Durable sodium iodide interphase stabilizing sodium metal anodes

The implementation of sodium metal batteries (SMBs) is known for their low cost and high energy density. However, a major concern in SMBs is the formation of dendrites on the Na metal anode, which can potentially cause short circuits and compromise safety. Herein, to address this issue, we propose a novel approach to create a protective layer by decorating Na surface with NaI particles. This protective layer exhibits a high Young’s modulus and excellent sodium ion transference ability. As a result, the lifespan of the Na/NaI||Na/NaI cell is significantly extended to 850 h at 0.5 mA cm −2 /1 mAh cm −2 . Furthermore, when the Na/NaI anode is combined with a Na 3 V 2 (PO 4 ) 3 (NVP) cathode, the full cell retains 83 mAh g −1 (approximately 94% of its initial capacity) even after 1500 cycles at 5 C. Overall, this work presents a simple and effective method for establishing a protective layer on the Na surface, thereby enabling the realization of long lifespan and stable SMBs.