Nanosupercapacitors with fractal structures: searching designs to push the limit

Abstract

Microsupercapacitors (MSCs) are of increasing interest for powering microelectronic systems, while their applications are still limited by insufficient energy densities due to relatively large sizes. To address this critical challenge, herein nanosupercapacitors (NSCs) with fractal structures in 15 μm × 15 μm area are designed and fabricated by focused ion beam processing. Compared with typical interdigital electrode MSCs, the fractal geometry-designed NSCs (FNSCs) exhibit significantly enhanced performances, with the capacitance exceeding 15.1 mF cm⁻². It is proved by COMSOL Multiphysics simulations that the abundant sharp corners and narrow inter-electrode distances of the unique fractal designs produce stronger electric field intensity, tremendously increasing their charge storage abilities. Furthermore, a systematic mathematical model is built to evaluate the charge transfer difficulty, stability and performances of FNSCs with different structures and complexities. This study establishes a rational fractal design strategy to screen superior NSCs and push the limit of supercapacitors in future study.