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

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 Sn₃O₄/Sn₂S₃ interfacial layer on a porous scaffold. Theoretical studies and experimental techniques reveal that the Sn₃O₄/Sn₂S₃ 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.