Confining Dendrite Growth Enabled By Ionically Conductive Interphase for Highly Stable Potassium Metal Anode

Abstract

Potassium metal has been considered as one of the ultimate anode for rechargeable potassium batteries because of its high theoretical capacity (686 mAh g-1) and low electrode potential (~2.93 V vs. SHE). However, K metal is thermodynamically instable in aprotic electrolyte and uneven K plating usually leads to dendritic K metal deposition, resulting in low Coulombic efficiency and safety concerns.1,2In this study, we introduce potential strategy to stabilize the K metal anode via simple chemical interface control. The robust and ionically conductive passivation layer can be controllably designed by the spontaneous chemical reaction when a K metal foil kept in contact with a liquid phase potassium-polysulfide (0.05M K2S5 dissolved in DEGDME);3 this provides a strong guiding effect to form an electronically and ionically conductive solid electrolyte interphase (SEI) layer, enabling a dense K plating with dendrite-free morphology. The unique characteristics of the functionalized K-metal is fully evidenced by the Operando optical microscopy and phase field modeling in electrodeposition process. Under practical constraints (i.e. using lean electrolyte and thin polymer separator), the functionalized K-metal anode exhibits the ultra-long-term K plating-stripping cycles over 1200 h in a symmetrical cells and further highlights a practical applicability with high areal capacity and fast charging-discharging capability in full-cells using TiS2 cathode. References U.-H. Kim, G.-T. Park, B.-K. Son, G. W. Nam, J. Liu, L.-Y. Kuo, P. Kaghazchi, C. S. Yoon and Y.-K. Sun, Nat. Energy, 2020, 5, 860. J.-Y. Hwang, S.-T. Myung and Y.-K. Sun, Adv. Funct. Mater., 2018, 28, 1802938.J.-Y. Hwang, H. M. Kim, C. S. Yoon and Y.-K. Sun, ACS Energy Lett., 2018, 3, 540-541.