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 (H 2 ), is crucial for early warning of thermal runaway. However, conventional semiconductor metal oxide sensors often exhibit limited H 2 sensitivity due to the weak interactions between H 2 molecules and metal oxide surfaces. In this work, we present an innovative strategy to enhance trace-level H 2 detection by modifying SnO/Sn 2 O 3 with palladium (Pd) sensitizers. The optimized 1 wt % Pd-doped SnO/Sn 2 O 3 demonstrates remarkable sensitivity, achieving a high response ( R a / R g = 25) to 50 ppm H 2 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 Sn 2 O 3, (ii) the Pd-induced spillover effect enhancing oxygen adsorption, and (iii) well-defined metal-metal oxide and heterojunction interfaces. These features enable exceptional trace H 2 detection, positioning the proposed sensor as a promising candidate for real-time safety monitoring in lithium-ion batteries.