Synergistic regulation of bottom-up sodium deposition via sodiophilicity and electric field dual gradients for long-cycle sodium metal batteries
Sodium metal anodes, with high theoretical capacity (1166 mAh g−1) and low redox potential (−2.71 V vs. H+/H2), are promising for low-cost, high-energy sodium metal batteries (SMBs). However, uncontrolled dendrite growth and drastic volume changes cause short circuits and safety hazards. This work presents a dual-gradient engineering strategy to address these issues. A 3D self-supporting current collector (SSM-ZnS@Zn) was fabricated by laminating a stainless steel mesh (SSM) with a Zn foil decorated with pre-grown ZnS nanoparticles via a one-step rolling process. The substantial electrical conductivity difference between the bottom zinc foil (~16.6×10^6 S m−1) and the top SSM (~1.3×10^6 S m−1) establishes an electric field gradient. Simultaneously, a sodiophilicity gradient is created by electrochemically in-situ generated sodiophilic NaZn13 and Na2S on the bottom zinc foil, combined with the sodiophobic upper SSM layer. This dual-gradient synergy guides bottom-up sodium deposition, homogenizes current density and electric potential, and reinforces mechanical robustness. The framework exhibits outstanding electrochemical performance in both symmetric and full cells, outperforming most reported 3D structures. A pouch cell assembled with SSM-ZnS@Zn successfully lit an LED lamp, demonstrating practical application potential. This strategy surpasses single-gradient limitations and offers a new approach for high-performance sodium metal anode design.