Fe-X (X=C, P, S) atom pair-decorated g-CN monolayers for sensing toxic thermal runaway gases in lithium-ion batteries: A DFT Study.

The thermal runaway of lithium-ion batteries (LIBs) releases a mixture of toxic and explosive gases, posing severe safety risks. High-performance sensors are critical for the early detection of these thermal runaway gases (TRGs) to prevent accident escalation. Herein, we systematically investigate Fe-X (X = C, P, S) atomic pair-modified g-CN (FCN, FPN, FSN) monolayers as potential sensing materials for six TRGs (CO, CO, H, CH, CH, and CH) using first-principles calculations. The results demonstrate that the Fe-X pairs can be stably anchored onto the g-CN monolayer, and this co-doping strategy significantly enhances its adsorption and sensing capabilities. Furthermore, the key TRGs such as CO, CH, and CH undergo strong chemisorption, inducing substantial changes in the electronic properties of the modified monolayers and signifying excellent sensing potential. Notably, the materials exhibit tailored functionalities; for instance, FCN and FSN are identified as promising candidates for reusable, room-temperature (298 K) H detection due to their fast desorption performance. This study underscores that atomic pair co-doping is a powerful approach to design g-CN-based materials with high sensitivity and selectivity, offering a theoretical foundation for the development of advanced sensors for LIBs safety monitoring.