Ultrasensitive Hydrogen Sensor Based on a Non-Stoichiometric Tin Oxide Heterojunction for LIB Thermal Runaway Early Monitoring.

Real-time detection of characteristic gases, particularly hydrogen (H2), is crucial for early warning of thermal runaway. However, conventional semiconductor metal oxide sensors often exhibit limited H2 sensitivity due to the weak interactions between H2 molecules and metal oxide surfaces. In this work, we present an innovative strategy to enhance trace-level H2 detection by modifying SnO/Sn2O3 with palladium (Pd) sensitizers. The optimized 1 wt % Pd-doped SnO/Sn2O3 demonstrates remarkable sensitivity, achieving a high response (Ra/Rg = 25) to 50 ppm H2 at 180 °C with an ultralow theoretical detection limit of 0.35 ppb. In a practical validation using a commercial lithium-ion pack, this sensor delivered a thermal runaway approximately 28 min earlier than conventional battery management systems. The enhanced sensing performance stems from synergistic effects: (i) abundant defects in non-stoichiometric SnO and Sn2O3, (ii) the Pd-induced spillover effect enhancing oxygen adsorption, and (iii) well-defined metal-metal oxide and heterojunction interfaces. These features enable exceptional trace H2 detection, positioning the proposed sensor as a promising candidate for real-time safety monitoring in lithium-ion batteries.