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 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.
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