# Flexible Graphene/Carbon Nanotube Electrochemical Double-Layer Capacitors with Ultrahigh Areal Performance

**Authors:** Valentino Romano, Beatriz Martin-Garcia, Sebastiano Bellani, Luigi Marasco, Jaya Kumar Panda, Reinier Oropesa-Nunez, Leyla Najafi, Antonio Esau Del Rio Castillo, Mirko Prato, Elisa Mantero, Vittorio Pellegrini, Giovanna D Angelo, Francesco Bonaccorso  
**arXiv:** [2005.13024](https://arxiv.org/abs/2005.13024)  
**Date:** 2020-04-11  
**Summary page:** https://www.summarizepaper.com/en/paper/2005.13024v1/

## Key points

- Fabrication of Electrochemical Double-Layer Capacitors (EDLCs) with high areal capacitance is crucial for advanced energy storage devices.
- A high-throughput manufacturing process for graphene/nanotubes hybrid EDLCs is presented in this study.
- Wet-jet milling (WJM) method is utilized to exfoliate graphite into single/few-layer graphene flakes (WJM-G) in industrial volume, with a production rate of approximately 0.5 kg/day.
- Commercial single/double-walled carbon nanotubes (SDWCNTs) are mixed with graphene flakes to act as spacers during film formation.
- The resulting self-standing, metal- and binder-free flexible EDLC electrodes exhibit high active material mass loadings up to 30 mg cm–2.
- The symmetric WJM–G/SDWCNTs EDLCs demonstrate outstanding performance, exhibiting electrode energy densities of 539 µWh cm–2 at 1.3 mW cm–2 and operating power densities up to 532 mW cm–2, outperforming most other EDLC technologies.
- The EDCLs show excellent cycling stability and remarkable flexibility even under highly folded states (up to 180 degrees).
- This novel approach combines industrial-like production of active materials with simplified manufacturing of EDLC electrodes, resulting in ultrahigh areal performance of the as-produced EDLCs that hold great promise for advanced energy storage designs.
- The use of WJM–G and SDWCNTs as spacers provides a simple yet effective way to achieve high mass loadings while maintaining good electrical conductivity and mechanical properties.
- This research opens up new avenues for developing flexible and efficient energy storage devices that can be integrated into various applications such as wearable electronics or electric vehicles.

## Summary

The fabrication of Electrochemical Double-Layer Capacitors (EDLCs) with high areal capacitance is crucial for the development of advanced energy storage devices. In this study, a high-throughput manufacturing process for graphene/nanotubes hybrid EDLCs is presented. The wet-jet milling (WJM) method is utilized to exfoliate graphite into single/few-layer graphene flakes (WJM-G) in industrial volume, with a production rate of approximately 0.5 kg/day. Commercial single/double-walled carbon nanotubes (SDWCNTs) are mixed with graphene flakes to act as spacers during film formation. The resulting self-standing, metal- and binder-free flexible EDLC electrodes exhibit high active material mass loadings up to 30 mg cm–2. The symmetric WJM–G/SDWCNTs EDLCs demonstrate outstanding performance, exhibiting electrode energy densities of 539 µWh cm–2 at 1.3 mW cm–2 and operating power densities up to 532 mW cm–2, outperforming most other EDLC technologies. Additionally, the EDCLs show excellent cycling stability and remarkable flexibility even under highly folded states (up to 180 degrees). This novel approach combines industrial-like production of active materials with simplified manufacturing of EDLC electrodes, resulting in ultrahigh areal performance of the as-produced EDLCs that hold great promise for advanced energy storage designs. The use of WJM–G and SDWCNTs as spacers provides a simple yet effective way to achieve high mass loadings while maintaining good electrical conductivity and mechanical properties. This research opens up new avenues for developing flexible and efficient energy storage devices that can be integrated into various applications such as wearable electronics or electric vehicles.