Amorphous phosphatized hybrid interfacial layer for dendrite-free sodium deposition

Sodium (Na) is a promising anode material for sodium ion batteries due to its high theoretical capacity and favorable redox voltage, but the dendrite growth issue limits its practical application. Herein, an artificial hybrid interface layer based on an amorphous phosphatized hybrid (a-Na3P/NaBr) is developed to facilitate a homogeneous and dendrite-free lateral growth behavior during recurring sodium plating/stripping processes. The proposed Na metal anode delivers an excellent cycling performance for over 200 cycles with an average Coulombic efficiency 99.5% under the capacity of 3 mAh cm-2. Besides, the symmetric cell also persists for over 2000 h under the same capacity. Notably, under the depth of discharge as high as 50%, the modified Na metal anode can still be stably cycled for nearly 350 h, showing much superior performance to the bare Na counterpart. Benefiting from these advantages, the full cell based on the Na anodes with this amorphous phosphatized hybrid interphase coating delivers a 98% capacity retention even after 1200 cycles. We believe that these findings will provide a promising avenue for the next-generation Na metal-based energy storage technologies.