Regulating the coordination of solvent molecules with K salts for non-flammable and durable potassium-ion batteries with all-aluminum current collectors

The full utilization of affordable potassium-ion batteries (PIBs) based on all-aluminum current collectors is plagued by low specific energy, limited lifespan, and safety concerns, which are primarily dictated by the lack of proper electrolytes suitable for high-capacity electrodes. New molecular insights, ranging from bulk solvation chemistry to interfacial behaviors, should be proposed for the design of compatible electrolytes. The fluorinated triethyl phosphate (FTEP) of tris(2,2,2-trifluoroethyl) phosphate was elaborately selected as the low-polarity solvating solvent to create an anion-rich solvation sheath, albeit at the expense of salt dissolution degree with reduced ion mobility at a moderate concentration (1.0 mol/L). The deficiency of the solvating-solvent molecules in the primary solvation sheath facilitates the formation of a protective layer derived from FSI^- anions decomposition and ultimately inhibits the undesirable side reactions on both electrode/electrolyte interfaces. Moreover, the sole solvating solvent of FTEP endows the electrolyte with exceptional flame retardancy. The results obtained in this work provide crucial insights into the role of solvation chemistry on the solvation structure and interfacial transport dynamics, which is critical for advancing the development of compatible electrolytes for high-performance PIBs.