Room Temperature Ionic Liquid as Electrolyte for Lithium Ion Battery

has been reported to have a good room temperature ionic conductivity of higher than 1mS·cm-1 and an overall stability window in excess of 5.5V [1]. Py14TFSI with lithium salt (e.g. LiTFSI or LiPF6) thus provides a promising electrolyte for lithium ion secondary batteries application.LiTFSI-Py14TFSI solutions with various concentrations of LiTFSI salt were prepared by dissolving required amount of LiTFSI in neat Py14TFSI. The Py14TFSI/LiTFSI Room Temperature Ionic Liquid (RTIL) system prepared were investigated as electrolyte for lithium ion battery by various electrochemical methods using coin-type cells. Electrochemical cells were assembled with the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode electrodes, metallic lithium foil as anode, Cellgard 2300 as separator and LiTFSI-Py14TFSI as electrolyte. All operations were performed in the Argon-filled glove box. The fabricated IL-Cells with LiTFSI salt concentration higher than 0.4 M showed high initial discharge capacity of ca. 190 mAh/g when tested at 0.2 C together with good cycling stability and higher than 98 % coulombic efficiencies except for the first cycle. Electrochemical impedance spectra (EIS) technique was used to study the stability of the electrode/IL-electrolyte interface. The impedance response of Li/0.6 M LiTFSI-Py14TFSI/cathode cell at open circuit potential (ca. 3 V) during storage was recorded. The data were tested at different storage times, extending to 30 days. The results interpreted from equivalen