Ionic Peltier Effect in Concentrated Carbonate and Ether-Based Li-Ion Electrolytes

Understanding the Li+ transport and solvation behaviors in electrolytes is crucial for electrolyte selection to optimize cell performance. The ionic Peltier effect is the phenomenon of heat generation or absorption at the interface of electrodes during a reversible electrode reaction. It can provide us with information on the solvation thermodynamics of Li-ion electrolytes. By using the temperature difference metrology developed by our group, we expand our ionic Peltier coefficient measurements and study more ether-based and carbonate-based electrolytes. The magnitude of Peltier coefficients of ether-based electrolytes is -70-80 kJ/mol, almost 2 times larger than that of carbonated-based electrolytes, around -20-30 kJ/mol. This difference indicates a larger change in partial molar entropy between the Li electrode and electrolyte at the interface in ether-based electrolytes. In addition, we also observe a decrease in the magnitude of the Peltier coefficient in ether-based electrolytes with increasing concentration, the same as in carbonate electrolytes. For carbonate electrolytes, the binary mixture (EC/DMC) electrolyte has a Peltier coefficient between the values of pure solvents, EC and DMC. Peltier coefficients of different Li salt concentrations, from 0.5M to 3M, are slightly temperature dependent by being more negative with increasing temperature. Combining with the present Li solvation thermodynamic properties and the structures of different electrolytes, we provide information on the interaction between Li ion-solvent, and its correlation with solvent physical properties.