Experimental Measurement of Molecular Diffusion and Evaporation Rate of Battery Organic Electrolytes in Ambient Air

Abstract

In this paper, we measured the molecular diffusivity and evaporation rate of organic solvents—1,2-dimethoxyethane (DME), dimethyl carbonate (DMC), diethyl carbonate (DEC), and propylene carbonate (PC)—in ambient air, which are commonly used in light metal batteries, such as Li-ion, Li-air, and Na-O2 batteries. The measurement was conducted through the evolution of the evaporation rate of a liquid solvent in a glass tube, which was designed based on a one-dimensional (1-D) mass transfer model. The experiment successfully measured the diffusion coefficients of DME (0.0925 cm2 s−1), DMC (0.2116 cm2 s−1), and DEC (0.0569 cm2 s−1) in dry air, but failed for that of PC. The PC testing showed a liquid loss smaller than the measurement uncertainty due to its slow evaporation rate under the experimental condition. In the ambient air with the relative humidity (RH) of 50 ± 5%, higher water-soluble solvents showed more decrease in diffusivity calculation compared to that under the dry condition, which is likely due to uncertainty arising from water dissolving to the testing liquid. In addition, we also investigated the time constant for experimental measurement. For the organic liquids, the effective running time can be up to 10 days under room temperature.

Direct measurement of internal temperatures of commercially-available 18650 lithium-ion batteries

“…The internal components of the cell are exposed for approximately 2 h in the glovebox during the insertion process, and for a small amount of time afterward while the cells are being resealed. Previous research has shown that common Li-ion battery electrolytes evaporate slowly when exposed to dry ambient air 17 , which would result in only a small decrease in conductivity consistent with the small loss of capacity seen in the modified cells.…”

Spatial Variations of Cathode Reaction and Discharge Precipitate in Li-Air Batteries: Analysis and Experimental Measurement

“…Loss of the electrolyte due to evaporation and diffusion may also partially contribute to the observed difference. 48 In addition, the experimental reaction rate was obtained by averaging the reaction rate within each sublayer over the entire discharge period, while the model prediction considers a steady-state condition and hence a constant ORR profile. Note that the local reaction rate changed with time due to precipitate's impact, which is small due to the small volume fraction of precipitate as disclosed in the SEM images.…”