Graphene hydrogels functionalized non-covalently by fused heteroaromatic molecule for asymmetric supercapacitor with ultra-long cycle life.

A redox-active organic molecular electrode is prepared for supercapacitors. Benzo[1,2-b:4,5-b']dithiophene-4,8-dione (BDTD), planar molecule with fused heteroaromatic structure, has been adsorbed on conductive reduced graphene oxide (rGO) by π–π interactions to form a 3D interconnected and functionalized xerogel (BDTD-rGO). Because the five-membered aromatic heterocycle is more electron-rich than the six-membered aromatic ring, which enlarges the electronic interaction between the BDTD molecule and the conjugated graphene network and accordingly reduce the solubility of BDTD molecule in electrolyte. As a result, the optimized BDTD-rGO electrodes achieve specific capacitance of 360 F g−1 at 1 A g−1, with ultra-long cycle life of 96.4% after 10,000 cycles, and even 80% after 50,000 cycles at 5 A g−1 in 1 M H 2 SO 4. Furthermore, the asymmetric supercapacitor (ASC), which is assembled by using the BDTD-rGO as the negative electrode and lamellar holey graphene hydrogel (LGH) as the positive electrode respectively, exhibits better energy storage performance. Image 1 • Reduced graphene oxide was non-covalently functionalized by organic molecules. • The BDTD-rGO exhibits an ultra-long cycle life (96.4% for 10,000 cycle). • The BDTD-rGO possesses an excellent specific capacitance of 360 F g−1 at 1 A g−1. • Negative and positive electrodes can generate potential self-matching behavior. • As-fabricated the asymmetric supercapacitor delivers a superior cyclic stability. [ABSTRACT FROM AUTHOR]