Stabilization of Lithium Bis(fluorosulfonyl)imide Electrolyte by the Incorporation of Pyridinium Ionic Liquids for Advanced Lithium-Ion Batteries

Highly efficient lithium-ion batteries (LIBs) with lithium bis(fluorosulfonyl)imide (LiFSI) electrolytes have been explored over LiFP₆ electrolytes owing to their fabulous ionic conductivity, good thermal stability, and HF-free nature. This work investigates the influence of ionic liquid (IL), 1-propyl-2-methylpyridium bis(trifluoromethylsulfony)imide ([Pyr₃-₂Me][(CF₃SO₂)₂N], Pyr₃₂TFSI) as an additive in LiFSI electrolyte on the electrical, electrochemical, and flammability properties of LIBs. The addition of Pyr₃₂TFSI additive has considerably elevated the ionic conductivity and thermal stability of LiFSI electrolytes. Pyr₃₂TFSI IL modified LiFSI electrolyte exhibits an increased ionic conductivity from 16.4 mS·cm⁻¹ (LiFSI electrolyte) to 17.3 mS·cm⁻¹. With Pyr₃₂TFSI additive, the lithium transfer number ((Formula presented.)) has increased, which is usually associated with the synergistic effect of the additive to LiFSI and builds an inorganic “LiF”-rich dendrite-free interphase. The flammability test of Pyr₃₂TFSI IL modified LiFSI electrolyte explicates the nonflammable nature, indicating excellent stability in ambient and extreme circumstances. Fabricated graphite|Li half-cell LIBs with Pyr₃₂TFSI IL modified LiFSI electrolytes, display the improved performance in charging/discharging ability with a capacity of 380 mAh·g⁻¹, exhibiting marvelous cycling stability up to 200 cycles. Our work shows that incorporating LiFSI with novel ILs could be a promising approach for manufacturing high-performance liquid electrolytes for LIBs.