Mixing ionic liquids and ethylene carbonate as safe electrolytes for lithium-ion batteries

Abstract

With aim to design safety and high electrochemical-stability electrolytes, mixtures ionic liquids (ILs) – ethylene carbonate have been prepared and investigated for lithium-ion cell using LiMn2O4 (LMO) and LiFePO4 (LFP) as cathode materials. The addition of 20 % vol. ethylene carbonate (EC) could decrease significantly the viscosity as well as improve ionic conductivity and cycling performance of the electrolyte at room temperature. In the electrolyte containing 20% vol. EC, lithium-ion diffusion coefficient is still lower than commercial one based on conventional solvents. However, the stable charge - discharge behavior with N,N-dimethyl-N-ethyl-N-propylammonium bis(trifluoromethanesulfonyl) imide (N1123TFSI) based mixtures was achieved up to 120 mAh.g-1 in the first cycle and remaining round 100 mAh.g-1 within 20 cycles without any noticeable capacity loss, and a little bit lower with respect to 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) and N,N-dimethyl-N-ethyl-N-butylammonium bis(trifluoromethanesulfonyl) imide (N1124TFSI). The results also showed that the solvent addition up to 25% vol. maintained homogenous solution and good electrochemical stability of the electrolytes. 

IF: 4.51

DOI: 10.1016/j.molliq.2018.09.068