Substituent effect on the cell voltage of nanographene based Li-ion batteries: A DFT study

Abstract Using density functional theory calculations, we studied the electronic and energetic properties of –F, –NH2, and –NO2 functionalized Hexa-peri-hexabenzocoronene (HBC, C42H18) nanographene and their potential application in Li-ion batteries (LIBs). We found that Li/Li+ preferably adsorbs above the center of peripheral six-membered rings of HBC with adsorption energy about −53.7 kcal/mol. After the Li+ adsorption, the work function of HBC is increased by about 84.5%, while the atomic Li decreases it by about 36.0%. After functionalization, –NO2 increases the HBC work function from 3.45 to 4.00 eV, and the –NH2 decreases it to 3.28 eV. Also, –NO2 strongly and –NH2 weakly reduces the HOMO-LUMO gap of HBC. Our calculated cell voltage for LIB when an HBC nanographene is used as the anode is about 1.70 V. Based on the results, –NH2 group increases the cell voltage by about 0.25 V and reversely, –NO2 group decreases it from 1.70 to 1.16 eV. This indicates that the NH2-HBC is much more appropriate material for application in the anode of LIBs compared to the F-HBC, NO2-HBC, and pristine HBC.