Room Temperature Ionic Liquid as Electrolyte for Lithium Ion Battery

摘要

Applicability of RTIL as electrolyte for lithium ion battery wasassessed using coin-cells with Li[Li_(0.2)Mn_(0.54)Ni_(0.13)Co_(0.13)]O_2 ascathode, metallic lithium foil as anode, Cellgard 2300 as separatorand LiTFSI-Py_(14)TFSI as electrolyte. Those with LiTFSI higherthan 0.4 M showed a high initial discharge capacity (190 mAh g~(-1)at 0.2 C) and good cycling stability (> 98% coulombic efficiencies)after first cycle. Change upon cycling and storage was investigatedby impedance measurement at open circuit potential (ca. 3 V) withresults showing a relatively high resistance, 10 ～ 20 Ω forelectrolyte resistance (R_e) and 100 ～ 200 Ω for SEI and chargetransfer resistance (R_(sei) + R_(ct)). As the total resistance is stable afterstorage for 30 days, good stability of the cathode/IL electrolyte andLi/IL electrolyte interface is indicated. The use of Py_(14)TFSI-addedmixed electrolyte system to enhance current rating and reduce firehazards were studied with results discussed.