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 (Rb 2 CO 3 ) 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 Na 3 V 2 (PO 4 ) 3 ||GPE+R||Na cells. The practical viability and mechanical flexibility are further verified by the operation of NaNi 1/3 Fe 1/3 Mn 1/3 O 2 ||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.