Synergistic regulation of bottom-up sodium deposition via sodiophilicity and electric field dual gradients for long-cycle sodium metal batteries

• • The dual-gradient SSM-ZnS@Zn framework achieves a bottom-up sodium deposition mode, effectively suppressing dendrite growth and volume fluctuation, as evidenced by stable cycling in symmetric cells over extended cycles (exact cycle number not specified in text). • • The electric field gradient arises from a 12.8-fold difference in electrical conductivity between the bottom zinc foil (~16.6×10^6 S m−1) and the top SSM (~1.3×10^6 S m−1), which homogenizes current density and electric potential distribution. • • The sodiophilicity gradient is formed by in-situ generated NaZn13 and Na2S on the bottom zinc foil, which are sodiophilic, while the upper SSM is sodiophobic, guiding sodium deposition from bottom to top. • • The pouch cell assembled with SSM-ZnS@Zn successfully lit an LED lamp, demonstrating practical application potential for high-energy sodium metal batteries.