Synergizing 3D-printed structure and sodiophilic interface enables highly efficient sodium metal anodes

Sodium (Na) metal batteries have gained increasing attention more recently, owing to their high energy densities and cost efficiencies, but are severely handicapped by the unsatisfactory Coulombic efficiency (CE) and cycling stability stemming from dendrite growth on Na anodes. In this study, we developed a strategy of direct ink writing (DIW) 3D printing combined with electroless deposition to construct a hierarchical Cu grid coated with a dense nanoscale Ag interfacial layer as the host material for Na plating. The sodiophilic Ag interface contributes to a fall in the Na nucleation energy, hence enabling uniform Na deposition on each 3D-printed filament. The constructed 3D-printed structure can effectively moderate the electric-field distribution and lower the local current density for relieving Na inhomogeneous growth, as confirmed by finite element simulation and Na plating/stripping morphology evolution results. In particular, the unique 3D structure also promotes the lateral growth of Na, thus the volume change of Na metal was accommodated to stabilize the solid electrolyte interphase (SEI). As a result, the CE of the half-cell can reach 99.9% at the current density of 1 mA/cm2 after 300 cycles and the full-cell exhibits outstanding electrochemical performance (capacity retention of 91.0% after 500 cycles at 2 C).