Formation of a stable LiF-rich SEI layer on molybdenum-based MXene electrodes for enhanced lithium metal batteries

Lithium metal batteries are considered highly promising candidates for the next-generation high-energy storage system. However, the growth of lithium dendrites significantly hinders their advance, particularly under high current densities, due to the formation of unstable solid electrolyte interphase (SEI) layers. In this study, we demonstrate that molybdenum-based MXenes, including Mo₂CT_x, Mo₂TiC₂T_x, and Mo₂Ti₂C₃Tx, form more stable LiF/Li₂CO₃ SEI layers during lithium plating, compared to the conventional Cu electrode. Among these, the bimetallic Mo₂Ti₂C₃T_x MXene, with its higher fluorine terminations, produces the most stable LiF-rich SEI layer. The formation of this stable inorganic SEI layer significantly reduces the nucleation overpotential for lithium deposition, promotes uniform Li deposition, and suppresses dendrite growth. Consequently, the Mo₂Ti₂C₃T_x substrate achieved prolonged cycling stability of approximately 544 cycles with coulombic efficiency of ~99.79% at high current density of 3 mA cm^-2 and capacity of 1 mAh cm^-2. In full cells, the Mo₂Ti₂C₃T_x anode, paired with an NCM622 cathode, maintained capacity retention of 70% over 100 cycles with high cathode loading of 10 mg cm^-2. Our approach highlights the potential of Mo-based MXenes to improve the performance of lithium metal batteries, making them promising candidates for the next-generation energy storage system.