Abstract: We recently proposed two atomic structures of the Al2CuLi (T1) phase using first-principles density functional theory calculations. Here, we find that both the previously proposed T1 phases (Al6Cu4Li3, Al13Cu7Li6) are predicted using X-ray absorption fine structure (XAFS) spectroscopy. It is found that the semi-coherent T1/Al interface of two T1 phases shows approximately 0.70 J/m2 with Al-Li termination at interface. Thus, there is a coexistence of both T1 phases in Al-Cu-Li alloys based on our computations. It is also found that the T1 formation is controlled by Ag and Mg solute segregations at interface over Cu/Li ratio based on bulk thermodynamics.