Regulation of Electrostatic Shielding Effect by 18-Crown-6 Ether for Achieving Stable Deposition of Potassium Metal Anodes

Potassium (K) metal stands out as a promising anode material for rechargeable K batteries, due to its low redox potential and high capacity. However, K-metal anodes suffer from interfacial instability in polar organic electrolytes alongside uncontrolled dendrite growth during electrodeposition. Herein, we propose an innovative approach for improving the stability of K-metal anodes. This involves incorporating 4 wt % of 18-crown-6 (18C6) as an additive in a carbonate-based electrolyte solution comprising 0.5 M potassium hexafluorophosphate dissolved in ethylene carbonate/diethyl carbonate. The key of this strategy is that 18C6 coordinates K+ into the cavity, forming a robust K+–18C6 complex. This complex exhibits higher reductive stability compared to other ion–solvent complexes in the electrolyte. During the plating reaction, this unique feature induces an electrostatic shielding effect, altering the transition of the K-deposition behavior from self-amplification to self-flattening. Consequently, it forms a stable solid electrolyte interphase, resulting in dendrite-free electrodeposition of K.