Focused ion beam-fabricated high-performance electrodeposited nickel-ruthenium-ruthenium oxide nano-supercapacitor

Abstract

Supercapacitor miniaturization is highly sought due to the considerable demand for portable, flexible, and wearable microscale electronics. Constructing supercapacitor devices in micro- and nano-scale dimensions, however, imposes significant conceptual and technical challenges. We report an in-plane nickel-ruthenium/ruthenium-oxide (NiRu/RuO2) nano-supercapacitor fabricated by focused ion beam (FIB). The FIB-patterned nano-supercapacitor consists of interdigitated microscale electrodes separated by extremely small, 100 nm, spacings and a thin (200 nm) electrodeposited NiRi/RuO2 layer. An aqueous device exhibited high areal capacitance (10.5 mF cm-2) at high scan rates, low equivalent series resistance (0.047 Ω cm2), good capacitance retention, and power-density of 625 mW cm-2 with an energy density of 0.8 µWh cm-2. A NiRu/RuO2 nano-supercapacitor comprising non-aqueous gel electrolyte was also prepared, demonstrating practical applicability of the technology. Notably, the FIB-fabricated NiRu/RuO2 nano-supercapacitor featured high frequency response and alternating current (AC)-line filtering capabilities, making the device the smallest supercapacitor AC line-filter reported. The new FIB-fabricated NiRu/RuO2 nano-supercapacitor design may open new avenues in nano- and micro-scale energy storage, power conditioning, and AC line filtering.