Combined Computational and Experimental Study on the Influence of Surface Chemistry of Carbon-Based Electrodes on Electrode-Electrolyte Interactions in Supercapacitors

Supercapacitors are regarded as a promising technology for novel, powerful energy-storage systems. The mechanism of energy storage in these capacitors is not fully understood yet because of the complex molecular mechanisms at the atomistic scale. Exploring the processes at the nanoscale provides necessary fundamental and thorough insights for improving the performance of such devices. In this work, we present a combined computational and experimental study on electrode-electrolyte interactions in electric double-layer capacitors. The influence of pore size and surface chemistry of carbon-based electrode material on interactions with the electrolyte has been investigated for an organic and inorganic electrolyte using density functional theory calculations. In addition, solvent effects on the interaction strength have been systematically explored. We found that experimentally determined effects of pore confinement can be linked with calculated interaction energies, providing a suitable descriptor for virtual prescreening approaches. Our results show that the pore size significantly affects the interaction quality with the electrolyte. This effect and the influence of chemical functionalization have a stronger impact on the interaction with anions than with cations. Moreover, our studies indicate that solvent effects are especially important for surface functional groups that allow for hydrogen bonding. Overall, our results provide relevant information on how structural and electronic effects affect confinement, wettability, and mobility of electrolyte molecules, which is important for boosting and tuning the performance of supercapacitors.