The gas-sensitive properties of Ti2CO2 MXene modified by transition metals (Ir and Rh) in relation to lithium-ion thermal runaway gases: a first-principles study.

With the rapid development of energy storage and power batteries, thermal runaway of lithium-ion batteries (LIBs) poses serious safety risks. Accurate detection and early warning of thermal runaway gases are of great significance for safety protection. Thus, the adsorption behaviors of three typical thermal runaway gases of LIBs (CO, CO2, and C2H2) on the surfaces of pristine Ti2CO2, oxygen-vacant Ti2CO2, TM@Ti2CO2, and TM-Ti2CO2 (TM = Ir and Rh) were investigated based on density functional theory (DFT). By analyzing the adsorption energy, charge transfer, charge density difference, band structure, density of states, work function, and recovery time, the results indicate that both oxygen vacancy and transition metal modification can narrow the band gap of Ti2CO2 and enhance its interaction with characteristic gases. Ir@Ti2CO2 presents the strongest adsorption for CO and C2H2 with difficult desorption at room temperature, making it a favorable adsorbent. At 398 K, Rh-Ti2CO2 exhibits a desirable desorption time and reversible sensing capability for C2H2, which is suitable for C2H2 gas sensing. Moreover, biaxial positive strain can enhance the CO2 adsorption of Ir@Ti2CO2, with the best performance at +2% strain. This work provides a theoretical basis for developing Ti2CO2 gas sensors and adsorbents applied to the thermal runaway gas monitoring of LIBs.