Key Takeaways & Executive Findings
- •• • 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.
Abstract
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.
1. Introduction
Sodium metal anodes are attractive for low-cost, high-energy batteries due to their high theoretical capacity (1166 mAh g−1) and low redox potential (−2.71 V vs. H+/H2). However, uncontrolled dendrite growth and drastic volume changes during repeated plating/stripping cause internal short circuits and safety hazards, hindering practical application. Conventional strategies such as electrolyte optimization, artificial SEI layers, and 3D host structures have been explored, but they often fail to simultaneously address the inhomogeneous distribution of current density and electric potential, which is a critical factor inducing dendrite formation.
Gradient structures have emerged as a promising approach, but most reported materials only employ a single type of gradient. This work introduces a dual-gradient design combining sodiophilicity and electric field gradients in a 3D SSM-ZnS@Zn current collector. The substantial conductivity difference between the bottom zinc foil and top stainless steel mesh creates an electric field gradient, while the in-situ generated sodiophilic NaZn13 and Na2S on the bottom foil establish a sodiophilicity gradient. This synergistic regulation guides bottom-up sodium deposition, homogenizes current density, and reinforces mechanical robustness, offering a new pathway to overcome the limitations of single-gradient strategies.
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Jiawen Yan, Zixian Lv, Xiaoqiang Cui, Kaishun Li, Yuehai Song, Xiang Chen, Xunzhu Zhou, Huanhuan Dong, Lin Li, Jianchao Sun (2026). Synergistic regulation of bottom-up sodium deposition via sodiophilicity and electric field dual gradients for long-cycle sodium metal batteries. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4188-x
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Frequently Asked Questions
What is the specific cycle life and Coulombic efficiency achieved in symmetric cells using the SSM-ZnS@Zn framework?
The research text does not provide explicit numerical values for cycle life or Coulombic efficiency in the provided sections. However, it states that the framework exhibits outstanding electrochemical performance in both symmetric and full cells, outperforming most reported 3D structures. Detailed metrics are likely available in the full paper.
How does the dual-gradient design quantitatively improve the uniformity of sodium deposition compared to single-gradient or bare Zn foil?
The dual-gradient design combines an electric field gradient (conductivity difference of ~12.8×) and a sodiophilicity gradient (NaZn13 and Na2S on bottom, sodiophobic SSM on top) to guide bottom-up deposition. This synergy homogenizes current density and electric potential, reducing dendrite growth. Quantitative improvements in deposition uniformity are not specified in the text but are implied by enhanced electrochemical performance.
What is the scalability of the fabrication process for SSM-ZnS@Zn, and what are the cost implications compared to conventional copper or aluminum current collectors?
The fabrication involves a facile hydrothermal sulfidization of zinc foil followed by a one-step rolling process to embed the stainless steel mesh. This is a scalable and potentially low-cost method. However, the text does not provide cost analysis or comparison with conventional current collectors. The use of zinc and stainless steel suggests lower cost than sodium metal hosts, but detailed economic assessment is not included.
What are the failure mechanisms of the SSM-ZnS@Zn framework under high areal capacity or high current density conditions?
The text does not specify failure mechanisms under extreme conditions. It emphasizes that the dual-gradient design suppresses dendrite growth and volume changes, but quantitative limits (e.g., maximum current density, areal capacity) are not provided. Further details would be in the full paper.
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