Lithium bis(trifluoromethanesulfonyl)imide solution

Lithium bis(trifluoromethanesulfonyl)imide in ethylene carbonate and dimethylcarbonate, 1.0 M LiTFSI in EC/DMC=50/50 (w/w) is a solution of battery-grade LiTFSI dissolved in binary mixture of EC/DMC (50:50) wt%. The product is a clear solution with strictly minimized impurities including low moisture (≤100 ppm), low trace metals (≤10 ppm Na and K), low chloride (<10 ppm), and low sulfate (<10 ppm).

LiTFSI-based electrolytes have advantages over LiPF₆-based electrolytes because LiTFSI is less sensitive to hydrolysis, safer to handle, and is more stable thermally and electrochemically. These advantages enable longer cycling times and less corrosion of aluminum current collectors at moderate to high working temperatures. Ethylene carbonate (EC) is a popular choice of solvent because it provides a high-dielectric constant to dissolve the electrolytic salt and helps to form an ionically conductive, passivating solid electrolyte interphase (SEI) on the electrodes. The addition of dimethylcarbonate (DMC) lowers the blend’s viscosity and melting point, yielding an electrolyte with a good balance between desirable electrochemical properties, high dielectric constant, and low viscosity. In one study comparing solvent blends, it was found that a EC/DMC solvent is more conductive than the EC/DEC counterpart. Experimentally, using Walden′s rule, it has been observed that 1.0 M LiTFSI in EC/DMC is more ionically conductive than 1.0 M LiPF₆ in the same binary solvent.