Divergent Mechanisms of Elemental Doping in Sodium Titanate Anodes for Enhanced Performance

Elemental doping is widely employed to enhance the performance of sodium titanate (Na 2 Ti 3 O 7 ) as an anode material for sodium-ion batteries (SIBs). However, the underlying microscopic mechanisms of how various dopants alter Na 2 Ti 3 O 7 remain elusive. Herein, we reveal distinct modification mechanisms for d-block transition metals and f-block lanthanide metals via theoretical simulations. The results indicate that d-block metals enhance electronic conductivity by modulating the metal–oxygen electronic structure and facilitating the formation of shallow-level defects within the bandgap to improve carrier conversion efficiency, which is closely related to their atomic number. In contrast, f-block metals improve ionic mobility by tailoring the crystalline structure and expanding interlayer migration channels, thereby lowering the migration-energy barrier. The average 1D barrier of tested f-metal-doped Na 2 Ti 3 O 7 is 0.45 eV. This study elucidates, for the first time, the divergent mechanisms of various metal dopants in overcoming the intrinsic limitations of sodium titanate, providing a robust theoretical foundation for the advanced design of SIB anodes.