Design Principles of Sodium/Potassium Protection Layer for High‐Power High‐Energy Sodium/Potassium‐Metal Batteries in Carbonate Electrolytes: a Case Study of Na 2 Te/K 2 Te

The sodium (potassium)-metal anodes combine low-cost, high theoretical capacity, and high energy density, demonstrating promising application in sodium (potassium)-metal batteries. However, the dendrites' growth on the surface of Na (K) has impeded their practical application. Herein, density functional theory (DFT) results predict Na2 Te/K2 Te is beneficial for Na+ /K+ transport and can effectively suppress the formation of the dendrites because of low Na+ /K+ migration energy barrier and ultrahigh Na+ /K+ diffusion coefficient of 3.7 × 10-10 cm2 s-1 /1.6 × 10-10 cm2 s-1 (300 K), respectively. Then a Na2 Te protection layer is prepared by directly painting the nanosized Te powder onto the sodium-metal surface. The Na@Na2 Te anode can last for 700 h in low-cost carbonate electrolytes (1 mA cm-2 , 1 mAh cm-2 ), and the corresponding Na3 V2 (PO4 )3 //Na@Na2 Te full cell exhibits high energy density of 223 Wh kg-1 at an unprecedented power density of 29687 W kg-1 as well as an ultrahigh capacity retention of 93% after 3000 cycles at 20 C. Besides, the K@K2 Te-based potassium-metal full battery also demonstrates high power density of 20 577 W kg-1 with energy density of 154 Wh kg-1 . This work opens up a new and promising avenue to stabilize sodium (potassium)-metal anodes with simple and low-cost interfacial layers.