Supercapacitor Electrodes from Viscose-Based Activated Carbon Fibers: Significant Yield and Performance Improvement Using Diammonium Hydrogen Phosphate as Impregnating Agent

Stefan Breitenbach,Mathias Andreas Hobisch,Stefan Spirk,Christian Fürst,Christoph Unterweger,David Stifter,Achim Walter Hassel,Alexander Lumetzberger

doi:10.3390/c6020017

Abstract

Viscose fibers were impregnated with different concentrations of diammonium hydrogen phosphate (DAHP), carbonized, activated, and tested as high-performance electrode materials for supercapacitors. The yield of these activated carbon fibers (ACFs) could be increased by a factor of 14 by using DAHP compared to ACF without impregnation. These specific activation procedures yielded a high specific surface area of more than 2700 m2·g−1 with a pore size distribution (PSD) suitable for use as a supercapacitor electrode. The electrode materials were implemented in symmetric supercapacitors using TEMA BF4 as electrolyte and cyclic voltammetry measurements showed high specific capacitances of up to 167 F·g−1. Furthermore, the devices showed high energy densities of up to 21.4 W·h·kg−1 and high-power densities of up to 8.7 kW·kg−1. The supercapacitors featured high capacity retention (96%) after 10,000 cycles. These results show that ACFs made of viscose fibers, previously impregnated with DAHP, can be used as high-performance electrodes in supercapacitors for energy storage applications.

Highlights

Global energy consumption has been accelerating at an alarming rate due to the rapid development of the global economy and the growing human population worldwide [1,2,3,4,5,6,7,8,9]
For the production of such supercapacitors, carbon materials are used as electrodes, since they are chemically and thermally stable and easy to process
Activated carbons are very popular in this research area since they are characterized by a high specific surface area (1000–3000 m2 ·g−1 ) and a high pore volume (0.5–2 cm3 ·g−1 ) at a comparatively low cost (4.15 US$·kg−1 ) [1,2,3,4,5,6,7,8,9,12]

Summary

Introduction

Global energy consumption has been accelerating at an alarming rate due to the rapid development of the global economy and the growing human population worldwide [1,2,3,4,5,6,7,8,9]. For the production of such supercapacitors, carbon materials are used as electrodes, since they are chemically and thermally stable and easy to process. Their structural properties can be modified and optimized relatively . ACFs are an exciting alternative to classic granular and powdered activated carbons These are known for their low electrical resistance along the fiber axis and good contact with the current collector [13]. The effect of DAHP on the yield of cellulosic materials during carbonization is well described in the literature, its influence on the development of the pore structure during carbonization, and especially activation, is not systematically studied [14,17,18]. We use viscose fibers as a precursor for ACFs

Methods

Results

Conclusion