Asymmetric tetraalkyl ammonium cation-based ionic liquid as an electrolyte for lithium-ion battery applications

Performance of N-butyl N,N,N-triethylammonium bis(trifluoromethanesulfonyl)-imide (N2224TFSI) as a room temperature ionic liquid (RTIL) containing ethylene carbonate (EC)/diethylcarbonate (DEC) and lithium salt has been investigated as an electrolyte for lithium-ion battery. The electrolyte is highly resistant to fire during direct exposure to the flame, indicating its non-flammable nature. The overall electrochemical window of the ionic liquid (IL) electrolyte is up to 5.7 V vs. Li metal without any solvent decomposition, as confirmed by linear sweep voltammetry (LSV). The electrolyte has low viscosity (32.9 cPs) and high conductivity (5.23 mS cm−1) with effective SEI film-forming ability. The performance of the IL electrolyte has been tested with lithium-ion half cells using LiFePO4 and mesocarbon microbead (MCMB) electrodes, showing good galvanostatic cycling with high capacity retention of about 84 and 90 %, respectively.