Alkoxy substituted imidazolium-based ionic liquids as electrolytes for lithium batteries

The design and the optimization of new electrochemically stable and safer electrolytes for both Li-ion and Li–air/Li–O2 batteries is a key-target in the field of clean energy. Ionic liquids (ILs) were often indicated as components of the electrolytes of the future, because they could fulfil all the requirements for the use in electronic devices and they also address the safety issues for large-scale applications.In this work, two ether-functionalized ILs, namely 1-(2-methoxyethyl)-3-methylimidazolium TFSI (IMI1,2O1TFSI) and 3-(2-(2-methoxyethoxy)ethyl)-1-methylimidazolium TFSI (IMI1,1O2O1TFSI) were synthesized and characterised from a physical and electrochemical point of view. The thermal features, viscosity, conductivity and electrochemical stability were compared with those of an alkyl-IMITFSI (BuMeIMITFSI) in order to evaluate the influence of the alkoxy-groups on the electrolyte performances. Preliminary battery tests in Li/LiFePO4 cells containing solutions of IL-LiTFSI mixed with EC/DEC as electrolytes were also performed to address the cycling behaviour and the delivered capacity.

► Novel alkoxy-imidazolium ionic Liquids as electrolytes for lithium batteries.
► Safer mixtures based on alkoxy-IMITFSI and organic carbonates.
► R.t. conductivity >5 mS cm−1 in case of IMITFSI with the shorter ether side chain.