High energy flexible supercapacitors formed via bottom-up infilling of gel electrolytes into thick porous electrodes

Xiangming Li,Paul V Braun,Chaochao Yao,Qiye Zheng,Jinyou Shao,Pengcheng Sun,Junjie Wang,Runyu Zhang,Sung-Kon Kim,Yu-Run Miao

doi:10.1038/s41467-018-04937-8

Abstract

Formation of thick, high energy density, flexible solid supercapacitors is challenging because of difficulties infilling gel electrolytes into porous electrodes. Incomplete infilling results in a low capacitance and poor mechanical properties. Here we report a bottom-up infilling method to overcome these challenges. Electrodes up to 500 μm thick, formed from multi-walled carbon nanotubes and a composite of poly(3,4-ethylenedioxythiophene), polystyrene sulfonate and multi-walled carbon nanotubes are successfully infilled with a polyvinyl alcohol/phosphoric acid gel electrolyte. The exceptional mechanical properties of the multi-walled carbon nanotube-based electrode enable it to be rolled into a radius of curvature as small as 0.5 mm without cracking and retain 95% of its initial capacitance after 5000 bending cycles. The areal capacitance of our 500 μm thick poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, multi-walled carbon nanotube-based flexible solid supercapacitor is 2662 mF cm–2 at 2 mV s–1, at least five times greater than current flexible supercapacitors.

Highlights

Formation of thick, high energy density, flexible solid supercapacitors is challenging because of difficulties infilling gel electrolytes into porous electrodes
We find the volumetric capacitance of even the thick (>100 μm) bottom-up infilled Flexible solid supercapacitors (FSSCs) is comparable to the value of other previously reported, much thinner, sandwich type multi-walled carbon nanotubes (MWCNT)-based thin-film FSSCs43–45
A bottom-up infilling method is demonstrated to be highly effective for infilling of solid gel electrolytes into porous electrodes

Summary

Introduction

High energy density, flexible solid supercapacitors is challenging because of difficulties infilling gel electrolytes into porous electrodes. Examples of FSSC containing both micropores and larger macropores include one formed using 120 μm thick 3D graphene hydrogel electrodes which exhibited an areal capacitance of 372 mF cm–2 24, one formed with 81.6 μm thick reduced graphene oxide/polypyrrole nanotube paper electrodes which exhibited an areal capacitance of 512 mF cm–2 25, and one formed using graphene/carbon nanofiber aerogel electrodes which showed an areal capacitance of 158 mF cm–2 26 In these systems, the macropores both serve as an electrolyte reservoir and improve the infilling of the porous electrodes[24,25,26,27,28]. Prior to the work here, it has not been possible to infill such a structure with solid electrolyte

Methods

Results

Conclusion