Operando Monitoring of Electrode Temperatures During Overcharge-Caused Thermal Runaway

Lithium-ion batteries' (LIBs) failure due to abusive cycling conditions can result in thermal runaway, which calls for reliable real-time battery thermal safety monitoring. Herein, an effective method for LIB thermal runaway detection using a resistant temperature detector (RTD) is compared with a conventional battery surface temperature measurement. A direct electrode temperature measurement technique based on additive manufacturing-enabled application of miniature RTDs for measurement of internal temperature within large-capacity Li-ion pouch cells is used. The miniature RTDs are embedded in a customized electrochemically inactive polymeric substrate for real-time thermal safety monitoring during overcharge abuse. Electrode temperature profiles under different conditions of overcharge (at 1 and 5 C rate, charged until battery explosion) are analyzed and mechanisms of heat generation in LIBs during overcharge-induced thermal runaway are investigated. The internal RTDs detect the onset temperature of the solid-electrolyte interface decomposition approximate to 10 s earlier than the sensors attached to the battery surface. A maximum temperature gradient of approximate to 200 degrees C is observed between the electrode and the battery surface during overcharge-induced thermal runaway. The internal RTDs are shown as a possible guide for sensor placement location to capture the maximum temperature within the LIBs during abuse events.