Advanced LiFSI-LiPF ₆ Electrolyte for Wide-Temperature and Thermally Stable Lithium-Ion Batteries

A new optimized LiFSI–LiPF 6 dual-salt controlled-solvation electrolyte (E-DS) is demonstrated to enable practical graphite||LiNi 0.8 Mn 0.1 Co 0.1 O 2 cells (≈4.1 mAh cm −2 ) to achieve exceptional performance and safety under extreme conditions. By optimizing anion coordination with the smaller, more dissociating FSI − anion, the E-DS forms ultrathin, dense, and inorganic-rich electrode/electrolyte interphases that dramatically suppress solvent decomposition, transition-metal dissolution, and surface reconstruction compared to the conventional LiPF 6 /carbonate electrolyte. Consequently, E-DS cells deliver >78% capacity retention after 300 cycles at 60 °C, retain fast discharging capacity at 30 °C, and operate effectively at −20 °C. Most strikingly, fully charged full cells with E-DS, even under overcharging to 4.8 V and elevated temperatures, show a lower heat evolution in stable formulations—transforming a traditionally unstable high-voltage/high-temperature configuration into an intrinsically safe state. This work establishes a new benchmark for carbonate-containing electrolytes, simultaneously achieving high energy density, fast-discharging capability, wide-temperature operation (−20 to 60 °C), and outstanding thermal safety in nickel-rich lithium-ion batteries.