UC San Diego

In recent years, as the automotive industry is shifting towards electric vehicles (EVs), lithium-ion battery (LIB) has attracted increasing attention for its high energy density, relatively long cycle life, and relatively low cost per kW-h. In a LIB cell, under normal operating condition, the polymer membrane separator hosts the electrolyte for lithium ion transport between the anode and the cathode, while blocking the internal electron transport. However, such a membrane structure is point sensitive and may be damaged under extreme conditions, leading to internal shorting and thermal runway.

To mitigate thermal runaway of LIB cells, robust composite electrodes with either cracking/debonding initiation (CDI) additives or thermally sensitive binders (TSBs) were systematically investigated. Both of the thermal-runaway mitigation (TRM) mechanisms were integrated into the active electrode layer. When a battery was internally shorted, TRM process was activated, which disintegrated the components of electrode and limited the discharge current and Joule heating rate, preventing the cell from reaching the onset temperature of thermal runaway. The CDI was triggered mechanically, and the TSB was triggered thermally.

The testing results suggested that TSB was more effective than CDI; it reduced the peak temperature increase in a damaged LIB cell by approximately 50%. The triggering temperature was around 100 oC, conservatively lower than the onset of thermal runaway. The TSB mechanism was also tested for compatibility with high-energy battery chemistries and demonstrated promising results.