonstrate that the thermal physical parameters of the battery change greatly before and after thermal runaway, significantly affecting the behavior of thermal runaway propagation within a battery pack. Therefore, the changes in the thermal physical parameters should be considered in thermal runaway modelling for battery pack design.