Substrate Engineered Interconnected Graphene Electrodes with Ultrahigh Energy and Power Densities for Energy Storage Applications.

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, the energy densities of current supercapacitors are still significantly lower than the energy densities of lead acid (20-35 W h kg), Ni-metal hydride (40-100 W h kg), and Li-ion (120-170 W h kg) batteries. Recently, graphene-based supercapacitors have shown an energy density of 40-80 W h kg. 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 and a power density of 416.6 W cm. 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.