Al₂O₃ In-situ Modified Al Current Collectors for Uniform Na Plating/Stripping

Na metal batteries are considered to be one of the most promising large-scale energy storage batteries due to their high theoretical specific capacity and low cost. However, the high reactivity of sodium metal can easily lead to problems such as instability of the solid electrolyte interface (SEI) film, uneven deposition of sodium, and dendrite growth. Here, an Al₂O₃ in-situ modified Al foil current collector (Al@Al₂O₃) was fabricated by a facile one-step calcination method to promote uniform Na deposition/stripping. During the discharge process, Al₂O₃ is sodiumified to form a Na-Al-O film with high ion conductivity, which not only stabilizes the electrode/electrolyte interface, but also regulates the nucleation behavior on the current collector surface, reducing the formation of nuclear energy barrier, improving ion mass transfer kinetics, and achieving uniform deposition of dendrite-free sodium and long cycle life. The results show that Al@Al₂O₃ can stably deposit/strip sodium for 50 times with an average Coulombic efficiency of 99.6% under 3 mA·cm⁻²/3 mAh·cm⁻²; and that the Na-Al@Al₂O₃‖Na-Al@Al₂O₃ symmetric battery can be cycled stably for 1000 h at 1 mA·cm⁻² and 1 mAh·cm⁻². Even at a high current density of 10 C, the NVP‖Na-Al@Al₂O₃ full cell can be cycled stably for 250 cycles with a high capacity retention of 94%.