Bio-inspired choline chloride-based deep eutectic solvents as electrolytes for lithium-ion batteries

The safety issues of lithium-ion batteries require the substitution of volatile and flammable organic components of the electrolyte. In this context, deep eutectic solvents (DESs) represent an interesting alternative to conventional ionic liquids as green solvents to dissolve common lithium salts. This paper explores two eutectics: i) ethylene glycol/choline chloride (EG/ChCl, 3:1 mol/mol), and ii) L-(+)-lactic acid/choline chloride (LA/ChCl, 2:1 mol/mol). The lithium salts added in both cases were LiN(CF3SO2)2 and LiPF6, both in concentration of either 0.5 M or 1 M. They still retain their liquid properties despite the addition of relatively high molar contents (up to 1.0 M) of lithium salts. The 0.5 M LiPF6/EG:ChCl electrolyte, in particular, displays ionic conductivity of 7.95 mS cm−1 at room temperature, and is thus very promising as a green and cheap electrolyte.