Supercapacitors combine the advantages of electrochemical storage technologies such as high energy density batteries and high power density capacitors. At 5-10 W h kg-1, the energy densities of current supercapacitors are still significantly lower than the energy densities of lead acid (20-35 W h kg-1), Ni-metal hydride (40-100 W h kg-1), and Li-ion (120-170 W h kg-1) batteries. Recently, graphene-based supercapacitors have shown an energy density of 40-80 W h kg-1. However, their performance is mainly limited because of the reversible agglomeration and restacking of individual graphene layers caused by π-π interactions. The restacking of graphene layers leads to significant decrease of ion-accessible surface area and the low capacitance of graphene-based supercapacitors. Here, we introduce a microstructure substrate-based method to produce a fully delaminated and stable interconnected graphene structure using flash reduction of graphene oxide in a few seconds. With this structure, we achieve the highest amount of volumetric capacitance obtained so far by any type of a pure carbon-based material. The affordable and scalable production method is capable of producing electrodes with an energy density of 0.37 W h cm-3 and a power density of 416.6 W cm-3. This electrode maintained more than 91% of its initial capacitance after 5000 cycles. Moreover, combining with ionic liquid, this solvent-free graphene electrode material is highly promising for on-chip electronics, micro-supercapacitors, as well as high-power applications.
Keywords: GO flash reduction; energy storage; interconnected graphene network; substrate patterning; supercapacitor.