Long-life potassium metal batteries enabled by anion-derived solid electrolyte interphase using concentrated ionic liquid electrolytes

Potassium metal batteries (PMBs) show great potential as next -generation energy storage systems yet face challenges such as the dendritic growth of the potassium anode, leading to issues with cycle life and safety. This study reports a potassium salt -concentrated ionic liquid electrolyte (PCIL) consisting of potassium bis(fluorosulfonyl)imide (KFSI) and 1-methyl-1-propyl pyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) to achieve long -life and, safe PMBs. PCIL presents several advantages including outstanding oxidation stability (approximate to 5.2 V), decent ionic conductivity (4.0 mS cm -1 at 25 degrees C), and negligible flammability. Moreover, PCIL promotes the development of anion -derived solid -electrolyte interphase (SEI) with high inorganic content. This not only hinders the growth of potassium dendrites but also facilitates facile interfacial charge transfer kinetics. Benefiting from these advantages, PMBs (K||KVPO 4 F) employing PCIL exhibit remarkable cycle performances at both ambient and elevated temperatures (capacity retention after 300 cycles: 74.8% at 25 degrees C and 82.9% at 45 degrees C), surpassing the performance of conventional carbonate (1 M KPF 6 EC/PC) and dilute potassium ionic liquid electrolyte (PIL). This work demonstrates the tangible capability of PCIL in realizing practical PMBs.