Flexible, Thermally Stable, and Ultralightweight Polyimide-CNT Aerogel Composite Films for Energy Storage Applications

Omid Aghababaei Tafreshi; Zia Saadatnia; Shahriar Ghaffari-Mosanenzadeh; Ambrish Kumar; Meysam Salari; Sara Mohseni Taromsari; Mohammad Mahdi Rastegardoost; Chul B Park; Hani E Naguib

doi:10.1021/acsami.3c11539

Flexible, Thermally Stable, and Ultralightweight Polyimide-CNT Aerogel Composite Films for Energy Storage Applications

ACS Appl Mater Interfaces. 2023 Nov 1;15(43):50360-50377. doi: 10.1021/acsami.3c11539. Epub 2023 Oct 17.

Affiliations

¹ Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada.
² Department of Mechanical and Manufacturing Engineering, Ontario Tech University, Oshawa, Ontario, L1G 0C5, Canada.
³ Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada.
⁴ Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada.

PMID: 37847866
DOI: 10.1021/acsami.3c11539

Abstract

Polyimide (PI) aerogels are promising in various fields of application, ranging from thermal insulators to aerospace. However, they are typically in the form of a bulk monolith, which suffers from a lack of conformability and drapability. Moreover, their electrical conductivity is limited, and they mainly display an insulative behavior. These shortcomings can limit the applications of PI aerogels in energy storage systems, which require ultralightweight flexible conductive films, which at the same time offer high thermal stability, ultralow density, and high surface area. To overcome these obstacles, the present study reports the fabrication of PI-carbon nanotube (PI-CNT) aerogel composite films with varying CNT content prepared through a sol-gel preparation method, followed by a supercritical drying procedure. Compared to pristine PI aerogels, which displayed a large shrinkage and density of 18.3% and 0.12 g cm^-3, respectively, the incorporation of only 5 wt % CNTs resulted in a significant reduction of both shrinkage and density to only 11.5% and 0.10 g cm^-3, respectively. This suggests the importance of CNTs in improving the dimensional stability of aerogels and creating a robust network. Further characterizations showed that incorporation of 5 wt % CNTs also resulted in the highest pore volume (1.25 cm³ g^-1), highest surface area (324 m² g^-1), highest real permittivity (80), highest electrical conductivity (3 × 10^-1 S m^-1), and ultrahigh service temperature (575 °C). It was also shown that the aerogel films can withstand a large degree of bending, can be twisted, and can be fully rolled with no obvious cracks propagated in the structure. The combined outstanding properties of the developed aerogel composite films make them promising potential candidates for supercapacitor electrodes. Therefore, the electrochemical performance of the devices based on aerogel electrodes was further studied. The device demonstrated a high energy density of 2.6 Wh kg^-1 at a power density of 303.8 W kg^-1. The total capacitance after 5000 cycles was 91.8% of the initial capacitance, which indicated excellent stability and durability of the device. Overall, this work provides a facile yet effective methodology for the development of high-performance aerogel materials for energy storage applications.

Keywords: aerogel composites; carbon nanotubes; electrical conductivity; supercapacitor; surface area.