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UT Chem/Biochem Dept


 

The 2014-2015 Beckman Scholars: Logan Daniel Bishop

Logan

Beckman research project in the Stevenson Group:

Probing Solvent-Ion Interactions using Experiment and Theory

The central principle behind rechargeable batteries is the ability to use a mobile charge carrier (ions) dissolved in a solvent. Reversibility of the charge storage process is made possible through solvation of the charge carrier, traditionally an alkaline cation, which can migrate between the two electrodes to balance the expenditure of charge. Solvation of ions is not well understood mechanistically and has several varying factors that can influence charge storage behavior.

Solvation properties of ion/solvent pairs can be analyzed quantitatively using vibrational spectroscopy including Raman spectroscopy, which measures the vibrations of chemical bonds by monitoring the wavelength of scattered light. Because the vibrational modes of these chemical bounds are affected by the ionic nature of their surroundings, the spectral readings of a solution relay information about the inter-molecular interactions of solute and solvent species. This is most aptly represented by the shifting of the spectral peaks, which occurs as the energy of the vibrational mode is altered. In this manner, the inter-molecular reactions occurring in the electrolyte solution can be observed by examining the vibrations of intra-molecular bonds.

Due to the prominence of lithium ion in the field of rechargeable cells, this study will center on identifying the solvation mechanism of several common lithium ion salts (LiPF6, LiClO4, LiBF4) in a series of organic carbonate electrolytes (Ethylene Carbonate, Polycarbonate, etc.) with variably sized non-polar chains. These experiments and correlated theoretical investigations will probe the nature of the solvating mechanism under a variety of different steric hindrances. Further study of these pairings across a range of concentrations can offer insight to the nature of the molecules that form a solvation shell about the central cation as the solution approaches infinite dilution.

Identifying a sensible mechanism for solvation can offer insight into selection of other promising electrolytes for new electrochemical cells and support further studies into lithium retention during battery cycling.


 

Created and maintained by Ruth Shear. Comments to author at DrRuth@mail.utexas.edu
Created Wed Jun 6th 2007. Last modified Mon, Mar 16, 2015.