Joule Heating Shocked Ag-Loaded ZnO Nanofibers Assisted by Photo-Excitation Effect for ppb-Level H ₂ Sensors for Battery Safety Warning

Thermal-runaway-induced fire incidents remain a persistent challenge in electrochemical energy storage systems. While conventional battery management systems (BMSs) serve as primary diagnostic tools for battery anomalies, their inherent limitations in voltage/temperature anomaly detections during early stage thermal runaway always result in significant delays in capturing initial failure signatures of batteries. Hydrogen (H 2 ) generation is recognized as a precursor during the incipient phase of thermal runaway, since the low molecular weight (2.016 g/mol) of H 2 coupled with exceptional diffusivity (0.61 cm 2 /s at NTP) enables rapid permeation through battery enclosures and sensor barriers, providing inherent advantages for real-time monitoring. In this study, Ag-ZnO nanofibers were synthesized by combining the Joule heating with ultraviolet light excitation. Benefiting from the synergistic effects of Ag catalytic sensitization, dislocation defects induced by the Joule thermal shock, and photogenerated electrons from ultraviolet (UV) excitation, the fabricated H 2 sensor (J-ZA sensor) exhibits excellent performance, including a ppb-level detection limit, a fast response/recovery time (6/5 s), and a low operating temperature (180 °C). In addition, the J-ZA sensor successfully provides an early safety alert for practical pouch-type lithium cells, triggering 45.02 s prior to the onset of battery swelling, which demonstrates its strong promise for integration of advanced nanostructured sensors into next-generation battery safety management systems.