Synergistic Stabilization of Potassium Metal Anodes by Surface Imperfections Elimination and Robust Solid-Electrolyte Interphase

Potassium (K) metal anodes hold great promise for next-generation rechargeable batteries due to their low redox potential and abundance, yet are challenged by dendrite growth and unstable solid-electrolyte interphase (SEI). In this work, we optimize the K metal surface properties through manufacturing methods and tailor SEI properties via electrolyte concentrations, enabling a comprehensive investigation of the synergy of the K surface and SEI properties in enhancing K metal plating/stripping behavior. Our investigations reveal that the structural integrity of SEI is crucial for maintaining rapid, uniform mass transfer, while a smooth K surface enhances even electric field distribution; the synergy of the two amplifies the benefits of fast K plating/stripping kinetics and high deposition capacity with high reversibility and long lifespan, which cannot be achieved from improving the K surface or SEI individually. The optimized K||K symmetric cells exhibit long-term cycling stability at 0.5 mA cm−2 and 4 mA h cm−2 for over 4,000 hours, and K||K1.97Mn[Fe(CN)6] full cells achieve 84% capacity retention after 1,200 cycles with a cathode mass loading of 7.9 mg cm−2. These results highlight the importance of concurrent interfacial and morphological control in stabilizing K metal anodes for practical applications.