Construction of KF‐Rich Solid Electrolyte Interfaces Based on the Electrodeposition Behavior of FEC Additives for Protecting K‐Metal Anodes

It is feasible to construct a KF-rich solid electrolyte interface (SEI) layer via electrodeposition using fluoroethylene carbonate (FEC) solution as an additive. The freshly deposited K metal reacts in situ with FEC, forming a uniform and robust KF-rich SEI layer. This discovery provides valuable insights into the construction of KF-SEI layers, offering significant guidance in this area.

Abstract

Potassium metal (K) electrodes have attracted much attention as one of the most promising anode materials in potassium metal batteries. Nevertheless, dendrite growth and unstable solid electrolyte interface (SEI) have seriously hindered the practical application of potassium-metal anodes. Therefore, to address the aforementioned issue, a brand-new method is proposed: electrodeposition to construct a KF-rich artificial SEI layer, which can improve the stability and cycle time of the K metal anode. The homogeneous KF-rich SEI layer is formed via an in situ reaction between fresh K metal and the electrolyte additive fluoroethylene carbonate (FEC) during electrodeposition. This exerts tremendous effects on protecting the electrode and inhibiting the growth of dendrites. With the uniform and robust SEI layer, the potassium-metal symmetric battery has been stably cycled for more than 1400 h in a conventional carbonate electrolyte (0.8 m KPF₆-based electrolyte (EC:DEC = 1:1, v/v)). In addition, K||Prussian blue (PPB) batteries with this conventional carbonate electrolyte can be operated for more than 200 cycles with an average Coulombic efficiency of 99.4%. This study sheds light on the construction mechanism of the KF-rich artificial SEI layer on K-metal anodes.