Early Detection of Thermal Runaway Gases in Lithium-Ion Batteries Using Transition Metal (Ti, Zr)-Decorated Graphene Quantum Dots

Early detection of thermal runaway gases is crucial for ensuring the safety of lithium-ion batteries (LIBs). In this study, we have designed and evaluated a graphene quantum dot (GQD) system composed of a divacancy doped with four pyridinic nitrogen atoms (DV/4N) and further decorated with transition metals (TM = Ti, Zr). We have systematically investigated the adsorption and sensing mechanisms of the TM@DV/4N system toward six key thermal runaway gases associated with LIB, i.e., C₂H₂, C₂H₄, CH₄, CO, CO₂, and H₂, employing the density functional theory (DFT). Our analysis of adsorption energy, charge transfer, frontier molecular orbitals, and density of states reveals distinct adsorption behaviors. Additionally, the variation in work function, sensitivity, and desorption time provides insights into the sensing performance of the system. Furthermore, quantum theory of atoms in molecules (QTAIM) and electron localization function (ELF) analyses have been employed to confirm the nature of bonding and the strength of interactions. Our study has proposed Ti@DV/4N and Zr@DV/4N as promising gas-sensing materials, each with unique characteristics. Ti@DV/4N surface show improved performance in the detection of specific gases, such as C₂H₂. However, Zr@DV/4N offers greater selectivity and sensitivity, making it effective as a disposable sensor and a safety-enhancing component in LIB systems. Hence, TM@DV/4N would act as next-generation gas-sensing materials, promoting safer, greener, and more efficient energy storage solutions.