A U.S. renewable energy manufacturer needed to evaluate a sodium-ion battery cell’s thermal behavior under conditions that closely mimic real-world thermal confinement, such as those found inside battery packs or battery energy storage systems (BESS). Failure of these batteries could result in performance and safety concerns, such as capacity fade, overheating, release of toxic gases, and even fire.
The ioKinetic team measured sodium-ion battery safety by simulating normal and worst-case operating conditions safely under laboratory conditions using an EVx Battery tester and calorimeter. Two calorimetric tests were carried out.
Table 1 - Details of the batteries tested
This test helped determine the onset temperature of the reaction and internal short circuit. An Accelerating Rate Calorimeter (ARC®) test includes a heat-wait-search which heats the cell and then waits for a period to allow an exotherm detection. Battery “heat-wait-search” tests are conducted to gather information about the temperature at which a battery becomes hazardous (thermal runaway or an energy release occurs), the amount of thermal energy released runaway, and the time required for complete decomposition. These tests simulate a worst-case scenario which is an adiabatic environment, similar to the conditions experienced by a cell in the middle of a large battery pack or in a well-insulated system for transportation where heat cannot dissipate into the surroundings.
By analyzing the thermal data obtained from these tests, knowledge of the average specific heat capacity of the battery allows for converting a temperature rise into thermal energy. In this case, the specific heat capacity of the cells can be assumed from the literature. However, to get a more accurate value for the specific heat capacity of each cell, we also recommended conducting a heat capacity test. This data should be obtained for modelling and safety analysis purposes. We also recommended a Battery Hazard Analysis (BHA) to help them identify the safeguards and other mitigation strategies to reduce the risk of a thermal runaway event at battery installations.
The primary data obtained from this type of test are the battery surface temperature, the energy released during decomposition and short circuit, and the vented gas temperature when using a closed test, which is monitored to determine the self-heating rate of the cell against temperature. Cell voltage data can also be collected when using a closed test.
We delivered critical insights to the client on the thermal runaway and fire potential of the sodium-ion batteries. Through ARC® testing, the team determined the onset temperature of the reaction and internal short circuit. The data was essential for developing appropriate risk mitigation strategies to ensure the safe operation of their BESS facilities.