Graphene Carbon Nanotube Carpets Grown Using Binary Catalysts for High-Performance Lithium-Ion Capacitors.

Salvatierra, Rodrigo Villegas; Zakhidov, Dante; Sha, Junwei; Kim, Nam Dong; Lee, Seoung-Ki; Raji, Abdul-Rahman O; Zhao, Naiqin; Tour, James M · ACS Nano · 2017

basic_science · Level V

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Abstract

Here we show that a versatile binary catalyst solution of Fe<sub>3</sub>O<sub>4</sub>/AlO<sub>x</sub> nanoparticles enables homogeneous growth of single to few-walled carbon nanotube (CNT) carpets from three-dimensional carbon-based substrates, moving past existing two-dimensional limited growth methods. The binary catalyst is composed of amorphous AlO<sub>x</sub> nanoclusters over Fe<sub>3</sub>O<sub>4</sub> crystalline nanoparticles, facilitating the creation of seamless junctions between the CNTs and the underlying carbon platform. The resulting graphene-CNT (GCNT) structure is a high-density CNT carpet ohmically connected to the carbon substrate, an important feature for advanced carbon electronics. As a demonstration of the utility of this approach, we use GCNTs as anodes and cathodes in binder-free lithium-ion capacitors, producing stable devices with high-energy densities (∼120 Wh kg<sup>-1</sup>), high-power density capabilities (∼20,500 W kg<sup>-1</sup> at 29 Wh kg<sup>-1</sup>), and a large operating voltage window (4.3 to 0.01 V).