Characterising Lithium-Ion Electrolytes via Operando Raman Microspectroscopy

Knowledge of electrolyte transport and thermodynamic properties in Li-ion and 'beyond Li-ion' technologies is vital for their continued development and success.  

In this paper, published in Nature Communications, Jack Fawdon, Johannes Ihli, Fabio La Mantia and Mauro Pasta of The Pasta Group present a method for fully characterising electrolyte systems.  This was achieved by measuring the electrolyte concentration gradient over time via operando Raman microspectroscopy, in tandem with potentiostatic electrochemical impedance spectroscopy, the Fickian 'apparent' diffusion coefficient, transference number, thermodynamic factor, ionic conductivity and resistance of charge-transfer were quantified within a single experimental setup.

Using lithium bis(fluorosulfonyl)imide (LiFSI) in tetraglyme (G4) as a model system, the study provides a visualisation of the electrolyte concentration gradient, a method for determining key electrolyte properties, and a necessary technique for correlating intermolecular electrolyte structure with the described transport and thermodynamic properties.