Orchestrating Sodium Deposition and SEI Passivation via Bifunctional Mo 2 TiC 2 T x MXene for High‐Efficiency Anode‐Free Sodium Batteries

ABSTRACT The operational instability of anode‐free sodium metal batteries (AFSMBs), stemming from uncontrolled sodium dendrite growth and unstable solid electrolyte interphase (SEI) formation, presents a formidable barrier to their commercialization. Herein, we address these critical bottlenecks by employing a bimetallic MXene (Mo 2 TiC 2 T x ) as a dual‐functional interfacial modifier on planar copper current collectors. Unlike conventional single‐metal MXenes, Mo 2 TiC 2 T x exploits the synergistic electronic interaction between Mo and Ti to create a highly sodiophilic surface, drastically reducing the nucleation overpotential and guiding a lateral, spherical growth mode of sodium that precludes dendritic protrusions. Beyond physical nucleation control, the unique surface chemistry of Mo 2 TiC 2 T x actively modulates the solvation/decomposition pathway of the electrolyte, fostering an ultrathin SEI that is predominantly composed of highly ion‐conductive NaF and Na 2 O nanocrystallites. This electrochemically robust interface ensures rapid Na + desolvation and transport, as confirmed by a six‐fold increase in the Na + diffusion coefficient compared to conventional MXenes. Benefiting from this synergistic orchestration of bulk deposition and interfacial chemistry, the Mo 2 TiC 2 T x @Cu electrode achieves an unparalleled cycling longevity of over 1400 hours and a high average Coulombic efficiency of 99.61%. When paired with a Na 3 V 2 (PO 4 ) 3 cathode, the full cell demonstrates outstanding capacity retention over 600 cycles. This work underscores the critical role of bimetallic MXenes in engineering both the nucleation thermodynamics and SEI formation kinetics, offering a transformative strategy for developing durable and energy‐dense AFSMBs.