Tuning charge transfer and ion diffusion in 3D nanotubular arrays by engineering vacancy and implanting sodiophilic seeds for dendrite-free sodium metal anodes

Sodium metal anode (SMA) stands out as a compelling choice for future high-energy Na batteries due to its high theoretical capacity and low redox potential. However, its widespread application is severely impeded by dendrite-related hazards. Designing a host for “hostless” SMA has emerged as a promising strategy to address its harmful dendrite growth. Recent studies highlight the effectiveness of low-tortuosity arrays in SMA for guiding rapid ion transport and achieving uniform Na deposition. Herein, a pioneering 3D host, Ag@H-TNTA, characterized by low-tortuosity hydrogenated TiO_2-x nanotubular arrays decorated with silver nanocrystals, are unveiled for constructing fast, stable, and dendrite-free SMA. The strategic introduction of oxygen vacancies and the implantation of sodiophilic seeds enable the achievement of rapid and coordinated electronic/ion transport as well as uniform electric-field/ion flux distribution in the Ag@H-TNTA, ultimately facilitating uniform Na deposition. Consequently, Ag@H-TNTA electrode exhibits a dendrite-free plating morphology and maintains an impressive Coulombic efficiency of ≈ 98% over 600 cycles at 1 mA cm⁻² with a capacity of 1 mAh cm⁻². Outstanding cycling performances and high rate capabilities of Ag@H-TNTA-Na anode are also demonstrated in both symmetric and full cells, underscoring the potential of Ag@H-TNTA as a robust host for stable and dendrite-free SMA.