Surface Work Function‐Induced High‐Entropy Solid Electrolyte Interphase Formation for Highly Stable Potassium Metal Anodes

Abstract The failure of the solid electrolyte interphase (SEI) layer is a key issue limiting the practical application of potassium metal batteries. Herein, a novel high‐entropy SEI layer rich in inorganic components is designed and constructed via in situ electrochemical conversion of the Sn 3 O 4 /Sn 2 S 3 interfacial layer on a porous scaffold. Theoretical studies and experimental techniques reveal that the Sn 3 O 4 /Sn 2 S 3 heterostructure, with its low work function and weak Sn─O/S bond, significantly enhances reactivity with the electrolyte, thereby facilitating the in situ formation of the high‐entropy SEI layer. The in situ generated high‐entropy SEI exhibits low surface roughness, low surface potential, fast potassium ion transport characteristics, and excellent mechanical properties (Young's modulus of 20.08 GPa). Leveraging these advantageous properties of the high‐entropy SEI, the resulting potassium metal anode achieves an excellent rate performance up to 10 mA cm −2 in symmetric cells and demonstrates outstanding cycling stability for 2500 h at 0.5 mA cm −2 . When paired with a perylene‐3,4,9,10‐tetracarboxylic dianhydride cathode, the potassium metal full battery retains 81.6% of its capacity over 1650 cycles at 10 C. This work underscores a straightforward and effective approach for the establishment of a stable interphase on metallic potassium anodes.