Characterization of N-Methyl-N-Butylpyrrolidinium Bis(trifluoromethanesulfonyl)imide-LiTFSI-Tetra(ethylene glycol) Dimethyl Ether Mixtures as a Li Metal Cell Electrolyte

We have employed tetra(ethylene glycol)dimethyl ether (TEGDME) as a polymer solvent in mixed electrolytes composed of -methyl--butyl pyrrolidinium bis(trifluoromethanesulfonyl)imide , LiTFSI, and TEGDME and characterized their physical and electrochemical properties as well as the cyclability of cells with LiTFSI TEGDME electrolyte. The addition of the TEGDME polymer solvent to the TEGDME mixtures resulted in a significant enhancement of ionic conductivity, particularly at lower temperatures. Interfacial impedance and galvanostatic Li cycling measurements show that the TEGDME ternary mixture exhibits excellent compatibility with Li metal electrodes. The use of the ternary mixture as an electrolyte in a cell provided good charge and discharge capability of the cell at room temperature with a discharge capacity of sulfur at and at low temperature with a discharge capacity of about sulfur at for the first cycle, respectively (theoretical specific capacity sulfur). In addition, the cell tested at exhibited a stable cyclability after the , with a discharge capacity of sulfur for the .