Regulating Sodium Deposition through Gradiently-Graphitized Framework for Dendrite-Free Na Metal Anode.

Na metal anode (NMA) is one of the most promising candidate materials for next-generation low-cost sodium metal batteries. However, the preferred deposition of Na metal at the anode/separator interface increases the risk of dendrite penetration of the separator, consequently, reduces safety and life of batteries with NMA. In this study, a Na deposition-regulating strategy is shown by designing a gradiently graphitized 3D carbon fiber (CF) framework as host (grad-CF), whereby Na is guided to deposit preferentially at the bottom of the anode, safely away from the separator. The obtained Na anode significantly reduces the probability of dendrite-induced short circuits. The grad-CF host enables NMA stable cycling at a high current density of 6 mA cm -2 . When the Na@grad-CF is applied as anode in full cells pared with Na 3 V 2 (PO 4 ) 3 (NVP) cathode, it exhibits a reversible capacity of 73 mA h g -1 after 500 cycles with a low decay rate of 0.13%.