Interfacial thermal signature of electrode/electrolyte interfaces and its effect on charge storage performance during charging of electrochemical energy storage devices

Abstract

This study investigates the interfacial thermal signature at the electrode/electrolyte interface and its effect on charge storage capabilities of electrochemical energy storage devices. In order to do so, commonly used binary solvent of EC/DMC is chosen as an example to interpret the fundamental interplay between different solvents. Molecular dynamics simulation are presented to analyse the interfacial dynamics during charging. The results show that the interfacial thermal resistance for hot electrode is generally higher than that for cold electrode. This was due to the poor contact between electrolyte molecules and hot electrode caused by local disorder for high temperature. In addition, the interfacial thermal resistance gradually decreases with increasing surface charge density, which is slightly asymmetric for different heat flow directions from positive or negative electrodes. The continuous decrease near negative electrode is due to the continuously increasing electrostatic interaction energy of solvent molecules with negative electrode. On the other hand, the oscillatory decrease near positive electrode is due to the trade-off between increasing electrostatic interaction energy with positive electrode and switching between different solvent species. Furthermore, diverse heat flow pathways could be present at the interface with solvent playing a crucial role. Solvent molecules preferred a tilted or vertical orientation at high surface charge density, leading to better heat flow at the electrode/electrolyte interface. Finally, two distinct regimes of differential capacitance were observed, i.e., temperature dominant regime at low surface charge density and charge dominant regime at high surface charge density. In the meantime, the total differential capacitance is better when temperature gradient aligns with electric field, especially for low surface charge density. This can be attributed to solvation-mediated dynamics of solvated ions. This investigation could help in better designing electrode/electrolyte interface systems with better heat transfer/dissipative ability and performance.