Effect of oxygen-vacancy modulation in tungsten oxide-based hydrogen sensor for lithium-ion battery thermal runaway monitoring

High-performance hydrogen sensors are critical for the safety monitoring of lithium-ion batteries. Here, WO_3-x thin films were fabricated by powder aerosol deposition, featuring an amorphous-matrix-encapsulated nanocrystalline structure. By systematically varying annealing atmospheres and temperatures, oxygen stoichiometry was tuned independently. Oxygen vacancies enhance surface reactivity and electron supply, while the microstructure governs the amplification of interfacial reactions into resistance changes. Their combined effect determines the sensing performance of Pd-WO_3-x hydrogen sensor. Vacuum annealing further confirms the performance enhancement induced by oxygen-vacancy engineering. The optimal sensor exhibits a wide detection range of 0.5 – 20,000 ppm H₂, a response exceeding 2 × 105 at 2 vol% H₂/air, and a fast response time of ≤0.4 s. These results demonstrate an effective strategy for developing high-performance WO_3-x-based hydrogen sensors and highlight the potential of PAD for tuning defect chemistry in metal-oxide sensing materials.