Testing Lithium Batteries to Destruction
Conducting abuse testing on lithium-ion batteries for automotive applications for upcoming electric vehicles to determine their safety characteristics with Jaguar Land Rover and WMG.
Calorimetry testing uses temperature to study or measure properties of materials. The aim is was to obtain time-temperature-pressure data about test samples.
Two types of tests were conducted: heat-wait-seek (HWS) and overcharge tests. These were conducted at different states of charge (SOC) inside and outside the calorimeter at the cell level.
For this project, an Accelerated Rate Calorimeter (ARC) was used.
The lithium cell itself was suspended from a copper rod that was free to rotate inside the chamber. Aluminium tape with high grade adhesive was chosen to ensure it would cope with the temperatures inside the chamber. It was also used to attach the thermocouples to the cell surface. The ARC thermocouple along with one from the Maccor were taped to middle of the front surface. Another Maccor thermocouple was taped to the middle of the back surface, totalling three thermocouples.
Conducting the experiments
A total of 21 experiments were conducted for the dissertation. The data sets were analysed and appropriate visuals were created to better understand the failure pathway and draw conclusions. The HWS tests suggested that failure time for low SOC cells was shorter compared to high SOC cells.
The results from the overcharge tests spawned another undergraduate project conducted for Jaguar Land Rover for 2016-17.