Non-flammable Inorganic Liquid Electrolyte Lithium-Ion Batteries

Abstract

Reduced safety of conventional organic electrolyte (OE) lithium-ion batteries (LIBs) during abusive failure conditions pose a technical barrier and the state of uncertainty in the market penetration of electrification of vehicles and stationary storage. To address this, we report nonflammable inorganic liquid electrolyte LiFePO4/Graphite (LFP/G) batteries for commercial high energy/power applications. The inorganic electrolyte (IE) is prepared by solvating the molten LiAlCl4 salts using liquid/gaseous xSO2 (x = 1 to 22 moles SO2, proprietary formulae is used) which shows remarkably high Li+ ion conductivity of 121 mS cm−1 at 22 °C. IE LFP/Li half-cell exhibits outstanding rate capability up to 8 C with the capacity of 74 mAh g−1 at room temperature (RT). For the first time, IE-based commercial prototype LFP/G prismatic cells with the capacity of 1.08 Ah shows ultrahigh longevity (50,000 cycles at 2 C up to 20% residual capacity) with coulombic efficiency of ∼99.99% and constant internal resistance at RT. We also demonstrate depth of discharge up to 0 V for 150 cycles using IE LFP/G cells at RT, which shows comparable cycling stability of cells which are discharged to 2.5 V, in contrast to OE LIBs. Further, the capacity retention is improved by 5% using dip-coating process of positive electrodes.