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

Abstract

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.