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

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., Na2 S/V/Na or K2 S/V/K). Experimental studies and theoretical calculations indicate that a heterogeneous Na2 S/V (K2 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 Na2 S/V/Na cell displays a long lifespan of over 1000 h in a carbonate-based electrolyte, and the K2 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 (Na3 V2 (PO4 )3 ||Na2 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.