The impact of vertical π-extension on redox mechanisms of aromatic diimide dyes

Aromatic diimide dyes are an attractive class of redox-active organic molecules for lithium-ion batteries, whose battery performances (stabilities. conductivities and cyclicities) are strongly dependent on the sizes of their pi-systems. However, due to the different Clar's structures possessed, three vertically pi-extended aromatic diimides, namely, naphthalene diimide (two one-electron reductions), perylene diimide and terrylene diimide (two one-electron reductions), exhibit different electronic redox mechanisms when served as cathode materials in organic lithium-ion batteries. Herein, we have studied carefully the different electrochemical characteristics of the three aromatic diimides through experimental and theoretical calculations. Their battery present different shape of charge/discharge curves resulting from stability of their reduction state during charge/discharge process. Terrylene diimide shows better cycle and rate capacities than those of naphthalene diimide and perylene diimide, which could be attributed to the more energies released during terrylene diimide combining with lithium ions than those of other two diimides. (C) 2019 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.