Sodium Deposition with a Controlled Location and Orientation for Dendrite-Free Sodium Metal Batteries

Sodium is one of the most promising alternatives to lithium as an anode material for next-generation batteries. However, severe Na dendrite growth hinders its practical implementation. Here, a polyacrylonitrile (PAN) fiber film coated with a thin layer of tin on the bottom side (closing to battery case) serves as a scaffold for Na deposition. Due to the low nucleation barrier enabled by the Sn layer, Na deposition spontaneously occurs at the bottom of the scaffold, and then is homogeneously confined within its 3D network because of the decreased local current density caused by 3D structure and uniform Na⁺ distribution regulated by the sodiophilic PAN. With this well-controlled orientation of Na deposition, the Na-PAN/Sn electrode delivers a high Coulombic efficiency of 99.5% in Na plating/stripping at 5 mA cm⁻², stable operation for over 2500 h in symmetric batteries at 2 mA cm⁻², and excellent cyclic stability and rate capability in Na metal full batteries.