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Temperature dependence studies of electrochemical parameters provide insight into electron transfer processes. In cases where adding excess electrolyte causes experimental complications, e.g., colloidal systems, organic or biological samples, it is preferable to deal with the high resistivity of the medium. We validate the use of unsupported and weakly-supported solutions in thermoelectrochemical experiments. The temperature dependence of the diffusion coefficient allows calibration of the steady-state current to measure changes when a continuous-wave (CW) ultraviolet laser,λ= 325 nm, illuminates an ultramicroelectrode (UME) from the front. Calibrating the steady-state current ratios, before and after heating with a thermostatic bath, allows temperature measurements within an accuracy of 0.6 K. The solutions are without supporting electrolytes in methanol, a volatile solvent, and we use a model that accurately describes the viscosity and temperature dependence of the solvent. We calculated the temperature and derived an equation to estimate the error in the temperature measurement. A numeric method yields satisfactory results, considering the changes for both diffusion coefficients and viscosity explicitly, and predicts the thermostatic temperature bath, agreeing with the theoretical model’s error. In unsupported solutions, the ferrocene diffusion coefficient and the iodide apparent diffusion coefficient follow the expected increase with temperature. Under CW laser illumination, the UME temperature increase is: ΔT = 4 ± 1 K.
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Refractive Laser Beam Measuring Diffusion Coefficient of Concentrated Battery Electrolytes
Abstract A thorough understanding of electrolyte transport properties is crucial in the development of alternative battery technology. As a key parameter, the diffusion coefficient offers important insights into the behavior of electrolytes, especially for fast charge of high-energy batteries. Existing methods of measurement are often limited by redox species or offer questionable accuracy due to side reactions and/or disruption of the diffusion profile. This work provides a novel optical method for measuring diffusion coefficients of liquid-phase concentrated battery electrolytes without electrochemical reactions. The method relies on the deflection of a refractive laser beam passing through an electrolyte of a minor concentration gradient in a triangular diffusion column. The diffusion coefficient, D, for a range of zinc sulfate electrolytes was successfully extracted by correlating the position of the laser beam to its concentration. Several other physicochemical properties of the same electrolytes are studied to correlate to the concentration-dependent diffusion coefficients, including viscosity, conductivity, and microstructure analysis based on vibrational spectroscopy (infrared and Raman). Also included is the future application of the triangular column for in situ electrochemical measurements.
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- Award ID(s):
- 2243098
- PAR ID:
- 10490809
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- ISSN:
- 0013-4651
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1149/1945-7111/ad2954
