Impact of ionic liquid on lithium ion battery with a solid poly(ionic liquid) pentablock terpolymer as electrolyte and separator

In this study, the physical, transport, mechanical, morphological, and electrochemical properties of a ternary blend solid polymer electrolyte (SPE) (poly(ionic liquid) (PIL) multiblock polymer, lithium salt, and ionic liquid (IL)) were systematically investigated as a function of IL concentration. With increasing IL concentration, the conductive volume increases along with the polymer chain segmental mobility. This facilitates high ionic conductivity, while the mechanical modulus exhibits a percolation threshold. Surprisingly, at higher IL concentrations, there is a reduction in the lithium cation mobility as evidenced by pulsed-field gradient nuclear magnetic resonance, which coincides with an increased overpotential evidenced by lithium metal stripping and plating. Stable lithium ion battery cycling durability (over 100 cycles at room temperature) is demonstrated with the ternary blend SPE as the electrolyte and separator. This work provides valuable insights into the design of new SPEs with both high ionic conductivity and improved battery stability.