"Correlating Li-Ion Solvation Structures and Electrode Potential Temperature Coefficients"

Hansen Wang: Sang Cheol Kim, Tomás Rojas, Yangying Zhu, Yanbin Li, Lin Ma, Kang Xu, Anh T. Ngo, Yi Cui; Journal of the American Chemical Society, 01/28/21.

Additional Authors: Sang Cheol Kim, Tomás Rojas, Yangying Zhu, Yanbin Li, Lin Ma, Kang Xu, Anh T. Ngo, Yi Cui

Abstract:

Temperature coefficients (TCs) for either electrochemical cell voltages or potentials of individual electrodes have been widely utilized to study the thermal safety and cathode/anode phase changes of lithium (Li)-ion batteries. However, the fundamental significance of single electrode potential TCs is little known. In this work, we discover that the Li-ion desolvation process during Li deposition/intercalation is accompanied by considerable entropy change, which significantly contributes to the measured Li/Li+ electrode potential TCs. To explore this phenomenon, we compare the Li/Li+ electrode potential TCs in a series of electrolyte formulations, where the interaction between Li-ion and solvent molecules occurs at varying strength as a function of both solvent and anion species as well as salt concentrations. As a result, we establish correlations between electrode potential TCs and Li-ion solvation structures and further verify them by ab initio molecular dynamics simulations. We show that measurements of Li/Li+ electrode potential TCs provide valuable knowledge regarding the Li-ion solvation environments and could serve as a screening tool when designing future electrolytes for Li-ion/Li metal batteries.