Design Principles of Sodium/Potassium Protection Layer for High‐Power High‐Energy Sodium/Potassium‐Metal Batteries in Carbonate Electrolytes: a Case Study of Na2Te/K2Te

Abstract 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 Na 2 Te/K 2 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 cm 2 s −1 /1.6 × 10 −10 cm 2 s −1 (300 K), respectively. Then a Na 2 Te protection layer is prepared by directly painting the nanosized Te powder onto the sodium‐metal surface. The Na@Na 2 Te anode can last for 700 h in low‐cost carbonate electrolytes (1 mA cm −2 , 1 mAh cm −2 ), and the corresponding Na 3 V 2 (PO 4 ) 3 //Na@Na 2 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@K 2 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.