Fig. 1: Schematic of the method to measure key electrolyte properties.
From: Characterising lithium-ion electrolytes via operando Raman microspectroscopy
Li+ concentration (cs) gradient formation in an optical Li/Li symmetric cell, while current is passed. Using a scanning confocal Raman microspectrometer, a time-series of one-dimensional line scans was performed to obtain a progression of concentration gradients; measured with the stage moving in the z-direction. The cell was placed vertically on the stage to avoid natural convection. Potentiostatic electrochemical impedance spectroscopy (PEIS) was also performed prior to passing current to quantify ionic conductivity (κ) and resistance of charge-transfer (Rct), and between line scans to obtain an accurate concentration overpotential (ηc). Using the diffusion length (Ld), interfacial gradient (dcs/dz∣z = 0,L) and ηc from each concentration profile, the Fickian “apparent” diffusion coefficient (Dapp), cation transference number (\({t}_{+}^{0}\)), and molar thermodynamic factor (χM), were calculated.
