In Situ Thermal Runaway Detection in Lithium-Ion Batteries with an Integrated Internal Sensor

Thermal safety is of prime importance for any energy-storage system. For lithium-ion batteries (LIBs), numerous safety incidences have been roadblocks on the path toward realizing high-energy-density next-generation batteries. Solutions, viz. electrolyte additives, shut-off separators, and exotic coatings, have limited scope in their operating voltage window, response time, and performance. Various temperature monitoring devices have been tested out with their limitations. Here, we report in situ sensing of thermal signatures from the anode of a typical LIB using an internal resistance temperature detector (RTD). Solid electrolyte interface (SEI) comprised of ROCO2Li, (CH2OCO2Li)(2) and ROLi is formed on the surface of a graphite anode, and its decomposition releases enormous heat during thermal runway events. Sensing the temperature from the anode gives direct access to the heat liberated in thermal runaway, including SEI decomposition related heat generation. External short circuit (ESC) and overcharge tests were conducted to trigger the thermal runaway event, and temperature of 36.4 and 48.4 degrees C were recorded using internal RTDs, which were 9 and 20 degrees C higher than with external RTD, respectively. Interestingly, internal RTD has detection ability for 90% temperature rise 14 times faster than compared to the external RTD. Modeling of simulated tests explained the occurrence of different regimes during thermal runaway events initialed by ESC and overcharge. Furthermore, multimode calorimetry (MMC) for LIB with internal RTD yielded more endothermic peaks beyond 150 degrees C due to the presence of three-dimensional (3D)-printed polylactic acid (PLA) support. Overall 1.75 kJ g(-1) of generated heat was measured using MMC, which is significantly lower than LIB without an RTD sensor. The RTD-embedded assembly acts as a passive safety device while stationed inside the battery. Using thermal signatures from RTD, an advanced battery management system can lead to a conducive LIB, which would be a safer powerhouse for high-energy-density applications such as in the automotive industry and high-energy grid storage.