Ultrastable Dendrite-Free Potassium Metal Batteries Enabled by Weakly-Solvated Electrolyte
Ping Gao, Fei Zhang, Xingchao Wang, Miaomiao Wu, Qian Xiang, Aikai Yang, Ying Sun, Jixi Guo, Yudai Huang
Abstract
Potassium (K) metal is considered one of the most promising anodes for potassium metal batteries (PMBs) because of its abundant and low-cost advantages but suffers from serious dendritic growth and parasitic reactions, resulting in poor cyclability, low Coulombic efficiency (CE), and safety concerns. In this work, we report a localized high-concentration electrolyte (LHCE) consisting of potassium bis(fluorosulfonyl)imide (KFSI) in a cosolvent of 1,2-dimethoxyethane (DME) and 1,1,2,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) to solve the problems of PMBs. TTE as a diluent not only endows LHCE with advantages of low viscosity, good wettability, and improved conductivity but also solves the dendrite problem pertaining to K metal anodes. Using the formulation of LHCE, a CE of 98% during 800 cycles in the K||Cu cell and extremely stable cycling of over 2000 h in the K||K symmetric cell are achieved at a current density of 0.1 mA cm –2 . In addition, the LHCE shows good compatibility with a Prussian Blue cathode, allowing almost 99% CE for the K||KFe II Fe III (CN) 6 full cell during 100 cycles. This promising electrolyte design realizes high-safety and energy-dense PMBs.