Bottom-up scalable temporally-shaped femtosecond laser deposition of hierarchical porous carbon for ultrahigh-rate micro-supercapacitor

With the accelerated development of electronic devices, micro-supercapacitors (MSCs), as energy storage devices that can charge and discharge quickly, have attracted considerable attention. To improve the rate capability of MSCs with consideration of the energy density remains a challenge. We demonstrated a facile method for the preparation of thin films through bottom-up femtosecond pulsed laser deposition. The femtosecond laser irradiated the polyimide film through a transparent substrate to uniformly sputter the electrode material onto the lower surface of the substrate. We successfully deposited porous amorphous carbon, graphene, and carbon quantum dots with controllable properties by temporally shaping the femtosecond laser. The resulting MSC exhibited an ultrahigh frequency response and good performance at scan rates up to 10,000 V s⁻¹. The characteristic frequency f₀ of the MSC was as high as 42,000 Hz, and the relaxation time constant τ₀ was 0.0238 ms. The MSC reached an impedance phase angle of −82.6° at a frequency of 120 Hz, an ultrahigh power density of more than 30 kW cm⁻³, and an energy density of 0.068 W h cm⁻³. This method provides a novel perspective for the preparation of ultrahigh frequency filters for future miniaturized portable electronic devices.[Figure not available: see fulltext.]