PNNL

Abstract

We report coronene, a polycyclic aromatic hydrocarbon, exhibits reversible oxidative anion insertion properties in a LiTFSI based water-in-salt electrolyte. The coronene electrode delivers a reversible capacity of 64.5 mAh g–1 with the first-cycle Coulombic efficiency of 73.1%. The results demonstrate that the high concentrations of LiTFSI lower the anion-insertion potential in coronene, which allows to reveal the capacity below the onset of oxygen evolution reaction. Furthermore, evidence points to the formation of cathode electrolyte interphase on the surface of coronene, which contributes to the reversible anion-storage in coronene as well. Ex situ XRD and SEM are carried out to reveal the structural evolution of the coronene electrode and storage mechanism of the TFSI– anions. FTIR studies reveal that upon anion insertion the interactions between the TFSI- ion and coronene molecules resemble that of covalent bonding.