Composite A2M6O13 anodes (A = Li, Na; M = Ti, Zr) for Li-Na dual cation batteries: a theoretical investigation.

The development of advanced anode materials is critical for improving the efficiency and durability of alkali-ion batteries. In this study, large-scale molecular dynamics simulations are employed to investigate the transport properties of A2M6O13 (A = Li, Na; M = Ti, Zr) compounds in mono-, bi-crystalline and composite forms. Grain boundaries exert a decisive influence on ion migration in enhancing Na+ mobility in bi-Na2Zr6O13 but slightly restrict transport in bi-Na2Ti6O13. Composite architectures integrating both Li- and Na-based phases (Li2Zr6O13@Na2Ti6O13, LZNTO; Li2Ti6O13@Na2Zr6O13, LTNZO) exhibit superior conductivity compared to Na-only counterparts, underscoring the higher intrinsic mobility of Li+ ions. Population-weighted mean square displacement analysis confirms that effective diffusivity and conductivity in dual-cation composites are mathematically equivalent to the sum of species-resolved contributions, thereby capturing simultaneous transport effects. Of the studied systems, Na2Ti6O13 demonstrates excellent Na+ transport with the lowest activation energy, while Li-containing composites achieve moderate conductivity through synergistic Li+/Na+ migration. These findings provide evidence of synchronized transport in dual-cation titanate/zirconate composites, establishing LZNTO and LTNZO as promising anode candidates for next generation Li-Na dual-cation battery systems.