Differently Modified ZnO Monolayers as Key Gas Sensors for Lithium-Ion Thermal Runaway: A DFT Study

To address the demand for rapid detection of toxic gases (C 2 H 2, C 2 H 4, CH 4 and H 2 ) released during lithium-ion batteries (LIBs) thermal runaway, this study uses first-principles calculations to investigate adsorption behavior. First, two modification methods are considered, namely surface doping of pure ZnO (TM-ZnO) and defect doping containing Zn vacancies (TM D -ZnO). And the stable structures of transition metals (TM = Ir, Os, W, and Pt) under two modifications were explored. The calculation results show that the geometric structure of TM D -ZnO is relatively stable. Subsequently, the different adsorption structures of C 2 H 2, C 2 H 4, CH 4, and H 2 on the two doped structures were studied, and the adsorption properties of the stable adsorption structures were calculated. The results indicate that chemical adsorption of C 2 H 2 and C 2 H 4 was observed in the two doped systems respectively, while the adsorption performance in the TM-ZnO system is the strongest. Furthermore, the W–ZnO/H 2 system has an E ad of −0.82 eV, and there is an interaction of a certain strength between molecules, which is mainly chemical adsorption. Finally, the sensing properties of gas molecules on TM-ZnO and TM D -ZnO were evaluated. The results show that the bandgap width of the W–ZnO/C 2 H 4, Pt D -ZnO/C 2 H 2, and Pt D -ZnO/C 2 H 4 systems decreases, and good desorption can be achieved within an appropriate time after heating. Meanwhile, the bandgap width of the W–ZnO/H 2, Ir D -ZnO/CH 4, and Ir D -ZnO/H 2 systems changes significantly, with recovery times at room temperature of 7.55 × 10 1, 6.14 × 10 –2, and 2.32 × 10 –2 s, respectively. This makes them potential reusable gas-sensing elements for CH 4 and H 2 detection. This work demonstrates that metal-modified ZnO is a potential material for harmful gas monitoring.