Response Mode Engineering of ZnO@In2O3 Nanorods to Enable Single-Device H2/CO Discrimination for Early Warning of Lithium-Ion Battery Thermal Runaway

Rapid and reliable detection of early gas release is crucial for preventing thermal runaway (TR) in lithium-ion batteries (LIBs). Herein, we report a MEMS-integrated ZnO@In2O3 core- shell gas sensor that enables intrinsic single-device discrimination between H2 and CO, two key marker gases associated with early TR. Single-crystalline ZnO nanorods were directly grown on a MEMS microhotplate and conformally coated with 10-30 nm In2O3 shells. The optimized sensor with a 10 nm shell exhibits a stable p-type response to CO and a distinctive dynamic n-p response transition to H2 at 130 °C, allowing programmable dual-gas identification without sensor arrays. Coupled with a dynamic resistance-based early-warning algorithm, the device enables rapid and reliable detection of abnormal gas generation and triggers an alarm within 14 s of puncturing an overcharged swollen pouch cell. This work provides a compact, low-power, and intelligent sensing strategy for early warning of TR in LIBs.