Artificial Heterogeneous Interphase Layer with Boosted Ion Affinity and Diffusion for Na/K‐Metal Batteries

Abstract Metallic Na (K) are considered a promising anode materials for Na‐metal and K‐metal batteries because of their high theoretical capacity, low electrode potential, and abundant resources. However, the uncontrolled growth of Na (K) dendrites severely damages the stability of the electrode/electrolyte interface, resulting in battery failure. Herein, a heterogeneous interface layer consisting of metal vanadium nanoparticles and sodium sulfide (potassium sulfide) is introduced on the surface of a Na (K) foil (i.e., Na 2 S/V/Na or K 2 S/V/K). Experimental studies and theoretical calculations indicate that a heterogeneous Na 2 S/V (K 2 S/V) protective layer can effectively improve Na (K)‐ion adsorption and diffusion kinetics, inhibiting the growth of Na (K) dendrites during Na (K) plating/stripping. Based on the novel design of the heterogeneous layer, the symmetric Na 2 S/V/Na cell displays a long lifespan of over 1000 h in a carbonate‐based electrolyte, and the K 2 S/V/K electrode can operate for over 1300 h at 0.5 mA cm –2 with a capacity of 0.5 mAh cm –2 . Moreover, the Na full cell (Na 3 V 2 (PO 4 ) 3 ||Na 2 S/V/Na) exhibits a high energy density of 375 Wh kg –1 and a high power density of 23.5 kW kg –1 . The achievements support the development of heterogeneous protective layers for other high‐energy‐density metal batteries.