Improved-quality graphene films via the synergism of large nanosheet aligning and nanotube bridging for flexible supercapacitors.

Scalable production of reduced graphene oxide (rGO) films with high mechanical-electrical properties are desirable candidates for wearable electronics devices and energy storage applications. Removing structural incompleteness such as wrinkles or voids in the graphene films generated from the assemble process would greatly optimize their mechanical properties. However, the densely stacked graphene sheets in the films degrades their ionic kinetics and thus limits their development. Here, a horizontal-longitudinal-structure modulating strategy is demonstrated to produce enhanced mechanical, conductive and capacitive graphene films. Typically, two-dimensional (2D) large graphene sheets (LGS) induce regular stacking of GO during assembling process to reduce wrinkles, while one-dimensional (1D) single-walled carbon nanotubes (SWCNT) bridge with graphene sheets to strengthen the multidirectional intercalation and reduce GO layer restacking. The simultaneous incorporation of LGS and SWCNT synergistically makes fine microstructure with improving the alignment of graphene sheets, increasing continuous conductive pathways to facilitate electron transport, and enlarging interlayer spacing to promote the electrolyte ion diffusion. As a result, the obtained graphene films are flat and exhibit signally reinforced mechanical properties, electrical conductivity (38727 S m-1), as well as specific capacitance (232 F g-1) as supercapacitor electrodes than those of original rGO films. Moreover, owing to the comprehensive improved properties, the flexible gel supercapacitor assembled by the graphene film-based electrodes shows high energy density, good flexibility and excellent cycling stability (93.8% capacitance retention after 10000 cycles). This work provides a general strategy to manufacture robust graphene structural materials for energy storage applications in flexible and wearable electronics.