Ionic Gel Chemical Sensors with Damage Tolerance for Monitoring Lithium‐ion Battery Electrolyte Leakage and Battery Safety

Abstract Given the frequent occurrence of lithium‐ion battery (LIB) incidents, gas sensors monitoring LIB safety are imperative yet deficient. Here, a new class of LIB electrolyte sensors based on ionic gels is presented, in which ions instead of electrons act as charge carriers and interact with analyte molecules for improved sensitivity. The ionic gels are readily synthesized through the photopolymerization of ionic liquids (ILs) incorporating C═C bonds with structurally analogous ILs devoid of C═C bonds. Through systematic investigation, PF 6 − is identified as the optimal ion carrier for LIB electrolyte sensing. Trace amounts of LIB electrolyte (20 nL) leakage can be detected within seconds. Interestingly, the devices exhibit decent damage tolerance. More importantly, multiple sensors with decent consistency can be batch‐fabricated on a large scale, which is essential for practical applications. Remarkably, the devices exhibit an extended operational lifespan, endowing them with significant potential for long‐term safety monitoring. The sensors are integrated into a monitoring system and demonstrate exceptional capability in differentiating the various stages of LIB thermal runaway, which paves the way for their potential applications in power storage stations and electric vehicles.