Femtosecond Laser Bessel Beam Fabrication of a Supercapacitor with a Nanoscale Electrode Gap for High Specific Volumetric Capacitance.

Supercapacitors are widely used in electronic systems as energy storage devices. The fabrication of a miniaturized supercapacitor with high specific capacitance has attracted much attention in recent years. Here, we propose a new method to fabricate supercapacitors with a nanoscale electrode gap by using a femtosecond laser. The original femtosecond laser was converted to a nondiffraction Bessel light field with nanoscale beam width and microscale focal depth. Nanoscale processing precision was achieved by regulating the Bessel beam. We fabricated graphene supercapacitors with different electrode gap widths (varying from the microscale to the nanoscale) using this method. Supercapacitors fabricated by this method have advantages in both size miniaturization (electrode gap width down to ∼500 nm) and electrochemical performance improvement (a specific volumetric capacitance of 195 F/cm 3 ). This work demonstrates that the femtosecond laser Bessel beam processing method provides a reliable pathway to fabricate miniaturized supercapacitors with high specific capacitance and other nanoscale electronic devices.