Heterogeneous Cations Enable Crystallographic Regulation of Na Deposition toward Dendrite-Free Sodium Metal Batteries

Sodium metal batteries have great promise for next-generation energy storage but face fundamental challenges of dendritic growth and interfacial instability. Herein, a gel polymer electrolyte incorporating multifunctional rubidium carbonate (Rb2CO3) additive is proposed (GPE+R) to stabilize the electrolyte–electrode interface and induce uniform Na deposition. Through optimal geometric matching and surface energy anisotropy, Rb+ cations preferentially adsorb onto the Na(200) plane, creating an electrostatic shielding effect that redirects planar Na deposition toward the closest-packed (110) plane. Simultaneously, Rb+ can also participate in competitive solvation with Na+, modifying the solvation structure and reducing the Na+ desolvation barrier. Consequently, the modified electrolyte enables dendrite-free Na deposition and 96.2% capacity retention after 4000 cycles in Na3V2(PO4)3||GPE+R||Na cells. The practical viability and mechanical flexibility are further verified by the operation of NaNi1/3Fe1/3Mn1/3O2||Na pouch cells. This work provides a clue for crystallographic regulation for dendrite-free Na anodes and paves a pathway toward high-energy-density Na metal batteries.