Hydrous RuO2/carbon nanowalls hierarchical structures for all-solid-state ultrahigh-energy-density micro-supercapacitors

• Hydrous ruthenium oxide has been electrodeposited on carbon nanowalls.
• The electrode exhibits a specific capacitance in excess of 1000 mF cm−2.
• Based on this material, an all-solid-state micro-supercapacitor has been realized.
• Its specific energy is comparable to the state-of-the-art lithium ion micro-batteries.

Micro-supercapacitors have attracted considerable research attention for on-chip energy storage due to their unique properties and potential applications in various smart electronic devices. Although significant advances have been reported on their power performances, they still cannot compete with micro-batteries in terms of energy densities for mobile, portable and self-powered applications. Herein, we demonstrate the fabrication of vertically aligned carbon nanowalls (CNW) decorated with porous ruthenium oxide as a high-performance electrode for all-solid-state micro-supercapacitors. The decorated CNW electrode, essentially consisting of thin carbon sheets assembled from graphene domains, delivers specific capacitance in excess of 1000 mF cm−2 (which is three orders of magnitude higher than state-of-the-art micro-supercapacitors) and energy density comparable to that of lithium-ion micro-batteries, but with superior power and cycling stability. Our findings demonstrate a route towards the integration of microfabricated supercapacitors combining fast charge/discharge rates with high energy densities.

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