Highly reversible Na and K metal anodes enabled by carbon paper protection

Abstract Alkali metal batteries are now under revival for their large energy density. But their practical viability hinges on the successful development of safe and cyclable alkali metal anodes, preferrentially via scalable and cost-effective methods. Despite tremendous research efforts on the Li metal anode, the attention on Na and K is considerably less. In this work, we report a general and straightforward strategy to enhance the electrochemical performances of Na and K metal anodes. When their surfaces are covered with a thin piece of commercial carbon paper as the protection layer, both Na and K metal anodes exhibit significantly improved overpotentials and cycling stability (up to ~1200 cycles for Na and ~3000 cycles for K) within carbonate or ether electrolyte and even under large current density (5 mA cm −2 ). Proof-of-concept sodium metal batteries are also assembled using the protected Na metal anode and Na 3 V 2 (PO 4 ) 3 cathode, and demonstrate large areal capacity and impressive cycle life. Given its effectiveness, scalability and low cost, we believe that our strategy holds great promise for practical implementation.