Assessing the Ion Transport Properties of Highly Concentrated Non-Flammable Electrolytes in a Commercial Li-Ion Battery Cell

Abstract

In order to assess the ion transport properties of alternative non-flammable electrolytes in a typical commercial Li-ion battery cell, we have measured the ionic conductivity σion and the lithium-ion transference number under anion-blocking conditions, tABCLi+, for two classes of highly concentrated battery electrolytes: (i) Mixtures of the ionic liquid N-methyl-N-propyl-pyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) with different amounts of the lithium bis(fluorosulfonyl)imide (LiFSI), and (ii) a solvate ionic liquid consisting of an equimolar mixture of tetraglyme (G4) and LiFSI. Together with previously published data on the solvate ionic liquid G4/LiTFSI (1 : 1), the obtained Li+ ion transport data was used to estimate the overall resistance and the resulting maximum cycling rate of a commercial 10 Ah Li-ion pouch cell containing these alternative electrolytes. Our results suggest that Pyr13FSI/LiFSI mixtures would allow for maximum charging/discharging rates close to 1 C, while the solvate ionic liquids would only support maximum rates of about 0.3 C.