A Novel Benchmarking Approach to Assess Fire Safety of Liquid Electrolytes in Lithium‐Ion Batteries

Abstract Establishing authoritative electrolyte safety assessment methods at laboratory levels is crucial for addressing conflicts from thermal runaway of lithium‐ion batteries. However, self‐extinguishing time (SET), as the most widely used evaluation method now, lacks benchmarks and heavily relies on the specific implementation of test procedures. This work systematically summarizes and investigates key test parameters. Based on repeatability and reliability, burning a glassfiber separator (Φ16 mm) with absorption of 0.1 g liquid electrolyte (LE) can be proposed as a unified method. The concept of self‐extinguishing efficiency (SEE) is further proposed with a new evaluation criterion of i) SEE≤70, Flammable; ii) 70<SEE<90, Flame Retarded; iii) 90≤SEE≤100, Nonflammable. The feasibility of the new protocol is verified by employment in evaluating the effects of 15 representative flame retardants (FRs) on combustion behaviors of LEs. Meanwhile, the underlying flame retardancy mechanism is revealed, indicating that preceding or simultaneous vaporization and pyrolysis of FRs in conjunction with the decomposition of LE promote mitigating electrolyte fire risk. In addition, machine learning is employed to aid in analyzing the significance of various features on SEE, providing further validation of the proposed mechanism. This work provides a benchmark for the safety evaluation of LEs, facilitating the advancement of fire‐safe batteries.