image: Figure 1 Design and characterization of gradient electrode. (a) Cross-sectional SEM image, the corresponding EDS mapping and the corresponding elemental line scan of NS/Na. (b) The measured potential of NS/Na. (c) Schematic illustration of the NS/Na electrode after Na plating and stripping process. (d) Cross-sectional SEM image, the corresponding EDS mapping and the corresponding elemental line scan of GNS/Na. (e) The measured potential of GNS/Na. (f) Schematic illustration of the GNS/Na electrode after Na plating and stripping process. We prepared cross-sectional samples of NS/Na and GNS/Na, measuring the potential in five 5-micrometer regions from top to bottom of the modified layer using KPFM (Fig. S7 and S8).
Credit: ©Science China Press
The development of sustainable energy storage systems demands cost-effective and high-performance battery technologies. Sodium (Na)-based batteries have emerged as promising alternatives to conventional lithium-ion batteries in the renewable energy sector, primarily due to the greater natural abundance and lower cost of Na. However, the realization of high-energy-density Na batteries faces fundamental challenges at the anode, where three critical requirements converge: high capacity, Na compensation capability, and dendrite suppression.
Now, a research team led by Prof. Danni Lei and Prof. Chengxin Wang at Sun Yat-sen University has developed a gradient sodium-tin/sodium bilayer anode (GNS/Na) that addresses these critical issues. The work, published in National Science Review, demonstrates the new anode that fundamentally redefines sodium deposition behavior.
A gradient sodium-tin/sodium bilayer anode (GNS/Na) via in-situ chemical displacement involving Sn ethoxide reduction and controlled interdiffusion. The compositionally modulated unsaturated NaxSny alloys (x/y≤15:4) serves as an electrochemical buffer layer, which simultaneously optimizes both the thermodynamics and kinetics of ion diffusion, thereby achieving dendrite-free morphology. Beneath this gradient layer, the bulk Na reservoir ensures both the stability of gradient structure and compensation of Na+ depletion through dynamic ion replenishment during extended cycling. Therefore, this work redefines anode design principles. As a result, the symmetric cell achieves an ultralong cycle life of 7000 and 700 hours at current densities of 3 and 10 mA cm−2, respectively. Notably, when paired with a high-loading Na3V2(PO4)3 (NVP) (30 mg cm−2) cathode, the full cycles stably for nearly 1000 cycles and delivers an unprecedented energy density of 200 Wh kg−1. We establish a materials design paradigm that simultaneously addresses capacity, stability, and safety–key barriers to sustainable energy storage. This strategy can be extended to post-lithium batteries.
This achievement has been published in National Science Review. Original article link: https://doi.org/10.1093/nsr/nwaf427