Room-temperature fast assembly of 3D macroscopically porous graphene frameworks for binder-free compact supercapacitors with high gravimetric and volumetric capacitances

Abstract

Synthesis and applications of three-dimensional (3D) porous graphene frameworks (GFs) have attracted extensive interest owing to their intriguing advantages of high specific surface area, enriched porosity, excellent electrical conductivity, exceptional compressibility and processability. However, it is still challenging for economically viable, fast and scalable assembly of 3D GFs at room-temperature. Herein, we reported a one-step scalable strategy for fast self-assembly of graphene oxide into 3D macroscopically porous GFs, with assistance of polyoxometalates (POM) as functional cross-linker and hydrazine hydrate as reductant at room-temperature. The resulting 3D interconnected macroporous POM-GFs uniformly decorated with ultrasmall POM nanoclusters were directly processed into binder-/additive-free film compact electrodes (1.68 g cm−3) with highly aligned, layer-stacked structure and electrically conductivity (622 S m−1) for high-performance supercapacitors, showing an impressive gravimetric capacitance of 205 F g−1, volumetric capacitance of 334 F cm−3 at 1 mV s−1, and remarkable cycling stability with capacitance retention of 83% after 10,000 cycles, outperforming the most reported GFs. Further, the solid-state supercapacitors offered excellent gravimetric capacitance of 157 F g−1, exceptionally volumetric capacitance of 115 F cm−3 at 2 mV s−1 based on single electrode, and volumetric energy density of 2.6 mWh cm−3. Therefore, this work will open novel opportunities to room-temperature fast assembly of 3D porous graphene architectures for high-energy–density supercapacitors.